C2K77 ELISA detects cleavage of type II collagen by cathepsin K in equine articular cartilage.

OBJECTIVES: Develop a species-specific ELISA for a neo-epitope generated by cathepsin K cleavage of equine type II collagen to: (1) measure cartilage type II collagen degradation by cathepsin K in vitro, (2) identify cytokines that upregulate cathepsin K expression and (3) compare cathepsin K with matrix metalloproteinase (MMP) collagenase activity in stimulated cartilage explants and freshly isolated normal and osteoarthritic (OA) articular cartilages. DESIGN: A new ELISA (C2K77) was developed and tested by measuring the activity of exogenous cathepsin K on equine articular cartilage explants. The ELISA was then employed to measure endogenous cathepsin K activity in cultured cartilage explants with or without stimulation by interleukin-1 beta (IL-1ß), tumour necrosis-alpha (TNF-α), oncostatin M (OSM) and lipopolysaccharide (LPS). Cathepsin K activity in cartilage explants (control and osteoarthritic-OA) and freshly harvested cartilage (control and OA) was compared to that of MMPs employing C2K77 and C1,2C immunoassays. RESULTS: The addition of Cathepsin K to normal cartilage caused a significant increase (P < 0.01) in the C2K77 epitope release. Whereas the content of C1,2C, that reflects MMP collagenase activity, was increased in media by the addition to cartilage explants of TNF-α and OSM (P < 0.0001) or IL-1ß and OSM (P = 0.002), no change was observed in C2K77 which also unchanged in OA cartilages compared to normal. CONCLUSIONS: The ELISA C2K77 measured the activity of cathepsin K in equine cartilage which was unchanged in OA cartilage. Cytokines that upregulate MMP collagenase activity had no effect on endogenous cathepsin K activity, suggesting a different activation mechanism that requires further study.

The Effect of Perfusate Volume on Amikacin Concentration in the Metacarpophalangeal Joint Following Cephalic Regional Limb Perfusion in Standing Horses.

OBJECTIVE: To determine the influence of 3 perfusate volumes on amikacin concentration in the metacarpophalangeal joint following cephalic regional limb perfusion (RLP) in standing horses. ANIMALS: Seven healthy horses. METHODS: Three perfusate volumes (100, 60, and 30 mL), containing 2 grams of amikacin, were tested during intravenous RLP at the cephalic vein, placing the tourniquet at mid antebrachium, in standing sedated horses. Synovial fluid was collected from the metacarpophalangeal joint before perfusion and at 30 and 120 minutes after perfusion. Serum samples were taken from the jugular vein at the same time points. Samples were analyzed for amikacin concentrations and a repeated measures ANOVA, followed by least squares difference pairwise comparisons to identify differences in amikacin concentration across perfusate volumes. Differences were considered significant at P<.05. RESULTS: The mean amikacin concentration in synovial fluid at 30 minutes after perfusion was significantly higher following perfusate volume of 100 mL (579 µg/mL), compared to volumes of 60 mL (227 µg/mL) or 30 mL (282 µg/mL) (P<.05). When a threshold of 160 µg/mL was used, more horses reached the synovial therapeutic threshold following perfusate volume of 100 mL (100%), than horses receiving 60 mL (43%) and 30 mL (57%) at 30 minutes after injection. CONCLUSION: The use of 100 mL volume for RLP at the cephalic vein in standing horses resulted in higher concentration of amikacin in the synovial fluid and is recommended for use in clinical cases.

Comparison of two tourniquet application times for regional intravenous limb perfusions with amikacin in sedated or anesthetized horses.

