Researchers at the University of California, Berkeley, have turned back the clock on mature muscle tissue, coaxing it back to an earlier stem cell stage to form new muscle. Moreover, they showed in mice that the newly reprogrammed muscle stem cells could be used to help repair damaged tissue. The achievement, described in the Sept. 23 issue of the journal Chemistry & Biology, “opens the door to the development of new treatments to combat the degeneration of muscle associated with muscular dystrophy or aging,” said study principal investigator Irina Conboy, UC Berkeley assistant professor of bioengineering.
Skeletal muscle tissue is composed of elongated bundles of myofibers, which are individual muscle cells (myoblasts) that have fused together. This fusion of individual cells is considered the final step of skeletal muscle differentiation.
“Muscle formation has been seen as a one-way trip, going from stem cells to myoblasts to muscle fiber, but we were able to get a multi-nucleated muscle fiber to reverse course and separate into individual myoblasts,” said Conboy, who is also a member of the Berkeley Stem Cell Center and an investigator with the California Institute for Quantitative Biosciences (QB3). “For many years now, people have wanted to do this, and we accomplished that by exposing the tissue to small molecule inhibitor chemicals rather than altering the cell’s genome.”