Researchers are working, step by step, towards the knowledge needed to reprogram cells to regenerate damage they presently let stand. Here is one small step forward: "A protein that the heart produces during its early development reactivates the embryonic coronary developmental program and initiates migration of heart cells and blood vessel growth after a heart attack ... The molecule, Thymosin beta-4 (TB4), is expressed by embryos during the heart's development and encourages migration of heart cells. ... Tremendous medical progress has been made to counter the damaging effects of heart attacks, but ordinarily, mammalian hearts are incapable of repairing themselves following damage. They are also limited in their ability to form new blood vessels. ... In this mouse study researchers found that TB4 initiates capillary tube formation of adult coronary endothelial cells in tissue culture. The molecule also encourages cardiac regeneration by inhibiting death in heart cells after an injury such as a heart attack and by stimulating new vessel growth. ... We observed that by injecting this protein systemically, there was increased cardiac function after a heart attack. We hope this protein can inhibit cell death that occurs during a heart attack in the short term, and that it may initiate new growth of coronary vessels by activating progenitor cells in the long term."