Regional limb perfusion (RLP) in horses has proven to be a simple and effective technique for the treatment of synovial and musculoskeletal infections in the distal portion of the limbs. The ideal tourniquet time needed to achieve therapeutic synovial concentrations remains unknown. The pharmacokinetic effects of general anesthesia (GA) versus standing sedation (SS) RLP on synovial amikacin concentrations are not completely understood. This study investigated the pharmacokinetic effects of RLP under general anesthesia (GA) versus standing sedation (SS) on synovial amikacin concentration following 20 or 30 min tourniquet time. Using 1 g of amikacin RLP was performed in two groups of six horses (GA and SS). A pneumatic tourniquet was applied proximal to the carpus and maintained for 20 or 30 min. Two weeks later, the opposite treatment (20 or 30 min) was randomly performed in the opposite limb of horses in each group (GA and SS). Synovial fluid samples were collected from the metacarpophalangeal (MCP) and radiocarpal (RC) joints. Amikacin was quantified by a fluorescence polarization immunoassay. Regardless of the group, no significant difference in the synovial amikacin concentrations was noted between 20 and 30 min RLP. Mean synovial concentrations of amikacin in the standing sedated horses were significantly higher in the MCP joint at 30 min (P = 0.003) compared to horses under general anesthesia. No significant difference was noted for the RC joint.

Use of ultrasound-guided small joint biopsy to evaluate the histopathologic response to rheumatoid arthritis therapy: recommendations for application to clinical trials.

OBJECTIVE: To examine in a cohort of rheumatoid arthritis (RA) patients undergoing serial ultrasound (US)-guided biopsies of small joints in the context of clinical trials whether sufficient synovial tissue could be obtained at both baseline and second biopsy to: 1) accurately evaluate the synovial immune phenotype, 2) permit adequate RNA extraction to determine molecular signatures, and 3) sensitively detect change in the number of synovial sublining macrophages (CD68+) following effective therapy. METHODS: Synovial samples from RA patients undergoing US-guided biopsy of small joints as part of 2 clinical trials (Barts Early Arthritis Cohort [n = 18] and the Clinical and Pathological Response to Certolizumab Pegol (CLIP-Cert) study [n = 17]) were examined, and the quality and quantity of histologic samples and RNA extracted per joint were determined and compared to synovial thickness and power Doppler scores determined by US before biopsy. Modulation of the number of CD68+ sublining macrophages was correlated with clinical response to treatment. RESULTS: Good quality synovial tissue that accurately reflected the synovial immune phenotype of the total joint was obtained in 80% of US-guided procedures when synovial thickness (higher than grade 2) was documented before biopsy. In 100% of the procedures, sufficient RNA was extracted to permit molecular analysis. There was a significant correlation between change in CD68+ sublining macrophage number and clinical response to treatment. CONCLUSION: This study provides minimum standards for sample retrieval for small joint biopsy. Furthermore, our findings confirm the clinical utility of the procedure in the largest reported cohort of US-guided small joint biopsies. The demonstration that small joint synovial tissue can be readily accessed by a technically simple, minimally invasive procedure is likely to facilitate critical advancements in the knowledge of RA pathobiology and personalized health care.

Contrast-enhanced CT facilitates rapid, non-destructive assessment of cartilage and bone properties of the human metacarpal.

OBJECTIVE: The aim of this work is to establish the human metacarpal as a new whole joint surface early-stage osteoarthritis (OA) model that enables comparisons of articular cartilage and subchondral bone through high resolution contrast-enhanced CT (CECT) imaging, mechanical testing, and biochemical analysis. DESIGN: The fourth metacarpal was obtained from 12 human cadaveric donors and baseline µCT imaging was followed by indentation testing. The samples were then immersed in anionic (Ioxaglate) and cationic (CA4+) iodinated contrast agent solutions followed by CECT. Cartilage GAG content and distribution was measured using the 1,9 dimethylmethylene blue (DMMB) assay and Safranin-O histology staining. Linear regression was performed to compare cartilage and subchondral bone properties. RESULTS: Strong and significant positive correlations were observed between CA4+ CECT attenuation and both GAG content (R(2) = 0.86) and equilibrium modulus (R(2) = 0.84), while correlations using Ioxaglate were insignificant (R(2) ≤ 0.24, P > 0.05). Subchondral bone plate (SBP) thickness negatively and significantly correlated with SBP mineral density (R(2) = 0.49). Cartilage GAG content significantly correlated with several trabecular bone properties, including positive correlations with bone volume fraction (%BV/TV, R(2) = 0.67), trabecular number (Tb.N, R(2) = 0.60), and trabecular thickness (R(2) = 0.42), and negative relationships with structural model index (SMI, R(2) = 0.78) and trabecular spacing (Tb.Sp, R(2) = 0.56). Similarly, equilibrium modulus correlated positively with %BV/TV (R(2) = 0.50), Tb.N (R(2) = 0.59) and negatively with Tb.Sp (R(2) = 0.55) and SMI (R(2) = 0.60). CONCLUSION: This study establishes the human metacarpal as a new early-stage OA model suitable for rapid, high resolution CECT imaging, mechanical testing, and biochemical analysis of the cartilage and subchondral bone, and for examining their inter-relationships.

