Mending a broken heart—targeting cardiomyocyte regeneration: a literature review

BACKGROUND AND OBJECTIVES: Cardiovascular diseases have been the leading cause of death globally for decades. Pharmacological advances targeting the sympathetic nervous system, renin-angiotensin-aldosterone system, and fibrosis slow the progression of diverse cardiovascular diseases. However, ongoing cardiomyocyte loss is inevitable in divergent cardiovascular diseases, eventually leading to heart failure as the end stage. In this review, we focused on the key biomedical findings and underlying principles of cardiomyocyte regeneration. METHODS: Literature regarding the key findings in cardiomyocyte regeneration research, including controversies on the origins of newly formed cardiomyocytes, potential barriers and strategies to heart regeneration, and the key animals, models, and methods applied in the study of heart regeneration, were broadly researched using the PubMed and Web of Science databases. KEY CONTENT AND FINDINGS: In the mammalian heart, cardiomyocytes proliferate during the embryonic and early postnatal stages, while the capability of proliferation disappears in the adult stage. An increasing amount of evidence suggests that cardiomyocytes self-renew at a very limited level and that most newly formed cardiomyocytes originate from pre-existing cardiomyocytes and not cardiac progenitor cells (CPCs). Several potential barriers to heart regeneration have been addressed, including metabolic switch, a large increase in multinucleated and polyploid cardiomyocytes, and alteration in the epigenome and transcriptome. In addition, immune system evolution is also associated with the loss of regenerative capacity. However, the activation of resident cardiomyocytes, somatic cell reprogramming, and direct reprogramming, in addition to the promotion of neovascularization and immune modulation, constitute the new insights into those strategies that can boost cardiac regeneration. CONCLUSIONS: Heart regeneration is one of the most popular fields in cardiovascular research and represents a promising avenue of therapeutics for mending a broken heart. Despite the controversies and challenges, a clearer picture of adult mammalian cardiac regeneration is emerging.