Human Adipose-Derived Endothelial Progenitor Cells Accelerate Epithelialization of Radiation Ulcers in Nude Mice

BACKGROUND: Cotransplantation of adipose-derived stem cells (ASCs) and endothelial progenitor cells has shown superior angiogenic effects compared with ASCs alone in recent animal studies. However, endothelial progenitor cells could only be collected from blood vessels or bone marrow. Thus, the authors have established a method for purifying adipose-derived endothelial progenitor cells (AEPCs). The authors hypothesized that AEPCs would enhance the therapeutic effect of ASCs on radiation ulcers. METHODS: Seven-week-old male nude mice (BALB/cAJcl-nu/nu) were irradiated on the dorsal skin (total 40 Gy); 12 weeks later, 6-mm-diameter wounds were created. The mice were then treated with subcutaneous injection of human ASCs [1 × 10 5 ( n = 4)], human AEPCs [2 × 10 5 or 5 × 10 5 ( n = 5)], combinations of those [ASCs 1 × 10 5 plus AEPCs 2 × 10 5 ( n = 4) or 5 × 10 5 ( n = 5)], or only vehicle ( n = 7). The nonirradiated group was also prepared as a control ( n = 6). The days required for macroscopic epithelialization was compared, and immunostaining for human-derived cells and vascular endothelial cells was performed at day 28. RESULTS: AEPC-ASC combination-treated groups healed faster than the ASC-treated group (14 ± 0 days versus 17 ± 2 days; P < 0.01). Engraftment of the injected cells could not be confirmed. Only the nonirradiated mice had significantly higher vascular density (0.988 ± 0.183 × 10 -5 /µm -2 versus 0.474 ± 0.092 × 10 -5 /µm 2 ; P = 0.02). CONCLUSION: The results suggested therapeutic potentials of AEPCs and an enhanced effect of combination with ASCs. This study is a xenogenic transplantation model, and further validation in an autologous transplantation model is needed. CLINICAL RELEVANCE STATEMENT: Human AEPCs and their combination with ASCs accelerated epithelialization of radiation ulcers in nude mice. The authors suggest that administration of humoral factors secreted from AEPCs (eg, treatment with culture-conditioned media) could be used for the same purpose.