Pilot study on suppression of Kr＆#252;ppel-like factor 6 for proliferation of human lens epithelial cells

Abstract

Background Kruppel-like factor 6 (KLF6) is related to the physiological or pathological process,such as growth,cell differentiation,proliferation,apoptosis,angiogenesis,tissue repair,and so on.But in ophthalmology,it is less reported about the expressing level of KLF6 protein in lens epithelial cclls (LECs) or the effect of KLF6 on the proliferation of human LECs.Objective This study was to investigate whether KLF6 can inhibit proliferation of human LECs.Methods KLF6 eukaryotic expression plasmid (pEGFP-C2-KLF6) was constructed using reverse transcription PCR(RT-PCR) and identified by double enzyme digestion method and PCR.Human LECs strain (HLE-B3) was cultured and passaged using low glucose DMEM containing 10％ fetal bovine serum and then divided into 4 groups.KLE-B3 transfection reagents were added in the culture medium of all groups.In addition,no agent was used in the blank control group;only insulin-like growth factor-1 (IGF-1) was appended to the medium in only IGF-1 group ;null vector was transfected and IGF-1 was appended in the null plasmid transfection+ IGF-1 group;while pEGFP-C2-KLF6 eukaryotic expression plasmid was transfected into the cells,and simultaneously IGF-1 was added in the pEGFP-C2-KLF6 plasmid transfection+IGF-1 group.After 24 hours of intervene,water soluble tetrazolium salt-1 (WST-1) test was used to detect the growth status of the cells,and Western blot assay was used to assay the relative expressing level of KLF6 protein in the cells.In the other hand,the cells were cultured at the density of 1 ×104/piece,and 0,0.10 and 0.25 μg pEGFP-KLF6 were transfected into each piece of cells respectively,and then IGF-1 was added with a final concentration of 50 μg/L for 24 hours after cell culture.Expressions of Ki-67 protein and mRNA in the cell pieces were detected by immunocytochemistry and fluorescent semiquantitative PCR,respectively.Results The PCR product bands were consistent with KLF-6 gene in length,and the product fragments were corresponding with expectant ones via PCR and double enzyme digestion method,showing a successful construction of pEGFP-C2-KLF6 eukaryotic expression plasmid.After 24 hours of IGF-1 stimulation,the absorbance values of the cells were 0.86±0.00,2.10±0.01,2.24±0.12 and 1.06±0.02 in the blank control group,only IGF-1 group,null plasmid transfection + IGF-1 group and the pEGFP-C2-KLF6 plasmid transfection + IGF-1 group,with a significant difference among the 4 groups (F =38.322,P ＜ 0.05),and that in the pEGFP-C2-KLF6 plasmid transfection +IGF-1 group was significantly lowed in comparison with the only IGF-1 group and the null plasmid transfection+IGF-1 group (q=6.42,7.31,both at P＜0.05).Western blot assay showed that the relative expressing levels of KLF6 protein were statistically different among the four groups (F =591.858,P＜0.05),and those in the pEGFP-C2-KLF6 plasmid transfection+IGF-1 group were 1.47,2.04,3.27 folds higher than those in the blank control group,only IGF-1 group,respectively and null plssmid transfection+IGF-1 group,respectively.Immunocytochemistry revealed that the expressing intensity of Ki-67 protein was gradually weakened with the decrease of pEGFP-C2-KLF6 plasmid dose in the 0,0.10 and 0.25 μg pEGFP-C2-KLF6 plasmid transfection+IGF-1 groups.Fluorescence semiquantitative PCR results showed that the relative expression values of Ki-67 mRNA in the cells were O.15±0.08 and 0.11±0.03 in the 0.10 μg and 0.25 μg pEGFP-C2-KLF6 plasmid transfection+ IGF-1 groups,which were significantly lower than O.77± 0.12 of the 0 μg pEGFP-C2-KLF6 plasmid transfection group,with a statistically significant difference among the three groups (F =54.825,P＜0.05).Conclusions KLF-6 can effectively inhibit IGF-1-induced proliferation of human LECs,and it can be regarded as one of the regulatory factors of the proliferation of HLE-B3 cells. Key words: Lens; Epithelial cell; Cell, cultured; Kruppel like factor; Plasmid; Transfection; Cell proliferation