Foxc1 Regulates Early Cardiomyogenesis and Functional Properties of Embryonic Stem Cell Derived Cardiomyocytes.

Embryonic Stem Cells (ESCs) hold great potential for regeneration of damaged myocardium, however the molecular circuitry that guides ESC differentiation into cardiomyocytes remains poorly understood. This is exemplified by the elusive role of the transcription factor, Foxc1, during cardiac development. The only known Foxc1 target during heart development is Tbx1. Because Foxc1 null mice contain heart mutations that are far more severe than Tbx1 null mice, it is likely that Foxc1 has additional regulatory roles during heart development. The goal of our study was to test whether Foxc1 is critical for ESC differentiation into functional cardiomyocytes through proper regulation of specific downstream gene networks. Converging evidence from Foxc1 deficient and overexpression ESC models reveals a close relationship between Foxc1 levels and early cardiomyogenic factors Isl1, Mef2c, and Nkx2.5 and also the production of functional cardiomyocytes. We show Foxc1 regulates early cardiomyogenesis during a specific window of differentiation, D4-D6. Through whole transcriptome RNA-sequencing analysis, we report pathways regulated by Foxc1 involved in cardiac function including actin cytoskeleton, cell adhesion, tight and gap junctions, and calcium signaling. Our data indicate a novel Foxc1 direct gene target, Myh7, which encodes the predominant myosin heavy chain isoform, MHCß, expressed during cardiac development. These data lead us to conclude that Foxc1 regulates both early cardiomyogenesis and the functional properties of ESC-derived cardiomyocytes. Our findings shed light on the molecular circuitry governing cardiomyogenesis that may lead to the development of better translational strategies for the use of pluripotent stem cells in regenerative medicine towards repairing damaged myocardium. Stem Cells 2016;34:1487-1500.

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.

Navigating the labyrinth of cardiac regeneration.

Heart disease is the number one cause of morbidity and mortality in the world and is a major health and economic burden, costing the United States Health Care System more than $200 billion annually. A major cause of heart disease is the massive loss or dysfunction of cardiomyocytes caused by myocardial infarctions and hypertension. Due to the limited regenerative capacity of the heart, much research has focused on better understanding the process of differentiation toward cardiomyocytes. This review will highlight what is currently known about cardiac cell specification during mammalian development, areas of controversy, cellular sources of cardiomyocytes, and current and potential uses of stem cell derived cardiomyocytes for cardiac therapies. Developmental Dynamics 245:751-761, 2016. © 2016 Wiley Periodicals, Inc.

Enhanced angiogenic and cardiomyocyte differentiation capacity of epigenetically reprogrammed mouse and human endothelial progenitor cells augments their efficacy for ischemic myocardial repair.

RATIONALE: Although bone marrow endothelial progenitor cell (EPC)-based therapies improve the symptoms in patients with ischemic heart disease, their limited plasticity and decreased function in patients with existing heart disease limit the full benefit of EPC therapy for cardiac regenerative medicine. OBJECTIVE: We hypothesized that reprogramming mouse or human EPCs, or both, 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 dimethyltransferase. A 48-hour treatment led to global increase in active transcriptome, including the reactivation of pluripotency-associated and cardiomyocyte-specific mRNA expression, whereas endothelial cell-specific genes were significantly upregulated. When cultured under appropriate differentiation conditions, reprogrammed EPCs showed efficient differentiation into cardiomyocytes. Treatment with epigenetic-modifying agents show marked increase in histone acetylation on cardiomyocyte and pluripotent cell-specific gene promoters. Intramyocardial 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 cardiomyocyte 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 postinfarct cardiac repair by both neocardiomyogenesis and neovascularization.

Interleukin-10 treatment attenuates pressure overload-induced hypertrophic remodeling and improves heart function via signal transducers and activators of transcription 3-dependent inhibition of nuclear factor-κB.

