Chapter 3. The adenoviral vector angiogenesis/lymphangiogenesis assay

Adenoviral vectors expressing vascular permeability factor/vascular endothelial growth factor (VPF/VEGF, VEGF-A(164)) offer a powerful method for elucidating the mechanisms of pathological angiogenesis and lymphangiogenesis and for evaluating the effectiveness of pro- and anti-angiogenesis therapies. When injected into any of a variety of tissues in nude mice or rats, adenoviral vectors expressing VEGF-A(164) (Ad-VEGF-A(164)) induce the formation of six structurally and functionally distinct types of new blood vessels: mother vessels (MV), capillaries, glomeruloid microvascular proliferations (GMP), vascular malformations (VM), feeding arteries (FA), and draining veins (DV). Each of these abnormal vessel types may be found in tumors and in other examples of pathological angiogenesis. In addition, Ad-VEGF-A(164) induces the formation of highly abnormal and poorly functional "giant" lymphatics. The Ad-VEGF-A(164) assay has provided a means of elucidating the steps and mechanisms by which each type of new blood and lymphatic vessel forms, and for generating at defined times and in large numbers each of these different types of vessels for molecular study. Ear injection sites are advantageous in that the angiogenic and lymphangiogenic responses can be followed visually over time in intact animals, thus providing a convenient, inexpensive global screening assay for assessing the efficacy and toxicity of anti- or pro-angiogenic therapies. The assay can be readily extended to the study of the new blood vessels/lymphatics induced by adenoviral vectors expressing other growth factors and cytokines.