Lymphomonocytic Extracellular Vesicles Influence Fibroblast Proliferation and Collagen Production in Systemic Sclerosis.

Systemic sclerosis (SSc) is a chronic autoimmune disorder characterized by fibrosis, immune dysregulation, and vascular abnormalities. Extracellular vesicles (EVs), secreted by immune cells, have been implicated in modulating fibroblast activity and are actively involved in SSc pathogenesis. This study aims to determine whether lymphomonocytic-derived EVs influence fibroblast proliferation and collagen synthesis in SSc. Fibroblasts from healthy donors (HDFs) and SSc patients (SScHDFs) were exposed to EVs derived from Jurkat and U937 cell lines stimulated under pro-inflammatory conditions using tumor necrosis factor-α (TNFα) or phorbol 12-myristate 13-acetate + ionomycin (PMA + IONO). Proliferation was assessed using CCK-8 assays, while collagen production was quantified via ELISA. Our findings demonstrate that EVs derived from PMA + IONO-stimulated Jurkat and U937 cells significantly reduced fibroblast proliferation in a dose-dependent manner. Notably, SScHDFs exhibited lower baseline proliferation and a diminished overall response to EV treatment. Collagen production was markedly reduced in both fibroblast types following exposure to PMA + IONO-stimulated EVs, whereas TNFα-stimulated EVs affected only HDFs. These findings suggest that EVs from activated immune cells modulate fibroblast function in SSc, potentially contributing to disease pathogenesis. Further research is warranted to elucidate the molecular mechanisms underlying these effects and to explore the therapeutic potential of targeting EV-mediated signaling in SSc.