RESUMO
BACKGROUND: The antineoplastic compound paclitaxel (Taxol) causes an increased assembly of extraordinarily stable microtubules. The present study was designed to characterize the effects of paclitaxel on proliferation and migration of human arterial smooth muscle cells (haSMCs) in vitro and on neointima formation in an in vivo experimental rabbit model. METHODS AND RESULTS: Both monocultures of haSMCs and cocultures with human arterial endothelial cells (haECs) were used. Cell growth after 4, 8, and 14 days was determined in the absence or presence of platelet-derived growth factor-AB (PDGF-AB), basic fibroblast growth factor (bFGF), or thrombin. Nonstop paclitaxel exposure, as well as single-dose applications of paclitaxel for 24 hours or even 20 minutes (0.1 to 10.0 micromol/L), caused a complete and prolonged inhibition of haSMC growth up to day 14, with an IC50 of 2.0 nmol/L. Mitogens or cocultures with stimulating haECs did not significantly attenuate paclitaxel-induced effects. Immunohistochemistry showed characteristic cytoskeletal changes predominantly in the microtubule network. Additionally, in 20 male New Zealand White rabbits, intimal plaques were produced by electrical stimulation. In 10 animals, paclitaxel was locally applied by use of microporous balloons. Histologically, the intima wall area, wall thickness, and degree of stenosis were reduced significantly in paclitaxel-treated animals compared with controls. CONCLUSIONS: Our data show that paclitaxel inhibits haSMC proliferation and migration in a dose-dependent manner in monocultures and cocultures even in the presence of mitogens. Furthermore, paclitaxel prevents neointima formation in rabbits after balloon angioplasty. The long-lasting effect after just several minutes' exposure time makes this lipophilic substance a promising candidate for local antiproliferative therapy of restenosis.
