Marshall, L.N. et al. PNAS 116, 3614–3623 (2019)

After injury, adult human hearts cannot compensate for the loss of damaged cardiomyocytes, owing to their limited regenerative capacity. Lost cardiomyocytes are replaced by fibrotic tissue through a remodelling process that can lead to heart failure. Zebrafish hearts, by contrast, can regenerate throughout their lifetime; researchers are trying to understand these species-specific differences to inform new therapeutic approaches for cardiac regeneration.

A new study using Xenopus laevis as a model for cardiac regeneration shows that tadpole hearts can regenerate until the larvae reach metamorphosis, which is the transition stage between the larval and the juvenile phenotype. Thyroid hormone excess or deprivation in tadpoles reduced cardiac regenerative capacity, indicating that fine-tuning of thyroid hormone availability might be necessary for successful cardiac regeneration.