Cardiomyocyte cell cycling, maturation, and growth by multinucleation in postnatal swine. (September 2020)

• Record Type: Journal Article
• Authors: Velayutham, Nivedhitha; Alfieri, Christina M.; Agnew, Emma J.; Riggs, Kyle W.; Baker, R. Scott; Ponny, Sithara Raju; Zafar, Farhan; Yutzey, Katherine E.
• Is Part Of: Journal of molecular and cellular cardiology. Volume 146(2020)
• Page Start: 95
• Page End: 108
• Publication Date: 2020-09
• Subjects: Pig heart development -- Large mammal cardiac model -- Cardiomyocyte cell cycle -- Postnatal cardiac maturation -- Neonatal heart regeneration; Cardiology -- Periodicals; Heart Diseases -- Periodicals; Molecular Biology -- Periodicals; Cardiologie -- Périodiques; Cardiology; Electronic journals; Periodicals; 616.12
• DOI: 10.1016/j.yjmcc.2020.07.004
• Languages: English
• ISSNs: 0022-2828

Abstract

Abstract: Background: Rodent cardiomyocytes (CM) undergo mitotic arrest and decline of mononucleated-diploid population post-birth, which are implicated in neonatal loss of heart regenerative potential. However, the dynamics of postnatal CM maturation are largely unknown in swine, despite a similar neonatal cardiac regenerative capacity as rodents. Here, we provide a comprehensive analysis of postnatal cardiac maturation in swine, including CM cell cycling, multinucleation and hypertrophic growth, as well as non-CM cardiac factors such as extracellular matrix (ECM), immune cells, capillaries, and neurons. Our study reveals discordance in postnatal pig heart maturational events compared to rodents. Methods and results: Left-ventricular myocardium from White Yorkshire-Landrace pigs at postnatal day (P)0 to 6 months (6mo) was analyzed. Mature cardiac sarcomeric characteristics, such as fetal TNNI1 repression and Cx43 co-localization to cell junctions, were not evident until P30 in pigs. In CMs, appreciable binucleation is observed by P7, with extensive multinucleation (4–16 nuclei per CM) beyond P15. Individual CM nuclei remain predominantly diploid at all ages. CM mononucleation at ~50% incidence is observed at P7–P15, and CM mitotic activity is measurable up to 2mo. CM cross-sectional area does not increase until 2mo–6mo in pigs, though longitudinal CM growth proportional to multinucleation occurs after P15. RNAseq analysis of neonatal pig left ventricles showed increased expression of ECM maturation, immune signaling, neuronal remodeling, and reactive oxygen species response genes, highlighting significance of the non-CM milieu in postnatal mammalian heart maturation. Conclusions: CM maturational events such as decline of mononucleation and cell cycle arrest occur over a 2-month postnatal period in pigs, despite reported loss of heart regenerative potential by P3. Moreover, CMs grow primarily by multinucleation and longitudinal hypertrophy in older pig CMs, distinct from mice and humans. These differences are important to consider for preclinical testing of cardiovascular therapies using swine, and may offer opportunities to study aspects of heart regeneration unavailable in other models. Graphical abstract: Unlabelled Image Highlights: Pig cardiomyocyte (CM) maturation and mitotic arrest occur over 2–6 months. Nearly 50% mononucleated-diploid CMs persist at 2 weeks after birth in swine. Adolescent pig CMs exhibit progressive multinucleation and longitudinal growth. Pig CM terminal maturation does not coincide with reported P3 regenerative loss. RNAseq suggests critical role for non-CM factors in postnatal pig heart maturation.