Proangiogenic soluble factors from amniotic fluid stem cells mediate the recruitment of endothelial progenitors in a model of ischemic fasciocutaneous flap

Skin flaps are routinely used in surgery for the functional and cosmetic repair of wounds or disfiguring scars. The recent concept of therapeutic angiogenesis has emerged as an attractive approach to overcome the problem of blood supply deficiency, often resulting in the flap grafting failure. In the present study, we embedded a gelatin membrane with amniotic fluid stem cells (AFSC) derived conditioned media (ACM) to topically deliver angiogenic growth factors and cytokines into a rat model of ischemic full-thickness skin flap elevated in the epigastric region. AFSC secretome triggered the endogenous repair by the recruitment of endothelial progenitor cells. We studied the vascular perfusion rate, the vessel distribution, and the survival of ACM-treated flaps. In detail, the ischemic sectors of ACM-treated flaps showed at day 7 a perfusion level 50% higher than the preoperation baseline. The ensuing necrosis development was delayed and the histology analysis showed a normal arrangement of epidermal and dermal structures and a high density of vessels in subcutaneous tissues. Further, we found that ACM recruited CD31+/VEGFR2+ and CD31+/CD34+ cells into the ischemic subcutaneous tissues and that the isolated progenitors were capable to form clusters of von Willebrand factor-positive cells in culture. We propose ACM as a cell-free cocktail of chemokines and growth factors to be adopted for clinical applications.