Comparison of quantitative and semiquantitative dynamic contrast-enhanced MRI with respect to their correlation to delayed gadolinium-enhanced MRI of the cartilage in patients with early rheumatoid arthritis.

OBJECTIVE: The objective of this study was to investigate the correlation between semiquantitative and quantitative dynamic contrast-enhanced (DCE) parameters with delayed gadolinium-enhanced magnetic resonance imaging (MRI) of the cartilage (dGEMRIC). METHODS: Fifteen patients with early rheumatoid arthritis (RA) from the ArthroMark cohort were investigated at a 3-T MRI scanner. The metacarpophalangeal (MCP) joint of the index finger was examined with DCE-MRI and dGEMRIC. Semiquantitative and quantitative DCE perfusion parameters were calculated. The RA MRI score of the second MCP joint and the joint space width were measured. RESULTS: Significant correlations were noted between both semiquantitative and quantitative DCE parameters and the RA MRI score of the second MCP joint. There was a significant negative correlation between DCE parameters and dGEMRIC. No association between joint space width and DCE parameters was observed. CONCLUSIONS: Semiquantitative and quantitative analyses of perfusion are applicable to show that cartilage damage correlates with the inflammation activity despite the absence of joint space narrowing.

Label-free proteomic analysis of the hydrophobic membrane protein complement in articular chondrocytes: a technique for identification of membrane biomarkers.

CONTEXT: There is insufficient knowledge about the chondrocyte membranome and its molecular composition. OBJECTIVE: To develop a Triton X-114 based separation technique using nanoLC-MS/MS combined with shotgun proteomics to identify chondrocyte membrane proteins. MATERIALS AND METHODS: Articular chondrocytes from equine metacarpophalangeal joints were separated into hydrophobic and hydrophilic fractions; trypsin-digested proteins were analysed by nanoLC-MS/MS. RESULTS: A total of 315 proteins were identified. The phase extraction method yielded a high proportion of membrane proteins (56%) including CD276, S100-A6 and three VDAC isoforms. DISCUSSION: Defining the chondrocyte membranome is likely to reveal new biomarker targets for conventional and biological drug discovery.

Associations between biomarkers of joint metabolism, hand osteoarthritis, and hand pain and function: the Johnston County Osteoarthritis Project.

OBJECTIVE: To determine the associations between joint metabolism biomarkers and hand radiographic osteoarthritis [(rOA), based on Kellgren Lawrence (KL) grade ≥ 2], symptoms, and function. METHODS: Cross-sectional data were available for 663 participants (mean age 63 yrs, 63% white, 49% women). Three definitions of hand rOA were considered: (1) a composite measure involving at least 3 hand joints distributed bilaterally with 2 of 3 in the same joint group, including ≥ 1 distal interphalangeal joint, without metacarpophalangeal (MCP) swelling; (2) rOA in at least 1 joint of a group; and (3) number of joints with KL ≥ 2. We assessed hand symptoms and the 15-item Australian Canadian Hand Osteoarthritis Index (AUSCAN; Likert format). We measured serum cartilage oligomeric matrix protein (sCOMP), hyaluronic acid (sHA), carboxy-terminal propeptide of type II collagen, type II collagen degradation product, urinary C-terminal crosslinked telopeptide of type II collagen, and urinary N-terminal crosslinked telopeptide. Linear regression models were performed to assess associations between each biomarker with hand rOA, AUSCAN, and symptoms, adjusting for age, sex, race, current smoking/drinking status, body mass index, and hip and knee rOA. RESULTS: In adjusted analyses, MCP (p < 0.0001) and carpometacarpal rOA (p = 0.003), and a higher number of hand joints with rOA (p = 0.009), were associated with higher levels of sHA. Positive associations were seen between AUSCAN and hand symptoms and levels of sCOMP (p ≤ 0.003) and sHA (p ≤ 0.048). CONCLUSION: Hand symptoms and higher AUSCAN scores were independently associated with higher levels of both sCOMP and sHA; hand rOA was associated only with sHA levels.

