Pain in knee osteoarthritis is associated with variation in the neurokinin 1/substance P receptor (TACR1) gene.

BACKGROUND: Substance P (SP) is a pain- and inflammation-related neuropeptide which preferentially binds to the neurokinin receptor 1 (NK1 ). SP and NK1 receptors have been implicated in joint pain, inflammation and damage in animal models and human studies of osteoarthritis (OA). The aim of this study was to test if genetic variation at the neurokinin 1 receptor gene (TACR1) is associated with pain in individuals with radiographic knee OA. METHODS: Participants from the Genetics of OA and Lifestyle study were used for the discovery group (n = 1615). Genotype data for six SNPs selected to cover most variation in the TACR1 gene were used to test for an association with symptomatic OA. Replication analysis was performed using data from the Chingford 1000 Women Study, Hertfordshire Cohort Study, Tasmanian Older Adult Cohort Study and the Clearwater OA Study. In total, n = 1715 symptomatic OA and n = 735 asymptomatic OA individuals were analysed. RESULTS: Out of six SNPs tested in the TACR1 gene, one (rs11688000) showed a nominally significant association with a decreased risk of symptomatic OA in the discovery cohort. This was then replicated in four additional cohorts. After adjusting for age, gender, body mass index and radiographic severity, the G (minor) allele at rs11688000 was associated with a decreased risk of symptomatic OA compared to asymptomatic OA cases (p = 9.90 × 10-4 , OR = 0.79 95% 0.68-0.90 after meta-analysis). CONCLUSIONS: This study supports a contribution from the TACR1 gene in human OA pain, supporting further investigation of this gene's function in OA. SIGNIFICANCE: This study contributes to the knowledge of the genetics of painful osteoarthritis, a condition which affects millions of individuals worldwide. Specifically, a contribution from the TACR1 gene to modulating pain sensitivity in osteoarthritis is suggested.

Does Chondrocalcinosis Associate With a Distinct Radiographic Phenotype of Osteoarthritis in Knees and Hips? A Case-Control Study.

OBJECTIVE: To examine if knee chondrocalcinosis (CC), hip CC, or CC at distant joints associates with a distinct radiographic phenotype of osteoarthritis (OA) in knees or hips. METHODS: We conducted a case-control study using data from the Genetics of Osteoarthritis and Lifestyle (GOAL) study (n = 3,170). All participants of the GOAL study had radiographs of knees, hands, and pelvis, which have been scored for CC and for individual radiographic features of OA. For this study, cases had radiographic OA and CC, and controls had radiographic OA without CC at the index joint. Data for knees and hips were analyzed separately. Binary logistic regression was used to examine the association between each radiographic phenotype and CC in joints with OA. Generalized estimating equation analysis was used to account for correlated data. RESULTS: Knee CC, and CC at any distant joint (without knee CC), associated with attrition in knee OA (adjusted odds ratio 2.32 [95% confidence interval 1.42-3.79] and 2.42 [1.41-4.13], respectively). There was no association between knee CC and osteophytosis or joint space narrowing (JSN) in knees with OA. Hip CC associated negatively with the summated osteophyte score and minimum JSN in hip OA. However, in hips with OA, CC did not associate with cysts or sclerosis. Additionally, distant joint CC did not associate with any structural change in hip OA. CONCLUSION: This study demonstrates that knee CC and CC at distant joints associate with attrition in knee OA, and hip CC associates with a milder hip OA phenotype. There was no evidence that CC associates with a hypertrophic OA phenotype.

Large-scale meta-analysis of interleukin-1 beta and interleukin-1 receptor antagonist polymorphisms on risk of radiographic hip and knee osteoarthritis and severity of knee osteoarthritis.

OBJECTIVE: To clarify the role of common genetic variation in the Interleukin-1ß (IL1B) and Interleukin-1R antagonist (IL1RN) genes on risk of knee and hip osteoarthritis (OA) and severity of knee OA by means of large-scale meta-analyses. METHODS: We searched PubMed for articles assessing the role of IL1B and IL1RN polymorphisms/haplotypes on the risk of hip and/or knee OA. Novel data were included from eight unpublished studies. Meta-analyses were performed using fixed- and random-effects models with a total of 3595 hip OA and 5013 knee OA cases, and 6559 and 9132 controls respectively. The role of ILRN haplotypes on radiographic severity of knee OA was tested in 1918 cases with Kellgren-Lawrence (K/L) 1 or 2 compared to 199 cases with K/L 3 or 4. RESULTS: The meta-analysis of six published studies retrieved from the literature search and eight unpublished studies showed no evidence of association between common genetic variation in the IL1B or IL1RN genes and risk of hip OA or knee OA (P>0.05 for rs16944, rs1143634, rs419598 and haplotype C-G-C (rs1143634, rs16944 and rs419598) previously implicated in risk of hip OA). The C-T-A haplotype formed by rs419598, rs315952 and rs9005, previously implicated in radiographic severity of knee OA, was associated with reduced severity of knee OA (odds ratio (OR)=0.71 95%CI 0.56-0.91; P=0.006, I(2)=74%), and achieved borderline statistical significance in a random-effects model (OR=0.61 95%CI 0.35-1.06 P=0.08). CONCLUSION: Common genetic variation in the Interleukin-1 region is not associated with prevalence of hip or knee OA but our data suggest that IL1RN might have a role in severity of knee OA.

