Mesenchymal stem cells (MSCs) exert their therapeutic capability through a variety of bioactive substances, including trophic factors, microRNAs, and extracellular vesicles (EVs) in infarcted tissues. We therefore hypothesized that MSC-derived EVs (MSC-EVs) possess therapeutic molecules similar to MSCs. Moreover, given their nature as nanosized and lipid-shielded particles, the intravenous infusion of MSC-EVs would be advantageous over MSCs as a safer therapeutic approach. In this study, we investigated the biodistribution, therapeutic efficacy, and mode of action of MSC-EVs in a rat stroke model. MSC-EVs successfully stimulated neurogenesis and angiogenesis in vivo. When compared to the MSC-treated group, rats treated with MSC-EVs exhibited greater behavioral improvements than the control group (p < 0.05). Our biodistribution study using fluorescence-labeled MSC-EVs and MSCs demonstrated that the amounts of MSC-EVs in the infarcted hemisphere increased in a dose-dependent manner, and were rarely found in the lung and liver. In addition, MSC-EVs were highly inclusive of various proteins and microRNAs (miRNAs) associated with neurogenesis and/or angiogenesis compared to fibro-EVs. We further analyzed those miRNAs and found that miRNA-184 and miRNA-210 were essential for promoting neurogenesis and angiogenesis of MSC-EVs, respectively. MSC-EVs represent an ideal alternative to MSCs for stroke treatment, with similar medicinal capacity but an improved safety profile that overcomes cell-associated limitations in stem cell therapy.
Keywords: Angiogenesis; Extracellular vesicles; Mesenchymal stem cells; MicroRNAs; Neurogenesis; Stroke.