Reversing muscular dystrophy comes closer to reality

November 16th, 2007 - 5:42 pm ICT by admin  

Washington , Nov 16 (ANI): Scientists have come a step closer to reversing muscular dystrophy by identifying a compound that eliminates myotonia, a key symptom of the disease in mice.

Myotonic dystrophy is the most common form of muscular dystrophy in adults. It is characterised by progressive muscle wasting and weakness, particularly in the lower legs, hands, neck, and face.

People with myotonic dystrophy have prolonged muscle tensing (myotonia) and are not able to relax certain muscles after use. The condition is particularly severe in the hand muscles and can cause a persons grip to lock, making it difficult to perform rapid, repeated movements.

The study at the University of Rochester Medical Center (URMC) designed a synthetic RNA-based molecule that, when injected into mice with myotonic dystrophy, restored a critical cellular mechanism, or pathway, that controls electrical activity in muscles.

The researchers found that once this pathway was re-established, normal muscle function was returned.

The significance of this work is the proof of concept that a fundamental aspect of this genetic disease can be reversed even after it is very well established, said Charles Thornton, M.D., co-director of the URMC Neuromuscular Disease Center and senior author of the study.

It encourages us to believe that other parts of the disease could be reversible as well, he added.

The study also unravelled the genetic flaw that caused the disease by showing that messenger RNA(mRNA) was responsible for transmitting genetic information out of the nucleus and into the main part of the cell, where instructions from the molecular blueprint get carried out.

The authors found that the regulation of muscle activity and relaxation was basically electrical and was governed by the movement of small charged particles into and out of muscle cells in a very controlled manner. This electrical flow went through very specific pathways, including one called the chloride channel.

In individuals with myotonic dystrophy, the chloride channel is essentially disabled, causing electrical signals in muscles stay on for too long, resulting in unstable muscle control like when someone grasps anothers hand and cant let go.

The team also created a synthetic RNA-based compound that restored proper genetic instruction for building the chlorine channel. When the compound, called a morpholino, was injected into the muscle cells of a set of mice with myotonic dystrophy, the chloride channel was restored and the myotonia all but disappeared and did not return for several weeks.

This material is incredibly stable in the cells once we get it inside the muscle, said URMC neurologist Thurman Wheeler, M.D., lead author of the study.

And the effects are surprisingly prolonged, which makes it potentially more attractive as a treatment, he added.

This work should provide hope and encouragement to people with myotonic dystrophy and their families, said Thornton .

This is a progressive and debilitating condition, but there are early indications that effective treatments are possible. To see a problem like myotonia disappear after it has been present for a long time is certainly a hopeful sign.

As we move forward, we should not be content to keep this condition from getting worse. We should set our set our sights on making it better, he added.

The study appeared online in the Journal of Clinical Investigation. (ANI)

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