Syndecans, Exostosins and Sulfotransferases as Potential Synovial Inflammation Moderators in Patients with Hip Osteoarthritis

The gradual deterioration of articular cartilage was thought to be the central event in osteoarthritis (OA), but recent studies demonstrated the importance of low-grade synovitis in the progression of OA. The Syndecan (SDC) family of membrane proteoglycans is known to be involved in the regulation of inflammation, but there is limited evidence considering the role of syndecans in OA synovitis. Our study aimed to investigate the hip OA synovial membrane expression patterns of SDC1, SDC2 and SDC4, as well as exostosins and sulfotransferases (enzymes involved in the polymerisation and modification of syndecans' heparan sulphate chains). Synovial membrane samples of patients with OA (24) were divided into two groups according to their Krenn synovitis score severity. The immunohistochemical expressions of SDC1, SDC2, SDC4, EXT1, EXT2, NDST1 and NDST2 in synovial intima and subintima were then analysed and compared with the control group (patients with femoral neck fracture). According to our study, the immunoexpression of SDC1, NDST1 and EXT2 is significantly increased in the intimal cells of OA synovial membrane in patients with lower histological synovitis scores and SDC4 in patients with higher synovitis scores, in comparison with non-OA controls. The difference in the expression of SDC2 among the OA and non-OA groups was insignificant. SDC1, SDC4, NDST1 and EXT2 seem to be involved as inflammation moderators in low-grade OA synovitis and, therefore, should be further investigated as potential markers of disease progression and therapeutic goals.

Identification of CD64 as a marker for the destructive potential of synovitis in osteoarthritis

OBJECTIVES

OA is characterized by cartilage degeneration and persistent pain. The majority of OA patients present with synovitis, which is associated with increased cartilage damage. Activated synovial macrophages are key contributors to joint destruction. Therefore, a marker that reflects the activation of these cells could be a valuable tool to characterize the destructive potential of synovitis and benefit monitoring of OA. Here, we aimed to investigate the use of CD64 (FcγRI) as a marker to characterize the damaging potential of synovitis in OA.

METHODS

Synovial biopsies were obtained from end-stage OA patients that underwent joint replacement surgery. CD64 protein expression and localization was evaluated using immunohistochemistry and immunofluorescence and quantified using flow cytometry. qPCR was performed to measure the expression of FCGR1 and OA-related genes in synovial biopsies, and in primary chondrocytes and primary fibroblasts stimulated with OA conditioned medium (OAS-CM).

RESULTS

Our data exposed a wide range of CD64 expression in OA synovium and showed positive correlations between FCGR1 and S100A8, S100A9, IL1B, IL6 and MMP1/2/3/9/13 expression. CD64 protein correlated with MMP1, MMP3, MMP9, MMP13 and S100A9. Furthermore, we observed that synovial CD64 protein levels in source tissue for OAS-CM significantly associated with the OAS-CM-induced expression of MMP1, MMP3 and especially ADAMTS4 in cultured fibroblasts, but not chondrocytes.

CONCLUSION

Together, these results indicate that synovial CD64 expression is associated with the expression of proteolytic enzymes and inflammatory markers related to structural damage in OA. CD64 therefore holds promise as marker to characterize the damaging potential of synovitis.

The relationship of ALPK1, hyaluronic acid and M1 macrophage polarization in the temporomandibular joint synovitis

M1 macrophage polarization and synovitis play an important role in the pathogenesis of temporomandibular joint osteoarthritis (TMJOA). Reduced molecular weight of hyaluronic acid (HA) in synovial fluid of patients with TMJOA. In addition, high molecular weight hyaluronic acid (HMW-HA) is often used clinically to treat TMJ inflammation. As a pattern recognition receptor of the cytoplasm, ALPK1 was found to be pro-inflammatory in a variety of diseases. However, the relationship of ALPK1, HA and M1 macrophage polarization in TMJ synovitis remains unclear. We aimed to investigate the role of ALPK1 and HA in macrophage polarization and TMJ synovitis and the underlying mechanisms. The results demonstrated that ALPK1 was highly upregulated in the synovial macrophages in the inflamed TMJ synovium of patients. Low molecular weight hyaluronic acid (LMW-HA) promoted the expression of ALPK1 and M1 macrophage-associated genes. Besides, rhALPK1 promoted the expression of M1 macrophage-associated factors and the nuclear translocation of PKM2. Furthermore, ALPK1 knockout mice exhibited limited infiltration of macrophages and decreased expression levels of M1 macrophage-associated genes in CFA-induced TMJ synovitis. While HMW-HA inhibited the expression of ALPK1 and M1 macrophage polarization. Our results elucidated that ALPK1 promoted TMJ synovitis by promoting nuclear PKM2-mediated M1 macrophage polarization, whereas HMW-HA inhibited the expression of ALPK1 as well as M1 macrophage polarization.

Inflammatory Fibroblast-Like Synoviocyte-Derived Exosomes Aggravate Osteoarthritis via Enhancing Macrophage Glycolysis

The severity of osteoarthritis (OA) and cartilage degeneration is highly associated with synovial inflammation. Although recent investigations have revealed a dysregulated crosstalk between fibroblast-like synoviocytes (FLSs) and macrophages in the pathogenesis of synovitis, limited knowledge is available regarding the involvement of exosomes. Here, increased exosome secretion is observed in FLSs from OA patients. Notably, internalization of inflammatory FLS-derived exosomes (inf-exo) can enhance the M1 polarization of macrophages, which further induces an OA-like phenotype in co-cultured chondrocytes. Intra-articular injection of inf-exo induces synovitis and exacerbates OA progression in murine models. In addition, it is demonstrated that inf-exo stimulation triggers the activation of glycolysis. Inhibition of glycolysis using 2-DG successfully attenuates excessive M1 polarization triggered by inf-exo. Mechanistically, HIF1A is identified as the determinant transcription factor, inhibition of which, both pharmacologically or genetically, relieves macrophage inflammation triggered by inf-exo-induced hyperglycolysis. Furthermore, in vivo administration of an HIF1A inhibitor alleviates experimental OA. The results provide novel insights into the involvement of FLS-derived exosomes in OA pathogenesis, suggesting that inf-exo-induced macrophage dysfunction represents an attractive target for OA therapy.

OA susceptibility in mice is partially mediated by the gut microbiome, is transferrable via microbiome transplantation and is associated with immunophenotype changes

OBJECTIVES

The Murphy Roths Large (MRL)/MpJ 'superhealer' mouse strain is protected from post-traumatic osteoarthritis (OA), although no studies have evaluated the microbiome in the context of this protection. This study characterised microbiome differences between MRL and wild-type mice, evaluated microbiome transplantation and OA and investigated microbiome-associated immunophenotypes.

METHODS

Cecal material from mixed sex C57BL6/J (B6) or female MRL/MpJ (MRL) was transplanted into B6 and MRL mice, then OA was induced by disruption of the medial meniscus surgery (DMM). In other experiments, transplantation was performed after DMM and transplantation was performed into germ-free mice. Transplanted mice were bred through F2. OARSI, synovitis and osteophyte scores were determined blindly 8 weeks after DMM. 16S microbiome sequencing was performed and metagenomic function was imputed. Immunophenotypes were determined using mass cytometry.

RESULTS

MRL-into-B6 transplant prior to DMM showed reduced OA histopathology (OARSI score 70% lower transplant vs B6 control), synovitis (60% reduction) and osteophyte scores (30% reduction) 8 weeks after DMM. When performed 48 hours after DMM, MRL-into-B6 transplant improved OA outcomes but not when performed 1-2 weeks after DMM. Protection was seen in F1 (60% reduction) and F2 progeny (30% reduction). Several cecal microbiome clades were correlated with either better (eg, Lactobacillus, R=-0.32, p=0.02) or worse (eg, Rikenellaceae, R=0.43, p=0.001) OA outcomes. Baseline immunophenotypes associated with MRL-into-B6 transplants and MRL included reduced double-negative T cells and increased CD25+CD4+ T cells.

CONCLUSION

The gut microbiome is responsible in part for OA protection in MRL mice and is transferrable by microbiome transplantation. Transplantation induces resting systemic immunophenotyping changes that correlate with OA protection.

Three-dimensional ultrasound to investigate synovitis in first carpometacarpal osteoarthritis: A feasibility study

BACKGROUND

Synovitis is one of the defining characteristics of osteoarthritis (OA) in the carpometacarpal (CMC1) joint of the thumb. Quantitative characterization of synovial volume is important for furthering our understanding of CMC1 OA disease progression, treatment response, and monitoring strategies. In previous studies, three-dimensional ultrasound (3-D US) has demonstrated the feasibility of being a point-of-care system for monitoring knee OA. However, 3-D US has not been tested on the smaller joints of the hand, which presents unique physiological and imaging challenges.

PURPOSE

To develop and validate a novel application of 3-D US to monitor soft-tissue characteristics of OA in a CMC1 OA patient population compared to the current gold standard, magnetic resonance imaging (MRI).

METHODS

A motorized submerged transducer moving assembly was designed for this device specifically for imaging the joints of the hands and wrist. The device used a linear 3-D scanning approach, where a 14L5 2-D transducer was translated over the region of interest. Two imaging phantoms were used to test the linear and volumetric measurement accuracy of the 3-D US device. To evaluate the accuracy of the reconstructed 3-D US geometry, a multilayer monofilament string-grid phantom (10 mm square grid) was scanned. To validate the volumetric measurement capabilities of the system, a simulated synovial tissue phantom with an embedded synovial effusion was fabricated and imaged. Ten CMC1 OA patients were imaged by our 3-D US and a 3.0 T MRI system to compare synovial volumes. The synovial volumes were manually segmented by two raters on the 2D slices of the 3D US reconstruction and MR images, to assess the accuracy and precision of the device for determining synovial tissue volumes. The Standard Error of Measurement and Minimal Detectable Change was used to assess the precision and sensitivity of the volume measurements. Paired sample t-tests were used to assess statistical significance. Additionally, rater reliability was assessed using Intra-Class Correlation (ICC) coefficients.

RESULTS

The largest percent difference observed between the known physical volume of synovial extrusion in the phantom and the volume measured by our 3D US was 1.1% (p-value = 0.03). The mean volume difference between the 3-D US and the gold standard MRI was 1.78% (p-value = 0.48). The 3-D US synovial tissue volume measurements had a Standard Error Measurement (SEm ) of 11.21 mm3 and a Minimal Detectible Change (MDC) of 31.06 mm3 , while the MRI synovial tissue volume measurements had an SEM of 16.82 mm3 and an MDC of 46.63 mm3 . Excellent inter- and intra-rater reliability (ICCs = 0.94-0.99) observed across all imaging modalities and raters.

