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Molecular mechanism of cardiac hypertrophy and development
1Department of Cardiovascular Medicine, University of Tokyo Graduate School of Medicine, Japan. komuro-tky@umin.ac.jp
Insights
Mechanical stress causes cardiac hypertrophy, a key factor in heart failure. Researchers developed an in-vitro model to study this process, identifying key signaling pathways and genes like Csx involved in cardiac development and disease.
Area of Science:
- Cardiology
- Molecular Biology
- Developmental Biology
Background:
- Congestive heart failure is a significant clinical challenge.
- Understanding cardiac hypertrophy mechanisms is crucial for heart failure research.
- Mechanical stress is a primary driver of cardiac hypertrophy.
Purpose of the Study:
- To investigate the signaling pathways linking mechanical stress to cardiac hypertrophy.
- To identify key genes and molecular mechanisms involved in cardiac development and differentiation.
- To explore potential therapeutic strategies for heart failure.
Main Methods:
- Developed an in-vitro device to apply mechanical stress to neonatal rat cardiac myocytes.
- Analyzed hypertrophic responses including protein kinase activation, gene expression, and protein synthesis.
- Isolated and studied the role of the cardiac homeobox-containing gene Csx in cardiac development.
Main Results:
- Mechanical stretching of cardiac myocytes induced hypertrophic responses.
- Vasoactive peptides (angiotensin II, endothelin-1) were upregulated and critical for hypertrophy.
- The gene Csx is essential for cardiac development; its disruption leads to embryonic lethality.
- Csx, with GATA4, induces cardiomyocyte differentiation and upregulates cardiac genes.
Conclusions:
- Mechanical stress initiates signaling cascades leading to cardiac hypertrophy.
- Vasoactive peptides play a critical role in mediating stress-induced cardiac hypertrophy.
- The Csx gene is a vital regulator of cardiac development and differentiation.
- Understanding Csx function is important for congenital heart disease research and potential therapies.
Abstract:
Congestive heart failure is a major issues for cardiologists and to fully understand heart failure, it is important to understand the mechanism of the development of cardiac hypertrophy. Hemodynamic overload, namely mechanical stress, is a major cause of cardiac hypertrophy and to dissect the signaling pathways from mechanical stress to cardiac hypertrophy, an in-vitro device by which mechanical stress can be imposed on cardiac myocytes of neonatal rats cultured in serum-free conditions has been developed. Passively stretching cardiac myocytes cultured on silicone membranes induced various hypertrophic responses, such as activation of the phosphorylation cascades of many protein kinases, expression of specific genes and an increase in protein synthesis. During this process, secretion and production of vasoactive peptides, such as angiotensin II and endothelin-1, were increased and they played critical roles in the induction of these hypertrophic responses. Candidates for the 'mechanoreceptor' that receives the mechanical stress and converts it into intracellular biochemical signals have been recently demonstrated. Gene therapy and cell transplantation are hopeful strategies for the treatment of heart failure and require an understanding of how normal cardiac myocytes are differentiated. A key gene that plays a critical role in cardiac development has been isolated. The cardiac homeobox-containing gene Csx is expressed in the heart and the heart progenitor cells from the very early developmental stage, and targeted disruption of the murine Csx results in embryonic lethality because of the abnormal looping morphogenesis of the primary heart tube. With a cardiac zinc finger protein GATA4, Csx induces cardiomyocyte differentiation of teratocarcinoma cells as well as upregulation of cardiac genes. Mutations of human CSX cause various congenital heart diseases including atrial septal defect, ventricular septal defect, tricuspid valve abnormalities and atrioventricular block.