Stage-Related Changes in TGF-β Isoforms in PBMC Culture Supernatants in Endometriosis: A Prospective Case–Control Study

Endometriosis is a chronic inflammatory disease in which transforming growth factor-beta (TGF-β) has been implicated in immune dysregulation, extracellular matrix remodeling, and fibrosis. Data on baseline secretion of TGF-β isoforms by systemic immune cells remain limited. This pilot study quantified unstimulated secretion of TGF-β1, TGF-β2, and TGF-β3 by peripheral blood mononuclear cell (PBMC) cultures from women with and without endometriosis and explored stage-related patterns. In this prospective case–control study, PBMCs from 50 women with surgically confirmed endometriosis and 30 controls were cultured for 24 h without exogenous stimulation. Supernatant concentrations were measured using a multiplex bead-based immunoassay (Bio-Plex, Bio-Rad) and expressed as pg/mL; between-group and stage-related differences were assessed using non-parametric tests. Median 24 h secretion was similar between groups (TGF-β1: 103,816 vs. 114,700 pg/mL, p = 0.25; TGF-β2: 3735 vs. 3732 pg/mL, p = 0.32; TGF-β3: 3280 vs. 3284 pg/mL, p = 0.70). Within the endometriosis cohort, TGF-β2 was significantly higher in moderate/advanced disease (rASRM stages III–IV) than in minimal/mild disease (stages I–II), whereas TGF-β1 and TGF-β3 did not reach statistical significance for a stage-dependent pattern in this pilot cohort (p = 0.42 and p = 0.41, respectively; Kruskal–Wallis), and a type II error cannot be excluded given the small sample size per rASRM (revised American Society of Reproductive Medicine)stage (n = 11–14). These findings suggest that TGF-β dysregulation is compartmentalized to the peritoneal environment rather than systemically imprinted in circulating immune cells. The stage-dependent elevation of TGF-β2 supports its role in progressive fibrogenesis and as a candidate severity biomarker, warranting confirmation in larger, stimulus-augmented studies.