Bone Marrow Alterations and Lower Endothelial Progenitor Cell Numbers in Critical Limb Ischemia Patients

Abstract

BackgroundCritical limb ischemia (CLI) is characterized by lower extremity artery obstruction and a largely unexplained impaired ischemic neovascularization response. Bone marrow (BM) derived endothelial progenitor cells (EPC) contribute to neovascularization. We hypothesize that reduced levels and function of circulating progenitor cells and alterations in the BM contribute to impaired neovascularization in CLI.MethodsLevels of primitive (CD34+ and CD133+) progenitors and CD34+KDR+ EPC were analyzed using flow cytometry in blood and BM from 101 CLI patients in the JUVENTAS-trial (NCT00371371) and healthy controls. Blood levels of markers for endothelial injury (sE-selectin, sICAM-1, sVCAM-1, and thrombomodulin), and progenitor cell mobilizing and inflammatory factors were assessed by conventional and multiplex ELISA. BM levels and activity of the EPC mobilizing protease MMP-9 were assessed by ELISA and zymography. Circulating angiogenic cells (CAC) were cultured and their paracrine function was assessed.ResultsEndothelial injury markers were higher in CLI (P<0.01). CLI patients had higher levels of VEGF, SDF-1α, SCF, G-CSF (P<0.05) and of IL-6, IL-8 and IP-10 (P<0.05). Circulating EPC and BM CD34+ cells (P<0.05), lymphocytic expression of CXCR4 and CD26 in BM (P<0.05), and BM levels and activity of MMP-9 (P<0.01) were lower in CLI. Multivariate regression analysis showed an inverse association between IL-6 and BM CD34+ cell levels (P = 0.007). CAC from CLI patients had reduced paracrine function (P<0.0001).ConclusionCLI patients have reduced levels of circulating EPC, despite profound endothelial injury and an EPC mobilizing response. Moreover, CLI patients have lower BM CD34+-cell levels, which were inversely associated with the inflammatory marker IL-6, and lower BM MMP-9 levels and activity. The results of this study suggest that inflammation-induced BM exhaustion and a disturbed progenitor cell mobilization response due to reduced levels and activity of MMP-9 in the BM and alterations in the SDF-1α/CXCR4 interaction contribute to the attenuated neovascularization in CLI patients.

Effect of Repetitive Intra-Arterial Infusion of Bone Marrow Mononuclear Cells in Patients With No-Option Limb Ischemia

“…The lack of benefit in our patients could be partly due to BM cell dysfunction in patients with high atherosclerotic burden. 43 The major amputation rate in our study was lower than expected based on the available literature at the time of the initiation of the trial. 25 More recent data suggest that amputation rates in no-option patients with advanced PAD have decreased over the past decades, in line with the observation in our study.…”

Dipeptidyl Peptidase-IV Inhibition for the Treatment of Cardiovascular Disease ― Recent Insights Focusing on Angiogenesis and Neovascularization ―

“…Clinical observations have shown that impaired neovascularization is probably attributable, at least in part, to inflammationinduced BM exhaustion and reduced progenitor cell mobilization associated with reductions in the levels of BM DPP4 and MMP-9 and changes in the SDF-1/CXCR4 interaction in patients with critical PAD. 41 In addition, Sun and (c) the beneficial effects of GLP-1 on angiogenesis in vivo are mediated in part via the ability of vildagliptin to increase adiponectin (APN) secretion. 6 Based on these findings, we propose that DPP-IV inhibition facilitates EC angiogenic events via VEGF/Src kinase-mediated eNOS-Akt signaling activation, an effect that may be mediated by both GLP-1-dependent and -independent mechanisms.…”

Bone Marrow Microvascular and Neuropathic Alterations in Patients With Critical Limb Ischemia

“…Patients with cardiovascular disease, including CLI, have low levels of circulating progenitor cells (PCs), which may contribute to their impaired neovascularization response. 1,2 The low PC levels have been suggested to be secondary to alterations at the bone marrow (BM) level; however, the effects of CLI on BM structure in humans have not been reported.…”