# Radiation-induced gastrointestinal and cutaneous injuries: understanding models, pathologies, assessments, and clinically accepted practices

Radia Tamarat, Merriline M Satyamitra, Marc Benderitter, Andrea L Dicarlo

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## To cite this version:

Radia Tamarat, Merriline M Satyamitra, Marc Benderitter, Andrea L Dicarlo. Radiation-induced gastrointestinal and cutaneous injuries: understanding models, pathologies, assessments, and clinically accepted practices. International Journal of Radiation Biology, 2024, 100 (7), pp.969 - 981. 10.1080/09553002.2024.2356544. irsn-04891780

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# Radiation-induced gastrointestinal and cutaneous injuries: understanding models, pathologies, assessments, and clinically accepted practices

Radia Tamarat, Merriline M. Satyamitra, Marc Benderitter & Andrea L. DiCarlo

**To cite this article:** Radia Tamarat, Merriline M. Satyamitra, Marc Benderitter & Andrea L. DiCarlo (2024) Radiation-induced gastrointestinal and cutaneous injuries: understanding models, pathologies, assessments, and clinically accepted practices, *International Journal of Radiation Biology*, 100:7, 969-981, DOI: 10.1080/09553002.2024.2356544

**To link to this article:** https://doi.org/10.1080/09553002.2024.2356544

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Published online: 24 May 2024.

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# Radiation-induced gastrointestinal and cutaneous injuries: understanding models, pathologies, assessments, and clinically accepted practices

Radia Tamaratª, Merriline M. Satyamitraᵇ ID, Marc Benderitterª and Andrea L. DiCarloᵇ ID

ªInstitut de Radioprotection et de Sûreté Nucléaire (IRSN), Fontenay-aux-Roses, France; ᵇRadiation and Nuclear Countermeasures Program (RNCP), Division of Allergy, Immunology, and Transplantation (DAIT), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Rockville, MD, USA

## ABSTRACT

**Purpose:** A U. S. and European joint effort fostering the development of medical countermeasures (MCMs) operable in case of radiological or nuclear emergencies.

**Methods:** Based on the joint engagement between the U.S. National Institute of Allergy and Infectious Diseases (NIAID) and the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN), a Statement of Intent to Collaborate was signed in 2014 and a series of working group meeting were established. In December 2022, the NIAID and IRSN hosted a five-day, U.S./European meeting titled 'Radiation-Induced Cutaneous and Gastrointestinal Injuries: Advances in Understanding Pathologies, Assessment, and Clinically Accepted Practices' in Paris, France. The goals of the meeting were to bring together U.S. and European investigators to explore new research avenues for the medical management of skin and gastrointestinal injuries, including specific diagnostics for each organ system, animal models, and promising medical countermeasures (MCMs) to mitigate radiation damage. There was also an emphasis on exploring additional areas of medicine and response to understand best practices from other emergency scenarios, which could be leveraged to improve radiation preparedness, and the importance of accurate dosimetry in preclinical work.

**Results:** Subsequent to the workshop, seven collaborative projects, funded by both organizations, were established on topics ranging from MCMs and predictive biomarkers, and using physical methods to assess cutaneous radiation injuries, to mechanistic studies to understand radiation-induced damage in multiple organ systems. The importance of accurate dosimetry in preclinical works was highlighted and two recently published U.S./European commentaries that focus on the need for dosimetry standardization in the reported literature had their origins in this meeting. This commentary summarizes the workshop and open discussions among academic investigators, industry researchers, and U.S. and IRSN program representatives.

**Conclusions:** Given the substantive progress made due to these interactions, both groups plan to expand out these meetings by incorporating high-level investigators from across the globe, while endeavoring to maintain the informal setting that was conducive to in-depth scientific discussion and enhanced the state of the science in radiation research.

## ARTICLE HISTORY

Received 30 January 2024
Revised 2 April 2024
Accepted 29 April 2024

## KEYWORDS

Biodosimetry; medical;
emergency; skin; diagnosis;
intestines

## Introduction

An exceptional health situation is defined as the occurrence of an emerging, unusual, and often complex scenario that goes beyond the scope of routine health management, in terms of number of victims, seriousness (population impact), or media coverage, and can often lead to a crisis. Examples of exceptional health situations can include industrial disasters, pandemics, and radiological and nuclear emergencies resulting from an accident or malicious act. Such situations are characterized by high strain on healthcare systems and potential disruptions in the supply of medical products. Governmental and international organizations implement response plans to manage these exceptional health situations.

The medical response to a radiological or nuclear emergency differs depending on the characteristics of the emergency. Several scenarios have been described, including (1) nuclear accidents that may occur at a power plant, at a fuel cycle facility, or during a transport of radioactive materials; (2) radiological mishaps in industrial or research facilities operating radiological devices (e.g. mishandling of orphan source used for radiography or sterilization); (3) accidents arising in medical facilities (error in the use of radiotherapy or brachytherapy equipment); or (4) malicious attacks via a radiological dispersal device, radiological exposure device, or improvised nuclear device. Further, a deliberate attack may occur on a nuclear facility with a risk of discharge of significant amounts of radioactive material into the environment. In the case of a major
accident or terrorist attack, a very large number of victims would require emergency hospital admission and treatment. Irradiated or contaminated (internally or externally) individuals could also suffer additional trauma (e.g., wounds or thermal burns), which would complicate treatment strategies. Victims exposed to a large part of the body volume with a dose >1 Gy may develop an acute radiation syndrome (ARS) in its hematological (H), gastrointestinal (GI) or cutaneous presentation, and possibly experience further chronic debilitating multi-organ injuries years after exposure (delayed effects of acute radiation exposure - DEARE) or radiation-induced cancer. Victims exposed to a smaller body volume with higher doses (>20Gy) may develop cutaneous (CRI) or localized radiation injuries (LRI), with superficial and extensive necrotic lesions possible in the acute phase, and further radiation-induced fibrosis or radiation-induced cancer months to years after exposure.

At the international level, coordination of joint efforts to establish a strategic research agenda strengthening the medical response to a radiological or nuclear emergency will be crucial for the future. For this reason, the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and the National Institute of Allergy and Infectious Diseases (NIAID), part of the U. S. National Institutes of Health (NIH) have endeavored to strengthen their cooperation over the past 15 years. The IRSN, supervised among others by the French Ministries of Health, Research and Defense, has responsibility for considering and addressing a wide range of radiation and nuclear emergencies. NIAID, through the Radiation and Nuclear Countermeasures Program (RNCP), provides funding and oversight for researchers developing diagnostics and therapeutics for civilian use in case of a radiological or nuclear incident. Beginning in 2014, a Statement of Intent was signed by the IRSN and NIAID outlining activities that would be supported by the collaboration. Among other undertakings, these research areas included development of mitigators of radiation injuries, coordination of basic, pre-clinical and clinical research efforts, exchange of biological samples, comparative studies between researchers in both countries, coordination of scientific workshops and training, and joint publishing of scientific findings.

A first meeting hosted in Paris, France, in July 2015 on 'Cellular Therapies as Mitigators for Treatment of Radiation Injuries' (DiCarlo et al. 2017) focused on understanding the potential use of cells as mitigators of radiation injuries in a number of different organ systems, and their ability to save lives during a radiological or nuclear public health emergency. A second meeting, hosted once more in Paris, France in December of 2022 (the focus of this commentary), brought together U. S. researchers supported by NIAID and investigators from France and other European institutions (Table 1). Objectives of these interactions were to:

* Design, implement, and maintain an action plan for research, innovation, and development of diagnostics, mitigators, and treatments (medical countermeasures, or MCMs) to address injuries resulting from exposure to radiological or nuclear threats;

* Pursue innovative strategies to foster translation from research and development activities to MCM availability for clinical use;

<table><caption>Table 1. IRSN/NIAID Invited meeting presenters.</caption><thead><tr><td>Name</td><td>Affiliation</td></tr></thead><tbody><tr><td>Oscar Acosta, PhD</td><td>University of Rennes 1, Rennes France</td></tr><tr><td>Melissa Adomako, MPH</td><td>NIAID, Rockville, MD, USA</td></tr><tr><td>Mohamed Amine Benadjaoud, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Marc Benderitter, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Jean-Michel Bonnet</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Nelson, Chao, MD, MBA</td><td>Duke University Medical Center, Durham, NC, USA</td></tr><tr><td>Alain Chapel, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>David Chen, PhD</td><td>NIAID, Rockville, MD, USA</td></tr><tr><td>Rachael Clark, MD, PhD</td><td>Brigham and Women's Hospital, Boston, MA, USA</td></tr><tr><td>Elise Colin, PhD</td><td>Office National d'Etudes et de Recherches Aérospatiales, Palaiseau, France</td></tr><tr><td>Enzo Delvecchio,</td><td>Ministaire de la Santé and de la Prevention, Paris, France</td></tr><tr><td>Andrea DiCarlo, PhD</td><td>NIAID, Rockville, MD, USA</td></tr><tr><td>Melanie Doyle-Eisele, PhD</td><td>Lovelace Biomedical Research Institute, Albuquerque, NM, USA</td></tr><tr><td>Marvin Edeas, MD, PhD</td><td>Université de Paris, INSERM*, Paris, France</td></tr><tr><td>Mark Ervin, MD</td><td>Radiation Emergency Assistance / Training Center, Oak Ridge, TN, USA</td></tr><tr><td>Stéphane Flamant, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Jean-Christophe Gariel, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Chandan Guha, MD, PhD</td><td>Albert Einstein College of Medicine, New York, NY, USA</td></tr><tr><td>Alain Hovnanian, MD, PhD</td><td>Necker Hospital, Paris, France</td></tr><tr><td>Richard Kolesnick, MD</td><td>Memorial Sloan Kettering Cancer Center, New York, NY, USA</td></tr><tr><td>Vidya Kumar, PhD</td><td>Armed Forces Radiobiology Research Institute, Bethesda, MD, USA</td></tr><tr><td>Naresh Menon, PhD</td><td>Chromologic LLC, Monrovia, CA, USA</td></tr><tr><td>Vincent Mouly, PhD</td><td>Sorbonne Université, INSERM*, Paris, France</td></tr><tr><td>Jean-Marc Philippe, MD, PHD</td><td>Necker Hospital, Paris, France</td></tr><tr><td>Sergey Pigarev, PhD</td><td>Meabco, Inc., Copenhagen, Denmark</td></tr><tr><td>Hervé Raffin, MD, PhD</td><td>Medic'air International, Bagnolet, France</td></tr><tr><td>Merriline Satyamitra, PhD</td><td>NIAID, Rockville, MD, USA</td></tr><tr><td>Alla Shapiro, MD</td><td>Food and Drug Administration (retired), White Oak, MD, USA</td></tr><tr><td>Radia Tamarat, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Jenny Ting, PhD</td><td>University of North Carolina, Chapel Hill, NC, USA</td></tr><tr><td>Christelle Huet, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Jason Sidabras, PhD</td><td>Medical College of Wisconsin, Milwaukee, WI, USA</td></tr><tr><td>Francois Trompier, PhD</td><td>IRSN, Fontenay-aux-Roses, France</td></tr><tr><td>Matthias Port, MD</td><td>Bundeswehr Institute of Radiobiology, Munich, Germany</td></tr></tbody></table>