CONCLUSION

Our results indicate the feasibility of applying 3-D US technology to provide accurate and precise CMC1 synovial tissue volume measurements, similar to MRI volume measurements. Lower MDC and SEm values for 3-D US volume measurements indicate that it is a precise measurement tool to assess synovial volume and that it is sensitive to variation between volume segmentations. The application of this imaging technique to monitor OA pathogenesis and treatment response over time at the patient's bedside should be thoroughly investigated in future studies.

Comparative analysis of late-stage rheumatoid arthritis and osteoarthritis reveals shared histopathological features

OBJECTIVES

Osteoarthritis (OA) is a debilitating and heterogeneous condition, characterized by various levels of articular cartilage degradation, osteophytes formation, and synovial inflammation. Multiple evidences suggest that synovitis may appear early in the disease development and correlates with disease severity and pain, therefore representing a relevant therapeutic target. In a typical synovitis-driven joint disease, namely rheumatoid arthritis (RA), several pathotypes have been described by our group and associated with clinical phenotypes, disease progression, and response to therapy. However, whether these pathotypes can be also observed in the OA synovium is currently unknown.

METHODS

Here, using histological approaches combined with semi-quantitative scoring and quantitative digital image analyses, we comparatively characterize the immune cell infiltration in a large cohort of OA and RA synovial tissue samples collected at the time of total joint replacement.

RESULTS

We demonstrate that OA synovium can be categorized also into three pathotypes and characterized by disease- and stage-specific features. Moreover, we revealed that pathotypes specifically reflect distinct levels of peripheral inflammation.

CONCLUSIONS

In this study, we provide a novel and relevant pathological classification of OA synovial inflammation. Further studies investigating synovial molecular pathology in OA may contribute to the development of disease-modifying therapies.

Neuropathic-like pain in knee osteoarthritis: exploring differences in knee loading and inflammation. A cross-sectional study

BACKGROUND

A subgroup of patients with knee osteoarthritis (OA) reports symptoms attributable to a neuropathic cause. Little to no attention has been invested on investigating differences in knee loading and inflammation in these patients.

AIM

To explore differences in inflammation and knee loading in patients with knee OA categorized based on the presence of neuropathic-like pain.

DESIGN

Cross-sectional study.

SETTING

Ghent University Hospital, Ghent, Belgium.

POPULATION

Knee OA patients.

METHODS

cross-sectional analysis of data from 96 patients (mean age 64.18±7.11 years) with primary knee OA participating in a randomized controlled trial. Participants were divided into three groups (unlikely, possible and indication of neuropathic-like pain) according to the modified painDETECT questionnaire (mPDQ). Data on demographics, symptoms and physical function were obtained by questionnaires. Effusion/synovitis and bone marrow lesions (BMLs) were measured using magnetic resonance imaging. Knee loading variables (knee adduction moment [KAM], KAM impulse, and knee flexion moment [KFM]) were assessed by 3D-motion analysis. One-way analysis of covariance (ANCOVA), Chi-square test and curve analyses were used to analyze continuous, categorical and loading variables respectively. Multinomial logistic regression was used to identify predictors for neuropathic-like pain.

RESULTS

Patients with indication of neuropathic-like pain exhibited higher KAM impulse compared to those with no indication of neuropathic-like pain (standard mean difference (SMD): -0.036 Nm normalized to body weight and height per second, 95% CI: -0.071, -0.001) along with greater pain intensity (SMD: 3.87 units, 95% CI: 1.90, 5.84), stiffness (SMD: 1.34 units, 95% CI: 0.19, 2.48) and worse physical function (SMD: 13.98 units 95% CI: 7.52, 20.44). Curve analysis showed no significant differences in KFM and KAM between groups. Effusion/synovitis and BMLs did not differ significantly between groups. The best predictors for indication of neuropathic-like pain were KAM impulse, Hoffa and sex.

CONCLUSIONS

Knee OA patients with indication of neuropathic-like pain exhibited higher dynamic medial loading, greater pain severity and worse physical function, while inflammatory markers were not significantly different across mPDQ groups. Future longitudinal studies are warranted to strengthen the evidence and establish mechanisms to explain associations between neuropathic-like pain and knee loading.

CLINICAL REHABILITATION IMPACT

Knee loading is a modifiable factor and patients with neuropathic-like pain may benefit from offloading interventions.

Sex-Linked Discrepancies in C57BL6/J Mouse Osteoarthritis are Associated With the Gut Microbiome and are Transferrable by Microbiome Transplantation

OBJECTIVE

Females have reduced osteoarthritis (OA) in surgical models. The objective of the current study was to evaluate a sex-linked gut microbiome in the pathogenesis of OA.

METHODS

We induced OA via destabilization of the medial meniscus surgery in adult male and female C57BL6/J mice with and without opposite-sex microbiome transplantation. Eight weeks later, animals were euthanized, and OA severity, synovitis, and osteophyte scores were determined. Serum lipopolysaccharide was measured chromogenically, and serum cytokines were quantified via multiplex immunoassay. Cecal microbiome profiles were generated using 16S deep sequencing.

RESULTS

Males had worse OA histology (3.5x, P = 6 × 10-7 ), synovitis (2.4x, P = 5 × 10-4 ), and osteophyte scores (3.7x, P = 3 × 10-4 ) than females. Male-into-female transplantation worsened all outcomes (histology 1.8x, P = 0.02; synovitis 2.0x, P = 3 × 10-5 ; osteophyte 2.1x, P = 0.01) compared to females, whereas female-into-male transplantation improved all outcomes except for synovitis (histology 0.53x, P = 2 × 10-4 ; osteophyte 0.28x, P = 5 × 10-4 ) compared to males. In the gut microbiome analysis, 44 clades were different in at least one group comparison; 5 clades were correlated with the Osteoarthritis Research Society International score (Lactobacillus R = -0.40, Aldercreutzia R = -0.40, rc4_4 R = -0.55, Sutterella R = -0.37, and Clostridiales R = 0.36). In the cytokine analysis, 10 analytes were different in at least one group comparison; 3 were different in two groups (female and female-into-male transplants vs male comparisons, all reduced in female and female-into-male transplants), including interleukin-12 (0.66x, P = 0.02; 0.66x, P = 0.02, respectively), eotaxin (0.74x, P = 5 × 10-6 ; 0.57x, P = 0.03), and tumor necrosis factor ⍺ (0.49x, P = 0.03; 0.52x, P = 0.009).

CONCLUSION

Sex-linked differences in the mouse gut microbiome are associated with OA outcomes, are reversible by opposite-sex microbiome transplantation, and are associated with serum cytokine changes.

High-grade synovitis associates with clinical markers and response to therapy in chronic inflammatory arthritis: post hoc analysis of a synovial biomarkers prospective cohort study

Background

Inflammatory arthritis (IAs), such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA), are characterized by the presence of chronic synovitis. The Krenn's synovitis score (KSS), a simple tool detectable by haematoxylin/eosin staining of synovial biopsy samples, allows the discrimination between high-grade and low-grade synovitis. The aim of this study was to identify the clinical associations of KSS and to evaluate the relationship between high-grade synovitis and treatment response in IA patients.

Methods

Clinical, laboratory and ultrasound data were retrieved from RA and PsA patients recruited in the prospective MATRIX cohort study. Inclusion criteria were age≥18 years, RA or PsA diagnosis, and presence of active disease with eligibility to start/modify therapy. Patients underwent ultrasound-guided synovial biopsy of one of the most involved joints before starting/modifying treatment according to treat-to-target strategy. The samples were analysed by an expert pathologist for KSS calculation. Univariable and multivariable logistic regression analyses were performed to evaluate the relationship between KSS and baseline variables. The association between KSS and treatment response at 24 weeks of follow-up was investigated in univariable logistic regression analysis.

Results

53 patients, 34 RA and 19 PsA, completed 24 weeks of follow-up after synovial biopsy. Patients were either treatment naïve (N=6, 11%), csDMARDs-experienced (N=46, 87%) or b/tsDMARDs-experienced (N=20, 38%). Median KSS was 6.00 (Q1-Q3 4.00-7.00) in RA and 4.00 (3.00-6.00) in PsA (p=0.040), and inflammatory infiltrates score was significantly higher in RA than in PsA patients (median 3.00 vs 2.00, p=0.021). In multivariable analysis, synovial effusion in the biopsied joint (OR 9.26, 95%CI 2.12-53.91) and erythrocyte sedimentation rate (ESR) (OR 1.04, 95%CI 1.01-1.08) associated with high KSS. High-grade synovitis significantly associated with a higher probability of achieving DAS28 remission, ACR20/50 response, and Boolean2.0 remission, independently from diagnosis.

Conclusion

Several markers of pro-inflammatory pathways associated with the presence of high-grade synovitis, and patients with higher KSS shared a higher probability of treatment targets achievement in the follow up. The integration of a simple and feasible tool like KSS in the clinical and prognostic stratification of patients with IA might help in intercepting patients with a disease more prone to respond to available treatment paradigms.

T2 Black Synovitis in Musculoskeletal MRI: Disease Spectrum and Imaging Characteristics of Joint Diseases

The synovium may be affected by a wide spectrum of disorders, including inflammatory, infectious, degenerative, traumatic, hemorrhagic, and tumorous conditions. Magnetic resonance imaging (MRI) is a valuable imaging modality to characterize synovial disorders. Most abnormal lesions appear as areas of nonspecific high signal intensity on T2-weighted images (T2-WI) due to high water content or increased perfusion. However, T2 hypointensity can be attributed to blood components of varying ages, calcification, inorganic crystals, fibrosis, caseous necrosis and/or amyloid deposition. Hypointense lesions on T2-WI are infrequent and additional clinical and imaging characteristics can help to limit the list of differential diagnoses, which may include tenosynovial giant cell tumor, synovial chondromatosis, rheumatoid arthritis, tuberculous arthritis, chronic tophaceous gout, amyloid arthropathy, synovial hemangioma, lipoma arborescens and hemosiderotic synovitis. Recently, susceptibility weighted imaging has been developed and may contribute to more accurate diagnosis for deoxygenated blood and calcium. We review the MRI features of hypointense synovial lesions on MRI and emphasize the characteristic findings that suggest a correct diagnosis.

Value of Magnetic Resonance T1 Mapping in Evaluating the Early Response to Treatment for Rheumatoid Arthritis

BACKGROUND

Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS) is usually used for the semi-quantitative evaluation of joint changes in Rheumatoid Arthritis (RA). However, this method cannot evaluate early changes in bone marrow edema (BME).

OBJECTIVE

To determine whether T1 mapping of wrist BME predicts early treatment response in RA.

METHODS

This study prospectively enrolled 48 RA patients administered oral anti-rheumatic drugs. MRI of the most severely affected wrist was performed before and after 4 (48 patients) and 8 weeks of treatment (38 patients). Mean T1 values of BME in the lunate, triangular, and capitate bones; RAMRIS for each wrist; Erythrocyte-Sedimentation Rate (ESR); and 28-joint Disease Activity Score (DAS28)-ESR score were analyzed. Patients were divided into responders (4 weeks, 30 patients; 8 weeks, 32 patients) and non-responders (4 weeks, 18 patients; 8 weeks, 6 patients), according to EULAR response criteria. Receiver operating characteristic (ROC) curves were used to evaluate the efficacy of T1 values.

