A Novel Protocol to Reconstruct the Three-Dimensional Architecture of the Periurethral Space Following Surgical Simulation of the Mid-Urethral Sling Procedure (2021)

Background 
The mid-urethral sling (MUS) surgery aims to prevent urinary leakage in female stress urinary incontinence patients (Szell et al., 2017). However, the MUS transects the female periurethral tissue (FPT), a highly innervated and vascularized space, potentially leading to female sexual dysfunction post-operatively (Clohosey et al., 2018; Szell et al., 2017). 
Yet, there is a paucity of anatomical information relevant to the FPT and how this surgery may impact these structures. Unlike two-dimensional (2D) imaging, three-dimensional (3D) reconstruction following surgical simulation can inform on the spatial relationships and patterns of neurovascular supply. A review of the current literature suggests that there is no standard protocol to study the 3D histology of the adult female pelvis and the FPT post-operatively. 
Methods 
The main objective of the current investigation is to conduct an extensive literature review to develop a suited protocol for the 3D reconstruction of this tissue. An extensive literature search was conducted to evaluate recent (from 2015 to now) 3D reconstruction studies of the female pelvis and female periurethral tissue. 
Results & Discussion 
The tissue staining was found to be central in the 3D reconstruction protocol. Immunohistochemistry (IHC) was most often performed prior to image digitalization and computer-based 3D reconstruction. Chromogenic and multiplexing chromogenic IHC (mIHC), among other immunostaining methods, were reported in the literature, demonstrating the heterogeneity in the staining methods currently used. Additionally, studies often reported the use of chromogens carrying different absorbance spectra. Translucent DISCOVERY is the only chromogen with a narrow absorbance spectrum permitting colocalization by generating a third color in overlapping signals (Ilie et al., 2018). Adequate staining optimizes the signal to noise ratio, thereby avoiding excessive background noise. The signal represents the detection of the antigens of interest, while the noise represents unwanted staining (Bond and Kinnamon, 2013). 
Mass spectrometry imaging (MSI) protocols with desorption electrospray ionization (DESI) (DESI-MSI) 3D chemical images convey information about the chemical distributions and spatial relationships of structures in highly innervated and vascularized tissues (Leon et al., 2019). DESI does not require excessive tissue processing and hence may be applied prior to staining (Ifa, Wu, Ouyang, & Cooks, 2010). Based on a thorough review of the literature, it is believed that DESI-MSI can potentially be used to confirm or infirm IHC results in 3D reconstruction of the FPT after MUS surgical simulation. 
Conclusion & Future Directions 
Our future objectives are to (1) determine whether the DISCOVERY translucent chromogenic mIHC staining method provides direct colocalization of antibodies in female periurethral tissue (FPT) and has superior visualization of innervated structures in comparison to standard IHC, and (2) to determine whether DESI is a feasible method to confirm IHC results which identify the spatial arrangement of structures. A standard 3D reconstruction protocol for the FPT will allow reproducibility in a research setting and will be of particular interest to pathologists and urogynecologists. 
  
References: 
Bond, A., & Kinnamon, J. C. (2013). Microwave processing of gustatory tissues for immunohistochemistry. Journal of neuroscience methods, 215(1), 132–138.https://doi.org/10.1016/j.jneumeth.2013.02.014 
Clohosey, D., Gaudet, D., Goldstein, S., Komisaruk, B., Szell, N., Hannan, J., . . . Adams, M. (2018). 009 Histological Characterization of Periurethral Tissue: Potential Role in Sexual Function. The Journal of Sexual Medicine, 15(2). doi:10.1016/j.jsxm.2017.11.028 
Ifa, D. R., Wu, C., Ouyang, Z., & Cooks, R. G. (2010). Desorption electrospray ionization and other ambient ionization methods: Current progress and preview. The Analyst, 135(4), 669. doi:10.1039/b925257f 
Ilie, M., Beaulande, M., Hadj, S. B., Chamorey, E., Schiappa, R., Long-Mira, E., . . . Hofman, P. (2018). Chromogenic Multiplex Immunohistochemistry Reveals Modulation of the Immune Microenvironment Associated with Survival in Elderly Patients with Lung Adenocarcinoma. Cancers, 10(9), 326. doi:10.3390/cancers10090326 
Leon, M., Ferreira, C. R., Eberlin, L. S., Jarmusch, A. K., Pirro, V., Rodrigues, A. C. B., Favaron, P. O., Miglino, M. A., & Cooks, R. G. (2019). Metabolites and Lipids Associated with Fetal Swine Anatomy via Desorption Electrospray Ionization – Mass Spectrometry Imaging. Scientific Reports, 9(1), 3–6. https://doi.org/10.1038/s41598-019-43698-2  
Szell, N., Komisaruk, B., Goldstein, S. W., Qu, X. (., Shaw, M., & Goldstein, I. (2017). A Meta-Analysis Detailing Overall Sexual Function and Orgasmic Function in Women UndergoingMidurethral Sling Surgery for Stress Incontinence. Sexual Medicine, 5(2).doi:10.1016/j.esxm.2016.12.001