Roles of vascular endothelial growth factor and astrocyte degeneration in the genesis of retinopathy of prematurity.
OBJECTIVE
To assess the role of vascular endothelial growth factor (VEGF) in the feline model of retinopathy of prematurity (ROP).


METHODS
Retinopathy of prematurity was induced in neonatal cats by raising them in an oxygen-enriched (70% to 80%) atmosphere for 4 days to suppress vessel formation and then returning them to room air for 3 to 27 days. In situ hybridization was used to detect the expression of VEGF and its high-affinity receptor, flk-1, in the retina of neonatal cats, and glial fibrillary acidic protein immunocytochemistry was used to assess astrocyte status.


RESULTS
The expression of VEGF in the innermost layers of retina fell in hyperoxia and increased on return to room air. Vascular endothelial growth factor expression was transient; it was maximal where vessels were about to form, and it rapidly downregulated after vessels had formed. During the proliferative vasculopathy of ROP, VEGF expression was stronger than in the normally developing retina, and the astrocytes that normally express VEGF degenerated. After the degeneration of astrocytes, VEGF was expressed by neurones of the ganglion cell layer. flk-1 was expressed by intraretinal and preretinal vessels. Supplemental oxygen therapy reduced or eliminated the overexpression of VEGF expression, astrocyte degeneration, and formation of preretinal vessels.


CONCLUSIONS
Regulation of VEGF by tissue oxygen mediates the inhibition of vessel growth during hyperoxia and the subsequent proliferative vasculopathy. Degeneration of retinal astrocytes creates conditions for the growth of preretinal vessels.
Stone
J
J
Department of Molecular Biology, Hebrew University, Jerusalem.
Chan-Ling
T
T
Pe'er
J
J
Itin
A
A
Gnessin
H
H
Keshet
E
E
D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology*; D002415:Cats; D015536:Down-Regulation; D016228:Endothelial Growth Factors / Q000096:biosynthesis / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D007231:Infant, Newborn; D008222:Lymphokines / Q000096:biosynthesis / Q000502:physiology*; D010102:Oxygen Inhalation Therapy; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis; D017978:Receptors, Growth Factor / Q000096:biosynthesis; D040262:Receptors, Vascular Endothelial Growth Factor; D015861:Retinal Neovascularization / Q000473:pathology / Q000503:physiopathology; D012171:Retinal Vessels / Q000473:pathology*; D012178:Retinopathy of Prematurity / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D005904:Glial Fibrillary Acidic Protein; D008222:Lymphokines; D017978:Receptors, Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor