Cardiomyocytes recover, only slowly and low
The mammalian heart is constantly regenerating, albeit very slowly
NanoNewsNet based on Max-Planck-Gesellschaft: The heart's own stem cells play their part in regenerationA few years ago, the scientific community was unanimous in the opinion that the regenerative capacity of the mammalian heart is almost zero.
However, scientists now know that heart muscle cells are constantly regenerating, albeit at a very low rate. Scientists from the Max Planck Institute for Heart and Lung Research in Bad Nauheim, Germany, have identified a population of stem cells responsible for this regeneration. Perhaps in the future, science will be able to create drugs that stimulate the processes of self-healing in patients with diseases of the heart muscle.
Some vertebrates seem to have found a source of eternal youth, at least for their hearts. So, in many amphibians and fish, this important organ has a significant ability to regenerate and self-heal. And some representatives of these two groups have this ability brought to perfection: they can completely eliminate the damage caused to the heart tissue, thereby preserving the functionality of the organ.
With mammals, everything is more complicated: their heart really has a very low ability to regenerate. According to the prevailing ideas until recently, the reason for this is that the cells of their heart muscle stop dividing immediately after birth. It was also assumed that there are no stem cells in the mammalian heart – the source of new cardiomyocytes. However, recent studies show that the old muscle cells of the mammalian heart are still being replaced by new ones. But, according to experts, only one to four percent of the cells in the heart muscle are replaced every year.
Scientists from the research group of Professor Thomas Braun managed to identify a population of stem cells in the heart of mice, which plays a key role in the regeneration of cardiomyocytes. Experiments on genetically modified mice conducted by scientists from Bad Nauheim show that the so-called Sca1 stem cells of a healthy heart are involved in the permanent replacement of cardiomyocytes. Sca1 cells increase their activity in response to damage to the heart, as a result of which the number of newly formed cardiomyocytes increases significantly.
Since, compared to the total number of heart muscle cells, Sca1 stem cells account for only a small fraction, their search is a search for a needle in a haystack. In addition, the researchers faced another problem: after the transformation of stem cells into cardiomyocytes, the protein Sca1 is no longer expressed as a marker. To prove their participation in regenerative processes, scientists had to show ingenuity. They genetically modified the stem cells in such a way that, in addition to Sca1, the cells expressed another visible marker. This fluorescent marker was detected constantly.
"Thus, we were able to establish that in healthy mice, the proportion of cardiomyocytes originating from Sca1 stem cells is constantly increasing. Within 18 months, about five percent of the heart muscle cells regenerate," says project manager Shizuka Uchida.
In addition, in mice with simulated heart diseases, the number of such newly formed cardiomyocytes increased threefold.
"These data show that, in principle, the mammalian heart is able to start the processes of regeneration and renewal. However, under normal conditions, these processes are not enough to completely restore the heart muscle," Dr. Brown comments on the results.
Now the scientists' goal is to find ways to enhance the formation of new cardiomyocytes from stem cells and, thereby, increase the heart's ability to self–repair.
Article by Uchida et al. Sca1-derived cells are a source of myocardial renewal in the murine adult heart published in the journal Stem Cell Reports.
Portal "Eternal youth" http://vechnayamolodost.ru03.12.2013