Influence of monochromatic light exposure on the growth of Miiller cell and the expression of myopia-related cell factors in vitro

Abstract

Background Research showed that exposure of 530 nm monochromatic light can induce myopia in animal,and retinal Muller cells participate in the formation of myopia.However,the effect and mechanism of retinal Muller cells during the formation of monochromatic light induced-myopia is below understood.Objective This study was to investigate biologic characteristics of rat retina Muller cells and the expression of cell factors in Muller cells after being illuminated by the 530 nm monochromatic light,and discuss the role of the retina Muller cells in myopia induced by monochromatic light.Methods Immortalized rat retinal Muller cells were cultured with DMEM containing 10％ fetal bovine serum in a self-made cell incubator with monochromatic light by adjusting luminance of 530 nm LED source.The cells were exposed to 125,250 and 500 lx luminance respectively for 6,12 and 24 hours,and the cells without light-irradiation were used as control.The growth of the cells under the different light time and different illuminations was described by MTT as the absorbance at the wavelength 570 nm (A570),and cell cycle analysis of Muller cells was performed by flow cytometry 48 hours after cultured,and the expression of transforming growth factor-beta 1 (TGF-β1),tyrosine hydroxylase(TH),inducible nitric oxide synthase(iNOS) and basic fibroblast growth factor(bFGF)in the cells were detected by reverse transcription PCR(RT-PCR),respectively.Results The Muller cells were uniform in size with polygonal shape and defined edges.No statistically significant difference was found in the A570 value in the cells of the 125 lx and 250 lx illuminated groups compared with the control group in various time points(P＞0.05).However,significant lowing was seen in the A570 value in the cells of the 500 lx illuminating for 12 hours and 24 hours in comparison with the control group (P =0.013,0.001).Compared with the control group,the ratio of the number between G2 and G1 phase was not significantly declined in 125 lx,250 lx illuminating for 48 hours (P =0.073,0.330),and the ratio in the 500 lx illuminating group was significantly lower than those in the 250 lx illuminated group and the control group (P =0.028,0.038).RT-PCR revealed that the expression of TGF-β1 mRNA in the cells was higher in the 250 lx illuminated group than that of the 500 lx illuminated group (P=0.006).The expression of iNOS mRNA was gradually upregulated in the 250 lx illuminated group compared with the control group (P =0.001),but that in the 500 lx illuminated group was downregulated (P =0.000).The expression of bFGF mRNA was raised in the 125 lx and 250 lx groups but reduced in the 500 lx group when compared with the control group(P=0.002,0.000,0.005).Also,the expression of TH mRNA was significantly increased in the 250 lx group(P=0.000),but decreased in the 500 lx group(P=0.000,P=0.001).Conclusions The monochromatic light of 530 nm can inhibit the growth of rat Muller cells and downregulate the expression of myopia-related cell factors and therefore exert effect in the formation of myopia. Key words: Monochromatic light; Muller cell; Myopia; Transforming growth factor-beta 1 ; Tyrosine hydroxylase; Inducible nitric oxide synthase; Basic fibroblast growth factor