Many fish can replace lost cardiac tissue throughout their lives, but adult mammals cannot. Researchers have now discovered a stage very early in life at which mammals can mend their own hearts through the replication of cells called cardiomyocytes.

Hesham Sadek and Eric Olson at the University of Texas Southwestern Medical Center in Dallas and their team surgically removed about 15% of muscle tissue from the ventricle walls of 1-day-old mice. One week later, they found evidence of cardiomyocyte proliferation in the heart. The animals fully recovered their muscle tissue and organ function within two months. The same procedure performed on 7-day-old mice did not lead to cardiomyocyte proliferation or recovery.

This work may lead to new strategies for reawakening regeneration in the adult mammalian heart after injury.

Science 331, 1078–1080 (2011)