*Institut National de la Santé et de la Recherche Médicale.

* Develop a sustainable and efficient consortium expert group to assess performance and impact of activities carried out in the field of MCMs and enable connections between international teams to strengthen networking and collaborative research for the future.

The specific discussions of the assembled expert working group were structured around the fields of GI-ARS and CRI/LRI, with other associated interest areas, such as biomarkers, biological and physical dosimetry. This construct included presentations and discussions on diagnosis of exposure and consequences of radiation threat agents; new operational physical or biological dosimetry tools and molecular signatures to diagnose and/or predict ARS severity; and consideration of sensitive laboratory analyses and innovative field tests for rapid assessments with improved performance. Products to address GI-ARS and CRI/LRI encompassed both
<figure><img src="image_16.png" /></figure>

radio-protectants and radio-mitigators. These conversations included new research based on drugs and stem cells or stem cell-derived products, as well as gene therapies and research activities for the design of new technical approaches in other pathologies. Further, innovative approaches, such as the use of artificial intelligence, and new methods and devices to monitor radiation lesions and predict development of complications were a focus. The text below provides a high-level overview of the December 2022 meeting and a follow-up on workshop outcomes but is not intended to be a comprehensive review of cutaneous and GI injuries and radiation exposure assessment. As such, there are multiple areas of research targeting cells and pathways known to be involved in both radiation-induced GI and cutaneous injuries (e.g. Lgr5+ cells and WNT beta catenin signaling), as well as exciting small molecule and other pharmacological products under study that are not discussed below but are obviously of great relevance to the field overall. First initial and last name of the presenter are noted in parentheses to identify the speaker or when pre-publication data are mentioned.

## Background

There are many challenges in organizing and implementing a medical response to exceptional health situations, such as those encountered during a radiological or nuclear public health emergency. To set the scene for the involvement of both the U. S. and France in these efforts, presentations were made by leaders from the IRSN (J.-C. Gariel), and NIAID (A. DiCarlo), along with a talk explaining facilitation of international research by the NIAID (M. Adomako). For context, historical radiation exposures were then discussed, as well as other exceptional health situations (e.g., coronavirus disease-19 (COVID-19). The role of both U. S. and French organizations in responding to radiological or nuclear threats, as well as more broad consideration of other exceptional health situations was also considered. In the decades that have followed the Chernobyl disaster, there have been many reports detailing the therapies attempted in the hours, days, weeks, and months following the accident (A. Shapiro). These interventions included routine medical care and radiation-specific MCMs such as potassium iodide (KI), treatment of superficial radiation skin burns, growth factor administration, and other heroic attempts such as bone marrow transplants. Beyond overwhelming suppression of the bone marrow, the most common manifestations of the exposures were evolution of CRI/LRI, as well as complications involving the GI tract. Insights gained from the handling of patients included understanding the diversity and severity of skin damage and its influence on survival, and the need for early surgeries. It is critical to understand how earlier crises have been handled, to more adequately prepare for possible future threats.

More recently, the handling of COVID-19 medical preparedness provides additional lessons learned, which are also applicable in some respects to a radiological or nuclear mass casualty incident (M. Ervin). In both scenarios, the public's fear likely will be overblown, with a lack of coordinated

government response. It is critical that professional opinions offered by the media be trusted, and subject matter experts must be trained to deliver information and collaborate with non-medical personnel. In addition, the lack of a surge capacity for laboratory testing and medical personnel was an issue during COVID-19, which will also be the case if there is a radiation public health emergency. Lessons learned from COVID-19 were mainly the need to rapidly expand lab/survey capability, to have in place stockpiling plans at the national level ready for deployment, and to develop an automated event registry to follow the population in the years following the incident.

Similarly, responses to other emergency mass casualty situations can also assist first responders during radiological or nuclear emergencies. These incidents could include explosions due to accidents such as gas leaks, industrial disasters (e.g., the Toulouse chemical factory explosion in 2001), or intentional terrorist actions (multi-site terrorist attack in Paris – 2015), all of which were encountered by French emergency and medical professionals over the past decades (H. Raffin). These single and multi-site responses involved basic location requirements that are universal to an equivalent scale incident, and included triage, diagnostics, and initiation of care onsite. Although health systems organize and adapt care at the local, regional or national level, taking all necessary measures to ensure that victims receive timely and appropriate care is critical. The complexity of handling communication with first responders, and the chaos in which evacuations must be undertaken makes for seemingly insurmountable challenges; however, there are many lessons learned from these events, such as the need for multilateral exchange of information, and use of a high-reliability organization model¹, which leverages previous encounters with other high-risk disasters.

In the U. S. and France, there are governmental and non-governmental players engaged in ensuring a rapid and effective medical response to a radiological or nuclear emergency. The Radiation Injury Treatment Network (RITN), comprised of more than 74 U.S. hospitals, seeks to develop guidelines to treat hematopoietic injuries after a radiation exposure (N. Chao). Network experts provide education to health-care workers about managing radiation injuries, coordinating responses during an incident, and providing evaluation and treatment of patients. RITN's current ARS treatment guidelines generally follow standard medical interventions for individuals with chemotherapy-induced toxicities and address reductions in cell counts and other complications. In France, the Organization de la réponse du système de SANté en situations sanitaires exceptionnelles (ORSAN) plan provides coordinated organization of healthcare professionals and systems facing an emergency. To define healthcare pathways and give structure, the basis of ORSAN is tied to education, operational plans, and response strategies. In keeping with this approach, the mission of the IRSN is to support radiological or nuclear emergency prevention and logistical response, considering medical intervention strategies (J-M Philippe), by working with health facilities and other government entities. Individual and regional health facilities have capabilities that can be quickly activated, and training exercises are carried out regularly to ensure familiarity with plans. The IRSN provides national and international
educational training, technical support, and operational backing to national authorities and health care systems to assist with health response operations during an emergency. Through these efforts, the IRSN stands at the ready to provide guidance and support for radiological or nuclear emergencies in France, throughout Europe, and beyond.

## Challenges specific for mass casualties

In terms of victim triage and treatment, the medical response to a radiological or nuclear emergency presents some unique challenges that require altering of traditional practices. In a radiation incident, it is important to discriminate four groups for triage purposes: (1) unexposed, (2) low dose-exposed (does not require immediate care, but needs surveillance for late health effects), (3) high dose-exposed developing ARS and requiring immediate and intensive health care, and (4) very high dose-exposed that are unlikely to survive and may drain resources from a challenged healthcare system. There is a need to design and validate medical diagnostic tests and biodosimeters that will be used, not only early by first responders or health personnel, but also later, in the hospital for confirmatory purposes, or to be employed in medical laboratories. Implementation of different technologies for measuring external exposure could include individual and collective connected dosimetry systems, real time dosimetry, or compact and transportable detectors.

For medical management during a radiological or nuclear emergency, it is important that product formulations are amenable for rapid use in mass casualties. Thus, their route of administration should be noninvasive and require minimal medical oversight (e.g., oral, subcutaneous, transdermal, inhaled, or intramuscular rather than intravenous injection). Liquid formulations of oral products (or specific instructions for compounding tablets or capsules) for sensitive populations, such as pediatric, or geriatric use may be considered, if available. As storage considerations are important factors for the decisions on selecting the pharmaceutical products by the end-users, products with minimal refrigeration requirements and long shelf-lives are preferred, as are lyophilized compounds. Care must be taken to ensure that stockpiled products can be safely dosed in all populations.

## Experimental models of radiation-induced injuries

Because of the rare instances of ARS in humans, researchers and drug developers rely on animal models that faithfully recapitulate the injury under study, in order to assess efficacy of therapeutics for radiation-induced damage.

