Objective. Joint bleeding, or hemarthrosis, leads in time to severe joint damage. This study was carried out to test the in vitro thresholds of exposure time and concentration that lead to irreversible joint damage, to add to the discussion on the usefulness of aspiration of the joint after a hemorrhage.Methods. Explants of healthy human articular cartilage tissue were cultured in the presence or absence of 50% (volume/volume) blood for 1, 2, 3, or 4 days or in the presence of 0%, 5%, 10%, 20%, 30%, or 50% (v/v) blood for 4 days, followed by a 12-day period of recovery after withdrawal of blood. The effect of blood exposure on cartilage was determined by measuring the rate of proteoglycan synthesis as well as the release and content of cartilage matrix proteoglycans and the activity of matrix metalloproteinases.

SummaryHaemophilic arthropathy is joint damage evolving from recurrent joint bleeds that occur in patients suffering from the clotting disorder haemophilia. Insight into the pathogenetic mechanism of this blood-induced arthropathy yields possible treatment targets and modalities useful to reduce this invalidating co-morbidity of haemophilia. Joint bleeding leads to initially independent adverse changes in both the synovial tissue and the articular cartilage. These subsequently influence each other: the synovial inflammatory changes enhancing cartilage damage and vice versa. Consequently, effective treatment strategies will have to affect both pathways.

Objective: It has been reported that interleukin (IL)-10 limits blood-induced cartilage damage. Our aim was to study the effect of IL-4 alone and in combination with IL-10 on blood-induced cartilage damage. Design: Healthy human full thickness cartilage explants were cultured for 4 days in the presence of 50% v/v blood. IL-4, IL-10, or a combination of both cytokines was added during blood exposure. Cartilage matrix turnover was determined after a recovery period; additionally cytokine production, chondrocyte apoptosis, and expression of the IL-4 and IL-10 receptors were analyzed directly after exposure. Results: Blood-induced damage to the cartilage matrix was limited by IL-4 in a dose-dependent way (P < 0.05). Also IL-10 limited this damage, although to a lesser extent (P < 0.03). The effect of IL-4 plus IL-10 was more pronounced and protective than IL-10 alone (P < 0.05). Production of IL-1b and tumor necrosis factor (TNF)-a was limited by both IL-4 and IL-10 (P < 0.05), but more strongly by IL-4. Bloodinduced apoptosis of chondrocytes was limited by IL-4 and the combination, and not by IL-10 alone. No direct beneficial effect of IL-4 or IL-10 on cartilage was found, however, the chondrocyte receptor expression of both cytokine receptors was upregulated by exposure to blood. Conclusions: This study demonstrates that IL-4 alone and in combination with IL-10 prevents bloodinduced cartilage damage. Expectedly, anti-inflammatory effects on monocytes in the blood fraction and protective effects on chondrocytes are both involved. IL-4 in combination with IL-10 might be used to prevent blood-induced joint damage as a result of trauma or surgery.

Summary Despite prophylactic treatment, haemophilia patients suffer from spontaneous joint bleeds, which lead to severe joint damage. Also after joint trauma, an intra‐articular haemorrhage can add to joint damage over time. This study evaluated interleukin 10 (IL‐10) in the search for possible interventions to prevent or limit the damaging effects of joint bleeds. Human articular cartilage tissue explants were cultured in the presence or absence of 50% v/v blood (or its cellular components) for 4 d (the expected blood load in vivo after a joint haemorrhage), followed by a recovery period of 12 d. Pharmacological dosages of IL‐10 reached during treatment (1 or 10 ng/ml) were added. Additionally, cartilage and synovial tissue obtained from joints with end‐stage haemophilic arthropathy (HA) were cultured in the presence of IL‐10 (10 ng/ml). IL‐10 protected cartilage from the damaging effects of blood exposure, measured by its effects on proteoglycan turnover. In addition, IL‐10 beneficially influenced cartilage from patients with HA and reduced the production of the inflammatory cytokines IL‐1β and tumour necrosis factor‐α by haemophilic synovial tissue. Taken together, although effects were obtained in vitro, IL‐10 protects against blood‐induced joint damage and might be further evaluated as candidate in treatment of tissue damaging effects of joint haemorrhages.

