A new technique could make tissue regeneration cheaper and safer for health-care systems and their patients. The study has identified new ways in which proteins and various biological molecules  -  known as growth factors  -  can work together to turn cells on the surface into cells that form the middle layer of the heart valve.... A new technique could make tissue regeneration cheaper and safer for health-care systems and their patients. The study has identified new ways in which proteins and various biological molecules  -  known as growth factors  -  can work together to turn cells on the surface into cells that form the middle layer of the heart valve.... A