Abstract 15107: Comparative Therapeutic Efficacy and Mechanism of Stem Cells in Rat Myocardial Infarction Model

Introduction: Successful cell therapy should be able to resist the hostile ischemic myocardium, should be retained for longer duration to continue secreting cardioprotective growth factors/exosomes and should not elicited immunological host response. Hypothesis: Analysis of 5 clinically relevant human stem/progenitor cells in a rodent model of acute myocardial infarction demonstrated that neonatal cardiac mesenchymal stromal cells (nMSCs) provide the strongest cardiac functional recovery. Methods: Cardiac functional outcome following nMSCs/aMSCs in rat MI model was measured by echocardiography. Transplanted cell retention, in vivo phagocytosis and CD68 + cells was assessed by immunohistochemistry. In vitro phagocytosis analysis for aMSCs/nMSCs were performed with THP-1 derived macrophages. THP-1 differentiated macrophages were validated for the expression of CD68 and absence of CD31. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for proteomic analysis of nMSCs and aMSCs. CD47 expression in nMSCs was blocked by anti-CD47/ siRNA transections/lenti-virus expressing CD47 shRNAs approaches. CD47 knock down efficiency by siRNA and lenti-virus were validated by immunoblot. Isotype antibody, scrambled siRNA and lentivirus expressing empty vector served as control. Results: Transplanted nMSCs significantly increased the number of tissue reparative macrophages and regulatory T cells and significantly decreased monocyte-derived inflammatory macrophages and neutrophils. nMSCs also showed immune evasion in the host myocardium. mRNA microarray and single-cell analyses combined with targeted depletion studies established CD47 in nMSCs as a key molecule responsible for stem cell retention in the myocardium through an antiphagocytic mechanism regulated by miR34a-5p. Gain- and loss-of-function studies demonstrated that mir34a-5p regulated the production of exosomes and cardioprotective paracrine factors in the nMSC secretome. Conclusions: We conclude that the functional benefits of nMSCs are governed by a novel miR34a-5p pathway regulating immunomodulation, cell retention, exosome production, and cytokine secretion.