BET inhibition blocks inflammation-induced cardiac dysfunction and SARS-CoV-2 infection.

Cardiac injury and dysfunction occur in COVID-19 patients and increase the risk of mortality. Causes are ill defined but could be through direct cardiac infection and/or inflammation-induced dysfunction. To identify mechanisms and cardio-protective drugs, we use a state-of-the-art pipeline combining human cardiac organoids with phosphoproteomics and single nuclei RNA sequencing. We identify an inflammatory "cytokine-storm", a cocktail of interferon gamma, interleukin 1ß, and poly(I:C), induced diastolic dysfunction. Bromodomain-containing protein 4 is activated along with a viral response that is consistent in both human cardiac organoids (hCOs) and hearts of SARS-CoV-2-infected K18-hACE2 mice. Bromodomain and extraterminal family inhibitors (BETi) recover dysfunction in hCOs and completely prevent cardiac dysfunction and death in a mouse cytokine-storm model. Additionally, BETi decreases transcription of genes in the viral response, decreases ACE2 expression, and reduces SARS-CoV-2 infection of cardiomyocytes. Together, BETi, including the Food and Drug Administration (FDA) breakthrough designated drug, apabetalone, are promising candidates to prevent COVID-19 mediated cardiac damage.

GLA-modified RNA treatment lowers GB3 levels in iPSC-derived cardiomyocytes from Fabry-affected individuals.

Recent studies in non-human model systems have shown therapeutic potential of nucleoside-modified messenger RNA (modRNA) treatments for lysosomal storage diseases. Here, we assessed the efficacy of a modRNA treatment to restore the expression of the galactosidase alpha (GLA), which codes for α-Galactosidase A (α-GAL) enzyme, in a human cardiac model generated from induced pluripotent stem cells (iPSCs) derived from two individuals with Fabry disease. Consistent with the clinical phenotype, cardiomyocytes from iPSCs derived from Fabry-affected individuals showed accumulation of the glycosphingolipid Globotriaosylceramide (GB3), which is an α-galactosidase substrate. Furthermore, the Fabry cardiomyocytes displayed significant upregulation of lysosomal-associated proteins. Upon GLA modRNA treatment, a subset of lysosomal proteins were partially restored to wild-type levels, implying the rescue of the molecular phenotype associated with the Fabry genotype. Importantly, a significant reduction of GB3 levels was observed in GLA modRNA-treated cardiomyocytes, demonstrating that α-GAL enzymatic activity was restored. Together, our results validate the utility of iPSC-derived cardiomyocytes from affected individuals as a model to study disease processes in Fabry disease and the therapeutic potential of GLA modRNA treatment to reduce GB3 accumulation in the heart.

Maturing differentiated human pluripotent stem cells in vitro: methods and challenges.

Human pluripotent stem cells (hPSCs), derived from individuals or genetically modified with disease-related mutations and variants, have revolutionised studies of human disease. Researchers are beginning to exploit the extraordinary potential of stem cell technology to screen for new drugs to treat intractable diseases, ideally without side-effects. However, a major problem is that the differentiated cell types on which these models are based are immature; they resemble fetal and not adult cells. Here, we discuss the nature and hurdles of hPSC maturation, using cardiomyocytes as an example. We review methods used to induce cardiomyocyte maturation in culture and consider remaining challenges for their integration into research on human disease and drug development pipelines.

Kidney organoids reveal redundancy in viral entry pathways during ACE2-dependent SARS-CoV-2 infection.

