Abstract
Loss of Bcl2-associated athanogene 3 (BAG3) is associated with dilated cardiomyopathy (DCM). BAG3 regulates sarcomere protein turnover in cardiomyocytes; however, the function of BAG3 in other cardiac cell types is understudied. In this study, we used an isogenic pair of BAG3-knockout and wild-type human induced pluripotent stem cells (hiPSCs) to interrogate the role of BAG3 in hiPSC-derived cardiac fibroblasts (CFs). Analysis of cell type–specific conditional knockout engineered heart tissues revealed an essential contribution of CF BAG3 to contractility and cardiac fibrosis, recapitulating the phenotype of DCM. In BAG3–/– CFs, we observed an increased sensitivity to TGF-β signaling and activation of a fibrogenic response when cultured at physiological stiffness (8 kPa). Mechanistically, we showed that loss of BAG3 increased transforming growth factor-β receptor 2 (TGFBR2) levels by directly binding TGFBR2 and mediating its ubiquitination and proteasomal degradation. To further validate these results, we performed single-nucleus RNA sequencing of cardiac tissue from DCM patients carrying pathogenic BAG3 variants. BAG3 pathogenic variants increased fibrotic gene expression in CFs. Together, these results extend our understanding of the roles of BAG3 in heart disease beyond the cardiomyocyte-centric view and highlight the ability of tissue-engineered hiPSC models to elucidate cell type–specific aspects of cardiac disease.
Authors
Bryan Z. Wang, Margaretha A.J. Morsink, Seong Won Kim, Lori J. Luo, Xiaokan Zhang, Rajesh Kumar Soni, Roberta I. Lock, Jenny Rao, Youngbin Kim, Anran Zhang, Meraj Neyazi, Joshua M. Gorham, Yuri Kim, Kemar Brown, Daniel M. DeLaughter, Qi Zhang, Barbara McDonough, Josephine M. Watkins, Katherine M. Cunningham, Gavin Y. Oudit, Barry M. Fine, Christine E. Seidman, Jonathan G. Seidman, Gordana Vunjak-Novakovic
Abstract
Heterozygous truncating variants in the sarcomere protein titin (TTN) are the most common genetic cause of heart failure. To understand mechanisms that regulate abundant cardiomyocyte TTN expression we characterized highly conserved intron 1 sequences that exhibited dynamic changes in chromatin accessibility during differentiation of human cardiomyocytes from induced pluripotent stem cells (hiPSC-CMs). Homozygous deletion of these sequences in mice caused embryonic lethality while heterozygous mice demonstrated allele-specific reduction in Ttn expression. A 296 bp fragment of this element, denoted E1, was sufficient to drive expression of a reporter gene in hiPSC-CMs. Deletion of E1 downregulated TTN expression, impaired sarcomerogenesis, and decreased contractility in hiPSC-CMs. Site-directed mutagenesis of predicted NKX2-5- and MEF2-binding sites within E1 abolished its transcriptional activity. Embryonic mice expressing E1 reporter gene constructs validated in vivo cardiac-specific activity of E1 and the requirement for NKX2-5 and MEF2 binding sequences. Moreover, isogenic hiPSC-CMs containing a rare E1 variant in the predicted MEF2 binding motif that was identified in a patient with unexplained DCM showed reduced TTN expression. Together these discoveries define an essential, functional enhancer that regulates TTN expression. Manipulation of this element may advance therapeutic strategies to treat DCM caused by TTN haploinsufficiency.