### Models to address GI-ARS

To study mitigators of radiation-induced GI injury, it is first necessary to develop an animal model that accurately simulates anticipated human responses to and exposure. The U. S. Food and Drug Administration (FDA) has suggested that the model to be used for efficacy determination be one that experiences the damage, but then can also demonstrate regeneration of the

tissue and ultimately, a survival benefit. This specific 'Animal Rule' licensure pathway for products to address chemical, biological, radiological, or nuclear threats (U. S. Food and Drug Administration 2015) states that at least one animal model must be studied (but is generally expected to be two animals; one rodent and one non-rodent) to demonstrate efficacy of the product. Because the doses of irradiation needed to generate GI-ARS are so high as to be universally lethal to the bone marrow, total body irradiation (TBI) models are not appropriate to study GI-targeted MCMs. At the same time, the FDA wants to ensure that the animals experience acute H-ARS, with survivable myelosuppression, so it is important not to shield too high a percentage of the marrow. Therefore, both small and large animal models have been developed that allow for shielding of a minimal percentage of the hematopoietic system from radiation exposure, allowing for survival of enough bone marrow to prevent lethality attributable to H-ARS. Small models include mouse and rat, and larger animals include nonhuman primates and minipigs. A mouse partial-body irradiation (PBI) model has been developed at the Armed Forces Radiobiology Research Institute (V. Kumar) using a linear accelerator (LINAC), using shielding to protect ~2.5% of the bone marrow. The unique aspects of this model are the use of a LINAC to irradiate the animals, and the fact that the percentage of shielding is lower than the 5% that was previously reported (Booth et al. 2012). Dosimetry shows that the radiation dose under the shield is ~18% of the dose to the rest of the body. Radiation dose response curves have been generated for both male and female mice, which suggest a similar $LD_{50/30}$ (lethal dose of irradiation at which 50% of the animals survive for up to 30 days) for each sex, and the model successfully recapitulates both GI-ARS and survivable H-ARS. It has been shown to have utility in looking at MCM efficacy for GI injuries, and also has promise in studying delayed effects, such as lung fibrosis (Kumar et al. 2023).

### Models to address CRI/LRI

Similarly, it is also necessary to model CRI/LRI in an animal with skin attributes similar to humans. CRI/LRI can arise from either gamma-rays from a prompt exposure, or beta burns resulting from incomplete external removal of fallout from the skin. Although some work is done in mouse models, this species is generally not preferred, as its means of healing differs from humans in several key areas. In addition, since the FDA would prefer two animals, other models have gained prominence for their promise in testing CRI/LRI mitigating MCMs. These include minipigs and Yorkshire swine, both of which are believed to be close to humans in their skin responses to irradiation. Multiple CRI/LRI and ARS models are under development at Lovelace Biomedical Research Institute (M. Doyle). With access to several irradiation sources, minipig and large swine models, as well as advanced imaging capabilities, it is possible to accurately track MCM efficacy, wound features, and injury progression (Foubert et al. 2017a; Doyle-Eisele et al. 2021).

Development of a xenograft model in mice that mimics clinical applications would help better characterize drug efficacy and generate transcriptional, functional, and proteomic
<figure><img src="image_17.png" /></figure>

biomarkers in treatment-naive and relapsed disease. Thus, a NOD SCID gamma mouse model grafted with human skin was generated to study biomarkers induced by radiation exposure (R. Clark). Interestingly, the engraftment maintains epithelial differentiation, vasculature, and immune cells of the human skin. Additionally, irradiation impairs the epidermal permeability barrier function of the skin, associated with inflammation, which has also been reported in patients with chronic radiation dermatitis. Evaluation of functional activity showed a radiation-dose effect 24 h post-irradiation. A T-cell mediated inflammatory burst was observed after 1 Gy exposure, and upregulation occurred in genes belonging to the CDKN1A/p21 pathway, p53-mediated apoptosis pathway, and other p53-induced genes. While gene sequencing is a robust approach, an ideal biomarker should be accessible to rapid noninvasive measurements. Immunostaining of skin can confirm protein expression and location of biomarkers; hence, tape stripping allows for a noninvasive detection of both RNA and protein targets on top of the epidermis (Pailler-Mattei et al. 2011). Using this approach, several genes and proteins were found to be upregulated at 24 and 48 h post-exposure. There are plans to identify new biomarkers to develop rapid RNA and protein-based tests.

Responses of skeletal muscles to aging, injury and certain disease states were also considered to provide relevant information for investigating CRI/LRI (V. Mouly). Although muscle tissue has a low rate of cell turnover, it has a high potential for regeneration (Rando 2006). Similarly, muscles are relatively radio-resistant, but do demonstrate adverse impacts at doses of irradiation of ~20Gy. Different patterns of DNA methylation are believed to be involved in some observed aging effects on the muscle, along with a loss of proliferative capacity of myoblasts. In developing muscle models, the feasibility and validity of human to mouse xenografts (human muscle strips in RAG/IL2rb immunodeficient mice) as a preclinical model of myopathy was demonstrated with xenografts of human muscle strips in immunodeficient mice. These findings illustrate the value of a human muscle xenograft in mice as a valid preclinical tool to better investigate the pathogenesis of human genetic myopathies and potentially irradiation, to better predict therapeutic responses.

## Challenges in animal models

There are several considerations that impact the accessibility of novel large and small models to address GI-ARS and CRI/LRI. These factors include higher costs involved in advancing some animal shielding models and the need for health physics expertise in their development. Also, rodent models that rely on the use of genetic modifications can also add to the expense of a study. In addition, several incidents, including intentional bombings (Hiroshima and Nagasaki) and radiation accidents (e.g. Chernobyl and Goiania), have shown the importance of improving the diagnosis and management of radiation combined injuries, which has been addressed in several models, but remains a continuing need, to better understand the multiorgan syndromes that result from these complex exposures (Molinar-Inglis et al. 2024).

## Injury assessment and MCM treatments

In the aftermath of a radiation mass casualty incident, there will be several immediate challenges in the identification of individuals requiring medical attention and determination of severity of their injuries. To address this need, meeting participants discussed the importance of accurate, radiation-specific biodosimetry, and provided background on what state-of-the-art approaches are currently under study, including those on biomarkers that address GI-ARS and CRI/LRI. For bone marrow injuries following exposure, there are now six H-ARS U. S. approved products, including growth factors and biosimilars addressing the neutrophil and macrophage lineages, and a product for radiation-induced thrombocytopenia. These drugs were also successfully administered in France under a compassionate use situation, based on prior data showing their efficacy in clinical management of H-ARS victims (Benderitter et al. 2021), and were recommended by earlier international medical consensus (Gorin et al. 2006; Fliedner et al. 2009). Despite the importance of these accomplishments, there are still many organ injuries that are not responsive to the licensed products, including immediate injuries to the GI tract and skin. There is also a high likelihood that, depending on the nature of the incident, combined injuries (radiation combined with skin concerns, such as thermal burns and other wounds) will be frequent (Iddins et al. 2022). For this reason, both the NIAID and the IRSN have provided funding to address GI-ARS and CRI/LRI, to better understand the mechanism of damage from irradiation, and to develop MCMs to mitigate and treat these injuries, thereby leading to improved survival and a reduction in major morbidities.

## Innovative approaches for assessment of GI-ARS

Several novel approaches to assess GI injury were discussed that involve imaging, including voxel-based analyses that are used to predict local radiation toxicity to the GI tract during prostate tumor radiotherapy (O. Acosta) (Acosta et al. 2013). This advanced dose mapping and 3D organ visualization allows for precise dosing and salvage of normal tissues, thereby minimizing unwanted radiotherapy side effects, such as rectal bleeding (Dréan et al. 2016) and urinary tract toxicities like incontinence (Mylona et al. 2019), and were considered promising for further development for GI-ARS assessment. Other clinical manifestations of radiation injury to the GI tract were also discussed.

## Challenges in the treatment of GI-ARS

Several state-of-the-art products were discussed for their ability to mitigate radiation-induced injuries to the GI tract. These options included use of stem cell-based therapies, such as bone marrow- and adipose-derived stromal cells (C. Guha). In high dose irradiated mice (TBI or abdomen only), injection of bone marrow-derived adherent stromal cells improved survival (Saha et al. 2011), as did administration of extracellular vesicles (EVs) derived from this cell type (Accarie et al. 2020). EVs constitute a heterogeneous group
of cell-derived vesicles and have been classified based on origin, size, composition, and markers small vesicles (van der Pol et al. 2012). These vesicles can contain mRNA, miRNA, proteins, DNA, and nuclear fragments that are dependent on the cell of origin and are considered vectors of biological information and intercellular communication. They were also found to be a promising treatment option for severe radiation injuries (Nanduri et al. 2021; Loinard et al. 2023).

Similar studies have also demonstrated the ability of mesenchymal stem cells (MSCs) to accelerate recovery of irradiated GI tissue in a human/mouse chimeric (Sémont et al. 2006) and minipig model (Linard et al. 2013), and have been used clinically in individuals with GI lesions due to severe radiotherapy squalae (A. Chapel). Four patients injected with MSCs experienced reduced pain, bleeding, diarrhea, and fistula incidence (Voswinkel et al. 2013). A Phase 2 clinical trial involving seven radiotherapy centers continues to explore the efficacy of this approach in patients with chronic radiation injuries that are resistant to conventional treatments. However, given the limitations that have been encountered with some stem cell therapies, and the challenge of their use in a mass casualty setting, the use of EVs is gaining interest as a means of overcoming these difficulties.