With a high incidence of acute kidney injury among hospitalized COVID-19 patients, considerable attention has been focussed on whether SARS-CoV-2 specifically targets kidney cells to directly impact renal function, or whether renal damage is primarily an indirect outcome. To date, several studies have utilized kidney organoids to understand the pathogenesis of COVID-19, revealing the ability for SARS-CoV-2 to predominantly infect cells of the proximal tubule (PT), with reduced infectivity following administration of soluble ACE2. However, the immaturity of standard human kidney organoids represents a significant hurdle, leaving the preferred SARS-CoV-2 processing pathway, existence of alternate viral receptors, and the effect of common hypertensive medications on the expression of ACE2 in the context of SARS-CoV-2 exposure incompletely understood. Utilizing a novel kidney organoid model with enhanced PT maturity, genetic- and drug-mediated inhibition of viral entry and processing factors confirmed the requirement for ACE2 for SARS-CoV-2 entry but showed that the virus can utilize dual viral spike protein processing pathways downstream of ACE2 receptor binding. These include TMPRSS- and CTSL/CTSB-mediated non-endosomal and endocytic pathways, with TMPRSS10 likely playing a more significant role in the non-endosomal pathway in renal cells than TMPRSS2. Finally, treatment with the antihypertensive ACE inhibitor, lisinopril, showed negligible impact on receptor expression or susceptibility of renal cells to infection. This study represents the first in-depth characterization of viral entry in stem cell-derived human kidney organoids with enhanced PTs, providing deeper insight into the renal implications of the ongoing COVID-19 pandemic. IMPORTANCE: Utilizing a human iPSC-derived kidney organoid model with improved proximal tubule (PT) maturity, we identified the mechanism of SARS-CoV-2 entry in renal cells, confirming ACE2 as the sole receptor and revealing redundancy in downstream cell surface TMPRSS- and endocytic Cathepsin-mediated pathways. In addition, these data address the implications of SARS-CoV-2 exposure in the setting of the commonly prescribed ACE-inhibitor, lisinopril, confirming its negligible impact on infection of kidney cells. Taken together, these results provide valuable insight into the mechanism of viral infection in the human kidney.

Single Cell Analysis of High-Parameter Histology Images Using Histoflow Cytometry.

Immunofluorescence histology is commonly used to study immune cells in tissues where the number of fluorescence parameters is normally limited to four or less. This makes it impossible to interrogate multiple subsets of immune cells in tissue with the same precision as flow cytometry. The latter, however, dissociates tissues and loses spatial information. To bridge the gap between these technologies, we developed a workflow to expand the number of fluorescence parameters that can be imaged on widely available microscopes. We instituted a method for identifying single cells in tissue and exporting the data for flow cytometry-based analysis. This histoflow cytometry technique successfully separates spectrally overlapping dyes and identifies similar numbers of cells in tissue sections as manual cell counts. Populations identified through flow cytometry-like gating strategies are mapped to the original tissue to spatially localize gated subsets. We applied histoflow cytometry to immune cells in the spinal cords of mice with experimental autoimmune encephalomyelitis. We ascertained that B cells, T cells, neutrophils, and phagocytes differed in their frequencies in CNS immune cell infiltrates and were increased relative to healthy controls. Spatial analysis determined that B cells and T cells/phagocytes preferentially localized to CNS barriers and parenchyma, respectively. By spatially mapping these immune cells, we inferred their preferred interacting partners within immune cell clusters. Overall, we demonstrate the ease and utility of histoflow cytometry, which expands the number of fluorescent channels used in conventional immunofluorescence and enables quantitative cytometry and spatial localization of histological analyses.

Affinity Purification-Mass Spectrometry and Single Fiber Physiology/Proteomics Reveals Mechanistic Insights of C18ORF25.

