Embryonic Stem Cells Create Healthy Muscle in Mice

By Madeline Vann
HealthDay Reporter
Sunday, January 20, 2008; 12:00 AM

SUNDAY, Jan. 20 (HealthDay News) -- Researchers have coaxed embryonic mouse stem cells to grow into healthy muscle tissue, in a feat that creates new possibilities for the treatment of Duchenne muscular dystrophy (DMD).

DMD is the most common of nine types of muscular dystrophy, which is characterized by a lack of the protein dystrophin in voluntary muscles, such as those in the arms and legs. Dystrophin plays a key role in building and repairing muscle; without it, muscles deteriorate and lose function.

The University of Texas Southwestern Medical Center team focused on developing embryonic stem cells containing the gene Pax3, which triggers cells to grow into muscle tissue that will produce dystrophin.

"Embryonic stem cells can make every tissue in the body. We instructed these cells to make more skeletal muscle, and from a crowd of cells," explained study author Rita Perlingeiro. "We found a way to pull out only the ones destined to make muscle. These two steps combined resulted in a cell population capable of making muscle in a mouse with muscular dystrophy and, very importantly, the new muscle is stronger."

This is one of the few studies to test the ability of embryonic stem cells to grow in adult muscle tissue, the researchers added. The method they used also managed to avoid the risk of tumor formation in the mice.

One expert lauded the study, which appears in the Jan. 20 online issue ofNature Medicine, as a strong first step.

"By way of experiments done with mice, the paper offers a compelling 'proof of principle,' that embryonic stem cells can be turned into muscle-producing cells in the laboratory and used to deliver healthy muscle to people with Duchenne muscular dystrophy," said Paul Muhlrad, research program coordinator for the Muscular Dystrophy Association.

The researchers noted it was only necessary to regenerate a portion of the muscle tissue for the mice to regain some control. However, the process requires refining before it can be tried in humans, they added.

"At the present time, no one has yet demonstrated that genetic manipulation of human embryonic stem cells can be used to derive functional skeletal muscle progenitors from these cells, so it's far too early to tell whether this technique could lead to any potential clinical application," said Perlingeiro. "The main hurdle is to make sure we can indeed combine successfully these two approaches, and test these cells exhaustively in mouse models before we think about clinical trials."

Muhlrad also cautioned that this research is a long way from human use.

"While mice provide an excellent model system, experiments that work in mice don't always readily transfer to humans. Scientists would probably want to replicate the experiments in dog models of muscular dystrophy before moving on to human studies," Muhlrad said. Additionally, the mice had to take immunosuppressants to prevent their bodies from rejecting cells from another mouse. The ideal approach would be to use a body's own stem cells to avoid the issue of rejection.

More information

To learn more about the different types of muscular dystrophy, visit the Muscular Dystrophy Association.

SOURCES: Paul Muhlrad, Ph.D., research program coordinator, Muscular Dystrophy Association, Tucson, Ariz.; Rita Perlingeiro, Ph.D., assistant professor, developmental biology and molecular biology, Department of Developmental Biology, University of Texas Southwestern Medical Center at Dallas; Jan. 20, 2008,Nature Medicineonline



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