Abstract 16803: Endothelial Cells Communicate with Vascular Smooth Muscle Cells Via Transfer of microRNA Contained in Secreted Exosomes
Background: Endothelial cell (EC) mediated inhibition of vascular smooth muscle cell (VSMC) proliferation plays an important role in maintaining vascular wall homeostasis and preventing atherosclerosis. The mechanism that mediates this effect has not been clarified. MicroRNAs (miR) are ∼23nt RNAs that regulate many important cellular processes by post-transcriptional regulation of gene expression. Exosomes are small (30-100nm) vesicles secreted from cells, and previously shown to contain miR. We hypothesized that intercellular transfer of miRNA from EC to VSMC via exosomes contributes to the inhibition of VSMC proliferation.
Results: We show that EC secreted exosomes contain abundant miRs and protect their contents from degradation by circulating RNases. The miR population in secreted exosomes differs significantly from the cytoplasmic miR population, indicating regulation of miR packaging in ECs. Conditioned media of ECs inhibited Human Aortic VSMC (HAVSMC) proliferation by 37.4% (n=4, p=0.0006) at 120 hrs, while exosome-depleted conditioned media loses this inhibitory effect (n=4, p=0.0001). Purified exosomes applied directly to VSMCs inhibited HAVSMC proliferation by 28.8% at 72hrs (n= 8, p= 0.0107) and by 26.9% at 96 hrs (n=8, p=0.0596). Similar results were found with Coronary Artery SMC proliferation (data not shown). EC-derived exosomes are taken up into recipient SMCs, as seen by ICC to an exosome marker, GFP-CD63, and by qPCR to transferred miRNAs. Transfection into VSMC of RNA purified from EC secreted exosomes is sufficient to inhibit SMC proliferation (34.8%, n= 9, p=0.0001), and provides a similar level of inhibition compared to whole exosome treatment (33.5%, n=9, p=0.001). The miRNA population of exosomes can be engineered through transfection of the progenitor EC; transfection with pre-mir-203 leads to a 317-fold increase in exosomal mir-203 levels, and a 126-fold increase in SMCs treated with EC-derived conditioned media.
Conclusions: This is the first evidence that ECs can communicate with VSMCs via transfer of exosomal miRs and further, identify this process as a mechanism for EC-mediated inhibition of VSMC proliferation. These findings also identify exosomal miRs as a potential therapeutic agent in vascular disease.
- © 2011 by American Heart Association, Inc.