The effects of hypoxia on the expression of AQP-4 in Miiller cells

Abstract

Background Hypoxia is an important cause resulting in many retinal diseases,such as retinal edema,diabetic retinopathy,proliferative retinopathy and so on. Objective This study is to investigate the effects of hypoxia on the expression of AQP-4 in Muller ceils in vitro. Methods Muller cells were isolated from New Zealand white rabbits and primarily cultured in DMEM containing 20% fetal bovine serum by the explant culture method. The cells were identified by immunostaining for the glial fibrillary acidic protein（ GFAP）. Generation 2 of cells was cultivated with the chemical hypoxia inducer, CoCl2 ,for 24 hours in the hypoxic group and only with DMEM in the control group. The expression of the AQP-4 protein in Mtiller cells was detected by immunocytochemistry. The expression of AQP-4 mRNA was determined by semi-quantitative reverse transcription-polymerase chain reaction （RT-PCR）. Results About 90% of Mtiller cells （generation 2） presented a positive immunoreactivity for GFAP, showing a brown staining in the cytoplasm. Cultured cells displayed the presence of intermediate filaments, microvillus and various cellular organs. The Integral absorbanee of the AQP-4 protein in Mtiller cells was markedly increased 24 hours after incubation with CoC12 in comparison with the control group （t = 6.74 ,P 〈 0.05 ）. The expression level of AQP-4 mRNA in MUller cells was significantly enhanced 24 hours after incubation with CoC12 in comparison with the control group （t = 21.79, P 〈 0.05 ）. Conclusion Hypoxia enchances the expression of AQP-4 in Mutiller cells and further increases fluid accumulation in the retina. These results suggest that Mtiller cells play an important role in the formation of retinal edema in diabetic retinopathy or proliferative retinopathy. Key words: aquaporin-4 ; Muller cell; retinal edema; hypoxia