Evolution of synovitis in osteoarthritic knees and its association with clinical features.

OBJECTIVE: To investigate the course of synovitis on contrast-enhanced magnetic resonance images (CE-MRI) in osteoarthritic knees over 2 years, and its association with pain and cartilage deterioration. DESIGN: Consecutive patients (n = 39, mean age 61 years, 79% woman, median (range) body mass index (BMI) 29 (24-48) kg/mm2) with clinical osteoarthritis (OA) were included. Baseline and follow-up CE-MRI (3 T) were scored paired in chronological order for synovitis (semi-quantitatively at 11 sites (range 0-22)), cartilage deterioration and bone marrow lesions (BMLs) (semi-quantitatively according to Knee Osteoarthritis Scoring System (KOSS)). Changes in sum scores were calculated. Cartilage deterioration was defined as change of ≥2 above the smallest detectable change (SDC). Pain was assessed by standardized questionnaires. Analysis of covariance (ANCOVA) and linear regression models were used to investigate association between synovitis change and cartilage deterioration and between synovitis change or cartilage deterioration and change in pain. RESULTS: The total synovitis score did not change over 2 years (mean change 0.2 (standard deviation (SD) 3.2)), although changes in individual patients were observed. Cartilage deterioration was observed in 51% of patients. Synovitis change score was lower in patients without compared to patients with cartilage deterioration, taking BML change in account (mean difference -2.1 (-4.1 to -0.1)). Change in synovitis was not associated with change in pain, whereas cartilage deterioration was associated with change in Intermittent and Constant OsteoArthritis Pain (ICOAP) constant pain in adjusted models (unstandardised coefficient (B) (95% confidence interval (CI)) 2.8 (0.4-5.3)). CONCLUSIONS: In individual patients synovitis fluctuates during disease course. Synovitis change was not associated with change in pain. Increase in synovitis is associated with cartilage deterioration, suggesting a role for synovitis as a target for disease-modifying treatment.

Characterization of synovial mast cells in knee osteoarthritis: association with clinical parameters.

OBJECTIVE: To investigate the presence of mast cells in the osteoarthritic (OA) synovium and their association with clinical parameters in comparison with rheumatoid arthritis (RA) samples. METHOD: Synovial tissues of 56 symptomatic OA and 49 RA patients were obtained. Two to three paraffin slides were used to quantify inflammation using haematoxylin and eosin (H&E) staining (synovitis score 0-9), and numbers of mast cells (per 10 high-power fields) using double immunofluorescence for CD117 and tryptase. Average scores per patient were used for analysis. Knee radiographs of OA patients were scored according to the Kellgren and Lawrence (KL) system and pain was determined in OA patients at baseline by visual analogue scale (VAS). RESULTS: Median (range) of mast cells was significantly higher in OA samples 45 (1-168) compared to RA samples 4 (1-47) (P-value < 0.001), despite a lower median (range) synovitis score in OA (2.5 (0-6.0)) compared to 4.6 (0-8.0) in RA samples. The synovitis score was significantly correlated with the number of mast cells (in OA Spearman's rho (P-value) 0.3 (0.023) and RA 0.5 (P-value < 0.001)). Interestingly, we observed a trend towards an association between the number of mast cells and an increased KL-grade (P-value 0.05) in OA patients, independently of synovitis. No associations were found with self-reported pain. CONCLUSION: Prevalence of mast cells in OA synovial tissue is relatively high and associates with structural damage in OA patients, suggesting a role of mast cells in this disease.

Association of pain in knee osteoarthritis with distinct patterns of synovitis.

OBJECTIVE: To determine possible patterns of synovitis on contrast-enhanced magnetic resonance imaging (CE-MRI) and its relation to pain and severity in patients with radiographic knee osteoarthritis (OA). METHODS: In total, 86 patients (mean age 62 years, 66% women, median body mass index 29 kg/m(2) ) with symptomatic knee OA (Kellgren/Lawrence radiographic score 3) were included. T1-weighted, gadolinium-chelate-enhanced MRI with fat suppression was used to semiquantitatively score the extent of synovitis at 11 knee sites (total score range 0-22). Self-reported pain was assessed with 3 standardized questionnaires. Principal components analysis (PCA) was used to investigate patterns (the location and severity) of synovitis. Subsequently, these patterns were assessed for associations with pain measures and radiographic severity in adjusted logistic regression models. RESULTS: Synovitis was observed in 86 patients and was found to be generally mild on CE-MRI (median total synovitis score 7, range 0-16). The median pain scores were 53 (range 0-96) on the visual analog scale for pain, 51.4 (range 2.8-97.2) on the Knee Injury and Osteoarthritis Outcome Score (KOOS) for pain, 35 (range 0-75) on the Intermittent and Constant Osteoarthritis Pain (ICOAP) score for constant pain, and 40.6 (range 0-87.5) on the ICOAP score for intermittent pain. PCA resulted in extraction of 3 components, explaining 53.4% of the variance. Component 1 was characterized by synovitis at 7 sites (mainly medial parapatellar involvement) and was associated with scores on the KOOS pain subscale and the ICOAP constant pain subscale. Component 2 was characterized by synovitis at 4 sites (mainly the site adjacent to the anterior cruciate ligament), but was not associated with pain measures or with radiographic severity. Component 3, characterized by synovitis at 3 sites (mainly at the loose body site), was associated with radiographic severity. CONCLUSION: Different patterns of synovitis in knee OA were observed. The pattern that included several patellar sites was associated with pain, whereas other patterns showed no association, suggesting that pain perception in patients with knee OA is a localized response.

