The mammalian heart may possess the ability to renew seriously damaged tissue, researchers say. Previously only certain non-mammalian species were thought to have such potent powers of regeneration. But according to a report published today in the early online edition of the Proceedings of the National Academy of Sciences, a strain of laboratory mice dubbed MRL mice succeeded in regenerating heart tissue without the aid of drugs or other treatments.

Ellen Heber-Katz of the Wistar Institute and her colleagues damaged the right ventricles of both MRL mice and control animals and monitored their recovery for up to 60 days. The results were striking. As many as 20 percent of the heart cells in the MRL mice divided and regenerated as compared to less than 3 percent in the regular mice. "In these adult [MRL] mice, cells in the region of an injury to the heart tissue were replaced over time by new cells that were indistinguishable from neighboring health heart cells," Heber-Katz says. "After two months, the damaged heart tissue looked normal and functioned well."

Because the ability to regenerate tissue is inherent to the MRL mice (no interventions such as drugs or transferred cells were used to initiate the healing), the team plans to investigate genetic differences between MRL mice and other mouse strains. Such comparisons will help scientists to better understand this lone example of mammalian heart regeneration, and may ultimately lead to better drugs for treating injury and disease.