by Graydyl

Created on: May 22, 2008   Last Updated: May 23, 2008

Gene therapy sounds like a dream come true for those with muscular dystrophy or other diseases. But gene therapy could also turn into gene doping for athletes desiring that extra boost of energy or speed to win. If gene therapy is poised to become a practical medical treatment, gene doping for personal wants is not far behind. In truth, the start of research toward genetically enhancing muscle size and strength was not focused on serving elite athletes. If gene therapy becomes a worldwide medical practice, will it be so commonplace that the world may accept the manipulation of genes to enhance athletic performance?

In the most common and most severe version of MD (Duchenne muscular dystrophy), an inherited gene mutation results in the absence of a protein called dystrophin. Dystrophin protects muscle fibers from injury by the force that they exert during regular movement. Muscles are good at repairing themselves, but their normal regenerative mechanisms cannot keep up with the excessive rate of damage in MD. In aging muscles the rate of damage may be normal, but the repair methods become less responsive. As a result, in both aging and Duchenne MD, muscle fibers die and are replaced by infiltrating fibrous tissue and fat.

Manufacturing new proteins that can repair the outer membrane of existing fibers and plumping their interior with new myofibrils requires the activation of the necessary genes within the muscle cell's nuclei, and when the demand for myofibrils is great, additional nuclei are needed to support the muscle cell's manufacturing capacity. Local satellite cells residing outside the muscle fibers answer this call. First, these muscle-specific stem cells multiply by normal cell division. Then, some of their progeny fuse with the muscle fiber, contributing their nuclei to the cell. Both progrowth and antigrowth factors are implicated in regulating this process. Satellite cells respond to insulinlike growth factor I, or IGF-I, by undergoing a greater number of cell divisions. The key causal question can be formulated: Why is gene alteration or transfer so effective in helping medical cases such as muscle dystrophy?

A few hypotheses were generated to answer this question: Modifying a tiny virus (AAV) with a synthetic gene that would produce IGF-I only in skeletal muscle would strengthen muscles; Overproduction of IGF-I throughout the skeletal muscle would hasten muscle repair.

A major obstacle to gene therapy was figuring out how to get the chosen gene into

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