Coculture of bovine cartilage with synovium and fibrous joint capsule increases aggrecanase and matrix metalloproteinase activity

Background A hallmark of osteoarthritis is increased proteolytic cleavage of aggrecan. Cross talk between cartilage and the synovium + joint capsule (SJC) can drive cartilage degradation by activating proteases in both tissues. We investigated aggrecan proteolysis patterns in cartilage explants using a physiologically relevant explant model of joint injury combining cartilage mechanical compression and coincubation with SJC. Methods Bovine cartilage explants were untreated; coincubated with SJC; or subjected to mechanical injury and coincubated with SJC, mechanical injury alone, or mechanical injury and incubated with tumor necrosis factor-α (TNF-α). To compare the patterns of aggrecan proteolysis between 6 h and 16 days, release of sulfated glycosaminoglycans and specific proteolytic aggrecan fragments into medium or remaining in cartilage explants was measured by dimethylmethylene blue and Western blot analysis. Results Aggrecanase activity toward aggrecan was observed in all conditions, but it was directed toward the TEGE↓ARGS interglobular domain (IGD) site only when cartilage was coincubated with SJC or TNF-α. Matrix metalloproteinase (MMP) activity at the aggrecan IGD site (IPES↓FFGV) was not detected when cartilage was exposed to TNF-α (up to 6 days), but it was in all other conditions. Compared with when bovine cartilage was left untreated or subjected to mechanical injury alone, additional aggrecan fragment types were released into medium and proteolysis of aggrecan started at an earlier time when SJC was present. Conclusions Indicative of different proteolytic pathways for aggrecan degradation, the SJC increases both aggrecanase and MMP activity toward aggrecan, whereas TNF-α inhibits MMP activity against the IGD of aggrecan.National Institutes of Health (U.S.) (AR060331

Prevalence of knee pain and knee OA in southern Sweden and the proportion that seeks medical care.

The aim of this study was to estimate the prevalence of frequent knee pain in radiographic, symptomatic and clinically defined knee OA in middle-aged and elderly patients and the proportion that seeks medical care

Changes in knee joint load indices from before to 12 months after arthroscopic partial meniscectomy:a prospective cohort study

Patients undergoing arthroscopic partial meniscectomy (APM) are at increased risk of knee osteoarthritis (OA). Meniscal damage and/or surgery may alter knee joint loading to increase OA risk. We investigated changes in knee joint loading following medial APM surgery, compared with the contra-lateral leg

Implementing storm damage in a dynamic vegetation model for regional applications in Sweden

Wind is the dominant agent of damage in forests in Western Europe. Traditional winddamage models calculate a probability for damage or a critical wind speed at which damage occurs. However, in a dynamic vegetation model actual damage to stands and individual trees is needed to get a dynamical progression of the vegetation. We present a prototype for a new approach to modelling forest wind damage at the regional scale, which we incorporate within a dynamic vegetation model. The approach is based on knowledge from both empirical and mechanical models and calculates the damaged fraction of a cohort based on wind load and a sensitivity that depends on the current physical state and history of the cohort in relation to the ecosystem. The modelling concept has been developed, calibrated and evaluated for Swedish conditions but can be applicable to other similar areas with minor modification. Because of the stochastic nature of local wind load and the difficulty of describing the stand-level exposure, the ability to explain observed damage at stand level was low. Regional level variation in damage, which more depends on the wind load, was however explained reasonably well (R2 = 0.43). We suggest that this is a useful concept for evaluating alternatives of forest management under different climate scenarios in the process of adaptation to future storm-damage risks

Hip disability and osteoarthritis outcome score (HOOS) – validity and responsiveness in total hip replacement

BACKGROUND: The aim of the study was to evaluate if physical functions usually associated with a younger population were of importance for an older population, and to construct an outcome measure for hip osteoarthritis with improved responsiveness compared to the Western Ontario McMaster osteoarthritis score (WOMAC LK 3.0). METHODS: A 40 item questionnaire (hip disability and osteoarthritis outcome score, HOOS) was constructed to assess patient-relevant outcomes in five separate subscales (pain, symptoms, activity of daily living, sport and recreation function and hip related quality of life). The HOOS contains all WOMAC LK 3.0 questions in unchanged form. The HOOS was distributed to 90 patients with primary hip osteoarthritis (mean age 71.5, range 49–85, 41 females) assigned for total hip replacement for osteoarthritis preoperatively and at six months follow-up. RESULTS: The HOOS met set criteria of validity and responsiveness. It was more responsive than WOMAC regarding the subscales pain (SRM 2.11 vs. 1.83) and other symptoms (SRM 1.83 vs. 1.28). The responsiveness (SRM) for the two added subscales sport and recreation and quality of life were 1.29 and 1.65, respectively. Patients ≤ 66 years of age (range 49–66) reported higher responsiveness in all five subscales than patients >66 years of age (range 67–85) (Pain SRM 2.60 vs. 1.97, other symptoms SRM 3.0 vs. 1.60, activity of daily living SRM 2.51 vs. 1.52, sport and recreation function SRM 1.53 vs. 1.21 and hip related quality of life SRM 1.95 vs. 1.57). CONCLUSION: The HOOS 2.0 appears to be useful for the evaluation of patient-relevant outcome after THR and is more responsive than the WOMAC LK 3.0. The added subscales sport and recreation function and hip related quality of life were highly responsive for this group of patients, with the responsiveness being highest for those younger than 66

Incidence of severe knee and hip osteoarthritis in relation to different measures of body mass. A population-based prospective cohort study.

