Abstract
Abstract: :
Purpose: Retinal Müller cells play an important role in supporting retinal neurons and retinal blood vessels. Pigmented epithelial–derived factor (PEDF) is a neurotrophic factor and an angiogenesis inhibitor. However, the regulation of PEDF expression is largely unknown. This study is to investigate the regulation of PEDF expression in retinal Müller cells and the effects of PEDF on Müller cell viability under normoxia and hypoxia. Methods: A rat Müller cell line (rMC–1) and primary bovine retinal capillary endothelial cells (BRCEC) were used. Recombinant PEDF was purchased from BioProducts MD, LLC. Cobalt chloride (CoCl2, 100–1600 µM) or low O2 concentration (<1%) was applied to rMC–1 for 24 h to induce hypoxia. PEDF of concentrations 10–640 nM was used in the experiment. Cell viability was analyzed by MTT assay. Cell apoptosis was detected via DNA fragmentation. Intracellular PEDF levels were determined by Western blot analysis and normalized by ß–actin levels. PEDF mRNA levels were measured by real time PCR. Results: Both low O2 concentration– and CoCl2–induced hypoxia resulted in apoptosis of retinal Müller cells. PEDF significantly prevented hypoxia–induced Müller cell apoptosis. PEDF expression was significantly down–regulated by hypoxia at both the mRNA and protein levels. PEDF upregulated the expression of endogenous PEDF at both the mRNA and protein levels in Müller cells but not in BRCEC in a dose–dependent manner under both normoxia and hypoxia. Conclusions: Hypoxia induces apoptosis of Müller cells and down–regulates PEDF expression. PEDF prevents hypoxia–induced Müller cell apoptosis and up–regulates the expression of itself in an autocrine manner. The mechanism for the PEDF autocrine regulation remains to be studied.
Keywords: growth factors/growth factor receptors • Muller cells • diabetic retinopathy