Reversal of Retinal Vascular Changes Associated with Ocular Neovascularization by Small Molecules: Progress toward Identifying Molecular Targets for Therapeutic Intervention

The elucidation of the molecular pathogenesis of ocular disease provides candidate targets for treatment. Animal models allow for identification and quantitation of ocular diseases. By gaining insight regarding the molecular signals involved in various types of ocular angiogenesis, general concepts can emerge that may apply to other settings, including tumor angiogenesis. The hypoxia inducible factor-1 (HIF-1) pathway is relatively well understood and serves as a good example of how knowledge of the biological responses to hypoxia can translate into new therapies. Furthermore, HIF pathway can be used as a therapeutic target and that the manipulation of the HIF pathway at several points has potential use for the treatment of oxygen-dependent diseases in retina. However, there are numerous other molecular and cellular responses to hypoxia that are independent of HIF-1, perhaps each with unique oxygen sensors. Despite participation of multiple stimulatory factors for ocular neovascularization (NV), vascular endothelial growth factor (VEGF) emerges as a pivotal player, thus manipulation of VEGF signaling represents an important therapeutic strategy. While most studies have focused on prevention of ocular NV, regression of new vessels is desirable and is achievable with various small molecules. Screens are underway to identify and test the efficacy of these small-molecules to target various mechanisms involved in ocular NV. These small molecules might represent an important component of novel combination therapies to target various molecular signaling mechanisms in neovascular tissues.