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+ 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 cardiac progenitor cell (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 utilizes 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.

Circular RNAs are generated from many protein-coding genes, but their role in cardiovascular health and disease states remains unknown. Here we report identification of circRNA transcripts that are differentially expressed in post myocardial infarction (MI) mouse hearts including circFndc3b which is significantly down-regulated in the post-MI hearts. Notably, the human circFndc3b ortholog is also significantly down-regulated in cardiac tissues of ischemic cardiomyopathy patients. Overexpression of circFndc3b in cardiac endothelial cells increases vascular endothelial growth factor-A expression and enhances their angiogenic activity and reduces cardiomyocytes and endothelial cell apoptosis. Adeno-associated virus 9 -mediated cardiac overexpression of circFndc3b in post-MI hearts reduces cardiomyocyte apoptosis, enhances neovascularization and improves left ventricular functions. Mechanistically, circFndc3b interacts with the RNA binding protein Fused in Sarcoma to regulate VEGF expression and signaling. These findings highlight a physiological role for circRNAs in cardiac repair and indicate that modulation of circFndc3b expression may represent a potential strategy to promote cardiac function and remodeling after MI.

Rationale: Systemic inflammation compromises the reparative properties of endothelial progenitor cell (EPC) and their exosomes on myocardial repair, although the underlying mechanism of loss of function of exosomes from inflamed EPCs is still obscure. Objective: To determine the mechanisms of IL-10 (interleukin-10) deficient-EPC–derived exosome dysfunction in myocardial repair and to investigate if modification of specific exosome cargo can rescue reparative activity. Methods and Results: Using IL-10 knockout mice mimicking systemic inflammation condition, we compared therapeutic effect and protein cargo of exosomes isolated from wild-type EPC and IL-10 knockout EPC. In a mouse model of myocardial infarction (MI), wild-type EPC-derived exosome treatment significantly improved left ventricle cardiac function, inhibited cell apoptosis, reduced MI scar size, and promoted post-MI neovascularization, whereas IL-10 knockout EPC-derived exosome treatment showed diminished and opposite effects. Mass spectrometry analysis revealed wild-type EPC-derived exosome and IL-10 knockout EPC-derived exosome contain different protein expression pattern. Among differentially expressed proteins, ILK (integrin-linked kinase) was highly enriched in both IL-10 knockout EPC-derived exosome as well as TNFα (tumor necrosis factor-α)-treated mouse cardiac endothelial cell–derived exosomes (TNFα inflamed mouse cardiac endothelial cell–derived exosome). ILK-enriched exosomes activated NF-κB (nuclear factor κB) pathway and NF-κB–dependent gene transcription in recipient endothelial cells and this effect was partly attenuated through ILK knockdown in exosomes. Intriguingly, ILK knockdown in IL-10 knockout EPC-derived exosome significantly rescued their reparative dysfunction in myocardial repair, improved left ventricle cardiac function, reduced MI scar size, and enhanced post-MI neovascularization in MI mouse model. Conclusions: IL-10 deficiency/inflammation alters EPC-derived exosome function, content and therapeutic effect on myocardial repair by upregulating ILK enrichment in exosomes, and ILK-mediated activation of NF-κB pathway in recipient cells, whereas ILK knockdown in exosomes attenuates NF-κB activation and reduces inflammatory response. Our study provides new understanding of how inflammation may alter stem cell-exosome–mediated cardiac repair and identifies ILK as a target kinase for improving progenitor cell exosome-based cardiac therapies.

Background Micro ribonucleic acid (miR) dysregulation in the myocardium has been implicated in cardiac remodeling after injury or stress. Objectives This study sought to explore the role of miR in human CD34+ cell (hCD34+) dysfunction in vivo after transplantation into the myocardium under ischemia-reperfusion (I-R) conditions. Methods In response to inflammatory stimuli, the miR array profile of endothelial progenitor cells (EPC) was analyzed using a polymerase chain reaction-based miR microarray. MiR-377 expression was assessed in myocardial tissue from human patients with heart failure (HF). We investigated the effect of miR-377 inhibition on hCD34+ cell angiogenic proteome profile, in vitro and on cardiac repair and function after I-R injury in immunodeficient mice. Results The miR array data from EPCs in response to inflammatory stimuli indicate changes in numerous miR with a robust decrease in miR-377. Human cardiac biopsies from HF patients showed significant increase in miR-377 expression compared to nonfailing control hearts. Proteome profile of hCD34+ cells transfected with miR-377 mimics showed significant decrease in proangiogenic proteins versus nonspecific control transfected cells. We also validated that serine/threonine kinase 35 is a target of miR-377 using a dual-luciferase reporter assay. In a mouse model of myocardial I-R, intramyocardial transplantation of miR-377-silenced hCD34+ cells in immunodeficient mice, promoting neovascularization (at 28 days, post-I-R) and lower interstitial fibrosis, leading to improved left ventricular (LV) function. Conclusions These findings indicate that HF increases miR-377 in the myocardium, which is detrimental to stem cell function, and transplantation of miR-377 knockdown hCD34+ cells into ischemic myocardium promoted their angiogenic ability, attenuating LV remodeling and cardiac fibrosis.

