MicroRNA Expression Differences in Blood-Derived CD19+ B Cells of Methotrexate Treated Rheumatoid Arthritis Patients.

Fatima Heinicke,Benedicte A Lie,Siri T Flåm,Siri Lillegraven,Anna-Birgitte Aga,Maria D Mjaavatten,Ellen S Norli,Xiangfu Zhong,Simon Rayner,Johannes Breidenbach,Marthe T Mæhlen,Magnus Leithaug,Manuela Zucknick,Espen A Haavardsholm

doi:10.3389/fimmu.2021.663736

Abstract

Rheumatoid arthritis (RA) is a complex disease with a wide range of underlying susceptibility factors. Recently, dysregulation of microRNAs (miRNAs) in RA have been reported in several immune cell types from blood. However, B cells have not been studied in detail yet. Given the autoimmune nature of RA with the presence of autoantibodies, CD19+ B cells are a key cell type in RA pathogenesis and alterations in CD19+ B cell subpopulations have been observed in patient blood. Therefore, we aimed to reveal the global miRNA repertoire and to analyze miRNA expression profile differences in homogenous RA patient phenotypes in blood-derived CD19+ B cells. Small RNA sequencing was performed on CD19+ B cells of newly diagnosed untreated RA patients (n=10), successfully methotrexate (MTX) treated RA patients in remission (MTX treated RA patients, n=18) and healthy controls (n=9). The majority of miRNAs was detected across all phenotypes. However, significant expression differences between MTX treated RA patients and controls were observed for 27 miRNAs, while no significant differences were seen between the newly diagnosed patients and controls. Several of the differentially expressed miRNAs were previously found to be dysregulated in RA including miR-223-3p, miR-486-3p and miR-23a-3p. MiRNA target enrichment analysis, using the differentially expressed miRNAs and miRNA-target interactions from miRTarBase as input, revealed enriched target genes known to play important roles in B cell activation, differentiation and B cell receptor signaling, such as STAT3, PRDM1 and PTEN. Interestingly, many of those genes showed a high degree of correlated expression in CD19+ B cells in contrast to other immune cell types. Our results suggest important regulatory functions of miRNAs in blood-derived CD19+ B cells of MTX treated RA patients and motivate for future studies investigating the interactive mechanisms between miRNA and gene targets, as well as the possible predictive power of miRNAs for RA treatment response.

Highlights

Rheumatoid arthritis (RA) is a systemic autoimmune disorder associated with chronic inflammation, mainly in the joints, causing bone erosion and loss of mobility if not treated effectively at an early disease stage
Because data on global blood-derived CD19+ B cell miRNA expression profiles in RA patients have not been previously published, we focused on studies performed on healthy controls [29,30,31,32,33]
No significant (p>0.05) differences were seen in age, gender or smoking status between the newly-diagnosed or MTX treated RA patients compared to healthy controls

Summary

Introduction

Rheumatoid arthritis (RA) is a systemic autoimmune disorder associated with chronic inflammation, mainly in the joints, causing bone erosion and loss of mobility if not treated effectively at an early disease stage. A majority of RA patients do not respond toward MTX monotherapy [2,3,4], and no biomarker exists to reliably predict the success or failure of MTX treatment for a given patient. Even though the precise pathogenesis of RA is unknown, lymphocytes, such as B cells, have been reported to play a major role. Auto-antibodies can be detected in serum of RA patients up to 10 years prior to diagnosis [5, 6]. B cells are major producers of chemokines and cytokines and can thereby influence RA pathogenesis [7]. Disturbances in CD19+ B cell subpopulations have been observed in peripheral blood of RA patients, indicating breaks in tolerance within B cell development potentially leading to self-reactive B cells [8, 9]

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