Background Inflammation plays a critical role in adverse cardiac remodeling and heart failure. Therefore, approaches geared towards inhibiting inflammation may provide therapeutic benefits. We tested the hypothesis that genetic deletion of interleukin-10 (IL10), a potent anti-inflammatory cytokine, exacerbates pressure-overload induced adverse cardiac remodeling and hypertrophy and that IL10 therapy inhibits this pathology. Methods and Results Cardiac hypertrophy was induced in Wild-type (WT) and IL10-knockout (KO) mice by isoproterenol (ISO) infusion. ISO-induced left ventricular (LV) dysfunction and hypertrophic remodeling, including fibrosis and fetal gene expression, were further exaggerated in KO mice compared to WT. Systemic recombinant mouse IL10 administration markedly improved LV function and not only inhibited but also reversed ISO-induced cardiac remodeling. Intriguingly, very similar cardio-protective response of IL10 was found in transverse aortic constriction (TAC)-induced hypertrophy and heart failure model. In neonatal rat ventricular myocytes (NRCM) and H9c2 myoblasts, ISO activated NFκB while it inhibited STAT3 phosphorylation. Interestingly, IL10 suppressed ISO-induced NFκB activation and attenuated STAT3 inhibition. Moreover, pharmacological and genetic inhibition of STAT3 reversed the protective effects of IL10 while ectopic expression of constitutively active STAT3 mimicked the IL10 responses on the ISO effects, confirming that IL10 mediated inhibition of NFκB is STAT3 dependent. Conclusions Taken together our studies suggest IL10 treatment as a potential therapeutic approach to limit the progression of pressure overload-induced adverse cardiac remodeling.

Rationale Endothelial progenitor cell (EPC) survival and function in the injured myocardium is adversely influenced by hostile microenvironment like ischemia, hypoxia and inflammatory response, thereby compromising full benefits of EPC-mediated myocardial repair. Objective We hypothesized that interleukin-10 (IL-10) modulates EPC biology leading to enhanced survival and function following transplantation in the ischemic myocardium. Methods and Results Myocardial infarction (MI)-induced mobilization of bone marrow EPC (Sca-1+Flk1+ cells) into the circulation was significantly impaired in IL-10 KO-mice. Bone marrow transplantation (BMT) to replace IL-10 KO-marrow with WT-marrow attenuated these effects. Impaired mobilization was associated with lower SDF-1 expression levels in the myocardium of KO-mice. Interestingly, SDF-1 administration reversed mobilization defect in KO-mice. In vitro, hypoxia-mediated increases in CXCR4 expression and cell survival were lower in IL-10-deficient-EPCs. Furthermore, SDF-1-induced migration of WT-EPCs was inhibited by AMD3100, an inhibitor of CXCR4. To further study the effect of IL-10 on in vivo EPC survival and engraftment into vascular structures, GFP-labeled EPC were injected intramyocardially after induction of MI, and the mice were treated with either saline or recombinant IL-10. IL-10-treated group showed increased retention of transplanted EPCs in the myocardium and was associated with significantly reduced EPC apoptosis post-MI. Interestingly, increased EPC retention and their association with the vascular structures was observed in IL-10 treated mice. Increased EPC survival and angiogenesis in the myocardium of IL-10-treated mice corroborated with improved LV function, reduced infarct size and fibrosis in the myocardium. In vitro, IL-10-induced increase in VEGF expression in WT-EPC was abrogated by STAT3 inhibitor suggesting IL-10 signals via STAT3 activation. Conclusions Taken together, our studies demonstrate that MI-induced EPC mobilization was impaired in IL-10 KO-mice and that IL-10 increases EPC survival and function possibly via activation of STAT3/VEGF signaling cascades, leading to attenuation of MI-induced LV dysfunction and remodeling.

Rationale While Bone-marrow endothelial progenitor cell based therapies (BM-EPC) improve the symptoms in patients with ischemic heart disease their limited plasticity and decreased function in patients with existing heart disease limits the full benefit of EPC therapy for cardiac regenerative medicine. Objective We hypothesized that reprogramming mouse and/or human EPCs using small molecules targeting key epigenetic repressive marks would lead to a global increase in active gene transcription, induce their cardiomyogenic potential and enhance their inherent angiogenic potential. Method and Results Mouse Lin-Sca1+CD31+ EPCs and human CD34+ cells were treated with inhibitors of DNA methyltransferases (5-Azacytidine), histone deacetylases (valproic acid) and G9a histone di-methyltransferase. Forty eight hour treatment led to global increase in active transcriptome including the reactivation of pluripotency associated and CMC specific mRNA expression while EC specific genes were significantly up-regulated. When cultured under appropriate differentiation conditions, reprogrammed EPCs showed efficient differentiation into CMC and vascular smooth muscle cells. Treatment with epigenetic modifying agents show marked increase in histone acetylation on cardiomyocyte and pluripotent cell specific gene promoters. Intra-myocardial transplantation of reprogrammed mouse and human EPCs in an acute myocardial infarction mouse model showed significant improvement in ventricular functions, which was histologically supported by their de novo CMC differentiation and increased capillary density and reduced fibrosis. Importantly, cell transplantation was safe and did not form teratomas. Conclusions Taken together, our results suggest that epigenetically reprogrammed EPCs display a safe, more plastic phenotype and improve post-infarct cardiac repair by both neo-cardiomyogenesis and neovascularization.

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The Sindbis virus (SIN) nonstructural protein nsP4 possesses the RNA-dependent RNA polymerase activity required for the replication of the SIN genome and transcription of a subgenomic mRNA during infection. Isolation of this protein from other viral components of the RNA synthetic complex allowed the characterization of template requirements for nsP4-mediated genome replication. The major findings of this study are: (i) in the absence of other viral proteins nsP4 is capable of copying SIN plus- and minus-strand templates, but does not transcribe subgenomic RNA; (ii) mutations in the 3' conserved sequence element and poly(A) tail of the plus-strand template prevent nsP4-mediated de novo initiation of minus-strand RNA synthesis; (iii) nsP4-dependent terminal addition of nucleotides occurs on template RNA possessing certain mutations in the 3'CSE and polyadenylate tail ; (iv) nsP4 is capable of minus-strand synthesis independent of the sequence at the 5' end of the template; (v) an A-U rich sequence in the 3'CSE represents a binding site for a replicase component, probably nsP4; (vi) plus-strand genomic RNA synthesis is dependent on the 3' end of the minus-strand template. These studies begin to define the specific interactions with the viral RNA templates mediated by individual components of the viral replication complex and suggest a model for ternary complex formation during the initiation of minus-strand RNA synthesis.