Selective Recruitment of Endothelial Progenitor Cells to Ischemic Tissues with Increased Neovascularization

Abstract

Tissue ischemia remains a common problem in plastic surgery and one for which proangiogenic approaches have been investigated. Given the recent discovery of circulating endothelial stem or progenitor cells that are able to form new blood vessels, the authors sought to determine whether these cells might selectively traffic to regions of tissue ischemia and induce neovascularization. Endothelial progenitor cells were isolated from the peripheral blood of healthy human volunteers and expanded ex vivo for 7 days. Elevation of a cranially based random-pattern skin flap was performed in nude mice, after which they were injected with fluorescent-labeled endothelial progenitor cells (5 x 10(5); n = 15), fluorescent-labeled human microvascular endothelial cells (5 x 10(5); n = 15), or media alone (n = 15). Histologic examination demonstrated that endothelial progenitor cells were recruited to ischemic tissue and first appeared by postoperative day 3. Subsequently, endothelial progenitor cell numbers increased exponentially over time for the remainder of the study [0 cells/mm2 at day 0 (n = 3), 9.6 +/- 0.9 cells/mm2 at day 3 (n = 3), 24.6 +/- 1.5 cells/mm2 at day 7 (n = 3), and 196.3 +/- 9.6 cells/mm2 at day 14 (n = 9)]. At all time points, endothelial progenitor cells localized preferentially to ischemic tissue and healing wound edges, and were not observed in normal, uninjured tissues. Endothelial progenitor cell transplantation led to a statistically significant increase in vascular density in ischemic tissues by postoperative day 14 [28.7 +/- 1.2 in the endothelial progenitor cell group (n = 9) versus 18 +/- 1.1 in the control media group (n = 9) and 17.7 +/- 1.0 in the human microvascular endothelial cell group (n = 9; p < 0.01)]. Endothelial progenitor cell transplantation also showed trends toward increased flap survival [171.2 +/- 18 mm2 in the endothelial progenitor cell group (n = 12) versus 134.2 +/- 10 mm2 in the media group (n = 12) and 145.0 +/- 13 mm2 in the human microvascular endothelial cell group (n = 12)], but this did not reach statistical significance. These findings indicate that local tissue ischemia is a potent stimulus for the recruitment of circulating endothelial progenitor cells. Systemic delivery of endothelial progenitor cells increased neovascularization and suggests that autologous endothelial progenitor cell transplantation may have a role in the salvage of ischemic tissue.

Hypoxia-Induced Mediators of Stem/Progenitor Cell Trafficking Are Increased in Children With Hemangioma

“…11,12 These mediators are capable of enhancing the mobilization and recruitment of EPCs to ischemic tissue during postnatal vasculogenesis. [12][13][14][15][16] In the bone mar-row, MMP-9, which is also hypoxia responsive, 17 may lead to the release of EPCs by cleavage of membrane bound kit ligand. 18,19 Interestingly, children with proliferating hemangioma have increased urinary MMP-9, 20 a finding which warrants further investigation of the role of this important mediator of stem/progenitor cell trafficking in hemangioma growth.…”

Endothelial Progenitor Cells Derived From CD34⁺ Cells Form Cooperative Vascular Networks

“…Consistent with an EPC phenotype, immunostaining demonstrated that most adherent cells were positive for both uptake of DiI-ac-LDL and binding of FITC-UEA-l (Fig.2) [26][27][28][29].…”

Transplantation of Endothelial Progenitor Cells Transferred by Vascular Endothelial Growth Factor Gene for Vascular Regeneration of Ischemic Flaps

“…So, 3 days after injection, a cranially based 1.25 ϫ 2.5 cm flap, with the flap base 0.5 cm caudal to the occipital neck line, was elevated on the back of mice. A 0.13-mm-thick silicone sheet was inserted to separate the flap from the bed, and the flap was sutured in place without a dressing [3]. distance and on the same focus were taken by a digital camera.…”

“…Some studies have been reported of augmenting the survival area of flaps using drugs, laser, hyperbaric oxygen and ischemic preconditioning, the success rate of which, however, is not satisfactory in most studies [2]. Many of the reports on augmenting the survival areas of local flaps described above are mainly directed at augmenting the blood supply to the flaps [2,3].…”