Heparinase enhances collateral vessel development in the ischemic limb

Several angiogenic factors are bound to heparin and stored in the extracellular matrix of diverse tissues; thus, the controlled release of these factors can provide a novel approach of angiogenic stimulation to ischemic tissues. The purpose of this study was to test the hypothesis that heparinase, when administered in vivo, might enhance collateral vessel development in the ischemic limb by the controlled release of angiogenic factors such as basic fibroblast growth factor (bFGF). Eleven male New Zealand White rabbits underwent ligation and excision of the common and superficial femoral arteries in the left hindlimb. In the heparinase group (n = 6), 9.7 IU of heparinase (in 3 ml saline) was injected intramuscularly to the left thigh daily for 10 days, beginning 11 days after surgery. In the control group (n = 5), inactivated heparinase (also in 3 ml saline) was administered following the same experimental protocol. Calf systolic pressure was measured in both hindlimbs and was expressed as a ratio of left to right (L/R ratio) before injections (on day 10) and after injections (on days 20, 30, and 40). Vascularization was quantified by comparing the number of vessels along a line drawn across the mid-thigh on angiograms taken 4 seconds after contrast injection at day 40 when the study was terminated. The intramuscular injection of heparinase improves perfusion to the ischemic limb through the process of enhanced collateral vessel development. The angiogenic effect of heparinase on the ischemic tissue may result from release of endogenous angiogenic factors, such as bFGF.