VEGF expression and receptor activation in the choroid during development and in the adult.
OBJECTIVE
Previous studies have demonstrated a role for the retinal pigment epithelium (RPE) in the development and maintenance of the choroidal vasculature, suggesting that RPE serves a trophic role for the choroidal vessels. The goal of this study was to determine the expression pattern of vascular endothelial growth factor (VEGF) and its receptors and their activation status in embryonic and adult choroid, with the purpose of providing cues regarding the role of VEGF in development and stabilization of the choroidal vasculature.


METHODS
Transgenic VEGF-LacZ mice were used to examine VEGF expression in embryonic and adult eyes. Expression of VEGF isoforms and receptors in the RPE-choroid complex was assessed by RT-PCR and real-time PCR. VEGF receptor 2 expression was assessed by immunohistochemistry and its activation state was examined by immunoprecipitation followed by phosphotyrosine blot.


RESULTS
VEGF is expressed by RPE throughout the choroidal vascular development and in the adult. The major VEGF isoforms detected in adult RPE were VEGF120 and VEGF164, with almost no detectable VEGF188. RT-PCR analysis showed expression of VEGF receptors and coreceptors in the RPE-choroid complex. VEGFR2 was detected in the choriocapillaris underlying the RPE. Immunoprecipitation and phosphotyrosine blot of this receptor revealed that VEGFR2 is activated in adult mouse and bovine choroids.


CONCLUSIONS
The observations suggest that VEGF signaling is involved, not only in choroidal vessel formation, but perhaps also in the maintenance of the choriocapillaris.
Saint-Geniez
Magali
M
Schepens Eye Research Institute, the Department of Ophthalmology, Children's Hospital, Harvard Medical School, Boston, MA 02114, USA.
Maldonado
Angel E
AE
D'Amore
Patricia A
PA
D000818:Animals; D001011:Aorta / Q000166:cytology; D015153:Blotting, Western; D002478:Cells, Cultured; D002829:Choroid / Q000098:blood supply* / Q000196:embryology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D007124:Immunoenzyme Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics* / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D040301:Vascular Endothelial Growth Factor Receptor-2