Abstract 5441: Critical Role of Increased MicroRNA-126 Expression for the Pro-angiogenic Capacity of Autologous Human CD34+ Stem/Progenitor Cells
Circulating, bone-marrow derived CD34+ progenitor cells have been shown to promote ischemia-induced neovascularisation, and are currently explored as a potential novel therapeutic strategy in ischemic heart disease. By using culture approaches “early” endothelial progenitor cells (EPCs) are thought to be derived from CD34+/CD14+ cells, whereas “late outgrowth” EPCs are thought to be derived from CD34+/CD14− cells. The aim of the present study was to determine the expression of pro- and anti-angiogenic microRNAs in CD34+ cells and to characterize their role for endothelial growth promoting effects.
Methods: We examined the pro- and anti-angiogenic microRNA expression profile, of circulating CD34+14+ and CD34+14− stem/progenitor cells, as compared to CD34−14+ (monocytes) and CD34−14− (lymphocytes) isolated by MACS sorting from mononuclear cells, by using quantitative RT-PCR. Furthermore, pro-angiogenic effects of these cell populations were examined by tubulogenesis in co-cultures with differentiated endothelial cells (HAECs). In vivo endothelial repair capacity was determined by cell transplantation (200,000 cells) into nude mice with carotid endothelial injury. The functional role of differentially regulated miRs was characterized by transfection with anti-miRs and miR mimics.
Results: Only CD34+14+ and CD34+14−, but not CD34−14+ or CD34−14− cells exerted a pro-angiogenic effect, paralleled by a substantially increased expression of the pro-angiogenic miR126 and miR130a. Similarly, in vivo endothelial repair was enhanced by CD34+ cells with no significant difference between CD34+14+ and CD34+14− cells. CD34+ cell transfection with anti-miR-126 abolished the pro-angiogenic effects of CD34+ cells, whereas forced expression of miR126 (miR mimic) markedly enhanced their pro-angiogenic effects.
Conclusions: These findings demonstrate for the first time a differential pro-angiogenic microRNA expression of CD34+ stem/progenitor cells as compared to CD34− mononuclear cells. Importantly expression of miR126 is critical for endothelial growth promoting effects of CD34+ cells, and represents an interesting novel target to enhance the pro-angiogenic capacity of autologous CD34+ stem/progenitor cells.