Congenital heart diseases (CHD) occur in nearly 1% of all live births and are the major cause of infant mortality and morbidity. Although an improved understanding of the genetic causes of CHD would provide insight into the underlying pathobiology, the genetic etiology of most CHD remains unknown. Here we show that mutations in the gene encoding the transcription factor GATA6 cause CHD characteristic of a severe form of cardiac outflow tract (OFT) defect, namely persistent truncus arteriosus (PTA). Two different GATA6 mutations were identified by systematic genetic analysis using DNA from patients with PTA. Genes encoding the neurovascular guiding molecule semaphorin 3C (SEMA3C) and its receptor plexin A2 (PLXNA2) appear to be regulated directly by GATA6, and both GATA6 mutant proteins failed to transactivate these genes. Transgenic analysis further suggests that, in the developing heart, the expression of SEMA3C in the OFT/subpulmonary myocardium and PLXNA2 in the cardiac neural crest contributing to the OFT is dependent on GATA transcription factors. Together, our data implicate mutations in GATA6 as genetic causes of CHD involving OFT development, as a result of the disruption of the direct regulation of semaphorin-plexin signaling.congenital heart disease ͉ persistent truncus arteriosus ͉ cardiac neural crest C ongenital heart diseases (CHD) constitute a major percentage of clinically significant birth defects with an estimated prevalence of 4-10 per 1,000 live infants (1). Cardiac outflow tract (OFT) defects are estimated to account for approximately 30% of CHD (2) and usually require an intervention during the first year of life. A variety of OFT defects results from disturbance of the morphogenetic patterning of the anterior pole of the heart, which is essential for the establishment of separate systemic and pulmonary circulations in higher vertebrates. Persistent truncus arteriosus (PTA), which is attributed to missing septation of the OFT, is recognized as the most severe phenotype of OFT defect, and is often associated with an unfavorable prognosis because complete surgical repair is not always possible (3). Although an improved understanding of possible genetic causes would provide insight into the pathogenesis of CHD and allow for better assessment of disease risk, prenatal diagnosis, and critical information for disease prevention, the etiology of most CHD, including OFT defects, remains unknown because of the multifactorial nature of the diseases (4-6).Based on animal studies, it appears that abnormal development of cardiac neural crest (CNC) cells, an ectoderm-derived cell lineage, contributes significantly to the pathology of OFT defects (7-12). During early embryogenesis, CNC cells arise from the dorsal neural tube and migrate ventrally as mesenchymal cells to populate the OFT, where they coalesce to form the aorticopulmonary septum, which divides the single truncus arteriosus (embryonic OFT) into the aorta and pulmonary artery, resulting in the establishment of separate systemic and pulmonary c...

Background Despite the promise shown by stem cells for restoration of cardiac function following myocardial infarction (MI), the poor survival of transplanted cells has been a major issue. Hypoxia inducible factor-1 (HIF-1) is a transcription factor that mediates adaptive responses to ischemia. Here we hypothesize that co-delivery of cardiac progenitor cells (CPCs) with a nonviral minicircle plasmid carrying HIF-1 (MC-HIF1) into the ischemic myocardium can improve the survival of transplanted CPCs. Methods and Results Following MI, CPCs were co-delivered intramyocardially into adult NOD/SCID mice with either saline, MC-GFP, or MC-HIF1 versus MC-HIF1 alone (N=10/group). Bioluminescence imaging (BLI) demonstrated better survival when CPCs were co-delivered with MC-HIF1. Importantly, echocardiography showed mice injected with CPCs + MC-HIF1 had the highest ejection fraction 6 weeks post-MI (57.1±2.6%) followed by MC-HIF1 alone (48.5±2.6%), with no significant protection for CPCs + MC-GFP (44.8±3.3%) compared to saline control (38.7±3.2%, P<0.05). In vitro mechanistic studies confirmed that cardiac endothelial cells (ECs) produced exosomes which were actively internalized by recipient CPCs. Exosomes purified from ECs overexpressing HIF-1 had higher contents of miR-126 and miR-210. These microRNAs activated pro-survival kinases and induced a glycolytic switch in recipient CPCs, giving them increased tolerance when subjected to in vitro hypoxic stress. Inhibiting both of these miRs blocked the protective effects of the exosomes. Conclusions In summary, HIF-1 can be used to modulate the host microenvironment for improving survival of transplanted cells. The exosomal transfer of miRs from host cells to transplanted cells represents a unique mechanism that can be potentially targeted for improving survival of transplanted cells.

Left ventricular non-compaction (LVNC) is the third most prevalent cardiomyopathy in children and its pathogenesis has been associated with the developmental defect of the embryonic myocardium. We show that patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from LVNC patients carrying a mutation in the cardiac transcription factor TBX20 recapitulate a key aspect of the pathological phenotype at the single-cell level and was associated with perturbed transforming growth factor beta (TGFβ) signaling. LVNC iPSC-CMs have decreased proliferative capacity due to abnormal activation of TGFβ signaling. TBX20 regulates the expression of TGFβ signaling modifiers including a known genetic cause of LVNC, PRDM16, and genome editing of PRDM16 caused proliferation defects in iPSC-CMs. Inhibition of TGFβ signaling and genome correction of the TBX20 mutation were sufficient to reverse the disease phenotype. Our study demonstrates that iPSC-CMs are a useful tool for the exploration of pathological mechanisms underlying poorly understood cardiomyopathies including LVNC.

