Heart Muscle Regeneration In Childhood And Beyond: Study reveals heart muscles grow in childhood because they increase in size instead of number.

According to a study by the Karolinska Institute in Sweden, heart muscles can regenerate during the first 10 years of a person’s life, and continue to do so later in life as well.

The study was published in the journal Cell, demonstrating that heart muscles can be made to regenerate at a modest rate throughout an individual’s life, supporting the possibility of stimulating and rebuilding damaged heart tissue.

The study was financed with grants from the Heart Lung Foundation, Swedish Research Council, Karolinska Institutet, the Swedish Cancer Society, StratRegen, the Tobias Foundation, the Knut and Alice Wallenberg Foundation and the Torsten Söderberg Foundation.

During a heart attack, certain parts of the cardiac muscle are deprived of oxygen. This causes extensive damage to the cells and even death, replacing the dead cells with scar tissue. Since the presence of damaged cells and scar tissue impairs the effective functionality of the heart muscle, researchers in the field of regenerative medicine have been keenly interested in finding a method of regenerating the lost heart muscle.

To demonstrate the possibility of heart muscle regeneration, the study involved various methods. Among them was measuring the amount of C-14, a radioactive isotope of carbon. Researchers exploited the sharp increase in atmospheric levels of the isotope between the 1950’s and 60’s, which occurred due to nuclear testing. The levels of C-14 had then declined, indicating that the cells that were formed after the decrease had lower levels of C-14. Hence, by measuring the amounts of C-14 incorporated in the DNA of a cell, its age can be estimated.

The results of the study revealed that heart muscles grow in childhood because they increase in size instead of number – thus they are regenerated at a modest rate. Even during late adulthood, only about 40% of cardiac cells are replaced.

“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,” stated Olaf Bergmann from the Department of Cell and Molecular Biology.

The study also demonstrated that the heart contained other types of cells as well – endothelial cells and connective tissue (mesenchymal cells). It was seen that these cells evolved at a much faster rate than the heart cells. The endothelial cells exhibited the shortest lifecycle, and in adults all these cells are completely replaced over six years. However, the mesenchymal cells are replaced approximately twice during the life of an individual.

“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,” study leader Jonas Frisén from the Department of Cell and Molecular Biology remarked.