Abstract 16656: Cardiosphere-derived Cell Exosomes Reduce Proinflammatory Gene Expression and Enhance Efferocytosis of Macrophages to Reduce Infarct Size Following Ischemia-reperfusion Injury
Introduction: Cardiosphere-Derived Cells (CDCs) are cardioprotective against ischemia/reperfusion (I/R) injury if delivered within 20-30 min of reperfusion (Kanazawa et al, Circ HF 2015; de Couto et al, JCI 2015). The effects of CDC-mediated protection have been attributed to distinctive polarization of macrophages (Mφ) via CDC exosomes (CDCexo). Enhanced phagocytic capacity is the key phenotypic feature of CDCexo-primed (MCDCexo). Here we show that MCDCexo reduce proinflammatory stress and subsequent infarct expansion by rapidly scavenging cellular debris from dying cells (i.e., cardiomyocytes) following I/R, a process known as efferocytosis.
Methods & Results: Wistar-Kyoto rats (aged 8-12 weeks) underwent 45 min of ischemia followed by 20 min of reperfusion, and were then randomly allocated to intracoronary infusion of CDCexo or inert fibroblast exosomes (FBexo; control). Two days later, hearts were excised for histological analysis or cardiac Mφ isolation. Hearts from animals treated with CDCexo, in contrast to FBexo, had reduced infarct mass (CDCexo: 6.38% vs. FBexo: 13.32%; p<0.05) and attenuated proinflammatory gene expression in cardiac Mφ (Nos2, Tnf, Il6; p<0.05). To test whether CDCexo enhance Mφ efferocytosis, bone marrow-derived Mφ were primed toward M1 (LPS & IFNγ), M2 (IL-4 & IL-13), MFBexo (FBexo), or MCDCexo (CDCexo) overnight. The following day, neonatal rat ventricular myocytes were stained with DiI then UV-irradiated (254nm) to generate apoptotic cells (ACs), which were placed in co-culture with primed Mφ. One hour later, MCDCexo Mφ exhibited enhanced uptake of ACs (M1: 3.07%; M2: 18.4%; MFBexo: 15.73%; MCDCexo: 24.30%; p<0.05). To test Mφ efferocytosis in vivo, eGFP rats underwent LAD ligation and 2x106 DiI-labeled MCDCexo or MFBexo Mφ were injected into the border zone. Two hours later, cardiac Mφ were isolated; MCDCexo Mφ had greater uptake of eGFP than MFBexo (p<0.05).
Conclusions: CDCexo reduce infarct size when delivered via the intracoronary route 20 min post-I/R. Furthermore, CDCexo reduce proinflammatory cytokine expression in cardiac Mφ and promote Mφ-mediated efferocytosis of apoptotic debris in vitro and in vivo. These findings rationalize the requirement for Mφ as mediators of CDC-induced cardioprotection.
Author Disclosures: G. de Couto: None. E. Jaghatspanyan: None. E. Kravets: None. E. Marbán: Consultant/Advisory Board; Significant; Capricor Inc..
- © 2016 by American Heart Association, Inc.