Lifetime body mass index, other anthropometric measures of obesity and risk of knee or hip osteoarthritis in the GOAL case-control study.

OBJECTIVE: To examine the risk of large joint osteoarthritis (OA) in those becoming overweight during early adult life, and to assess the risks associated with high body mass index (BMI) and other anthropometric measures of obesity. METHODS: BMI, waist and hip circumference were measured in the GOAL case-control study comprising hip OA cases (n=1007), knee OA cases (n=1042) and asymptomatic controls (n=1121). Retrospective estimates of lifetime weight, body shape and other risk factors were collected using an interview-lead questionnaire. Odds ratios (ORs), adjusted OR (aOR), 95% confidence intervals (CIs) and P values were calculated using logistic regression analysis. RESULTS: BMI was associated with knee OA (aOR 2.68, 95% CI 2.33-3.09, P-trend<0.001) and hip OA (aOR 1.65, 95% CI 1.46-1.87, P-trend<0.001). Those who became overweight earlier in adulthood showed higher risks of lower limb OA (P-trend<0.001 for knee OA and hip OA). Self-reported body shape was also associated with knee OA and hip OA, following a similar pattern to current and life-course BMI measures. Waist:hip ratio (WHR) at time of examination did not associate with OA independently of BMI, except in women-only analysis. Waist circumference was associated with lower limb OA risk. CONCLUSIONS: Becoming overweight earlier in adult life increased the risks of knee OA and hip OA. Different distribution patterns of adiposity may be related to OA risk in women.

Measurement and visualisation of focal cartilage thickness change by MRI in a study of knee osteoarthritis using a novel image analysis tool.

We describe the application of a novel analysis method that provides detailed maps of changes in cartilage thickness measured from MRI scans for individuals and cohorts of patients together with regional measures. A cohort of osteoarthritis patients was imaged using a 1.0 T MR scanner over a 36-month period. Hyaline cartilage was manually segmented from a three-dimensional (3D) spoiled gradient-echo sequence with fat suppression. Representative outlines of the bone surfaces of the distal femur and proximal tibia were automatically generated from T2 weighted images using statistical models of the shape and appearance of the bones. Cartilage thickness was measured from a dense set of points representing the bony surface. The models of the bones provided a common frame of reference, relative to which change maps were generated and aggregated across the cohort and anatomically corresponding subregions of the joint to be identified. In the reproducibility arm involving six patients, the thickness of cartilage had coefficients of variation of 2.66% within the tibiofemoral joint and 2.94% within the medial femoral condyle region. In the 9 patients (6 female, 3 male) who completed the 36-month study, the most striking observation was that lack of change in global measures of cartilage thickness concealed substantial focal changes. Specifically, the cartilage thickness within the tibiofemoral joint decreased by 0.85% per annum (95% CI -2.13% to 0.45%) with the medial femoral condyle as the region with the most significant change, decreasing by 2.43% per annum (uncorrected 95% CI -4.31% to 0.51%).

Can cartilage loss be detected in knee osteoarthritis (OA) patients with 3-6 months' observation using advanced image analysis of 3T MRI?

