Browsing by Author "Mayr, Manuel"

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    Fibroblast GATA-4 and GATA-6 promote myocardial adaptation to pressure overload by enhancing cardiac angiogenesis
    (Springer, 2021-04-19) Dittrich, Gesine M.; Froese, Natali; Wang, Xue; Kroeger, Hannah; Wang, Honghui; Szaroszyk, Malgorzata; Malek‑Mohammadi, Mona; Cordero, Julio; Keles, Merve; Korf‑Klingebiel, Mortimer; Wollert, Kai C.; Geffers, Robert; Mayr, Manuel; Conway, Simon J.; Dobreva, Gergana; Bauersachs, Johann; Heineke, Joerg; Pediatrics, School of Medicine
    Heart failure due to high blood pressure or ischemic injury remains a major problem for millions of patients worldwide. Despite enormous advances in deciphering the molecular mechanisms underlying heart failure progression, the cell-type specific adaptations and especially intercellular signaling remain poorly understood. Cardiac fibroblasts express high levels of cardiogenic transcription factors such as GATA-4 and GATA-6, but their role in fibroblasts during stress is not known. Here, we show that fibroblast GATA-4 and GATA-6 promote adaptive remodeling in pressure overload induced cardiac hypertrophy. Using a mouse model with specific single or double deletion of Gata4 and Gata6 in stress activated fibroblasts, we found a reduced myocardial capillarization in mice with Gata4/6 double deletion following pressure overload, while single deletion of Gata4 or Gata6 had no effect. Importantly, we confirmed the reduced angiogenic response using an in vitro co-culture system with Gata4/6 deleted cardiac fibroblasts and endothelial cells. A comprehensive RNA-sequencing analysis revealed an upregulation of anti-angiogenic genes upon Gata4/6 deletion in fibroblasts, and siRNA mediated downregulation of these genes restored endothelial cell growth. In conclusion, we identified a novel role for the cardiogenic transcription factors GATA-4 and GATA-6 in heart fibroblasts, where both proteins act in concert to promote myocardial capillarization and heart function by directing intercellular crosstalk.
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    Gene editing reverses arrhythmia susceptibility in humanized PLN-R14del mice: modelling a European cardiomyopathy with global impact
    (Oxford University Press, 2022) Dave, Jaydev; Raad, Nour; Mittal, Nishka; Zhang, Lu; Fargnoli, Anthony; Oh, Jae Gyun; Savoia, Maria Elisabetta; Hansen, Jens; Fava, Marika; Yin, Xiaoke; Theofilatos, Konstantinos; Ceholski, Delaine; Kohlbrenner, Erik; Jeong, Dongtak; Wills, Lauren; Nonnenmacher, Mathieu; Haghighi, Kobra; Costa, Kevin D.; Turnbull, Irene C.; Mayr, Manuel; Cai, Chen-Leng; Kranias, Evangelia G.; Akar, Fadi G.; Hajjar, Roger J.; Stillitano, Francesca; Pediatrics, School of Medicine
    Aims: A mutation in the phospholamban (PLN) gene, leading to deletion of Arg14 (R14del), has been associated with malignant arrhythmias and ventricular dilation. Identifying pre-symptomatic carriers with vulnerable myocardium is crucial because arrhythmia can result in sudden cardiac death, especially in young adults with PLN-R14del mutation. This study aimed at assessing the efficiency and efficacy of in vivo genome editing, using CRISPR/Cas9 and a cardiotropic adeno-associated virus-9 (AAV9), in improving cardiac function in young adult mice expressing the human PLN-R14del. Methods and results: Humanized mice were generated expressing human wild-type (hPLN-WT) or mutant (hPLN-R14del) PLN in the heterozygous state, mimicking human carriers. Cardiac magnetic resonance imaging at 12 weeks of age showed bi-ventricular dilation and increased stroke volume in mutant vs. WT mice, with no