BACKGROUND: Inflammation plays a critical role in adverse cardiac remodeling and heart failure. Therefore, approaches geared toward inhibiting inflammation may provide therapeutic benefits. We tested the hypotheses that genetic deletion of interleukin-10 (IL-10), a potent antiinflammatory cytokine, exacerbates pressure overload-induced adverse cardiac remodeling and hypertrophy and that IL-10 therapy inhibits this pathology. METHODS AND RESULTS: Cardiac hypertrophy was induced in wild-type and IL-10 knockout mice by isoproterenol (ISO) infusion. ISO-induced left ventricular dysfunction and hypertrophic remodeling, including fibrosis and fetal gene expression, were further exaggerated in knockout mice compared with wild-type mice. Systemic recombinant mouse IL-10 administration markedly improved left ventricular function and not only inhibited but also reversed ISO-induced cardiac remodeling. Intriguingly, a very similar cardioprotective response of IL-10 was found in transverse aortic constriction-induced hypertrophy and heart failure models. In neonatal rat ventricular myocytes and H9c2 myoblasts, ISO activated nuclear factor-κB and inhibited signal transducers and activators of transcription 3 (STAT3) phosphorylation. Interestingly, IL-10 suppressed ISO-induced nuclear factor-κB activation and attenuated STAT3 inhibition. Moreover, pharmacological and genetic inhibition of STAT3 reversed the protective effects of IL-10, whereas ectopic expression of constitutively active STAT3 mimicked the IL-10 responses on the ISO effects, confirming that the IL-10-mediated inhibition of nuclear factor-κB is STAT3 dependent. CONCLUSION: Taken together, our results suggest IL-10 treatment as a potential therapeutic approach to limit the progression of pressure overload-induced adverse cardiac remodeling.

Histone deacetylase 1 deficiency impairs differentiation and electrophysiological properties of cardiomyocytes derived from induced pluripotent cells.

Epigenetic and chromatin modifications play particularly important roles in embryonic and induced pluripotent stem cells (ESCs and iPSCs) allowing for the cells to both differentiate and dedifferentiate back to a pluripotent state. We analyzed how the loss of a key chromatin-modifying enzyme, histone deacetylase 1 (HDAC1), affects early and cardiovascular differentiation of both ESCs and iPSCs. We also investigated potential differences between these two cell types when differentiation is induced. Our data indicate an essential role for HDAC1 in deacetylating regulatory regions of key pluripotency-associated genes during early differentiation. Although HDAC1 functions primarily as a HDAC, its loss also affects DNA methylation in ESCs and iPSCs both during pluripotency and differentiation. We show that HDAC1 plays a crucial, nonredundant role in cardiomyocyte differentiation and maturation. Our data also elucidate important differences between ESCs and iPSCs, when levels of this enzyme are reduced, that affect their ability to differentiate into functional cardiomyocytes. As varying levels of chromatin-modifying enzymes are likely to exist in patient-derived iPSCs, understanding the molecular circuitry of these enzymes in ESCs and iPSCs is critical for their potential use in cardiovascular therapeutic applications

Interleukin-10 deficiency impairs bone marrow-derived endothelial progenitor cell survival and function in ischemic myocardium.

RATIONALE: Endothelial progenitor cell (EPC) survival and function in the injured myocardium is adversely influenced by hostile microenvironment such as 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 after 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 knockout (KO) mice. Bone marrow transplantation to replace IL-10 KO marrow with wild-type (WT) marrow attenuated these effects. Impaired mobilization was associated with lower stromal cell-derived factor (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. The IL-10-treated group showed increased retention of transplanted EPCs in the myocardium and was associated with significantly reduced EPC apoptosis after 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 left ventricular 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 through 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 through activation of STAT3/VEGF signaling cascades, leading to attenuation of MI-induced left ventricular dysfunction and remodeling.

Myocardial knockdown of mRNA-stabilizing protein HuR attenuates post-MI inflammatory response and left ventricular dysfunction in IL-10-null mice.

Prolonged inflammatory response is associated with left ventricular (LV) dysfunction and adverse remodeling following myocardial infarction (MI). IL-10 inhibits inflammation by suppressing HuR-mediated mRNA stabilization of proinflammatory cytokines. Here we report that following MI, IL-10(-/-) mice showed exaggerated LV dysfunction, fibrosis, and cardiomyocyte apoptosis. Short-hairpin RNA (shRNA)-mediated knockdown of HuR in the myocardium significantly reversed MI-induced LV dysfunctions and LV remodeling. HuR knockdown significantly reduced MI-induced cardiomyocyte apoptosis concomitant with reduced p53 expression. Moreover, HuR knockdown significantly reduced infarct size and fibrosis area, which in turn was associated with decreased TGF-beta expression. In vitro, stable knockdown of HuR in mouse macrophage cell line RAW 264.7 corroborated in vivo data and revealed reduced mRNA expression of TNF-alpha, TGF-beta, and p53 following LPS challenge, which was associated with a marked reduction in the mRNA stability of these genes. Taken together, our studies suggest that HuR is a direct target of IL-10, and HuR knockdown mimics anti-inflammatory effects of IL-10.

IL-10 inhibits inflammation and attenuates left ventricular remodeling after myocardial infarction via activation of STAT3 and suppression of HuR.

