Mesenchymal vs. epithelial extracellular vesicles in corneal epithelial repair, apoptosis, and immunomodulation: An...

Corneal injuries often lead to epithelial damage, apoptosis, and inflammation which impact visual function. Effective epithelial healing is critical for optimal vision and functioning of the cornea. Mesenchymal stem/stromal cells (MSCs)-derived extracellular vesicles (EVs) present promising avenues for cell-free therapy, however, evaluation of their specific roles in corneal epithelial injury requires further investigations with due consideration to the endogenous human corneal epithelial cell-derived EVs (HCEC-EVs). This study aims to isolate and characterize the EVs from a commonly available human corneal epithelial cell line (HCE-2 [50. B1], ATCC) and evaluate their corneal epithelial repair, anti-apoptotic, and immunomodulatory potential in comparison with human bone marrow mesenchymal stem cell-derived EVs (BM-MSC-EVs) in vitro. Both the BM-MSC- and HCEC-EVs exhibited similar morphology with a diameter <150 nm. However, the yield of EVs from HCECs was higher than that of BM-MSCs. Nanoparticle tracking analysis revealed an average EV size of ∼120 nm, while western blotting confirmed the presence of CD63, CD81, and TSG101, whereas Calnexin could not be detected in the BM-MSC- and HCEC-EVs. The corneal epithelial repair was monitored through in vitro wound healing assay, whereas apoptosis was studied through flow cytometry-based Propidium iodide staining in H₂O₂-treated cells. IL-1β-stimulated HCECs were treated with BM-MSC- and HCEC-EVs for 24 h and expression of pro- (IL-6 and TNF-α) and anti-inflammatory (IL-10 and TGF-β) cytokines was evaluated through ELISA. Our results, limited to in vitro investigations, suggest that compared with HCEC-EVs, BM-MSC-EVs showed: i) accelerated corneal epithelial healing, ii) enhanced anti-apoptotic potential, and iii) improved anti-inflammatory properties, in cultured HCECs.