Intravenous Infusion of Exosomes Derived from Human Adipose Tissue-Derived Stem Cells Promotes Angiogenesis and Muscle Regeneration: An Observational Study in a Murine Acute Limb Ischemia Model.

INTRODUCTION: Recent studies have demonstrated that adipose tissue-derived stem cell (ADSC) transplantation could promote neoangiogenesis in various ischemic diseases. However, as whole cells, ADSCs have some disadvantages, such as shipping and storage issues, high costs, and controversies related to the fates of grafted cells in the recipients. Therefore, this study aimed to investigate the effects of intravenously infused exosomes purified from human ADSCs on ischemic disease in a murine hindlimb ischemia model.

METHODS: ADSCs were cultured in exosome-free medium for 48 h before the conditioned medium was collected for exosome isolation by ultracentrifugation. The murine ischemic hindlimb models were created by cutting and burning the hindlimb arteries. Exosomes were intravenously infused into murine models (ADSC-Exo group), with phosphate-buffered saline (PBS) used as a placebo (PBS group). Treatment efficacy was determined using a murine mobility assay (frequency of pedaling in water per 10 s), peripheral blood oxygen saturation (SpO2 index), and the recovery of vascular circulation by trypan blue staining. The formation of blood vessels was shown by X-ray. Expression levels of genes related to angiogenesis and muscle tissue repair were quantified by quantitative reverse-transcription polymerase chain reaction. Finally, H&E staining was used to determine the histological structure of muscle in the treatment and placebo groups.

RESULTS: The rates of acute limb ischemia in the PBS and ADSC-Exo injection groups were 66% (9/16 mice) and 43% (6/14 mice), respectively. The mobility of the limbs 28 days after surgery was significantly different between the ADSC-Exo treatment group (41 ± 1 times/10 s) and the PBS group (24 ± 1 times/10 s; n = 3; p < 0.05). Peripheral blood oxygen saturation 21 days after treatment was 83.83% ± 2.02% in the PBS group and 83% ± 1.73% in the ADSC-Exo treatment group, and the difference was not statistically significant (n = 3, p > 0.05). On day 7 after treatment, the time required to stain the toes after trypan blue injection was 20.67 ± 12.5 s and 85 ± 7.09 s in the ADSC-Exo and PBS groups, respectively (n = 3, p < 0.05). On day 3 after the operation, the expression of genes promoting angiogenesis and muscle remodeling, such as Flk1, Vwf, Ang1, Tgfb1, Myod, and Myf5, was increased 4-8 times in the ADSC-Exo group compared with the PBS group. No mice in either group died during the experimental period.

CONCLUSIONS: These results revealed that intravenous infusion of human ADSC-derived exosomes is a safe and effective method to treat ischemic disease, especially hindlimb ischemia, by promoting angiogenesis and muscle regeneration.