Tatiana Abramova

Embryonic Stem Cell-Derived Exosomes Promote Endogenous Repair Mechanisms and Enhance Cardiac Function Following Myocardial Infarction

RATIONALE Embryonic stem cells (ESCs) hold great promise for cardiac regeneration but are susceptible to various concerns. Recently, salutary effects of stem cells have been connected to exosome secretion. ESCs have the ability to produce exosomes, however, their effect in the context of the heart is unknown. OBJECTIVE Determine the effect of ESC-derived exosome for the repair of ischemic myocardium and whether c-kit(+) cardiac progenitor cells (CPCs) function can be enhanced with ESC exosomes. METHODS AND RESULTS This study demonstrates that mouse ESC-derived exosomes (mES Ex) possess ability to augment function in infarcted hearts. mES Ex enhanced neovascularization, cardiomyocyte survival, and reduced fibrosis post infarction consistent with resurgence of cardiac proliferative response. Importantly, mES Ex augmented CPC survival, proliferation, and cardiac commitment concurrent with increased c-kit(+) CPCs in vivo 8 weeks after in vivo transfer along with formation of bonafide new cardiomyocytes in the ischemic heart. miRNA array revealed significant enrichment of miR290-295 cluster and particularly miR-294 in ESC exosomes. The underlying basis for the beneficial effect of mES Ex was tied to delivery of ESC specific miR-294 to CPCs promoting increased survival, cell cycle progression, and proliferation. CONCLUSIONS mES Ex provide a novel cell-free system that uses the immense regenerative power of ES cells while avoiding the risks associated with direct ES or ES-derived cell transplantation and risk of teratomas. ESC exosomes possess cardiac regeneration ability and modulate both cardiomyocyte and CPC-based repair programs in the heart.

Bone Marrow Progenitor Cell Therapy-Mediated Paracrine Regulation of Cardiac miRNA-155 Modulates Fibrotic Response in Diabetic Hearts

Diabetes is associated with a higher incidence of myocardial infarction (MI) and increased risk for adverse vascular and fibrogenic events post-MI. Bone marrow-derived progenitor cell (BMPC) therapy has been shown to promote neovascularization, decrease infarct area and attenuate left ventricular (LV) dysfunction after MI. Unlike vascular effects, the anti-fibrosis mechanisms of BMPC, specifically under diabetic conditions, are poorly understood. We demonstrated that intramyocardial delivery of BMPCs in infarcted diabetic db/db mice significantly down-regulates profibrotic miRNA-155 in the myocardium and improves LV remodeling and function. Furthermore, inhibition of paracrine factor hepatocyte growth factor (HGF) signaling in vivo suppressed the BMPC-mediated inhibition of miR-155 expression and the associated protective effect on cardiac fibrosis and function. In vitro studies confirmed that the conditioned media of BMPC inhibited miR-155 expression and profibrotic signaling in mouse cardiac fibroblasts under diabetic conditions. However, neutralizing antibodies directed against HGF blocked these effects. Furthermore, miR-155 over-expression in mouse cardiac fibroblasts inhibited antifibrotic Sloan-Kettering Institute proto-oncogene (Ski) and Ski-related novel gene, non-Alu-containing (SnoN) signaling and abrogated antifibrogenic response of HGF. Together, our data demonstrates that paracrine regulation of cardiac miRNAs by transplanted BMPCs contributes to the antifibrotic effects of BMPC therapy. BMPCs release HGF, which inhibits miR-155-mediated profibrosis signaling, thereby preventing cardiac fibrosis. These data suggest that targeting miR-155 might serve as a potential therapy against cardiac fibrosis in the diabetic heart.

