12565 Expression Of Sex Hormone Receptors In Levator Ani Muscle Tissue From Patients With Pelvic Organ Prolapse

Abstract Disclosure: T. You: None. A. Halle: None. W. Xu: None. T. Potluri: None. H. Nguyen: None. S.E. Bulun: None. J. Julia Geynisman-Tan: None. H. Zhao: None. Introduction: Women with pelvic floor disorders usually have weakened pelvic floor muscles, which may cause urinary incontinence, fecal incontinence, and pelvic organ prolapse (POP). Histologically, the pelvic floor musculature in POP patients displays increased fibrosis and muscle atrophy. However, the underlying molecular mechanism for POP has not been fully investigated. We and others found that estrogen causes pelvic skeletal muscle fibrosis and inguinal hernias in male animal models. Additionally, clinical trials from the Women's Health Initiative showed women receiving estrogen-only or estrogen plus progestin treatment had statistically significant increases in the risk for urinary incontinence. However, the role of estrogen, progesterone, androgen, and their receptor expression in pelvic floor muscle is not well studied. Methods: TruCut biopsy needles were used to obtain levator ani (LA, the major pelvic floor muscle) biopsies from four groups of patients undergoing surgery: (i) 5 premenopausal women with stage II/III POP (age 38-52 years), (ii) 5 postmenopausal women with stage III POP (59-75 years), (iii) 5 age and parity matched premenopausal controls, and (iv) 5 age and parity matched postmenopausal controls. The control patients did not have any POP (stage 0) or only had sole stress urinary incontinence. H&E staining, Masson’s trichrome staining, and immunohistochemistry (IHC) staining for estrogen receptor α (ERα), progesterone receptor (PGR), and androgen receptor (AR) were performed in LA muscle tissue. Standard patient demographics (age, parity, and diagnosis) were collected. Results: We used H&E staining to morphologically assess stromal cells and myofibers obtained from LA muscle biopsies. Masson’s trichrome staining showed extracellular matrix deposition in the LA muscle from women with or without POP. In addition, we found ERα was present in the stromal cells from nearly every LA biopsy using IHC staining. ERα expression (H-Score) was similar in four groups of patients. ERα IHC staining was absent in LA myofibers. AR was highly expressed in stromal cells in all LA muscles and weakly expressed in myofibers in ∼70% of LA tissues. AR expression (H-Score) was significantly decreased in postmenopausal women with stage III pelvic organ prolapse. PGR was only expressed in a small portion of the LA sample (30%), with PGR exclusively expressed in the stroma of the LA muscle. Conclusion: Our findings indicate that sex hormone receptors (ERα, AR, and PGR) are present in LA muscle stroma, providing the foundation to further define the roles of sex steroid hormones in pelvic organ prolapse. Presentation: 6/3/2024