PURPOSE: Prior investigations of magnetic resonance imaging (MRI) biomarkers of cartilage loss in knee osteoarthritis (OA) suggest that trials of interventions which affect this biomarker with adequate statistical power would require large clinical studies of 1-2 years duration. We hypothesized that smaller, shorter duration, "Proof of Concept" (PoC) studies might be achievable by: (1) selecting a population at high risk of rapid medial tibio-femoral (TF) progression, in conjunction with; (2) high-field MRI (3T), and; (3) using advanced image analysis. The primary outcome was the cartilage thickness in the central medial femur. METHODS: Multi-centre, non-randomized, observational cohort study at four sites in the US. Eligible participants were females with knee pain, a body mass index (BMI)> or =25 kg/m(2), symptomatic radiographic evidence of medial TF OA, and varus mal-alignment. The 29 participants had a mean age of 62 years, mean BMI of 36 kg/m(2), with eight index knees graded as Kellgren-Lawrence (K&L)=2 and 21 as K&L=3. Eligible participants had four MRI scans of one knee: two MRIs (1 week apart) were acquired as a baseline with follow-up MRI at 3 and 6 months. A trained operator, blind to time-point but not subject, manually segmented the cartilage from the Dual Echo Steady State water excitation MR images. Anatomically corresponding regions of interest were identified on each image by using a three-dimensional statistical shape model of the endosteal bone surface, and the cartilage thickness (with areas denuded of cartilage included as having zero thickness - ThCtAB) within each region was calculated. The percentage change from baseline at 3 and 6 months was assessed using a log-scale analysis of variance (ANOVA) model including baseline as a covariate. The primary outcome was the change in cartilage thickness within the aspect of central medial femoral condyle exposed within the meniscal window (w) during articulation, neglecting cartilage edges [nuclear (n)] (nwcMF x ThCtAB), with changes in other regions considered as secondary endpoints. RESULTS: Anatomical mal-alignment ranged from -1.9 degrees to 6.3 degrees , with mean 0.9 degrees . With one exception, no changes in ThCtAB were detected at the 5% level for any of the regions of interest on the TF joint at 3 or 6 months of follow-up. The change in the primary variable (nwcMF x ThCtAB) from (mean) baseline at 3 months from the log-scale ANOVA model was -2.1% [95% confidence interval (CI) (-4.4%, +0.2%)]. The change over 6 months was 0.0% [95% CI (-2.7%, +2.8%)]. The 95% CI for the change from baseline did not include zero for the cartilage thickness within the meniscal window of the lateral tibia (wLT x ThCtAB) at 6 month follow-up (-1.5%, 95% CI [-2.9, -0.2]), but was not significant at the 5% level after correction for multiple comparisons. CONCLUSIONS: The small inconsistent compartment changes, and the relatively high variabilities in cartilage thickness changes seen over time in this study, provide no additional confidence for a 3- or 6-month PoC study using a patient population selected on the basis of risk for rapid progression with the MRI acquisition and analyses employed.

A meta-analysis of interleukin-6 promoter polymorphisms on risk of hip and knee osteoarthritis.

OBJECTIVE: Interleukin-6 is a pro-inflammatory cytokine involved in the pathogenesis of osteoarthritis (OA). We investigated the role of two single nucleotide polymorphisms (SNPs) mapping to the promoter of the IL-6 gene on genetic susceptibility to hip and knee OA. METHODS: The -174G/C (rs1800795) and -597G/A (rs1800797) SNPs, implicated in the literature in risk of hip and hand OA, were genotyped in 2511 controls, 1101 hip OA cases and 1904 knee OA cases from four cohorts from the UK and Estonia. Data were analysed in conjuntion with published data on rs1800797 from the Genetics of OA and Lifestyle study (UK) on 791 controls, 1034 knee and 997 hip OA cases and rs1800795 data on 75 hip OA cases and 96 controls from Italy. Cases included both radiographic OA only and radiographic and symptomatic OA. Fixed and random-effects meta-analysis models were tested. RESULTS: No significant association was found with hip OA or knee OA with either SNP nor with the haplotypes formed by them. For individual SNPs the smallest P-value for hip OA was observed using a random-effects model for rs1800795 OR(Gallele)=1.066 (95% CI 0.89-1.28) P<0.49, and significant heterogeneity between cohorts (I(2)=65%, P<0.034) was detected. For knee OA the smallest P-value was seen for rs1800797 OR(Aallele)=1.055 (95%CI 0.98-1.12) P<0.18, no significant heterogeneity was observed (I(2)=0%, P<0.68). CONCLUSIONS: Our data do not support a role for the -174 and -597 IL-6 promoter polymorphisms in genetic susceptibility to knee or hip OA in Caucasian populations.

Effects of a metalloproteinase inhibitor on osteochondral angiogenesis, chondropathy and pain behavior in a rat model of osteoarthritis.

