Soluble forms of EphrinB2 and EphB4 reduce retinal neovascularization in a model of proliferative retinopathy.
OBJECTIVE
Ephrin ligands and their Eph receptors are key regulators of endothelial cell (EC) proliferation, migration, adhesion, and repulsion during mammalian vascular development. The hypothesis was that these molecules also play a role in pathologic neovascularization (NV) in the mouse model of oxygen-induced retinopathy.


METHODS
C57BL/6 mice at postnatal day (P)7 were exposed to 75% oxygen (O(2)) for 5 days (until P12) and allowed to recover in room air to induce retinal NV. Retinas from unexposed and hyperoxia-exposed mice between P7 to P24 were analyzed specifically for EphrinB2 and EphB4 transcript expression by RT-PCR. Phospho-Eph (p-Eph) receptor was evaluated during active EC proliferation at P15 and P17 by immunohistology. Some hyperoxia-exposed mice had one eye injected intravitreally with 150 ng/1.5 microL of soluble EphrinB2/Fc or EphB4/Fc chimeras during transition from high O(2) to room air (P12) and injected again on P14. Contralateral eyes were injected with human IgG as the control. Preretinal nuclei and retinal blood vessels were quantified at peak disease (P17).


RESULTS
EphrinB2 mRNA was constitutively expressed in the developing retina and was unchanged by hyperoxia. In contrast, EphB4 mRNA expression was modulated during normal retinal development and was altered by hyperoxia. Furthermore, p-Eph was detected in developing preretinal tufts, thus implying that Ephrin/Eph signaling system is active in this experimental model. Intravitreal injection of soluble versions of these molecules significantly reduced pathologic neovascularization. The number of preretinal nuclei in hyperoxia-treated mice was reduced by 66% (P < 0.05) in EphrinB2-injected eyes, whereas EphB4 treatment yielded a 69% reduction (P < 0.05), compared with control injections. Intraretinal vessel development was not altered by the injections.


CONCLUSIONS
These results support the hypothesis that endogenous EphrinB2 and EphB4 are regulators of retinal NV during oxygen-induced retinopathy and may be useful targets for therapeutic intervention.
Zamora
David O
DO
Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, 97239, USA.
Davies
Michael H
MH
Planck
Stephen R
SR
Rosenbaum
James T
JT
Powers
Michael R
MR
D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D036388:Ephrin-B2 / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D018496:Hyperoxia / Q000150:complications; D007150:Immunohistochemistry; D007231:Infant, Newborn; D007267:Injections; D051379:Mice; D008810:Mice, Inbred C57BL; D010100:Oxygen / Q000633:toxicity; D012333:RNA, Messenger / Q000378:metabolism; D036224:Receptor, EphB4 / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D015861:Retinal Neovascularization / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D012171:Retinal Vessels / Q000473:pathology; D012178:Retinopathy of Prematurity / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012995:Solubility
D036388:Ephrin-B2; D012333:RNA, Messenger; D036224:Receptor, EphB4; D010100:Oxygen