Abstract 340: Recombinant Soluble Apyrase Inhibits Vascular Smooth Muscle Cell Migration

Abstract

Background: Purinergic receptor activation by extracellular nucleotides is involved in thrombosis and neointimal hyperplasia that accompany atherosclerosis and postangioplasty restenosis. Human apyrases [ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDases)] are membrane bound enzymes that hydrolyze extracellular nucleotides, thereby inhibiting purinergic receptor activation. CD39, the first identified human apyrase, is constitutively expressed on endothelial cell (EC) and vascular smooth muscle cell (VSMC) surfaces. APT102, a recombinant soluble form of CD39L3, has been shown to reduce platelet activation through its ADPase activity, but its effects on VSMC and EC function are yet to be established. We tested the hypothesis that APT102 will inhibit migration of VSMCs and ECs. Methods: We studied cell migration using a modified Boyden chamber assay in which 5x10 4 cells suspended in 0.2% FBS/DMEMF12 were added to the upper chamber of transwells separated from the lower chamber medium by a microporous membrane through which VSMCs and ECs can migrate. APT102 (100 nM) or vehicle control was added to the upper chamber; lower chamber contained 2.5% FBS/DMEMF12 and either ATP (10 μM) or vehicle control. Transwells were incubated at 37 0 C for 6 h, after which cells that migrated through pores and adhered to the lower chamber side of the membrane were fixed, stained and counted. Results: ATP (10μM) significantly enhanced migration of both VSMCs and ECs. APT102 significantly inhibited VSMC migration and completely abrogated the pro-migratory effect of ATP. In contrast, APT102 had no inhibitory effect on EC migration, either spontaneous or ATP-enhanced. Conclusion: APT102 inhibits VSMC but not EC migration. These results suggest that pharmacological targeting of extracellular nucleotides may provide a safe and effective therapeutic strategy to inhibit neointimal hyperplasia and restenosis after angioplasty, without delaying endothelial cell recovery, which is a significant limitation of drug-eluting stents. Further studies are needed to clarify the mechanism(s) underlying the differential effect of extracellular nucleotide degradation by APT102 on VSMC and EC migration.