Transplantation of iMSCs-Exo stimulated angiogenesis in the ischemic limb. (A) Mouse endothelial cells were stained red for surface marker CD31 and green for surface marker CD34. Nuclei (blue) were stained with 4′, 6-diamidino-2-phenylindole (DAPI). Compared with the control group, the iMSCs-Exo group had a significant microvessel density improvement at days 7, 14, and 21 (3.11-, 3.14-, and 3.46-fold increase relative to the control group on days 7, 14, and 21 for CD31 staining, and 2.56-, 2.64-, and 3.01-fold increase relative to the control group on days 7, 14, and 21 for CD34 staining, respectively; *P <0.05). (B) Microvessel density in the control group rarely increased; however, in the iMSCs-Exo group, there was a significant increase at days 7, 14, and 21 (*P <0.05). iMSCs-Exo, exosomes derived from induced pluripotent stem cell-derived mesenchymal stem cells.