Today's Science Daily reported a study by a Boston research group (Mark Keating's) that has identified a drug delivery technique using a drug called periostin that could rebuild heart tissue without stem cells. This drug causes heart cells to re-enter the cell division cycle 100 times more than normal 12 weeks after a mouse was given a heart attack. In any other tissue, this abundant increase in division would cause a tumor. But since heart cells hardly ever divide, what they saw was an increase from 0.01% to 1.0% when the marker for cell division (BrdU for my biologist readers) was given for 6 days. Just as a way of reference, that much BrdU given to an animal would cause almost 50% of the intestine to be positive.
These drastic increases in cell division are what is needed in order to harness any latent ability in the heart for cell division. While this group did find that heart function improved after treatment with their drug patch, it is unclear to me whether this is due to the effects of cell division or other effects of the drug, namely different scar properties.
The original document (needing institutional subscription) is here.