Ocular neovascularization: a valuable model system.
There is no unique formula for angiogenesis. Instead there is a large group of potential participating proteins that interact in complex ways. Depending upon the surrounding cell types and the relative expression levels of angiogenesis-related proteins, the 'angiogenesis cascade' can vary. Therefore, it is valuable to study and compare the role of proteins in several well-characterized vascular beds. The eye provides a useful model system, because it contains several vascular beds sandwiched between avascular tissue. This allows for unequivocal identification and quantitation of new vessels. Retina-specific promoters combined with inducible promoter systems provide a means to regulate the expression of proteins of interest. As a relatively isolated compartment, the eye also provides advantages for gene transfer. 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. One concept that has emerged is that despite participation of multiple stimulatory factors for ocular neovascularization, VEGF plays an essential role and interruption of VEGF signaling is an important therapeutic strategy. Another concept is that while most studies have focused on prevention of ocular neovascularization, regression of new vessels is desirable and is achievable with at least three agents, combretastatin A-4 phosphate, pigment epithelium-derived factor, and angiopoietin-2. Finally, endostatin and angiostatin, which have been sources of controversy because of inconsistent results in tumor models, have been shown to have good efficacy when delivered by gene transfer in models of ocular neovascularization. These results provide leads for new ocular treatments and perspective for evaluation of studies of neovascularization in extraocular tissues.
Campochiaro
Peter Anthony
PA
Department of Ophthalmology, The Johns Hopkins University School of Medicine, Maumenee 719, 600 N. Wolfe Street, Baltimore, MD 21287-9277, USA. pcampo@inmi.edu
Hackett
Sean Francis
SF
D020533:Angiogenesis Inhibitors / Q000627:therapeutic use; D000818:Animals; D002829:Choroid / Q000098:blood supply; D004195:Disease Models, Animal; D016228:Endothelial Growth Factors / Q000502:physiology; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D005123:Eye / Q000098:blood supply*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology; D008222:Lymphokines / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D012171:Retinal Vessels / Q000473:pathology*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D020533:Angiogenesis Inhibitors; D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D019001:Nitric Oxide Synthase