Abstract 154: Transcriptomic Analysis Reveals Upregulation of The Pro-Apoptotic, Extracellular Matrix-Degrading Granzyme System in Human Aortic Valve Calcification

Abstract

Background: Calcific Aortic Valve Stenosis (CAVS) is a major valvular disease that leads to myocardial hypertrophy and heart failure. It shares many hallmarks with atherosclerosis, however, many of the specific mechanisms remain to be discovered. We used a DNA-microarray to study the transcriptomic changes in human aortic valve tissue during different stages of stenosis. Methods and Results: RNA was extracted from severely stenotic aortic valves of patients undergoing valve replacement surgery (n=5) and non-sclerotic control valves from patients with aortic insufficiency (n=5). A GeneChip Human Genome U133 Plus 2.0 Array (Affymetrix) was used to study the transcriptomic changes. Among the most upregulated genes were pro-apoptotic Granzymes, which are an integral part of the T-cell-mediated cytotoxic reaction. They have also been shown to be able to degrade the extracellular matrix (ECM). These findings were validated in a larger sample population (n=26) using qRT-PCR. Indeed, significantly increased expression of Granzymes A, B, H, K and M as well as granzyme co-effector Perforin 1 (PRF1) was detected in stenotic valves compared to normal valves. The most significant increase was seen in Granzyme B mRNA levels (7.1-fold; P<0.001) and the gene expression of PRF1 was also markedly upregulated (3.6-fold; P<0.001). Furthermore, the localization of granzymes within the valves and the effect of statin medication on their expression were studied. Conclusions: To our knowledge, this is the first time that the upregulation of the Granzyme system has been studied in human aortic valves. Its involvement indicates an active T-cell-mediated cytotoxic response as well as active degradation of the ECM. This opens up novel possibilities for the treatment and diagnosis of CAVS.