Adipose-derived stem cell spheroid treated with low-level light irradiation accelerates spontaneous angiogenesis in mouse model of hindlimb ischemia

Background aims. We investigated whether low-level light irradiation (LLLI) before adipose-derived stromal cells (ASCs) spheroid transplantation improved hind-limb functional recovery by stimulation of angiogenesis. Methods. The spheroid, composed of ASCs, was irradiated with low-level light and expressed angiogenic factors, including vascular endothelial growth factor and basic fibroblast growth factor. From immunochemical staining analysis, the spheroid of ASCs included CD31(+), KDR and CD34(+), whereas monolayer-cultured ASCs were negative for these markers. To evaluate the therapeutic effect of the ASC spheroid treated with LLLI in vivo, phosphate-buffered saline, monolayer ASCs, LLLI-monolayer ASCs, spheroid ASCs and LLLI-spheroid ASCs were transplanted into a hind-limb ischemia model. Results. The LLLI-spheroid ASCs transplanted into the hind-limb ischemia differentiated into endothelial cells and remained differentiated. Transplantation of LLLI-spheroid ASCs into the hind-limb ischemia significantly elevated the density of vascular formations through angiogenic factors released by the ASCs and enhanced tissue regeneration at the lesion site. Consistent with these results, the transplantation of LLLI-spheroid ASCs significantly improved functional recovery compared with ASC or spheroid ASC transplantation and PBS treatment. Conclusions. These findings suggest that transplantation of ASC spheroid treated with LLLI may be an effective stem cell therapy for the treatment of hind-limb ischemia and peripheral vascular disease.