No abstract

Background Induced pluripotent stem cells and their differentiated cardiomyocytes ( iCM s) have tremendous potential as patient‐specific therapy for ischemic cardiomyopathy following myocardial infarctions, but difficulties in viable transplantation limit clinical translation. Exosomes secreted from iCM s (iCM‐Ex) can be robustly collected in vitro and injected in lieu of live iCM s as a cell‐free therapy for myocardial infarction. Methods and Results iCM ‐Ex were precipitated from iCM supernatant and characterized by protein marker expression, nanoparticle tracking analysis, and functionalized nanogold transmission electron microscopy. iCM ‐Ex were then used in in vitro and in vivo models of ischemic injuries. Cardiac function in vivo was evaluated by left ventricular ejection fraction and myocardial viability measurements by magnetic resonance imaging. Cardioprotective mechanisms were studied by JC ‐1 (tetraethylbenzimidazolylcarbocyanine iodide) assay, immunohistochemistry, quantitative real‐time polymerase chain reaction, transmission electron microscopy, and immunoblotting. iCM ‐Ex measured ≈140 nm and expressed CD 63 and CD 9. iCM and iCM ‐Ex micro RNA profiles had significant overlap, indicating that exosomal content was reflective of the parent cell. Mice treated with iCM ‐Ex demonstrated significant cardiac improvement post–myocardial infarction, with significantly reduced apoptosis and fibrosis. In vitro iCM apoptosis was significantly reduced by hypoxia and exosome biogenesis inhibition and restored by treatment with iCM ‐Ex or rapamycin. Autophagosome production and autophagy flux was upregulated in iCM ‐Ex groups in vivo and in vitro. Conclusions iCM‐Ex improve post–myocardial infarction cardiac function by regulating autophagy in hypoxic cardiomyoytes, enabling a cell‐free, patient‐specific therapy for ischemic cardiomyopathy.

Background Exosomes are small extracellular vesicles that function as intercellular messengers and effectors. Exosomal cargo contains regulatory small molecules, including mi RNA s, mRNA s, lnc RNA s, and small peptides that can be modulated by different pathological stimuli to the cells. One of the main mechanisms of action of drug therapy may be the altered production and/or content of the exosomes. Methods and Results We studied the effects on exosome production and content by neprilysin inhibitor/angiotensin receptor blockers, sacubitril/valsartan and valsartan alone, using human‐induced pluripotent stem cell‐derived cardiomyocytes under normoxic and hypoxic injury model in vitro , and assessed for physiologic correlation using an ischemic myocardial injury rodent model in vivo. We demonstrated that the treatment with sacubitril/valsartan and valsartan alone resulted in the increased production of exosomes by induced pluripotent stem cell‐derived cardiomyocytes in vitro in both conditions as well as in the rat plasma in vivo. Next‐generation sequencing of these exosomes exhibited downregulation of the expression of rno‐miR‐181a in the sacubitril/valsartan treatment group. In vivo studies employing chronic rodent myocardial injury model demonstrated that miR‐181a antagomir has a beneficial effect on cardiac function. Subsequently, immunohistochemical and molecular studies suggested that the downregulation of miR‐181a resulted in the attenuation of myocardial fibrosis and hypertrophy, restoring the injured rodent heart after myocardial infarction. Conclusions We demonstrate that an additional mechanism of action of the pleiotropic effects of sacubitril/valsartan may be mediated by the modulation of the mi RNA expression level in the exosome payload.