In Vivo Rectal Mucosal Barrier Function Imaging in a Large-Animal Model by Using Confocal Endomicroscopy: Implications for Injury Assessment and Use in HIV Prevention Studies

Abstract

Injury occurring on the surface of the rectal mucosal lining that causes defects in barrier function may result in increased risk for transmission of infection by HIV and other pathogens. Such injury could occur from microbicidal or other topical agents, mechanical trauma during consensual or nonconsensual intercourse, or inflammatory conditions. Tools for evaluation of rectal mucosal barrier function for assessing the mucosa under these conditions are lacking, particularly those that can provide in vivo structural and functional barrier integrity assessment and are adaptable to longitudinal imaging. We investigated confocal endomicroscopy (CE) as a means for in vivo imaging of the rectal epithelial barrier in the ovine model following spatially confined injury to the surface at a controlled site using a topical application of the microbicide test agent benzalkonium chloride. Topical and intravenous (i.v.) fluorescent probes were used with CE to provide subcellular resolution imaging of the mucosal surface and assessment of barrier function loss. A 3-point CE grading system based on cellular structure integrity and leakage of dye through the mucosa showed significant differences in score between untreated (1.19 ؎ 0.53) and treated (2.55 ؎ 0.75) tissue (P < 0.0001). Histological grading confirmed findings of barrier compromise. The results indicate that CE is an effective means for detecting epithelial injury and barrier loss following localized trauma in a large-animal model. CE is promising for real-time rectal mucosal evaluation after injury or trauma or topical application of emerging biomedical prevention strategies designed to combat HIV.

Characterization of the Ovine Vaginal Microbiome and Inflammation Patterns as an Improved Testing Model of Human Vaginal Irritation

“…Further, the suitability of sheep as a large animal model for evaluation and testing of the performance of human size intravaginal devices including vaginal rings for sustained delivery of emerging non-vaccine biological preventatives, (e.g. tenofovir), as well as application of several OTC and experimental compounds is indicated by recent reports (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). Finally, in addition to standard histopathology of tissues after euthanasia, there are now refined repeated measure methods for ovine vaginal irritation inspection, namely, optical coherence tomography (OCT), colposcopy, and tissue sampling by repeat biopsy.…”

Fluorescence In Vivo Endomicroscopy Part 2: Applications of High-Resolution, 3-Dimensional Confocal Laser Endomicroscopy

“…Barrier function studies. Vargas reported a lack of tools for evaluation of rectal mucosal barrier function and explored FIVE for assessing in vivo structural and functional barrier integrity [43]. Topical and i.v.…”