SHORT-TERM EXPOSURE TO THAPSIGARGIN INHIBITS NEOINTIMA FORMATION IN HUMAN SAPHENOUS-VEIN

Vascular smooth muscle cell (VSMC) migration and proliferation are inv olved in the intimal thickening responsible for late vein graft failur e. In addition to growth and chemotactic factors, VSMCs require expres sion of matrix-degrading enzymes, eg, metalloproteinases (MMP), to rel ieve the antiproliferative and antimigratory constraints of the extrac ellular matrix. Thapsigargin irreversibly inhibits Ca2+-ATPase, elicit ing an increase in intracellular Ca2+ and depletion of the intracellul ar calcium pools that are thought to be involved in the control of VSM C migration, VSMC proliferation, and MMP activity. We therefore studie d the effect of thapsigargin on VSMC migration, VSMC proliferation, an d MMP expression in human saphenous vein organ cultures. Vein segments were cultured for 14 days, and VSMC proliferation and migration were determined by autoradiography. Cell death was assessed using in situ e nd-labeling and lactate dehydrogenase release. Using Western blotting, we examined MMP-2 and MMP-9 and tissue inhibitor of metalloproteinase s (TIMP)-1 and TIMP-2 expression. Exposure to thapsigargin at 10 nmol/ L for 60 minutes before culture significantly inhibited neointimal thi ckening (60%, P<.05), intimal and medial VSMC proliferation (32%, P<.0 5 and 37%, P<.05, respectively), and VSMC migration (36%, P<.05). Thap sigargin at 10 nmol/L did not significantly increase cell death or MMP -2, MMP-9, TIMP-1, and TIMP-2 expression. These results suggest that b lockade of Ca2+-ATPase by thapsigargin inhibits VSMC migration and pro liferation involved in neointimal formation without affecting MMP-2 an d MMP-9 expression. Because short-term exposure to thapsigargin was su fficient to inhibit neointima formation, this drug may prove useful in the treatment of intimal thickening after arterial bypass graft surge ry.