Abstract 9528: Apical Resection in Newborn Pig Hearts Extends the Regenerative Window of Cardiomyocyte

Abstract

Background: The neonatal porcine heart possesses proliferative cardiomyocyte capacity to recover heart function and structure after an acute myocardial injury during two days of birth. In this study, we have extended the myocardial regenerative window to postnatal day 28 (P28) by a double injury pig model (AR P1 MI P28 ), which performed apical resection at P1 (AR P1 ) followed by LAD ligation at P28 (MI P28 ). However, the molecular mechanism of regenerative window extension is unknown. Methods: The AR P1 MI P28 hearts showed no visible sign of myocardial damage or malfunction 4 weeks after LAD ligation. The nuclear RNA contents were isolated from hearts that received none, singe, and double injury hearts. They performed single nuclei RNA-seq to characterize the gene-expression profile of the AR P1 MI P28 in cardiomyocytes. Results: Gene-expression profiles revealed that regenerating AR P1 MI P28 hearts contained different subpopulations of cardiomyocytes early after 2 nd injury. Louvain clustering identified the six cardiomyocyte clusters (CM1-CM6). The CM6, CM3, and CM2 clusters have mainly comprised fetal (92.4%), CTL-P1 (95.7%), and CTL-P56 (96.2%) cardiomyocytes. In contrast, the CM1 cluster has comprised heterogeneous cardiomyocyte groups from all other animal groups, including less than 1% of fetal and CTL-P1 cardiomyocytes. The CM5 and CM4 clusters have mainly comprised AR P1 MI P28 -P35 (double injury hearts harvested at P35) cardiomyocytes, 97.8% and 68.6%, respectively. Sparse modeling analysis revealed that AR and MI injury, both alone and in combination, appeared to extend the regenerative capacity of cardiomyocytes and perturb cardiomyocyte maturation. Conclusion: We have demonstrated that the unique CM5 cluster appeared only after the 2 nd injury of AR P1 MI P28 -P35 hearts. This cell cluster was characterized by a highly expressed isoenzyme of the glycolytic enzyme pyruvate kinase M2 (Pkm2) and skeletal muscle filamentous gene Nebulin. Transient expression of the CM5 cluster induces by the AR P1 might contribute to the sustained remuscularization and myocardial function recovery following an acute MI in large mammals.