"Mammalian heart renewal by pre-existing cardiomyocytes"
Controversy reigns in the area of adult heart cell regeneration. Until recently it was thought there was no adult regenerative capacity, but even though this dogma has now been abolished, the rate at which it occurs and the source of this de novo regeneration is still debated. Some studies suggest that there is a high level of differentiation of progenitors to cardiomyocytes (Hosoda et al) and their turnover is high (Kaystura et al), while other studies suggest that new cardiomyocytes are made at a very low level (Soonpaa and Field, Bergmann et al and Walsh et al). Additional controversy stems from the question of the source of these cardiomyocytes and therefore the plasticity of the heart; do they come from the division of existing myocytes (Kikuchi et al), progenitors residing in the heart (Beltrami et al) or from exogenous niches, such as the bone marrow (Orlic et al)? To attempt to address these questions, researchers from the laboratory of Richard T. Lee at the Harvard Stem Cell Institute, Cambridge, Massachusetts, USA have used multiple tracking techniques to demonstrate that the genesis of cardiomyocytes indeed occurs at a low rate through the division of pre-existing cardiomyocytes, a phenomenon which is exacerbated by injury (Senyo et al).