C18ORF25 was recently shown to be phosphorylated at S67 by AMP-activated protein kinase (AMPK) in the skeletal muscle, following acute exercise in humans. Phosphorylation was shown to improve the ex vivo skeletal muscle contractile function in mice, but our understanding of the molecular mechanisms is incomplete. Here, we profiled the interactome of C18ORF25 in mouse myotubes using affinity purification coupled to mass spectrometry. This analysis included an investigation of AMPK-dependent and S67-dependent protein/protein interactions. Several nucleocytoplasmic and contractile-associated proteins were identified, which revealed a subset of GTPases that associate with C18ORF25 in an AMPK- and S67 phosphorylation-dependent manner. We confirmed that C18ORF25 is localized to the nucleus and the contractile apparatus in the skeletal muscle. Mice lacking C18Orf25 display defects in calcium handling specifically in fast-twitch muscle fibers. To investigate these mechanisms, we developed an integrated single fiber physiology and single fiber proteomic platform. The approach enabled a detailed assessment of various steps in the excitation-contraction pathway including SR calcium handling and force generation, followed by paired single fiber proteomic analysis. This enabled us to identify >700 protein/phenotype associations and 36 fiber-type specific differences, following loss of C18Orf25. Taken together, our data provide unique insights into the function of C18ORF25 and its role in skeletal muscle physiology.

Impact of lung cancer screening on stage migration and mortality among the national Veterans Health Administration population with lung cancer.

BACKGROUND: Despite randomized trials demonstrating a mortality benefit to low-dose computed tomography screening to detect lung cancer, uptake of lung cancer screening (LCS) has been slow, and the benefits of screening remain unclear in clinical practice. METHODS: This study aimed to assess the impact of screening among patients in the Veterans Health Administration (VA) health care system diagnosed with lung cancer between 2011 and 2018. Lung cancer stage at diagnosis, lung cancer-specific survival, and overall survival between patients with cancer who did and did not receive screening before diagnosis were evaluated. We used Cox regression modeling and inverse propensity weighting analyses with lead time bias adjustment to correlate LCS exposure with patient outcomes. RESULTS: Of 57,919 individuals diagnosed with lung cancer in the VA system between 2011 and 2018, 2167 (3.9%) underwent screening before diagnosis. Patients with screening had higher rates of stage I diagnoses (52% vs. 27%; p ≤ .0001) compared to those who had no screening. Screened patients had improved 5-year overall survival rates (50.2% vs. 27.9%) and 5-year lung cancer-specific survival (59.0% vs. 29.7%) compared to unscreened patients. Among screening-eligible patients who underwent National Comprehensive Cancer Network guideline-concordant treatment, screening resulted in substantial reductions in all-cause mortality (adjusted hazard ratio [aHR], 0.79; 95% confidence interval [CI], 0.67-0.92; p = .003) and lung-specific mortality (aHR, 0.61; 95% CI, 0.50-0.74; p < .001). CONCLUSIONS: While LCS uptake remains limited, screening was associated with earlier stage diagnoses and improved survival. This large national study corroborates the value of LCS in clinical practice; efforts to widely adopt this vital intervention are needed.

Outcomes after definitive radiation therapy for localized prostate cancer in a national health care delivery system.

PURPOSE: Accurate information regarding real-world outcomes after contemporary radiation therapy for localized prostate cancer is important for shared decision-making. Clinically relevant end points at 10 years among men treated within a national health care delivery system were examined. METHODS: National administrative, cancer registry, and electronic health record data were used for patients undergoing definitive radiation therapy with or without concurrent androgen deprivation therapy within the Veterans Health Administration from 2005 to 2015. National Death Index data were used through 2019 for overall and prostate cancer-specific survival and identified date of incident metastatic prostate cancer using a validated natural language processing algorithm. Metastasis-free, prostate cancer-specific, and overall survival using Kaplan-Meier methods were estimated. RESULTS: Among 41,735 men treated with definitive radiation therapy, the median age at diagnosis was 65 years and median follow-up was 8.7 years. Most had intermediate (42%) and high-risk (33%) disease, with 40% receiving androgen deprivation therapy as part of initial therapy. Unadjusted 10-year metastasis-free survival was 96%, 92%, and 80% for low-, intermediate-, and high-risk disease. Similarly, unadjusted 10-year prostate cancer-specific survival was 98%, 97%, and 90% for low-, intermediate-, and high-risk disease. The unadjusted overall survival was lower across increasing disease risk categories at 77%, 71%, and 62% for low-, intermediate-, and high-risk disease (p < .001). CONCLUSIONS: These data provide population-based 10-year benchmarks for clinically relevant end points, including metastasis-free survival, among patients with localized prostate cancer undergoing radiation therapy using contemporary techniques. The survival rates for high-risk disease in particular suggest that outcomes have recently improved.