In a more targeted approach to addressing GI-ARS, the role of the vasculature was considered in studies that focus on plasma membrane lipid-signaling pathways identified in endothelial cells associated with the GI tract (R. Kolesnick). Ceramide in the outer leaflet clusters after irradiation and induces apoptosis in injured cells (Santana et al. 1996), and levels of endothelial apoptosis are correlated with survival after TBI at levels known to cause lethal GI injuries (Paris et al. 2001). An antibody against ceramide has shown promise as a mitigator of GI-ARS as a subcutaneous injection at 24h post-irradiation (Rotolo et al. 2012). Other, non-cellular approaches discussed included a thrombopoietin mimetic (PEG-TPOm; Janssen) under investigation as a treatment for GI-ARS. Findings indicate that the product reduces gastric hemorrhage and intestinal permeability, stimulates crypt cell proliferation, and improves survival when given post-irradiation (C. Guha).

A novel GI-ARS approach centers on the role of the microbiota in radiation injuries, and how they might be harmed as MCMs (Gebrayel et al. 2022). Studies indicate connections between radiation exposure and a limiting of the diversity of the microbiota, along with a decrease in 'good' and an increase in 'bad' bacteria (M. Edeas). Also discussed were the strategies that are being sought to modify the microbiome of the gut, including use of fecal microbiota transplantation (FMT), pre-/pro-biotics, and bacterial metabolites, as well as the vital role that mitochondria activity plays in microbiota quality (Gebrayel et al. 2022). The importance of the microbiome in radiation was further emphasized in an overview of recent work to identify its correlation with survival after radiation exposure (J. Ting). In those studies, irradiated mice that survived bone marrow-lethal exposures (referred to as 'elite survivors') were found to possess a unique microbiome, which when transplanted into naïve mice protected them from a subsequent

radiation-induced lethality (Guo et al. 2020). Further analysis of the bacterial make-up showed an abundance of several species, which were similar to those identified in patients undergoing bone marrow transplant and were indicative of reduced GI toxicity. Researchers also identified specific small chain fatty acids that appeared to play a role in the observed protection. Another microbiome approach involves the use of the *Lactobacillus reuteri* (LR) probiotic bacterial strain as a method to bring therapeutic cytokines directly to the small intestines (N. Menon). Researchers have orally administered interferon-beta (IFN-β) using this approach, with mice showing higher survival and improved histopathology (Hamade et al. 2023).

## Innovative approaches for CRI/LRI assessment

A CRI/LRI imaging study was carried out using the FDA-approved ARANZ® Silhouette, a laser-based, hand-held system that allows for consistent imaging and study blinding (Foubert et al. 2017b). A second product, eKARE InSight has also proved effective for real-time imaging and analysis. These and other modalities can assess injuries in animal models in a way that improves translation of findings to the clinic. Meabco has also created models of CRI/LRI using male and female Yorkshire-Landrace swine that are irradiated with 80Gy to the skin in a single fraction, and using multiple irradiators (Grenz machine, Strontium-90 source, or a LINAC) (S. Pigarev). Using advanced photography of the lesion (ARANZ Medical 3D Camera), wound planimetry, several scoring rubrics (Radiation Therapy Oncology Group (RTOG) (Hoeller et al. 2003), and Kumar (Kumar et al. 2008)), and dermatoscopy (Derlite® Dermatoscope), they can assess CRI/LRI severity and have collected samples to assay for systemic inflammatory cytokines. Skin burns develop and resolve in the model between days 0 and 120, and wound growth as the animals themselves get larger is taken into account. They are also testing an immunomodulator (BP-C2) to assess its promise as an MCM for CRI/LRI. Early findings suggest that the product is well tolerated and has beneficial skin healing effects.

ITAE Medical Research is developing new medical imaging instruments, which are noninvasive and specifically designed to estimate subcutaneous vascularization of the skin. They propose a technique involving real-time, high-resolution imaging of skin microvascularization based on a process utilizing temporal variation of a spatially depolarized optical speckle field, which is generated by moving red blood cells when illuminated with fully polarized coherent light (E. Colin). Full-field images reveal the microvasculature with a spatial resolution of 80 µm, and acquisition speed allows for real-time applications. They demonstrate the ability of this method to quickly determine stable and reliable microvascular activity, enabling numerous clinical applications that require quantitative measurements (Colin et al. 2022). This approach can lead to interesting clinical equipment for easy and rapid assessment of various skin microvascular pathologies that need a deeper observation than optical coherence tomography angiography, without requiring its depth-resolved imaging capabilities. Another imaging approach with potential to detect the
<figure><img src="image_18.png" /></figure>

severity of radiation-induced CRI/LRI is SimpleITK, an open-source, image analysis library, that provides a virtual reality interface allowing visualization of internal anatomy using computed tomography (CT) scans taken of irradiated animals (D. Chen). Other sources, including those taken with a standard camera and other image capture devices, allow for pictures of wounds to be segmented and analyzed automatically. These methods have also been used to better understand late injuries using lung CT scans taken months post-irradiation in nonhuman primates. Although the use of artificial intelligence is not new in wound evaluation, gaps remain mainly because clinical manifestation of injuries cannot be directly monitored in animals and endpoints are not practical. Further upgrades of these methods would detect backscatter contributions simultaneously parallel and orthogonal to the illumination polarization to distinguish between surface and deeper vascularization.

In the clinic, electron paramagnetic resonance (EPR) is a unique tool for skin research and is being employed for non-invasive detection of endogenous free radical melanin in human skin melanomas (Wehbi et al. 2023). EPR spectroscopy and imaging of free radicals in human skin performed at low-frequency (3 GHz) is a promising technique to study redox metabolism, formation of free radicals and reactive oxygen species (ROS), oxygen concentration, barrier function, and drug penetration in vivo (J. Sidabras). While ROS are pronounced with low ultraviolet-irradiation, lipid oxygen species increase at higher radiation doses. The ratio of the free radical types is a good indicator of radiation exposure; however, there is much interference from the signal to noise ratio, and improvement of EPR sensitivity is required for in vivo use. Applications of these technologies include in vitro (measurement of ROS<pH, pO2 in primary cells or in skin-on-a-chip), or in vivo quantification (ROS in skin, magnetic resonance imaging (MRI), microvasculature imaging, and low-field MRI).

## Challenges in the treatment of CRI/LRI

Unfortunately, there have been numerous instances of CRI/LRI in individuals exposed to radioactivity in several forms. The Radiation Emergency Assistance Center and Training Site (REAC/TS) maintains a database of radiation accidents, from which a number of CRI/LRI cases were considered (M. Ervin). The most common injuries arose from handling a radiation-emitting source, with threshold doses of greater than ~3Gy required to display overt injuries (Gusev et al. 2001). Symptomatic treatment of these patients typically consisted of standard burn therapies, topical and systemic antihistamines, and anti-inflammatories. Important add-ons include appropriate nutrition, analgesics, infection control, dressings, skin substitutes, hyperbaric oxygen, and surgery. As mentioned above, cell therapies (MSCs, adipose-derived stem cell therapy and use of stromal vascular fraction), although not currently FDA-approved, are also in clinical trials for similar indications (NCT01771679).

In other human CRI/LRI incidents dating back to 2005, IRSN has worked with the Hôpital d'Instruction des Armées Percy in Paris, under the umbrella of the International

Atomic Energy Agency, to assess and treat casualties from more than 15 radiation incidents around the world (M. Benderitter). Many of these patients had severe LRI from contact with an IR-192 source, either alone or in combination with H-ARS. Four of these reports were presented, with many of the patients experiencing comparable courses of progression of their injuries, and with similar treatments attempted. Bone-marrow derived MSCs were administered to some patients as an adjuvant treatment to surgery and skin grafting, depending on the size and volume of the lesion. These clinical applications were supported by preclinical studies in pigs (Linard et al. 2018a; 2018b). In all instances, patients experienced complete healing with no pain, further suggesting the promise of cell-based approaches for CRI/LRI. Despite the strengths and perspective in the use of stem cells such as MSCs, the need for a large amount of cell production and banking remains challenging and expensive. In addition, the duration of MSC culture and its quality controls require that treatments be planned in advance, and therefore, patient administration would be delayed for several weeks. Although MSC-derived EVs have a promising role in the medical management of radiation injuries, several challenges need to be addressed before they can be used in the clinic: standardization of production and release criteria, optimized storage conditions, and a lysophilized operational product needs to be validated for emergency situations (Benderitter et al. 2022; Flamant et al. 2023; Loinard et al. 2023).

## Clinical perspectives in treating related injuries

To seek new perspectives on the treatment of radiation-induced skin and gut injuries, participants also explored other disease states with similar presentations, to see if assessment and therapeutics could be harnessed and applied to diagnosis, biodosimetry and MCM development. For example, strategies under study to address genetic skin defects, such as recessive dystrophic epidermolysis bullosa (RDEB) were considered during the meeting (A. Hovnanian). This condition, which involves faulty collagen and anchoring fibrils, results in chronic wounds that manifest as severe inflammation and fibrosis and can also lead to skin cancers that arise at an early age (Tartaglia et al. 2021). Cell therapies (Kiritsi et al. 2021), and gene modification strategies (Siprashvili et al. 2016; Eichstadt et al. 2019) have shown promise as treatments. Combining these therapies with skin grafting approaches has led to testing of genetically modified skin grafts, which are reducing the duration of hospitalization and improving the quality of life of patients with this disease (Gurevich et al. 2022). In considering these successful approaches in the context of radiation, and their clinical status for RDEB, it is possible that they could be adapted as therapies for CRI/LRI.

