Introduction:
Despite current standard of care, heart failure (HF) remains a leading cause of death and indication for transplant in the single ventricle congenital heart disease (SV) population. However, little is known regarding the molecular mechanisms underlying remodeling and eventual HF in SV patients. The purpose of this study was to characterize the transcriptional profile of SV myocardium in both failing (SVHF) and non-failing (SVNF) SV patients compared to biventricular NF controls (BVNF). Furthermore, we conducted high resolution respirometry to assess mitochondrial function in each of these populations.
Methods:
Library prep was performed using the TruSeq Ribo Zero rRNA depletion kit, and 2x150 total RNAseq (Illumina HiSEQ 4000) was performed on age-matched explanted RV myocardium from BVNF (n=4 biventricular donors), SVNF (n=8 SV primary transplants, normal function), and SVHF (n=9 SV systolic HF transplants). Samples were aligned to hg19 and were normalized and annotated using the edgeR pipeline. Significant changes in gene expression were calculated using an FDR adjusted p-value (q<0.1; p<0.025). Respiration of myocardial mitochondria was measured using a stepwise protocol to evaluate respiratory capacity in an Oroboros Oxygraph system; n=6 SVHF, n=6 SVNF, n=18 BVNF.
Results:
RNAseq identified 1,007 differentially expressed genes in SVNF and 2,109 in SVHF myocardium relative to BVNF controls. Transcriptome pathway analysis demonstrated multiple pathways that are similarly dysregulated in SVNF and SVHF, while pathways involved in mitochondrial metabolism and function were significantly dysregulated specifically in the SVHF population. Moreover, mitochondrial oxygen flux was significantly decreased, particularly through complexes I and II, in SVHF relative to BVNF controls.
Conclusions:
Our results provide new insights into SVHF by identifying unique gene expression changes, including those related to metabolism, and impaired mitochondrial function. Together these data suggest dysregulated metabolic gene expression and mitochondrial dysfunction are phenotypes associated with the failing single ventricle and may serve as potential therapeutic targets for the treatment or prevention of HF in the SV population.
Expression profiling reveals differences in metabolic gene expression between exercise-induced cardiac effects and maladaptive cardiac hypertrophy