ß-Catenin drives distinct transcriptional networks in proliferative and nonproliferative cardiomyocytes.

The inability of the adult mammalian heart to regenerate represents a fundamental barrier in heart failure management. By contrast, the neonatal heart retains a transient regenerative capacity, but the underlying mechanisms for the developmental loss of cardiac regenerative capacity in mammals are not fully understood. Wnt/ß-catenin signalling has been proposed as a key cardioregenerative pathway driving cardiomyocyte proliferation. Here, we show that Wnt/ß-catenin signalling potentiates neonatal mouse cardiomyocyte proliferation in vivo and immature human pluripotent stem cell-derived cardiomyocyte (hPSC-CM) proliferation in vitro By contrast, Wnt/ß-catenin signalling in adult mice is cardioprotective but fails to induce cardiomyocyte proliferation. Transcriptional profiling and chromatin immunoprecipitation sequencing of neonatal mouse and hPSC-CMs revealed a core Wnt/ß-catenin-dependent transcriptional network governing cardiomyocyte proliferation. By contrast, ß-catenin failed to re-engage this neonatal proliferative gene network in the adult heart despite partial transcriptional re-activation of a neonatal glycolytic gene programme. These findings suggest that ß-catenin might be repurposed from regenerative to protective functions in the adult heart in a developmental process dependent on the metabolic status of cardiomyocytes.

3D-cardiomics: A spatial transcriptional atlas of the mammalian heart.

Understanding the spatial gene expression and regulation in the heart is key to uncovering its developmental and physiological processes, during homeostasis and disease. Numerous techniques exist to gain gene expression and regulation information in organs such as the heart, but few utilize intuitive true-to-life three-dimensional representations to analyze and visualise results. Here we combined transcriptomics with 3D-modelling to interrogate spatial gene expression in the mammalian heart. For this, we microdissected and sequenced transcriptome-wide 18 anatomical sections of the adult mouse heart. Our study has unveiled known and novel genes that display complex spatial expression in the heart sub-compartments. We have also created 3D-cardiomics, an interface for spatial transcriptome analysis and visualization that allows the easy exploration of these data in a 3D model of the heart. 3D-cardiomics is accessible from http://3d-cardiomics.erc.monash.edu/.

Sex-Specific Control of Human Heart Maturation by the Progesterone Receptor.

BACKGROUND: Despite in-depth knowledge of the molecular mechanisms controlling embryonic heart development, little is known about the signals governing postnatal maturation of the human heart. METHODS: Single-nucleus RNA sequencing of 54 140 nuclei from 9 human donors was used to profile transcriptional changes in diverse cardiac cell types during maturation from fetal stages to adulthood. Bulk RNA sequencing and the Assay for Transposase-Accessible Chromatin using sequencing were used to further validate transcriptional changes and to profile alterations in the chromatin accessibility landscape in purified cardiomyocyte nuclei from 21 human donors. Functional validation studies of sex steroids implicated in cardiac maturation were performed in human pluripotent stem cell-derived cardiac organoids and mice. RESULTS: Our data identify the progesterone receptor as a key mediator of sex-dependent transcriptional programs during cardiomyocyte maturation. Functional validation studies in human cardiac organoids and mice demonstrate that the progesterone receptor drives sex-specific metabolic programs and maturation of cardiac contractile properties. CONCLUSIONS: These data provide a blueprint for understanding human heart maturation in both sexes and reveal an important role for the progesterone receptor in human heart development.

Alpha-protein kinase 3 (ALPK3) truncating variants are a cause of autosomal dominant hypertrophic cardiomyopathy.

