In previous studies, Rudnicki's group demonstrated that Pax7 is required to turn adult stem cells into muscle cells during regeneration. Here, the researchers worked with mouse models and in vitro experiments to investigate whether Pax7 is sufficient to initiate muscle cell formation in injured tissue.
They show that stem cells taken from regenerating muscle in mice lacking the Pax7 gene could not become muscle cells, and that by putting Pax7 back into stem cells taken from uninjured muscle, they can generate a population of cells that readily differentiate into muscle cells. When stem cells engineered to express Pax7 proteins were injected into the muscles of mice lacking dystrophin (the protein defective in muscular dystrophy), the cells differentiated, forming dystrophin-expressing muscle cells in the defective muscle. This shows that engineered "donor cells" can differentiate in living tissue and help repair damaged muscle of recipient mice. When the researchers injected Pax7 (using a gene therapy virus) into the damaged muscle of mice lacking Pax7, they observed the production of muscle-forming cells that not only gave rise to differentiated muscle cells, but also aided in tissue repair.
The researchers argue that these results "unequivocally establish" Pax7 as a key regulator of muscle cell differentiation in specific populations of adult stem cell
Contact: Mark Patterson
Public Library of Science