In their current study, published in the online edition of the journal Nature, Conboy and her team found that old muscle produces elevated levels of a molecule called TGF-beta, which is known to inhibit muscle growth. The researchers then showed that the muscle-deteriorating effects of TGF-beta can be reversed by blocking its pathway in old mice.
In the experiments, the researchers used RNA interference, which can silence specific genes, to inhibit the molecules that act downstream of TGF-beta to prevent cells from multiplying. They then locally injured the muscles of treated mice, as well as untreated old and young mice, by injecting a small amount of snake venom, which killed muscle tissue in the immediate vicinity.
After five days, the team found that the young mice were able to produce healthy cells to replace damaged tissue. The treated older mice, whose inhibitory pathways were suppressed, were able to regenerate new cells in much the same way. Not surprisingly, old untreated mice did not recover as well and developed fibroblasts and scar tissue around the injured site.