Enhanced angiogenesis and growth of collaterals by in vivo administration of recombinant basic fibroblast growth factor in a rabbit model of acute lower limb ischemia: Dose-response effect of basic fibroblast growth factor

Abstract

The purpose of this study was to evaluate the effects of exogenous recombinant basic fibroblast growth factor (bFGF) on angiogenesis in severely ischemic tissue beds. We used a two-stage procedure to produce severe ischemia of the hindlimb of 34 New Zealand rabbits. The ischemic hindlimb received intramuscular injection of saline (group A), 1 μg bFGF (group B), or 3 μg bFGF (group C), daily for 2 weeks. Tissue perfusion, skeletal muscle infarction, angiogenesis, and collateral growth were assessed by angiography, transcutaneous oximetry (TcPo2), quantitative spectrophotometric assay of triphenyltetrazolium chloride reduction in muscle, capillary density (capillaries per square millimeter), and capillary per muscle fiber ratio. There were no significant differences in baseline TcPo2 among the three groups for both thigh and calf measurements. Angiography revealed extensive perfusion of the left hindlimb in all the assessed bFGF treated animals. Both thigh and calf TcPo2 values showed a significant increase in all groups over the 14 days ischemia was induced (p < 0.0001), but the two treatment groups exhibited a much more rapid rise in TcPo2 than the control group (p < 0.0001). The capillaries per square millimeter and capillaries per muscle fiber ratios were significantly increased in all posttreatment measurements for all animals that received bFGF. The treatment groups with bFGF had a significant (p = 0.025) increase in thigh muscle viability compared with controls based on triphenyltetrazolium chloride reduction. Whereas there was evidence of muscle infarction in both the thighs of groups A and B, there was none in group C. At the level of the calf, there was improvement in muscle viability in group B, but infarction was seen in both groups A and C (p = NS). The results in group C suggest that a high dose of bFGF in the thigh muscle may be protective, but in the more ischemic calf muscle may cause infarction. Generally there was a trend toward a dose-response effect for all posttreatment measurements except triphenyltetrazolium chloride reduction in the calf. We conclude that exogenous bFGF can enhance angiogenesis and growth of collaterals in a severely ischemic rabbit lower limb.