Overexpression of USP35 enhances the protective effect of hUC-MSCs and their extracellular vesicles in oxygen-glucose deprivation/reperfusion-induced SH-SY5Y cells via stabilizing FUNDC1.

Ischemia-reperfusion (IR) injury is associated with neurological disorders such as stroke. The therapeutic potential of human umbilical cord mesenchymal stem cells (hUC-MSCs) and their secreted extracellular vesicles (EVs) in alleviating IR injury across various cell types including neuronal cells has been documented. However, the underlying mechanisms through which hUC-MSCs and hUC-MSC-EVs protect neuronal cells from IR-triggered damage are not well understood. In this study, we co-cultured SH-SY5Y neuroblastoma cells with hUC-MSCs or hUC-MSC-EVs and subjected them to oxygen-glucose deprivation/reperfusion (OGD/R) treatment. Our findings indicate that both hUC-MSCs and hUC-MSC-EVs significantly improved viability, reduced apoptosis, promoted autophagy of OGD/R-induced SH-SY5Y cells, and decreased mitochondrial reactive oxygen species levels within them. Furthermore, the neuroprotective effect of hUC-MSCs and hUC-MSC-EVs in OGD/R-induced SH-SY5Y cells was enhanced by overexpressing USP35, a deubiquitinase. Mechanistically, USP35 interacted with and stabilized FUNDC1, a positive regulator of mitochondrial metabolism. Knockdown of FUNDC1 in USP35-overexpressing hUC-MSCs and their secreted EVs eliminated the augmented neuroprotective function induced by excess USP35. In conclusion, these findings underscore the crucial role of USP35 in enhancing the neuroprotective function of hUC-MSCs and their secreted EVs, achieved through the stabilization of FUNDC1 in OGD/R-induced SH-SY5Y cells.