Persistent inflammatory response has adverse effects on left ventricular (LV) function and remodeling following acute myocardial infarction. We hypothesized that suppression of inflammation with interleukin (IL)-10 treatment attenuates LV dysfunction and remodeling after acute myocardial infarction. After the induction of acute myocardial infarction, mice were treated with either saline or recombinant IL-10, and inflammatory response and LV functional and structural remodeling changes were evaluated. IL-10 significantly suppressed infiltration of inflammatory cells and expression of proinflammatory cytokines in the myocardium. These changes were associated with IL-10-mediated inhibition of p38 mitogen-activated protein kinase activation and repression of the cytokine mRNA-stabilizing protein HuR. IL-10 treatment significantly improved LV functions, reduced infarct size, and attenuated infarct wall thinning. Myocardial infarction-induced increase in matrix metalloproteinase (MMP)-9 expression and activity was associated with increased fibrosis, whereas IL-10 treatment reduced both MMP-9 activity and fibrosis. Small interfering RNA knockdown of HuR mimicked IL-10-mediated reduction in MMP-9 expression and activity in NIH3T3 cells. Moreover, IL-10 treatment significantly increased capillary density in the infarcted myocardium which was associated with enhanced STAT3 phosphorylation. Taken together, our studies demonstrate that IL-10 suppresses inflammatory response and contributes to improved LV function and remodeling by inhibiting fibrosis via suppression of HuR/MMP-9 and by enhancing capillary density through activation of STAT3.

Human induced pluripotent stem cell-derived atrial cardiomyocytes carrying an SCN5A mutation identify nitric oxide signaling as a mediator of atrial fibrillation.

Mutations in SCN5A, encoding the cardiac sodium channel, are linked with familial atrial fibrillation (AF) but the underlying pathophysiologic mechanisms and implications for therapy remain unclear. To characterize the pathogenesis of AF-linked SCN5A mutations, we generated patient-specific induced pluripotent stem cell-derived atrial cardiomyocytes (iPSC-aCMs) from two kindreds carrying SCN5A mutations (E428K and N470K) and isogenic controls using CRISPR-Cas9 gene editing. We showed that mutant AF iPSC-aCMs exhibited spontaneous arrhythmogenic activity with beat-to-beat irregularity, prolonged action potential duration, and triggered-like beats. Single-cell recording revealed enhanced late sodium currents (INa,L) in AF iPSC-aCMs that were absent in a heterologous expression model. Gene expression profiling of AF iPSC-aCMs showed differential expression of the nitric oxide (NO)-mediated signaling pathway underlying enhanced INa,L. We showed that patient-specific AF iPSC-aCMs exhibited striking in vitro electrophysiological phenotype of AF-linked SCN5A mutations, and transcriptomic analyses supported that the NO signaling pathway modulated the INa,L and triggered AF.

Cell-free embryonic stem cell extract-mediated derivation of multipotent stem cells from NIH3T3 fibroblasts for functional and anatomical ischemic tissue repair.

The oocyte-independent source for the generation of pluripotent stem cells is among the ultimate goals in regenerative medicine. We report that on exposure to mouse embryonic stem cell (mESC) extracts, reversibly permeabilized NIH3T3 cells undergo dedifferentiation followed by stimulus-induced redifferentiation into multiple lineage cell types. Genome-wide expression profiling revealed significant differences between NIH3T3 control and ESC extract-treated NIH3T3 cells including the reactivation of ESC-specific transcripts. Epigenetically, ESC extracts induced CpG demethylation of Oct4 promoter, hyperacetylation of histones 3 and 4, and decreased lysine 9 (K-9) dimethylation of histone 3. In mouse models of surgically induced hindlimb ischemia or acute myocardial infarction transplantation of reprogrammed NIH3T3 cells significantly improved postinjury physiological functions and showed anatomic evidence of engraftment and transdifferentiation into skeletal muscle, endothelial cell, and cardiomyocytes. These data provide evidence for the generation of functional multipotent stem-like cells from terminally differentiated somatic cells without the introduction of retroviral mediated transgenes or ESC fusion.

STAT3-dependent mouse embryonic stem cell differentiation into cardiomyocytes: analysis of molecular signaling and therapeutic efficacy of cardiomyocyte precommitted mES transplantation in a mouse model of myocardial infarction.