## Biomarkers in the development of MCMs

The main objectives in biomarker discovery are to determine kinetics under clinically relevant radiation exposures,
with focus on the natural history of disease pathology, and a time-course of these markers that are relevant to the clinical conditions observed (M. Satyamitra). The need for rapid, radiation-specific, noninvasive and robust biomarkers of radiation exposures for biodosimetry needs are crucial since no devices have yet been FDA-cleared for use during a radiation incident. Approaches that have been explored include cytogenetics, transcriptomics, genomics, proteomics, and metabolomics (Satyamitra et al. 2022). The RNCP has identified end-uses for ideal biodosimetry tests: (1) field-deployable methods to assess ≥2 Gy exposure in humans, to differentiate exposed populations from the worried well and permit their triage, (2) laboratory-based, high throughput assays to determine definitive TBI or PBI dose to the exposed humans, and (3) approaches to predict immediate and long-term consequences of radiation injury. Although a variety of biomarkers have been considered for dose estimation and damage assessment after radiation exposure, identification of new radiation-modified molecules could provide qualitative information and quantitative output to facilitate triage and clinical decision-making at different stages after mass casualty radiation incidents. While a first-line assay or kit should provide basic binary response, allowing on site stratification of exposed from non-exposed individuals, secondary molecular tests are in need to refine diagnosis and identify victims with high risk of developing acute injury and DEARE.

## Innovative approaches in biomarkers

Circulating microRNAs (miRNAs) have been extensively studied as disease biomarkers due to their stable presence in body fluids, and several studies have identified a number of time- and dose-specific miRNAs for radiation injury assessment in animal models and patient samples following whole body irradiation. Circulating miRNAs are good biomarker candidates of health effects following radiation exposure (i.e., low invasive tissue accessibility, stability, accuracy and reproducibility of measurement, compatibility with clinical use and automated high-throughput platforms). Chromologic LLC found modified miRNA signatures following radiation exposure that predict health outcome using minimally invasive approaches (fingerstick of blood) in irradiated nonhuman primate models, including whole thoracic lung irradiation, PBI (with 5% bone marrow shielding), and TBI (N. Menon). The company has developed miRNA panels to assess neutropenia, and pulmonary fibrosis risk at 30 days post-exposure. The miRNA signatures in preclinical samples were validated in clinical samples of neutropenia and fibrosis, although additional validation in patient population is necessary (Rogers et al. 2021).

Using a preclinical model of CRI/LRI in rodents, IRSN identified, in a proof-of-concept study, a circulating miRNA diagnosis signature associated with injury severity level, thereby validating the use of systemic (blood) miRNAs as molecular biomarkers of CRI/LRI (S. Flamant). These experiments paved the way for further work to establish early miRNA signatures for prediction of CRI/LRI and its level of severity (Ancel et al. 2024 (in press)). Current research aims to identify acute phase, circulating miRNAs predictive of late

adverse effects in this model (e.g., fibrosis) that could allow an improved and timely intervention to mitigate or prevent further development of late irradiation complications. However, use of miRNAs as biological indicators of radiation injury still faces many challenges, including the need to find more sensitive and radiation-specific miRNAs, or a combination of them, and the specific timepoints and doses after irradiation to achieve optimal results. Inter-individual differences and confounders must also be considered.

Over the last 20 years, circulating EVs have also been investigated as biomarkers in liquid biopsy, because EVs are highly stable and can be found in all body fluids. Given their role as vehicles of intercellular communication, EVs are involved in many (patho)physiological processes. This characteristic, together with their molecular composition that reflects the status of the producing cell, make EVs exploitable tools for diagnostic and therapeutic purposes. At the IRSN, circulating microvesicles have shown promise as biomarkers of radiation toxicity in a cohort of patients with prostate adenocarcinoma who were over-exposed in the Epinal radiotherapy accident in France (Tamarat and Benderitter 2019). The number of EVs directly correlated with severity of adverse events (Ribault et al. 2023), and the protein content of the EVs confirm the presence of molecules involved in coagulation and inflammatory processes. Based on these data, a multicenter prospective study for early detection and prediction of delayed cardiac complications arising as a side effect of breast cancer radiotherapy was conducted (Walker et al. 2018). Preliminary results showed an increase in microvesicles derived from platelets and endothelial cells that was radiation dose-dependent (R. Tamarat). From preclinical and clinical studies, it is clear that research on EVs suffers from limitations. A more detailed molecular profiling of the vesicle cargo as well as a more stringent EV characterization, and standardization of pre-analytical and isolation procedures should be done. Going forward, investigations need to be performed in large animals (pigs and nonhuman primates), and findings should be confirmed in larger prospective cohorts for clinical transfer.

## Challenges in radiation triage and dosimetry

Between 1980 and 2013, there were >600 reports of radiation overexposure to individuals in medical and industrial settings, resulting in >2,000 overexposed individuals and nearly 200 deaths (Coeytaux et al. 2015). Assessment of dose is imperative for medical management of radiation-induced injury and to define follow-up therapeutic strategies. Due to the inherent variability of certain biological indicators of exposure, there still exists a need for physical dosimetry, which can provide important information about the characteristics of exposures that may have been received by individuals. Coupling this information with available biological markers of injury in exposed individuals strengthens the ability to accurately obtain information needed to triage large numbers of potentially exposed individuals.

Typically, tools deployed to assess radiation dose include clinical assessment, and biological or physical dosimetry.
<figure><img src="image_19.png" /></figure>

Physical dosimetric reconstruction can be achieved using experimental or numerical techniques (C. Huet). One approach in physical dosimetry is retrospective dose assessment of biological or non-biological samples, such as electronic components inside a mobile phone, collected from victims or in their close environment, using EPR, thermoluminescence, or optically-stimulated luminescence (Beerten et al. 2011). Physical dosimetric reconstruction consists in reproducing the circumstances of the accident by experimental or numerical means and can give information on the dose distribution within the body if knowledge of the exposure scenario is available. Over the past 20 years, IRSN has been developing the SESAME tool (Simulation of External Source Accident with MEdical images), which combines numerical simulations with a Monte Carlo radiation-material interaction code and a personalized voxel geometry construct from MRI or CT images of the victim. This tool was successfully deployed in dose reconstruction following several small-scale radiation accidents (Huet et al. 2009; Courageot et al. 2011). Physical dose assessment has value in medical management of victims in small-scale radiation accidents, as it helps to guide surgery, assess dose heterogeneity to guide treatments, and can verify efficacy of therapeutic strategies. The IRSN, in collaboration with the French Service de Protection Radiologique des Armées, is also developing a dosimetry tool called Simulation of External Exposures and Dosimetry (SEED). The SEED is a powerful and mobile system that can be deployed at the site of the radiation incident. The tool can capture input data at the site of exposure, model the scene, and display results as a 3-D rendition. Future development includes generating models with increasing complexity to mirror real-life situations and inter-relating dose assessments coming from different locations and techniques.

At the Bundeswehr Institute of Radiobiology, radiation emergencies were initially a focus due to the desire to have a pre-planned response to nuclear power plant accidents (M. Port). However, recent world events have shifted the concern to addressing potential to acts of radiation terrorism. Classic approaches to estimating absorbed dose include whole body counters, metabolite analyses, and clinical evaluation using medical treatment protocols for radiation accident victims (METREPOL) (Fliedner et al. 2008). These approaches are not often accurate (especially at lower ARS severity scores), the logistics of timely responses are challenging, and there are often gaps in harmonization efforts and expertise (Dörr et al. 2017). There are also complexities associated with radiation (quality, source, dose and dose rate, PBI/TBI, homogeneity, routes) and inherent differences in radiation sensitivity. Recently, an approach that integrates clinical signs and symptoms with cytogenetics into an algorithm (H-Module) has led to more accurate results (Dörr et al. 2017). There is a convergence of exposure reconstruction using both physical and biological dosimetry assays to assist in medical management. In a recent finding, H-ARS could be predicted using a four gene panel in 29 irradiated nonhuman primates in the first two days post-irradiation (Port et al. 2016). Increased high throughput of this assay (1,000 samples in 30h) classified H-ARS severity categories

corresponding to radiation dose with an accuracy of 90-97% (Port et al. 2019). Therefore, while focusing on dose and retrospective biodosimetry is challenging for prediction of health effects, biomarkers and clinical outcome prediction are more promising.

With the advent of advanced programming languages, it is also now possible, using open-source tools (e.g. Biodose Tools, developed by RENEB (Running the European Network of Biological and retrospective physical dosimetry), to convert data generated on the intensity of a radiation-induced cytogenetic biomarker response and its kinetics into an estimate of the dose received (A. Benadjaoud). Using Biodose Tools and R programming to develop an app, it is now possible to ascertain dose information from an incident using levels of dicentrics or chromosomal translocations (Hernández et al. 2023). This app has already been used in global training exercises and has allowed for further validation and continued improvement. Future work includes expanding its application for micronuclei markers, and to make the app more amenable to inter-laboratory harmonization efforts. However, a correct detection of such chromosomal aberration requires trained specialists, as chromosomes are deformable objects, which makes their scoring challenging. In the context of a large-scale incident, manual aberration scoring is widely acknowledged to be a bottleneck and automated solutions are required. In 2020, IRSN initiated a project to explore potential applications of the recent advances of deep learning in computer vision to cytogenetic imaging (A. Benadjaoud). Trained on a large spatial labelled dataset including around five thousands images containing chromosomal aberrations, the proposed solution was based on the U-Net architecture (Ronneberger et al. 2015). The obtained model was able to estimate robust calibration curves on an independent, spatially-unlabeled dataset comprised of over twenty thousand images.

