Abstract 734: Paracrine Promotion of Diabetic Ischemic Ulcer Healing by Topically Applied Fetal Aorta-derived Vascular Progenitor Cells: Involvement of the Wnt Signaling
The therapeutic potential of vascular progenitor cells (VPC) either in limb ischemia or wound healing has been demonstrated. However, no information is available regarding the effectiveness of cell therapy under disease states, like diabetes, where the two conditions are associated. We aimed
to test the cicatrisation faculty of CD133+ VPC transplantation on excisional limb ulcers with overlaid ischemia (femoral artery ligation) in type 1 diabetic mice and
to determine the mechanisms of the cell therapy-induced repair.
Wounds were covered with collagen, collagen-embedded fetal aorta CD133+ or CD133− cells, or endothelial progenitor cells from adult peripheral blood (EPC). Transplantation of CD133+ VPC accelerated wound closure at days 3 and 7 (p<0.05 vs CD133− cells, EPC or collagen). Epidermal cell proliferation was higher in wounds given CD133+ or CD133− cells (p<0.01 vs collagen). Likewise, in vitro, human keratinocyte proliferation was stimulated by the conditioned culture medium (CCM) of CD133+ or CD133− cells (p<0.01 vs non-conditioned medium), with the effect blunted by PI3K inhibitor wortmannin (p<0.05). In vivo, only CD133+ VPC promoted angiogenesis, attenuated epidermal and endothelial cell apoptosis, and increased expression levels of Wnt7a (p<0.05 vs collagen or CD133−). Incorporation of transplanted cells was too low to account for cicatrisation. We found that CD133+ VPC release larger amounts of angiogenesis and keratinocyte-supporting soluble factors, such as VEGF-A, IL-8, and IL-6, compared with CD133− cells or EPC. Under high glucose, CD133+ but not CD133− CCM, stimulated keratinocyte and HUVEC chemotaxis, which were both reduced by an anti-VEGF neutralizing antibody (p<0.05). Moreover, CD133+ CCM induced GSK3β phosphorylation and expression of Wnt3, Wnt5a and Wnt9a by HUVEC, as well stimulated β-catenin translocation to the perinuclear region in scratch-wounded HUVEC, accelerating migration. In vitro wound closure was impaired by FrzA and antibodies neutralizing VEGF, IL6, and IL8 (p<0.05). The therapeutic action of CD133+ VPC is attributable to paracrine stimulation of vascularization and re-epithelization through integration of multiple signals that, amongst others, involve Wnt-mediated mechanisms.