NSC-derived exosomes enhance therapeutic effects of NSC transplantation on cerebral ischemia in mice

Transplantation of neural stem cells (NSCs) has been proved to promote functional rehabilitation of brain lesions including ischemic stroke. However, the therapeutic effects of NSC transplantation is limited by the low survival and differentiation rates of NSCs due to the harsh environment in the brain after ischemic stroke. Here, we employed NSCs derived from human induced pluripotent stem cells (iPSCs) together with exosomes extracted from NSCs to treat cerebral ischemia induced by middle cerebral artery occlusion/reperfusion (MCAO/R) in mice. The results showed that NSC-derived exosomes significantly reduced the inflammatory response, alleviated oxidative stress after NSC transplantation, and facilitated NSCs differentiation in vivo. The combination of NSCs with exosomes ameliorated the injury of brain tissue including cerebral infarct, neuronal death and glial scarring, and promoted the motor function recovery. To explore the underlying mechanisms, we analyzed the miRNA profiles of NSC-derived exosomes and the potential downstream genes. Our study provided the rationale for the clinical application of NSC-derived exosomes as a supportive adjuvant for NSC transplantation after stroke. Overall design: Eighty-eight MCAO/R mice were randomly divided into 4 groups at 7 days post operation, and twelve mice with low body weight (less than 15g) were excluded. Mice were anesthetized and placed in a mouse stereoscopic apparatus (RWD, China). The skull was drilled to make a burr hole above the lateral ventricle (AP+0, ML-1, DV-2.25 mm) for NSCs and exosomes injection. NSCs were genetically labeled with tdTomato for cell tracking. The five groups were treated as follows: Model (MCAO/R mice treated with 5 µL PBS), Exo (MCAO/R mice treated with 10 µg exosomes in 5 µL PBS), NSC (MCAO/R mice treated with 5×105 NSCs in 5 µL PBS), NSC+Exo (MCAO/R mice treated with 5×105 NSCs combine with 10 µg exosomes in 5 µL PBS) and Sham (fifteen mice with sham operation not treated). We did not perform high-throughput sequencing of all samples that participated in animal experiments.