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Diabetic ulcers are difficult to heal. New hope for the treatment of these complications comes from stem cells. Recently, we identified cells similar to endothelial progenitor cells (EPCs) in the aorta of human foetuses. These cells (hVPCs)express early vascular markers and, under appropriate culture conditions, give origin to mature vascular-like structures, while in vivo stimulate vascular and skeletal regeneration. The present study evaluated the therapeutic potential of hVPCs in type 1 diabetic models of pressure or ischemic ulcers. Diabetes was induces by streptozotocin in CD1 mice. Skin wounds were produced between the scapulae or in limbs made ischemic by femoral artery occlusion. A total of 20,000 hVPCs or vehicle (collagen) was applied onto the ulcers. In diabetic, non-immunocompetent mice, hVPC-treated wounds measured 59% and 37% of the initial lesion at 3 and 7 days, respectively, whereas the contralaterals were 75% and 57% (P<0.05). The ratio of cell-treated vs collagen-treated wounds was 0.92±0.11 on day 0, then declining to 0.74±0.10 on day 3 and 0.56±0.08 on day 7. In contrast, the ratio was unchanged in controls given collagen on both sides. Wound neovascularization was increased 1.32-fold in hVPC-treated wounds (124±3 vs. 84±2 cap per mm2 in collagen-treated, P<0.01). Arteriole density was increased by 1.69-fold (5.5±1.1 vs. 1.7±0.8 art per mm2 in collagen-treated, P<0.01). Incorporation of human cells in murine tissue was recognized by immunostaining for human nuclear antigen, both at the border (5.4 cells per mm2) or center of the wound (6.8 cells per mm2), whereas no signal was detected in controls. The rate of cicatization was worsened by ischemia, resulting in ulcers 1.86- and 3.72-fold larger than non-ischemic ones at day 3 and 7. Transplantation of hVPCs accelerated wound closure during the first 3 days after ischemia (P<0.01). Improvement by cell therapy led ischemic ulcers to match the healing of non-ischemic wounds. No supplementary effect was seen in the late phase of recovery. Worthy to note, a 4-fold higher number of adults peripheral EPCs failed to produce therapeutic effects. In vitro, hVPCs released large amounts of immunoreactive VEGF-A and Angiopoietin 2.Transplantation of a low number of hVPC onto diabetic ulcers improves healing through potentiation of neovascularization. The beneficial effect could be ascribed to direct participation in vascular regeneration and to paracrine release of growth factors.
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J. Vasc. Biol. 42, Sup:2 (2005) p15