RESULTS

ESR and DAS28-ESR were not correlated with T1 value and RAMRIS at each examination (P > 0.05). Changes in T1 value and DAS28-ESR relative to the baseline were moderately positively correlated with each other at 4 and 8 weeks (r = 0.555 and 0.527, respectively; P < 0.05). At 4 weeks, the change and rate of change in T1 value significantly differed between responders and non-responders (-85.63 vs. -19.92 ms; -12.89% vs. -2.81%; P < 0.05). The optimal threshold of the rate of change in T1 value at 4 weeks for predicting treatment response was -5.32% (area under the ROC curve, 0.833; sensitivity, 0.900; specificity, 0.667).

CONCLUSION

T1 mapping provides a new imaging method for monitoring RA lesions; changes in wrist BME T1 values reflect early treatment response.

Gut-joint axis in knee synovitis: gut fungal dysbiosis and altered fungi-bacteria correlation network identified in a community-based study

OBJECTIVES

Knee synovitis is a highly prevalent and potentially curable condition for knee pain; however, its pathogenesis remains unclear. We sought to assess the associations of the gut fungal microbiota and the fungi-bacteria correlation network with knee synovitis.

METHODS

Participants were derived from a community-based cross-sectional study. We performed an ultrasound examination of both knees. A knee was defined as having synovitis if its synovium was ≥4 mm and/or Power Doppler (PD) signal was within the knee synovium area (PD synovitis). We collected faecal specimens from each participant and assessed gut fungal and bacterial microbiota using internal transcribed spacer 2 and shotgun metagenomic sequencing. We examined the relation of α-diversity, β-diversity, the relative abundance of taxa and the interkingdom correlations to knee synovitis.

RESULTS

Among 977 participants (mean age: 63.2 years; women: 58.8%), 191 (19.5%) had knee synovitis. β-diversity of the gut fungal microbiota, but not α-diversity, was significantly associated with prevalent knee synovitis. The fungal genus Schizophyllum was inversely correlated with the prevalence and activity (ie, control, synovitis without PD signal and PD synovitis) of knee synovitis. Compared with those without synovitis, the fungi-bacteria correlation network in patients with knee synovitis was smaller (nodes: 93 vs 153; edges: 107 vs 244), and the average number of neighbours was fewer (2.3 vs 3.2).

CONCLUSION

Alterations of gut fungal microbiota and the fungi-bacteria correlation network are associated with knee synovitis. These novel findings may help understand the mechanisms of the gut-joint axis in knee synovitis and suggest potential targets for future treatment.

Diagnostic and prognostic role of synovial tissue analysis in juvenile idiopathic arthritis: a monocentric study

OBJECTIVES

This study investigates the diagnostic role of synovial tissue analysis in children presenting with arthritis and assesses its prognostic significance to predict clinical outcome in juvenile idiopathic arthritis (JIA).

METHODS

Synovial samples of paediatric patients undergoing synovial biopsy between 1995 and 2020 were analysed histologically and immunohistochemically. Relationships between histological/immunohistochemical parameters and clinical variables were assessed.

RESULTS

Synovial biopsy was performed for diagnosis in 65 cases allowing to correctly classify 79% of patients.At histological analysis on 42 JIA samples, any difference in the number of synovial lining layers, subsynovial elementary lesions, fibrin deposit, Krenn Synovitis Score, inflammatory infiltrate score and pattern emerged between JIA subsets or on treatment exposure. Synovial tissue analysis predicted outcome: higher number of synovial layers predicted worse disease course (>4 flares during follow-up; 4.5 vs 3.0, p=0.035), even after adjusting for age at diagnosis and observation time (OR 2.2, p=0.007); subjects who had switched>2 biological disease-modifying antirheumatic drugs had higher prevalence of subsynovial elementary lesions (55.6% vs 10.3%, p=0.005) and fibrin deposits in synovial lining (60.0% vs 22.6%, p=0.049), even after adjustment for observation time and age at diagnosis (OR 8.1, p=0.047). At immunohistochemistry on 31 JIA samples, higher CD3 expression was described in polyarticular compared with oligoarticular subset (p=0.040). Patients with severe disease course had higher CD20+ rate (OR 7, p=0.023), regardless of JIA subset and treatment exposure.

CONCLUSIONS

Synovial tissue analysis might support the clinicians in the diagnostic approach of paediatric patients presenting with arthritis and guide the clinical management in JIA.

Distinct mast cell subpopulations within and around lymphatic vessels regulate lymph flow and progression of inflammatory-erosive arthritis in TNF-transgenic mice

Objective

Inflammatory-erosive arthritis is exacerbated by dysfunction of joint-draining popliteal lymphatic vessels (PLVs). Synovial mast cells are known to be pro-inflammatory in rheumatoid arthritis (RA). In other settings they have anti-inflammatory and tissue reparative effects. Herein, we elucidate the role of mast cells on PLV function and inflammatory-erosive arthritis in tumor necrosis factor transgenic (TNF-tg) mice that exhibit defects in PLVs commensurate with disease progression.

Methods

Whole mount immunofluorescent microscopy, toluidine blue stained histology, scanning electron microscopy, and in silico bioinformatics were performed to phenotype and quantify PLV mast cells. Ankle bone volumes were assessed by μCT, while corresponding histology quantified synovitis and osteoclasts. Near-infrared indocyanine green imaging measured lymphatic clearance as an outcome of PLV draining function. Effects of genetic MC depletion were assessed via comparison of 4.5-month-old WT, TNF-tg, MC deficient KitW-sh/W-sh (cKit-/-), and TNF-tg x cKit-/- mice. Pharmacological inhibition of mast cells was assessed by treating TNF-tg mice with placebo or cromolyn sodium (3.15mg/kg/day) for 3-weeks.

Results

PLVs are surrounded by MCT+/MCPT1+/MCPT4+ mast cells whose numbers are increased 2.8-fold in TNF-tg mice. The percentage of peri-vascular degranulating mast cells was inversely correlated with ICG clearance. A population of MCT+/MCPT1-/MCPT4- mast cells were embedded within the PLV structure. In silico single-cell RNA-seq (scRNAseq) analyses identified a population of PLV-associated mast cells (marker genes: Mcpt4, Cma1, Cpa3, Tpsb2, Kit, Fcer1a & Gata2) with enhanced TGFβ-related signaling that are phenotypically distinct from known MC subsets in the Mouse Cell Atlas. cKit-/- mice have greater lymphatic defects than TNF-tg mice with exacerbation of lymphatic dysfunction and inflammatory-erosive arthritis in TNF-tg x cKit-/- vs. TNF-Tg mice. Cromolyn sodium therapy stabilized PLV mast cells, increased TNF-induced bone loss, synovitis, and osteoclasts, and decreased ICG clearance.

Conclusions

Mast cells are required for normal lymphatic function. Genetic ablation and pharmacological inhibition of mast cells exacerbates TNF-induced inflammatory-erosive arthritis with decreased lymphatic clearance. Together, these findings support an inflammatory role of activated/degranulated peri-PLV mast cells during arthritic progression, and a homeostatic role of intra-PLV mast cells, in which loss of the latter dominantly exacerbates arthritis secondary to defects in joint-draining lymphatics, warranting investigation into specific cellular mechanisms.

Advanced Magnetic Resonance Imaging and Molecular Imaging of the Painful Knee

Chronic knee pain is a common condition. Causes of knee pain include trauma, inflammation, and degeneration, but in many patients the pathophysiology remains unknown. Recent developments in advanced magnetic resonance imaging (MRI) techniques and molecular imaging facilitate more in-depth research focused on the pathophysiology of chronic musculoskeletal pain and more specifically inflammation. The forthcoming new insights can help develop better targeted treatment, and some imaging techniques may even serve as imaging biomarkers for predicting and assessing treatment response in the future. This review highlights the latest developments in perfusion MRI, diffusion MRI, and molecular imaging with positron emission tomography/MRI and their application in the painful knee. The primary focus is synovial inflammation, also known as synovitis. Bone perfusion and bone metabolism are also addressed.

Disease activity drives transcriptomic heterogeneity in early untreated rheumatoid synovitis

OBJECTIVES

Transcriptomic profiling of synovial tissue from patients with early, untreated rheumatoid arthritis (RA) was used to explore the ability of unbiased, data-driven approaches to define clinically relevant subgroups.

METHODS

RNASeq was performed on 74 samples, with disease activity data collected at inclusion. Principal components analysis (PCA) and unsupervised clustering were used to define patient clusters based on expression of the most variable genes, followed by pathway analysis and inference of relative abundance of immune cell subsets. Histological assessment and multiplex immunofluorescence (for CD45, CD68, CD206) were performed on paraffin sections.

RESULTS

PCA on expression of the (n=894) most variable genes across this series did not divide samples into distinct groups, instead yielding a continuum correlated with baseline disease activity. Two patient clusters (PtC1, n=52; PtC2, n=22) were defined based on expression of these genes. PtC1, with significantly higher disease activity and probability of response to methotrexate therapy, showed upregulation of immune system genes; PtC2 showed upregulation of lipid metabolism genes, described to characterise tissue resident or M2-like macrophages. In keeping with these data, M2-like:M1-like macrophage ratios were inversely correlated with disease activity scores and were associated with lower synovial immune infiltration and the presence of thinner, M2-like macrophage-rich synovial lining layers.

CONCLUSION

In this large series of early, untreated RA, we show that the synovial transcriptome closely mirrors clinical disease activity and correlates with synovial inflammation. Intriguingly, lower inflammation and disease activity are associated with higher ratios of M2:M1 macrophages, particularly striking in the synovial lining layer. This may point to a protective role for tissue resident macrophages in RA.

Combined femoral and acetabular version and synovitis are associated with dGEMRIC scores in people with femoroacetabular impingement (FAI) syndrome

This study sought to explore, in people with symptoms, signs and imaging findings of femoroacetabular impingement (FAI syndrome): (1) whether more severe labral damage, synovitis, bone marrow lesions, or subchondral cysts assessed on magnetic resonance imaging (MRI) were associated with poorer cartilage health, and (2) whether abnormal femoral, acetabular, and/or combined femoral and acetabular versions were associated with poorer cartilage health. This cross-sectional study used baseline data from the 50 participants with FAI syndrome in the Australian FASHIoN trial (ACTRN12615001177549) with available dGEMRIC scans. Cartilage health was measured using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) score sampled at the chondrolabral junction on three midsagittal slices, at one acetabular and one femoral head region of interest on each slice, and MRI features were assessed using the Hip Osteoarthritis MRI Score. Analyses were adjusted for alpha angle and body mass index, which are known to affect dGEMRIC score. Linear regression assessed the relationship with the dGEMRIC score of (i) selected MRI features, and (ii) femoral, acetabular, and combined femoral and acetabular versions. Hips with more severe synovitis had worse dGEMRIC scores (partial η2  = 0.167, p = 0.020), whereas other MRI features were not associated. A lower combined femoral and acetabular version was associated with a better dGEMRIC score (partial η2  = 0.164, p = 0.021), whereas isolated measures of femoral and acetabular version were not associated. In conclusion, worse synovitis was associated with poorer cartilage health, suggesting synovium and cartilage may be linked to the pathogenesis of FAI syndrome. A lower combined femoral and acetabular version appears to be protective of cartilage health at the chondrolabral junction.

