Integrative blood-derived epigenetic and transcriptomic analysis reveals the potential regulatory role of DNA methylation in ankylosing spondylitis

Application of methylation in the diagnosis of ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease, mainly characterized by perifibrocartilage osteitis of the sacroiliac joints and spinal enthesitis. To date, the exact pathogenesis of AS remains elusive. It is generally believed that AS is a multifactorial disease involving genetics, infection, environment, and immunity. Among them, genetic factors are the primary determinants of disease risk and severity. In recent years, epigenetic mechanisms such as DNA methylation have been extensively surveyed with respect to the pathogenesis of AS. This review summarizes the latest research progress of methylation in AS, from whole-genome sequencing to individual differentially methylated gene. And finally, the role of methylase in AS inflammation, autophagy, and osteogenic differentiation was explored. In summary, the results of this review attempt to explain the role of methylation in the occurrence and development of AS and point out the shortcomings of current methylation research, providing directions for subsequent methylation research in AS.

Deoxycholic acid inducing chronic atrophic gastritis with colonic mucosal lesion correlated to mucosal immune dysfunction in rats

The present study aimed to explore the underlying mechanism of bile reflux-inducing chronic atrophic gastritis (CAG) with colonic mucosal lesion. The rat model of CAG with colonic mucosal lesion was induced by free-drinking 20 mmol/L sodium deoxycholate to simulate bile reflux and 2% cold sodium salicylate for 12 weeks. In comparison to the control group, the model rats had increased abundances of Bacteroidetes and Firmicutes but had decreased abundances of Proteobacteria and Fusobacterium. Several gut bacteria with bile acids transformation ability were enriched in the model group, such as Blautia, Phascolarctobacter, and Enterococcus. The cytotoxic deoxycholic acid and lithocholic acid were significantly increased in the model group. Transcriptome analysis of colonic tissues presented that the down-regulated genes enriched in T cell receptor signaling pathway, antigen processing and presentation, Th17 cell differentiation, Th1 and Th2 cell differentiation, and intestinal immune network for IgA production in the model group. These results suggest that bile reflux-inducing CAG with colonic mucosal lesion accompanied by gut dysbacteriosis, mucosal immunocompromise, and increased gene expressions related to repair of intestinal mucosal injury.

Differences of RUNX2 gene promoter methylation and transcription level in ankylosing spondylitis

BACKGROUND AND OBJECTIVE

Ankylosing spondylitis is a refractory immune disease that seriously affects the life and work of patients. Epigenetic modifications, especially DNA methylation, have become a research hotspot in complex diseases. We aim to explore the changes in runt-related transcription factor 2 (RUNX2) gene promoter methylation and transcription level in AS.

METHOD

We detected the RUNX2 gene promoter methylation in 83 AS patients and 83 healthy controls (HCs), then inspected the mRNA difference of RUNX2 between 30 AS patients and 30 HCs by the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR).

RESULTS

The RUNX2 gene promoter was hypomethylated in AS patients compared to HCs (p < .001). The research involved 4 CpG regions and 74 CpG sites of RUNX2, of which CpG-2, CpG-4 regions, and 18 CpG sites have been differentially methylated. The CpG-4 island methylation was negatively correlated with C-reactive protein (p < .05) in AS patients. In the qRT-PCR validation phase, the mRNA level of RUNX2 in AS patients was significantly higher than HCs (p < .05), and in AS patients who were treated with biologics, the methylation level of CpG-2 island showed a negative correlation to mRNA (p < .05). ROC results indicated that RUNX2 methylation and its transcription level have good potential to distinguish AS patients from HCs.

CONCLUSION

The RUNX2 gene promoter was hypomethylated in AS patients. Meanwhile, the qRT-PCR verified the up-regulated expression on the transcription level, suggesting the abnormal methylation of RUNX2 contributes to the pathogenesis of AS.

DNA methylation and transcriptome signatures of the PDCD1 gene in ankylosing spondylitis

Ankylosing spondylitis (AS) is an autoimmune-related inflammatory arthritis. The association between the DNA methylation and mRNA expression of PDCD1 gene with the susceptibility to AS remains unclear. In this case-control study, the methylation level of PDCD1 promoter was detected in 80 AS patients and 80 healthy controls by MethylTarget method. The transcriptional level of PDCD1 gene was measured in 47 AS patients and 47 healthy controls by real-time quantitative PCR. Finally, 17 methylation sites mapped to one CpG island were detected. Compared to healthy controls, the promoter of PDCD1 was hypermethylated (p < 0.001) and the mRNA expression was downregulated (p < 0.001) in AS patients. Significantly negative correlation was identified between the DNA methylation and mRNA expression of PDCD1 gene (r_s = -0.470, p < 0.001). The receiver operating characteristic (ROC) results showed that PDCD1 island had a sensitivity of 61.3% and a specificity of 82.5%, and PDCD1 mRNA had a sensitivity of 87.2% and a specificity of 89.0%. The methylation level of PDCD1 was positively correlated with the ESR, CRP and ASDAS of AS, and was not affected by HLA-B27 status, gender or medicine intake.

DNA methylation and transcription of the FOXO3a gene are associated with ankylosing spondylitis

To explore the association between methylation level and transcript level of Forkhead box O3a (FOXO3a) gene with ankylosing spondylitis (AS) susceptibility. Methylation levels of the FOXO3a promoter were measured in 84 AS patients and 83 healthy controls. A total of 77 patients and 66 healthy subjects were included in subsequent mRNA level testing. DNA methylation levels of 107 CpG sites on 6 CpG islands in the FOXO3a gene were investigated. This study indicated that CpG-4 and CpG-5 islands were markedly hypomethylated in AS patients. The methylation level of CpG-4 island in AS patients was negatively correlated with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and Ankylosing Spondylitis Disease Activity Score (ASDAS). Moreover, FOXO3a mRNA levels were significantly decreased in AS patients and were obviously negatively correlated with the methylation levels of CpG-2 and CpG-5 islands in AS patients without treatment. The sensitivity and specificity of differential methylated CpG sites of FOXO3a were 74.7 and 85.4%, respectively. Besides, FOXO3a mRNA had a sensitivity of 80.0% and a specificity of 68.8%. DNA methylation and transcription of FOXO3a might be related to AS susceptibility and play a crucial role in the diagnosis of AS, but many open questions remain.