Transcriptomic characterization of classical monocytes highlights the involvement of immuno-inflammation in bone erosion in Rheumatoid Arthritis

Abstract

IntroductionEvidence-based data suggest that under inflammatory conditions, classical monocytes are the main source of osteoclasts and might be involved in bone erosion pathophysiology. Here, we analyze the transcriptomic profile of classical monocytes in erosive and non-erosive rheumatoid arthritis patients in order to better understand their contribution to bone erosion.MethodsThirty-nine premenopausal RA patients were consecutively enrolled and divided into two groups based on the presence of bone erosions on hand joints. Classical monocytes were isolated from peripheral blood through negative selection, and RNA-seq was performed using a poly-A enrichment kit and Illumina® platform. Classical monocytes transcriptome from healthy age-matched women were also included to identify differentially expressed genes (DEGs). Therefore, gene sets analysis was performed to identify the enriched biological pathways.ResultsRNA-seq analysis resulted in the identification of 1,140 DEGs of which 89 were up-regulated and 1,051 down-regulated in RA patients with bone erosion compared to those without bone erosions. Among up-regulated genes, there was a highlighted expression of IL18RAP and KLF14 related to the production of pro-inflammatory cytokines, innate and adaptive immune response. Genes related to collagen metabolism (LARP6) and bone formation process (PAPPA) were down-regulated in RA patients with erosions. Enriched pathways in patients with erosions were associated with greater activation of immune activation, and inflammation. Interestingly, pathways associated with osteoblast differentiation and regulation of Wnt signaling were less activated in RA patients with erosions.ConclusionThese findings suggest that alterations in expression of monocyte genes related to the inflammatory process and impairment of bone formation might have an important role in the pathophysiology of bone erosions in RA patients.

Transcriptomic signatures of classical monocytes reveal pro-inflammatory modules and heterogeneity in polyarticular juvenile idiopathic arthritis

“…Patients were excluded if they had metabolic bone disease (e.g., rickets, primary hypoparathyroidism, osteomalacia, and Paget’s disease), ii) use of any medication interfering with bone metabolism (e.g., prednisone doses higher than 7.5 mg/day, bisphosphonates, and bone-targeted monoclonal antibodies), iii) other autoimmune disease, or iv) pregnancy or lactation. Premenopausal status was assessed through a self-reported information as previously described ( 10 ). In addition, clinical and transcriptomics data of 17 age- and body mass index-matched healthy subjects were extracted from our previously published database ( 10 ).…”

“…Premenopausal status was assessed through a self-reported information as previously described ( 10 ). In addition, clinical and transcriptomics data of 17 age- and body mass index-matched healthy subjects were extracted from our previously published database ( 10 ). The inclusion and exclusion criteria were carefully delineated for the healthy controls group.…”

“…Only female participants without osteometabolic diseases were eligible for inclusion in the study. Additionally, individuals with any autoimmune and/or non-communicable chronic diseases, those who were pregnant, had bone metabolism disorders (like hyperparathyroidism, Paget’s disease, and bone dysplasia), had neoplasms, or were using medications that could disrupt bone metabolism were excluded ( 10 ). The study was approved by the local Ethics Committee from Sao Paulo University-CAPPesq (#51178115.1.0000.0068).…”

“…Demographic and clinical data were obtained through interviews and electronic medical records, including age, weight, height, race, coexisting chronic diseases, time from pJIA onset, and treatment data ( 1 , 10 ). Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), and anti-cyclic citrullinated peptide (anti-CCP) antibodies were measured using standard automated methods.…”

“…However, the contribution of specific blood cell types to this heterogeneity remains unclear. Recently, using RNA sequencing, we demonstrated that classical monocytes isolated from rheumatoid arthritis (RA) patients are involved with the excessive activation of immuno-inflammatory pathways and bone erosion observed in this disease ( 10 ). Nevertheless, the role of the subtype of classical monocyte in pJIA is still uncertain.…”