Mechanisms of restenosis following successful coronary angioplasty (PTCA) are knownasvascularsmoothmuscle cells(VSMCs)proliferationandmigration, elastic recoil or vascular wall remodeling. Paclitaxel whose effect on the stabilization of microtubles leads to cell death is highly lipophilic, permitting easy pass through cell membrane, and has a long-term antiproliferative effect. This study was performed to evaluate effect of paclitaxel on VSMCs proliferation and whether locally delivered paclitaxel can prevent stenosis and neointimal formation in rat carotid artery injury model.

Cultured VSMCs were exposed to sequential concentrations of paclitaxel in vitro, and proliferation inhibition was analyzed with ³H-thymidine incorporation. Paclitaxel of a suitable concentration was applied to the endothelium-denuded carotid artery of Fisher 344 inbred rats for 20 minutes. Angiogram and morphometric analysis of carotid artery was performed after 2 weeks.

³H-thymidine incorporation in cultured VSMCs was decreased dose-dependently from the concentration of 0.1 micromol/L (2,454±149cpm/µgram protein) to 100 µmol/L (1,323±69cpm/µgram protein) of paclitaxel by single and 20-minute exposure in the presence of platelet-derived growth factor (p<0.005). In the absence of platelet-derived growth factor, the decrement of ³H-thymidine incorporation was evident above the concentration of 5 µmol/L of paclitaxel. To evaluate in vivo effect, paclitaxel (0.1 or 1 µmol/L) was administered into the endothelium-denuded carotid artery by balloon injury and incubated for 20 minutes. Percent stenoses (32.2±9.8%) of paclitaxel-treated group was less than those (46.3±7.5%) of control group on histologic analysis (p<0.01). Paclitaxel-treated group also had wider lumen on carotid angiogram and less neointimal thickening than control on histologic examination (p<0.005).

Proliferation of VSMCs was effectively inhibited and neointimal formation and luminal stenosis was prevented in rat carotid artery injury model by single, brief and local delivery of low-dose paclitaxel. This strategy could be applied to clinical settings for the prevention of restenosis after PTCA.