Abstract 329: The Human Pericardial Fluid is Enriched With Cardiovascular-expressed Micrornas and Exosomes Able to Elicit Therapeutic Responses

Abstract

Cells release functionally active microRNAs (miRs) into extracellular vesicles (EVs: exosomes and microparticles). In vitro, EVs shuttle miRs and other molecules between cells. The functional relevance of EVs in the context of human physiopathology is still debated. We hypothesize that the pericardial fluid (PF) mediates myocardium cell-to-cell communication through EVs exchanges. Here, we aimed to (1) characterize human PF EVs and exosomal miRs; (2) investigate if PF EVs exert a biological function. PF, plasma, thoracic aorta (TA) and right atrium appendage (RAA) samples were collected as leftovers from aortic valve replacement surgery. A miR array identified PF miRs expression. The top expressed cardiovascular miRs were measured (RT-qPCR) in TA and RAA (to validate expression in patients cardiovascular tissues), PF and plasma, and exosomes enriched from PF and plasma. EVs concentration and size distribution in PF and plasma were quantified by a nanoparticle tracking analysis system. The exosome functional activity was tested in human endothelial cells (ECs) and in a mouse model of limb ischemia (LI). A pool of cardiovascular miRs (including miR-21 and -29a), were enriched in the PF in comparison to plasma, suggesting that the PF/plasma concentration gradients of cardiovascular miRs were caused by the trafficking of these miRs from the myocardium and thoracic vessels to the PF. This gradient was reverted for the negative control miR-122 (produced by the liver and undetectable in the PF). Exosomes were abundant in the PF, even if less concentrated than in plasma. PF-exosome treatment of ECs exposed to hypoxia significantly decreased cell apoptosis and increased cell proliferation (P<0.01 vs PBS). Local PF-exosomes delivery increased post-LI ischemic blood flow recovery (P<0.01 vs PBS). By contrast, plasma-exosomes were not effective (P=NS vs PBS). We have provided the first characterization of EVs and exosomal miRs in the human PF and for first identified a therapeutic potential of PF- exosomes from cardiovascular patients. Future studies will be tailored to exploit the properties PF-exosome in regenerative medicine.