OBJECTIVE: To investigate the effects of a matrix metalloproteinase (MMP) inhibitor on joint pathology and pain behavior in the rat meniscal transection (MNX) model of osteoarthritis (OA) and evaluate which aspects of structural disease modification contribute to symptom improvement. METHODS: OA pathology was induced in male Lewis rats, by transecting the medial collateral ligament with (MNX) or without (SHAM) a full thickness cut through the meniscus. MNX animals were orally administered an equipotent MMP 2, 8, 9, 12, 13 inhibitor (0.25, 1 and 5 mg/kg/day) or vehicle from day 1. Chondropathy, osteophytosis, osteochondral vascularity were assessed from toluidine blue stained coronal sections of the total knee joint and weight-bearing asymmetry by incapacitance. Group differences were evaluated using 1-way analysis of variance (ANOVA) and associations as Spearman's correlation coefficients. RESULTS: Treatment with the MMP inhibitor reduced weight-bearing asymmetry from day 14 onwards, and attenuated chondropathy (both P<0.05). Osteochondral vascularity was elevated in MNX compared with SHAM-operated animals (P<0.001) and reduced, dose-dependently, by MMP inhibitor treatment (r=-0.89, P<0.05). Reduced osteochondral vascularity and chondropathy were associated with the amelioration of weight-bearing asymmetry (both P<0.05). CONCLUSION: Here we show that treatment with a MMP inhibitor reduces joint damage, osteochondral angiogenesis and behavioral evidence of pain. The association between osteochondral angiogenesis and pain behavior may be explained by perivascular nerve growth or stimulation of subchondral nerves following loss of osteochondral integrity. Our data suggest that targeting angiogenesis may have utility in the treatment of pain associated with structural damage in OA.

Beta2-adrenergic agonist-induced hypertrophy of the quadriceps skeletal muscle does not modulate disease severity in the rodent meniscectomy model of osteoarthritis.

OBJECTIVE: To examine whether beta2-adrenergic agonist-induced hypertrophy of the quadriceps skeletal muscle can modulate the severity of osteoarthritis (OA) in the rodent meniscectomy (MNX) model. METHODS: Male Lewis rats were subcutaneously administered with 1.5 mg/kg/day clenbuterol hydrochloride (n=15) or saline vehicle (n=20) for 14 days. Following pre-treatment, five animals from each group were sacrificed to assess the immediate effects of clenbuterol. The remaining animals underwent either invasive knee surgery (clenbuterol pre-treated n=10; saline pre-treated n=10) or a sham control surgical procedure (saline pre-treated n=5). During disease initiation and progression, weight bearing was assessed by hindlimb loading. Myosin heavy chain (MHC) protein isoforms were quantified by silver stained SDS PAGE. OA severity was graded by assessment of toluidine blue stained step coronal sections of the total knee joint. RESULTS: Clenbuterol treatment resulted in an increase in total bodyweight, growth rate and in quadriceps skeletal muscle mass. Meniscal surgery resulted in the development of OA-like lesions, changes to weight bearing, and changes in MHC protein expression in the quadriceps. Clenbuterol-induced skeletal muscle hypertrophy had no effect on either weight bearing or articular pathology following MNX surgery. CONCLUSIONS: Our data reveal that clenbuterol-induced skeletal muscle hypertrophy is unable to mimic the beneficial clinical effects of increased musculature derived through targeted strength training in humans, in a rodent model of MNX-induced OA. In addition we observed fibre-type switching to "slow twitch" in the quadriceps muscle during the induction of OA that warrants further investigation as to its relationship to joint stability.

Attempt to replicate published genetic associations in a large, well-defined osteoarthritis case-control population (the GOAL study).

OBJECTIVE: Published studies have tested over 90 genes for association with osteoarthritis (OA), but few positives reported have been independently replicated. Using a new case-control study, our aim was to attempt the replication of findings from 12 genes reported to have significant genetic association with OA and to further examine the role of genetic variation in six of these genes. METHODS: A case-control study was undertaken in Nottingham, UK. Hospital-referred index cases with symptomatic, radiographic OA (ROA) of the knee (n=1040) or hip (n=1004) were recruited. Asymptomatic controls (n=1123) were recruited from intravenous urography waiting lists and screened for radiographic hip and knee OA. Sixty-eight polymorphisms were genotyped in IL1A, IL1B, IL1RN, IL4R, IL6, COL2A1, ADAM12, ASPN, IGF1, TGFB1, ESR1 and VDR. Statistical analysis compared allele or genotype frequencies of these polymorphisms in all asymptomatic controls and the subset of controls without ROA vs all OA, knee OA and hip OA. The analyses were adjusted for age, gender and body mass index. RESULTS: We were unable to replicate any of the published genetic associations investigated. Our extended exploratory analyses identified some associations between polymorphisms in TGFB1, IGF1 and IL1RN and OA; but the strength of evidence varied with the control group used. CONCLUSION: Lack of replication is common and could be due to differences in study design, phenotype, populations examined or the occurrence of false positives in the initial study. Variants within TGFB1, IGF1 and IL1RN could have a role in OA susceptibility; however, replication of these findings is required in an independent study.

