Transcriptomic analysis of patients with tetralogy of Fallot reveals the effect of chronic hypoxia on myocardial gene expression

Objectives

In cyanotic patients undergoing repair of heart defects, chronic hypoxia is thought to lead to greater susceptibility to ischemia and reoxygenation injury. We sought to find an explanation to such a hypothesis by investigating the cardiac gene expression in patients with tetralogy of Fallot undergoing cardiac surgery.

Methods

The myocardial gene profile was investigated in right ventricular biopsy specimens obtained from 20 patients with a diagnosis of cyanotic (n = 11) or acyanotic (n = 9) tetralogy of Fallot undergoing surgical repair. Oligonucleotide microarray analyses were performed on the samples, and the array results were validated with Western blotting and enzyme-linked immunosorbent assay.

Results

Data revealed 795 differentially expressed genes in cyanotic versus acyanotic hearts, with 198 upregulated and 597 downregulated. Growth/morphogenesis, remodeling, and apoptosis emerged as dominant functional themes for the upregulated genes and included the apoptotic gene TRAIL (tumor necrosis factor–related apoptosis-inducing ligand), the remodeling factor OPN (osteopontin), and the mitochondrial function gene COX11 (cytochrome-c oxidase 11). In contrast, transcription, mitogen-activated protein kinase signaling, and contractile machinery were the dominant functional classes for the downregulated genes, which included the calcium-handling gene NCX1 (sodium-calcium exchanger). Protein levels of COX11, NCX1, OPN, and LYZ (lysozyme) in the myocardium followed the same pattern obtained by means of transcriptomics. The TRAIL level did not change in myocardium but increased in circulating blood of cyanotic patients, suggesting the myocardium as a possible source. Additionally, our data showed increased protein expression of apoptosis markers in cyanotic myocardium.

Conclusions

Chronic hypoxia in cyanotic children with tetralogy of Fallot induced the expression of genes associated with apoptosis and remodeling and reduced the expression of genes associated with myocardium contractility and function.

CTSNet classification: 20, 29

Abbreviations and Acronyms: BAX, Bcl-2-associated X protein, CPB, cardiopulmonary bypass, ELISA, enzyme-linked immunosorbent assay, ERK, extracellular signal-regulated kinase, FDR, false discovery rate, MAPK, mitogen-activated protein kinase, RVH, right ventricular hypertrophy, TOF, tetralogy of Fallot, VEGF, vascular endothelial growth factor