目的探讨转录因子CCCTC结合因子(CTCF)对翼状胬肉中B淋巴细胞瘤-2基因(Bcl-2)表达的调控及其分子机制。
方法纳入2017年6月至2019年2月在长沙市第一医院眼科行翼状胬肉切除联合自体角膜缘干细胞移植术治疗的原发性翼状胬肉患者22例，术中收集翼状胬肉组织作为翼状胬肉组；同期纳入因结膜裂伤、眼球破裂伤或眼球穿通伤就诊的眼外伤患者20例，取眼外伤修复手术过程中切取的少量正常结膜组织作为正常结膜组。分别采用实时荧光定量PCR和Western blot法检测各组样本中CTCF及Bcl-2的表达水平；采用亚硫酸氢盐处理后测序法(BSP)检测各组样本中Bcl-2启动子DNA甲基化水平。分离并培养翼状胬肉成纤维细胞，使用波形蛋白抗体进行免疫组织化学鉴定成纤维细胞。将分离培养的细胞分成2个组，CTCF干扰组转染CTCF干扰质粒，对照组转染对照质粒。采用实时荧光定量PCR法和Western blot法检测CTCF、Bcl-2表达水平；采用细胞计数试剂盒8检测各组培养12、24和48 h细胞增生活性；采用BSP检测各组样本中Bcl-2启动子DNA甲基化水平。比较各组各指标差异，采用Pearson线性相关分析探讨翼状胬肉组织中Bcl-2 mRNA与CTCF蛋白及Bcl-2基因启动子甲基化水平的相关性。
结果翼状胬肉组CTCF mRNA及蛋白相对表达水平分别为7.23±3.34和0.92±0.21，明显高于正常结膜组的1.10±0.44和0.28±0.07，差异均有统计学意义(t＝－8.136、－13.025，均P<0.01)。翼状胬肉组Bcl-2 mRNA及蛋白相对表达水平分别为10.27±4.64和0.95±0.27，高于正常结膜组的1.10±0.41和0.32±0.14，差异均有统计学意义(t＝－8.789、－10.782，均P<0.01)。翼状胬肉组CTCF蛋白相对表达量与Bcl-2 mRNA相对表达量呈显著正相关(r＝0.746，P<0.01)。翼状胬肉组Bcl-2启动子区DNA甲基化水平为0.65±0.09，低于正常结膜组的0.83±0.06，差异有统计学意义(t＝7.408，P<0.01)。翼状胬肉组Bcl-2启动子DNA甲基化水平与Bcl-2 mRNA相对表达量呈显著负相关(r＝－0.635，P<0.01)。CTCF干扰组CTCF及Bcl-2 mRNA相对表达水平为0.37±0.03和0.53±0.06，明显低于对照组的1.02±0.06和0.99±0.07，差异均有统计学意义(t＝20.035、9.029，均P<0.01)；CTCF干扰组CTCF及Bcl-2蛋白相对表达水平为0.23±0.06和0.56±0.07，低于对照组的0.52±0.05和0.92±0.12，差异均有统计学意义(t＝6.914、4.719，均P<0.01)。CTCF干扰组转染后12、24和48 h细胞活力分别为0.10±0.01、0.17±0.01和0.38±0.04，低于对应时间点对照组的0.12±0.01、0.29±0.01和0.85±0.06，差异均有统计学意义(t＝3.718、18.350、15.621，均P<0.01)。CTCF干扰组Bcl-2启动子DNA甲基化水平为0.75±0.04，明显高于对照组的0.61±0.03，差异有统计学意义(t＝－4.472，P<0.05)。
结论翼状胬肉中CTCF高表达，其可能通过下调启动子DNA甲基化水平介导Bcl-2异常表达。
ObjectiveTo investigate the regulation of transcription factor CCCTC binding factor (CTCF) on the expression of B-cell lymphoma 2 (Bcl-2) gene in pterygium and its molecular mechanism.