Authors
Yuri Kim, Seong Won Kim, David Saul, Meraj Neyazi, Manuel Schmid, Hiroko Wakimoto, Neil Slaven, Joshua H. Lee, Olivia G. Layton, Lauren K. Wasson, Justin H. Letendre, Feng Xiao, Jourdan K. Ewoldt, Konstantinos Gkatzis, Peter Sommer, Bénédicte Gobert, Nicolas Wiest-Daesslé, Quentin McAfee, Nandita Singhal, Mingyue Lun, Joshua M. Gorham, Zoltan Arany, Arun Sharma, Christopher N. Toepfer, Gavin Y. Oudit, William T. Pu, Diane E. Dickel, Len A. Pennacchio, Axel Visel, Christopher S. Chen, J.G. Seidman, Christine E. Seidman
Abstract
Previous studies highlight the potential for sodium-glucose cotransporter type 2 (SGLT2) inhibitors (SGLT2i) to exert cardioprotective effects in heart failure by increasing plasma ketones and shifting myocardial fuel utilization toward ketone oxidation. However, SGLT2i have multiple in vivo effects and the differential impact of SGLT2i treatment and ketone supplementation on cardiac metabolism remains unclear. Here, using gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–tandem mass spectrometry (LC-MS/MS) methodology combined with infusions of [13C6]glucose or [13C4]βOHB, we demonstrate that acute SGLT2 inhibition with dapagliflozin shifts relative rates of myocardial mitochondrial metabolism toward ketone oxidation, decreasing pyruvate oxidation with little effect on fatty acid oxidation in awake rats. Shifts in myocardial ketone oxidation persisted when plasma glucose levels were maintained. In contrast, acute βOHB infusion similarly augmented ketone oxidation, but markedly reduced fatty acid oxidation and did not alter glucose uptake or pyruvate oxidation. After inducing heart failure, dapagliflozin increased relative rates of ketone and fatty acid oxidation, but decreased pyruvate oxidation. Dapagliflozin increased mitochondrial redox and reduced myocardial oxidative stress in heart failure, which was associated with improvements in left ventricular ejection fraction after 3 weeks of treatment. Thus, SGLT2i have pleiotropic effects on systemic and heart metabolism, which are distinct from ketone supplementation and may contribute to the long-term cardioprotective benefits of SGLT2i.
Authors
Leigh Goedeke, Yina Ma, Rafael C. Gaspar, Ali Nasiri, Jieun Lee, Dongyan Zhang, Katrine Douglas Galsgaard, Xiaoyue Hu, Jiasheng Zhang, Nicole Guerrera, Xiruo Li, Traci LaMoia, Brandon T. Hubbard, Sofie Haedersdal, Xiaohong Wu, John Stack, Sylvie Dufour, Gina Marie Butrico, Mario Kahn, Rachel J. Perry, Gary W. Cline, Lawrence H. Young, Gerald I. Shulman
Abstract
Cardiac endothelial cells are essential for heart development, and disruption of this process can lead to congenital heart disease (CHD). However, how miRNAs influence cardiac endothelial cells in CHD remains unclear. This study identified elevated miR-187 expression in embryonic heart endothelial cells from CHD fetuses. Using a conditional knock-in model, we showed that increased miR-187 levels in embryonic endothelial cells induce CHD in homozygous fetal mice, closely mirroring human CHD. Mechanistically, miR-187 targets NIPBL, which is responsible for recruiting the cohesin complex and facilitating chromatin accessibility. Consequently, the endothelial cell-specific upregulation of miR-187 inhibited NIPBL, leading to reduced chromatin accessibility and impaired gene expression, which hindered endothelial cell development and ultimately caused heart septal defects and reduced heart size both in vitro and in vivo. Importantly, exogenous miR-187 expression in human cardiac organoids mimicked developmental defects in the cardiac endothelial cells, reversible by NIPBL replenishment. Our findings establish the miR-187/NIPBL axis as a potent regulator that inhibits cardiac endothelial cell development by attenuating the transcription of numerous endothelial genes, with our mouse and human cardiac organoid models effectively replicating severe defects from minor perturbations. This discovery suggests that targeting the miR-187/NIPBL pathway could offer a promising therapeutic approach for CHD.
