Localization of VEGF receptor-2 (KDR/Flk-1) and effects of blocking it in oxygen-induced retinopathy.
OBJECTIVE
Vascular endothelial cell growth factor (VEGF) has been implicated in vascular development and in proliferative retinopathies. The goal of this study was to examine the immunohistochemical localization and relative levels of VEGF receptor-2 (KDR) in canine retina during postnatal vasculogenesis and during angiogenesis in oxygen-induced retinopathy (OIR) and to investigate the effects of neutralizing KDR on these processes.


METHODS
Eyes from normal dogs ranging from 1 to 22 days of age and age-matched oxygen-treated animals were snap frozen for immunohistochemical analysis with antibodies against human KDR. To examine the effects of blocking KDR, 6-day-old air-reared control and oxygen-treated animals were surgically implanted with slow release polymer pellets containing control IgG or anti-KDR. Material eluted from pellets was assessed using a binding assay (measures binding to soluble KDR) to determine the kinetics of anti-KDR release and endothelial cell proliferation to measure bioactivity. Animals were killed at 22 days of age and tissues examined with adenosine diphosphatase (ADPase) histochemical staining of blood vessels.


RESULTS
KDR immunoreactivity was only weakly associated with developing retinal vessels and was not observed in angioblasts throughout normal postnatal development. Immunoreactivity was very strong in reforming retinal vessels and intravitreal neovascularization in oxygen-treated animals. Anti-KDR had no effect on vessel morphology or growth in air-reared control animals. In oxygen-treated animals, anti-KDR significantly inhibited revascularization of the retina (P = 0.005) and formation of intravitreal neovascularization compared with control IgG pellet eyes (P < 0.04).


CONCLUSIONS
KDR/Flk-1 was only weakly associated with normal developing primary retinal vessels but was strongly expressed by proliferating endothelial cells in reforming retinal vessels and intravitreal neovascularization after hyperoxic insult. Anti-KDR antibody delivered by slow-release pellets had no effect on normal vasculogenesis, but it inhibited the formation of intravitreal neovascularization and retinal vessel development in OIR. The study suggests that blocking KDR may be beneficial for treating pathologic angiogenesis in adult tissue.
McLeod
D Scott
DS
Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Taomoto
Makoto
M
Cao
Jingtai
J
Zhu
Zhenping
Z
Witte
Larry
L
Lutty
Gerard A
GA
D000818:Animals; D000831:Animals, Newborn; D019138:Antibodies, Blocking / Q000008:administration & dosage; D001081:Apyrase / Q000378:metabolism; D004195:Disease Models, Animal; D004285:Dogs; D004730:Endothelium, Vascular / Q000378:metabolism; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism; D007124:Immunoenzyme Techniques; D007074:Immunoglobulin G / Q000276:immunology; D007231:Infant, Newborn; D018919:Neovascularization, Physiologic; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000276:immunology / Q000378:metabolism*; D040262:Receptors, Vascular Endothelial Growth Factor; D012160:Retina / Q000378:metabolism*; D015861:Retinal Neovascularization / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D012171:Retinal Vessels / Q000201:enzymology / Q000473:pathology; D012178:Retinopathy of Prematurity / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control
D019138:Antibodies, Blocking; D007074:Immunoglobulin G; D017978:Receptors, Growth Factor; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D001081:Apyrase