中文摘要：

目的探讨人胚肺成纤维细胞复制性衰老及过氧化氢诱导的早衰过程中Foxa2的表达改变及其启动子区CpG岛的甲基化水平变化。方法按传代情况将人胚肺成纤维细胞分为年轻细胞[第22代细胞，即22PDL（population doubling levels，群体倍增水平）1组、中年细胞（35PDL）组、复制性衰老细胞（49PDL）组和氧化应激诱导的早衰细胞（premature senescence，PS）组。用荧光定量PCR方法检测人胚肺成纤维细胞衰老过程中Foxa2的mRNA表达改变，应用甲基化特异性PCR（MSP）检测启动子区-777--478bp甲基化的变化情况，并用亚硫酸氢盐修饰基因组结合克隆测序检测启动子区域CpG岛的甲基化水平。结果与年轻细胞组比较，中年细胞组人胚肺成纤维细胞Foxa2mRNA的表达水平无明显变化；而复制性衰老细胞组和早衰细胞组人胚肺成纤维细胞Foxa2的mRNA表达水平均显著降低，差异有统计学意义（P〈0．05）。早衰细胞组的启动子区具有一定的甲基化水平；年轻细胞组、复制性衰老细胞组及早衰细胞组Foxa2启动子区CpG岛的甲基化水平分别为5．7％，17．1％和43．6％。结论人胚肺成纤维细胞衰老过程中Foxa2的mRNA表达水平逐渐降低，其启动子区CpG岛甲基化水平逐渐升高，参与其表达调控。

英文摘要：

Objective To explore the expression and the methylation level of the CpG island in its promoter of Foxa2 during cellular replicative senescence and premature senescence induced by hydrogen peroxide of human embryonic lung fibroblasts （HEFs）. Methods The HEFs were divided into young ceils （22 population doubling levels, 22PDL）, middle-aged cells（35PDL） and replicative senescent cells（49PDL） and premature senescent cells induced by H202 （premature senescence, PS） according to the age definition in cell culture. The mRNA level of Foxa2 was detected by Q-PCR in different groups during cellular senescence of HEFs. The methylation status in the promoter region （-777-478 bp） was observed by methylationspecific PCR. The CpGs island methylation level was detected by bisulfite sequencing. Results The mRNA level for Foxa2 had no distinct change in middle-aged cells, while it decreased in both replicative senescence and premature senescence with statistical significant difference （P〈0.05） compared with that of young cells. It had a certain methylation level in -777--478 bp of premature senescence group. The average rate of methylation in the promoter of Foxa2 was 5.7% in the young cells, 17.1% in the replicative senescent cells and 43.6% in the premature sensescent cells. Conclusion The increasing methylation of CpG island in the promoter of Foxa2 is involved in regulating its decreasing mRNA expression during cellular senescence of HEFs.