Abstract 282: Differential Effects of Thrombospondins on Angiogenesis Gene Expression: Contribution of Statins

Abstract

Objectives: Angiogenesis is important for vascular repair and of interest for treating peripheral arterial disease (PAD). Thrombospondins (TSP) are matricellular proteins involved in PAD. TSP-1 is the first endogenous angiogenesis inhibitor found. TSP-2, which is structurally similar, is also anti-angiogenic. TSP-5 (Cartilage Oligomeric Matrix Protein) differs structurally and may not be anti-angiogenic. Statins have pleiotropic vascular effects that impact TSPs. We studied the effects of TSPs and statin on endothelial cells (ECs). Hypothesis: TSP-1 and -2 induce anti-angiogenic genes, and inhibit EC tube formation while TSP-5 or statin induce pro-angiogenic genes and stimulate EC tube formation. Methods: ECs were exposed to serum free medium (SFM), TSP-1, -2, or -5 (20μg/mL) for 6 hours with or without 24 hour statin (0.5μM) pre-treatment. qrtPCR was done on 94 angiogenesis related genes. Analysis was by t-test and ANOVA, p < 0.05 was significant. Canonical pathways were examined with IPA software. EC tube formation and disruption were assessed with Matrigel and SFM, TSP-1, -2, or -5 (20μg/mL) treatment with or without statin. Results: TSP-1 and -2 downregulated pro-angiogenic genes while TSP-5 both up-regulated and downregulated pro-angiogenic genes (Fig. 1). All TSPs were affected by statin. TSP-1, and -2 decreased EC tube formation (47% and 28% respectively, p<0.05) and disrupted EC tubes (36% and 26% respectively, p<0.05). Addition of statin trends towards attentuation of TSP tube disruption. TSP-5 had no effect on EC tubes formation. Conclusions: TSP-1, -2, and -5 impact EC angiogenesis pathways. TSP-1 and -2 downregulated pro-angiogenic genes in similar pathways. TSP-5 upregulated pro-angiogenic genes, and statin augmented this effect. TSP-1 and -2 are anti-angiogenic while TSP-5 is not in vitro . The role of statin in EC tube formation is unclear but statin does impact TSP regulation of angiogenesis gene expression and thus further studies are needed.