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What prevents the heart to recover?

The cardiac muscle apparently can not regenerate because of its own intercellular substance.

What prevents the heart to recover?

Heart cells of newborn mice. Blue dyed cell nucleus. (Photo: California Institute for Regenerative Medicine / Flickr.com)

In all mammals the heart is not restored: new cells (cardiomyocytes) is displayed only during the embryonic development and stem cells from which they appear immediately after birth fall asleep. Therefore, after a heart attack, damaged areas of the cardiac muscle is the muscle cells, which could be reduced, there is connective tissue in a scar.

However, in 2011 a cardiologist Hash Sadek (Hesham Sadek) with colleagues from the University of Texas. After surgical removal from mice one day of the piece of the heart muscle, the lost tissue was recovered within three weeks, and two months later, the ventricle was already working as, if any damage was not.

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Ability to restore the heart was kept seven days, seven animals the ventricle is already not regenerated. Curious thing was that regeneration was not due to stem cells, and the normal Mature cells of the heart muscle, which, apparently, suddenly remembered how to share.

Results tried to reproduce in other research groups, but managed not all. However, there were those who still managed to see for myself how much the heart muscle was restored, and among them were ángel Raya (Ángel Raya) and his colleagues at the Barcelona center for regenerative medicine. But their goal was not just to see the same result. Obviously, in the newborn heart, there are some changes, and to understand what this changes, is possible only after analyzing the activity of genes in cardiomyocytes.

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In the new experiments, the heart was restored only if the damage occurred on the first day of life; if the mice were at least two days old, the cardiac muscle there is a characteristic scar (i.e., regenerative abilities are not enough for a week, but over a much shorter period). One would assume that the day after birth, the heart cells turned off genes that control cell division.

However, it was not so: the article in Science Advances they say that the differences between “day” and “two-day” were in the genes related to the extracellular substance, or extracellular matrix. This substance is found in all tissues and organs, it somewhere in the body, helps to keep the shape, provides mechanical support and helps cells to communicate with each other and maintain the working environment.

The composition of the extracellular matrix is ​​composed of a variety of biomolecules, the synthesis of which is governed by specific genes. And now it turns out that genes that stimulate the accumulation of the intercellular substance in the heart, the day after birth, become very active, and the heart on the second day, becomes 50% harder and denser than the day before.

In addition, when in the heart of the mice, we tried to disable the enzyme that is necessary for the formation of the extracellular matrix. We can assume that the heart muscle can be regenerated if it does not interfere with the accumulation of intercellular connective tissue. But, of course, if you think about a treatment, then there must be another way to stimulate the recovery of the heart. should.

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However, some experts doubted that. Let connective tissue scars on the heart and you are not formed.

The angel Raya claims that any damaged parts on the heart in mice did appear muscular tissue; but, anyway, the results have more than once to the double check – especially as they relate to such controversial topics as the restoration of the heart.

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