Osteitis and synovitis, but not bone erosion, is associated with proteoglycan loss and microstructure damage in the cartilage of patients with rheumatoid arthritis.

OBJECTIVES: To investigate the relation between anatomic changes of the synovium, the bone, the bone marrow and the cartilage to biochemical properties of the cartilage in patients with rheumatoid arthritis (RA). METHODS: 33 patients with RA received 3-T MRI scans of the metacarpophalangeal joints. Two independent methods, (A) the delayed gadolinium enhanced MRI of the cartilage (dGEMRIC, T2-mapping), which was used to assess the biochemical properties of the cartilage; (B) synovitis, osteitis and bone erosions were quantified according to the RA MRI scoring (RAMRIS) method and cartilage thickness (CT), interbone joint space (IBJS, distance between proximal and distal bone surface) and intercartilage joint space (ICJS, distance between proximal and distal cartilage surface) were measured. RESULTS: Biochemical changes of the cartilage, corresponding to low dGEMRIC and high T2 values, were more likely to be seen in joints with decreased IBJS and ICJS as well as decreased CT. For instance, dGEMRIC was directly correlated to the IBJS (p=0.001) and ICJS (p=0.001), whereas T2 mapping was inversely correlated to IBJS and ICJS (both p=0.017). Moreover, the degree of osteitis, and to some extent synovitis, was correlated to biochemical cartilage changes as measured by dGEMRIC (p=0.003) or the T2 mapping (p=0.013). By contrast, bone erosions did not correlate to the degree of biochemical cartilage changes. DISCUSSION: These data support the concept that synovitis and osteitis may be two main triggers for cartilage damage. Thus, the actual inflammatory state of a joint, but not so much the degree of bone erosion, appears to influence cartilage properties in RA.

Molecular imaging of cartilage damage of finger joints in early rheumatoid arthritis with delayed gadolinium-enhanced magnetic resonance imaging.

OBJECTIVE: To assess cartilage glycosaminoglycan content and cartilage thickness in the metacarpophalangeal (MCP) joints of patients with early rheumatoid arthritis (RA) and healthy volunteers. METHODS: After review board approval and informed consent were obtained, 22 subjects were prospectively enrolled (9 patients with early RA [7 women and 2 men with a mean ± SD age of 49 ± 13 years; range 25-68 years] and 13 healthy volunteers [10 women and 3 men with a mean ± SD age of 51 ± 12 years; range 25-66 years). In a total of 44 MCP joints of the index and middle fingers, measurements of cartilage thickness and delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) index (T1 [msec]) were obtained using the variable flip-angle method and a 3T MR scanner. MRIs were evaluated for bone edema, erosions, and synovitis (using the RA MRI Scoring criteria). Student's t-test was used to test the significance of differences between groups. RESULTS: The mean ± SD dGEMRIC index was 497 ± 86 msec in healthy volunteers and was significantly lower in the early RA group (421 ± 76 msec) (P = 0.042). There was no joint space narrowing seen on standard radiographs. No significant difference was found between cartilage thickness in patients with early RA and that in controls (index finger mean ± SD 1.27 ± 0.23 mm in RA patients versus 1.46 ± 0.34 mm in controls [P = 0.16] and middle finger 1.26 ± 0.23 mm in RA patients versus 0.97 ± 0.47 mm in controls [P = 0.10]). No significant correlation was noted between cartilage thickness and dGEMRIC index (R = 0.36, P = 0.88 in RA patients; R = 0.156, P = 0.445 in controls). CONCLUSION: Our findings indicate that cartilage damage is present in the MCP joints of patients with early RA despite the absence of joint space narrowing on standard radiographs and MRI. Cartilage damage in RA can be imaged with dGEMRIC.

