Abstract 82: Wnt11 Regulates Chamber Specific Neonatal Cardiomyocyte Proliferation During Perinatal Circulatory Transition

Abstract

Background: Fetal to neonatal transition of heart involves major changes in cardiomyocytes (CMC) including proliferative capacity. However, the chamber specific CMC proliferation programs of remain poorly understood. Elucidating the mechanisms involved is critical to develop chamber specific therapies for newborn infants with single ventricle physiology and other congenital heart defects (CHDs). Methods: Transcriptomes of mouse left ventricle (LV) and right ventricle (RV) were analyzed by RNA-seq at postnatal days 0 (P0), P3 and P7. R package and Ingenuity suite were used for weighted gene co-expression network analysis (WGCNA) and gene ontology studies. Mechanistic analysis was conducted using gain and loss of function approaches. Results: Mouse neonatal cardiac transcriptome was mostly affected by developmental stage. WGCNA revealed 5 LV and 8 RV modules that were significantly correlated with maturation stage and highly preserved between both ventricles at P0 and P7. In contrast, P3 specific gene modules exhibited the largest chamber specific variations in cell signaling, involving proliferation in LV and Wnt signaling molecules, including Wnt11, in RV. Importantly, Wnt11 expression significantly decreased in cyanotic CHDs phenotypes and correlated with O2 saturation levels in hypoxemic infants with Tetralogy of Fallot (TOF). Notably, Perinatal hypoxia treatment in mice suppressed Wnt11 expression, induced CMC proliferation, downregulated Rb1 expression and enhanced Rb1 phosphorylation more robustly in RV vs. LV. Remarkably, Wnt11 inactivation was sufficient to induce myocyte proliferation in perinatal mouse heart and reduced Rb1 expression and phosphorylation in primary neonatal CMC. Importantly, downregulated Wnt11 in hypoxemic TOF infantile heart was also associated with Rb1 suppression and inversely correlated with proliferation marker Plk1 in human. Conclusion: Using integrated systems genomic and functional biology analyses of perinatal cardiac transcriptome, we revealed a previously uncharacterized function for Wnt11 in chamber specific growth and cyanotic CHD. Reduction of Wnt11 expression by hypoxia plays a critical role in neonatal CMC proliferation via modulating Rb1 expression and activity.