June 9 (UPI) -- Researchers at the University of Rochester Medical Center have discovered that the driving force behind muscle decline in old age is loss of muscle stem cells.
In a recent study with mice, detailed in the journal eLife earlier this week, researchers found the loss of muscle stem cells is the main culprit behind muscle decline in old age, contrary to the current prevailing theory that age-related muscle decline is caused by the loss of motor neurons.
Muscle size and strength start to decline in your mid 30s, however, by the time you reach your 70s and 80s, the decline leaves people frail and makes everyday task difficult.
"Even an elite trained athlete, who has high absolute muscle strength will still experience a decline with age," Joe Chakkalakal, assistant professor of Orthopaedics in the Center for Musculoskeletal Research at URMC, said in a press release.
For the study, the researchers depleted muscle stem cells in mice without disrupting motor neurons, the nerve cells that control muscle.
The researchers found the loss of muscle stem cells in the mice sped up muscle decline starting in middle age. Mice that were genetically altered to prevent muscle stem cell loss had healthier muscles in old age compared to control mice.
Researchers found very few muscle fibers that completely lost connection with their motor neurons, challenging the long-held Denervation/Re-Innervation theory that age-related muscle decline is caused by motor neurons losing their connections or dying causing muscle atrophy.
Chakkalakal said the next step is finding a therapeutic drug target to prevent the loss of muscle stem cells and, as a result, the degeneration of muscles.