Despite the obvious growth and the inevitable aging of our bodies, many of us are tempted to think of our physical vessels as stable and unchanging structures.
The cells of our bodies, however, are in a constant state of flux–regenerating, flourishing and dying at different rates, depending on their purpose and location.
Colon and sperm cells, for example, live for mere days, skin cells for weeks and various types of blood cells for months or years. Only the neurons of the brain’s cerebral cortex and the cells of the eye’s inner lens are irreplaceable. When these die, they are gone forever.
Prior to the past decade, this thinking also applied to heart muscle cells.
Scientists believed that these cells, called cardiomyocytes, were incapable of regeneration, making any damage to the heart muscle permanent.
But then, a research breakthrough
Just recently scientists have shown that the adult human heart generates new muscle cells.
The cells are regenerated in sites throughout the heart several times throughout our lives. Uncovering the mechanisms behind cardiomyocyte regeneration could lay the foundation for the development of therapies that harness the heart’s regenerative capabilities to heal itself.
The work, published in the June 18 edition of Cell, is a result of collaboration between four researchers. Those researchers are: Stefan Jovinge, M.D., Ph.D., director of the DeVos Cardiovascular Research Program (a joint effort between Van Andel Research Institute and Spectrum Health); and Karolinska Institute’s Jonas Frisén, M.D., Ph.D., Olaf Bergmann, M.D., Ph.D., and Henrik Druid, M.D.
The new study builds on the group’s 2009 Science paper, which demonstrated that the adult heart is indeed capable of generating new muscle cells, albeit slowly at about 1 percent annually at age 25. This turnover rate decreases as a person ages, dropping to about 0.45 percent by age 75.
The new paper further defines where this regeneration occurs and how often.
“In our previous paper, we showed an unequivocal generation of heart muscle cells in the adult human heart,” Dr. Jovinge said. “This led to a lot of questions about the nature of the adult generation of cardiomyocytes.”
Questions such as:
- Is the generation of cardiomyocytes restricted and generated from certain locations in the heart?
- Is the heart increasing in size mainly by adding more cells?
- And how does the growth and expansion of the other cells in the heart occur?
“The prospect of using the inherent capacity to generate heart muscle cells in adults to make the heart repair itself requires answers to these questions,” Dr. Jovinge said. “This paper does that.”
One step closer to regenerative therapy
Dr. Jovinge and his partners demonstrate that new cardiomyocytes are continuously generated throughout the heart but hit a threshold of 3.2 billion cells at 1 month of age.
This fixed number indicates that new cells only replace those that die off and that growth of the heart is due to enlargement of individual heart cells, rather than an increasing number of cells.
The team also showed other cells that line the heart’s vessels completely replenish only eight times in a person’s lifespan.
This low turnover rate of cardiomyocytes makes it difficult to heal when the heart sustains damage.
Current work in Dr. Jovinge’s Van Andel Research Institute laboratory focuses on finding the individual cell types responsible for the generation of new heart muscle cells and understanding how this process works.
Once this process is established, Dr. Jovinge’s team plans to develop a treatment to help the heart mend itself by generating new muscle cells.
As medical director of research at Spectrum Health Frederik Meijer Heart & Vascular Institute, Dr. Jovinge directs a clinical program aimed at translating his laboratory findings into new therapies for patients with heart failure and other cardiovascular diseases.
“Our findings open avenues for more research on individual heart muscle cells to find the source for this regeneration,” Jovinge said. “It brings us one step closer to developing regenerative therapies for heart diseases.”