Objective: To assess a wide spectrum of biochemical markers (biomarkers) in a large cohort of individuals with (very) early symptomatic knee and/or hip osteoarthritis (OA). Secondly, to investigate associations between biomarkers and between biomarkers and demographics to demonstrate validity of the obtained dataset and further investigate the involvement and/or role of these biomarkers in OA. Design: Fourteen biomarkers (uCTX-II, uCTX-I, uNTX-I, sCOMP, sPIIANP, sCS846, sC1,2C, sOC, sPINP, sHA, sPIIINP, pLeptin, pAdiponectin, pResistin) were assessed by ELISA or RIA in CHECK (Cohort Hip and Cohort Knee), a 10-year prospective cohort of 1,002 individuals with early symptomatic knee and/or hip OA. Results: Quality controls revealed that gathered data were technically reliable. The majority of biomarkers showed relevant associations with demographic variables, which were expectedly different between genders and/or menopausal status for some. Principal component analysis enabled identification of five clusters, consecutively designated as 'bone-CTX-II', 'inflammation', 'synovium', 'C1,2C-adipokines', and 'cartilage synthesis' cluster. Notably, uCTX-II clustered with biomarkers of bone metabolism, while sCOMP clustered with biomarkers of synovial activity. Conclusions: The identified clusters extended knowledge on individual biomarkers from mostly smaller studies as did the observed associations between biomarker levels and demographics, from which validity of our data was deduced. uCTX-II may not only reflect articular cartilage but also bone metabolism and sCOMP may reflect synovial rather than cartilage metabolism. Major involvement of adipokines in joint metabolism was not identified.

Objective. Hemophilic arthropathy, with characteristics of inflammatory (rheumatoid arthritis) and degenerative (osteoarthritis) joint damage, occurs at an early age, is associated with minor comorbidity, and is restricted to 3 pairs of large joints. The aim of this study was to determine whether commonly used serum and/or urinary biomarkers of cartilage and bone turnover for which assay kits are commercially available are associated with the severity of joint damage in patients with various degrees of hemophilic arthropathy and, thus, whether this disease could be useful in the identification and evaluation of such biomarkers.Methods. Blood and urine samples were collected from 36 patients with various degrees of hemophilic arthropathy. Commercially available assays for the most frequently investigated serum and urine biomarkers were performed: urinary C-terminal telopeptide of type I collagen (CTX-I), urinary CTX-II, serum CTX-I, serum CTX-II, serum cartilage oligomeric matrix protein (COMP), serum cartilage cleavage products C1,2C and C2C, and serum chondroitin sulfate 846 (CS-846).Radiographs of the ankles, knees, and elbows in all patients were evaluated for the degree of joint damage according to the Pettersson score, which is based on cartilage and periarticular bone changes and is specific for hemophilic arthropathy.Results. Urinary CTX-II, serum C1,2C, and serum CS-846 levels correlated with the overall Pettersson score and with the joint space narrowing component. Regression analysis showed that combined indexes of different markers increased the degree of correlation for the combination of urinary CTX-II, serum COMP, and serum CS-846. Bone-specific markers (urinary/serum CTX-I and serum C1,2C) did not correlate with specific bone-related items of the Pettersson score (osteoporosis and erosions).Conclusion. These results support the idea that a combination of biomarkers relates significantly better to the severity of joint damage than do individual biomarkers. The combination of urinary CTX-II, serum COMP, and serum CS-846 correlated best with the degree of arthropathy. Because of its specific characteristics and restricted involvement, hemophilic arthropathy may prove useful in the screening of newly developed biomarkers of joint damage.In the field of osteoarthritis (OA) and rheumatoid arthritis (RA), there is ample research on the applicability of biomarkers in the determination of the severity and/or progression of joint damage and in the evaluation of the effect of (new) treatment modalities (1). These biomarkers are molecules or fragments that are released into biologic fluids during the process of tissue turnover. In OA and RA, biomarkers considered Supported by grants from

This study demonstrates that biochemical markers of joint tissue damage increase shortly after a single joint bleed, both in humans with established hemophilic arthropathy (HA) and in an animal model of joint damage upon a first joint bleed. Biomarkers might be useful in monitoring the impact of a joint bleed and in evaluation of treatment of such bleeds.

Blood is cleared very rapidly from the canine knee joint, but already has adverse effects on both cartilage and synovial tissue within that short time span. This rapid clearance can play a role in the discrepancy between long-term in vitro and in vivo effects of blood-induced joint damage since more than 10% v/v blood present for at least 48 h is needed to induce long-term adverse effects in vitro.