Researchers at the University of Rochester have discovered that stem cells are the key to strong muscles in old age. They found that muscle stem cells in animal models drive muscle loss in old age, contrary to the currently prevailing idea that muscular decline with advancing age is on account of motor neuron loss. The scientists hope to develop a drug that will slow down the loss of muscle stem cells and consequently stop age-related muscle loss.
Age-Related Muscle Loss
Subtle muscle decline begins as early as the mid-30s in humans. By the time a person is in their 70s and 80s, muscle decline can be severe, leading to frailty and loss of independence. Every individual ages differently and muscle decline likewise varies from person to person. Some people may not be able to do simple activities of daily living while others may find exercising difficult with advancing age.
Study author, Assistant Professor of Orthopedics, Joe Chakkalakal, explains that even elite athletes with superior muscle strength as young adults experience declining muscle strength with age. The scientists have been studying declining muscle mass in aging mice with the hope of identifying ways to avoid it in humans.
Stem Cells Key to Strong Muscles in Old Age
The findings, published in the journal eLife, show that stem cells play a vital role in muscle maintenance throughout life. In adults, a population of stem cells is present in muscle tissue which serves as a source of new muscle cells in response to injury and exercise. Prior research has already shown that muscle stem cells die in aging individuals, but the new study indicates that they play a critical role in maintaining muscle strength as we age.
Stem Cell Experiments for Muscle Loss
Chakkalakal’s team removed muscle stem cells in mice without disturbing nerve cells called motor neurons. Motor neurons control muscles and are thought to play a critical role in age-related muscular decline.
The team found that in mice in whom the stem cells were depleted, muscle loss occurred in middle age rather than old age. In mice with intact muscle stem cells, muscles remained healthier than control mice of the same age. The team also did not find a loss of motor neurons occurring with age. Current theories believe that loss of connections in motor neurons is the driving force behind muscle atrophy and death in aging individuals. The findings have demonstrated that in sedentary individuals, stem cells play a role in muscle maintenance throughout life. The team now plans to search for drugs that may help maintain the pool of stem cells in muscles to inhibit muscular degeneration with advancing age.