Degree of synovitis on MRI by comprehensive whole knee semi-quantitative scoring method correlates with histologic and macroscopic features of synovial tissue inflammation in knee osteoarthritis.

OBJECTIVE: To evaluate the association between synovitis on contrast enhanced (CE) MRI with microscopic and macroscopic features of synovial tissue inflammation. METHOD: Forty-one patients (mean age 60 years, 61% women) with symptomatic radiographic knee OA were studied: twenty underwent arthroscopy (macroscopic features were scored (0-4), synovial biopsies obtained), twenty-one underwent arthroplasty (synovial tissues were collected). After haematoxylin and eosin staining, the lining cell layer, synovial stroma and inflammatory infiltrate of synovial tissues were scored (0-3). T1-weighted CE-MRI's (3 T) were used to semi-quantitatively score synovitis at 11 sites (0-22) according to Guermazi et al. Spearman's rank correlations were calculated. RESULTS: The mean (SD) MRI synovitis score was 8.0 (3.7) and the total histology grade was 2.5 (1.6). Median (range) scores of macroscopic features were 2 (1-3) for neovascularization, 1 (0-3) for hyperplasia, 2 (0-4) for villi and 2 (0-3) for fibrin deposits. The MRI synovitis score was significantly correlated with total histology grade [r = 0.6], as well as with lining cell layer [r = 0.4], stroma [r = 0.3] and inflammatory infiltrate [r = 0.5] grades. Moreover, MRI synovitis score was also significantly correlated with macroscopic neovascularization [r = 0.6], hyperplasia [r = 0.6] and villi [r = 0.6], but not with fibrin [r = 0.3]. CONCLUSION: Synovitis severity on CE-MRI assessed by a new whole knee scoring system by Guermazi et al. is a valid, non-invasive method to determine synovitis as it is significantly correlated with both macroscopic and microscopic features of synovitis in knee OA patients.

Osteoarthritis development is induced by increased dietary cholesterol and can be inhibited by atorvastatin in APOE*3Leiden.CETP mice--a translational model for atherosclerosis.

OBJECTIVE: Hypercholesterolaemia, a risk factor for atherosclerosis (ATH), has been suggested to have a role in the development of osteoarthritis (OA). To test this hypothesis, the effect of cholesterol and different cholesterol-lowering treatments on OA was investigated in a mouse model resembling human lipoprotein metabolism. METHODS: Female ApolipoproteinE*3Leiden.human Cholesteryl Ester Transfer Protein mice received a western-type diet with 0.1% (w/w) cholesterol (LC), 0.3% (w/w) cholesterol alone (HC) or treated with 3 mg/kg/day atorvastatin or 0.3 mg/kg/day ezetimibe. One group remained on chow (control). After 39 weeks, OA grades of the knees and the extent of ATH were determined. Plasma cholesterol levels were measured throughout the study. RESULTS: LC and HC groups developed significantly more OA at the medial side than the control group in a dose-dependent manner. Atorvastatin but not ezetimibe treatment significantly suppressed OA development. As expected, features of ATH were significantly increased in the LC and HC groups compared with the control group and suppressed by atorvastatin (48%) and ezetimibe (55%) treatment. There were significant correlations between the development of OA on the medial side of the joint and cholesterol exposure (r=0.4) or ATH features (r=0.3). CONCLUSIONS: Dietary cholesterol and accordingly increased plasma levels play a role in the development of OA. The correlation found between OA, cholesterol and ATH demonstrates that these variables are connected, but indicates the contribution of other ongoing processes in the development of OA. The suppressive effect on OA development of atorvastatin but not of ezetimibe, which had similar cholesterol exposure levels, corroborates these findings.

Metabolic profiling reveals differences in concentrations of oxylipins and fatty acids secreted by the infrapatellar fat pad of donors with end-stage osteoarthritis and normal donors.

