#heart development

Growing Beats

Building a heart carries a lot of pressure. This vital organ must beat or contract regularly, every few moments, for an entire life. Understanding the steps involved in building this zebrafish heart offers clues to similar mechanisms in developing human hearts. Pictured using a 3D microscopy technique, we see heart muscle cells known as cardiomyocytes (highlighted in white with their nuclei in yellow) in the top chambers – the atria – of a young zebrafish’s heart temporarily paused in its beating. Using this and other tools, scientists compare how cardiomyocytes develop into the cardiac muscle lining the atria and the lower chambers, the ventricles. Surprisingly, they find different chemical signals and patterns of growth shaping the different chambers – with stretched cardiomyocytes in the atria possibly allowing for speedy transfer of electrical impulses. Exploring these differences may yield clues to heart abnormalities during development, or later problems such as heart arrhythmias.

Written by John Ankers

Video from work by Marga Albu and colleagues

Max Planck Institute for Heart and Lung Research, Department of Developmental Genetics, Bad Nauheim, Germany

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Nature Communications, September 2024

Follow the Heart

The coronary arteries get all the acclaim when it comes supplying the heart with blood. But they branch out into a network of blood vessels that also do the work of supplying the heart with blood but don’t get so much of the limelight — they form the heart’s microvasculature. Researchers now investigate its importance in development using a new imaging and analysis toolset. They labelled heart muscle cells and microvasculature in developing quail hearts with different dyes. Using confocal fluorescent microscopy, they imaged these heart muscle cells and blood vessels (pictured) and analysed their orientations. Focusing on one of the heart’s lower chambers, they found the microvasculature followed the helical pattern of organisation of the heart muscle cells. This new approach may provide useful insights into the role of the heart's microvasculature in heart diseases, such as hypertrophic cardiomyopathy, where developing heart cells are misaligned.

Written by Lux Fatimathas

Image from work by Maryse Lapierre-Landry and Hana Kolesová and colleagues

Department of Biomedical Engineering, School of Medicine, Case Western Reserve University, Cleveland, OH, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Scientific Reports, September 2020

Neighbourly Messages

Like you drop a note through a neighbour’s letterbox, cells send messages to nearby companions, with instructions like ‘move’ or ‘die’ (hopefully not quite what you suggest to neighbours). To better understand the fundamentals of these widespread and crucial interactions, researchers investigated how just one of these messages, or ligands, is able to relay many messages in the simple fruit fly. They found multiple components, including a tether preventing the message spreading too far from the sender, like two cups on a string, and one that controls the volume of the message, helping distinguish an urgent shout from a gentle suggestion. These subtleties enable clear communication, and the ligand in question – FGF Pyramus, red in the developing fly embryo sequence pictured, with corresponding receptors in green – is key to healthy heart development in both flies and humans. Deciphering its methods of communication could reveal clues to preventing developmental heart defects.

Written by Anthony Lewis

Image from work by Vincent Stepanik, Jingjing Sun and Angelike Stathopoulos

Host– Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA

Image copyright Elsevier 2020. Reproduced with permission.

Published in Current Biology, August 2020

Hox Hearts

One leaky valve is all it takes to send things into disarray. We’re not talking about plumbing but the human heart. Congenital heart defects, such as a leaky valve, are sometimes caused by the failure of developing heart cells to mature correctly. Researchers focus on one group of cells vital for heart development called SHF cardiac progenitor cells. By analysing the messenger RNA in these cells in embryonic mouse hearts, they found the protein Hoxb1 was needed for correct maturation. Activating Hoxb1 in a subgroup of these cells disrupted the formation of the bottom right chamber of the heart as captured using fluorescence microscopy (pictured, right) when compared to hearts with normal Hoxb1 activity (left). Moreover, mice lacking Hoxb1 and a related protein, Hoxa1, had defects in the partitions between the top and bottom chambers of the heart. This provides clues to how certain congenital heart defects may arise.

Written by Lux Fatimathas

Image from work by Sonia Stefanovic and Brigitte Laforest, and colleagues

Aix Marseille Univ, INSERM, Marseille Medical Genetics, Marseille, France

Image originally published under a Creative Commons Licence (BY 4.0)

Published in eLife, August 2020

Heart Pressed

Standing in a dense crowd, a nudge here and a shove there are signals to shuffle over, make way, or stand your ground. And a new study has shown that at the molecular level, physical pressures can have a similar effect. During early heart development, two types of tissue grow separately, but in tandem: the muscle and the inner lining. Studying the hearts of various zebrafish (pictured in different colours to highlight particular factors at play), they found that the increasing pressure from expanding muscle tissue prompts chemical signals that encourage the lining to keep growing. The lining only slows when the pressure eases off – showing that a physical feedback loop is instigating important biochemical signals, a form of communication not previously seen. If this push and pull method of communication exists in other organs, it may reveal new details of how we grow, and even how diseases take hold.

Written by Anthony Lewis

Image from work by Dorothee Bornhorst and colleagues

Institute of Biochemistry and Biology, Potsdam University, Potsdam, Germany

Image copyright held by the original authors

Research published in Nature Communications, September 2019