Retinal neuronal SOCS3 governs EGF signaling and neovascular growth

Abstract

Purpose: Neurovascular interactions are important in the maintenance of normal function in the nervous system, and defects in this relationship often lead to various forms of disease. Accumulating evidence suggests that crosstalk between vasculature and the retinal neuroglia, photoreceptors and other neural cells in diabetes might contribute to the pathogenesis of diabetic retinopa­thy. However, the molecular mechanisms regulating neurovascular interaction in pathologic retinal angiogenesis are not well known. We identified a novel mechanism by which neurons govern neovascularization in retinopathy through neuronal/glial SOCS3.

Methods: We generated conditional knockout of suppressor of cytokine signaling 3 (SOCS3) inneurons and glias by crossing mice expressing the Cre recombinase transgene under the control of the nestin (Nes) promoter with mice carrying Socs3/loxP. Pathologic retinal angiogenesis was studied using a mouse oxygen-induced retinopathy (OIR) model, in which neonatal pups are exposed to 75% oxygen from postnatal day (P) 7 to 12. Laser capture microdissection, RNA Isolation, quantitative RT-PCR and western blot were performed to analyse gene expressions. Immunohistochemistry and confocal imaging were performed to demonstrate protein localization and cell type identification. Immunoblot was used to demonstrate protein phosphorylation.

Results: Conditional Socs3 knockout mice (Socs3^Nes-ko) subjected to OIR had significantly increased levels of pathologic retinal neovascularization compared with littermate controls (Socs3^flox/flox) at P17 (Socs3^Nes-ko, 11.65%±0.65%, n=27; Socs3^flox/flox, 8.30%±0.57%, n=10; P=0.002). The vaso-obliterated retinal area was significantly reduced (p=0.004) in Socs3^Nes-ko (13.65%±1%, n=27) compared with Socs3^flox/flox mice (16.8%±0.49%, n=10). In neuronal/glial Socs3 deficient retinas Vegfa expression was significantly increased. Lack of neuronal/glial SOCS3 does not affect HIF-1α level, but resulted in high level of phospho-STAT3, elevated Vegf receptors Flt1 and Flk1 expression, and activated phospho-ERK.

Conclusions: In summary, neuronal/glial SOCS3 suppresses pathologic endothelial activation through inhibiting STAT3 activation mediated VEGF-induced ERK activation. Together this study identifies neuronal/glial SOCS3 as a novel regulator of neurovascular interaction and pathologic retinal angiogenesis through titration of VEGF signaling.