Abstract 16009: Y RNA Fragments Enriched in Exosomes From Cardiosphere-derived Cells Mediate Cardioprotection and Macrophage Polarization
Background: Exosomes secreted by cardiosphere-derived cells (CDCs) are critical agents of regeneration and cardioprotection following ischemic injury, mediating the beneficial therapeutic effects of CDCs. Transfer of exosomal RNA to target cells is important for bioactivity.
Objective: We sought to determine the RNA content of CDCs-secreted exosomes (CDC-exo), and to assess the contributions of selected small non-coding RNAs to the therapeutic efficacy of CDC-exo.
Methods: Using next-generation sequencing (Illumina), we characterized the RNA content of CDC-exo. By direct transfection of fluorescently-labelled oligoribonucleotides, we delivered and tracked selected RNA fragments that are highly enriched in CDC-exo. In order to examine potential cytoprotective effects, neonatal rat ventricular myocytes (NRVMs) were pretreated with each of these fragments or a scrambled control fragment prior to H2O2-induced oxidative stress. Effects on gene expression were assessed by transfection of the fragments into bone marrow-derived macrophages.
Results: Several noncoding RNA species were present in CDC-exo. Among these, Y RNAs (either whole or in fragments of the 5’ end) constituted 18% of all hits. From this data set, we selected two highly-enriched Y RNA fragments. Both fragments localized to the cytoplasm of CDC, NRVM and macrophages, and conferred augmented resistance to oxidative stress of NRVM (64.25±31.13% viability vs. 44±26.85%; p=0.06). Additionally, macrophages transfected with Y fragments exhibit rapid, robust polarization to a distinctive gene expression profile notable for upregulation of IL-10 (83.07 vs. 0.59 fold; p<0.0001), an anti-inflammatory cytokine.
Conclusions: Here, we demonstrated that abundant noncoding RNA components of CDC-exo, Y RNA fragments, are bioactive components of CDC-exo. Two distinct fragments confer cardioprotection and also induce a strong anti-inflammatory response in macrophages. Although several components of the CDC-exo payload (including miRNA) contribute to functional efficacy, the present findings demonstrate the capacity of Y RNA fragments, an RNA species of previously-unknown function, to elicit therapeutic effects in vitro.
Author Disclosures: L. Cambier: None. G. de Couto: None. A. Ibrahim: Employment; Significant; Capricor, Inc. E. Marbán: Ownership Interest; Significant; Capricor Inc. Consultant/Advisory Board; Significant; Capricor Inc.
- © 2015 by American Heart Association, Inc.