Cellular and extracellular vaginal changes following murine ovarian removal.

Loss of estrogen as a result of aging, pelvic cancer therapy, genetics, or eating disorders affects numerous body systems including the reproductive tract. Specifically, a chronic hypoestrogenic state fosters debilitating vaginal symptoms like atrophy, dryness, and dyspareunia. Current treatment options, including vaginal estrogen and hyaluronan (HA), anecdotally improve symptoms, but rectifying mechanisms are largely understudied. In order to study the hypoestrogenic vaginal environment, in particular the extracellular matrix (ECM), as well as understand the mechanisms behind current treatments and develop new therapies, we characterized a reliable and reproducible animal model. Bilateral ovariectomies (OVX) were performed on 9-week-old CD1 mice. After 1 month of estrogen loss due to ovarian removal, a phenotype that is similar to human vaginal tissue in an estrogen reduced state was noted in mice compared to sham-operated controls. The uterine to body weight ratio decreased by 80% and vaginal epithelium was significantly thinner in OVX compared to sham mice. Estrogen signaling was altered in OVX, but submucosal ERα localization did not reach statistical differences. HA localization in the submucosal area was altered and CD44 expression decreased in OVX mice. Collagen turn-over was altered following OVX. The inflammation profile was also disrupted, and submucosal vaginal CD45+ and F4/80+ cell populations were significantly reduced in the OVX mice. These results show altered cellular and molecular changes due to reduced estrogen levels. Developing new treatments for hypoestrogenic vaginal symptoms rely on better understanding of not only the cellular changes, but also the altered vaginal ECM environment. Further studies using this mouse model has the potential to advance women's vaginal health treatments and aid in understanding the interplay between organ systems in both healthy, aged, and diseased states.

An Avant-Garde Model of Injury-Induced Regenerative Vaginal Wound Healing.

Objective: To design and validate a novel murine model of full-thickness (FT) vaginal wound healing that mirrors postinjury tissue repair and underscores the impact of estrogen signaling-driven healing kinetics, inflammation, and neovascularization. Approach: Five-week-old female CD1 mice were subjected to two 1-mm FT wounds. To assess wound healing kinetics, vaginas were harvested at 6, 12, 18, 24, 48, and 72 h and 7 days postinjury. Wounds from all time points were analyzed by hematoxylin and eosin and trichrome to, respectively, assess the rate of wound closure and tissue deposition. Inflammatory leukocyte (CD45), neutrophil (Ly6G), and macrophage (F480 and CD206) infiltration was examined by immunohistochemistry (IHC) and the resulting anti-inflammatory M2 (CD206)/total (F480) macrophage ratio quantified. Neovascularization (CD31) and estrogen receptor-α (ERα) expression levels were similarly determined by IHC. Results: We observed rapid healing with resolution of mucosal integrity by 48 h (p < 0.05), and overall neutrophils and polarized type 2 macrophages (M2) apexed at 12 h and reduced to near control levels by day 7 postinjury. Tissue repair was virtually indistinguishable from the surrounding vagina. CD31+ vessels increased between 12 h and day 7 and ERα trended to decrease at 12 h postinjury and rebound at day 7 to uninjured levels. Innovation: A proof-of-concept murine model to study vaginal wound healing kinetics and postinjury regenerative repair in the vagina was developed and verified. Conclusion: We surmise that murine vaginal mucosal repair is accelerated and potentially regulated by estrogen signaling through the ERα, thus providing a cellular and molecular foundation to understand vaginal healing responses to injury.