Inverse dynamic analysis of the biomechanics of the thumb while pipetting: a case study.

Thumb-push manual pipettes are commonly used tools in many medical, biological, and chemical laboratories. Epidemiological studies indicate that the use of thumb-push mechanical pipettes is associated with musculoskeletal disorders in the hand. The goal of the current study was to evaluate the kinematics and joint loading of the thumb during pipetting. The time-histories of joint angles and the interface contact force between the thumb and plunger during the pipetting action were determined experimentally, and the joint loadings and joint power in the thumb were calculated via an inverse dynamic approach. The moment, power, and energy absorption in each joint of the thumb during the extraction and dispensing actions were analyzed. The results indicate that the majority of the power is generated in the interphalangeal (IP) and carpometacarpal (CMC) joints for the pipetting action. The analysis method and results in the current study will be helpful in exploring the mechanism for musculoskeletal injuries of the hand associated with pipetting, providing a preliminary foundation for ergonomic design of the pipette.

Comparison of the response to experimentally induced short-term inflammation in the temporomandibular and metacarpophalangeal joints of horses.

OBJECTIVE: To investigate the relationship between inflammatory responses of the temporomandibular joint (TMJ) and the metacarpophalangeal (MCP) joint in clinically normal horses. ANIMALS: 7 mature horses. PROCEDURES: In each horse, 1 TMJ and 1 MCP joint were injected with lipopolysaccharide (LPS; 0.0025 µg). The contralateral TMJ and MCP joint were injected with saline (0.9% NaCl) solution. Synovial fluid samples were collected from all 4 joints over 24 hours after injection. Concentrations of interleukin-6, tumor necrosis factor-α, transforming growth factor-ß, and total protein were measured via immunoassay. Horses were assessed for clinical signs of joint inflammation at each time point. RESULTS: Concentrations of interleukin-6 were not significantly different between LPS-injected MCP joints and TMJs at any time point. Transforming growth factor-ß concentrations were significantly increased in MCP joints, compared with concentrations in TMJs, at 12 and 24 hours after injection. Tumor necrosis factor-α concentrations were significantly higher in LPS-injected TMJs than in LPS-injected MCP joints at 1 and 6 hours after injection. Total protein concentration did not differ significantly between LPS-injected MCP joints and TMJs. Injection of LPS induced clinical inflammation at all time points; additionally, 2 MCP joints (but no TMJs) had an inflammatory response to injection of saline solution. CONCLUSIONS AND CLINICAL RELEVANCE: The inflammatory response to LPS appeared to be attenuated more quickly in TMJs than in MCP joints of horses. The difference in response suggested that a lack of clinical osteoarthritis in the TMJ of horses could be attributable to a difference in cytokine response.

Comparison of two tourniquets and determination of amikacin sulfate concentrations after metacarpophalangeal joint lavage performed simultaneously with intravenous regional limb perfusion in horses.

OBJECTIVE: To determine whether joint lavage performed simultaneously with IV regional limb perfusion (IVRLP) reduces the effectiveness of IVRLP and to compare 2 types of tourniquets used for this procedure in horses. ANIMALS: 11 adult horses. PROCEDURES: 2 groups of 6 horses were tested by use of a pneumatic or an Esmarch tourniquet (1 horse was tested twice [once in each group]). Standing IVRLP with amikacin (500 mg) was performed for 30 minutes. Simultaneously, the metacarpophalangeal joint was lavaged with 2 L of lactated Ringer's solution and the egress fluids were collected. Samples of the distal interphalangeal joint synovial fluid and blood from the digital and jugular veins were collected at set time intervals. Amikacin concentrations in all fluids were determined via fluorescence polarization immunoassay. RESULTS: Less amikacin was measured in the systemic circulation with the Esmarch tourniquet than with the pneumatic tourniquet. Amikacin concentrations in the synovial fluid from the distal interphalangeal joints of the Esmarch tourniquet group ranged from 45.1 to 1,968 µg/mL and in the pneumatic tourniquet group ranged from 1.7 to 92.3 µg/mL after 30 minutes of IVRLP. Total loss of amikacin in the egress fluids from the joint lavage ranged from < 1.36 to 7.72 mg for the Esmarch tourniquet group and from < 1.20 to 1.75 mg for the pneumatic tourniquet group. CONCLUSIONS AND CLINICAL RELEVANCE: On standing horses, IVRLP performed simultaneously with joint lavage resulted in negligible loss of amikacin in the egress lavage fluids. The Esmarch tourniquet was more effective in preventing loss of amikacin from the distal portion of the limb, easier to use, and less expensive than the pneumatic tourniquet.

