HIPK3 hypomethylation as a potential epigenetic biomarker in rheumatic immune diseases with emphasis on rheumatoid arthritis.

Objectives: This study aimed to explore the potential of HIPK3 DNA methylation as a biomarker for rheumatoid arthritis (RA) by examining its methylation levels in various rheumatic immune diseases and analyzing its correlation with clinical indicators.

Methods: We recruited 368 participants, including patients with RA, ankylosing spondylitis (AS), GOUT, psoriatic arthritis (PSA), sjogren's syndrome (SS), systemic lupus erythematosus (SLE), dermatomyositis (DM), and healthy controls (HC), and MethylTargetTM targeted region methylation sequencing technology was employed to analyze the DNA methylation levels of HIPK3 (cg15692052). We analyzed the HIPK3 methylation levels and correlated them with common clinical indicators. Transcriptome data from the GEO dataset (GSE93272) were also analyzed to assess HIPK3 mRNA expression levels in RA patients. Statistical analyses included Spearman correlation, One-Way ANOVA, Kruskal-Wallis tests, and ROC curve analysis.

Results: HIPK3 methylation levels were significantly lower in the RA, SLE, and DM groups compared to the HC group (P < 0.05). RA subgroups based on RF and CCP statuses also showed lower HIPK3 methylation levels compared to the HC group (P < 0.05). Analysis of the GEO dataset revealed significantly elevated HIPK3 mRNA expression in RA patients (P < 0.05). A negative correlation was found between HIPK3 methylation levels and ESR (r = -0.14, P = 7.1e-3), CRP (r = -0.25, P = 4.1e-7), RF (r = -0.18, P = 5.2e-4), and DAS28-CRP (r = -0.12, P = 0.04) in the RA group. ROC analysis indicated that HIPK3 methylation levels had high diagnostic value for RA (AUC = 0.742), SLE (AUC = 0.701), and DM (AUC = 0.948), especially in distinguishing seronegative RA (AUC = 0.612, 0.747, 0.836) and differentiating RA from AS (AUC = 0.788).

Conclusions: The study suggests that HIPK3 hypomethylation in peripheral blood is associated with RA and correlated with inflammatory markers, such as CRP. HIPK3 methylation levels have potential as a novel biomarker for RA diagnosis and predicting inflammation trends, showing particular promise in differentiating RA from other types of arthritis. Key Points • MethylTargetTM targeted region methylation sequencing technology was employed to analyze the DNA methylation levels of HIPK3 (cg15692052). • HIPK3 methylation levels have potential as a novel biomarker for RA diagnosis and predicting inflammation trends.