Stem cells cut heart damage in muscular dystrophy mice
|Treatment with stem cells derived from blood vessels spurred nestin-positive stem cells already present in the heart to form new cardiac muscle cells (see arrows).--Courtesy of Suzanne Berry-Miller|
Stem cells could reduce or even prevent heart damage in people with the inherited muscle-wasting disease Duchenne muscular dystrophy, according to results from mouse studies published in Stem Cells Translational Medicine.
The lack of dystrophin in Duchenne muscular dystrophy stops the muscle cells from anchoring in place. The cells tear and die, and are then replaced by scar tissue. This leads to the disease's most obvious symptom: Weakness in the skeletal muscles and loss of the ability to walk. However, the same damage also happens in the heart and patients develop dilated cardiomyopathy, where the heart becomes enlarged and weakened. Despite improvements in treatment and management of Duchenne muscular dystrophy, about 20% of people with the disease will die from heart problems.
"Right now, doctors are treating the symptoms of this heart problem by giving patients drugs to try to prolong heart function, but that can't replace the lost or damaged cells," says Suzanne Berry-Miller of the University of Illinois, who led the study.
To try to tackle the heart damage, the researchers took a type of stem cells known as aorta-derived mesoangioblasts and injected these into the hearts of dystrophin-deficient mice. The stem cells, which have a working copy of the dystrophin gene, prevented or delayed heart problems in mice with no signs of heart damage.
The cells seemed to have three effects. They became new healthy heart muscle cells, they triggered existing stem cells to become new heart muscle cells and they stimulated the growth of new blood vessels. But Berry-Miller wasn't clear which of these improved the outcomes for the mice. The stem cells could be used as therapeutics in their own right, or could point toward targets to develop new drugs with new mechanisms of action.
However, in mice that already had heart damage, the treatment wasn't effective and could potentially even make the situation worse by increasing the amount of nonmuscle connective tissue, so the timing of these treatments could be crucial in order to prevent damage from occurring and avoid the risk of worsening existing damage.
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