EurekAlert! notes progress in manipulating existing repair systems in the body: "we asked, 'What would be the most ideal, natural way of fixing any sort of problem like this?' If you look at nature, the best way is to simply re-grow the tissue. We know that if we take out a piece of the liver, our body has programming to grow it back to how it was ... [scientists] first identified the signals in the rat heart that currently prevent the ability to re-grow damaged heart tissue. The researchers then manipulated those signals so the heart could work to regenerate itself. ... [researchers] investigated myocardial regeneration by initiating heart cell division and replication. They did this by expressing the cell-cycle regulator, a protein called cyclin A2. It is unique in its control at two major transitions of the cell cycle and is the only cyclin that is completely silenced after birth in mice, rats and humans. This approach - using cyclin A2 expression via gene transfer - yielded improved myocardial function."