miR-18a-5p shuttled by mesenchymal stem cell-derived extracellular vesicles alleviates early brain injury following subarachnoid hemorrhage through blockade of the ENC1/p62 axis.

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have therapeutic potential in various diseases due to their capacity to transfer bioactive cargoes such as microRNAs (miRNAs or miRs) to recipient cells. The present study isolated EVs from rat MSCs and aimed to delineate their functions and molecular mechanisms in early brain injury following subarachnoid hemorrhage (SAH). We initially determined the expression of miR-18a-5p and ENC1 in hypoxia/reoxygenation (H/R)-induced brain cortical neurons and rat models of SAH induced by the endovascular perforation method. Accordingly, increased ENC1 and decreased miR-18a-5p were detected in H/R-induced brain cortical neurons and SAH rats. After MSC-EVs were co-cultured with cortical neurons, the effects of miR-18a-5p on neuron damage, inflammatory response, endoplasmic reticulum (ER) stress, and oxidative stress markers were evaluated based on ectopic expression and depletion experiments. miR-18a-5p overexpression in brain cortical neurons co-cultured with MSC-EVs was shown to impede neuron apoptosis, ER stress and oxidative stress while augmenting neuron viability. Mechanistically, miR-18a-5p bound to the 3'UTR of ENC1 and reduced its expression, weakening the interaction between ENC1 and p62. Through this mechanism, transfer of miR-18a-5p by MSC-EVs contributed to the eventual inhibition of early brain injury and neurological impairment following SAH. Overall, miR-18a-5p/ENC1/p62 may be a possible mechanism underlying the cerebral protective effects of MSC-EVs against early brain injury following SAH.