A recent study published in Nature Communications identifies a link between exercise and the heart's ability to regenerate new muscle cells under normal conditions and after a heart attack.
The research, which was conducted on groups of mice, could have dramatic implications for "public health, physical education, and the rehabilitation of cardiac patients."
The first study authors are Ana Vujic, Ph.D., who works in the Harvard Department of Stem Cell and Regenerative Biology in Cambridge, MA, and Dr. Carolin Lerchenmüller, of Harvard Medical School (HMS), also in Cambridge, and the Massachusetts General Hospital in Boston.
According to previous research, our hearts have very little capacity to regenerate themselves.
Vujic explains, "We wanted to know whether there was a natural way to enhance the regenerative capacity of heart muscle cells. So, we decided to test the one intervention we already know to be safe and inexpensive: exercise."
They found that heart muscle cells in a young adult heart only renew 1 percent every year and this would continue to decrease with age. Therefore, any interventions that increase new heart cell formation could have the potential to prevent heart failure in the future.
The effects of exercise on heart cells
The mice with the treadmill ran around 5 kilometers each day. The scientists were able to measure heart regeneration in the mice by tracking the newly made DNA as the cells divided. By doing this, they could see where new cells were being produced in the heart muscles.
The team reported that the mice that used the treadmill produced more than four and half times the amount of new heart muscle cells than those without access to a treadmill.
They decided to take the test one step further by using mice that had experienced an actual heart attack. As Vujic says, "We also wanted to test this in the disease setting of a heart attack, because our main interest is healing."
Following a heart attack, the mice with access to a treadmill continued to run 5 kilometers per day voluntarily, and they showed an increase in heart tissue where new muscle cells were formed.
Co-senior study authors Dr. Richard Lee, a Harvard professor of stem cell and regenerative biology, and Dr. Anthony Rosenzweig, a Paul Dudley White Professor of Medicine at the HMS, believe that they have made significant progress with their research.
Dr. Rosenzweig says, "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. Our study suggests exercise can help tip the balance in favor of regeneration."
Dr. Lee adds, "Our study shows that you might be able to make your heart younger by exercising more every day."
The next step for these researchers is to locate the biological mechanisms that tie exercise to the regeneration of heart muscle cells. Thus far, they have found a particular biological pathway needed for exercise to switch on heart muscle cell regeneration.
"Now," explains Dr. Rosenzweig, "we need to find the signals that are sufficient to turn this pathway on."
Dr. Lee concludes, "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."