MethodsPterygium tissue samples from 22 primary pterygium patients who underwent pterygium excision combined with autologous limbal stem cell transplantation in The First Hospital of Changsha from June 2017 to February 2019 were collected during the operation as pterygium group.Normal conjunctival tissue from 20 patients with ocular trauma due to conjunctiva rupture, eyeball rupture or eyeball perforation in the same period were collected during the repair of ocular trauma as control group.Real-time PCR and Western blot were used to detect the expression levels of CTCF and Bcl-2 in the two groups.The DNA methylation level of the Bcl-2 promoter in the samples of the two groups was detected by bisulfite sequencing PCR (BSP). Pterygium fibroblasts were isolated and cultured.Fibroblasts were identified by immunohistochemistry using vimentin antibody.The cultured pterygium fibroblasts were divided into a CTCF interference group transfected with CTCF interference plasmid, and a control group transfected with control plasmid.The expression levels of CTCF and Bcl-2 in pterygium fibroblasts in CTCF interference and control groups were detected by real-time PCR and Western blot.The cell vitality was detected with cell counting kit-8 at 12, 24, and 48 hours after transfection.The DNA methylation level of the Bcl-2 promoter in the cells of the CTCF interference and control groups after transfection was determined by BSP.Differences of the indexes among groups were analyzed.Correlation between Bcl-2 mRNA and Bcl-2 gene promoter methylation level of CTCF protein in pterygium tissue was analyzed by Pearson linear correlation analysis.This study protocol was approved by the Ethics Committee of The First Hospital of Changsha (No.KL-2017021). Written informed consent was obtained from the patients from whom the specimens were collected.
ResultsThe relative expression levels of CTCF mRNA and protein in pterygium group were 7.23±3.34 and 0.92±0.21, respectively, which were significantly higher than 1.10±0.44 and 0.28±0.07 in normal conjunctiva group (t=-8.136, -13.025; both at P<0.01). The relative expression levels of Bcl-2 mRNA and protein in pterygium group were 10.27±4.64 and 0.95±0.27, which were higher than 1.10±0.41 and 0.32±0.14 in normal conjunctiva group, showing statistically significant differences (t=-8.789, -10.782; both at P<0.01). The CTCF protein expression was significantly positively correlated with the Bcl-2 mRNA expression in pterygium group (r=0.746, P<0.01). The DNA methylation level of the Bcl-2 promoter in pterygium group was 0.65±0.09, which was lower than 0.83±0.06 in normal conjunctiva group, with a statistically significant difference (t=7.408, P<0.01). The DNA methylation level was significantly negatively correlated with the Bcl-2 mRNA expression in pterygium group (r=-0.635, P<0.01). After the interference of CTCF expression in pterygium fibroblasts, the relative expression levels of CTCF and Bcl-2 mRNA in CTCF interference group were 0.37±0.03 and 0.53±0.06, which were significantly lower than 1.02±0.06 and 0.99±0.07 in control group (t=20.035, 9.029; both at P<0.01). The relative expression levels of CTCF and Bcl-2 proteins in CTCF interference group were 0.23±0.06 and 0.56±0.07, which were lower than 0.52±0.05 and 0.92±0.12 in control group, showing statistically significant differences (t=6.914, 4.719; both at P<0.01). The cell viability of pterygium fibroblasts in CTCF interference group was 0.10±0.01, 0.17±0.01, 0.38±0.04 at 12, 24, and 48 hours after interference, respectively, which were lower than 0.12±0.01, 0.29±0.01 and 0.85±0.06 in control group, and the differences were statistically significant (t=3.718, 18.350, 15.621; all at P<0.01). The DNA methylation level of Bcl-2 promoter in CTCF interference group was 0.75±0.04, which was significantly higher than 0.61±0.03 in control group (t=-4.472, P<0.05).
ConclusionsCTCF is excessively expressed in pterygium, which may mediate the overexpression of Bcl-2 through down-regulating DNA methylation level.
殷秀琴,于莉,易璐,等. CCCTC结合因子对翼状胬肉中B淋巴细胞瘤-2基因表达的调控及其机制[J]. 中华实验眼科杂志,2023,41(05)：421-427.
DOI:10.3760/cma.j.cn115989-20211108-00611版权归中华医学会所有。
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殷秀琴：参与研究选题、研究实施、论文撰写；方家华：参与研究选题、实验指导、论文修改和定稿；于莉、易璐：参与研究实施、数据分析
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