Ultrasound-induced microbubble destruction promotes targeted delivery of adipose-derived stem cells to improve hind-limb ischemia of diabetic mice.

This study aimed to investigate whether ultrasound-induced microbubble destruction was able to promote targeted delivery of adipose-derived stem cells (ASCs) to improve hind-limb ischemia of diabetic mice. Ischemia was induced in the lower limb of db/db mice which were then randomly divided into 5 groups: PBS group, Sham group, ultrasound + microbubble group (US+MB), US+MB+ASCs group and ASCs group. Contrast-enhanced ultrasound perfusion imaging showed the ratio of blood flow in ischemic hind-limb to that in contralateral limb increased over time in five groups. A significant enhancement in US+MB+ASCs group was observed compared with US+MB group (P<0.01). Immunofluorescence microscopy of hind-limb muscle showed the microvessel density (microvessels/skeletal muscle fibers) and arteriolar density in US+MB+ASCs group were higher than in US+MB group, and significantly higher than in other control groups (P<0.01). Masson staining indicated the degree of muscle fibrosis in US+MB+ASCs group was lower than in US+MB. 3 and 7 days after therapy, ELISA and RT-PCR showed the expression of VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than in US+MB group, and dramatically increased as compared to other groups (P<0.01). 3 and 7 days after therapy, Western blot assay showed the protein expression of P-P13K, P-AKT, VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than US+MB group (P<0.01). The bioeffects of ultrasound-induced microbubble cavitation is able to up-regulate the expression of pro-inflammatory cytokines, which may improve the targeted delivery, adhesion and paracrine of ASCs, attenuating the hind-limb ischemia in diabetic mice.