Endometriotic follicular fluid modulates granulosa cell phenotype and gap-junction signaling in vitro

Endometriosis-associated infertility is a multifactorial condition characterized by inflammatory, endocrine, and follicular microenvironment alterations that impair oocyte quality and reproductive efficiency. In particular, follicular fluid (FF) from women with endometriosis exhibits an altered biochemical composition that can modulate granulosa cell (GC) function, which is essential for oocyte growth, maturation, and metabolic support. This study investigated the effects of pathological FF on GC behavior using an in vitro cross-exposure experimental model. Sixty-eight women undergoing assisted reproductive technology (ART) procedures were enrolled and divided into a male-factor infertility group (MF, n = 30) and an endometriosis-associated infertility group (ENDO, n = 38). GCs isolated from both groups were cultured in the presence of FF-MF and FF-ENDO to evaluate proliferation, morphological remodeling, apoptosis, Connexin-43 (Cx43) and follicle-stimulating hormone receptor (FSHR) expression, and endocrine and inflammatory secretory profiles. Exposure to FF-ENDO induced marked phenotypic changes in GCs, promoting fibroblast-like and muscle-like morphologies associated with altered follicular function. Pathological FF also modulated Cx43 and FSHR expression, suggesting dysregulation of gap-junction communication and protein localization. In parallel, alterations in hormonal and cytokine secretion profiles indicated inflammatory activation and impaired steroidogenic activity. Overall, these findings support the hypothesis that the endometriotic follicular microenvironment directly contributes to GC dysfunction and reduced oocyte competence. This study provides further insight into the cellular mechanisms underlying endometriosis-associated infertility and may contribute to the development of targeted strategies aimed at improving ART outcomes.