EPR-based dosimetry uses the principle of free radical formation and defects in organic or mineral substances following irradiation, with EPR signal intensity being directly proportional to the absorbed dose (F. Trompier). As mentioned above, after an incident, these materials can be harnessed from the environmental proximity of the exposed individual or from biological samples from the victim. (Trompier et al. 2009). Of the biological samples mentioned, bone has been the most widely used for specific application of EPR-dosimetry supporting medical management; however, while bone EPR is signal specific and abundantly available, it is highly invasive to sample and needs complex processes before being measured. Beyond these factors, the physical characteristics of the exposure during radiological accidents are diverse, with most involving localized exposures, while others are heterogenous exposures or from internal contamination (ICRU Report 94, 2019). The effect of remodeling on EPR radio-induced signal in bone remains to be evaluated. Other promising biological materials are teeth and nails (Fattibene et al. 2023). A key area for future EPR research lies in addressing problems with standardization and certification for analysis, and applicability for evaluating damage to skin, soft tissue and other internal organs. IRSN has worked on triage techniques using touch screen or
smartphones with a small, light and inexpensive EPR spectrometer that can be fully automated and could be carried by emergency personnel. Confirmation of exposure for identified irradiated individuals could be done with tooth enamel mini-biopsies measured with Q-band EPR. In triage mode, with a 5-minute measurement per sample, it was the possible to categorize individuals (<1 Gy, 1–2 Gy, 2–4 Gy, >4 Gy) with less than 7% error. Therefore, IRSN’s overall triage capacity could be up to 2,000 samples per week.

An adequate 3D dose reconstruction can also be incorporated in risk models to predict the occurrence of undesirable radio-induced effects. A new framework was presented (O. Acosta) for 3D toxicity models, which tackles the lack of spatial accuracy of current dose volume histogram-based models by involving 3D spatial dose comparisons via non-rigid constrained registration (Dréan et al. 2016). These dose volume map analyses allow identification of high-risk of toxicity to sub-regions or organs without prior assumptions, and implication of specific sub-regions have been identified for rectal bleeding and urinary symptoms (Mylona et al. 2020). Challenges remain in external validation of these models as well as their extrapolation from clinical to accidental context, with regards to differences in dose distribution and toxicity outcomes.

## Importance of dosimetry

There are three major areas of dosimetry focus, including reference dosimetry, irradiation and dosimetry reporting in published literature, and the impact in biological dosimetry. In addition to beam characterization described in standard protocols (Ma et al. 2001), distribution of the dose in the biological site by accounting for field homogeneity and setup effects is also important. There is, however, a large gap in reporting standards for physics and dosimetry in radiobiology studies that contribute to a reproducibility problem (Draeger et al. 2020). Another important aspect is the need to harmonize irradiation and dosimetry protocols, as there are many facilities that fail to deliver accurate doses with well-defined geometry, especially those using X-ray irradiators. This observation also factored into a cytogenetics exercise carried out by 21 RENEB partners to investigate the influence of calibration practices and protocols on dose estimation (Trompier et al. 2017). Deviation in dose of >10% was observed in 5/21 facilities and corrective measures were then instituted to improve overall performances. Therefore, to harmonize procedures for dosimetry and irradiation, accurate and detailed reporting in published literature is needed, as well as continuous training among dosimetry and health physicists.

## Discussion of future areas of shared interest

Much has been learned over the past twenty years, yet more remains to be explored, through both preclinical work on relevant animal models and exploratory clinical trials. Indeed, a matter of serious consideration concerns the decision to move into clinical experimentation on the basis of available data. There is never enough preclinical data, but

there is information that can only be obtained from patients, such as adverse events that may not manifest in animals. There was general agreement that it is critical to ensure that appropriate radiation dosimetry is used in all preclinical animal studies. It was also discussed that combined injuries will be expected in the wake of a radiological or nuclear emergency, so consideration of this complex biological damage needs to be addressed, in terms of development of large animal models like the pig, and how these injuries could impact triage and predictive biomarkers as well as MCM efficacy.

The role of the gut microbiota in GI disease has been established and the future of the field of GI-ARS research will clearly involve understanding the role that the microbiome plays, not only in determining sensitivity to exposure, but also as mediators of potential beneficial effects and indicators of damage. The gut microbiome is also associated with many GI and non-GI conditions, including diabetes, metabolic syndrome, obesity, colon cancer, and others. Data on long-term safety of fecal microbiota transplant is lacking: larger long-term follow-up studies are needed to identify potential long-term adverse events that would have an impact on the process of donor selection.

Clinical transfer remains a major challenge for novel therapeutics based on drugs, stem cells, and alternative strategies like EVs. There is a need to confirm the benefits of these new treatments in large animal models to validate their safety and efficacy for tissue regeneration. Despite the promising therapeutic potential of MSC-based therapies, several limitations have been identified, including reliance on autologous adult stem cells, the necessity for careful in vitro expansion, the limited quantity of cells produced, potential functional impairment of stem cells, and cost. These constraints hinder the application of MSCs in scenarios involving mass accidents, as do requirements surrounding biobanking systems and stockpiling. An alternative approach involves the use of MSCs derived from human induced pluripotent stem cells (hiPSCs), which can be expanded without limits.

## Conclusions

This international meeting, which involved both U. S. and European investigators, is part of a larger effort to establish and strengthen global relationships in the radiation research community. By providing a forum for investigators to come together to share their research findings, as well as dedicated discussion sessions, the organizers encouraged the initiation of scientific partnerships between scientists engaging in a wide variety of topics of interest for radiation medical preparedness. As a result of the workshop, seven global collaborations, funded by both the NIAID and IRSN, were established on topics ranging from MCMs and innovative predictive biomarkers, and using EPR to assess CRI/LRI, to mechanistic studies deciphering biological mechanism of radiation-induced damage in multiple organ systems. Further, NIAID worked with IRSN and other subject matter experts to publish commentaries highlighting the need for minimum reporting standards in publications involving preclinical irradiations, with the intent to encourage researchers to better
<figure><img src="image_20.png" /></figure>

understand the importance of reporting on basic dosimetry to improve rigor and reproducibility of data (Poirier et al. 2023; Trompier et al. 2024). On 14 March 2024, the NIAID and IRSN signed a new Statement of Intent, which will only strengthen existing interactions and established research collaborations. Going forward, both agencies plan to expand out these interactions by incorporating investigators from across the globe, while attempting to still maintain the informal setting that helped to make the 2022 meeting so successful.

## Note

1. https://en.wikipedia.org/wiki/High_reliability_organization.

## Acknowledgments

The authors thank the IRSN administrative staff for their logistical work to host a successful meeting. We also thank the U. S. and European meeting participants for their valuable presentations and their willingness to work collaboratively to advance the state of the science in the field of diagnosis, mitigation, and treatment of normal tissue radiation-induced injuries.

## Disclosure statement

No potential conflict of interest was reported by the author(s).

## Funding

The author(s) reported there is no funding associated with the work featured in this article.

## Notes on contributors

**Radia Tamarat**, PhD is a Senior Expert in Medical Response in Nuclear and Radiological Emergency at the Department of Health, IRSN, Fontenay Aux Roses, France.

**Merriline M. Satyamitra**, PhD in radiation biology, serves as a Program Officer, Contracting Officer's Representative and biodosimetry lead in the Radiation and Nuclear Countermeasures Program, NIAID, NIH, Rockville, MD, USA.

**Marc Benderitter**, PhD is a radiopathologist and the head of the Department of RAdiobiology and regenerative MEDicine (SERAMED) at IRSN, Fontenay Aux Roses, France.

**Andrea L. DiCarlo**, PhD is the Director of the Radiation and Nuclear Countermeasures Program, NIAID, NIH, Rockville, MD, USA.

## ORCID

Merriline M. Satyamitra ID http://orcid.org/0000-0003-2207-4636

Andrea L. DiCarlo ID http://orcid.org/0000-0001-8113-0015

## References

Accarie A, l'Homme B, Benadjaoud MA, Lim SK, Guha C, Benderitter M, Tamarat R, Sémont A. 2020. Extracellular vesicles derived from mesenchymal stromal cells mitigate intestinal toxicity in a mouse model of acute radiation syndrome. Stem Cell Res Ther. 11(1):371. doi:10.1186/s13287-020-01887-1

Acosta O, Drean G, Ospina JD, Simon A, Haigron P, Lafond C, de Crevoisier R. 2013. Voxel-based population analysis for correlating local dose and rectal toxicity in prostate cancer radiotherapy. Phys Med Biol. 58(8):2581-2595.

Ansel L, Gabillot O, Szurewsky C, Granger R, Sache A, Voyer F, Gruel G, Illiano S, Benderitter M, Le Guen B, et al. 2024. MicroRNA blood signature for localized radiation injury. Sci Rep. 14(1):2681. doi:10.1038/s41598-024-52258-2

Beerten K, Reekmans F, Schroeyers W, Lievens L, Vanhavere F. 2011. Dose reconstruction using mobile phones. Radiat Prot Dosimetry. 144(1-4):580-583.

Benderitter M, Herrera-Reyes E, Gigov Y, Souleau B, Huet C, Trompier F, Fagot T, Grégoire E, Malfuson JV, Konopacki-Potet J, et al. 2021. Hematopoietic recovery using multi-cytokine therapy in 8 patients presenting radiation-induced myelosuppression after radiological accidents. Radiat Res. 196(6):668-679.

Benderitter M, Herrera-Reyes E, Tamarat R. 2022. Mesenchymal stromal cells in the regeneration of radiation-induced organ sequelae: will they make the difference? J Radiol Prot. 42(2):024001. doi:10.1088/1361-6498/ac6dd8

Booth C, Tudor G, Tudor J, Katz BP, MacVittie TJ. 2012. Acute gastrointestinal syndrome in high-dose irradiated mice. Health Phys. 103(4):383-399. doi:10.1097/hp.0b013e318266ee13

Coeytaux K, Bey E, Christensen D, Glassman ES, Murdock B, Doucet C. 2015. Reported radiation overexposure accidents worldwide, 1980-2013: a systematic review. PLOS One. 10(3):e0118709. doi:10.1371/journal.pone.0118709

Colin E, Plyer A, Golzio M, Meyer N, Favre G, Orlik X. 2022. Imaging of the skin microvascularization using spatially depolarized dynamic speckle. J Biomed Opt. 27(4):046003. doi:10.1117/1.JBO.27.4.046003

Courageot E, Huet C, Clairand I, Bottollier-Depois JF, Gourmelon P. 2011. Numerical dosimetric reconstruction of a radiological accident in South America in April 2009. Radiat Prot Dosimetry. 144(1-4):540-542.

