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Muscular dystrophy: new focus on myoblasts.

A controversial scientific report claims that a new type of cell therapy boosts the muscle strength of boys suffering from Duchenne's muscular dystrophy, the most severe form of this muscle-wasting disease. However, the new report already has drawn vocal criticism from a number of scientists who urge people to view the findings with extreme caution.

The study will be published in the May Cell Transplantation, a new peer-reviewed scientific journal published by Pergamon Press. The principal investigator, Peter K. Law, left the University of Tennessee in Memphis in January 1991 to start his own privately funded institute, the Memphis-based Cell Therapy Research Foundation.

Scientists now know that people with Duchenne's muscular dystrophy have a defective gene that causes the devastating muscle weakness. The disease mostly strikes males and usually kills them by age 20.

To correct the genetic flaw, Law and other researchers have turned to myoblast-transfer therapy, a treatment in which doctors inject diseased muscles with healthy but immature muscle cells. These cells, called myoblasts, carry the crucial gene for dystrophin, a key muscle protein. The myoblasts fuse with the defective muscle cells, a process that yields the missing dystrophin.

In 1990 Law used that technique to treat Sam Looper, a boy with Duchenne's muscular dystrophy who was 9 years old at the time. After receiving myoblast injections in one big toe, Looper could wriggle his toe more vigorously, Law reported (SN: 6/16/90. p. 380).

Now, Law claims more convincing proof of the treatment's efficacy. He and his colleagues injected Looper and 20 other boys who have Duchenne's muscular dystrophy with solutions containing billions of healthy myoblasts. This time, Law injected the cells into 69 major muscle groups in the legs and buttocks.

To prevent rejection of the myoblasts, which are obtained from healthy male donors, the team gave the boys the immunosuppressant drug cyclosporine.

The team documented the strength of each muscle three months prior to the injection period and again three months later. A sampling of preliminary data revealed that 43 percent of the treated muscles increased in strength, 38 percent stayed the same and 19 percent continued to lose strength.

While making no claims for a cure, Law says some of the treated boys experienced a dramatic improvement in muscle power.

Other researchers remain skeptical of Law's report. "There are some concerns with this paper," comments Donald S. Wood, director of science and technology for the Tucson-based Muscular Dystrophy Association (MDA). Wood says that Law's group failed to document each child's long-term decline in muscle strength, raising the possibility that the observed benefit is not real. Although the muscles of boys with muscular dystrophy do deteriorate over time, individual muscles can exhibit a temporary increase in strength even without treatment, Wood observes. Law disagrees, saying that boys show a steady muscle decline after age 6.

Neurologist Robert G. Miller at the California Pacific Medical Center in San Francisco cites another flaw in the study. He says Law's group failed to control for the effect of cyclosporine. Miller's own unpublished research, funded in part by MDA, suggests that cyclosporine temporarily improves muscle strength in boys with Duchenne's muscular dystrophy.

Law counters that his earlier research showed that myoblast transfer, not cyclosporine, produced an improvement in muscle might.

Despite the disagreements on some aspects of the new study, all those interviewed say the future of myoblast transfer remains one of great promise. "All of us working in this field are extremely optimistic," Miller says.
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Title Annotation:cell therapy treatment
Author:Fackelmann, Kathy A.
Publication:Science News
Date:Mar 14, 1992
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