Muscular dystrophy heart breakthrough

Heart failure is the second most common cause of death among people with Duchenne muscular dystrophy. However researchers believe that a particular drug may help protect the hearts of those affected by this condition.

Muscular dystrophy (MD) is a collective term for a range of neuromuscular conditions, characterised by the progressive weakening and wasting of the muscles. It can affect males and females of all ages.

Duchenne MD is the most common form and it almost exclusively affects male children. The condition's main symptoms involve deterioration of muscles used for movement, but the heart is also often affected. As a result, many of those with the condition die of heart failure in their 20s.

The muscle wasting is caused by the lack of a protein called dystrophin, however researchers did not know why this weakened heart muscle cells. However researchers at the University of Michigan believe that cells lacking this protein may be less resistant to stretching.

Dr Joseph Metzger and his colleagues took individual heart muscle cells from healthy mice and from mice genetically engineered to lack dystrophin. They then stretched the cells by 20%. They found that cells lacking dystrophin were more likely to break.

This was because the cell membranes became torn as they were stretched. Calcium ions, which are essential in muscle-cell contraction, flood in though the holes causing the cells to hypercontract.

"The cell rolls into a little ball and dies", Dr Metzger explained.

However when the researchers treated the cells with a chemical called poloxamer 188, which is used to plug holes in membranes, cell death was averted. The chemical acted as a 'sticking plaster' for the muscle cells.

While poloxamer has been used to treat sickle cell anaemia in short bursts, the researchers warned that it will be a long time before the drug can be declared safe to use on people with Duchenne MD, who may have to take the drug for life.

"If issues of dosing and long-term safety can be resolved, our research suggests that poloxamer 188 could be a new therapeutic agent for preventing or limiting progressive damage to the hearts of patients", Dr Metzger said.

He added that he and his colleagues also hoped to test the drug on mice with other types of MD.

Details of this research are published in the scientific journal, Nature.

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