Some organs in the human body deal with injury better than others. A flesh wound or muscle tear might hurt, but, assuming you are otherwise healthy, both will heal. The prognosis for a heart attack, on the other hand, is not so clear-cut.
It has long been thought that cardiac cells (cardiomyocytes) lack the capacity for self-renewal and repair, impeding the chances of a full recovery from a heart attack. However, recent evidence suggests that the heart might harbor stem cells after all and that such cells can be transformed into cardiomyocytes.
In a new study published in the premier open-access online journal PLoS Biology, Neal Epstein and colleagues report that a special group of cells (called skeletal precursors of cardiomyocytes, or Spoc cells) isolated from the skeletal muscle of adult mice can turn into beating cardiomyocytes in a test tube within days of isolation. When these cells are injected into mice with heart damage, they migrate to the damaged tissue and differentiate into cardiac muscle cells.
Epstein and colleagues argue that Spoc cells are more likely to be precursors to cardiomyocytes than to be some other type of skeletal muscle stem cell. This is based on an absence of protein markers for skeletal muscle cells in Spoc cells, as well as the fact that Spoc-derived cells display spontaneous rhythmic beating and express cardiac markers, whether they are grown in a test tube or have migrated to injured hearts in study mice.
The authors can't say why skeletal muscle would harbor cardiac stem cells, but for now, the Spoc cells provide a valuable tool for studying heart cell differentiation. And with time, they might prove an important resource for developing cell-based therapies for heart disease.
Citation: Winitsky SO, Gopal TV, Hassanzadeh S, Takahashi H, Gryder D, et al. (2005) Adult murine skeletal muscle contains cells that can differentiate into beating cardiomyocytes in vitro. PLoS Biol 3(4): e87.
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