How can the adult zebrafish and neonatal mice teach us about stimulating cardiac regeneration in the human heart?

The proliferative capacity of mammalian cardiomyocytes diminishes shortly after birth. In contrast, adult zebrafish and neonatal mice can regenerate cardiac tissues, highlighting new potential therapeutic avenues. Different factors have been found to promote cardiomyocyte proliferation in zebrafish and neonatal mice; these include maintenance of mononuclear and diploid cardiomyocytes and upregulation of the proto-oncogene c-Myc. The growth factor NRG-1 controls cell proliferation and interacts with the Hippo–Yap pathway to modulate regeneration. Key components of the extracellular matrix such as Agrin are also crucial for cardiac regeneration. Novel therapies explored in this review, include intramyocardial injection of Agrin or zebrafish-ECM and NRG-1 administration. These therapies may induce regeneration in patients and should be further explored. The heart pumps blood across the body carrying nutrients and oxygen where they are needed. If the heart is damaged (e.g., after a heart attack), it may lose its ability to pump blood, and this can lead to heart failure, where the heart cannot meet the body's needs, leaving the affected person tired and breathless. This occurs because the human heart unfortunately has a limited ability to heal and regain function. Current therapies for heart injuries focus on minimizing the problems resulting from the injury but cannot recover damaged heart tissue. Scientists have found that in contrast to adult human hearts, the hearts of baby mice and zebrafish can repair themselves after injuries and recover normal function. This review highlights some important mechanisms that occur in the hearts of baby mice and zebrafish, which may help contribute to their regenerative abilities. These mechanisms involve small messenger chemicals that stimulate heart cells to replicate and reform normal heart tissues. Further research into these pathways may help develop new therapies for damaged human hearts and help them regain function. Unlike humans, adult zebrafish and neonatal mice can regenerate cardiac tissues. Key regenerative processes that occur in zebrafish and neonatal mice may help the development of future therapeutic avenues for many cardiovascular diseases.