Background The relation among the coagulation cascade, its individual proteins, and the response to vascular injury is largely undefined. We have evaluated the effect of four probes that block specific levels of coagulation cascade on neointimal hyperplasia in the atherosclerotic rabbit arterial injury model.

Methods and Results Focal femoral atherosclerosis was induced by air-desiccation injury and hypercholesterolemic diet in 48 New Zealand White rabbits, followed by balloon angioplasty. Active-site inactivated factor VII_a (DEGR-VII_a), which blocks the binding of factor VII_a to tissue factor, was administered (n=12 arteries) by intravenous bolus (1 mg/kg) at the time of balloon angioplasty and followed by infusion of 50 μg · kg⁻¹ · h⁻¹ for 3 days; for the control (n=13 arteries), 150 U heparin was injected as bolus and followed by infusion of saline at 50 μL · kg⁻¹ · min⁻¹. Recombinant tissue factor pathway inhibitor (TFPI), which binds factor X_a and inhibits the tissue factor–factor VII_a complex and factor X_a, was given as a 1 mg/kg bolus followed by 15 μg · kg⁻¹ · min⁻¹ infusion for 3 days (n=17 arteries). Recombinant tick anticoagulant peptide (TAP; n=15 arteries) and hirudin (n=14 arteries), which block factor X_a and thrombin, respectively, were administered as a 1 mg/kg bolus followed by 5 μg · kg⁻¹ · min⁻¹ infusion for 3 days. These three groups had their own controls (n=14 arteries). There were no differences among treatment groups in preangioplasty and postangioplasty minimal luminal diameter (MLD) by angiography. The mean MLD 21 days after balloon angioplasty was significantly different between control and DEGR-VII_a–treated groups (0.74±0.25 and 1.24±0.27 mm, respectively; P=.0001) and between the TFPI-treated group and others (0.88±0.21 mm for control, 0.97±0.22 mm for hirudin-treated, 0.98±0.14 mm for TAP-treated, and 1.32±0.21 mm for TFPI-treated arteries; P=.0001 by ANOVA). By quantitative histological analysis, the ratio of neointimal cross-sectional area compared with the area of internal elastic lamina in the DEGR-VII_a–treated group was significantly less than control (0.48±0.12 versus 0.67±0.12, P=.0001), and the ratio of neointimal cross-sectional area to the area demarcated by the internal elastic lamina of the TFPI-treated group was significantly reduced compared with the other groups (0.46±0.20 for TFPI-treated, 0.67±0.15 for hirudin-treated, 0.61±0.15 for TAP-treated, and 0.64±0.13 for control groups; P=.003).

Conclusions Treatment with DEGR-VII_a or TFPI for 3 days in this rabbit atherosclerotic injury model reduced angiographic restenosis and decreased neointimal hyperplasia compared with controls. These findings highlight the importance of early initiators of the extrinsic coagulation pathway, especially factor VII and tissue factor, in the response to arterial injury.