Researchers find pathway to restore aging muscle
Researchers compared muscle samples from two groups of adult males—one group averaging 22 years of age, while the other group averaged 71 years of age. The subjects were then placed in leg casts for two weeks to simulate muscle atrophy. After the casts were removed, more muscle samples were taken at three days, then again at four weeks. Researchers found that adult stem cells in the younger samples were far more numerous than those in the older samples. What's more, when the two groups were subjected to a recuperative exercise regime, the older muscles actually showed signs of scaring and inflammation if the routine was too rigorous.
The researchers then tinkered with a few chemical receptors in the muscle tissue, including: Notch, which is a muscle stem cell receptor that triggers growth; TGF-beta, a protein that inhibits a cell's ability to divide; and mitogen-activated protein kinase (MAPK), which regulates Notch and is associated with organ growth. In older muscle, researchers knew that levels of Notch and MAPK tend to be low, while levels of TGF-beta tend to be high. By opening up the MAPK pathways in the older subjects, researchers were able to significantly enhance the ability to grow and regenerate muscle. This discovery means scientists could potentially target the MAPK and Notch pathways to effectively restore tissue health and spur muscle growth. Researchers hope to move on to clinical trials soon, according to the report, which appears in the Sept 30 issue of the journal EMBO Molecular Medicine.