Whole-Blood Transcriptome Unveils Altered Immune Response in Acute Myocardial Infarction Patients With Aortic Valve Sclerosis

Abstract

Background: Aortic valve sclerosis (AVSc) presents similar pathogenetic mechanisms to coronary artery disease and is associated with short- and long-term mortality in patients with coronary artery disease. Evidence of AVSc-specific pathophysiological traits in acute myocardial infarction (AMI) is currently lacking. Thus, we aimed to identify a blood-based transcriptional signature that could differentiate AVSc from no-AVSc patients during AMI.

Methods: Whole-blood transcriptome of AVSc (n=44) and no-AVSc (n=66) patients with AMI was assessed by RNA sequencing on hospital admission. Feature selection, differential expression, and enrichment analyses were performed to identify gene expression patterns discriminating AVSc from no-AVSc and infer functional associations. Multivariable Cox regression analysis was used to estimate the hazard ratios of cardiovascular events in AVSc versus no-AVSc patients.

Results: This cross-sectional study identified a panel of 100 informative genes capable of distinguishing AVSc from no-AVSc patients with 94% accuracy. Further analysis revealed significant mean differences in 143 genes, of which 30 genes withstood correction for age and previous AMI or coronary interventions. Functional inference unveiled a significant association between AVSc and key biological processes, including acute inflammatory responses, type I IFN (interferon) response, platelet activation, and hemostasis. Notably, patients with AMI with AVSc exhibited a significantly higher incidence of adverse cardiovascular events during a 10-year follow-up period, with a full adjusted hazard ratio of 2.4 (95% CI, 1.3-4.5).

Conclusions: Our findings shed light on the molecular mechanisms underlying AVSc and provide potential prognostic insights for patients with AMI with AVSc. During AMI, patients with AVSc showed increased type I IFN (interferon) response and earlier adverse cardiovascular outcomes. Novel pharmacological therapies aiming at limiting type I IFN response during or immediately after AMI might improve poor cardiovascular outcomes of patients with AMI with AVSc.

Keywords: acute myocardial infarction; aortic valve sclerosis; cardiovascular adverse events; immune response; inflammation.

Figure 1.

Gene expression dataset and feature selection. A, Pie chart shows the relative abundance of the different RNA biotypes of the entire set of expressed genes. B, Scatterplot of the 2 coordinates (X1 and X2) obtained from the multidimensional scaling performed on the 100 genes identified by applying feature selection based on genetic algorithm (ie, GARS [Genetic Algorithm for the Identification of Robust Subsets] R/Bioconductor package). Colors refer to aortic valve sclerosis (AVSc) and no-AVSc patients (red and blue, respectively). LNC indicates long noncoding; NOVEL, putative novel genes; PC, protein coding; PSE, pseudogenes; and SNC, small noncoding.

Figure 2.

Volcano plots and Venn diagram. Scatterplot of log2fold change (FC) vs the significance (x and y axis, respectively) for the comparison between aortic valve sclerosis (AVSc) and no-AVSc patients found from model (Mod)Ø (A), Mod1 (B), and Mod2 (C). Plot colors refers to differentially expressed (DE) genes (red), genes with adj. P<0.05 but |log2FC| <0.5 (blue), genes with |log2FC|>0.5 but adj. P>0.05 (green); nonsignificant DE genes (gray). Vertical and horizontal dashed lines represent log2FC and adj. P value thresholds, respectively. D, The intersection of DE genes (adj. P<0.05 and |log2FC| >0.5) obtained from the different statistical models. NS indicates not significant.

Figure 3.

Functional enrichment network. The enrichment network shows the gene ontology (GO)-biological processes (BP) gene sets (nodes) that are significantly associated (false discovery rate <0.05) either with aortic valve sclerosis (AVSc) and no-AVSc patients. The node color refers to the association with the phenotype (AVSc, red and no-AVSc, blue); node gradient color is proportional to the gene set normalized enrichment score (NES), from lower (light) to higher (dark); node size is proportional to the gene set size. Labels of overview gene set terms grouping nodes with similar meaning are shown. Edges connect related GO-BPs. Edge thickness is proportional to the similarity between 2 GO-BPs, for a cutoff=0.25 of the combined Jaccard plus Overlap coefficient. ER indicates endoplasmic reticulum; and SRP, signal recognition particle.

Figure 4.

Cell-type enrichment network. The network shows the significant gene sets related to immune cell types (false discovery rate <0.05) that are enriched in the comparison between aortic valve sclerosis (AVSc) and no-AVSc patients. The node color refers to the association with the phenotype (AVSc, red and no-AVSc, blue); node gradient color is proportional to the cell-set normalized enrichment score (NES), from lower (light) to higher (dark); node size is proportional to the cell-set size. Edges connect related cell type. Edge thickness is proportional to the similarity between 2 cell-type, for a cutoff=0.25 of the combined Jaccard plus Overlap coefficient. NK indicates natural killer.

Figure 5.

Adverse cardiovascular events in patients with acute myocardial infarction (AMI). A, Kaplan-Meier curves show the event’s probability of cardiovascular events in patients with AMI with aortic valve sclerosis (AVSc) vs patients with AMI without AVSc. B, Cox regression analyses show the hazard ratios (HRs) adjusted for AMI type only (ModØ), for AMI type and age (Mod1), and for AMI type, age plus previous cardiovascular events (Mod2).

Figure 6.

Box plots of relevant type I IFN (interferon) response genes. Box plots show the differences over the time-to-cardiovascular event (<5 and >5 years; x axis) of the normalized expression values (y axis) of the type I IFN response genes in aortic valve sclerosis (AVSc) and no-AVSc patients assessed on blood sample collected at hospital presentation. The 8 genes shown (A–H) were selected as they presented the highest combined-ranked score (cs, that is, log2-fold-change [FC]×−log10[P value]) among the type I IFN response genes as resulted by the differential expression analysis of AVSc vs no-AVSC in the full adjusted statistical model (Mod2). Number of patients for time-to-cardiovascular event comparisons were for <5 years: AVSc=25, no-AVSc=16; and for >5 years, AVSc=10, no-AVSc=38. Box (red and blue) and dots (pink and light blue) colors refer to AVSc and no-AVSc patients, respectively. Stars mark significant differences for post hoc tests with P values: **<0.01; *<0.05; •<0.1; ns indicates nonsignificant difference. IFI27 indicates interferon alpha-inducible protein 27; IFIT1, interferon-induced protein with tetratricopeptide repeats 1; IFIT3, interferon-induced protein with tetratricopeptide repeats 3; ISG15, ISG15 ubiquitin-like modifier; OAS3, 2’-5’-oligoadenylate synthetase 3; OASL, 2’-5’-oligoadenylate synthetase-like; RSAD2, radical S-adenosyl methionine domain containing 2; and XAF1, XIAP-associated factor 1.