Stem Cells Overpower Muscle Disease

12 December 2007 (All day)

Mirella Meregalli/University of Milan

Muscle bound.
Muscles from mice treated with modified human stem cells show human dystrophin-producing muscle fibers (yellow) integrated among mouse muscle fibers (red).

The recent breakthrough of skin cells reprogrammed to behave like embryonic stem cells has stolen the spotlight (ScienceNOW, 6 December), but adult stem cells are proving that they have advantages of their own. In the 13 December issue of Cell Stem Cell, researchers report using stem cells from patients afflicted with a form of muscular dystrophy to correct the disorder in mice. The results suggest that this strategy could one day treat muscular dystrophy in humans as well as other genetic disorders.

Duchenne muscular dystrophy, which predominantly strikes boys, is caused by a mutation in the gene for a protein called dystrophin that is essential for proper muscle function. The condition leads to muscle degeneration, and patients usually die in their 30s. A particular type of stem cell found in muscle can give rise to new muscle tissue, so a team led by geneticist Luis Garcia of Généthon, a nonprofit biotechnology firm in Évry, France, investigated whether these cells could be used to reverse the dystrophin problems.

The researchers first obtained the stem cells from patients via a muscle biopsy. Next, they used a virus to insert a gene into the cells that corrects the mutation in the dystrophin gene. The researchers then injected the modified stem cells into arteries of the legs of mice with muscular dystrophy. In just 3 weeks, muscles in the foot, shin, and thigh began expressing human dystrophin protein, indicating that the stem cells had given rise to muscle cells that had taken up residence in the muscles of the mice.

The real proof came in treadmill tests. The treated mice were able to run longer, maxing out at 15 minutes, than untreated ill animals, which managed only 10 minutes before becoming exhausted, the researchers report.

Garcia says his team now plans to test the strategy in people with muscular dystrophy. He adds that the technique could be used to treat a variety of genetic diseases, including other muscle and skin disorders.

Stem cell scientist Robert Lanza of Advanced Cell Technology in Worcester, Massachusetts, calls the strategy promising. He adds that the stem cells used in the study have advantages over reprogrammed skin cells, including eliminating the tricky business of inducing the cells to become muscle cells, but he notes that both types of cells could pose risks because the virus used to modify them could cause cancer.

Geneticist Kay Davies of the University of Oxford, U.K., says that in order for the approach to be successful in humans, the stem cells will have to be delivered to every muscle. That could prove an enormous challenge, she notes, because of the repeated injections and high costs involved.

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