Authors
Chao Li, Zizheng Tan, Hongdou Li, Xiaoying Yao, Chuyue Peng, Yue Qi, Bo Wu, Tong-Jin Zhao, Chengtao Li, Jianfeng Shen, Hongyan Wang
Abstract
Authors
Jeffrey D. Steimle, Yi Zhao, Fansen Meng, Mikaela E. Taylor, Diwakar Turaga, Iki Adachi, Xiao Li, James F. Martin
Abstract
Myocardial infarction (MI) is characterized by massive cardiomyocytes death and cardiac dysfunction, and effective therapies to achieve cardioprotection are sorely needed. Here we reported that flavin containing monooxygenase 2 (FMO2) level was markedly increased in cardiomyocytes both in ex vivo and in vivo models of ischemia injury. Genetic deletion of FMO2 resulted in reduced cardiomyocyte survival and enhanced cardiac dysfunction, whereas cardiomyocyte-specific FMO2 overexpression exerted a protective effect in infarcted rat hearts. Mechanistically, FMO2 inhibited the activation of endoplasmic reticulum (ER) stress-induced apoptotic proteins, including caspase 12 and C/EBP homologous protein (CHOP), by down-regulating unfolded protein response (UPR) pathway. Furthermore, we identified FMO2 as a chaperone that catalyzed disulfide-bond formation in unfolded/misfolded proteins through its GVSG motif. GVSG-mutated FMO2 failed to catalyze disulfide-bond formation and lost its protection against ER stress and cardiomyocyte death. Finally, we demonstrated the protective effect of FMO2 in human induced pluripotent stem cell–derived cardiomyocyte (hiPSC-CM) model. Collectively, this study highlights FMO2 as a key modulator of oxidative protein folding in cardiomyocytes and underscores its therapeutic potential for treating ischemic heart disease.
Authors
Qingnian Liu, Jiniu Huang, Hao Ding, Yue Tao, Jinliang Nan, Changchen Xiao, Yingchao Wang, Rongrong Wu, Cheng Ni, Zhiwei Zhong, Wei Zhu, Jinghai Chen, Chenyun Zhang, Xiao He, Danyang Xiong, Xinyang Hu, Jian'an Wang
Abstract
Hypertrophic and dilated cardiomyopathies (HCM and DCM, respectively) are inherited disorders that may be caused by mutations to the same sarcomeric protein but have completely different clinical phenotypes. The precise mechanisms by which point mutations within the same gene bring about phenotypic diversity remain unclear. Our objective has been to develop a mechanistic explanation of diverging phenotypes in two TPM1 mutations, E62Q (HCM) and E54K (DCM). Drawing on data from the literature and experiments with stem cell-derived cardiomyocytes expressing the TPM1 mutations of interest, we constructed computational simulations that provide plausible explanations of the distinct muscle contractility caused by each variant. In E62Q, increased calcium sensitivity and hypercontractility was explained most accurately by a reduction in effective molecular stiffness of tropomyosin and alterations in its interactions with the actin thin filament that favor the ‘closed’ regulatory state. By contrast, the E54K mutation appeared to act via long-range allosteric interactions to increase the association rate of the C-terminal troponin I mobile domain to tropomyosin/actin. These mutation-linked molecular events produced diverging alterations in gene expression that can be observed in human engineered heart tissues. Modulators of myosin activity confirmed our proposed mechanisms by rescuing normal contractile behavior in accordance with predictions.
Authors
Saiti S. Halder, Michael J. Rynkiewicz, Lynne Kim, Meaghan Barry, Ahmed G.A. Zied, Lorenzo R. Sewanan, Jonathan A. Kirk, Jeffrey R. Moore, William Lehman, Stuart G. Campbell
Abstract
Fibrosis represents the uncontrolled replacement of parenchymal tissue with extracellular matrix (ECM) produced by myofibroblasts. While genetic fate-tracing and single-cell RNA-Seq technologies have helped elucidate fibroblast heterogeneity and ontogeny beyond fibroblast to myofibroblast differentiation, newly identified fibroblast populations remain ill defined, with respect to both the molecular cues driving their differentiation and their subsequent role in fibrosis. Using an unbiased approach, we identified the metalloprotease ADAMTS12 as a fibroblast-specific gene that is strongly upregulated during active fibrogenesis in humans and mice. Functional in vivo KO studies in mice confirmed that Adamts12 was critical during fibrogenesis in both heart and kidney. Mechanistically, using a combination of spatial transcriptomics and expression of catalytically active or inactive ADAMTS12, we demonstrated that the active protease of ADAMTS12 shaped ECM composition and cleaved hemicentin 1 (HMCN1) to enable the activation and migration of a distinct injury-responsive fibroblast subset defined by aberrant high JAK/STAT signaling.
