Gene expression differences during the heterogeneous progression of peripheral atherosclerosis in familial hypercholesterolemic swine

Abstract

Background: The heterogeneous progression of atherosclerotic disease in the peripheral arteries is currently not well understood. In humans, artery specific disease progression is partly attributed to the local hemodynamic environments. However, despite similar hemodynamic environments, porcine brachial arteries are protected while femoral arteries are highly susceptible to advanced lesion formation. The aim of this investigation was to determine whether artery specific gene expression patterns contribute to the uneven distribution of peripheral arterial disease (PAD) in Rapacz Familial-Hypercholesterolemic (FHC) swine.

Results: Histological results confirmed rapid atherosclerotic disease progression in femoral but not brachial arteries. A total of 18,922 probe sets had sufficient signal abundance. A main effect for age and artery was observed for 1784 and 1256 probe sets, respectively. A significant age x artery interaction was found for 184 probe sets. Furthermore, comparison between arteries found a decrease from 714 to 370 differentially expressed transcripts from nine months to two years of age. Gene ontology analysis of the 56 genes with a main effect for artery and an age x artery interaction identified vascular smooth muscle contraction as enhanced biological signaling pathway.

Conclusion: This is the first investigation to report that the total number of differential genes decreases with diverging atherosclerotic disease pattern between porcine brachial and femoral arteries.

Figure 1

Differential Sudan IV staining between brachial and femoral arteries from 1 and 2 year old Rapacz FHC swine.

Figure 2

Representative VerhoeffVanGiesson (VVG) stains at 100x (A and B) and 40x (C and D) from brachial and femoral arteries of nine month (A, B) and two year old (C, D) Rapacz FHC swine.

Figure 3

Microarray results overview. The Venn diagrams illustrate the results of the 2 x 2 ANOVA (A) and the contrast comparison between arteries within age group (B). The volcano plots illustrate the overall microarray data for differential gene expression between brachial and femoral arteries in the nine month (C) and two (D) year old Rapacz FHC swine. The points indicate the log2(fold-change) (on the x-axis) and the –log10(FDR adj. P value) (on the y-axis) for each probe set with sufficient signal. The horizontal line (y = 1.3) specifies the FDR cut-off for significance (FDR = 0.05).

Figure 4

Heatmap displaying the 56 probe sets with a significant effect for artery and age x artery interaction. The red and green color of the cells indicates relative transcript abundance below and above the average gene expression for that particular probe set, respectively. The columns represent the 22 samples while the rows correspond to the 56 gene IDs. The dendograms on the left and top use two-way hierarchical clustering to cluster samples and probe sets, respectively, according to similarity in change in relative transcript abundance. Specifically, a total of four and 13 distinct clusters were identified for the samples (denoted “1”,”2”,”3”, and “4”) and probe sets (denoted “A” through “M”). The description under each column denotes the animal ID from Table  2 and “B” for brachial or “F” for femoral artery.