Transforming growth factor beta 1 induces methylation changes in lung fibroblasts

Idiopathic pulmonary fibrosis is a complex disease of unknown etiology. Environmental factors can affect disease susceptibility via epigenetic effects. Few studies explore global DNA methylation in lung fibroblasts, but none have focused on transforming growth factor beta-1 (TGF-β1) as a potential modifier of the DNA methylome. Here we analyzed changes in methylation and gene transcription in normal and IPF fibroblasts following TGF-β1 treatment. We analyzed the effects of TGF-β1 on primary fibroblasts derived from normal or IPF lungs treated for 24 hours and 5 days using the Illumina 450k Human Methylation array and the Prime View Human Gene Expression Array. TGF-β1 induced an increased number of gene expression changes after short term treatment in normal fibroblasts, whereas greater methylation changes were observed following long term stimulation mainly in IPF fibroblasts. DNA methyltransferase 3 alpha (DMNT3a) and tet methylcytosine dioxygenase 3 (TET3) were upregulated after 5-days TGF-β1 treatment in both cell types, whereas DNMT3a was upregulated after 24h only in IPF fibroblasts. Our findings demonstrate that TGF-β1 induced the upregulation of DNMT3a and TET3 expression and profound changes in the DNA methylation pattern of fibroblasts, mainly in those derived from IPF lungs.

特发性肺纤维化（Idiopathic Pulmonary Fibrosis, IPF）是一种病因未明的复杂性疾病。环境因素可通过表观遗传效应影响疾病易感性。目前鲜有研究探讨肺成纤维细胞的全基因组DNA甲基化水平，且尚无研究将转化生长因子β1（transforming growth factor beta-1, TGF-β1）视为DNA甲基化组的潜在调控因子。本研究分析了正常肺成纤维细胞与IPF肺成纤维细胞在经TGF-β1处理后，其甲基化水平与基因转录的变化情况。本研究采用Illumina 450K人类甲基化芯片与Prime View人类基因表达芯片，分析了TGF-β1对分别源自正常肺与IPF肺的原代成纤维细胞的作用，处理时长分别为24小时与5天。在短期处理后，TGF-β1可诱导正常肺成纤维细胞出现更多的基因表达变化；而长期刺激下，甲基化水平的显著变化则主要出现在IPF肺成纤维细胞中。DNA甲基转移酶3α（DNA methyltransferase 3 alpha, DNMT3A）与四甲基胞嘧啶双加氧酶3（tet methylcytosine dioxygenase 3, TET3）在两种细胞经TGF-β1处理5天后，其表达均出现上调；而仅在IPF肺成纤维细胞经24小时处理后，DNMT3A的表达才会上调。本研究结果表明，TGF-β1可诱导DNMT3A与TET3的表达上调，并使成纤维细胞的DNA甲基化模式发生显著改变，这种改变主要见于源自IPF肺的成纤维细胞。