Authors
Konrad Hoeft, Lars Koch, Susanne Ziegler, Ling Zhang, Steffen Luetke, Maria C. Tanzer, Debashish Mohanta, David Schumacher, Felix Schreibing, Qingqing Long, Hyojin Kim, Barbara M. Klinkhammer, Carla Schikarski, Sidrah Maryam, Mathijs Baens, Juliane Hermann, Sarah Krieg, Fabian Peisker, Laura De Laporte, Gideon J.L. Schaefer, Sylvia Menzel, Joachim Jankowski, Benjamin D. Humphreys, Adam Wahida, Rebekka K. Schneider, Matthias Versele, Peter Boor, Matthias Mann, Gerhard Sengle, Sikander Hayat, Rafael Kramann
Abstract
BACKGROUND. Recent studies conducted in COVID-19 survivors suggest that SARS-CoV-2 infection is associated with an increased risk of dyslipidemia. However, it remains unclear whether this augmented risk is confirmed in the general population and how this phenomenon is impacting the overall burden of cardiometabolic diseases. METHODS. To address these aspects, we conducted a 6-year longitudinal study to examine the broader effects of COVID-19 on dyslipidemia incidence within a real-world population (228,266 subjects) residing in Naples, Southern Italy. The pre-COVID-19 and the COVID-19 groups were balanced for demographic and clinical factors using propensity score matching. RESULTS. Our analysis spans over a period of three years during the pandemic (2020–2022), comparing dyslipidemia incidence with pre-pandemic data (2017–2019), with a follow-up time of at least 1,095 days corresponding to 21,349,215 person-years. During the COVID-19 period we detected an increased risk of developing any dyslipidemia when compared with the pre-COVID-19 triennium (OR = 1.29, 95% CI 1.19–1.39). Importantly, these estimates were adjusted for comorbidities by a multivariate analysis. CONCLUSIONS. Taken together, our data reveal a notable rise in dyslipidemia incidence amid the COVID-19 pandemic, suggesting to establish specialized clinical monitoring protocols for COVID-19 survivors to mitigate the risk of dyslipidemia development.
Authors
Valentina Trimarco, Raffaele Izzo, Stanislovas S. Jankauskas, Mario Fordellone, Giuseppe Signoriello, Maria Virginia Manzi, Maria Lembo, Paola Gallo, Giovanni Esposito, Roberto Piccinocchi, Francesco Rozza, Carmine Morisco, Pasquale Mone, Gaetano Piccinocchi, Fahimeh Varzideh, Bruno Trimarco, Gaetano Santulli
Abstract
Cardiac macrophages/monocytes participate in maintaining homeostasis and orchestrating cardiac responses upon injury. However, the function of specific macrophage/monocyte subtypes and the related cell fate commitment mechanisms remain elusive in regenerative and nonregenerative hearts due to their cellular heterogeneities. Using spatiotemporal single-cell epigenomic analysis of cardiac macrophages/monocytes in regenerative (P1) and nonregenerative (P10) mouse hearts post injury, we found that P1 hearts accumulate reparative Arg1+ macrophages, while proinflammatory S100a9+Ly6c+ monocytes are uniquely abundant during nonregenerative remodeling. Moreover, blocking chemokine CXCR2 to inhibit the specification of the S100a9+Ly6c+-biased inflammatory fate in P10 hearts resulted in elevated wound repair responses and marked improvements in cardiac function after injury. Single-cell RNA-seq further confirmed an increased Arg1+ macrophage subpopulation after CXCR2 blockade, which was accomplished by increased expression of wound repair-related genes and reduced expression of proinflammatory genes. Collectively, our findings provide instructive insights into the molecular mechanisms underlying the function and fate specification of heterogeneous macrophages/monocytes during cardiac repair and identify potential therapeutic targets for myocardial infarction.
Authors
Mingzhu Fu, Shengtao Jia, Longhui Xu, Xin Li, Yufang Lv, Yulong Zhong, Shanshan Ai
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)