Role of vitronectin receptor-type integrins and osteopontin in ischemia-induced retinal neovascularization.
OBJECTIVE
It has been reported that vitronectin receptor-type integrins mediate vascular cell proliferation and migration. In this study, we investigated the expression of vitronectin receptor-type integrins and osteopontin in ischemia-induced retinal neovascularization, and examined the role of osteopontin in angiogenesis as a ligand of vitronectin receptor-type integrins.


METHODS
Retinal neovascularization was produced by exposing C57BL/6J mice to 75% oxygen from postnatal day (P) 7 to P12. Expression of vitronectin receptor-type integrins and osteopontin was assessed by Northern blot analysis, in situ hybridization, and immunofluorescence. The role of osteopontin in retinal angiogenesis was evaluated by tube formation assay using cultured bovine retinal microcapillary endothelial cells.


RESULTS
In the murine model, integrin alpha(v) mRNA was increased from P14 with a 2.6-fold peak response observed on P19, when retinal neovascularization was remarkable. Indirect immunofluorescence for vitronectin receptor-type integrins revealed prominent expression of integrin alpha(v)beta3/beta5 in the neovascular endothelial cells. Osteopontin mRNA was increased from P14, with a 2.0-fold peak response observed on P19. In situ hybridization demonstrated localization of osteopontin mRNA in neovascular tufts. Vascular endothelial growth factor-induced tube formation (8.3 +/- 0.6 mm/field) was inhibited significantly by treatment with anti-osteopontin antibody (4.8 +/- 0.7 mm/field, P <.001).


CONCLUSIONS
These data suggest that increased expression of both vitronectin receptor-type integrins and osteopontin in ischemic retina contribute to vascular endothelial cell proliferation and to retinal vascular formation by promoting interaction between endothelial cells and extracellular matrix, which leads to retinal neovascularization.
Takagi
Hitoshi
H
Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Suzuma
Kiyoshi
K
Otani
Atsushi
A
Oh
Hideyasu
H
Koyama
Shinji
S
Ohashi
Hirokazu
H
Watanabe
Daisuke
D
Ojima
Tomonari
T
Suganami
Eri
E
Honda
Yoshihito
Y
D000818:Animals; D000831:Animals, Newborn; D015152:Blotting, Northern; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005455:Fluorescent Antibody Technique; D017403:In Situ Hybridization; D007511:Ischemia / Q000150:complications*; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D053495:Osteopontin; D012333:RNA, Messenger / Q000378:metabolism; D019030:Receptors, Vitronectin / Q000235:genetics / Q000378:metabolism*; D015861:Retinal Neovascularization / Q000209:etiology / Q000378:metabolism*; D012171:Retinal Vessels / Q000378:metabolism / Q000473:pathology; D012795:Sialoglycoproteins / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; D019030:Receptors, Vitronectin; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D053495:Osteopontin