Quantitative bone marrow lesion, meniscus, and synovitis measurement: current status

Imaging plays a pivotal role in osteoarthritis research, particularly in epidemiological and clinical trials of knee osteoarthritis (KOA), with the ultimate goal being the development of an effective drug treatment for future prevention or cessation of disease. Imaging assessment methods can be semi-quantitative, quantitative, or a combination, with quantitative methods usually relying on software to assist. The software generally attempts image segmentation (outlining of relevant structures). New techniques using artificial intelligence (AI) or deep learning (DL) are currently a frequent topic of research. This review article provides an overview of the literature to date, focusing primarily on the current status of quantitative software-based assessment techniques of KOA using magnetic resonance (MR) imaging. We will concentrate on the imaging evaluation of three specific structural imaging biomarkers: bone marrow lesions (BMLs), meniscus, and synovitis consisting of effusion synovitis (ES) and Hoffa's synovitis (HS). A brief clinical and imaging background review of osteoarthritis evaluation, particularly relating to these three structural markers, is provided as well as a general summary of the software methods. A summary of the literature with respect to each KOA assessment method will be presented overall as well as with respect to each specific biomarker individually. Novel techniques, as well as future goals and directions using quantitative imaging assessment, will be discussed.

Abnormalities of the pericruciate fat pad: Correlations with the location and severity of chondral lesions of the knee

PURPOSE

The aim of this study was to evaluate the relationship between the grade of signal change of the pericruciate fat pad (PCFP) and the location and severity of cartilage alterations in the knee on magnetic resonance imaging (MRI).

MATERIALS AND METHODS

This retrospective study included 234 patients (M:F = 96:138, mean: 51 years) who underwent knee MRI. Two experienced musculoskeletal radiologists assessed any PCFP alterations (as grades 0-3) and chondral lesions using the modified Outerbridge grade (as grades 0-4). Bone marrow lesions (BMLs), meniscal status, anterior cruciate ligament alterations, and effusion-synovitis were also evaluated on the MRI. The relationships between PCFP alteration and MR findings (including the grade of chondral lesion) were evaluated.

RESULTS

Signal changes in the PCFP were detected in 150 cases by Reader 1 (grade 0, 67 cases; grade 1, 53 cases; grade 2, 21 cases; grade 3, 9 cases) and in 154 cases by Reader 2 (grade 0, 59 cases; grade 1, 61 cases; grade 2, 24 cases; grade 3, 10 cases). The grade of PCFP signal change was statistically significantly correlated with the grade of the chondral lesion of the medial femoral condyle (MFC) (p = 0.029 and p = 0.003, respectively) and the medial tibial plateau (MTP) (p = 0.045, p = 0.002, Readers 1 and 2, respectively). The grade of PCFP signal change was significantly correlated with the grade of the BMLs of the MFC, MTP, and lateral femoral condyle (p < 0.05) for both readers. PCFP alteration was related to effusion-synovitis and tears of the medial meniscus.

CONCLUSIONS

The grade of PCFP signal change was correlated with the severity of the cartilage alteration in the medial compartment of the knee joint and was also correlated with BMLs in the medial compartment, medial meniscal tears, and synovitis. Therefore, signal change in the PFCP seen on MRI can be an additional clue of the presence of osteoarthritis in the knee, particularly in the medial compartment.

Sclerodermic hand: a retrospective study on the role of ultrasonography in the detection of subclinical joint involvement

INTRODUCTION

The inflammatory involvement of joints and tendons is common in Systemic Sclerosis (SSc). Ultrasonography (US) is a non-invasive tool commonly applied for the assessment of the main inflammatory arthropathies and could be also used in identifying pathological features in SSc patients, even without clinical evidence of joint complaint. So, the aim of this study was to assess the prevalence of US pathological features in a cohort of SSc patients and assessed the role of US in the detection of subclinical joint involvement.

METHODS

In this retrospective study, we collected data about the prevalence of US pathological features at the level of hands and wrists in a cohort of patients with a definite diagnosis of SSc, submitted to an ultrasound examination of hands and wrists according to the clinician's opinion, with or without joint involvement symptoms, in order to assess the US ability in detecting subclinical inflammatory signs in SSc patients.

RESULTS

In total, 47.5% of patients reported at least one US pathological feature. The most common was synovial hypertrophy (62.1%). Other assessed lesions were effusion (48%), tenosynovitis (37.9%), power Doppler (PD) signal (31.0%), and erosions (0.7%). Effusion and PD signal appeared significantly higher in symptomatic patients, with a p<0.01 and p=0.045, respectively.

CONCLUSIONS

In this cohort of SSc subjects, almost the half of the US-positive patients were clinically asymptomatic. Therefore, the application of US could be useful to detect the musculoskeletal involvement of SSc patients, a potential markers of disease severity. Further studies are required to assess the role of US in monitoring SSc patients. Key Points • The inflammatory involvement of joints and/or tendons is common in systemic sclerosis (SSc) but could be partially covered by other disease features. • Among the diagnostic methods able to increase the sensitivity of the musculoskeletal evaluation, Ultrasonography (US) is one of the most promising to reveal subclinical inflammation and predict the joint damage progression. • We retrospectively investigated the prevalence of US pathological features in a cohort of SSc patients, with or without symptoms of joint involvement, assessing the role of US in the detection of subclinical joint involvement. • We found that joint and tendon involvement, a potential marker of disease severity, is common in SSc.

[Septic arthritis and transient synovitis of the hip]

CLINICAL/METHODICAL ISSUE

Differentiating between septic arthritis and transient synovitis can be challenging but is very important as a late diagnosis of septic arthritis can lead to sepsis and joint damage. For correct diagnosis and prediction of complications, the right combination of physical examination, laboratory and radiological studies is needed.

STANDARD RADIOLOGICAL METHODS

Hip ultrasound is easy to learn and has a high sensitivity for joint effusion. Faster diagnosis and therapy are possible due to increasing use of ultrasound. Magnetic resonance imaging (MRI) is primarily used to rule out co-infections (osteomyelitis, pyomyositis) and differential diagnoses. X‑ray is typically nonremarkable in septic arthritis.

PRACTICAL RECOMMENDATIONS

Routine use of ultrasound in nontraumatic pediatric hip pain. Generous use of MRI in case of elevated inflammatory markers or inconclusive clinical findings. Using only few sequences may be appropriate to avoid sedation, primarily fluid sensitive sequences (fat-saturated T2, TIRM, STIR), in case of positive findings, accompanied by T1-weighted images.

The Natural Sequence in Which Subclinical Inflamed Joint Tissues Subside or Progress to Rheumatoid Arthritis: A Study of Serial MRIs in the TREAT EARLIER Trial

OBJECTIVE

The natural trajectory of clinical arthritis progression at the tissue level remains elusive. We hypothesized that subclinical inflammation in different joint tissues (synovitis, tenosynovitis, osteitis) increases in a distinct temporal order in patients with clinically suspect arthralgia (CSA) who develop rheumatoid arthritis (RA) and subsides in a different sequence when CSA spontaneously resolves.

METHODS

We studied 185 serial magnetic resonance images (MRIs) from CSA patients with subclinical joint inflammation from the placebo arm of the TREAT EARLIER trial: 52 MRIs from 21 RA progressors (MRIs conducted at 1 year before, at 4 months before, and upon RA development), and 133 MRIs from 35 patients with spontaneous resolution of pain (MRIs conducted at baseline and at 4, 12, and 24 months). MRIs were scored for osteitis, synovitis, and tenosynovitis. We used cross-lagged models to evaluate 2 types of time patterns between pairs of inflamed tissues: a simultaneous pattern (coinciding changes) and a subsequent pattern (inflammatory changes in 1 tissue preceding changes in another tissue).

RESULTS

In patients who developed RA, synovitis, tenosynovitis, and osteitis increased simultaneously. Increasing osteitis occurred in the final 4 months before RA diagnosis, following incremental tenosynovitis and synovitis changes during the 1 year to 4 months before diagnosis (P < 0.01). In anti-citrullinated protein antibody (ACPA)-positive and ACPA-negative patients who progressed to RA, osteitis increased just before RA development. In patients with pain resolution, simultaneous decreases in synovitis, tenosynovitis, and osteitis occurred, with tenosynovitis decreasing in the first 4 months after CSA onset preceding decreasing synovitis and osteitis during 4-12 months (P = 0.02 and P < 0.01).

CONCLUSION

We identified natural sequences of subclinical inflammation in different joint tissues, which deepens our understanding of clinical arthritis and RA development. During RA progression, increasing osteitis followed previous increases in tenosynovitis and synovitis. During pain resolution, tenosynovitis decreased first, followed by decreasing synovitis and osteitis.

Chronic stage magnetic resonance imaging findings in patients with shoulder injury related to vaccine administration (SIRVA)

PURPOSE

Identify chronic shoulder MRI findings in patients with known shoulder injury related to vaccine administration (SIRVA).

MATERIALS AND METHODS

Two fellowship-trained musculoskeletal radiologists retrospectively reviewed the MRI of nine patients with clinically established SIRVA. MRI was performed at least 4 weeks after vaccination and included intravenous contrast-enhanced sequences. MRI was reviewed for the presence of erosions, tendonitis, capsulitis, synovitis, bone marrow oedema, joint effusion, bursitis, cartilage defects, rotator cuff lesions, and lymphadenopathy. The number and location of focal lesions were recorded.

RESULTS

Erosions of the greater tuberosity were present in 8/9 (89%), tendonitis of the infraspinatus muscle tendon in 7/9 (78%), capsulitis, synovitis, and bone marrow oedema in 5/9 (56%) cases, respectively. Effusion was found in three, and subdeltoid bursitis, rotator cuff lesions as well as cartilage defects in one patient, respectively. None of our included subjects showed axillary lymphadenopathy.

CONCLUSION

In this case series, greater humeral tuberosity erosions, infraspinatus muscle tendonitis, capsulitis, synovitis, and bone marrow oedema were common MRI findings in chronic SIRVA.

Is histopathological synovitis score a predictor of postoperative requirement for additional or alternative drug treatment in the patients with rheumatoid arthritis?

OBJECTIVES

Histopathological synovitis scoring is useful for assessing activity in patients with rheumatoid arthritis (RA) at sampling, but it is unclear whether it can be a predictor of future drug treatment. The purpose of this study was to examine whether histopathological synovitis score is a predictor of postoperative requirement for additional or alternative drug treatment after total knee arthroplasty (TKA).