Changes in collagen fibril network organization and proteoglycan distribution in equine articular cartilage during maturation and growth.

The aim of this study was to record growth-related changes in collagen network organization and proteoglycan distribution in intermittently peak-loaded and continuously lower-level-loaded articular cartilage. Cartilage from the proximal phalangeal bone of the equine metacarpophalangeal joint at birth, at 5, 11 and 18 months, and at 6-10 years of age was collected from two sites. Site 1, at the joint margin, is unloaded at slow gaits but is subjected to high-intensity loading during athletic activity; site 2 is a continuously but less intensively loaded site in the centre of the joint. The degree of collagen parallelism was determined with quantitative polarized light microscopy and the parallelism index for collagen fibrils was computed from the cartilage surface to the osteochondral junction. Concurrent changes in the proteoglycan distribution were quantified with digital densitometry. We found that the parallelism index increased significantly with age (up to 90%). At birth, site 2 exhibited a more organized collagen network than site 1. In adult horses this situation was reversed. The superficial and intermediate zones exhibited the greatest reorganization of collagen. Site 1 had a higher proteoglycan content than site 2 at birth but here too the situation was reversed in adult horses. We conclude that large changes in joint loading during growth and maturation in the period from birth to adulthood profoundly affect the architecture of the collagen network in equine cartilage. In addition, the distribution and content of proteoglycans are modified significantly by altered joint use. Intermittent peak-loading with shear seems to induce higher collagen parallelism and a lower proteoglycan content in cartilage than more constant weight-bearing. Therefore, we hypothesize that the formation of mature articular cartilage with a highly parallel collagen network and relatively low proteoglycan content in the peak-loaded area of a joint is needed to withstand intermittent stress and shear, whereas a constantly weight-bearing joint area benefits from lower collagen parallelism and a higher proteoglycan content.

Interleukin-1beta-induced extracellular matrix degradation and glycosaminoglycan release is inhibited by curcumin in an explant model of cartilage inflammation.

Osteoarthritis (OA) is a degenerative and inflammatory disease of synovial joints that is characterized by the loss of articular cartilage, for which there is increasing interest in natural remedies. Curcumin (diferuloylmethane) is the main polyphenol in the spice turmeric, derived from rhizomes of the plant Curcuma longa. Curcumin has potent chemopreventive properties and has been shown to inhibit nuclear factor kappaB-mediated inflammatory signaling in many cell types, including chondrocytes. In this study, normal articular cartilage was harvested from metacarpophalangeal and metatarsophalangeal joints of eight horses, euthanized for reasons other than research purposes, to establish an explant model mimicking the inflammatory events that occur in OA. Initially, cartilage explants (N= 8) were stimulated with increasing concentrations of the proinflammatory cytokine IL-1beta to select effective doses for inducing cartilage degeneration in the explant model. Separate cartilage explants were then cotreated with IL-1beta at either 10 ng/mL (n= 3) or 25 ng/mL (n= 3) and curcumin (0.1 micromol/L, 0.5 micromol/L, 1 micromol/L, 10 micromol/L, and 100 micromol/L). After 5 days, the percentage of glycosaminoglycan (GAG) release from the explants was assessed using a dimethylmethylene blue colorimetric assay. Curcumin (100 micromol/L) significantly reduced IL-1beta-stimulated GAG release in the explants by an average of 20% at 10 ng/mL and 27% at 25 ng/mL back to unstimulated control levels (P < 0.001). Our results suggest that this explant model effectively simulates the proinflammatory cytokine-mediated release of articular cartilage components seen in OA. Furthermore, the evidence suggests that the inflammatory cartilage explant model is useful for studying the effects of curcumin on inflammatory pathways and gene expression in IL-1beta-stimulated chondrocytes.

