Evaluation of bone erosion in rheumatoid arthritis patients by high-resolution peripheral quantitative computed tomography scans: Comparison between two semi-automated programs in a three-dimensional setting

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

Introduction

Evidence-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.

Methods

Thirty-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.

Results

RNA-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.

Conclusion

These 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.

Lower hand grip in rheumatoid arthritis patients is associated with low finite element analysis using high resolution peripheral quantitative computed tomography scan of the 2nd metacarpophalangeal joint

AIM

To evaluate hand function by hand grip test in rheumatoid arthritis (RA) patients, and its association with bone erosions and the estimated bone strength (finite element - FE analysis) through the analysis of the 2nd metacarpal head of the dominant hand using high resolution peripheral quantitative computed tomography (HR-pQCT).

METHOD

Eighty-two female RA patients between 18-50 years old were selected. Demographic data, Health Questionnaire Assessment Disability Index (HAQ), Disease Activity Score of 28 joints (DAS)-28, simplified disease activity index (SDAI) and the hand grip test were set. The HR-pQCT scans of 2nd metacarpophalangeal joints of the dominant hand of all patients were performed according to SPECTRA group protocols. The images were used to assess bone erosions and FE analysis. The hand grip test was categorized in 2 groups and separately compared (< 18 vs ≥18 kgf). A logistic regression was performed using hand grip test <18 kgf as a dependent variable.

RESULTS

A significant difference was found between the 2 groups regarding HAQ, inflammatory markers (erythrocyte sedimentation rate, C-reactive protein), DAS-28, SDAI, total volume of erosion and bone strength parameter (FE analysis - Failure Load [F.Load]). The logistic regression analysis showed that the risk factors associated with hand grip test <18 kgf were higher SDAI (odds ratio [OR] 0.912; 95% CI 0.837-0.993) and lower values of bone strength parameter (F.Load) (OR 1.007; 95% CI 1.002-1.012).

CONCLUSION

Lower values of hand grip test were associated with higher disease activity score-SDAI and lower bone strength of 2nd metacarpal bone head of the dominant hand evaluated here through a FE analysis using HR-pQCT scan.

Bone erosions and osteophytes in premenopausal women with long-standing rheumatoid arthritis: association with systemic bone involvement by HR-Pqct

OBJECTIVE

To evaluate premenopausal women with long-standing RA and to explore the relationship between parameters of systemic and localized bone involvement.

METHODS

Eighty consecutive RA premenopausal women were evaluated. Volumetric bone mineral density (vBMD), microarchitecture and finite element analysis were performed using high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius (DR) and tibia (DT) and compared with parameters from 160 female healthy controls matched by age and body mass index. Localized bone involvement was also analyzed using HR-pQCT in the metacarpophalangeal and proximal interphalangeal joints to identify erosions and osteophytes.

RESULTS

The mean age of RA patients was 39.4±6.7years and disease duration 9.8±5.3years. RA patients had impaired trabecular, cortical and bone strength parameters, at DR and DT, compared with healthy controls (p<0.05). Bone erosions and osteophytes were found in 75% and 41.3% of patients, respectively. Comparing patients with and without erosions, at DR and DT, a lower cortical vBMD (DR: 980±72 versus 1021±47mgHA/cm³ , p=0.03; DT:979±47 versus 1003±34 mgHA/cm³ , p=0.04) and higher cortical porosity (DR:2.8±2.5 versus 1.8±1.6%, p=0.04; and DT:3.7±1.6 versus 2.7±1.6%, p=0.01) were observed in patients with erosions. At the DR, osteophyte volume was positively correlated with trabecular vBMD (0.392, p=0.02), trabecular number (0.381, p=0.03) and stiffness (0.411, p=0.02), and negatively with trabecular separation (-0.364, p=0.04).

CONCLUSION

Our findings showed that premenopausal women with long-standing RA had systemic bone fragility at peripheral sites. Moreover, erosions were associated mainly with cortical bone fragility at the DR and DT, and osteophytes correlated with repair of trabecular bone at the radius.