METHODS

Thirty patients with RA in whom synovial samples were obtained during TKA were included. Patients were divided into the drug treatment enhanced group (EG), which included patients who needed additional or alternative drug treatment within 1 year after TKA, and the drug treatment maintenance group (MG). The Rooney synovitis score (RSS) was compared between groups. Logistic regression analysis was performed to clarify prognostic factors for postoperative drug treatment change.

RESULTS

The total RSS was significantly higher in the EG than in the MG (29.3 vs 15.1; P < .001). Multivariate analysis showed that total RSS and swollen joint counts were independent variable associated with postoperative requirement for additional or alternative drug treatment (P < .05).

CONCLUSIONS

Histopathological synovitis scoring may predict requirement for additional or alternative drug treatment in patients with RA after TKA.

Identification of MYH9 as a key regulator for synoviocyte migration and invasion through secretome profiling

OBJECTIVES

'Invasive pannus' is a pathological hallmark of rheumatoid arthritis (RA). This study aimed to investigate secretome profile of synovial fibroblasts of patients with RA (RA-FLSs), a major cell type comprising the invasive pannus.

METHODS

Secreted proteins from RA-FLSs were first identified using liquid chromatography-tandem mass spectrometry analysis. Ultrasonography was performed for affected joints to define synovitis severity at the time of arthrocentesis. Expression levels of myosin heavy chain 9 (MYH9) in RA-FLSs and synovial tissues were determined by ELISA, western blot analysis and immunostaining. A humanised synovitis model was induced in immuno-deficient mice.

RESULTS

We first identified 843 proteins secreted from RA-FLSs; 48.5% of the secretome was associated with pannus-driven pathologies. Parallel reaction monitoring analysis of the secretome facilitated discovery of 16 key proteins related to 'invasive pannus', including MYH9, in the synovial fluids, which represented synovial pathology based on ultrasonography and inflammatory activity in the joints. Particularly, MYH9, a key protein in actin-based cell motility, showed a strong correlation with fibroblastic activity in the transcriptome profile of RA synovia. Moreover, MYH9 expression was elevated in cultured RA-FLSs and RA synovium, and its secretion was induced by interleukin-1β, tumour necrosis factor α, toll-like receptor ligation and endoplasmic reticulum stimuli. Functional experiments demonstrated that MYH9 promoted migration and invasion of RA-FLSs in vitro and in a humanised synovitis model, which was substantially inhibited by blebbistatin, a specific MYH9 inhibitor.

CONCLUSIONS

This study provides a comprehensive resource of the RA-FLS-derived secretome and suggests that MYH9 represents a promising target for retarding abnormal migration and invasion of RA-FLSs.

Naru-3 inhibits inflammation, synovial hyperplasia, and neovascularization in collagen-induced arthritis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Naru-3 is a prescribed formulation based on the theory of Mongolian medicine for the treatment of rheumatoid arthritis (RA). Naru-3 consists of three medicinal agents: Aconitum kusnezoffii Reichb (caowu), Terminalia chebula Retz (hezi), and Piper longum L (biba). These medicinal agents are widely distributed in the Mongolian area of China and have been used to treat rheumatism for centuries.

BACKGROUND

Mongolian medicine Naru-3 is commonly prescribed to treat RA, but its mechanism of action is unknown.

METHODS

A rat collagen-induced arthritis (CIA) model was established to investigate the mechanism of Naru-3. Rats were treated with Naru-3, Etanercept (ETN), and sodium carboxymethylcellulose (CMC) for four weeks. After treatment was terminated, paw thickness, ankle diameter, and arthritis index (AI) were scored. Synovial hyperplasia was evaluated using hematoxylin and eosin (H&E) staining and two-dimensional ultrasonography. Synovitis and neovascularization were assayed using power Doppler imaging (PDI) and contrast-enhanced ultrasonography (CEUS). Levels of vascular endothelial growth factor (VEGF), interleukin (IL)-1, and CD31 in the serum or synovium were detected using ELISA and immunohistochemistry analyses.

RESULTS

Naru-3 and ETN alleviated the symptoms of CIA as evidenced by diminished paw thickness, ankle diameter, and AI scores. Mechanistically, Naru-3 inhibited synovial hyperplasia, synovitis, and neovascularization by diminishing systemic and local inflammation, as indicated by the relative expression of CD31, VEGF and IL-1 in the serumor synovium. After four weeks of treatment, no significant neovascularization was observed in the Naru-3 group, but neovascularization and synovitis occurred in the ETN group, as demonstrated by H&E staining, PDI, and CEUS examination.

CONCLUSION

Naru-3 inhibited inflammation, synovial hyperplasia, and neovascularization and alleviates RA in our CIA rat model. No symptom recurrence was observed four weeks after drug treatment.

The access route through the anatomical snuffbox in ultrasound-guided synovial biopsy of the wrist allows for a safe and effective collection of tissue samples in inflammatory arthritis

BACKGROUND

A proof-of-concept study to evaluate the feasibility and safety of minimally invasive ultrasound (US)-guided synovial biopsy of the radiocarpal (RC) joint using the anatomical snuffbox as an access route.

METHODS

Twenty consecutive patients with active chronic arthritis of the wrist underwent minimally invasive US-guided synovial biopsy of the RC joint using the anatomical snuffbox as the access route. Samples were retrieved from 3 predetermined biopsy target sites of the RC synovia (proximal, vault, and distal site), aiming for a minimum of 12 samples. The procedure's feasibility was evaluated based on the number and histological quality of retrieved tissue fragments tested on pre-defined histometric parameters. The safety and tolerability of the procedure were assessed through 1-week and 1-month follow-up clinical evaluations.

RESULTS

A median number of 17 fragments (≥ 1 mm diameter size at macroscopic evaluation) per procedure was processed for histopathology (range 9-24) and dedicated to the study. At the histopathologic evaluation, a gradable tissue (visible lining layer and ≥ 4 fragments with IST) was recognized in 19/20 biopsies (95%), and all pre-defined histometric parameters were judged applicable and successfully measured in 19/19 gradable biopsies. All three biopsy target sites showed sampling accessibility. The entire procedure was generally well tolerated. At the 1-month follow-up, no patients showed infectious complications.

CONCLUSIONS

The access route through the anatomical snuff box in US-guided synovial biopsies of the RC joint allows for a safe and targeted collection of adequate tissue samples. This modification of the traditional access route may allow easier, repeatable, and safer sampling of anatomically distinct areas of the wrist in the course of arthritis.

MRI of the temporomandibular joint in children with juvenile idiopathic arthritis: protocol and findings

Contrast-enhanced magnetic resonance imaging (MRI) is the technique of choice for diagnosis and monitoring of temporomandibular joint (TMJ) disorders in patients with juvenile idiopathic arthritis (JIA), as it is able to visualize both soft tissue and osteochondral changes. Approximately 40% of children with JIA develop inflammatory and chronic osteochondral changes observable on imaging, which if left untreated can lead to significant facial growth impairment, including facial asymmetry and retrognathia. MRI of the TMJ plays a paramount role in diagnosis and treatment monitoring in JIA since early signs of TMJ involvement are difficult to detect clinically and with physical examination. Findings of TMJ arthritis may be classified into acute and chronic domains. Early or acute manifestations include joint effusion, bone marrow edema, synovial thickening, and increased joint enhancement. With disease progression, there are characteristic osteochondral changes, including deformity of the mandibular condyle with shortening of the mandibular ramus, bone erosions, and disk abnormalities. In this pictorial essay, we describe a consensus MRI protocol for the study of the TMJ and illustrate the degree of normal and pathological MRI findings using currently available MRI scoring systems of the TMJ developed for JIA.

Hemophilic arthropathy: how to diagnose subclinical bleeding early and how to orthopedically treat a damaged joint

INTRODUCTION

It is important to know the current status of hemophilic arthropathy diagnoses, treatments, complications, and outcomes in developed countries.

AREAS COVERED

A bibliographic search in PubMed for articles published from 1 January 2019 through 12 June 2023 was performed.

EXPERT OPINION

In developed countries with specialized hemophilia treatment centers, primary hematological prophylaxis (started before the age of 2 years and after no more than one joint bleed) has almost completely eliminated the joint-related problems of the disease. The ideal goal of zero hemarthroses can be achieved only with intense and well-dosed prophylaxis: intravenous infusion of coagulation factor - standard half-life or extended half-life; periodic or subcutaneous injections of nonfactor products (emicizumab or fitusiran). However, hemophilic arthropathy continues to occur due to subclinical joint hemorrhages. In one study, 16% of the joints without reported hemarthroses showed signs of previous subclinical bleeding (hemosiderin deposits with/without synovial hypertrophy on magnetic resonance imaging were deemed signs of previous subclinical bleeding), rendering evidence for subclinical bleeding in people with severe hemophilia with lifelong prophylaxis treatment. Subclinical joint hemorrhages can be averted only by employing accurate and tailored prophylaxis.

Development of a Magnetic Resonance Imaging-Based Definition of Knee Osteoarthritis: Data From the Multicenter Osteoarthritis Study

OBJECTIVE

Although magnetic resonance imaging (MRI) is the imaging modality of choice for research, there is no widely accepted MRI definition of knee osteoarthritis (OA). We undertook this study to test the performance of different MRI definitions of OA.

METHODS

We studied Multicenter Osteoarthritis Study participants with knee symptoms using posteroanterior and lateral knee radiographs and MRIs. Radiographic OA was defined as Kellgren/Lawrence grade ≥2 in the tibiofemoral (TF) and/or patellofemoral (PF) joint. Symptomatic OA was defined using a validated questionnaire. MRI findings of cartilage damage, osteophytes, bone marrow lesions (BMLs), and synovitis were scored using the Whole-Organ MRI Score system. We compared definitions using combinations of MRI features to the validation criteria of prevalent radiographic OA and symptomatic OA. All combinations included cartilage damage score ≥2 (0-6 scale) and osteophyte score ≥2 (0-6 scale); addition of BMLs and synovitis score was also tested. We also evaluated a Delphi panel definition that defined OA differently for the PF and TF joints. For each definition, we calculated sensitivity, specificity, and the area under the curve (AUC).

RESULTS

We included 1,185 knees from 1,185 participants (mean age 66 years, 62% female, 89% White). Among the 1,185 knees, 482 knees had radiographic OA, and 524 knees had symptomatic OA. The MRI definitions with a cartilage score ≥2 and osteophyte score ≥2 and definitions which added BMLs or synovitis score ≥1 had the highest sensitivities (95.2% and 94.5%, respectively) for prevalent radiographic OA (AUCs 0.67 and 0.69, respectively), and also had the highest sensitivities for symptomatic OA. The Delphi panel definition had similar performance but was more complex to apply.

