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Manipulating Mechanical Forces in the Developing Zebrafish Heart Using Magnetic Beads

Mechanical forces continuously provide feedback to heart valve morphogenetic programs. In zebrafish, cardiac valve development relies on heart contraction ...

Tokushima University

National Cerebral and Cardiovascular Center Research Institute

Calcium signalling in the endocardium is critical for heart valve development. Calcium ion pulses in the endocardium are generated in response to mechanical forces due to blood flow and can be visualised in the beating zebrafish heart using a genetically encoded calcium indicator such as GCaMP7a. Analysing these pulses is challenging because of the rapid movement of the heart during heartbeat. This protocol outlines an imaging analysis method used to phase-match the cardiac cycle in single z-slice movies of the beating heart, allowing easy measurement of the calcium signal. Key features • Software to synchronise and analyse frames from movies of the beating heart corresponding to a user-defined phase of the cardiac cycle. • Software to measure the fluorescence intensity of the beating heart corresponding to a user-defined region of interest.

Calcium Signal Analysis in the Zebrafish Heart via Phase Matching of the Cardiac Cycle.

Cells functioning at a specific zone by clustering according to gene expression are recognized as zonated cells. Here, we demonstrate anatomical and functional zones in the zebrafish heart. The cardiomyocytes (CMs) at the atrioventricular canal between the atrium and ventricle could be grouped into three zones according to the localization of signal-activated CMs: Wnt/β-catenin signal, Bmp signal, and Tbx2b zones. Endocardial endothelial cells (ECs) changed their characteristics, penetrated the Wnt/β-catenin signal CM zone, and became coronary ECs covering the heart. Coronary vessel length was reduced when the Wnt/β-catenin signal CMs were depleted. Collectively, we demonstrate the importance of anatomical and functional zonation of CMs in the zebrafish heart.

Zonated Wnt/β-catenin signal-activated cardiomyocytes at the atrioventricular canal promote coronary vessel formation in zebrafish.

The structural development of the heart depends heavily on mechanical forces, and rhythmic contractions generate essential physical stimuli during morphogenesis. Cardiac cells play a critical role in coordinating this process by sensing and responding to these mechanical forces. In vivo, cells experience rhythmic spatial and temporal variations in deformation-related stresses throughout heart development. What impact do these mechanical forces have on heart morphogenesis? Recent work in zebrafish (Danio rerio) offers important insights into this question. This review focuses on endocardial (EdCs) and myocardial cells (cardiomyocytes, CMs), key cell types in the heart, and provides a comprehensive overview of forces and tissue mechanics in zebrafish and their direct influence on cardiac cell identity.

Hajime Fukui

Institute of Advanced Medical Sciences

Tokushima University

Manipulating Mechanical Forces in the Developing Zebrafish Heart Using Magnetic Beads

Hajime Fukui

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Tokushima University

Manipulating Mechanical Forces in the Developing Zebrafish Heart Using Magnetic Beads

Institute of Advanced Medical Sciences