Transient Regenerative Potential of the Neonatal Mouse Heart

The regenerative capacity of adult human hearts afterinfarction seems vestigial at best, perhaps because of the poor proliferative capacity of terminally differenti-ated cardiomyocytes and desecration of the local environ-ment that would otherwise be conducive of stem cell-mediated repair or loss of stem cells, or both. In a recent edition of the journal Science, Porello et al set a new benchmark in this field by showing that the hearts of neonatal mice have, in contrast, an impressive regenera-tive capacity after surgical resection, albeit one that is lost almost immediately as cardiomyocytes exit the cell cycle and mature. In a technical tour de force, Porello et al1 report that day 1 neonatal mice subjected to resection of the apex of the left ventricle (amounting to 15 % of the ventricular myocardi-um) not only survive but also show complete regeneration o