"At that point, there must be mechanisms that come into play to prevent the heart muscle cells from dividing," Olson said.
The researchers thought of two possible mechanisms to explain the regeneration. One might involve spurring the remaining muscle cells to proliferate and repair the injury. Or possibly there are stem cells -- undifferentiated cells that give rise to all the different types of cells in the human body -- which are mobilized in response to the injury.
Upon further study, Olson and his colleagues determined that all the new heart muscle cells seemed to come from preexisting muscle cells rather than stem cells.
"A majority of the cells that contributed to regeneration were existing heart cells, not stem cells. That's huge," said Badylak. "That suggests that cells have been pulled out of the cell site. They've differentiated, [then] divide and form new cells."
"Now the question is maybe we can control this ability to regenerate at a site of interest," he added. "If that's possible, then the therapeutic potential is huge."
There's more on the science of regenerative medicine at the Indiana University Center for Regenerative Biology and Medicine.
SOURCES: Eric N. Olson, Ph.D., professor and chairman, molecular biology, University of Texas Southwestern Medical Center, Dallas; Stephen Badylak, D.V.M., Ph.D., M.D., professor, department of surgery and deputy director, tissue engineering, McGowan Institute for Regenerative Medicine, University of Pittsburgh, and president, Tissue Engineering and Regenerative Medicine International Society; Feb. 25, 2011, Science
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