OBJECTIVE: The infrapatellar fat pad (IPFP) in the knee joint is hypothesized to contribute to osteoarthritis (OA) development by the IFPF possibly by influencing inflammatory processes. Oxylipins are essential mediators in the inflammatory process. We undertook this study to investigate secretion by the IFPF of fatty acids and oxylipins derived from those fatty acids. METHODS: IPFP explants from 13 OA donors undergoing joint replacement surgery and from 10 normal donors postmortem were cultured for 24 hours, and supernatants (fat-conditioned medium [FCM]) were collected. Liquid chromatography tandem mass spectrometry detected fatty acids and oxylipins in FCM samples. Univariate and multivariate (partial least-squares discriminant analysis [PLS-DA]) analyses were performed, followed by pathway analysis. To validate these outcomes, a second set of OA FCM samples was measured (n=23). RESULTS: Twenty-nine oxylipins and fatty acids could be detected in FCM. Univariate analysis showed no differences between normal donor and OA donor FCM; however, PLS-DA revealed an oxylipin/fatty acid profile consisting of 14 mediators associated with OA (accuracy rate 72%). The most important contributors to the model were lipoxin A4 (decreased), thromboxane B2 (increased), and arachidonic acid (increased). The statistical model predicted 64% of the second set of OA FCM samples correctly. Pathway analysis indicated differences in individual mediators rather than in complete pathways. CONCLUSION: The IPFP secretes multiple and different oxylipins, and a subset of these oxylipins provides a distinctive profile for OA donors. It is likely that the observed changes are regulated by the OA process rather than being a consequence of basal metabolism changes, as an increase in fatty acid levels was not necessarily associated with an increase in oxylipins derived from that fatty acid.

Monounsaturated and Saturated, but Not n-6 Polyunsaturated Fatty Acids Decrease Cartilage Destruction under Inflammatory Conditions: A Preliminary Study.

PURPOSE: Osteoarthritis (OA) is associated with obesity in which altered fatty acid levels have been observed. We investigated whether the most common fatty acids in synovial fluid influence cartilage deterioration in OA. DESIGN: Cartilage was obtained from OA patients undergoing total knee arthroplasty. Chondrocytes or cartilage explants were cultured with linoleic (n-6 polyunsaturated), oleic (monounsaturated), or palmitic (saturated) acid. After preculture, media were renewed and inflammation was simulated in half of the samples by addition of 10 ng/mL tumor necrosis factor-α (TNFα) with or without the fatty acids. Effects on lipid uptake (Oil-Red-O), cell toxicity (lactate dehydrogenase), prostaglandin-E2 (PGE2) release and gene expression for prostaglandin-endoperoxide synthase-2 (PTGS2), matrix metalloproteinase-1 (MMP1), and MMP13, and a disintegrin and metalloproteinase with thrombospondin motifs 4 were determined on chondrocytes in monolayer. Effects on glycosaminoglycan (GAG) release were evaluated on cartilage explants. RESULTS: None of the fatty acids were cytotoxic and all were taken up by the cells, resulting in a higher amount of intracellular lipid in chondrocytes. Linoleic acid increased PGE2 production in the presence of TNFα. Oleic acid and palmitic acid inhibited MMP1 gene expression in chondrocytes stimulated with TNFα. In cartilage explants, GAG release was also inhibited by oleic acid and palmitic acid, and oleic acid decreased PTGS2 gene expression in stimulated chondrocytes. CONCLUSIONS: Linoleic acid has a pro-inflammatory effect on cartilage whereas oleic acid and palmitic acid seem to inhibit cartilage destruction. These results indicate that altered fatty acid levels may influence loss of cartilage structure in OA.

Metabolic stress-induced inflammation plays a major role in the development of osteoarthritis in mice.

OBJECTIVE: Obesity is associated with systemic inflammation and is a risk factor for osteoarthritis (OA) development. We undertook this study to test the hypothesis that metabolic stress-induced inflammation, and not mechanical overload, is responsible for the development of high-fat diet-induced OA in mice. METHODS: Human C-reactive protein (CRP)-transgenic mice received a high-fat diet without or with 0.005% (weight/weight) rosuvastatin or 0.018% (w/w) rosiglitazone, 2 different drugs with antiinflammatory properties. Mice fed chow were included as controls. After 42 weeks, mice were killed and histologic OA grading of the knees was performed. To monitor the overall inflammation state, systemic human CRP levels were determined. RESULTS: Male mice on a high-fat diet had significantly higher OA grades than mice on chow and showed no correlation between OA severity and body weight. In male mice, high-fat diet-induced OA was significantly inhibited by rosuvastatin or rosiglitazone to OA grades observed in control mice. Both treatments resulted in reduced human CRP levels. Furthermore, a positive correlation was found between the relative individual induction of human CRP evoked by a high-fat diet on day 3 and OA grade at end point. CONCLUSION: High-fat diet-induced OA in mice is due to low-grade inflammation and not to mechanical overload, since no relationship between body weight and OA grade was observed. Moreover, the OA process was inhibited to a great extent by treatment with 2 drugs with antiinflammatory properties. The inflammatory response to a metabolic high-fat challenge may predict individual susceptibility to developing OA later in life. The use of statins or peroxisome proliferator-activated receptor γ agonists (e.g., rosiglitazone) could be a strategy for interfering with the progression of OA.

