INS and type 2 diabetes mellitus: Compared with the C57BL/6J mice, the T2DM mice injected with PBS and those injected with MSC-sEVs and Ap-MSC-sEVs exhibited a significant increase in the number of insulin-positive and Ki-67-positive cells within the islets, which suggested that the increased replication of β-cells likely drove the enlargement of the β-cell area (Fig. 5b) (P < 0.05).