Th1 and Th2 cells in equine endometrosis and their interactions with endometrial fibroblasts

Mare endometrosis is a chronic degenerative condition of the endometrium, primarily characterized by fibrosis, involving interactions among fibroblasts, immune cells, and epithelial cells regulated by cytokines and growth factors. T helper (Th)1 and Th2 cells seem to play a pivotal role in fibrosis. However, their roles in equine endometrial fibrosis remain unknown. This study explores Th1 and Th2 cell distribution across different stages of endometrium histopathological Kenney and Doig categories; and evaluated their secretome effects on non-fibrotic endometrium derived fibroblast functional characteristics, extracellular matrix (ECM)-associated mRNA transcription, and transcriptomic profiles. Th1 and Th2 cells, along with cytokines (IFN-γ, IL-4, IL-13) and their receptors, were present in mare endometria at all endometrium stages. Th1 secretome influenced genes enriched in metabolism, cell cycle, and ECM-related pathways, while Th2 secretome regulated genes enriched in tissue remodeling and signaling pathways, suggesting their role in the development of fibrosis in the endometrosis progression.