Purified Stem Cells Restore Muscle In Mice With Muscular Dystrophy

"I'm very excited about this," said lead author Amy J. Wagers, Ph.D., Principal Investigator in the Joslin Section on Developmental and Stem Cell Biology, principal faculty member at the Harvard Stem Cell Institute and Assistant Professor of Stem Cell and Regenerative Biology at Harvard University. "This study indicates the presence of renewing muscle stem cells in adult skeletal muscle and demonstrates the potential benefit of stem cell therapy for the treatment of muscle degenerative diseases such as muscular dystrophy."

The study was designed to test the concept that skeletal muscle precursor cells could function as adult stem cells and that transplantation of these cells could both repair muscle tissue and regenerate the stem cell pool in a model of Duchenne muscular dystrophy, she said. The research is published in the July 11 issue of Cell.

Duchenne muscular dystrophy is the most common form of the disease and is characterized by rapidly progressing muscle degeneration. The disease is caused by a genetic mutation and there is currently no cure.

The data from this new study demonstrate that regenerative muscle stem cells can be distinguished from other cells in the muscle by unique protein markers present on their surfaces. The authors used these markers to select stem cells from normal adult muscle and transferred the cells to diseased muscle of mice carrying a mutation in the same gene affected in human Duchenne muscular dystrophy.

"Once the healthy stem cells were transplanted into the muscles of the mice with muscular dystrophy, they generated cells that incorporated into the diseased muscle and substantially improved the ability of the treated muscles to contract," said Wagers. "At the same time, the transplantation of the healthy stem cells replenished the formerly diseased stem cell pool, providing a reservoir of healthy stem cells that could be re-activated to repair the muscle again during a second injury."

According to the paper, these cells provide an effective source of immediately available muscle regenerative cells as well as a reserve pool that can maintain muscle regenerative activity in response to future challenges.

"This work demonstrates, in concept, that stem cell therapy could be beneficial for degenerative muscle diseases," Wagers said.

Wagers also said the study will lead to other studies in the near-term that will identify pathways that regulate these muscle stem cells in order to figure out ways to boost the normal regenerative potential of these cells. These could include drug therapies or genomic approaches, she said. In the long-term, the idea will be to replicate these findings in humans.

"This is still very basic science, but I think we're going to be able to move forward in a lot of directions. It opens up many exciting avenues," she said.

The Wagers Lab at Joslin studies both hematopoietic stem cells, which constantly maintain and can fully regenerate the entire blood system, as well as skeletal muscle stem cells, involved in skeletal muscle growth and repair. The work is aimed particularly at defining novel mechanisms that regulate the migration, expansion, and regenerative potential of these two distinct adult stem cells.

This study was funded by in part by a Burroughs Wellcome Fund career award, Seed and Program Grants from the Harvard Stem Cell Institute and grants from Jain Foundation, Beckman Foundation, and the National Institutes of Health.

Others participating in the research were Massimiliano Cerletti, Sara Jurga and Jennifer L. Shadrach of the Joslin Section on Developmental and Stem Cell Biology and the Department of Stem Cell and Regenerative Biology, Harvard University and Harvard Stem Cell Institute; and Carol A. Witczak, Michael F. Hirshman and Laurie J. Goodyear of the Joslin Section on Metabolism.