Abstract 20070: Hypoxic Reprogramming of Exosomal miRNAs by Ets Transcription Factors in Human CD34+ Stem Cells Promotes Ischemic Tissue Repair
Introduction: In a first study of its kind, we have demonstrated a novel mechanism that therapeutic human CD34+ stem cells secrete membrane bound nano-sized vesicles called exosomes (Exo) into their paracrine secretion. Our preliminary data suggests that cell-free Exo mimic the angiogenic and therapeutic activity of CD34+ cells and carry several proangiogenic miRNAs, such as miR-126 that affects their function.
Hypothesis: We hypothesized that the regenerative efficacy of the cell-free CD34Exo can be improved by hypoxic pre-conditioning, modulating its pro-angiogenic miRNA content.
Methods and Results: Exosomes 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 exosomes 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. Flow cytometry and confocal microscopy demonstrated that H-Exo were selectively uptaken by endothelial cells in the ischemic limb and induced their proliferation and cell cycle-related proteins. Interestingly, 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 including miR-210 and miR-126. Ets transcription factors are known to regulate hypoxia-mediated responses and affect the expression of HIF factors and miR-210. We have investigated the role of these transcription factors in hypoxia-induced miRNA expression.
Conclusions: Hypoxia modulates the miRNA content of exosomes from human CD34+ stem cells improving their angiogenic and therapeutic potency. Use of hypoxia to enhance microRNA content of CD34+ exosomes could be clinically important for therapeutic angiogenesis, especially in diabetic and cardiovascular patients with compromised stem cell population.
Author Disclosures: D. Kim: None. D.E. Vaughan: None. S.E. Quaggin: None. D.W. Losordo: None. S. Sahoo: None.
This research has received full or partial funding support from the American Heart Association
- © 2014 by American Heart Association, Inc.