The heart was once thought unable to regenerate at all but it's now known that around 1% of cardiomyocytes turn over each year. These cells have proved hard to pin down, but new research on mice has discovered a specialized cardiomyocyte that is able to divide. The newly discovered cell is importantly not a stem cell, but is unusual within the heart in its dividing capacity. The discovery could provide a target for research on increasing innate heart regeneration - boosting the process already taking place.
Read more at The Scientist