In vitro angiogenesis in ocular diseases

Angiogenesis in ocular diseases has been investigated using in vitro or in vivo methods. Although the results of in vitro studies do not always reflect the phenomena that occur in vivo, they have the great advantage that the number of environmental factors can be minimized. This is especially important in studying ocular angiogenesis because it involves so many dependent and independent factors and types of cells (including endothelial cells, pericytes, ganglion cells, and glial cells). Another advantage of in vitro methods to study angiogenesis is that separate assays are available to evaluate each of the four stages of angiogenesis (endothelial cell proliferation, migration, degradation of the basement membrane, and tube formation). A third advantage is that in vitro assays of the antiangiogenic factor vitamin E succinate are much more sensitive to angiogenesis-modulating factors than in vivo assays. Finally, cell-cell interactions can be evaluated by in vitro assay but not in vivo. For example, in vitro studies have shown that retinal pigment epithelial cells stimulate choroidal endothelial angiogenesis and that this angiogenic characteristic of RPE cells can be altered by retro-virus-mediated gene transfer of urokinase-type tissue plasminogen activator cDNA. Ophthalmic researchers should avail themselves of the advantages of in vitro studies for the investigation of angiogenesis.