Abstract 16186: Hypoxic Pre-conditioning on Human CD34+ Stem Cells Enhances Exosome Therapeutics of Ischemic Tissue Repair Through ETS-1-Regulated Pathway
Previous studies in our lab have revealed a novel mechanism that therapeutically important human CD34+ stem cells secrete exosomes (Exo) to extracellular milieu that induce angiogenic activity independent of the cells. Further studies demonstrated that CD34+ exosomes (CD34Exo) carry and transfer of proangiogenic miRNAs, such as miR-126, which affect the therapeutic function of the exosomes.
Herein we hypothesized that hypoxic treatment of CD34+ stem cells can modulate the miRNA content and regenerative efficacy of CD34Exo.
Methods and Results: Exosomes from human CD34+ cells cultured under hypoxia (H-Exo) were more proliferative, anti-apoptotic and angiogenic in vitro, as compared to exosomes from cells under normoxia (N-Exo). In a mouse model of hind limb ischemia, H-Exo treatment significantly enhanced 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). Flow cytometry and confocal microscopy indicated that H-Exo was uptaken by endothelial cells in the ischemic limb. Interestingly, hypoxic treatment did not alter the size and quantity of Exo or expression of major proteins of CD34Exo compared with normoxic treatment. However, hypoxic treatment altered the proangiogenic miRNA expression in H-Exo including miR-210 and miR-126. ETS-1, a transcription factor induced by hypoxia-inducible fator-1 (HIF-1) is known to regulate expression of miR-126. We have examined the protein and RNA expression of HIF-1 and ETS-1 in Sca-1 positive mouse hematopoietic stem cells, and propose that HIF-1/ETS-1 regulatory mechanisms affect the expression of exosomal miR-126 under hypoxia. These results are being confirmed in human CD34+ cells using siRNA silencing and HIF hydroxylase inhibitor dimethyloxalylglycine.
Conclusion: Hypoxia induced miR-126 expression in CD34 cell-derived exosomes stimulating exosomes-mediated angiogenesis and therapeutic recovery via ETS-transcriptional pathway. Our work has important clinical implications for therapeutic angiogenesis, especially in diabetic and cardiovascular patients who have stem cells with diminished angiogenic potential.
Author Disclosures: Y. Liang: None. P. Mathiyalagan: None. D. Kim: None. D. Losordo: None. R. Hajjar: None. S. Sahoo: Research Grant; Significant; AHA-SDG, NIH R01.
- © 2015 by American Heart Association, Inc.