Stem cells repair heart only early in life

Stem cells can replace dead heart tissue after a heart attack very early in life, but they lose that ability in adults, U.S. and German researchers say. Senior author Michael Kotlikoff, dean of Cornell's College of Veterinary Medicine, and colleagues at the University of Bonn said the study involving mice found undifferentiated precursor cells grow new heart cells in a 2-day-old mouse, but not in adult mice. Kotlikoff said the finding settles a decades-old controversy about whether stem cells can play a role in the recovery of the adult mammalian heart following infarction -- in which heart tissue dies due to artery blockage. "While the existence of these cells in adults is controversial, if one did have fully capable stem cells in adults, why are there no new heart cells after an infarct? Whether this is due to a lack of stem cells or to something special about the infarct that inhibits stem cells from forming new heart cells is the question we addressed, taking advantage of the fact that the newborn mouse has these cells," Kotlikoff said in a statement. The study, scheduled to be published in the August issue of the Proceedings of the National Academy of Sciences, found that 2-day-old mice grew new heart cells and almost completely recovered from infarction, proving that the injury did not inhibit stem cells from growing new heart cells.