17. Mechanical Offloading Prevents and Rescues Microtrauma Induced Fibrosis in Large Animal Model

Abstract

PURPOSE: Repetitive subdermal injections, as seen with insulin in diabetes mellitus, cause microtrauma leading to skin fibrosis and consequential pain. We hypothesized that microtrauma induced fibrosis could be attenuated by injecting through a mechanical offloading dressing (MOD). We developed a large animal porcine model to evaluate injection associated fibrosis. METHODS: Two, Red-Duroc (3-month-old) pigs were subjected to four treatment conditions over a 16-week period, in two 8-week phases. All conditions received daily bleomycin injections in Phase 1 to induce microtrauma induced fibrosis. Group 1 (NN) received no MOD. Group 2 (EE) received the MOD through Phases 1, 2. Group 3 (EN) received the MOD in Phase 1 only. Lastly group 4 (NE) received the MOD in Phase 2 only. Biopsies from each group, with their respective adjacent unwounded skin (UW), were acquired at the 16-week timepoint for both histology and transcriptional analysis using single-cell-RNA sequencing. RESULTS: Skin histology by H&E and Masson trichome demonstrated that EE-treated skin significantly reduced dermal thickness and restored hair follicle formation (*p<0.05). Picrosirius red staining confirmed that EE-treatment resembled the architecture of unwounded skin (*p<0.05). Mechanical testing of EE, EN, and NE treated skin exhibited significantly decreased stiffness compared to NN skin (*p<0.05). Finally, skin deformation, was significantly greater for EE, EN, and NE treated skin (*p<0.05). scRNA-seq analysis identified specific profibrotic notch pathways responsible for fibrosis in NN treated skin, which were downregulated following MOD application. CONCLUSION: To date there is no effective treatment to prevent injection induced fibrosis, which is a huge clinical problem in diseases such as diabetes. This pig study demonstrates for the first time that mechanical offloading may prevent and treat microtrauma induced fibrosis.