Volume Overload Initiates an Immune Response in the Right Ventricle at the Neonatal Stage

Abstract

Background: Pulmonary regurgitation caused by the correction or palliation of pediatric tetralogy of Fallot (TOF) leads to chronic right ventricular (RV) volume overload (VO), which induces adolescent RV dysfunction. A better understanding of the molecular mechanism by which VO initiates neonatal RV remodeling may bring new insights into the post-surgical management of pediatric TOF.Methods and Results: We created a fistula between the abdominal aorta and inferior vena cava on postnatal day 1 (P1) using a rat model to induce neonatal VO. Echocardiography revealed that the velocity and velocity- time-integral of the pulmonary artery (PA) were significantly elevated, and hematoxylin and eosin (H&E) staining showed that the diameter of the RV significantly increased. RNA-seq analysis of the RV on P7 indicated that the top 10 enriched Gene Ontology (GO) terms and the top 20 enriched terms in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were associated with immune responses. Flow-cytometric analysis demonstrated that the number of CD4+and CD8+ immune cells were significantly augmented in the VO group compared with the sham group.Conclusions: A neonatal cardiac VO rat model on P1 was successfully created, providing a platform for studying the molecular biology of neonatal RV under the influence of VO. VO - induces an immune response at the neonatal stage (from P1 to P7), suggesting that immune responses may be an initiating factor for neonatal RV remodeling under the influence of VO and that immunosuppressants may be used to prevent pediatric RV remodeling caused by VO.

Accelerated Growth, Differentiation, and Ploidy with Reduced Proliferation of Right Ventricular Cardiomyocytes in Children with Congenital Heart Defect Tetralogy of Fallot

“…In the myocardium of laboratory animals (mice and rats), the maximum proliferative activity of CMCs has been detected in the first week of postnatal development. It decreases later, but the ploidy of myocytes increases due to the formation of multinucleated CMCs [ 19 , 30 , 31 , 34 , 44 , 47 , 49 ]. The peak of DNA synthesis (up to 10% of labeled CMCs nuclei) and the maximum number of Ki67-positive CMCs nuclei are noted in the mouse myocardium on the fourth day of postnatal development, which later decreases to 0% [ 34 , 44 , 49 ].…”

“…Other mechanisms are known to control the arrest of CMCs in the G 0 phase of the cell cycle, such as the induction of CDKs inhibitors represented by members of the INK4 family (p15, p16, p18, p19 and CIP/KIP family (p21, p27, p53, and p57) [ 17 , 18 , 19 , 21 , 22 , 23 , 24 ]. It has also been shown that the Notch signaling pathway, due to its action on cyclin D, initiates the entry into the cycle of resting embryonic stem cells and neonatal ventricular CMCs [ 125 ].…”

“…It is known that the proliferative activity of RV CMCs in patients with TF is associated with SaO 2 parameters [ 16 ]. On the other hand, in a number of experimental studies it has been shown that pressure and volume RV overload, induced in the first days of postnatal development, similar to that arising in TF, leads to the activation of the expression of proliferative markers in CMCs, as well as to increased angiogenesis and, later, myocardial fibrosis [ 17 , 18 , 19 ]. One of the unresolved questions is whether the activation of the CMCs proliferation in the immature myocardium of children with TF can be caused and by what factors.…”

“…During this period, the activity of several cyclins and cyclin-dependent kinases (CDK), their inhibitors, and transcription factors, both positively and negatively regulating the cell cycle, change [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. Significant morphological changes occur in the myocardium, characterized by a decrease in the proliferative activity of CMCs, an increase in their ploidy, size, and differentiation [ 19 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. CMCs go through the last cell cycle without completing cytokinesis, which leads to an increase in the number of binucleated terminally differentiated CMCs at the G 0 [ 28 , 29 , 34 , 35 , 36 , 52 , 53 , 54 ].…”

Molecular Changes in Prepubertal Left Ventricular Development Under Experimental Volume Overload

“…In adult animals, ACF not only induces RV VO but also produces LV VO ( 24 , 25 ). In past studies, we demonstrated that ACF induces RV VO at neonatal and prepubertal animals ( 13 , 18 , 20 , 26 ), and VO induces different responses among neonatal, prepubertal, and adult RVs ( 13 , 26 , 27 ), highlighting the importance of developmental stage-specific analysis of the effect of VO on RV remodeling. How ACF induces prepubertal LV VO is unknown.…”