Troubleshooting the rabbit ferric chloride-induced arterial model of thrombosis to assess in vivo efficacy of antithrombotic drugs.

INTRODUCTION: The FeCl3-induced arterial model of thrombosis is one of the most widely used animal models to assess arterial efficacy of new antithrombotic drug candidates. This model is well-established in rodents but in a less extent in the rabbit. In this work, we present a methodology for a rabbit FeCl3-induced arterial model of thrombosis derived from our troubleshooting which allows the generation of reliable efficacy data for new antithrombotic drug candidates. METHODS: Rabbits were administered with heparin 4.5U/kg/min, argatroban 10µg/kg/min or saline by intravenous infusion. The blood flow was monitored using a Doppler flow probe. The time from the application of FeCl3 to the recorded zero blood flow was defined as the time to occlusion, with a maximum recording time of 60min post-FeCl3 application. After 30min of infusion, thrombosis was induced by wrapping a FeCl3-saturated filter paper around the carotid artery caudal to the flow probe. Animals were subject to exclusion criteria based on the visual aspect of the artery FeCl3-induced injury and based on changes in blood flow upon FeCl3 application. RESULTS: Following the application of FeCl3, a mean time to occlusion for saline, heparin and argatroban of 24.3±1.8, 52.5±4.8 and 53.5±4.5min was obtained, respectively. Mean time to occlusion for heparin and argatroban administered groups was significantly different when compared to the saline-treated group (p<0.05). These results for the test compounds represent approximately 80% of the maximum possible prolongation. DISCUSSION: The rabbit FeCl3-induced arterial model of thrombosis presented in this paper derived from our troubleshooting is sensitive and reproducible for the generation of accurate and reliable efficacy data in the assessment of new antithrombotic agents in preclinical drug development.

An optimized method to assess in vivo efficacy of antithrombotic drugs using optical coherence tomography and a modified Doppler flow system.

INTRODUCTION: Animal models of venous and arterial thrombosis are extremely useful to study the efficacy of antithrombotic agents. Variability in efficacy data is often observed in those preclinical studies. The goal of this study was to optimize the methodology for assessing antithrombotic drug efficacy by the use of optical coherence tomography (OCT) and a modified Doppler flow system in rat models of thrombosis. METHODS: Thrombus formation was assessed in both the rat venous and arterial ferric chloride (FeCl(3)) models of thrombosis. In the venous model, thrombus volume post-treatment was measured using OCT, and data were correlated against the thrombus weight. In the arterial model, the time to occlusion was measured using a Doppler flow probe connected to a perivascular flow module which allowed the reporting of dynamic blood flow data every 30s. Heparin (130 or 165U/kg), argatroban (4.5mg/kg), bivalirudin (1.3mg/kg) or saline were administered intravenously. RESULTS: In the venous model, for all treatment groups a strong linear correlation (R(2)=0.998) was observed between thrombus volume measured by OCT and thrombus weight. In the arterial model, using a high sampling rate of a dynamic blood flow using a modified Doppler flow system provided data accuracy and precision of the time to occlusion measurement. DISCUSSION: This study demonstrates that OCT is a powerful tool for the assessment of antithrombotic drug efficacy. Furthermore, it shows that a high Doppler sampling rates of dynamic blood flow leads to data accuracy and precision.