N-Cadherin promotes cardiac regeneration by potentiating pro-mitotic β-Catenin signaling in cardiomyocytes

Loss of cardiomyocytes (CMs) following injury can lead to myocardial dysfunction, heart failure (HF) and ultimately death. The limited regenerative ability of the adult human heart after injury, however, poses a significant obstacle to restore cardiac function effectively. While mammalian hearts, including those of mice and humans, do have the potential to regenerate, this capacity is restricted to a narrow window during early stages of life. The molecular mechanisms governing the regenerative capacity of mammalian hearts remain incompletely understood. Exploring a comparative transcriptome analysis in regenerative neonatal vs. non-regenerative adult mouse CMs, we identified N-Cadherin, a member of Ca2+-dependent cell adhesion protein cadherin superfamily, as a potential novel regulator of CM proliferation/renewal. The primary objectives of this study were to elucidate the molecular mechanisms through which N-Cadherin regulates cardiomyocyte proliferation and regeneration, and to determine the therapeutic potential to promote CM renewal and restore cardiac function following injury by targeting N-Cadherin. Cardiac N-Cadherin expression exhibits a strong positive correlation with that of cell cycle- and proliferation-related genes. Its expression levels show an age-dependent reduction, with a 75% decrease of N-Cadherin in adult, compared to P1 neonatal, CMs. N-Cadherin expression is upregulated in the neonatal mouse heart in response to apical resection, especially in the peri-injury region, coinciding with increased CM mitotic activities in the neonatal heart. Knocking down N-Cadherin reduced, whereas overexpression of N-Cadherin increased, the proliferation activity of neonatal mouse CMs and human induced pluripotent stem cell-derived CMs. Mechanistically, increased N-Cadherin potentiates CM renewal through direct binding with and stabilization of a pro-mitotic transcription regulator β-Catenin, leading to increased CMs proliferative activity. Deletion of β-Catenin-binding domain on N-Cadherin abrogated its pro-regenerative activity. Importantly, targeted depletion of N-Cadherin in CMs resulted in incomplete cardiac repair/regeneration and excessive fibrotic scar formation in neonatal mouse hearts following injury. Cardiac-specific overexpression of N-Cadherin in adult mouse heart using adeno-associated viral vectors, by contrast, resulted in increased CM proliferation and protected against myocardial infarction-induced adverse remodeling and contractile dysfunction. Adherent junction protein N-cadherin is demonstrated to play a crucial role in maintaining CM renewal potential by post-translational stabilization of β-Catenin. Enhancing N-cadherin expression levels and downstream signaling activities in the heart, therefore, could be a powerful new approach to promote cardiac regeneration and restore myocardial function in adult human heart following injury. To identify mediators of cardiac muscle regeneration, deep RNA sequencing was conducted utilizing isolated ventricular cardiomyocytes from neonatal (on postnatal day 1 & 3 [P1 & P3], both n=4 ) and adult (8-12 weeks, n=7) mice.