CONCLUSION

An MRI OA definition requiring cartilage damage and a small osteophyte with or without BMLs or synovitis had the best performance and was simplest for identifying radiographic OA and symptomatic OA.

Quantitative T2 mapping magnetic resonance imaging of articular cartilage in patients with juvenile idiopathic arthritis

PURPOSE

We aimed to analyze the microstructure changes of knee cartilage in Juvenile idiopathic arthritis (JIA) patients with active synovitis using quantitative magnetic resonance imaging (MRI) T2 mapping technique.

MATERIALS AND METHODS

This study included 23 JIA patients, who underwent bilateral knee joints by using a MR imaging protocol with the addition of a coronal T2 mapping. The femorotibial joint cartilage of participants was divided into eight subregions. Twenty-four (52.17%) of 46 joints (non-synovitis group), and twenty-two (47.83%) joint cases (active-synovitis group) were respectively calculated the T2 mean values for each subregion. Student's T test or Mann-Whitney U test was used to determine the statistical differences of each subregion in the non-synovitis and active-synovitis groups, which is also applied to define the distribution differences of cartilage subregion in femoral and tibial.

RESULTS

The T2 mean values of the superficial and deep zone of cartilage for active synovitis group were respectively higher than those for non-synovitis group (P < 0.05), except for the deep zone of cartilage in lateral tibial plateau (LTP) (P > 0.05). The mean T2 values of the deep zone in femoral cartilage for active synovitis group were significantly higher than that of tibial (P < 0.05).

CONCLUSION

The finding of an increased average T2 values in active synovitis for JIA patients, especially in the deep cartilage of femoral condyle, which suggests that T2 values may reflect cartilage microstructure differences that occur in JIA. T2 mapping as an objective and quantitative method may allow for early detection of cartilage changes.

Worsening of Articular Tissue Damage as Defined by Semi-Quantitative MRI Is Associated With Concurrent Quantitative Cartilage Loss Over 24 Months

OBJECTIVE

To assess the association of worsening of magnetic resonance imaging (MRI) semi-quantitative (SQ) tissue features with concurrent change in quantitative (Q) cartilage thickness measurements over 24 months within the Foundation for the National Institutes of Health (FNIH) Biomarker Consortium study.

METHODS

In all, 599 participants were included. SQ assessment included cartilage damage, meniscal extrusion and damage, osteophytes, bone marrow lesions (BMLs), and effusion- and Hoffa-synovitis. Change in medial compartment Q cartilage thickness was stratified by concurrent ipsicompartmental SQ changes. Between-group comparisons were performed using analysis of covariance (ANCOVA) with adjustment for age, sex, and body mass index (BMI). Results were presented as adjusted mean difference.

RESULTS

Knees with any increase in SQ cartilage scores in the medial compartment (n = 268) showed more Q cartilage loss compared to knees that remained stable (mean adjusted difference [MAD] = -0.16 mm, 95% confidence interval [CI]: [-0.19, -0.13] mm). Knees with any increase in meniscal extrusion in the medial compartment (n = 98) showed more Q cartilage loss than knees without (MAD = -0.18 mm, 95% CI: [-0.22, -0.14] mm. Comparable findings were seen for meniscal damage worsening. Regarding BMLs, an increase by one subregion resulted in a MAD of Q cartilage loss of -0.10 mm, 95% CI: [-0.14, -0.06] mm, while this effect almost tripled for change in two or more subregions. Increase in either effusion- and/or Hoffa-synovitis by one grade resulted in a MAD of -0.07 mm, 95% CI: [-0.10, -0.03] mm.

CONCLUSION

Worsening of SQ cartilage damage, meniscal extrusion and damage, number of subregions affected by BML, maximum size of BMLs and worsening of effusion- and/or Hoffa synovitis is associated with increased Q cartilage loss.

Synovitis, acne, pustulosis, hyperostosis and osteitis syndrome with mandibular involvement: Would surgical operation help?

BACKGROUND

Synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome is a rare autoinflammatory disease; its primary manifestation includes osteoarthropathy with skin involvement. Janus kinase (JAK) inhibitors, such as tofacitinib, were used for rheumatoid arthritis; however, due to its downregulation of immune cytokines including interleukin (IL)-6 and IL-8, it might be effective for SAPHO patients.

CASE SUMMARY

We report the 1st case of mandibular-related SAPHO syndrome treated with tofacitinib. The patient underwent mandibular resection surgery twice and postoperative pathology showed "osteomyelitis". The patient developed sclerosing osteomyelitis in the left wrist 9 months after surgery and SAPHO syndrome was diagnosed. The patient was administered nonsteroidal anti-inflammatory drugs and corticosteroids therapy without much remission. A 3-month tofacitinib therapy provided remission from both systemic inflammation status and peripheral osteoarticular symptoms and no significant recurrence was observed during follow-up in this case.

CONCLUSION

Mandibular involvement in SAPHO syndrome is easily misdiagnosed due to its rarity. Mandibular resection surgery should be applied carefully; after systemic treatment with tofacitinib, the patient had remission. We provide a successful experience for the treatment of mandibular-related SAPHO syndrome.

Polyarticular Joint Pain in Adults: Evaluation and Differential Diagnosis

Polyarticular joint pain involves five or more joints and can be inflammatory or noninflammatory. Two of the most common causes of chronic polyarthritis are osteoarthritis, especially in older patients, and rheumatoid arthritis, which affects at least 0.25% of adults worldwide. The initial evaluation should include a detailed history of the patient's symptoms, with a focus on inflammation, location of pain, duration of symptoms, the presence of systemic symptoms, and any exposures to pathogens that could cause arthritis. Redness, warmth, or swelling in a joint is suggestive of synovitis and joint inflammation. A systematic approach to the physical examination that assesses for a pattern of joint involvement and presence of synovitis can help narrow the differential diagnosis. Laboratory tests, joint aspiration, and imaging studies should be used to confirm a suspected diagnosis. Rheumatoid factor and cyclic citrullinated peptide antibody tests are helpful when there is concern for rheumatoid arthritis. Although magnetic resonance imaging is highly sensitive in identifying erosive bony changes and inflammation, conventional radiography remains the standard for the initial imaging evaluation of rheumatoid arthritis. Point-of-care musculoskeletal ultrasonography can also be a useful tool to detect findings that support a diagnosis of inflammatory arthritis.

Mechanism of action of genicular artery embolization in a rabbit model of knee osteoarthritis

OBJECTIVES

To establish a rabbit osteoarthritis model for genicular artery embolization (GAE) experiments and to investigate the cellular mechanism of action of this novel procedure for interventional radiologists.

METHODS

Rabbit knee osteoarthritis was surgically modeled by anterior cruciate ligament transection and medial partial meniscectomy of the bilateral hindlimbs followed by 10 weeks of incubation. Rabbits exhibiting synovitis on magnetic resonance imaging were randomly divided into two groups: the bilateral GAE group and the control (sham procedure) group. Four weeks later, the rabbits' mobility (moving time, sec/10 min) and the histopathological features of each knee were assessed, and inter-group differences were evaluated using Student's t-test and ordinal/linear logistic models with generalized estimating equations.

RESULTS

Osteoarthritis modeling and endovascular procedures were successful in 15 of 20 rabbits (8 and 7 in the GAE and control groups, respectively). There was no significant difference in moving times between the two groups (p = .958). The degree of structural cartilage damage was similar in both groups (p = .780). However, the synovial proliferation (p = .016), synovial hypertrophy (p < .001), and villous hyperplasia of the synovial stroma (p = .002) scores were significantly lower in the GAE group than in the control group. The CD3+ cell density (p = .018) and CD3 + cell-infiltrated area (p = .019) were also significantly lower in the GAE group than in the control group.

CONCLUSION

GAE can limit inflammatory processes in the synovium of osteoarthritis-affected knees.

KEY POINTS

Surgical transection of the anterior cruciate ligament and medial partial meniscectomy of rabbit knees provides a useful animal model for research of genicular artery embolization. Osteoarthritic knees treated by genicular artery embolization showed milder synovial proliferation (p = .016), synovial hypertrophy (p < .001), and villous hyperplasia of the synovial stroma (p = .002) than the untreated knees. Osteoarthritic knees treated by genicular artery embolization presented lower CD3+ cell density (p = .018) and CD3+ cell-infiltrated area (p = .019) in the synovium than the untreated knees.

Implementation of the OMERACT Psoriatic Arthritis Magnetic Resonance Imaging Scoring System in a randomized phase IIb study of abatacept in psoriatic arthritis

OBJECTIVES

To investigate if the OMERACT PsA MRI Scoring System (PsAMRIS), including a novel total inflammation score, shows sensitivity to change with an agent (abatacept) known to impact clinical outcomes in PsA.

METHODS

We performed a post hoc analysis of a randomized phase IIb study of abatacept in patients with PsA and inadequate DMARD response. Participants received one of three abatacept dosing regimens [ABA3, ABA10 or ABA30/10 mg/kg (30 mg/kg switched to 10 mg/kg after two doses)] or placebo until day 169, then ABA10 through day 365. MRIs at baseline and days 85, 169 and 365 were centrally evaluated by two readers blinded to chronological order and treatment arm. Synovitis, osteitis, tenosynovitis, periarticular inflammation, bone erosions, joint space narrowing and bone proliferation were assessed using the PsAMRIS. A novel total inflammation score was tested.

RESULTS

MRIs for 123 patients were included. On day 169, ABA10 and ABA30/10 significantly reduced MRI synovitis and tenosynovitis, respectively, vs placebo [differences -0.966 (P = 0.039) and -1.652 (P = 0.014), respectively]. Synovitis in the placebo group increased non-significantly from baseline to day 169, total inflammation and tenosynovitis decreased non-significantly and all measures improved significantly after a switch to ABA10 [-1.019, -0.940, -2.275 (P < 0.05), respectively, day 365 vs day 169]. Structural outcomes changed minimally across groups.

CONCLUSION

Adults with PsA receiving ABA10 and ABA30/10 demonstrated significant resolution of inflammatory components of disease, confirmed by MRI, with synovitis and tenosynovitis improvements consistent with previously reported clinical responses for these doses. Results indicate that a reduction in OMERACT PsAMRIS inflammation scores may provide proof of tissue-level efficacy in PsA clinical trials.

REGISTRATION

ClinicalTrials.gov (https://clinicaltrials.gov), NCT00534313.

lncRNA-mediated synovitis in rheumatoid arthritis: A perspective for biomarker development

Long noncoding RNAs (lncRNAs) are a regulatory class of noncoding RNAs with a wide range of activities such as transcriptional and post-transcriptional regulations. Emerging evidence has demonstrated that various lncRNAs contribute to the initiation and progression of Rheumatoid Arthritis (RA) through distinctive mechanisms. The present study reviews the recent findings on lncRNA role in RA development. It focuses on the involvement of different lncRNAs in the main steps of RA pathogenesis including T cell activation, cytokine dysregulation, fibroblast-like synoviocyte (FLS) activation and joint destruction. Besides, it discusses the current findings on RA diagnosis and the potential of lncRNAs as diagnostic, prognostic and predictive biomarkers in Rheumatology clinic.

