In conclusion, early injection of HucMSC-EVs can improve blood glucose level and insulin secretion in NOD mice, affect expression of splenocyte transcription factors, T-bet and GATA-3, adjust the Th1/Th2 ratio, and influence the secretion of inflammatory factors, thereby reducing inflammatory responses, downregulating Fas/Fasl-mediated islet β cell apoptosis, and finally delaying diabetes development. The gene discussed is FAS; the disease is diabetes mellitus.