New Perspectives on Regeneration of the Heart

Abstract

### De novo cardiomyocytes from within the activated adult heart after injury Smart et al Nature . 2011. doi:10.1038/nature10188 Can the adult mammalian heart regenerate and replace lost or damaged tissue? Text books suggest it cannot but recent studies suggest we may have to revisit this issue. Until recently, regeneration of the heart was thought to be restricted to fish and amphibians. For instance, hearts of zebrafish can regenerate completely within just 2 months of surgical amputation of up to 20% of the ventricle.1 This occurs by proliferation and dedifferentiation of mature cardiac myocytes.2 By contrast, severe injury of the adult mammalian heart leads to the formation of scar tissue, which replaces damaged and lost cardiac myocytes. Interestingly, neonatal mammalian hearts were recently shown to have some regenerative capacity, not unlike zebrafish, although this was lost beyond 7 days of age.3 In the last decade, several studies have described evidence for cardiac stem cell populations within the postnatal mammalian heart, which appear able to form cells with cardiac myocyte properties in culture and after transplantation back into the heart (reviewed in Rasmussen et al4). This has encouraged the search for ways to stimulate these endogenous cardiac stem cells to proliferate and differentiate into cardiac myocytes and vascular cells in situ to regenerate the injured heart even though their exact identity is unknown. In a recent study for example, Loffredo et al cleverly used genetically engineered mice to demonstrate at least some degree of endogenous myocardial replacement after an experimentally induced heart attack (myocardial infarction).5 Cardiac myocytes were …