[Construction and pathological characterization of 3 animal models of temporomandibular joint degenerative joint disease in mice]

Objective: To explore the pathological characteristics of three mice models of temporomandibular joint degenerative joint disease (TMJDJD), including osteoarthritis and osteoarthrosis, and to provide references for animal experimental study regarding the pathological mechanism of osteoarthritis and osteoarthrosis. Methods: A total of 54 8-week-old male C57BL/6 mice were selected to construct three TMJDJD animal models, including bilateral temporomandibular joint (TMJ) Freund's complete adjuvant (FCA) injection model, bilateral TMJ monosodium iodoacetate (MIA) injection model, and right TMJ discectomy model. FCA injection model (15 mice) was divided into saline injection group, FCA injection group-1 week, FCA injection group-2 week, FCA injection group-4 week and FCA injection group-6 week, 3 mice were used at each time point, with a total of 6 TMJs on both sides. MIA injection model (15 mice) was separated into saline injection group, MIA injection group-1 week, MIA injection group-2 week, MIA injection group-4 week and MIA injection group-6 week, 3 mice were used at each time point, with a total of 6 TMJs on both sides. TMJ discectomy model (24 mice) was split into control group, discectomy group-2 week group, discectomy group-4 week and discectomy group-6 week, six mice were used at each time point, with a total of six right TMJs. General pictures of the bilateral joints area of mice were collected 1 day after drug injection, and stereoscopic images of condylar tissues were collected 4 weeks after microsurgery for discectomy. Mouse TMJ tissue sections from each time point were stained with HE and toluidine blue, respectively, synovial tissues were scored for synovial inflammation, and the percentage of proteoglycan in condylar cartilage was quantitatively analyzed. Results: One day after intra-articular FCA or MIA injection, the width of bilateral TMJ were significantly increased in FCA injection groups [(24.60±0.46) mm] compared with the saline injection group [(21.63±0.52) mm] (t=4.25, P<0.013), the width of bilateral TMJ in MIA injection groups [(24.50±0.62) mm] were also significantly higher than that in saline injection group [(21.40±0.52) mm] (t=3.82, P=0.019). The synovitis scores in FCA injection groups 1, 2, 4, 6 weeks after FCA injection were significantly higher than that of the saline injection group (F=18.09, P<0.001), with the proteoglycan of condylar cartilage increased firstly and then decreased compared with the saline injection group (F=21.59, P<0.001). Condylar cartilage proteoglycan loss in different degrees were observed 1, 2, 4 and 6 weeks after MIA injection (F=13.59, P<0.001), and synovitis scores were increased at different degrees compared with saline injection group (F=14.79, P<0.001). The morphology of condylar cartilage in discectomy groups mice were severely damaged, synovial tissues showed dense connective tissue lesions at 2, 4 and 6 weeks postoperatively, condylar cartilage tissues showed a time-dependent loss of proteoglycan compared with the control group (F=40.62, P<0.001). Conclusions: Intra-articular FCA injection establishes a mouse model of TMJ osteoarthritis with severe synovial inflammation. Intra-articular MIA injection constructs a mouse model of typical TMJ osteoarthritis. Discectomy establishes a mouse TMJ osteoarthrosis model with severe condylar cartilage destruction.

Pro and contra: is synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) a spondyloarthritis variant?

PURPOSE OF REVIEW

The purpose of this review is to present the up-to-date evidence on the epidemiology, pathogenesis, musculoskeletal manifestations, and imaging of the synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome and to discuss its relationship with spondyloarthritis (SpA).

RECENT FINDINGS

SAPHO is a rare inflammatory disorder of bone, joints, and skin, with a worldwide distribution that predominantly affects the middle-age adults. The hallmark of the syndrome is a constellation of sterile inflammatory osteitis, hyperostosis, and synovitis involving the anterior chest wall, associated with acneiform and neutrophilic dermatoses, such as palmoplantar pustulosis and severe acne. The axial skeleton, sacroiliac, and peripheral joints can be involved in a similar fashion to SpA. The pathogenesis of the syndrome is multifactorial. The diagnosis is mainly based on the clinical and typical radiological features. The treatment approach is based on the off-label use of antibiotics, bisphosphonates, disease-modifying antirheumatic drugs, and anticytokine biologics.

SUMMARY

The SAPHO syndrome shares common features with SpA-related diseases, yet also shows some unique pathogenetic and clinical features. The nosology of SAPHO remains a subject of controversy, awaiting further research into the pathogenetic and clinical aspects of this syndrome. A better understanding of these aspects will improve the diagnostics and clinical care of patients with SAPHO.

The Genesis of Pain in Osteoarthritis: Inflammation as a Mediator of Osteoarthritis Pain

Chronic pain is a substantial personal and societal burden worldwide. Osteoarthritis (OA) is one of the leading causes of chronic pain and is increasing in prevalence in accordance with a global aging population. In addition to affecting patients' physical lives, chronic pain also adversely affects patients' mental wellbeing. However, there remain no pharmacologic interventions to slow down the progression of OA and pain-alleviating therapies are largely unsuccessful. The presence of low-level inflammation in OA has been recognized for many years as a major pathogenic driver of joint damage. Inflammatory mechanisms can occur locally in joint tissues, such as the synovium, within the sensory nervous system, as well as systemically, caused by modifiable and unmodifiable factors. Understanding how inflammation may contribute to, and modify pain in OA will be instrumental in identifying new druggable targets for analgesic therapies. In this narrative review, we discuss recent insights into inflammatory mechanisms in OA pain. We discuss how local inflammation in the joint can contribute to mechanical sensitization and to the structural neuroplasticity of joint nociceptors, through pro-inflammatory factors such as nerve growth factor, cytokines, and chemokines. We consider the role of synovitis, and the amplifying mechanisms of neuroimmune interactions. We then explore emerging evidence around the role of neuroinflammation in the dorsal root ganglia and dorsal horn. Finally, we discuss how systemic inflammation associated with obesity may modify OA pain and suggest future research directions.

Can CD200R1 Agonists Slow the Progression of Osteoarthritis Secondary to Injury?

Post-traumatic knee osteoarthritis is characterized by cartilage degeneration, subchondral bone remodeling, osteophyte formation, and synovial changes. Therapeutic targeting of inflammatory activity in the knee immediately post injury may alter the course of osteoarthritis development. This study aimed to determine whether CD200R1 agonists, namely the protein therapeutic CD200Fc or the synthetic DNA aptamer CCS13, both known to act as anti-inflammatory agents, are able to delay the pathogenesis of injury-associated knee osteoarthritis in a murine model. Ten week old male C57BL/6 mice were randomized and surgical destabilization of the medial meniscus (DMM) to induce knee arthritis or sham surgery as a control were performed. CCS13 was evaluated as a therapeutic treatment along with CD200Fc and a phosphate-buffered saline vehicle control. Oligonucleotides were injected intra-articularly beginning one week after surgery, with a total of six injections administered prior to sacrifice at 12 weeks post-surgery. Histopathological assessment was used as the primary outcome measure to assess cartilage and synovial changes, while µCT imaging was used to compare the changes to the subchondral bone between untreated and treated arthritic groups. We did not find any attenuation of cartilage degeneration or synovitis in DMM mice with CD200Fc or CCS13 at 12 weeks post-surgery, nor stereological differences in the properties of subchondral bone. The use of CD200R1 agonists to blunt the inflammatory response in the knee are insufficient to prevent disease progression in the mouse DMM model of OA without anatomical restoration of the normal joint biomechanics.

Matrix metalloproteinase-13 is fully activated by neutrophil elastase and inactivates its serpin inhibitor, alpha-1 antitrypsin: Implications for osteoarthritis

Matrix metalloproteinase-13 (MMP-13) is a uniquely important collagenase that promotes the irreversible destruction of cartilage collagen in osteoarthritis (OA). Collagenase activation is a key control point for cartilage breakdown to occur, yet our understanding of the proteinases involved in this process is limited. Neutrophil elastase (NE) is a well-described proteoglycan-degrading enzyme which is historically associated with inflammatory arthritis, but more recent evidence suggests a potential role in OA. In this study, we investigated the effect of neutrophil elastase on OA cartilage collagen destruction and collagenase activation. Neutrophil elastase induced significant collagen destruction from human OA cartilage ex vivo, in an MMP-dependent manner. In vitro, neutrophil elastase directly and robustly activated pro-MMP-13, and N-terminal sequencing identified cleavage close to the cysteine switch at 72 MKKPR, ultimately resulting in the fully active form with the neo-N terminus of 85 YNVFP. Mole-per-mole, activation was more potent than by MMP-3, a classical collagenase activator. Elastase was detectable in human OA synovial fluid and OA synovia which displayed histologically graded evidence of synovitis. Bioinformatic analyses demonstrated that, compared with other tissues, control cartilage exhibited remarkably high transcript levels of the major elastase inhibitor, (AAT) alpha-1 antitrypsin (gene name SERPINA1), but these were reduced in OA. AAT was located predominantly in superficial cartilage zones, and staining enhanced in regions of cartilage damage. Finally, active MMP-13 specifically inactivated AAT by removal of the serine proteinase cleavage/inhibition site. Taken together, this study identifies elastase as a novel activator of pro-MMP-13 that has relevance for cartilage collagen destruction in OA patients with synovitis.

Cellular and molecular diversity in Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a chronic systemic autoimmune disease. RA mainly affects synovial joints, with inflammation of the synovial membrane (synovitis), characterised by neo-angiogenesis, hyperplasia of lining layer, and immune cell infiltration that drive local inflammation and, if untreated, can lead to joint destruction and disability. In parallel to the well-known clinical heterogeneity, the underlying synovitis can also be significantly heterogeneous, both at cellular and molecular level, which can at least in part explain why despite the availability of highly effective treatment options, a large proportion of patients are resistant to some individual treatments. The assimilation of recent high-throughput data from analysis at the single-cell level with rigorous and high-quality clinical outcomes obtained from large randomised clinical trials support the definition of disease and treatment response endotypes. Looking ahead, the integration of histological and molecular signatures from the diseased tissue into clinical algorithms may help decision making in the management of patients with Rheumatoid Arthritis in clinical practice.

Post-traumatic osteoarthritis progression is diminished by early mechanical unloading and anti-inflammatory treatment in mice

OBJECTIVE

Post-traumatic osteoarthritis (PTOA) is a degenerative joint disease initiated by injury. Early phase (0-7 days) treatments often include rest (unloading) and anti-inflammatory medications, but how those early interventions impact PTOA progression is unknown. We hypothesized that early unloading and anti-inflammatory treatment would diminish joint inflammation and slow PTOA progression.

