Discoidin Domain Receptor2 (DDR2) inhibits the development of experimental CNV and RNV in mice

Abstract

Purpose: Intraocular neovascular disease，such as choroidal neovascularization (CNV) and retinal neovascularization (RNV), is the most frequent causes of severe and progressive vision loss, while its pathogenesis is still poorly understood. The etiology of neovascular growth is multi-factorial and complicated, and a number of genetic and environmental factors have been cited as possible risk factors for its formation. In view of our recent finding that discoidin domain receptor 2 (DDR2), a collagen-binding receptor tyrosine kinase, is involved in controlling vascular endothelial activity and tumor angiogenesis. These findings stimulated our interest to investigate whether DDR2 similarly plays a role in the pathogenesis of these intraocular neovascular disease.

Methods: DDR2 deletion mutant mice and their wild type littermates were used. CNV was induced by laser photocoagulation in DDR2-/- slie mice. The severity of the CNV was evaluated by FFA, histopathological and choroidal flatmount analysis 14 days after laser treatment. Down- and up-regulate DDR2 expression through intravitreous injection of DDR2 siRNA or adenovirus-mediated strategy to confirm the role of DDR2 in CNV development. OIR was induced at postnatal day 7 (P7) by exposure to hyperoxia (75 % O2) for 5d and normoxia (21 % O2) for 5d. At P17, the severity of OIR was evaluated by retinal flatmounts and histopathological analysis. Human RPE cell line ARPE19 was infected with Ad-EGFP or Ad-DDR2 for 24 h, and the cells were then cultured under nomoxia or hypoxia conditions for another 24 h. The expression levels of DDR2, Ang-2, and VEGF-A were analyzed by western blot.

Results: DDR2 mutant mouse exhibited enhanced amplitude of laser-induced CNV. The inhibitory role of DDR2 in CNV development was further confirmed by experiments through intravitreal injection of DDR2 siRNA or DDR2-expressing adenovirus. It was also shown that in OIR model, mutant mice had larger areas of retinal nonperfusion and more vascular endothelial cells penetrating the internal limiting membrane than wild type mice. In ARPE19 cell line, hypoxia-induced upregulation of Ang-2 and VEGF-A was inhibited by enhanced expression of DDR2.

Conclusions: These data identified an anti-angiogenic role of DDR2 in laser-induced CNV and experimental ROP. This study may suggest DDR2 as a potential new target for the prevention of human pathological ocular neovascularization.