Pluripotent embryonic stem (ES) cell therapy may be an attractive source for postinfarction myocardial repair and regeneration. However, the specific stimuli and signal pathways that may control ES cell-mediated cardiomyogenesis remains to be completely defined. The aim of the present study was to investigate (1) the effect and underlying signal transduction pathways of leukemia inhibitory factor (LIF) and bone-morphogenic protein-2 (BMP-2)-induced mouse ES cell (mES-D3 line) differentiation into cardiomyocytes (CMC) and (2) the efficacy of CMC precommitted mES cells for functional and anatomical cardiac repair in surgically-induced mouse acute myocardial infarction (AMI) model. Various doses of LIF and BMP-2 and their inhibitors or blocking antibodies were tested for mES differentiation to CMC in vitro. CMC differentiation was assessed by mRNA and protein expression of CMC-specific markers, Connexin-43, CTI, CTT, Mef2c, Tbx5, Nkx2.5, GATA-4, and alphaMHC. LIF and BMP-2 synergistically induced the expression of CMC markers as early as 2 to 4 days in culture. Signaling studies identified STAT3 and MAP kinase (ERK1/2) as specific signaling components of LIF+BMP-2-mediated CMC differentiation. Inhibition of either STAT3 or MAPK activation by specific inhibitors drastically suppressed LIF+BMP-2-mediated CMC differentiation. Moreover, in mouse AMI, transplantation of lentivirus-GFP-transduced, LIF+BMP-2 precommitted mES cells, improved post-MI left ventricular functions, and enhanced capillary density. Transplanted cells engrafted in myocardium and differentiated into CMC and endothelial cells. Our data suggest that LIF and BMP-2 may synergistically enhance CMC differentiation of transplanted stem cells. Thus augmentation of LIF/BMP-2 downstream signaling components or cell type specific precommitment may facilitate the effects of ES cell-based therapies for post-MI myocardial repair and regeneration.

Electrophysiologic Characterization of Calcium Handling in Human Induced Pluripotent Stem Cell-Derived Atrial Cardiomyocytes.

Human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes (CMs) hold great promise for elucidating underlying cellular mechanisms that cause atrial fibrillation (AF). In order to use atrial-like hiPSC-CMs for arrhythmia modeling, it is essential to better understand the molecular and electrophysiological phenotype of these cells. We performed comprehensive molecular, transcriptomic, and electrophysiologic analyses of retinoic acid (RA)-guided hiPSC atrial-like CMs and demonstrate that RA results in differential expression of genes involved in calcium ion homeostasis that directly interact with an RA receptor, chicken ovalbumin upstream promoter-transcription factor 2 (COUP-TFII). We report a mechanism by which RA generates an atrial-like electrophysiologic signature through the downstream regulation of calcium channel gene expression by COUP-TFII and modulation of calcium handling. Collectively, our results provide important insights into the underlying molecular mechanisms that regulate atrial-like hiPSC-CM electrophysiology and support the use of atrial-like CMs derived from hiPSCs to model AF.

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.

Inhibition of melanoma angiogenesis by telomere homolog oligonucleotides.

Telomere homolog oligonucleotides (T-oligos) activate an innate telomere-based program that leads to multiple anticancer effects. T-oligos act at telomeres to initiate signaling through the Werner protein and ATM kinase. We wanted to determine if T-oligos have antiangiogenic effects. We found that T-oligo-treated human melanoma (MM-AN) cells had decreased expression of vascular endothelial growth factor (VEGF), VEGF receptor 2, angiopoeitin-1 and -2 and decreased VEGF secretion. T-oligos activated the transcription factor E2F1 and inhibited the activity of the angiogenic transcription factor, HIF-1alpha. T-oligos inhibited EC tubulogenesis and total tumor microvascular density matrix invasion by MM-AN cells and ECs in vitro. In melanoma SCID xenografts, two systemic T-oligo injections decreased by 60% (P < .004) total tumor microvascular density and the functional vessels density by 80% (P < .002). These findings suggest that restriction of tumor angiogenesis is among the host's innate telomere-based anticancer responses and provide further evidence that T-oligos may offer a powerful new approach for melanoma treatment.

17Beta-estradiol mobilizes bone marrow-derived endothelial progenitor cells to tumors.

Neovascularization is critical for tumor growth and development. The cellular mediators for this process are yet to be defined. We discovered that bone marrow-derived endothelial progenitor cells (BM-EPC), having the phenotype (CD133+, CD34+, VEGFR-2+), initiate neovascularization in response to TG1-1 mammary cells implanted in the inguinal mammary gland of Tie-2 GFP transgenic mice. The fluorescence tag allowed for tracing the migration of green fluorescent protein-tagged endothelial progenitor cells to tumor tissues. We discovered that 17-beta estradiol supplementation of ovariectomized mice significantly enhanced BM-EPC-induced neovascularization and secretion of angiogenic factors within the tumor microenvironment. Cell-based system analyses showed that estrogen-stimulated BM-EPCs secreted paracrine factors which enhanced TG1-1 cell proliferation and migration. Furthermore, TG1-1 cell medium supplemented with estrogen-induced BM-EPC mediated tubulogenesis, which was an experimental in vivo representation of the neovasculature. Our data provide evidence of BM-EPC mammary tumor cell interactions and identify a novel cellular mediator of tumor progression that can be exploited clinically.