deficit in ejection fraction or cardiac output. Challenge of ex vivo hearts with isoproterenol and rapid pacing unmasked higher propensity for sustained ventricular tachycardia (VT) in hPLN-R14del relative to hPLN-WT. Specifically, the VT threshold was significantly reduced (20.3 ± 1.2 Hz in hPLN-R14del vs. 25.7 ± 1.3 Hz in WT, P < 0.01) reflecting higher arrhythmia burden. To inactivate the R14del allele, mice were tail-vein-injected with AAV9.CRISPR/Cas9/gRNA or AAV9 empty capsid (controls). CRISPR-Cas9 efficiency was evaluated by droplet digital polymerase chain reaction and NGS-based amplicon sequencing. In vivo gene editing significantly reduced end-diastolic and stroke volumes in hPLN-R14del CRISPR-treated mice compared to controls. Susceptibility to VT was also reduced, as the VT threshold was significantly increased relative to controls (30.9 ± 2.3 Hz vs. 21.3 ± 1.5 Hz; P < 0.01). Conclusions: This study is the first to show that disruption of hPLN-R14del allele by AAV9-CRISPR/Cas9 improves cardiac function and reduces VT susceptibility in humanized PLN-R14del mice, offering preclinical evidence for translatable approaches to therapeutically suppress the arrhythmogenic phenotype in human patients with PLN-R14del disease.
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    Pkm2 Regulates Cardiomyocyte Cell Cycle and Promotes Cardiac Regeneration
    (American Heart Association, 2020-04-14) Magadum, Ajit; Singh, Neha; Kurian, Ann Anu; Munir, Irsa; Mehmood, Talha; Brown, Kemar; Sharkar, Mohammad Tofael Kabir; Chepurko, Elena; Sassi, Yassine; Gyun, Jae; Lee, Philyoung; Santos, Celio X.C.; Gaziel-Sovran, Avital; Zhang, Guoan; Cai, Chen-Leng; Kho, Changwon; Mayr, Manuel; Shah, Ajay M.; Hajjar, Roger J.; Zangi, Lior; Pediatrics, School of Medicine
    Background: The adult mammalian heart has limited regenerative capacity, mostly attributable to postnatal cardiomyocyte cell cycle arrest. In the last 2 decades, numerous studies have explored cardiomyocyte cell cycle regulatory mechanisms to enhance myocardial regeneration after myocardial infarction. Pkm2 (Pyruvate kinase muscle isoenzyme 2) is an isoenzyme of the glycolytic enzyme pyruvate kinase. The role of Pkm2 in cardiomyocyte proliferation, heart development, and cardiac regeneration is unknown. Methods: We investigated the effect of Pkm2 in cardiomyocytes through models of loss (cardiomyocyte-specific Pkm2 deletion during cardiac development) or gain using cardiomyocyte-specific Pkm2 modified mRNA to evaluate Pkm2 function and regenerative affects after acute or chronic myocardial infarction in mice. Results: Here, we identify Pkm2 as an important regulator of the cardiomyocyte cell cycle. We show that Pkm2 is expressed in cardiomyocytes during development and immediately after birth but not during adulthood. Loss of function studies show that cardiomyocyte-specific Pkm2 deletion during cardiac development resulted in significantly reduced cardiomyocyte cell cycle, cardiomyocyte numbers, and myocardial size. In addition, using cardiomyocyte-specific Pkm2 modified RNA, our novel cardiomyocyte-targeted strategy, after acute or chronic myocardial infarction, resulted in increased cardiomyocyte cell division, enhanced cardiac function, and improved long-term survival. We mechanistically show that Pkm2 regulates the cardiomyocyte cell cycle and reduces oxidative stress damage through anabolic pathways and β-catenin. Conclusions: We demonstrate that Pkm2 is an important intrinsic regulator of the cardiomyocyte cell cycle and oxidative stress, and highlight its therapeutic potential using cardiomyocyte-specific Pkm2 modified RNA as a gene delivery platform.