DiCarlo AL, Tamarat R, Rios CI, Benderitter M, Czarniecki CW, Allio TC, Macchiarini F, Maidment BW, Jourdain JR. 2017. Cellular therapies for treatment of radiation injury: report from a NIH/NIAID and IRSN workshop. Radiat Res. 188(2):e54-e75.

Dörr H, Abend M, Blakely WF, Bolduc DL, Boozer D, Costeira T, Dant T, De Amicis A, De Sanctis S, Dondey M, et al. 2017. Using clinical signs and symptoms for medical management of radiation casualties - 2015 NATO exercise. Radiat Res. 187(3):273-286.

Doyle-Eisele M, Brower J, Aiello K, Ferranti E, Yaeger M, Wu G, Weber W. 2021. Developing and comparing models of hematopoietic-acute radiation syndrome in Göttingen and Sinclair minipigs. Int J Radiat Biol. 97(sup1):S73-S87. doi:10.1080/09553002.2020.1820604

Draeger E, Sawant A, Johnstone C, Koger B, Becker S, Vujaskovic Z, Jackson IL, Poirier Y. 2020. A dose of reality: How 20 years of incomplete physics and dosimetry reporting in radiobiology studies may have contributed to the reproducibility crisis. Int J Radiat Oncol Biol Phys. 106(2):243-252.

Dréan G, Acosta O, Ospina JD, Fargeas A, Lafond C, Corrégé G, Lagrange JL, Créhange G, Simon A, Haigron P, et al. 2016. Identification of a rectal subregion highly predictive of rectal bleeding in prostate cancer IMRT. Radiother Oncol. 119(3):388-397.

Eichstadt S, Barriga M, Ponakala A, Teng C, Nguyen NT, Siprashvili Z, Nazaroff J, Gorell ES, Chiou AS, Taylor L, et al. 2019. Phase 1/2a clinical trial of gene-corrected autologous cell therapy for recessive dystrophic epidermolysis bullosa. JCI Insight. 4(19):e130554. doi:10.1172/jci.insight.130554

Fattibene P, Trompier F, Bassinet C, Ciesielski B, Discher M, Eakins J, Gonzales CA, Huet C, Lee J, Marciniak A, et al. 2023. Reflections on the future developments of research in retrospective physical dosimetry. Phys Open. 14:1-16.

Flamant S, Loinard C, Tamarat R. 2023. Msc beneficial effects and limitations, and msc-derived extracellular vesicles as a new cell-free therapy for tissue regeneration in irradiated condition. Environ Adv. 13:100408.

Fliedner TM, Chao NJ, Bader JL, Boettger A, Case C, Jr., Chute J, Confer DL, Ganser A, Gorin NC, Gourmelon P, et al. 2009. Stem
cells, multiorgan failure in radiation emergency medical preparedness: A U. S./European consultation workshop. Stem Cells. 27(5):1205-1211. doi:10.1002/stem.16

Fliedner TM, Powles R, Sirohi B, Niederwieser D, European Group for Blood and Marrow Transplantation (EBMT) Nuclear Accident Committee (NAC). 2008. Radiologic and nuclear events: The METREPOL severity of effect grading system. Blood. 111(12):5757-5758. doi:10.1182/blood-2008-04-150243

Foubert P, Doyle-Eisele M, Gonzalez A, Berard F, Weber W, Zafra D, Alfonzo Z, Zhao S, Tenenhaus M, Fraser JK. 2017a. Development of a combined radiation and full thickness burn injury minipig model to study the effects of uncultured adipose-derived regenerative cell therapy in wound healing. Int J Radiat Biol. 93(3):340-350.

Foubert P, Zafra D, Liu M, Rajoria R, Gutierrez D, Tenenhaus M, Fraser JK. 2017b. Autologous adipose-derived regenerative cell therapy modulates development of hypertrophic scarring in a red duroc porcine model. Stem Cell Res Ther. 8(1):261. doi:10.1186/s13287-017-0704-1

Gebrayel P, Nicco C, Al Khodor S, Bilinski J, Caselli E, Comelli EM, Egert M, Giaroni C, Karpinski TM, Loniewski I, et al. 2022. Microbiota medicine: towards clinical revolution. J Transl Med. 20(1):111. doi:10.1186/s12967-022-03296-9

Gorin NC, Fliedner TM, Gourmelon P, Ganser A, Meineke V, Sirohi B, Powles R, Apperley J. 2006. Consensus conference on european preparedness for haematological and other medical management of mass radiation accidents. Ann Hematol. 85(10):671-679. doi:10.1007/s00277-006-0153-x

Guo H, Chou W-C, Lai Y, Liang K, Tam JW, Brickey WJ, Chen L, Montgomery ND, Li X, Bohannon LM, et al. 2020. Multi-omics analyses of radiation survivors identify radioprotective microbes and metabolites. Science. 370(6516):eaay9097. doi:10.1126/science.aay9097

Gurevich I, Agarwal P, Zhang P, Dolorito JA, Oliver S, Liu H, Reitze N, Sarma N, Bagci IS, Sridhar K, et al. 2022. *In vivo* topical gene therapy for recessive dystrophic epidermolysis bullosa: A phase I and 2 trial. Nat Med. 28(4):780-788. doi:10.1038/s41591-022-01737-y

Gusev IA, Guskova AK, Mettler FA. 2001. Medical management of radiation accidents. Boca Raton, FL: CRC Press.

Hamade DF, Epperly MW, Fisher R, Hou W, Shields D, van Pijkeren JP, Mukherjee A, Yu J, Leibowitz BJ, Vlad AM, et al. 2023. Release of interferon-β (ifn-β) from probiotic *limosilactobacillus reuteri*-ifn-β (Ir-ifn-β) mitigates gastrointestinal acute radiation syndrome (gi-ars) following whole abdominal irradiation. Cancers. 15(6):1670. doi:10.3390/cancers15061670

Hernández A, Endesfelder D, Einbeck J, Puig P, Benadjaoud MA, Higueras M, Ainsbury E, Gruel G, Oestreicher U, Barrios L, et al. 2023. Biodose tools: an R shiny application for biological dosimetry. Int J Radiat Biol. 99(9):1378-1390.

Hoeller U, Tribius S, Kuhlmeier A, Grader K, Fehlauer F, Alberti W. 2003. Increasing the rate of late toxicity by changing the score? A comparison of RTOG/EORTC and LENT/SOMA scores. Int J Radiat Oncol Biol Phys. 55(4):1013-1018.

Huet C, Lemosquet A, Clairand I, Rioual JB, Franck D, de Carlan L, Aubineau-Lanièce I, Bottollier-Depois JF. 2009. Sesame: a software tool for the numerical dosimetric reconstruction of radiological accidents involving external sources and its application to the accident in Chile in December 2005. Health Phys. 96(1):76-83. doi:10.1097/01.HP.0000327661.90794.0f

ICRU Report 94. 2019. Methods for initial-phase assessment of individual doses following acute exposures to ionizing radiation. J ICRU. 94:3-162.

Iddins CJ, DiCarlo AL, Ervin MD, Herrera-Reyes E, Goans RE. 2022. Cutaneous and local radiation injuries. J Radiol Prot. 42(1):011001. doi:10.1088/1361-6498/ac241a

Kiritsi D, Dieter K, Niebergall-Roth E, Fluhr S, Daniele C, Esterlechner J, Sadeghi S, Ballikaya S, Erdinger L, Schauer F, et al. 2021. Clinical trial of ABCB5+ mesenchymal stem cells for recessive dystrophic epidermolysis bullosa. JCI Insight. 6(22):e151922. doi:10.1172/jci.insight.151922

Kumar S, Kolozsvary A, Kohl R, Lu M, Brown S, Kim JH. 2008. Radiation-induced skin injury in the animal model of scleroderma:

implications for post-radiotherapy fibrosis. Radiat Oncol. 3(1):40. doi:10.1186/1748-717X-3-40

Kumar VP, Wuddie K, Tsioplaya A, Weaver A, Holmes-Hampton GP, Ghosh SP. 2023. Development of a multi-organ radiation injury model with precise dosimetry with focus on GI-ARS. Radiat Res. 201(1):19-34.