We have demonstrated that acute HIF-1α stabilization using either a pharmacological or genetic approach protected the heart against acute IRI by promoting aerobic glycolysis, decreasing mitochondrial oxidative stress, activating HKII, and inhibiting MPTP opening.

Highlights d TBX5 Clover2 and NKX2-5 TagRFP reporter enables purification of 4 cardiac subpopulations d Different cardiac lineages differentiate into specific cardiac cell types d CORIN is a cell-surface marker for the TBX5+NKX2-5+ subpopulation d Lineage-specific cardiomyocyte subtypes can be used for precise drug testing

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are a powerful platform for uncovering disease mechanisms and assessing drugs for efficacy/toxicity. However, the accuracy with which hiPSC-CMs recapitulate the contractile and remodeling signaling of adult cardiomyocytes is not fully known. We used β-adrenergic receptor (β-AR) signaling as a prototype to determine the evolution of signaling component expression and function during hiPSC-CM maturation. In "early" hiPSC-CMs (less than or equal to d 30), β2-ARs are a primary source of cAMP/PKA signaling. With longer culture, β1-AR signaling increases: from 0% of cAMP generation at d 30 to 56.8 ± 6.6% by d 60. PKA signaling shows a similar increase: 15.7 ± 5.2% (d 30), 49.8 ± 0.5% (d 60), and 71.0 ± 6.1% (d 90). cAMP generation increases 9-fold from d 30 to 60, with enhanced coupling to remodeling pathways (e.g., Akt and Ca(2+)/calmodulin-dependent protein kinase type II) and development of caveolin-mediated signaling compartmentalization. By contrast, cardiotoxicity induced by chronic β-AR stimulation, a major component of heart failure, develops much later: 5% cell death at d 30vs 55% at d 90. Moreover, β-AR maturation can be accelerated by biomechanical stimulation. The differential maturation of β-AR functionalvs remodeling signaling in hiPSC-CMs has important implications for their use in disease modeling and drug testing. We propose that assessment of signaling be added to the indices of phenotypic maturation of hiPSC-CMs.-Jung, G., Fajardo, G., Ribeiro, A. J. S., Kooiker, K. B., Coronado, M., Zhao, M., Hu, D.-Q., Reddy, S., Kodo, K., Sriram, K., Insel, P. A., Wu, J. C., Pruitt, B. L., Bernstein, D. Time-dependent evolution of functionalvs remodeling signaling in induced pluripotent stem cell-derived cardiomyocytes and induced maturation with biomechanical stimulation.

Nearly 8% of the human population carries an inactivating point mutation in the gene that encodes the cardioprotective enzyme aldehyde dehydrogenase 2 (ALDH2). This genetic polymorphism (ALDH2*2) is linked to more severe outcomes from ischemic heart damage and an increased risk of coronary artery disease (CAD), but the underlying molecular bases are unknown. We investigated the ALDH2*2 mechanisms in a human model system of induced pluripotent stem cell–derived cardiomyocytes (iPSC-CMs) generated from individuals carrying the most common heterozygous form of the ALDH2*2 genotype. We showed that the ALDH2*2 mutation gave rise to elevated amounts of reactive oxygen species and toxic aldehydes, thereby inducing cell cycle arrest and activation of apoptotic signaling pathways, especially during ischemic injury. We established that ALDH2 controls cell survival decisions by modulating oxidative stress levels and that this regulatory circuitry was dysfunctional in the loss-of-function ALDH2*2 genotype, causing up-regulation of apoptosis in cardiomyocytes after ischemic insult. These results reveal a new function for the metabolic enzyme ALDH2 in modulation of cell survival decisions. Insight into the molecular mechanisms that mediate ALDH2*2-related increased ischemic damage is important for the development of specific diagnostic methods and improved risk management of CAD and may lead to patient-specific cardiac therapies.

Background Human induced pluripotent stem cells (iPSCs) are attractive candidates for therapeutic use, with the potential to replace deficient cells and to improve functional recovery in injury or disease settings. Here we test the hypothesis that human iPSC-derived cardiomyocytes (iPSC-CMs) can secrete cytokines as a molecular basis to attenuate adverse cardiac remodeling after myocardial infarction (MI). Methods and Results Human iPSCs were generated from skin fibroblasts and differentiated in vitro using a small molecule based protocol. Troponin+ iPSC-CMs were confirmed by immunohistochemistry, quantitative PCR, fluorescence activated cell sorting (FACS), and electrophysiological measurements. Afterwards, 2×106 iPSC-CMs derived from a cell line transduced with a vector expressing firefly luciferase and GFP were transplanted into adult NOD/SCID mice with acute left anterior descending (LAD) ligation. Control animals received PBS injection. Bioluminescence imaging (BLI) showed limited engraftment upon transplantation into ischemic myocardium. However, magnetic resonance imaging (MRI) of animals transplanted with iPSC-CMs showed significant functional improvement and attenuated cardiac remodeling when compared to PBS-treated control animals at day 35 (Ejection fraction: 24.5±1.3 vs. 14.5±1.5%; P<0.05). To understand the underlying molecular mechanism, microfluidic single cell profiling of harvested iPSC-CMs, laser capture microdissection (LCM) of host myocardium, and in vitro ischemia stimulation were used to demonstrate that the iPSC-CMs could release significant levels of pro-angiogenic and anti-apoptotic factors in the ischemic microenvironment. Conclusions Transplantation of human iPSC-CMs into an acute mouse MI model can improve left ventricular function and attenuate cardiac remodeling. Because of limited engraftment, most of the effects are possibly explained by paracrine activity of these cells.