As our body ages, it loses its ability to repair damage, including that from normal wear and tear. Scientists from the Ottawa Hospital Research Institute and University of Ottawa have found the mechanisms behind our skeletal muscle decline. The results of their study were published in the journal Nature Medicine.
Dr. Michael Rudnicki, a leader of the study, discovered that aging muscle cells experience a progressive growth in the activation of a specific signalling pathway that leads to reduced muscle function. The pathway transmits information from the surrounding tissue to the muscle cells, and the pathway that is responsible for gradual muscle decline is called the JAK/STAT signalling pathway.
The team leader explained that when they took an old animal and inhibited this signaling pathway with specific drugs that are currently used for chemotherapy, they found that ability of the old animal’s muscle stem cells to renew and build new tissue increased to the level of young animals.
The mechanism behind this is the following. Due to gradually increasing activation of the JAK/STAT pathway, the way how our skeletal muscle stem cells divide changes. Normally, some part of muscle stem cells divides to produce muscle cells, while other part is involved in symmetric division, i.e. when two identical daughter stem cells arise from the one. This symmetrical division helps maintain the population of stem cells which hold reparative capacity However, when JAK/STAT pathway is activated, fewer stem cells divide to produce stem cells while more are converted to become muscle fibre. As a result, our muscles weaken, their ability to overcome damage drastically reduces.
Although the research is still at its early stages, the team aims to discover the treatments for muscle-wasting diseases such as muscular dystrophy. In addition, the finding can lead to discovery of new anti-aging therapies. The authors also plan to replace toxic drugs that were used in the study with less toxic ones that would have the same effect.