Linard C, Brachet M, L'homme B, Strup-Perrot C, Busson E, Bonneau M, Lataillade JJ, Bey E, Benderitter M. 2018a. Long-term effectiveness of local BM-MSCs for skeletal muscle regeneration: a proof of concept obtained on a pig model of severe radiation burn. Stem Cell Res Ther. 9(1):299. doi:10.1186/s13287-018-1051-6

Linard C, Brachet M, Strup-Perrot C, L'homme B, Busson E, Squiban C, Holler V, Bonneau M, Lataillade JJ, Bey E, et al. 2018b. Autologous bone marrow mesenchymal stem cells improve the quality and stability of vascularized flap surgery of irradiated skin in pigs. Stem Cells Transl Med. 7(8):569-582. doi:10.1002/sctm.17-0267

Linard C, Busson E, Holler V, Strup-Perrot C, Lacave-Lapalun JV, Lhomme B, Prat M, Devauchelle P, Sabourin JC, Simon JM, et al. 2013. Repeated autologous bone marrow-derived mesenchymal stem cell injections improve radiation-induced proctitis in pigs. Stem Cells Transl Med. 2(11):916-927. doi:10.5966/sctm.2013-0030

Loinard C, Ribault A, Lhomme B, Benderitter M, Flamant S, Paul S, Dubois V, Lai RC, Lim SK, Tamarat R. 2023. HuMSC-EV induce monocyte/macrophage mobilization to orchestrate neovascularization in wound healing process following radiation injury. Cell Death Discov. 9(1):38. doi:10.1038/s41420-023-01335-y

Ma CM, Coffey CW, DeWerd LA, Liu C, Nath R, Seltzer SM, Seuntjens JP, AAoPi M, American Association of Physicists in Medicine. 2001. AAPM protocol for 40-300 kV X-ray beam dosimetry in radiotherapy and radiobiology. Med Phys. 28(6):868-893.

Molinar-Ingles O, DiCarlo AL, Lapinskas PJ, Rios CI, Satyamitra MM, Silverman TA, Winters TA, Cassatt DR. 2024. Radiation-induced multi-organ injury. Int J Radiat Biol. 100(3):486-504.

Mylona E, Acosta O, Lizee T, Lafond C, Crehange G, Magné N, Chiavassa S, Supiot S, Ospina Arango JD, Campillo-Gimenez B, et al. 2019. Voxel-based analysis for identification of urethrovesical subregions predicting urinary toxicity after prostate cancer radiation therapy. Int J Radiat Oncol Biol Phys. 104(2):343-354.

Mylona E, Ebert M, Kennedy A, Joseph D, Denham J, Steigler A, Supiot S, Acosta O, de Crevoisier R. 2020. Rectal and urethro-vesical subregions for toxicity prediction after prostate cancer radiation therapy: validation of voxel-based models in an independent population. Int J Radiat Oncol Biol Phys. 108(5):1189-1195.

Nanduri LSY, Duddempudi PK, Yang WL, Tamarat R, Guha C. 2021. Extracellular vesicles for the treatment of radiation injuries. Front Pharmacol. 12:662437. doi:10.3389/fphar.2021.662437

Pailler-Mattei C, Guerret-Piécourt C, Zahouani H, Nicoli S. 2011. Interpretation of the human skin biotribological behaviour after tape stripping. J R Soc Interface. 8(60):934-941.

Paris F, Fuks Z, Kang A, Capodieci P, Juan G, Ehleiter D, Haimovitz-Friedman A, Cordon-Cardo C, Kolesnick R. 2001. Endothelial apoptosis as the primary lesion initiating intestinal radiation damage in mice. Science. 293(5528):293-297. doi:10.1126/science.1060191

Poirier Y, DeWerd LA, Trompier F, Santos MD, Sheng K, Kunugi K, Satyamitra MM, DiCarlo AL, Winters TA. 2023. Minimum reporting standards should be expected for preclinical radiobiology irradiators and dosimetry in the published literature. Radiat Res. 200(3):217-222. 216. doi:10.1667/RADE-23-00119.1

Port M, Herodin F, Valente M, Drouet M, Lamkowski A, Majewski M, Abend M. 2016. First generation gene expression signature for early prediction of late occurring hematological acute radiation syndrome in baboons. Radiat Res. 186(1):39-54.

Port M, Ostheim P, Majewski M, Voss T, Haupt J, Lamkowski A, Abend M. 2019. Rapid high-throughput diagnostic triage after a mass radiation exposure event using early gene expression changes. Radiat Res. 192(2):208-218.

Rando TA. 2006. Stem cells, ageing and the quest for immortality. Nature. 441(7097):1080-1086. doi:10.1038/nature04958

Ribault A, Benadjaoud MA, Squiban C, Arnaud L, Judicone C, Leroyer AS, Rousseau A, Huet C, Guha C, Benderitter M, et al. 2023.
<figure><img src="image_21.png" /></figure>

Circulating microvesicles correlate with radiation proctitis complication after radiotherapy. Sci Rep. 13(1):2033. doi:10.1038/s41598-022-21726-y

Rogers CJ, Kyubwa EM, Lukaszewicz AI, Starbird MA, Nguyen M, Copeland BT, Yamada-Hanff J, Menon N. 2021. Observation of unique circulating miRNA signatures in nonhuman primates exposed to total-body vs. whole thorax lung irradiation. Radiat Res. 196(5):547–559.

Ronneberger O, Fischer P, Brox T. 2015. U-net: Convolutional networks for biomedical image segmentation, in medical image computing and computer-assisted intervention (MICCAI). Paper presented at: International Conference on Medical Image Computing and Computer-Assisted Intervention; October 5–9, 2015, proceedings, part III 18, Munich, Germany. Springer International Publishing

Rotolo J, Stancevic B, Zhang J, Hua G, Fuller J, Yin X, Haimovitz-Friedman A, Kim K, Qian M, Cardó-Vila M, et al. 2012. Anti-ceramide antibody prevents the radiation gastrointestinal syndrome in mice. J Clin Invest. 122(5):1786–1790.

Saha S, Bhanja P, Kabarriti R, Liu L, Alfieri AA, Guha C. 2011. Bone marrow stromal cell transplantation mitigates radiation-induced gastrointestinal syndrome in mice. PLOS One. 6(9):e24072. doi:10.1371/journal.pone.0024072

Santana P, Peña LA, Haimovitz-Friedman A, Martin S, Green D, McLoughlin M, Cordon-Cardo C, Schuchman EH, Fuks Z, Kolesnick R. 1996. Acid sphingomyelinase-deficient human lymphoblasts and mice are defective in radiation-induced apoptosis. Cell. 86(2):189–199. doi:10.1016/s0092-8674(00)80091-4

Satyamitra MM, DiCarlo AL, Hollingsworth BA, Winters TA, Taliaferro LP. 2022. Development of biomarkers for radiation biodosimetry and medical countermeasures research: current status, utility, and regulatory pathways. Radiat Res. 197(5):514–532. doi:10.1667/RADE-21-00157.1

Sémont A, François S, Mouiseddine M, François A, Saché A, Frick J, Thierry D, Chapel A. 2006. Mesenchymal stem cells increase self-renewal of small intestinal epithelium and accelerate structural recovery after radiation injury. Adv Exp Med Biol. 585:19–30. doi:10.1007/978-0-387-34133-0_2

Siprashvili Z, Nguyen NT, Gorell ES, Loutit K, Khuu P, Furukawa LK, Lorenz HP, Leung TH, Keene DR, Rieger KE, et al. 2016. Safety and wound outcomes following genetically corrected autologous epidermal grafts in patients with recessive dystrophic epidermolysis bullosa. JAMA. 316(17):1808–1817. doi:10.1001/jama.2016.15588

Tamarat R, Benderitter M. 2019. The medical follow-up of the radio-logical accident: Épinal 2006. Radiat Res. 192(3):251–257.

Tartaglia G, Cao Q, Padron ZM, South AP. 2021. Impaired wound healing, fibrosis, and cancer: the paradigm of recessive dystrophic epidermolysis bullosa. Int J Mol Sci. 22(10):5104.

Trompier F, Bassinet C, Wieser A, De Angelis C, Viscomi D, Fattibene P. 2009. Radiation-induced signals analysed by EPR spectrometry applied to fortuitous dosimetry. Ann Ist Super Sanita. 45(3):287–296.

Trompier F, Baumann M, Barrios L, Gregoire E, Abend M, Ainsbury E, Barnard S, Barquinero JF, Bautista JA, Brzozowska B, et al. 2017. Investigation of the influence of calibration practices on cytogenetic laboratory performance for dose estimation. Int J Radiat Biol. 93(1):118–126.

Trompier F, DeWerd LA, Poirier Y, Dos Santos M, Sheng K, Kunugi KA, Winters TA, DiCarlo AL, Satyamitra M. 2024. Minimum reporting standards should be expected for preclinical radiobiology irradiators and dosimetry in the published literature. Int J Radiat Biol. 100(1):1–6.

U. S. Food and Drug Administration. 2015. Guidance for industry: product development under the animal rule. [accessed 2024 Jan 29]. https://www.fda.gov/downloads/drugs/guidances/ucm399217.pdf.

van der Pol E, Böing AN, Harrison P, Sturk A, Nieuwland R. 2012. Classification, functions, and clinical relevance of extracellular vesicles. Pharmacol Rev. 64(3):676–705. doi:10.1124/pr.112.005983

Voswinkel J, Francois S, Gorin NC, Chapel A. 2013. Gastro-intestinal autoimmunity: preclinical experiences and successful therapy of fistulizing bowel diseases and gut graft versus host disease by mesenchymal stromal cells. Immunol Res. 56(2–3):241–248. doi:10.1007/s12026-013-8397-8

Walker V, Crijns A, Langendijk J, Spoor D, Vliegenthart R, Combs SE, Mayinger M, Eraso A, Guedea F, Fiuza M, et al. 2018. Early detection of cardiovascular changes after radiotherapy for breast cancer: protocol for a European Multicenter Prospective Cohort Study (MEDIRAD early heart study). JMIR Res Protoc. 7(10):e178. doi:10.2196/resprot.9906

Wehbi M, Harkemanne E, Mignion L, Joudiou N, Tromme I, Baurain JF, Gallez B. 2023. Towards characterization of skin melanoma in the clinic by electron paramagnetic resonance (EPR) spectroscopy and imaging of melanin. Mol Imaging Biol. Epub ahead of print. doi:10.1007/s11307-023-01836-3