Abstract
Hypoplastic left heart syndrome (HLHS) is characterized by underdevelopment of the left ventricle (LV) and increased biomechanical stress on the right ventricle (RV) from single ventricle physiology. Despite the clinical significance, the signaling pathways active during RV remodeling and disease progression are not known. To address this, we examined differential changes in expression of genes associated with transforming growth factor-β (TGF-β)/bone morphogenetic protein (BMP) signaling in RV tissue isolated from HLHS patients relative to RV and LV tissue from control subjects.
Quantitative real-time polymerase chain reaction was used to detect changes in expression of 84 genes involved in TGF-β/BMP-mediated cardiac development, cell growth, and differentiation in RV tissue collected from 6 neonates with HLHS undergoing stage 1 Norwood procedure (age, 1-7 days; mean, 4 days) and RV and LV tissue obtained from 5 infants with noncardiac pathology (age range, 1-135 days: mean, 85 days) that served as controls. Analysis of gene expression profiles between control-LV and control-RV revealed significant depression of TGF-β/BMP signaling in RV compared with LV. Of the 84 genes analyzed, 38 were differentially expressed between HLHS-RV and control-RV, whereas only 22 compared with control-LV. Significant changes were observed in: tissue remodeling genes including
Activin receptor type IIA (
ACVR2A) (+2.13) and
Activin receptor-like kinase 1 (
ACVRL1) (+2.22); and cell survival, growth, and differentiation genes including
CDC25A (+2.18),
p21 (−3.64),
p15 (+2.15),
BMP5 (+4.58),
BMP3 (+2.16),
GDF3 (+8.59),
NODAL (+2.32), and
BMP binding endothelial regulator (BMPER) (+4.58). The most significant changes common to HLHS-RV versus control-RV and control-LV sample groups is observed for
Anti müllerian hormone receptor 2 (
AMHR2) (+18.79 control-RV, +3.38 control-LV), and the BMP antagonist
Inhibin alpha (
INHA) (+11.47 control-RV, +5.73 control-LV).
Although this descriptive study does not allow cause-effect inferences, our results suggest changes in cardiac development pathways and upregulation of genes associated with cell growth and differentiation in the neonatal RV of children with HLHS. These molecular profiles are more closely related to those observed in the normal LV rather than normal RV at similar maturational age. This work provides the basis for future mechanistic studies to elucidate the molecular mechanisms regulating RV remodeling in HLHS.
