Bad Timing

Your heart isn't all muscle. Its muscle layer (myocardium) is sandwiched between endocardium and epicardium. Defects in the development of these layers can cause congenital heart disease (CHD), which affects one in 100 newborns. CHD can be caused by a coronary artery fistula (CAF) where a channel, partly comprising smooth muscle, develops between the coronary artery and another part of the heart. A defect in myocardium development may be to blame. Researchers investigated in chick embryos, damaging the myocardium before the epicardium layer forms. The result? Endocardium cells met epicardium cells too early, leading to CAF-like structures. The team then grew quail embryo endometrium (pictured, left) with chick embryo epicardium (right). Fluorescence microscopy revealed that where these different cells met, smooth muscle developed, and where they were apart, smooth muscle was absent. This supports the idea that CAFs form due to the inappropriately timed meeting of these cells.

Written by Lux Fatimathas

Image from work by P. Palmquist-Gomes and colleagues

Department of Animal Biology, Faculty of Sciences, University of Málaga, Málaga, Spain

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

Published in Experimental & Molecular Medicine, January 2023

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