Although some invertebrates can regrow parts of their hearts after damage, that has not been known to be possible for mammals. Until now, that is. Hesham Sadek and his colleagues from the University of Texas Southwestern Medical Center have observed heart regeneration in newborn mice.
The researchers removed 15% of the heart tissue from newborn mice. To their surprise, the infant mice were able to regrow the tissue. The resultant hearts looked and performed exactly like normal hearts. This ability was retained until the mice were seven days old, at which point they lost the capacity to grow new heart muscle. To put that in perspective, mice reach maturity between 6 to 8 weeks and can live for two or three years. Thus, the ability to fix heart problems continues for a large part of the mouse’s ‘childhood’.The scientists believe that the infant mice’s cardiomyocytes, the beating cells of the heart, can stop beating and divide, repairing the damage. The next step is to figure out whether adult heart cells could be reprogrammed in the same manner. If so, there may be a way to induce human cardiomyocytes to repair heart defects.