The infrapatellar fat pad of patients with osteoarthritis has an inflammatory phenotype.

OBJECTIVES: Obesity is a risk factor for the development of osteoarthritis (OA) in hands and knees. Adipose tissue can secrete different adipokines with powerful immunomodulatory effects. The infrapatellar fat pad (IFP) is an intra-articular organ in the vicinity of the synovium and cartilage. It is hypothesised that IFP-derived soluble factors could contribute to pathological processes in the knee joint. A study was therefore undertaken to compare the release of inflammatory mediators in the IFP and subcutaneous adipose tissue (ScAT) and to characterise the adipocytes and immune cell infiltrate in these tissues. METHODS: Paired IFP and ScAT samples were obtained from 27 patients with primary OA. The stromal vascular cell fraction (SVF) was isolated and characterised by fluorescence activated cell sorting. Cytokine and adipokine release in fat- and adipocyte-conditioned media was measured by luminex. RESULTS: IFP secreted higher levels of inflammatory mediators such as interleukin 6 (IL-6), adipsin, adiponectin and visfatin than ScAT. This could be due to differences in the phenotype of adipocytes and/or in the composition and phenotype of the SVF cells. IFP adipocyte-conditioned media showed a trend towards more IL-6 and adipsin than ScAT. Moreover, the SVF fraction of IFP contained more cells/g tissue, a lower percentage of T cells and a higher percentage of mast cells than ScAT. In addition, T cells had a predominantly pro-inflammatory phenotype while macrophages had a mixed pro- and anti-inflammatory phenotype in the IFP. CONCLUSION: There are profound differences in secreted inflammatory factors and immune cell composition between the IFP and ScAT. These data indicate that IFP-derived soluble mediators could contribute to pathophysiological processes in the OA knee joint.

Time dependent effects of dexamethasone on serum insulin level and insulin receptors in rat liver and erythrocytes.

The effects of glucocorticoid excess on regulation of insulin receptors were investigated in dexamethasone-treated rats. Glucocorticoid excess was produced by administration of dexamethasone (0.5 mg/100 g b.w.) 30 min, 4, 12, 18, 24, 42 or 70 h before experiments. This treatment caused time-dependent changes of glucose and insulin concentration in blood, as well as in amounts of specific insulin binding and insulin receptors of liver cells and erythrocytes. The time intervals in which dexamethasone produced the increase in insulin concentration were accompanied with decrease in insulin binding to receptors in membranes of liver cells, while significant changes in insulin binding to receptors of erythrocytes were not observed under the same experimental conditions. The effect is maximal 18 and 42 h after dexamethasone treatment that increase insulin blood level by about 85% and 60%, respectively. Receptor analysis revealed that changes in specific binding of insulin could be due to significant changes in amount of binding sites on cell surface rather than to mild alteration in receptor affinity. These findings suggest that besides the changes in insulin level, the alterations in insulin receptor number and affinity may play a major role in the states of altered insulin sensitivity which accompany glucocorticoid excess.

Dependence of the sympatho-adrenal activity on the nutritional status in corticosterone treated rats.

1. An integrated sympatho-adrenal (SA) activity, expressed in terms of urinary catecholamines (CA) excretion, and direct sympathetic activity in the interscapular brown adipose tissue (IBAT), expressed in terms of noradrenaline (NA) turnover, were studied in corticosterone treated stock fed and sucrose overfed rats. 2. Corticosterone in stock fed rats significantly decreased both the rate of IBAT NA turnover and its mass as well as urinary NA excretion but did not change either IBAT NA content, urinary adrenaline excretion or adrenal CA content. 3. Sucrose overfeeding significantly increased SA activity, i.e. the rate of NA turnover in the IBAT and urinary excretion of CA. However, corticosterone did not inhibit the sucrose-induced sympathetic nervous system activation but potentiated the activity of adrenal medulla. 4. The results suggest that the effect of corticosterone treatment on the SA activity in rats is dependent, in addition to other factors, on the nutritional status of the animals.