Evaluation of Angiogenesis

Every year, thousands of individuals around the world suffer from severe lower extremity vascular disorders that are amenable to neither medical nor surgical treatment, and thus amputation is required. A substantial portion of these amputations might be avoided by stimulating blood vessel growth to the affected lower extremity. In a new therapeutic approach, certain recombinant growth factors, administered as genes or recombinant proteins, have been used successfully to promote neovascularization (1 ,2 ). However, prior to the investigation of such therapy in human patients, it is necessary to obtain specific information in animal studies regarding the basic mechanisms involved in lower-extremity collateral vessel development. In particular, the use of genetically engineered mice (e.g., mice that have specific genes deleted or overexpressed) allows one to investigate relevant key factors for neovascularization that can be related to human subjects (3 -6 ). Accordingly, we developed a murine model of angiogenesis (7 ). In this model, the left femoral artery, including all major side branches of one hind limb, is excised, rendering the limb ischemic. The subsequent development of collateral blood vessels in the ischemic limb can then be monitored in vivo at arbitrarily selected time-points by laser Doppler perfusion imaging, and measured ex vivo by immunohistochemistry to determine capillary density.