krn-633 and Retinal-Neovascularization

An impairment of cellular interactions between the elements of the neurovascular unit contributes to the onset and/or progression of retinal diseases. The present study aims to examine how elements of the neurovascular unit are altered in a rat model of retinopathy of prematurity (ROP). Neonatal rats were treated subcutaneously with the vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitor KRN633 (10 mg/kg) on postnatal day (P) 7 and P8 to induce ROP. Morphological assessments were performed of blood vessels, astrocytes and neuronal cells in the retina. Aggressive angiogenesis, tortuous arteries and enlarged veins were observed in the retinal vasculature of KRN633-treated (ROP) rats from P14 to P28, compared to age-matched control (vehicle-treated) animals. Morphological abnormalities in the retinal vasculature showed a tendency toward spontaneous recovery from P28 to P35 in ROP rats. Immunofluorescence staining for glial fibrillary acidic protein and Pax2 (astrocyte markers) revealed that morphological changes to and a reduction in the number of astrocytes occurred in ROP rats. The developmental cell death was slightly accelerated in ROP rats; however, no visible changes in the morphology of retinal layers were observed on P35. The abnormalities in astrocytes might contribute, at least in part, to the formation of abnormal retinal blood vessels and the pathogenesis of ROP.

Topics: Animals; Disease Models, Animal; Female; Phenylurea Compounds; Pregnancy; Protein Kinase Inhibitors; Quinazolines; Rats; Rats, Sprague-Dawley; Retina; Retinal Neovascularization; Retinopathy of Prematurity; Vascular Endothelial Growth Factor A

Retinal arterial tortuosity and venous dilation are hallmarks of plus disease, which is a severe form of retinopathy of prematurity (ROP). In this study, we examined whether short-term interruption of vascular endothelial growth factor (VEGF) signals leads to the formation of severe ROP-like abnormal retinal blood vessels. Neonatal rats were treated subcutaneously with the VEGF receptor (VEGFR) tyrosine kinase inhibitors, KRN633 (1, 5, or 10 mg/kg) or axitinib (10 mg/kg), on postnatal day (P) 7 and P8. The retinal vasculatures were examined on P9, P14, or P21 in retinal whole-mounts stained with an endothelial cell marker. Prevention of vascular growth and regression of some preformed capillaries were observed on P9 in retinas of rats treated with KRN633. However, on P14 and P21, density of capillaries, tortuosity index of arterioles, and diameter of veins significantly increased in KRN633-treated rats, compared to vehicle (0.5% methylcellulose)-treated animals. Similar observations were made with axitinib-treated rats. Expressions of VEGF and VEGFR-2 were enhanced on P14 in KRN633-treated rat retinas. The second round of KRN633 treatment on P11 and P12 completely blocked abnormal retinal vascular growth on P14, but thereafter induced ROP-like abnormal retinal blood vessels by P21. These results suggest that an interruption of normal retinal vascular development in neonatal rats as a result of short-term VEGFR inhibition causes severe ROP-like abnormal retinal vascular growth in a VEGF-dependent manner. Rats treated postnatally with VEGFR inhibitors could serve as an animal model for studying the mechanisms underlying the development of plus disease.

Topics: Animals; Animals, Newborn; Axitinib; Disease Models, Animal; Female; Fluorescent Antibody Technique, Indirect; Imidazoles; Indazoles; Microscopy, Fluorescence; Phenylurea Compounds; Pregnancy; Protein-Tyrosine Kinases; Quinazolines; Rats; Rats, Sprague-Dawley; Retinal Neovascularization; Retinal Vessels; Retinopathy of Prematurity; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

The impaired function of angiogenic factors, including vascular endothelial growth factor (VEGF), during pregnancy is associated with preeclampsia and intrauterine growth restriction. To determine how the attenuation of VEGF signals during retinal vascular development affects retinal vascular growth and patterns, we examined the effects of pre- and post-natal treatment of mice with KRN633, a VEGF receptor tyrosine kinase inhibitor, on retinal vascular development and structure. Delays in retinal vascular development were observed in the pups of mother mice that were treated daily with KRN633 (5 mg/kg/day) from embryonic day 13.5 until the day of delivery. A more marked delay was seen in pups treated with the inhibitor (5 mg/kg/day) on the day of birth and on the following day. Pups treated postnatally with KRN633 showed abnormal retinal vascular patterns, such as highly dense capillary networks and decreased numbers of central arteries and veins. The high-density vascular networks in KRN633-treated pups showed a greater sensitivity to VEGF signaling inhibition than the normal vascular networks in vehicle-treated pups. Compared to vehicle-treated pups, more severe hypoxia and stronger VEGF mRNA expression were observed in avascular areas in KRN633-treated pups. These results suggest that a short-term loss of VEGF function at the earliest stages of vascular development suppresses vascular growth, leading to abnormal vascular patterning, at least in part via mechanisms involving VEGF in the mouse retina.

Topics: Administration, Oral; Animals; Animals, Newborn; Female; Fluorescein Angiography; Fluorescent Antibody Technique, Indirect; In Situ Hybridization; Male; Mice; Mice, Inbred ICR; Phenylurea Compounds; Platelet Endothelial Cell Adhesion Molecule-1; Pregnancy; Prenatal Exposure Delayed Effects; Quinazolines; Retinal Neovascularization; Retinal Vessels; RNA, Messenger; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2