AIMS: The aim of this study was to determine the frequency of heterozygous truncating ALPK3 variants (ALPK3tv) in patients with hypertrophic cardiomyopathy (HCM) and confirm their pathogenicity using burden testing in independent cohorts and family co-segregation studies. METHODS AND RESULTS: In a discovery cohort of 770 index patients with HCM, 12 (1.56%) were heterozygous for ALPK3tv [odds ratio(OR) 16.11, 95% confidence interval (CI) 7.94-30.02, P = 8.05e-11] compared to the Genome Aggregation Database (gnomAD) population. In a validation cohort of 2047 HCM probands, 32 (1.56%) carried heterozygous ALPK3tv (OR 16.17, 95% CI 10.31-24.87, P < 2.2e-16, compared to gnomAD). Combined logarithm of odds score in seven families with ALPK3tv was 2.99. In comparison with a cohort of genotyped patients with HCM (n = 1679) with and without pathogenic sarcomere gene variants (SP+ and SP-), ALPK3tv carriers had a higher prevalence of apical/concentric patterns of hypertrophy (60%, P < 0.001) and of a short PR interval (10%, P = 0.009). Age at diagnosis and maximum left ventricular wall thickness were similar to SP- and left ventricular systolic impairment (6%) and non-sustained ventricular tachycardia (31%) at baseline similar to SP+. After 5.3 ± 5.7 years, 4 (9%) patients with ALPK3tv died of heart failure or had cardiac transplantation (log-rank P = 0.012 vs. SP- and P = 0.425 vs. SP+). Imaging and histopathology showed extensive myocardial fibrosis and myocyte vacuolation. CONCLUSIONS: Heterozygous ALPK3tv are pathogenic and segregate with a characteristic HCM phenotype.

The Australia and New Zealand Cardio-Oncology Registry: evaluation of chemotherapy-related cardiotoxicity in a national cohort of paediatric cancer patients.

Cancer therapy related cardiac dysfunction (CTRCD) is an area of increasing focus, particularly during the survivorship period, for paediatric, adolescent and adult cancer survivors. With the advent of immunotherapy and targeted therapy, there is a new set of mechanisms from which paediatric and young adult patients with cancer may suffer cardiovascular injury. Furthermore, cardiovascular disease is the leading cause of morbidity and mortality in the survivorship period. The recently established Australian Cardio-Oncology Registry is the largest and only population-based cardiotoxicity database of paediatric and adolescent and young adult oncology patients in the world, and the first paediatric registry that will document cardiotoxicity caused by chemotherapy and novel targeted therapies using a prospective approach. The database is designed for comprehensive data collection and evaluation of the Australian practice in terms of diagnosis and management of CTRCD. Using the Australian Cardio-Oncology Registry critical clinical information will be collected regarding predisposing factors for the development of CTRCD, the rate of subclinical left ventricular dysfunction and transition to overt heart failure, further research into protectant molecules against cardiac dysfunction and aid in the discovery of which genetic variants predispose to CTRCD. A health economic arm of the study will assess the cost/benefit of both the registry and cardio-oncology clinical implementation. Finally, an imaging arm will establish if exercise cardiac magnetic resonance imaging and VO2 max testing is a more sensitive predictor of cardiac reserve in paediatric and adolescent and young adult oncology patients exposed to cardiac toxic therapies.

Modelling Mitochondrial Disease in Human Pluripotent Stem Cells: What Have We Learned?

