VEGFR2 and VEGF-C Suppress the Epithelial–Mesenchymal Transition via YAP in RPE Cells

Abstract

Purpose : RPE cells play critical roles in maintaining retinal homeostasis. Dysfunctions in RPE cells lead to ocular diseases including age-related macular degeneration (AMD), proliferative vitreoretinopathy (PVR) and Leber congenital amaurosis (LCA). It has been reported that RPE cells not only secrete VEGF-A to support choroidal vasculature, but also express VEGFR2, the receptor of VEGFs. Anti-VEGF-A drugs have been routinely used to inhibit ocular revascularization, and drugs targeting VEGFR2, are also under development, however, the impact of VEGF signaling inhibition on RPE cell functions, particularly epithelial–mesenchymal transition (EMT) of RPE, remains to be fully elucidated. The purpose of this study is to investigate the effects of VEGF signaling inhibition on EMT of RPE cells.

Methods : siRNAs were utilized to knock down expression of genes in both human primary RPE and ARPE-19 cells. Real-time quantitative PCR (RT-PCR) and Western blotting analysis were hired to investigate the expression of typical EMT markers, fibronectin, collagen I and the hippo pathway markers YAP, CTGF and CYR61. A neutralization antibody was used to block VEGF-A.

Results : We found VEGFR2 is required to inhibit epithelial–mesenchymal transition (EMT) in RPE cells. We further revealed that loss of VEGF-C rather than VEGF-A induces EMT in these cells. Mechanistically, we showed that the VEGFR2 ablation-induced EMT in RPEs is mediated by activation of YAP, an effector of the Hippo pathway.

Conclusions : Our results disclose unexpected novel roles of VEGFR2 and VEGF-C in the Hippo pathway and in the process of EMT of RPE cells. These results call attention to the potential risks in the fields of anti-VEGFR2 and anti-VEGF-C drug development.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.