Mechanisms of Estrogen Induced Skeletal Muscle Fibrosis in Inguinal Herniation

Abstract

Background: Abdominal wall fibrosis weakens these muscles, often resulting in inguinal hernias. Despite its high prevalence and public health burden, the etiology or exploration of non-surgical treatments for muscle fibrosis remains a vastly under-explored area. We developed a mouse model (humanized aromatase mouse – Aromhum ) wherein all male mice develop scrotal hernias at puberty. The lower abdominal muscle (LAM) in these mice produces local estradiol (E2), which acts on stromal fibroblasts to proliferate, leading to muscle fibrosis, atrophy, and hernias. We are using this novel model to uncover mechanisms of muscle fibrosis. Objectives & Hypothesis: The study was to understand the mechanisms of E2-induced muscle fibrosis in scrotal hernias. We hypothesized that manipulating of E2-ERα signaling inhibits or reverses hernia formation by reducing or eliminating LAM fibrosis. Methods: Mice were administered E2-ERα antagonist treatment via Fulvestrant slow-release pellets (0.15mg/kg, 90 days) either prior to or post large hernia development. Hernia sizes were measured weekly, and LAM tissues were harvested for immunohistochemistry analysis.For in vitro experiments, fibroblasts were isolated from herniated LAM tissues and cultured under estrogen-replete (+10nM E2) and deplete (+ 100nM Fulvestrant) conditions. The cells were subsequently processed for ChIP-seq, ATAC-seq, and RNA-seq analysis. Sample size: 10-15 mice/group in 3 technical replicates Results: In vivo: Administration of fulvestrant to mice completely reversed scrotal herniation within 4-5 weeks of treatment (n = 10-15/group, p < 0.0001). In addition, the LAM tissues showed a reversal of fibrosis and a concurrent increase in myofiber cross-sectional area (n = 10-15/group, p < 0.0001) compared to placebo-treated mice. In vitro: Overall, 853 differentially expressed genes were observed between E2 and E2+Fulvestrant treated fibroblasts. Genes associated with the extracellular matrix, WNT signaling, TGFβ, and focal adhesions were enriched in our study. Further, transcription factors like Pbx1, Elk1, and Yy1 were also enriched in ERα cistrome. Integrating the three datasets, we identified 58 core genes that play a crucial role in E2-associated muscle fibrosis. Conclusions: We believe that this is the first skeletal fibrosis model that shows reversibility by inhibiting E2-ERα signaling. We provide mechanistic insight into this process by identifying the genetic, epigenetic, and transcriptomic changes associated with fibrosis in skeletal muscle upon stimulation by E2. These genes and pathways pave the way for potential therapeutic targets for the treatment of hernias and other skeletal muscular disorders. NIH R01 DK121529 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.