Abstract TP270: Adipose Derived Mesenchymal Stem Cells Reduce Autophagic Flux After Ischemic Stroke in Mice via Extracellular Vesicle Transfer of MiR-25-3p

Abstract

Transplantation of mesenchymal stem cells (MSCs) yields neuroprotection and enhanced neurological recovery in pre-clinical stroke models, which is mediated by the secretion of extracellular vesicles (EVs). The latter are a heterogenous group of vesicles containing microvesicles, exosomes, and apoptotic bodies. The neuroprotective cargo of EVs, however, has not yet been identified. To investigate such a cargo and its underlying mechanism, we designed a series of in vitro and in vivo experiments. Primary neurons were exposed to oxygen-glucose-deprivation (OGD) and co-cultured with either adipose-derived MSCs (ADMSCs) or treated with ADMSC-secreted EVs. As expected, both ADMSCs and ADMSC-secreted EVs significantly reduced neuronal death after 12 h of OGD and 24 h of reoxygenation, showing no difference between the two treatment groups. Screening for various signaling cascades being involved in the interaction between ADMSCs and neurons revealed a decreased autophagic flux as well as a declined p53-Bnip3 activity. However, these signaling cascades were significantly blocked when ADMSCs were pretreated with the inhibitor of exosomal secretion GW4869. In light of miR-25-3p being the most highly expressed miRNA in ADMSC-EVs interacting with the p53 pathway, further in vitro work focused on this pathway. Treatment with a miR-25-3p oligonucleotide mimic reduced cell death, whereas the anti-oligonucleotide increased autophagic flux and cell death by modulating p53-Bnip3 signaling in primary neurons exposed to OGD. Likewise, native ADMSC-EVs but not EVs obtained from ADMSCs pretreated with the anti-miR-25-3p oligonucleotide (ADMSC-EVs anti-miR-25-3p ) confirmed the aforementioned in vitro observations in C57BL6 mice exposed to cerebral ischemia. Infarct size was reduced and neurological recovery was increased in mice treated with native ADMSC-EVs when compared to ADMSC-EVs anti-miR-25-3p . As such, ADMSCs induce neuroprotection - at least in part - by improved autophagic flux through secreted EVs containing miR-25-3p. Hence, our work for the first time uncovers a key factor in naturally secreted ADMSC-EVs for the regulation of autophagy and induction of neuroprotection in a pre-clinical stroke model.