Study Reveals How Stem Cells Decide To Become Either Skeletal or Smooth Muscle

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Researchers have discovered a key protein that controls how stem cells “choose” to become either skeletal muscle cells that move limbs, or smooth muscle cells that support blood vessels, according to a study published today in the Proceedings of the National Academy of Sciences (PNAS). The results not only provide insight into the development of muscle types in the human fetus, but also suggest new ways to treat atherosclerosis and cancer, diseases that involve the creation of new blood vessels from stem cell reserves that would otherwise replace worn out skeletal muscle. The newly discovered mechanism also suggests that some current cancer treatments may weaken muscle, and that physician researchers should start watching to see if a previously undetected side effect exists.

Thanks to stem cells, humans develop from a single cell into a complex being with as many as 400 cell types in millions of combinations. The original, single human stem cell, the fertilized embryo, has the potential to develop into every kind of human cell. As we develop in the womb, successive generations of stem cells specialize (differentiate), with each group able to become fewer and fewer cell types. One set of mostly differentiated stem cells has the ability to become bone, blood, skeletal muscle or smooth muscle. Many human tissues keep a reserve of stem cells on hand in adulthood, ready to differentiate into replacement parts depending on the stimuli they receive. If body signals that skeletal muscle needs replacing, the stem cells take that route. If tissues signal for more blood vessels, the same stem cells may become smooth muscle that supports the lining of blood vessels.

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