Negative Regulation of miR‐375 by Interleukin‐10 Enhances Bone Marrow‐Derived Progenitor Cell‐Mediated Myocardial Repair and Function After Myocardial Infarction

Poor survival and function of transplanted cells in ischemic and inflamed myocardium likely compromises the functional benefit of stem cell‐based therapies. We have earlier reported that co‐administration of interleukin (IL)−10 and BMPAC enhances cell survival and improves left ventricular (LV) functions after acute myocardial infarction (MI) in mice. We hypothesized that IL‐10 regulates microRNA‐375 (miR‐375) signaling in BMPACs to enhance their survival and function in ischemic myocardium after MI and attenuates left ventricular dysfunction after MI. miR‐375 expression is significantly upregulated in BMPACs upon exposure to inflammatory/hypoxic stimulus and also after MI. IL‐10 knockout mice display significantly elevated miR‐375 levels. We report that ex vivo miR‐375 knockdown in BMPAC before transplantation in the ischemic myocardium after MI significantly improve the survival and retention of transplanted BMPACs and also BMPAC‐mediated post‐infarct repair, neovascularization, and LV functions. Our in vitro studies revealed that knockdown of miR‐375‐enhanced BMPAC proliferation and tube formation and inhibited apoptosis; over expression of miR‐375 in BMPAC had opposite effects. Mechanistically, miR‐375 negatively regulated 3‐phosphoinositide‐dependent protein kinase‐1 (PDK‐1) expression and PDK‐1‐mediated activation of PI3kinase/AKT signaling. Interestingly, BMPAC isolated from IL‐10‐deficient mice showed elevated basal levels of miR‐375 and exhibited functional deficiencies, which were partly rescued by miR‐375 knockdown, enhancing BMPAC function in vitro and in vivo. Taken together, our studies suggest that miR‐375 is negatively associated with BMPAC function and survival and IL‐10‐mediated repression of miR‐375 enhances BMPAC survival and function. Stem Cells 2015;33:3519–3529

Alcohol Consumption Negates Estrogen-mediated Myocardial Repair in Ovariectomized Mice by Inhibiting Endothelial Progenitor Cell Mobilization and Function

Background: Estrogen supplementation enhances voluntary alcohol consumption in ovariectomized rodents. The effects of the enhanced alcohol consumption on post-infarct myocardial repair are unknown. Results: Ethanol-mediated suppression of endothelial progenitor cells produces diminished post-ischemic left ventricular function. Conclusion: Estrogen-induced increases in alcohol consumption negatively compete with the cardioprotective effects of estrogen. Significance: Alcohol consumption during estrogen replacement therapy must be observed closely. We have shown previously that estrogen (estradiol, E2) supplementation enhances voluntary alcohol consumption in ovariectomized female rodents and that increased alcohol consumption impairs ischemic hind limb vascular repair. However, the effect of E2-induced alcohol consumption on post-infarct myocardial repair and on the phenotypic/functional properties of endothelial progenitor cells (EPCs) is not known. Additionally, the molecular signaling of alcohol-estrogen interactions remains to be elucidated. This study examined the effect of E2-induced increases in ethanol consumption on post-infarct myocardial function/repair. Ovariectomized female mice, implanted with 17β-E2 or placebo pellets were given access to alcohol for 6 weeks and subjected to acute myocardial infarction. Left ventricular functions were consistently depressed in mice consuming ethanol compared with those receiving only E2. Alcohol-consuming mice also displayed significantly increased infarct size and reduced capillary density. Ethanol consumption also reduced E2-induced mobilization and homing of EPCs to injured myocardium compared with the E2-alone group. In vitro, exposure of EPCs to ethanol suppressed E2-induced proliferation, survival, and migration and markedly altered E2-induced estrogen receptor-dependent cell survival signaling and gene expression. Furthermore, ethanol-mediated suppression of EPC biology was endothelial nitric oxide synthase-dependent because endothelial nitric oxide synthase-null mice displayed an exaggerated response to post-acute myocardial infarction left ventricular functions. These data suggest that E2 modulation of alcohol consumption, and the ensuing EPC dysfunction, may negatively compete with the beneficial effects of estrogen on post-infarct myocardial repair.

Elucidation of a novel pathway through which HDAC1 controls cardiomyocyte differentiation through expression of SOX-17 and BMP2.

Embryonic Stem Cells not only hold a lot of potential for use in regenerative medicine, but also provide an elegant and efficient way to study specific developmental processes and pathways in mammals when whole animal gene knock out experiments fail. We have investigated a pathway through which HDAC1 affects cardiovascular and more specifically cardiomyocyte differentiation in ES cells by controlling expression of SOX17 and BMP2 during early differentiation. This data explains current discrepancies in the role of HDAC1 in cardiovascular differentiation and sheds light into a new pathway through which ES cells determine cardiovascular cell fate.