There is a growing collection of evidence that exercise is greatly beneficial for heart health, but experts have not yet clarified why this is the case. A team of researchers from Harvard University may have now solved part of this mystery with the finding that exercise activates cardiac muscle cell growth in mice, helping the heart to regenerate.
The results of the study have major implications for physical education and for the rehabilitation of patients after heart attacks.
“We wanted to know whether there is a natural way to enhance the regenerative capacity of heart muscle cells,” said co-first author Dr. Ana Vujic. “So we decided to test the one intervention we already know to be safe and inexpensive: exercise.”
The human heart does not have the capability to repair itself beyond the regeneration of one percent of cardiac muscle cells per year in young adults. Identifying a way to replace lost heart cells could prevent chronic illness or death in the 200,000 individuals who are diagnosed with heart failure in the United States every year.
To investigate the impacts of exercise on the heart, the researchers compared a group of healthy mice who ran on a treadmill approximately 5 kilometers each day to another group of healthy mice that were sedentary. The researchers administered a chemical into specific regions of DNA to track where new heart muscle cells were being generated.
The study revealed that the physically active mice produced at least four and a half times the number of new heart muscle cells compared to the sedentary mice.
“We also wanted to test this in the disease setting of a heart attack, because our main interest is healing,” said Dr. Vujic.
Mice that had recently experienced a heart attack were given access to a treadmill and voluntarily ran the same 5 kilometers daily.
As a result, the mice showed a significant increase in the area of heart tissue where new muscle cells were made.
“Maintaining a healthy heart requires balancing the loss of heart muscle cells due to injury or aging with the regeneration or birth of new heart muscle cells,” said co-senior author Dr. Anthony Rosenzweig. “Our study suggests exercise can help tip the balance in favor of regeneration.”
Co-senior author Dr. Richard Lee added, “Our study shows that you might be able to make your heart younger by exercising more every day.”
During their analysis, the researchers identified a biological pathway that was required for exercise to stimulate cardiac cell regeneration in mice.
“Now we need to find the signals that are sufficient to turn this pathway on,” said Dr. Rosenzweig. “If we can turn on these pathways at just the right time, in the right people, then we can improve recovery after a heart attack.”
The study is published in the journal Nature Communications.