Altered expression of a limited number of genes contributes to cardiac decompensation during chronic ventricular tachypacing in dogs

Abstract

Our aim was to determine the changes in the gene expression profile occurring during the transition from compensated dysfunction (CD) to decompensated heart failure (HF) in pacing-induced dilated cardiomyopathy. Twelve chronically instrumented dogs underwent left ventricular pacing at 210 beats/min for 3 wk and at 240 beats thereafter, and four normal dogs were used as control. The transition from CD to HF occurred between the 3rd and 4th wk of pacing, with end-stage HF at 28 ± 1 days. RNA was extracted from left ventricular tissue at control and 3 and 4 wk of pacing ( n = 4) and tested with the Affymetrix Canine Array. We found 509 genes differentially expressed in CD vs. control ( P ≤ 0.05, fold change ≥±2), with 362 increasing and 147 decreasing; 526 genes were differentially expressed in HF vs. control ( P ≤ 0.05; fold change ≥±2), with 439 increasing and 87 decreasing. To better understand the transition, we compared gene alterations at 3 vs. 4 wk pacing and found that only 30 genes differed ( P ≤ 0.05; fold change of ±2). We conclude that a number of processes including normalization of gene regulation during decompensation, appearance of new upregulated genes and maintenance of gene expression all contribute to the transition to overt heart failure with an unexpectedly small number of genes differentially regulated.