Stockholm: New human heart muscle cells can be formed, but this mainly happens during the first ten years of life, according to a new study from Karolinska Institutet. Other cell types, however, are replaced more quickly. The study, which is published in the journal Cell , demonstrates that the heart muscle is regenerated throughout a person’s life, supporting the idea that it is possible to stimulate the rebuilding of lost heart tissue. During a heart attack, when parts of the heart muscle are starved of oxygen, many heart cells die and are replaced by scar tissue. As this impairs functionality, many researchers are interested in the possibility of stimulating the regeneration of lost heart muscle cells. But is it possible?
This is one of the big
questions of regenerative medicine, and scientists have long been trying
to answer it, without arriving at a consensus.
To examine the regeneration of human heart cells, the team
behind this new study used a combination of methods. One such was to
measure the radioactive isotope C-14, exploiting the sharp rise in
atmospheric levels of carbon-14 in the 1950s and 60s caused by nuclear
testing. Levels then declined, which means that cells that were formed
after that period give lower C-14 readings than those formed during it.
Thus by measuring the amount of C-14 in a cell’s DNA, the researchers
were able to calculate its age.
“We examined the heart tissue from 29 deceased individuals of
various ages and found that even by one month after birth, the heart
contains the same number of cells as it has in adults,” says Olaf
Bergmann from the Department of Cell and Molecular Biology.
According to the study, the heart grows during childhood
because its cells increase in size rather than in number; in other
words, heart cells are generated on only a modest scale, and even during
a long life, only forty per cent of muscle cells are replaced.
The heart also contains other types of cell, such as
endothelial cells and cells in the connective tissue that go under the
collective name of mesenchymal cells. What the researchers found was
that these cell populations change much more than the heart muscle
cells. The endothelial cells have the shortest life-cycle, and in adults
all such cells are exchanged over a six-year period. The mesenchymal
cells are also replaced, but more slowly – twice during a lifetime
estimate the researchers behind this new study.
“Our study shows that endothelial cells, mesenchymal cells and
heart muscle cells are renewed in the human heart throughout life,
albeit at a different rate for different cells,” says study leader Jonas
Frisén from the Department of Cell and Molecular Biology. “Our findings
suggest that it can be rational and realistic to develop new
therapeutic strategies for strengthening the body’s own regenerative
capacity to treat heart diseases.”
The study was financed with grants from the Swedish Research
Council, the Heart-Lung Foundation, the Swedish Cancer Society,
Karolinska Institutet, the Tobias Foundation, StratRegen, the Torsten
Söderberg Foundation and the Knut and Alice Wallenberg Foundation.