SHC1 affects oestrogen-driven differentiation and barrier function of vaginal epithelial cells via EGFR/Ras/ERK pathway.

BACKGROUND

Vaginal atrophy (VA), a common condition associated with oestrogen deficiency, significantly impacts women's quality of life. Src homology 2 domain-containing transforming protein 1 (SHC1) is implicated in various hormone-dependent processes. This project aims to investigate whether oestrogen promotes the proliferation, migration and differentiation of vaginal epithelial cells by regulating SHC1, and delineates the underlying mechanism.

METHODS

An ovariectomised (OVX) mouse model of VA was established and treated with 17β-estradiol (E2). Human vaginal epithelial VK2/E6E7 cells were stimulated with E2 (dose-dependent), transfected with SHC1 overexpression (OE-SHC1), SHC1 knockdown (sh-SHC1) or epidermal growth factor receptor (EGFR) overexpression (OE-EGFR) plasmids. Histological and immunohistochemical analyses were performed on vaginal tissues. Cellular proliferation and migration were assessed via CCK-8 and wound healing assays, respectively. Western blot analysed cellular/tissue proteins (differentiation/barrier markers, Ras/ERK pathway components).

RESULTS

E2 upregulated SHC1 expression both in atrophic vaginal tissue and in VK2/E6E7 cells in a dose-dependent manner. SHC1 overexpression enhanced, while its knockdown attenuated, E2-induced cell proliferation, migration, and the expression of differentiation (Keratin 6a (krt6a), Keratin 13 (krt13)) and barrier (E-cadherin, occludin) markers. Mechanistically, SHC1 mediated the effects of E2 by acting as an adaptor of EGFR and subsequent activation of the downstream Ras/ERK pathway. EGFR overexpression rescued SHC1 deficiency phenotypes in E2-treated VK2/E6E7 cells. In OVX mice, SHC1 knockdown reversed E2-mediated restoration of vaginal epithelial architecture, proliferation (Ki67) and Ras/ERK signalling.

CONCLUSIONS

SHC1 is a critical mediator of E2-induced vaginal epithelial homeostasis through the EGFR/Ras/ERK axis, representing a potential downstream therapeutic target for intervention in VA, particularly via localised delivery strategies.