Androgenic Steroids Induce Pathologic Scarring in a Preclinical Swine Model Via Dysfunctional Extracellular Matrix Deposition

Abstract Background Hypertrophic scarring is a major source of morbidity for surgery patients. Sex hormones are not classically considered to be modulators of scarring. However, based on clinical observations of increased frequency of hypertrophic scarring in patients on testosterone, we hypothesized that androgenic steroids induce abnormal scarring and developed a preclinical swine model to explore these effects. Methods A total of six male (XY) and female (XX) mini-swine underwent castration and were randomly assigned to no testosterone (noT) or biweekly testosterone therapy (+T). Ten dorsal excisional wounds were created on each pig. To mimic a chronic wound, a subset of wounds were re-excised at two weeks. Scars (POD42) and chronic wounds (POD28) were harvested six weeks after initial wounding for analysis via histology, RNA-seq, and mechanical testing. Results Histologic analysis of POD42 scars from +T swine showed increased mean fibrosis area (16mm 2 noT, 28mm 2 +T; p=0.007) and thickness (0.246mm 2 noT, 0.406mm 2 +T; p<0.001) compared to noT swine. Scars in XX+T and XY+T pigs had greater tensile burst strength (p=0.024 and p=0.013 respectively) compared to scars in noT swine. Color deconvolution analysis showed greater deposition of type I and type III collagen as well as increased type I to type III collagen ratio in +T scars. Dermatopathologist scores of POD42 scars show +T exposure was associated with worse overall scarring scores compared to controls (p<0.05). On RNAseq, gene ontology analysis showed testosterone exposure was associated with significant upregulation of cellular metabolism and immune response gene sets. Pathway analysis showed testosterone upregulated Reactome pathways related to keratinization and formation of collagen and laminin. Conclusion We developed a novel preclinical porcine model to study the effects of the sex hormone testosterone on scarring. Testosterone induces early proliferation of excessive granulation tissue, which eventually leads to increased scar tissue. T also appears to increase the physical strength of scars via supraphysiologic deposition of collagen and other ECM factors. The increase in burst strength observed for both XX and XY suggests that hormonal administration has a stronger influence on mechanical properties than chromosomal sex. Antiandrogen topical therapies may be a promising future area of research.