Heart ventricle regeneration in the lizard Eublepharis macularius, the leopard gecko.

Among mammals, injury to the heart typically results in scar formation and diminished cardiovascular function. In contrast, some teleost fish and salamanders can replace damaged heart tissue and restore overall function. For most species, however, less is known. Here, we investigate cardiac self-repair in an amniote capable of multi-tissue regeneration, the leopard gecko (Eublepharis macularius). To create a heart lesion, we placed a liquid nitrogen-cooled metal probe directly onto the ventricle. The result was a cryoinjury to ~20% of the ventricle. Cardiac cryoinjury induced localized cardiac cell death, followed by an increase in cell proliferation by injury-adjacent cardiomyocytes and non-cardiomyocytes. By 100 days, the histology of the ventricular myocardium was nearly completely restored. Echocardiography and invasive hemodynamic monitoring demonstrated that global cardiac function is restored within this timeframe, verifying functional replacement of the myocardium. To explore the molecular basis, we performed bulk RNA sequencing of the injury-adjacent tissue and found that many of the molecular mechanisms common to other cardiac regenerating species, including genes involved in heart development, glycolysis, and extracellular matrix deposition, are also conserved in geckos. Taken together, this work expands the comparative framework of heart regeneration to include reptiles and indicates that the ability to replace missing or damaged cardiomyocytes is shared across >50 million years of evolution.