Title: Identifying a utility for dentally derived extracellular vesicles to restore impaired bone healing associated with age-related systemic conditions
Funder: Dunhill Medical Trust

Abstract: Human bone has a high capacity for regeneration, but for patients where bone metabolism is impaired, such as osteoporosis and chronic diabetes, clinical management of bone healing remains a major clinical challenge. Osteoporosis is highly prevalent in women aged 80+ and incidences of type 2 diabetes predominate in males aged 70+; age groups correlating with high incidences of complex bone fractures and hip replacements. These patients respond poorly to bone grafts and other bone substitutes available and care-plans for these patients are often lengthy due to arising complications. Important in bone repair processes are mesenchymal stem cells, whose activities are tightly regulated by complex combinations of bioactive proteins, including growth factors, present at the wound healing site at optimal concentrations to secure successful repair. Of note, native extracellular matrix derived from bone [1] and dentine [2], that contain many relevant osseoinductive biofactors, have been demonstrated to accelerate bone healing in diabetic animal models, restoring the signalling environment. However, harvest of sufficient tissue hinders clinical translation. Research has shown a proven ability for dental pulp stem cells to synthesise a variety of connective tissues [3] including bone. The ease with which these cells are recovered from naturally exfoliating “milk” teeth (termed SHEDS), compared to bone marrow stem cells, requiring surgical harvest from central marrow, have supported their use for stem cell-based therapies. SHEDs are commercially banked, and allogenic use of typed-cell lines, providing immuno-suppressive activity, is proposed [4]. However, as for other stem cell therapy proposals, issues for maintaining cell survival and biological differences due to donor cell heterogeneity produce unpredictable responses. SHEDs produce extracellular vesicles (Dental EVs) that facilitate paracrine cellular communication, but research relevant for use in tissue engineering is very limited. Our own data reveals that Dental EVs contain a bioactive cargo capable of initiating bone repair processes when exposed to naïve bone-derived MSCs. Moreover, selection of sub-populations of SHEDs can enhance pro-osteogenic activity of secreted Dental EVs. With a hypothesis that Dental EVs can be harvested to produce a product-driven predictable biological response for promoting bone repair, this proposal aims to:- (1) provide the first clear scientific descriptions of pertinent signalling mechanisms for Dental EVs in facilitating bone repair; (2) determine how selection of SHED sub-populations can optimise the osseoinductive efficacy of Dental EVs to deliver a predictable bone healing response; (3) demonstrate scale-up potential for collection of Dental EVs to provide added attractiveness for translational development.

Lay abstract: The young human body has a great capacity for bone healing, but for patients with conditions such as osteoporosis and chronic diabetes their ability to repair bone is weakened. Population studies indicate that osteoporosis is highest amongst 80+ year-old women and type 2 diabetes is highest for 70+ year-old men; ages where incidences of complex bone fractures and hip replacements are greatest. Care for these patients is complex, due to various medical complications arising, leading to extended hospital stays that are estimated to cost healthcare providers approximately £1.7 billion per year. Adult stem cells are present throughout the body where they play important roles to regenerate damaged tissues. Much research has proposed that a few adult stem cells can be removed from the body, their numbers expanded within a laboratory and then transplanted back into the body to aid the regeneration of a range of different tissues. However, little research has progressed into regular therapies due to issues surrounding the poor survival and unpredictable responses of the transplanted cells. Research also proposes that stem cells placed at wound sites synthesise and release biological factors that are able to stimulate repair processes. Dental stem cells can be collected from the soft pulp tissue located within the centre of all teeth, including milk teeth, as they are naturally lost, or wisdom teeth, extracted due to surgical need; thus essentially representing clinical waste material. Our own research has identified that these dental stem cells produce very small spherical vesicles (we call Dental EVs) that contain a biologically active cargo. We have collected these Dental EVs within laboratory conditions, and added them to fresh stem cells which has led these cells to make bone tissue. We propose that Dental EVs can be used to restore poor bone healing apparent in the above described age-related conditions. This proposal lends itself to a new and exciting area of research, as Dental EVs can potentially be produced with a consistent and defined cargo that can be optimised and safely developed to give a predictable clinical outcome. The research is timely since dental stem cells are now being stored in cell banks, where they are described as “young” cells that may be used in the treatment of a range of age-related diseases. The use of Dental EVs to speed up recovery of bone healing for osteoporotic and diabetic patients may thus be one example for their potential use.

Research activity codes: 5.2 CELLULAR AND GENE THERAPIES
Health categories: MUSCULOSKELETAL