DESIGN

Mice were injured with non-invasive ACL rupture followed by hindlimb unloading (HLU) or normal cage activity (ground control: GC) for 7 days, after which all mice were allowed normal cage activity. HLU and GC mice were treated with daily celecoxib (CXB; 10 mg/kg IP) or vehicle. Protease activity was evaluated using in vivo fluorescence imaging, osteophyte formation and epiphyseal trabecular bone were quantified using micro-computed tomography, and synovitis and articular cartilage were evaluated using whole-joint histology at 7, 14, 21, and 28 days post-injury.

RESULTS

HLU significantly reduced protease activity (-22-30% compared to GC) and synovitis (-24-50% relative to GC) at day 7 post-injury (during unloading), but these differences were not maintained at later timepoints. Similarly, trabecular bone volume was partially preserved in HLU mice at during unloading (-14-15% BV/TV for HLU mice, -21-22% for GC mice relative to uninjured), but these differences were not maintained during reloading. Osteophyte volume was reduced by both HLU and CXB, but there was not an additive effect of these treatments (HLU: -46%, CXB: -30%, HLU + CXB: -35% relative to vehicle GC at day 28).

CONCLUSIONS

These data suggest that early unloading following joint injury can reduce inflammation and potentially slow PTOA progression.

Focal Synovial Inflammation Versus Enthesitis Theory in Distal Psoriatic Arthritis: A Pioneer Histopathologic Study

ABSTRACT

The aim of this analysis was to re-examine the classical concept of distal interphalangeal joint (DIP) psoriatic arthritis (PsA) as an entheseal-driven disease. Two cadaveric fingers with severe psoriatic arthritis were analyzed. Our results demonstrate that inflammation of DIP PsA is multifocal without interconnection between entheses and articular cartilage of the DIP. We found a clear association between synovitis and focal loss of articular cartilage at the head of the intermediate phalanx. By contrast, the articular cartilage adjacent to the zone of severe enthesitis did not show notable damage. Fibrocartilaginous destructions of enthesis were characterized by either a multifocal lymphocytic inflammation, accompanied by osteoclastic resorption, beginning on the interface between the uncalcified and calcified fibrocartilage and then extending into the bone or a subchondral bone inflammation which insidiously destroyed first the bone and then the fibrocartilage. Some sections well showed an inflammation either mild or prominent starting at the level of vascular foramina of flexor enthesis, with secondary invading into the interface between bone and enthesis. The different anatomic sites examined showed a slight predominance of CD8+ T cells over CD4+ T cells: 52% up to 63% for CD8+ T cells vs. to 36% up to 48% for CD4+ T cells. Sparse interspersed CD1a+cells and PS100+cells were also seen with a predominance of PS100+ cells on CD1a+ cells. CD20+ B cells, plasmocytes, neutrophils, and mastocytes were absent or rare. CD123 positive cells were not observed. In DIP PsA, 3 findings predominate: (1) cartilage invasion by the thin pannus offers a more rational explanation for the focal joint destruction than does inflammation of the enthesis which is independent from articular cartilage, (2) the thick ventral plate and to a lesser extend the thin dorsal plate constitute a barrier between the inflamed entheses and the articular cartilage, and (3) an unusual form of minute vascular foramen contributes to the early stage of enthesitis. This small study suggests that DIP PsA is a complex disease. It affects anatomical micro sites which, although close, are in fact relatively independent of each other. Further studies are needed to test this hypothesis.

Imperatorin alleviated NLR family pyrin domain-containing 3 inflammasome cascade-induced synovial fibrosis and synovitis in rats with knee osteoarthritis

We aimed to clarify the therapeutic effects of imperatorin (IMP) on knee osteoarthritis (KOA). Thirty 3-month-old SD male rats were randomly divided into Normal, monosodium iodoacetate (MIA) and MIA+IMP groups. Their synovial tissues were subjected to histopathological analysis. Primary synovial fibroblasts obtained from additional normal rats were treated by lipopolysaccharide (LPS) and then IMP. The mRNA and protein expressions of factors related to synovitis and synovial fibrosis were detected by qRT-PCR and Western blotting, respectively. The concentrations of inflammatory factors IL-1β and IL-18 were measured by ELISA. IMP reduced HIF-1α, NLR family pyrin domain-containing 3 inflammasome expression and IL-1β, IL-18 production in synovial fibroblasts induced by LPS. IMP also downregulated synovial fibrosis markers. In vitro study revealed that MIA-induced synovitis and synovial fibrosis were relieved by IMP. IMP relieves the inflammation associated with synovitis and synovial fibrosis. It reduces the production of pro-inflammatory mediators and cytokines and inhibits TGF-β1, TIMP-1 and VEGF expressions that promote synovial fibrosis.

Pathology-pain relationships in different osteoarthritis animal model phenotypes: it matters what you measure, when you measure, and how you got there

OBJECTIVE

To determine whether osteoarthritis (OA) pain characteristics and mechanistic pathways in pre-clinical models are phenotype-specific.

DESIGN

Male 11-week-old C57BL6 mice had unilateral medial-meniscal-destabilization (DMM) or antigen-induced-arthritis (AIA), vs sham-surgery/immunised-controls (Sham/Im-CT). Pain behaviour (allodynia, mechanical- and thermal-hyperalgesia, hindlimb static weight-bearing, stride-length) and lumbar dorsal root ganglia (DRG) gene-expression were measured at baseline, day-3, week-1/-2/-4/-8/-16, and pain-behaviour:gene-expression:joint-pathology associations investigated.

RESULTS

DMM and AIA induced structural OA defined by progressively increasing cartilage erosion, subchondral bone sclerosis and osteophyte size and maturation. All pain-behaviours were modified, with model-specific differences in severity and temporal pattern. Tactile allodynia developed acutely in both models and persisted to week-16. During early-OA (wk4-8) there was; reduced right hindlimb weight-bearing in AIA; thermal-hyperalgesia and reduced stride-length in DMM. During chronic-OA (wk12-16); mechanical-hyperalgesia and reduced right hindlimb weight-bearing were observed in DMM only. There were no associations in either model between different pain-behaviour outcomes. A coordinated DRG-expression profile was observed in sham and Im-CT for all 11 genes tested, but not in AIA and DMM. At wk-16 despite equivalent joint pathology, changes in DRG-expression (Calca, Trpa1, Trpv1, Trpv4) were observed only in DMM. In AIA mechanical-hyperalgesia was associated with Trpv1 (r = -0.79) and Il1b (r = 0.53). In DMM stride-length was associated with Calca, Tac1, Trpv1, Trpv2, Trpv4 and Adamts5 (r = 0.4-0.57). DRG gene-expression change was correlated with subchondral-bone sclerosis in DMM, and cartilage damage in AIA. Positive pain-behaviour:joint-pathology associations were only present in AIA - for synovitis, subchondral-bone resorption, chondrocyte-hypertrophy and cartilage damage.

CONCLUSION

Pain and peripheral sensory neuronal responses are OA-phenotype-specific with distinct pathology:pain-outcome:molecular-mechanism relationships.

The retinoid X receptor α modulator K-80003 suppresses inflammatory and catabolic responses in a rat model of osteoarthritis

Osteoarthritis (OA), a most common and highly prevalent joint disease, is closely associated with dysregulated expression and modification of RXRα. However, the role of RXRα in the pathophysiology of OA remains unknown. The present study aimed to investigate whether RXRα modulator, such as K-80003 can treat OA. Experimental OA was induced by intra-articular injection of monosodium iodoacetate (MIA) in the knee joint of rats. Articular cartilage degeneration was assessed using Safranin-O and fast green staining. Synovial inflammation was measured using hematoxylin and eosin (H&E) staining and enzyme-linked immunosorbent assay (ELISA). Expressions of MMP-13, ADAMTS-4 and ERα in joints were analyzed by immunofluorescence staining. Western blot, RT-PCR and co-Immunoprecipitation (co-IP) were used to assess the effects of K-80003 on RXRα-ERα interaction. Retinoid X receptor α (RXRα) modulator K-80003 prevented the degeneration of articular cartilage, reduced synovial inflammation, and alleviated osteoarthritic pain in rats. Furthermore, K-80003 markedly inhibited IL-1β-induced p65 nuclear translocation and IκBα degradation, and down-regulate the expression of HIF-2α, proteinases (MMP9, MMP13, ADAMTS-4) and pro-inflammatory factors (IL-6 and TNFα) in primary chondrocytes. Additionally, knockdown of ERα with siRNA blocked these effects of K-80003 in chondrocytes. In conclusion, RXRα modulators K-80003 suppresses inflammatory and catabolic responses in OA, suggesting that targeting RXRα-ERα interaction by RXRα modulators might be a novel therapeutic approach for OA treatment.

Investigation of synovial fluid lubricants and inflammatory cytokines in the horse: a comparison of recombinant equine interleukin 1 beta-induced synovitis and joint lavage models

BACKGROUND

Lameness is a debilitating condition in equine athletes that leads to more performance limitation and loss of use than any other medical condition. There are a limited number of non-terminal experimental models that can be used to study early inflammatory and synovial fluid biophysical changes that occur in the equine joint. Here, we compare the well-established carpal IL-1β-induced synovitis model to a tarsal intra-articular lavage model, focusing on serial changes in synovial fluid inflammatory cytokines/chemokines and the synovial fluid lubricating molecules lubricin/proteoglycan 4 and hyaluronic acid. The objectives of this study were to evaluate clinical signs; synovial membrane and synovial fluid inflammation; and synovial fluid lubricants and biophysical properties in response to carpal IL-1β synovitis and tarsal intra-articular lavage.

RESULTS

Hyaluronic acid (HA) concentrations, especially high molecular weight HA, and synovial fluid viscosity decreased after both synovitis and lavage interventions. Synovial fluid lubricin concentrations increased 17-20-fold for both synovitis and lavage models, with similar changes in both affected and contralateral joints, suggesting that repeated arthrocentesis alone resulted in elevated synovial fluid lubricin concentrations. Synovitis resulted in a more severe inflammatory response based on clinical signs (temperature, heart rate, respiratory rate, lameness and joint effusion) and clinicopathological and biochemical parameters (white blood cell count, total protein, prostaglandin E2, sulfated glycosaminoglycans, tumor necrosis factor-α and CC chemokine ligands - 2, - 3, - 5 and - 11) as compared to lavage.

CONCLUSIONS

Synovial fluid lubricin increased in response to IL-1β synovitis and joint lavage but also as a result of repeated arthrocentesis. Frequent repeated arthrocentesis is associated with inflammatory changes, including increased sulfated glycosaminoglycan concentrations and decreased hyaluronic acid concentrations. Synovitis results in more significant inflammatory changes than joint lavage. Our data suggests that synovial fluid lubricin, TNF-α, CCL2, CCL3, CCL5, CCL11 and sGAG may be useful biomarkers for synovitis and post-lavage joint inflammation. Caution should be exercised when performing repeated arthrocentesis clinically or in experimental studies due to the inflammatory response and loss of HA and synovial fluid viscosity.