HIF-1α Dependent Upregulation of Angiogenic Factors by Mechanical Stimulation in Retinal Pigment Epithelial Cells

Abstract

Purpose : Mechanical stimulation as a mimic for drusen formation increases the expression of angiogenic factors in retinal pigment epithelial (RPE) cells, but the underlying molecular mechanisms have remained unknown. We here investigated and characterized the effects of mechanical stimulation on angiogenic factor expression in RPE cells both in vitro and in a mouse model.

Methods : Human RPE1 cells were subjected to stretch stimulation in culture. Gene expression was assessed by RT-qPCR analysis. Immunoblot analysis, RNA interference, and pharmacological inhibitors were applied to probe the roles of signaling molecules. Mechanical stimulation in vivo was studied with a bead-induced compression model.

Results : Mechanical stimulation increased the expression of vascular endothelial growth factor (VEGF) and other angiogenesis-related genes in cultured RPE1 cells. It also increased the abundance of hypoxia-inducible factor-1α (HIF-1α), and both HIF-1α knockdown and the HIF-1α inhibitor CAY10585 attenuated the effects of mechanical stimulation on angiogenic factor gene expression. Signaling by the tyrosine kinase SRC and p38 mitogen-activated protein kinase was implicated in the activation of HIF-1α and consequent angiogenesis-related gene expression induced by mechanical stimulation. Physical stimulation also increased VEGF and angiopoietin 2 gene expression in RPE cells in vivo in a manner sensitive to inhibition by intraocular injection of CAY10585.

Conclusions : Our results implicate SRC-p38 and HIF-1α signaling in the upregulation of angiogenic factors in RPE cells by mechanical stimulation. Attenuation of such upregulation of angiogenesis-related gene expression in vivo by a pharmacological inhibitor of HIF-1α suggests a potential new approach to the treatment of age-related macular degeneration.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.