Background Bone marrow cell-based treatment for critical limb ischemia (CLI) in diabetic patients yielded a modest therapeutic effect due to cell dysfunction. Therefore, approaches that improve diabetic stem/progenitor cell functions may provide therapeutic benefits. Here, we tested the hypotheses that restoration of hydrogen sulfide (H2S) production in diabetic bone marrow cells (BMCs) improves their reparative capacities. Methods Mouse BMCs were isolated by density-gradient centrifugation. Unilateral hind limb ischemia (HLI) was conducted in 12- to 14-week old db/+ and db/db mice by ligation of left femoral artery. H2S level was measured by either gas chromatography or staining with florescent dye sulfidefluor 7AM. Results Both H2S production and cystathionine γ-lyase (CSE), an H2S enzyme, levels were significantly decreased in BMCs from diabetic db/db mice. Administration of H2S donor diallyl trisulfide (DATS) or overexpression of CSE restored H2S production and enhanced cell survival and migratory capacity in high glucose (HG)-treated BMCs. Immediately after HLI surgery, the db/+ and db/db mice were administrated with DATS orally and/or local intramuscular injection of GFP-labeled BMCs or RFP-CSE-overexpressing BMCs (CSE-BMCs). Mice with HLI were divided into six groups: 1) db/+; 2) db/db; 3) db/db+BMCs; 4) db/db+DATS; 5) db/db+DATS+BMCs; 6) db/db+CSE-BMCs. DATS and CSE overexpression greatly enhanced diabetic BMCs retention in ischemic hind limbs (IHL) followed by improved blood perfusion, capillary/arteriole density, skeletal muscle architecture and cell survival, and decreased perivascular CD68+ cell infiltration in IHL of diabetic mice. Interestingly, DATS or CSE overexpression rescued HG-impaired migration, tube formation and survival of BMCs or mature human cardiac microvascular endothelial cells (HCMVECs). Mechanistically, DATS restored nitric oxide production and decreased eNOS-pT495 levels in HCMVECs, and improved BMC angiogenic activity under HG condition. Finally, silencing CSE by siRNA significantly increased eNOS-pT495 levels in HCMVECs. Conclusions Decreased CSE-mediated H2S bioavailability is an underlying source of BMC dysfunction in diabetes. Our data indicate that H2S and overexpression of CSE in diabetic BMCs may rescue their dysfunction and open novel avenues for cell-based therapeutics of CLI in diabetic patients.

Taken together, our studies demonstrate that anti-miR-375 therapy reduced inflammatory response, decreased cardiomyocyte death, improved LV function, and enhanced angiogenesis by targeting multiple cell types mediated at least in part through PDK-1/AKT signalling mechanisms.

Background Activated fibroblasts (myofibroblasts; myoFBs) play critical role in cardiac fibrosis; however, their origin in the diseased heart remains unclear warranting further investigation. Recent studies suggest the contribution of bone marrow fibroblast progenitor cells (BM-FPC) in pressure overload (PO)-induced cardiac fibrosis. We have earlier shown that interleukin-10 (IL10) suppresses PO-induced cardiac fibrosis; however, the role of IL10 in inhibition of BM-FPC-mediated cardiac fibrosis is not known. We hypothesized that IL10 inhibits PO-induced homing of BM-FPCs to the heart and their trans-differentiation to myoFBs and thus attenuates cardiac fibrosis. Methods Pressure overload was induced in wild-type (WT) and IL10 knockout (IL10KO) mice by transverse aortic constriction (TAC). To determine the bone marrow origin, chimeric mice were created using eGFP WT mice marrow to the IL10KO mice. For mechanistic studies, fibroblast progenitor cells were isolated from mouse bone marrow. Results Pressure overload enhanced bone marrow fibroblast progenitor cell (BM-FPC) mobilization and homing in IL10KO mice compared to WT mice. Furthermore, WT bone marrow (from eGFP mice) transplantation in BM-depleted IL10KO mice (IL10KO chimeric mice) reduced TAC-induced BM-FPC mobilization compared to IL10KO mice. GFP co-staining with αSMA or collagen 1α in left ventricular tissue sections of IL10KO chimeric mice suggest that myofibroblasts were derived from bone marrow post-TAC. Finally, WT-BMT in IL10KO mice inhibited TAC-induced cardiac fibrosis and improved heart function. At the molecular level, IL10 treatment significantly inhibited TGFβ-induced transdifferentiation and fibrotic signaling in WT BM-FPC in vitro. Furthermore, fibrosis-associated miRNAs expression was highly upregulated in IL10KO-FPCs compared to WT-FPCs. PCR-based selective miRNA analysis revealed that TGFβ-induced enhanced expression of fibrosis-associated miRNAs (miRNA-21, -145 and -208) was significantly inhibited by IL10. Restoration of miRNA-21 levels suppressed the IL10 effects on TGFβ-induced fibrotic signaling in BM-FPC. Conclusion Our findings suggest that IL10 inhibits BM-FPC homing and trans-differentiation to myofibroblasts in pressure overloaded myocardium. Mechanistically for the first time we showed that IL10 suppresses Smad-miRNA-21 mediated activation of BM-FPCs and thus modulates cardiac fibrosis.

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 IL-10 and BMPAC enhances cell survival and improves LV (LV) functions after AMI in mice. We hypothesized that IL-10 regulates miR-375 signaling in BMPACs to enhance their survival and function in ischemic myocardium after MI and attenuates left ventricular dysfunction after MI. MicroRNA-375 expression is significantly up regulated in BMPACs upon exposure to inflammatory/hypoxic stimulus and also after MI. IL-10 KO mice display significantly elevated miR-375 levels. We report that ex vivo miR-375 knock down 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.