Do metabolic factors add to the effect of overweight on hand osteoarthritis? The Rotterdam Study.

BACKGROUND: As hand joints are non-weight bearing, the association between overweight and hand osteoarthritis (HOA) is critical to understanding how overweight may associate with osteoarthritis (OA) apart from axial load. Overweight might be associated with the occurrence of OA through other metabolic factors. AIM: To evaluate the role of overweight in HOA, cross-sectional data of a population-based study were used (> or =55 years, n = 3585). The role of diabetes, hypertension and total cholesterol:high-density lipoprotein (HDL)-cholesterol ratio on HOA, and whether they play an intermediate role in the association of overweight/HOA was investigated. Furthermore, the prevalence of HOA in the concurrent presence of overweight and other metabolic factors was evaluated. RESULTS: Independently of other metabolic factors, overweight (body mass index (BMI) >27.4 kg/m(2)) showed a significant association with HOA (OR 1.4, 95% CI 1.2 to 1.7). The association between diabetes and HOA was only present in people aged 55-62 years (OR 1.9, 95% CI 1.0 to 3.8), but was absent in the total population or in other age groups. The association of hypertension with HOA was weak, and disappeared after adjustment for BMI. The total/HDL cholesterol ratio showed no significant association with HOA. The concurrent presence of overweight, diabetes and hypertension resulted in an even higher prevalence of HOA (OR 2.3, 95% CI 1.3 to 3.9) compared with subjects with none of these characteristics; this prevalence increased further in the younger age group (OR 3.2, 95% CI 1.1 to 8.8). CONCLUSION: No intermediate effect of metabolic factors on the association of overweight with HOA was found. An increase in the prevalence of HOA, however, seems to be present when overweight occurs together with hypertension and diabetes especially at a relatively young age.

Nitrite and nitrotyrosine concentrations in articular cartilage, subchondral bone, and trabecular bone of normal juvenile, normal adult, and osteoarthritic adult equine metacarpophalangeal joints.

OBJECTIVE: Osteoarthritis (OA) is a chronic debilitating joint disorder in which the importance of inflammation is increasingly recognized. In advanced cases, both the articular cartilage and the underlying bony layers are affected, but the exact sequence of events and their localization in the initial phase of pathogenesis remain uncertain. We measured nitric oxide (NO) end products in tissue layers that constitute the bearing surface of the joint, as possible indicators of physiological and pathological processes. METHODS: Nitrite as a measure for NO and nitrotyrosine was measured in articular cartilage, subchondral bone, and the underlying trabecular bone of the proximal articular surface of the first phalanx of healthy mature horses (n = 15; age range 5-18 yrs), mature horses affected by OA (n = 15; age range 8-22 yrs), and unaffected juvenile horses (n = 13; age range 6 months-4 yrs). Data were correlated with cartilage damage, as quantified by the Cartilage Degeneration Index. RESULTS: In all 3 layers the nitrite concentration was higher in OA joints (cartilage, p < 0.001; subchondral and trabecular bone, p < 0.05). The concentration of nitrite was significantly higher in cartilage and subchondral bone of juvenile horses compared with mature horses (p < 0.001). Nitrotyrosine concentrations were significantly higher in subchondral bone of OA horses compared with healthy controls (p < 0.001), but significantly lower in trabecular bone of juvenile horses (p < 0.01). CONCLUSION: The similarities observed over the 3 tissue layers support the concept of the bearing surface of the joint as a functional entity. Nitrite concentration seems to be a good indicator of tissue metabolic activity, but cannot discriminate between physiological (juvenile animals) and pathological (OA cases) processes. The increased nitrotyrosine levels in subchondral bone of OA-affected animals suggest that this layer is important in early or moderate OA, and implies a role of oxidative stress in the development of the disease.