Abstract 19109: Hypoxia-Induced Reprogramming of Exosomal MicroRNAs From Human CD34+ Progenitor Cells Promotes Its Angiogenic Activity and Ischemic Tissue Repair
Introduction: In early clinical trials, human CD34+ stem cells have been shown to improve exercise tolerance in pts with myocardial ischemia and reduce amputation rates in pts with critical limb ischemia. Recently, we have demonstrated that adult human CD34+ stem cells secrete microRNA containing membrane bound nanovesicles called exosomes (Exo) that mimic the angiogenic and therapeutic activity of the cells.
We hypothesized that the regenerative efficacy of the cell-free Exo derived from human CD34+ cells can be improved by hypoxic pre-conditioning, modulating its pro-angiogenic miRNA content.
Methods and Results: Exo from human peripheral blood-derived CD34+ cells cultured under hypoxia (H-Exo) were significantly more proliferative, anti-apoptotic and angiogenic in vitro, as compared to Exo from cells under normoxia (N-Exo). Treatment with H-Exo significantly improved perfusion (ratio: 0.93±0.05 v 0.77±0.02), increased capillary density (1.6±0.2 v 1.1±0.1/HPF) and prevented ischemic limb amputation (0% v 37.5%) as compared to N-Exo (p<0.05; n=7-8), in a mouse model of hind limb ischemia. H-Exo were not significantly different in size, quantity of Exo secreted per cell, or, in the expression of major proteins as compared to N-Exo, measured using DLS and 2-D differential gel electrophoresis (DIGE) and mass spectrometry analyses. Interestingly, H-Exo had significantly higher expression of several pro-angiogenic miRNAs. Trafficking studies using confocal microscopy and flow cytometry revealed that fluorescent-labeled CD34 Exo were selectively internalized by endothelial cells in the ischemic tissue and directly transfer pro-angiogenic miRNA content, inducing cell cycle changes and cell division in the recipient endothelial cells. Currently, we are investigating the role of transcription factors in hypoxia-induced miRNA expression.
Conclusion: Hypoxia modulates the miRNA content of adult human CD34+ progenitor cell-derived exosomes improving their angiogenic and therapeutic potency. Use of hypoxia to enhance microRNA composition of CD34+ exosomes could have important clinical implications for therapeutic angiogenesis, especially in diabetic and cardiovascular patients with compromised stem cell population.
- © 2013 by American Heart Association, Inc.