Abstract
We hypothesized that endothelial progenitor cells derived from individuals with diabetes would exhibit functional defects including inability to respond to hypoxia and altered paracrine/autocrine function that would impair the angiogenic potential of these cells. Circulating mononuclear cells isolated from diabetic (n = 69) and nondiabetic (n = 46) individuals were used to grow endothelial colony forming cells (ECFC), early endothelial progenitor cells (eEPCs) and isolate CD34+ cells. ECFCs and eEPCs were established from only 15% of the diabetic individuals tested thus directing our main effort toward examination of CD34+ cells. CD34+ cells were plated in basal medium to obtain cell-free conditioned medium (CM). In CM derived from CD34+ cells of diabetic individuals (diabetic-CM), the levels of stem cell factor, hepatocyte growth factor, and thrombopoietin were lower, and IL-1β and tumor necrosis factor (TNFα) levels were higher than CM derived from nondiabetic individuals (nondiabetic-CM). Hypoxia did not upregulate HIF1α in CD34+ cells of diabetic origin. Migration and proliferation of nondiabetic CD34+ cells toward diabetic-CM were lower compared to nondiabetic-CM. Attenuation of pressure-induced constriction, potentiation of bradykinin relaxation, and generation of cGMP and cAMP in arterioles were observed with nondiabetic-CM, but not with diabetic-CM. Diabetic-CM failed to induce endothelial tube formation from vascular tissue. These results suggest that diabetic subjects with microvascular complications exhibit severely limited capacity to generate ex-vivo expanded endothelial progenitor populations and that the vasoreparative dysfunction observed in diabetic CD34+ cells is due to impaired autocrine/paracrine function and reduced sensitivity to hypoxia.
Highlights
Many diabetic individuals with ischemic cardiac and vascular disease remain symptomatic despite exhausting conventional medical therapy and mechanical revascularization
endothelial colony forming cells (ECFC) and endothelial progenitor cells (eEPCs) were Infrequently Generated in Diabetic Individuals with Microvascular Complications
ECFCs and eEPCs were only obtained from 15% of the diabetic individuals (Figure 1) while both types of cells could be grown from nearly 90% of the nondiabetic individuals
Summary
Many diabetic individuals with ischemic cardiac and vascular disease remain symptomatic despite exhausting conventional medical therapy and mechanical revascularization. Increasing evidence suggests that microvascular insufficiency plays a significant role in the pathophysiology of this ischemia. Recognizing the magnitude of this problem, investigators have worked to develop new treatments that have led to the evolution of therapeutic angiogenesis. Preclinical and clinical data provide evidence that growth factors and stem/progenitor cells may be used therapeutically for repair of ischemic tissue. Preclinical studies have provided evidence for safety and the potential therapeutic potency of vascular progenitor cells. Clinical trials using a variety of approaches have supporting the feasibility, safety and bioactivity of these cells for treatment of advanced cardiovascular disease with the goal of repairing ischemic tissue
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