Mechanical forces form the heart valve


Half of the Nobel Prize in Medicine and Physiology this year was awarded for the discovery of mechanical pressure receptors. In this regard, we talked about the important role mechanoreceptors play in our life: we are not only talking about the sense of touch – they are needed by the lungs, intestines, blood vessels, immunity and skin stem cells. Even the development of the embryo depends on mechanical forces: if the embryonic tissues do not feel compression and stretching, some organs will not form correctly, and the individual will be born with congenital defects.

Researchers from the University of Strasbourg and Imperial College London studied the development of heart valves in fish embryos Denmark rerio, or striped zebrafish. When the heart expands, it sucks in blood from the supplying vessels; when it contracts, the blood goes out into other vessels, which send it further through the body. At the same time, it is important that when the heart muscle relaxes, the blood does not return back from the outflowing vessels to the heart, and when the heart muscle contracts, so that the blood does not go out into the supplying vessels from which it has just come. Heart valves provide a unidirectional blood flow: there is a valve at the entrance to the heart and which closes when contracted, and there is a valve at the exit from the heart.

But that’s not all: there are chambers in the heart, fish have two, amphibians and most reptiles have three, birds and animals have four. There are also valves between the chambers that perform the same function – to prevent blood from flowing back. Many heart defects are associated with valves that allow blood to flow backward; because of this, the blood supply to tissues and organs, including the heart itself, is disrupted.

The formation of valves in the embryo is subject to a genetic program. But some genes are few, it is necessary for the forming valve to work, so that its cells experience mechanical stress from the blood and the working heart muscle. The researchers observed how a valve develops between the atrium and ventricle in fish embryos. In an article in Science they write that for the proper development of the valve, the Nfatc1 protein must be in the nuclei of the embryonic cells – there it will act in the right way on certain genes. Nfatc1 enters the nucleus when a signaling chain is turned on, in which calcium ions and one of the cellular receptors are involved. And this signal chain, in turn, is activated by mechanical forces. Mechanical pulsation turns into a bioelectric signal that tells stem cells what to do, where to divide more strongly, where it is weaker, like ordinary specialized cells – and this is how it turns out that the shape of the heart valve depends on mechanical forces.

Most likely, not only in fish, but also in other animals, for the correct formation of heart valves, the stem cells need to feel rhythmic contractions and stretches. And it is obvious that if something goes wrong in this signal chain, which starts from mechanical action, the valve will turn out to be defective. But the details here will become clear only after additional experiments, which will have to be performed not only on fish, but also on mammals.


Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.

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