Mitochondrial diseases disrupt cellular energy production and are among the most complex group of inherited genetic disorders. Affecting approximately 1 in 5000 live births, they are both clinically and genetically heterogeneous, and can be highly tissue specific, but most often affect cell types with high energy demands in the brain, heart, and kidneys. There are currently no clinically validated treatment options available, despite several agents showing therapeutic promise. However, modelling these disorders is challenging as many non-human models of mitochondrial disease do not completely recapitulate human phenotypes for known disease genes. Additionally, access to disease-relevant cell or tissue types from patients is often limited. To overcome these difficulties, many groups have turned to human pluripotent stem cells (hPSCs) to model mitochondrial disease for both nuclear-DNA (nDNA) and mitochondrial-DNA (mtDNA) contexts. Leveraging the capacity of hPSCs to differentiate into clinically relevant cell types, these models permit both detailed investigation of cellular pathomechanisms and validation of promising treatment options. Here we catalogue hPSC models of mitochondrial disease that have been generated to date, summarise approaches and key outcomes of phenotypic profiling using these models, and discuss key criteria to guide future investigations using hPSC models of mitochondrial disease.

Development of a human cardiac organoid injury model reveals innate regenerative potential.

The adult human heart possesses a limited regenerative potential following an ischemic event, and undergoes a number of pathological changes in response to injury. Although cardiac regeneration has been documented in zebrafish and neonatal mouse hearts, it is currently unknown whether the immature human heart is capable of undergoing complete regeneration. Combined progress in pluripotent stem cell differentiation and tissue engineering has facilitated the development of human cardiac organoids (hCOs), which resemble fetal heart tissue and can be used to address this important knowledge gap. This study aimed to characterize the regenerative capacity of immature human heart tissue in response to injury. Following cryoinjury with a dry ice probe, hCOs exhibited an endogenous regenerative response with full functional recovery 2 weeks after acute injury. Cardiac functional recovery occurred in the absence of pathological fibrosis or cardiomyocyte hypertrophy. Consistent with regenerative organisms and neonatal human hearts, there was a high basal level of cardiomyocyte proliferation, which may be responsible for the regenerative capacity of the hCOs. This study suggests that immature human heart tissue has an intrinsic capacity to regenerate.

Exercise cardiovascular magnetic resonance reveals reduced cardiac reserve in pediatric cancer survivors with impaired cardiopulmonary fitness.

BACKGROUND: Pediatric cancer survivors are at increased risk of cardiac dysfunction and heart failure. Reduced peak oxygen consumption (peak VO2) is associated with impaired cardiac reserve (defined as the increase in cardiac function from rest to peak exercise) and heart failure risk, but it is unclear whether this relationship exists in pediatric cancer survivors. This study sought to investigate the presence of reduced peak VO2 in pediatric cancer survivors with increased risk of heart failure, and to assess its relationship with resting cardiac function and cardiac haemodynamics and systolic function during exercise. METHODS: Twenty pediatric cancer survivors (8-24 years; 10 male) treated with anthracycline chemotherapy ± radiation underwent cardiopulmonary exercise testing to quantify peak VO2, with a value < 85% of predicted defined as impaired peak VO2. Resting cardiac function was assessed using 2- and 3-dimensional echocardiography, with cardiac reserve quantified from resting and peak exercise heart rate, stroke volume index (SVI) and cardiac index (CI) using exercise cardiovascular magnetic resonance (CMR). RESULTS: Twelve of 20 survivors (60%) had reduced peak VO2 (70 ± 16% vs. 97 ± 14% of age and gender predicted). There were no differences in echocardiographic or CMR measurements of resting cardiac function between survivors with normal or impaired peak VO2. However, those with reduced peak VO2 had diminished cardiac reserve, with a lesser increase in CI and SVI during exercise (Interaction P < 0.01 for both), whilst the heart rate response was similar (P = 0.71). CONCLUSIONS: Whilst exercise intolerance is common among pediatric cancer survivors, it is poorly explained by resting measures of cardiac function. In contrast, impaired exercise capacity is associated with impaired haemodynamics and systolic functional reserve measured during exercise. Consequently, measures of cardiopulmonary fitness and cardiac reserve may aid in early identification of survivors with heightened risk of long-term heart failure.

Functional screening in human cardiac organoids reveals a metabolic mechanism for cardiomyocyte cell cycle arrest.

