Abstract 121: Modulation of Apoptosis, Matrix Degradation and Matrix Synthesis Are the Primary Determinants for Intimal Hyperplasia in Response to Altered Shear

Abstract

Introduction: The quantity of high throughput microarray data leads to unique challenges in understanding its biological significance. We have developed a novel statistical method of clustering dynamics to elucidate for the mapping of gene expression arcs. In the current study, we applied these techniques to the multifactorial process of vein graft intimal hyperplasia, where direct correlation of these patterns was integrated with detailed morphologic data to identify those pathways central to the disease process. Methods: NZW rabbits underwent bilateral carotid vein grafting and unilateral distal branch ligation to create high and low shear environments. Vein grafts were harvested at 2h, 1 d, 7 ds, 28 d, 90 d, and 180 d (n=4 per group), and mRNA expression analyzed using a rabbit Agilent microarray platform. Parallel experiments were used to determine wall morphology, cell proliferation, apoptosis, and matrix content at each time point. Results: Compared to high shear grafts, exposure to a low shear resulted in a 5-fold greater intimal thickness at 180 d. Although 3365 (out of 14,958) genes varied with either time or shear, no single gene was significantly different (at a false discovery rate <0.001) as a function of shear only. To analyze the broad-based modulation of gene expression, a novel clustering technique was used to identify temporal patterns of genes expression. Eight clusters (A through H) were identified, with five of these clusters demonstrating significant variation between high and low shear grafts (Table; A <0.0001, D <0.0001, F < 0.0001, G <0.001, H <0.0001). Ingenuity pathway analysis was used to map gene ontology groups within the clusters to the dominant biologic process observed on histologic analysis. Cell death (cluster D), matrix degradation (cluster G), and matrix synthesis (cluster H), and the associated gene network pathways, were identified being significantly different in the high and low shear grafts (Figure). Conclusions: Using high throughput genomics and detailed morphologic data, we identify cell death, matrix degradation, and matrix synthesis, and the specific pathways associated with these process, as the most critical components in the development of the intimal hyperplastic lesion.