Thrombin effectuates therapeutic arteriogenesis in the rabbit hindlimb ischemia model: A quantitative analysis by computerized in vivo imaging

We report on an experimental mammalian controlled study that documents arteriogenic capacity of thrombin and utilizes computerized algorithms to quantify the newly formed vessels. Hindlimb ischemia was surgically invoked in 10 New Zealand white rabbits. After quiescence of endogenous angiogenesis heterologous bovine thrombin was intramuscularly injected (1500 units) in one hindlimb per rabbit (Group T). Contralateral limbs were infused with normal saline (Group C). Digital subtraction angiography (DSA) of both limbs was performed after thrombin infusion by selective cannulation of the abdominal aorta and digital images were post-processed with computerized algorithms in order to enhance newly formed vessels. Total vessel area and total vessel length were quantified. In vivo functional evaluation included measurements of blood flow volume at the level of the external iliac artery by Doppler ultrasonography both at baseline and at 20 days after thrombin infusion. Total vessel area and length (in pixels) were 14,713±1023 and 5466±1327 in group T versus 12,015±2557 and 4598±1269 in group C ( p = 0.0062 and 0.1526, respectively). Blood flow volumes (ml/min) at baseline and at 20 days after thrombin infusion were 25.87±11.09 and 38.06±11.72 in group T versus 26.57±11.19 and 20.35±7.20 in group C ( p = 0.8898 and 0.0007, respectively). Intramuscular thrombin effectuates an arteriogenic response in the rabbit hindlimb ischemia model. Computerized algorithms may enable accurate quantification of the neovascularization outcome.