Milk-Derived Extracellular Vesicles Protect Bovine Oviduct Epithelial Cells from Oxidative Stress

Extracellular vesicles (EVs) are promising therapeutic agents due to their role in intercellular communication. This study examined the protective effects of milk-derived EVs (mEVs) on bovine oviductal epithelial cells (BOECs) under cobalt chloride (CoCl₂)-induced oxidative stress (OS), comparing EVs stored at −80 °C or lyophilized. mEVs and algae-derived EVs (aEVs; negative control) were isolated via tangential flow filtration and applied at 10⁷, 10⁹, and 10¹¹ particles/mL in three treatment strategies: pre-treatment, co-incubation, and post-treatment. mEVs specifically enhanced cell viability in all protocols except for post-treatment, where only 10⁷ particles/mL was effective; meanwhile, storage method did not affect EV activity. Enzyme digestion suggested that internal EV cargos are potentially the dominant contributors to the protective response compared to surface-associated molecules. mEVs reduced the expression of the OS markers DDIT4 and HIF1A while promoting cell migration more effectively than aEVs. Pathway enrichment analysis of previously reported mEV miRNAs indicated regulation of cytokine production and glucocorticoid responses, potentially contributing to OS defense. mEV protein cargo analysis showed pathways primarily linked to peptidase and vesicle-related functions, suggesting that protein cargo may also contribute to the observed protective effects. Overall, mEVs protect BOECs against CoCl₂-induced OS and maintain bioactivity after lyophilization.