Differential Expression of Fibrosis-Related Genes in Intrauterine Adhesions and Cesarean Scar Defects: A Cohort Study

Objectives: This study aimed to characterize the expression patterns and interrelationship of key fibrosis-related markers-TGF-β1, SMAD2, SMAD3, and fibronectin-in human endometrial tissue, and to explore their potential diagnostic relevance in differentiating intrauterine adhesions (IUAs) from cesarean scar defects (isthmocele), with a particular focus on underlying fibrotic remodeling processes. Methods: Endometrial samples were obtained from women diagnosed with IUAs, isthmocele, or without uterine pathology. Total RNA was extracted from all specimens, and gene expression levels were quantified using real-time quantitative polymerase chain reaction (PCR). Statistical analyses included intergroup comparisons, parametric and non-parametric correlation analysis, multivariable linear and logistic regression models, and receiver operating characteristic (ROC) curve analysis to explore the discriminatory potential of the evaluated markers. Results: Significant positive correlations were observed across the study population between SMAD2 and SMAD3 (r = 0.892; p = 0.001), SMAD2 and TGF-β1 (r = 0.697; p = 0.001), and SMAD3 and TGF-β1 (r = 0.910; p = 0.001), indicating coordinated activation of profibrotic signaling pathways. ROC curve analysis showed high discriminatory performance for isthmocele across all evaluated markers, with area under the curve (AUC) values of 0.976 for SMAD3, 0.961 for TGF-β1, 0.913 for fibronectin, and 0.928 for SMAD2 (all p = 0.001). In contrast, although elevated expression levels of fibrotic markers were observed across different American Fertility Society (AFS) stages in IUAs, these differences did not reach statistical significance. Conclusions: This study provides molecular evidence distinguishing isthmocele from IUAs with respect to fibrosis-related signaling in human endometrial tissue. The markedly elevated and coordinated expression of TGF-β1, SMAD2, SMAD3, and fibronectin in isthmocele reflects activation of post-cesarean fibrotic remodeling pathways. However, given the limited sample size and the exploratory nature of the analyses, larger cohorts and future studies are required to validate these findings and to allow extrapolation of the results to the general population. At this stage, these biomarkers should therefore be regarded as indicators of underlying pathophysiological processes.