OBJECTIVES: To determine in a large prospective population-based cohort study relationships between different measures of body mass and incidence of severe knee and hip osteoarthritis (OA) defined as arthroplasty of knee or hip due to OA. MATERIALS AND METHODS: Body mass index (BMI), waist circumference, waist-hip ratio (WHR), weight, and percentage of body fat (BF%) was measured at baseline in 11026 men and 16934 women, 45 to 73 years old, from the general population. Incidence of severe OA was defined as arthroplasty due to knee or hip OA monitored over 11 years of follow-up by linkage with the Swedish hospital discharge register. RESULTS: During follow-up, 471 individuals had knee OA and 551 had hip OA. After adjustment for age, sex, smoking and physical activity, the relative risks (RR) of knee OA (4th vs. 1st quartile) were 8.1 (95% CI 5.3-12.4) for BMI, 6.7 (4.5-9.9) for waist circumference, 6.5 (4.6-9.43) for weight, 3.6 (2.6-5.0) for BF% and 2.2 (1.7-3.0) for WHR. The corresponding RR for hip OA were 2.6 (2.0-3.4) for BMI, 3.0 (2.3-4.0) for weight, 2.5 (1.9-3.3) for waist, 1.3 (0.99-1.6) for WHR and 1.5 (1.2-2.0) for BF%. CONCLUSIONS: All measures of overweight were significantly associated with incidence of knee OA leading to arthroplasty, with the strongest relative risk gradient observed for BMI. Even though incidence of hip OA showed smaller differences between normal weight and obesity, body mass was a significant risk factor also for hip OA leading to arthroplasty. Our results support a major link between overweight and biomechanics in increasing knee and hip OA risk in both men and women, but do not exclude a contributing role of metabolic factors associated with adipose tissue

Human aggrecanase generated synovial fluid fragment levels are elevated directly after knee injuries due to proteolysis both in the inter globular and chondroitin sulfate domains.

OBJECTIVE: To examine different aggrecanase generated fragments in synovial fluid (SF) from patients with acute and chronic knee injuries and from knee healthy subjects. METHODS: We prepared SF-D1 samples from acute (n=35) and chronic (n=35) knee injury patients and knee healthy subjects (n=10). Aggrecan fragments were analyzed in the SF-D1 samples by quantitative (G1, ARGS, KEEE and G3 antibodies) and non-quantitative (GRGT and AGEG antibodies) Western blot. RESULTS: ARGS-SELE, ARGS-chondroitin sulfate (CS)1, GRGT-, GLGS- and AGEG-G3 fragments were the main ARGS and G3 fragments in injured and reference samples. In the acute injury samples the concentrations of these fragments were increased compared to the reference, and the level of the ARGS-SELE remained elevated for at least 2 years after the joint injury. Both SF ARGS fragments and aggrecanase generated G3 fragments had high sensitivity and specificity as biomarkers in distinguishing injured from healthy knee joints, although the ARGS fragments had higher area under the receiver operating characteristic curve (AUC) values for injuries (74-86%) than the G3 fragments (AUC values 63-68%). CONCLUSION: Our results suggest that during the acute phase after knee injury there is an increased aggrecanase activity against both the interglobular domain (IGD) and the CS2 cleavage sites of joint cartilage aggrecan. This increase in SF aggrecanolytic fragments is present for several years after the injury. SF ARGS fragments are better biomarkers than the aggrecanase generated G3-fragments in distinguishing injured from healthy knee joints

Western blot quantification of aggrecan fragments in human synovial fluid indicates differences in fragment patterns between joint diseases.

OBJECTIVE: To develop a Western blot method for quantification of multiple aggrecan fragments in human synovial fluids (SFs). METHOD: SF aggrecan fragments were prepared from knee healthy (reference), knee injury and arthritis subjects by CsCl gradient centrifugations collecting D1 fractions. Samples were analyzed by Western blot, using antibodies against the N-terminal epitope ARGS and the G3 domain, and fragments were quantified using a digital luminescence image analyzer. RESULTS: The method had a coefficients of variation of 10-30%, and a high correlation (r(S)=0.86) with a corresponding enzyme-linked immunosorbent assay (ELISA). The SFs from reference, knee injured and arthritic subjects contained two major ARGS fragments, ARGS-SELE and ARGS-CS1, and three major G3 fragments (GRGT-G3, GLGS-G3 and AGEG-G3). Compared to the reference, the acute arthritis and acute joint injury groups had a 30-fold elevated concentration of ARGS fragments, and both groups had a higher proportion of the aggrecan in joint fluid as ARGS fragments compared to the other groups. The reference and chronic injury groups had an excess of ARGS-CS1 fragments over ARGS-SELE fragments, while subjects with acute arthritis or osteoarthritis had a more even distribution between these fragments. CONCLUSIONS: We have developed a novel Western blot quantification method for quantification of SF aggrecan fragments which can differentiate fragments of different sizes sharing the same epitope. The anti-ARGS and anti-G3 quantitative Western blots provided information important for a better understanding of the proteolytic pathways in aggrecan breakdown, information that discriminates between different joint diseases, and may aid in identification of new biomarkers