If you know exactly how to order cells around, you don't need stem cells to spur healing that would not normally take place: reaearchers "have devised a method to coax heart muscle cells into reentering the cell cycle, allowing the differentiated adult cells to divide and regenerate healthy heart tissue after a heart attack ...The key ingredient is a growth factor known as neuregulin1 (NRG1 for short) ... To my knowledge, this is the first regenerative therapy that may be applicable in a systemic way ... For instance, he added, people might one day go to the clinic for daily infusions of NRG1 over a period of weeks. ... In principle, there is nothing to preclude this going into the clinic. Based on the all the information we have, this is a promising candidate ... The heart had long been considered an organ largely incapable of repairing itself. Heart muscle cells, also known as cardiomyocytes, do proliferate during prenatal development. ... recent evidence has shown that adult heart muscle cells can replace themselves at some low level, with perhaps half of the cells in the heart turning over in the course of a lifetime ... The new study provides multiple lines of evidence for this turnover ability - including video of the cells in action - and shows that neuregulin1 can ramp up the process."