Heart Regeneration In A Reptilian Model

RM 210

Teleost fish and urodele amphibians are able to fully regenerate lost or damaged cardiomyocytes even as adults. Some mammal species (e.g., neonatal mice) appear to be able to regenerate the myocardium, whereas others (e.g., humans) are incapable of repair and regeneration. Whether this regenerative capacity exists in other vertebrate clades has not yet been described. In order to determine whether “reptiles” (non-avian sauropsids) have the capacity to regenerate cardiac tissue following injury, we developed experimental models similar to those used in zebrafish and mice— ventricular resection and cryoinjury—and tested them in the American alligator (Alligator mississippiensis). The alligator, with its four-chambered heart, and independent systemic and pulmonary pressure generation, can be a useful model in studies of cardiac regeneration. Hatchling alligators were injured or sham-operated, allowed to recover, and kept for up to four months. There is indication of significant increase in proliferation of cardiomyocytes in and around the wound area of injured hearts 14 days post-injury (dpi). However, by 60 dpi, a collagen-rich scar persists and assumes trabeculated morphology more similar to that seen in zebrafish. This suggests that regenerative capacity may not be present in crocodilia. Similar studies on more taxa are needed in order to elucidate evolutionary patterns with regard to regenerative capacity among vertebrate clades.