The mammalian heart undergoes maturation during postnatal life to meet the increased functional requirements of an adult. However, the key drivers of this process remain poorly defined. We are currently unable to recapitulate postnatal maturation in human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs), limiting their potential as a model system to discover regenerative therapeutics. Here, we provide a summary of our studies, where we developed a 96-well device for functional screening in human pluripotent stem cell-derived cardiac organoids (hCOs). Through interrogation of >10,000 organoids, we systematically optimize parameters, including extracellular matrix (ECM), metabolic substrate, and growth factor conditions, that enhance cardiac tissue viability, function, and maturation. Under optimized maturation conditions, functional and molecular characterization revealed that a switch to fatty acid metabolism was a central driver of cardiac maturation. Under these conditions, hPSC-CMs were refractory to mitogenic stimuli, and we found that key proliferation pathways including ß-catenin and Yes-associated protein 1 (YAP1) were repressed. This proliferative barrier imposed by fatty acid metabolism in hCOs could be rescued by simultaneous activation of both ß-catenin and YAP1 using genetic approaches or a small molecule activating both pathways. These studies highlight that human organoids coupled with higher-throughput screening platforms have the potential to rapidly expand our knowledge of human biology and potentially unlock therapeutic strategies.

Isolation and characterization of ventricular-like cells derived from NKX2-5eGFP/w and MLC2vmCherry/w double knock-in human pluripotent stem cells.

Human pluripotent stem cell (hPSC)-derived cardiomyocytes (CMs) are a promising source for cell transplantation into the damaged heart, which has limited regenerative ability. Many methods have been developed to obtain large amounts of functional CMs from hPSCs for therapeutic applications. However, during the differentiation process, a mixed population of various cardiac cells, including ventricular, atrial, and pacemaker cells, is generated, which hampers the proper functional analysis and evaluation of cell properties. Here, we established NKX2-5eGFP/w and MLC2vmCherry/w hPSC double knock-ins that allow for labeling, tracing, purification, and analysis of the development of ventricular cells from early to late stages. As with the endogenous transcriptional activities of these genes, MLC2v-mCherry expression following NKX2-5-eGFP expression was observed under previously established culture conditions, which mimic the in vivo cardiac developmental process. Patch-clamp and microelectrode array electrophysiological analyses showed that the NKX2-5 and MLC2v double-positive cells possess ventricular-like properties. The results demonstrate that the NKX2-5eGFP/w and MLC2vmCherry/w hPSCs provide a powerful model system to capture region-specific cardiac differentiation from early to late stages. Our study would facilitate subtype-specific cardiac development and functional analysis using the hPSC-derived sources.

3D aggregate culture improves metabolic maturation of human pluripotent stem cell derived cardiomyocytes.

Three-dimensional (3D) cultures of human pluripotent stem cell derived cardiomyocytes (hPSC-CMs) hold great promise for drug discovery, providing a better approximation to the in vivo physiology over standard two-dimensional (2D) monolayer cultures. However, the transition of CM differentiation protocols from 2D to 3D cultures is not straightforward. In this work, we relied on the aggregation of hPSC-derived cardiac progenitors and their culture under agitated conditions to generate highly pure cardiomyocyte aggregates. Whole-transcriptome analysis and 13 C-metabolic flux analysis allowed to demonstrate at both molecular and fluxome levels that such 3D culture environment enhances metabolic maturation of hiPSC-CMs. When compared to 2D, 3D cultures of hiPSC-CMs displayed down-regulation of genes involved in glycolysis and lipid biosynthesis and increased expression of genes involved in OXPHOS. Accordingly, 3D cultures of hiPSC-CMs had lower fluxes through glycolysis and fatty acid synthesis and increased TCA-cycle activity. Importantly, we demonstrated that the 3D culture environment reproducibly improved both CM purity and metabolic maturation across different hPSC lines, thereby providing a robust strategy to derive enriched hPSC-CMs with metabolic features closer to that of adult CMs.