Abstract
Purpose: :
Regulating angiogenesis in the retina is critical for preventing neovascularization in diseases such as diabetic retinopathy and age–related macular degeneration. Apelin is a novel angiogenic factor found in retinal endothelial cells. Apelin’s receptor, APJ, is highly expressed in retinal endothelial cells and it is implicated in capillary tube formation. This study was designed to determine if apelin and APJ are expressed in cultured rat Müller cells and whether their expression is altered by hypoxia.
Methods: :
A well–characterized rat Müller cell line, rMC–1, was used in these experiments. Müller cells were exposed to either normoxic or hypoxic conditions for 12 hours and analyzed with microarray. Immunocytochemistry to APJ was performed on rMC–1 cells grown in both normal and hypoxic conditions for 12 hours. Protein was extracted from rMC–1 cells grown in both normoxia and hypoxia for 24 hours for western blot analysis with antibody to APJ.
Results: :
We found apelin to be upregulated 5.6 fold (p=0.006) in rMC–1 Müller cells exposed to hypoxia by microarray analysis. Immunocytochemistry demonstrated that APJ is upregulated in rMC–1 cells exposed to 12 hours of hypoxia. Optical density analysis of western blots for APJ in rMC–1 cells showed a 1.7 fold increase in APJ protein in rMC–1 cells grown in hypoxic versus normal conditions.
Conclusions: :
Apelin and APJ are upregulated by hypoxia in rMC–1 Müller cells. This suggests a possible target for antiangiogenic therapy for retinal neovascular diseases.
Keywords: neovascularization • hypoxia • Muller cells