Index to ring finger length ratio and the risk of osteoarthritis.

OBJECTIVE: To determine the relationship between the index to ring finger (2D:4D) length ratio and the risk of knee and hip osteoarthritis (OA). METHODS: We conducted a case-control study, in which cases with persistent symptoms and radiographic evidence of knee or hip OA were compared with controls with no symptoms and no radiographic evidence of knee or hip OA. Hand radiographs were visually classified as type 1 (index finger longer than the ring finger), type 2 (index finger equal to the ring finger), or type 3 (index finger shorter than the ring finger). The 2D:4D phalangeal and metacarpal length ratios were measured separately. The odds ratio (OR) and 95% confidence interval (95% CI) were calculated and adjusted for possible confounding factors using a logistic regression model. RESULTS: Of 2,049 cases, 1,013 had radiographic evidence of knee OA and 995 had hip OA. Of 1,123 controls, 836 had no knee OA and 1,050 had no hip OA. The type 3 finger pattern was associated with knee OA (OR 1.94, 95% CI 1.54-2.44), and the risk was greater in women (OR 3.05, 95% CI 2.08-4.47) than in men (OR 1.45, 95% CI 1.08-1.95). There was a dose-response relationship between both 2D:4D phalangeal and metacarpal length ratios and the risk of knee OA. The risk of hip OA was inconsistent. CONCLUSION: Compared with types 1 and 2, the type 3 "male" pattern 2D:4D length ratio is associated with OA, especially knee OA. The risk is independent of other major OA risk factors.

Radiographic assessment of the index to ring finger ratio (2D:4D) in adults.

The smaller index to ring finger (2D:4D) ratio has been considered as a 'male finger pattern' and is associated with sporting ability and a number of conditions. However, the ratio may vary according to what is measured, the hand selected and the method used. This study aimed to determine: (1) which bones (phalanges, metacarpals or both) account for variation in the 2D:4D ratio; (2) whether the ratio shows right-left symmetry or relates to hand dominance; and (3) the correlation between visual classification and measured determinations of the ratio based on radiographs. Hand radiographs obtained as part of a large osteoarthritis genetic study were examined. Each hand was classified visually into three types according to the relative length of the index and ring finger: Type 1 (index longer than ring), Type 2 (index = ring) and Type 3 (index shorter than ring). For both index and ring fingers we measured (1) from base of proximal to tip of distal phalanx and (2) metacarpal length. Reproducibility of the classification and measurements were examined using kappa and intraclass correlation coefficient; symmetry between left and right hands was examined using Bland and Altman's agreement analysis; and correlation between visual classification and 2D:4D ratio data was analysed using the anova linearity test. Data were obtained from 3172 radiographs (1636 men, 1536 women; mean age 67 +/- 7.9 years, range 45-86 years). Prevalence of Type 3 hand was 61% in men and 37% in women (P < 0.001). Men had smaller 2D:4D ratios than women for phalanges (0.908 versus 0.922, P < 0.01), metacarpals (1.152 versus 1.157, P < 0.01) and the sum of phalanges plus metacarpals (1.005 versus 1.015, P < 0.01). The mean difference between right and left was -0.001 (95% limit of agreement -0.035, 0.032) for the phalangeal ratio and 0.003 (95% limit of agreement -0.051 to 0.057) for the metacarpal ratio. The 2D:4D ratio did not associate with handedness or age. There was a linear trend between the visual classification of hand type and the 2D:4D ratio data (P < 0.001). More technical difficulties (due to positioning, finger trauma, osteoarthritis) were encountered with the phalangeal ratio and visual categorization than with the metacarpal ratio: the latter could be measured in 98.7% of the study population. We concluded that measured 2D:4D ratios and visual categorization can be derived from hand radiographs. The phalanges and metacarpals both contribute to the variation in 2D:4D ratio with smaller ratios observed in men than in women. The ratio is symmetrical with only very small differences between right and left hands. Visual classification may be a useful simple tool for future epidemiological studies but is more prone to bias from positioning than direct measurement. If radiographs are used for this purpose, we recommend the metacarpal ratio with measurement of a single index hand or an average of both as it is least affected by bias from malpositioning, trauma or common joint disease.

Measurement of cartilage volumes in rheumatoid arthritis using MRI.

MRI is a valuable imaging modality for assessment of the articular cartilage in rheumatoid arthritis (RA) and is potentially of use in monitoring disease progression and response to therapy. In this study, we investigated the sources of error in volume measurements obtained by segmentation of MR images of knee cartilage in patients with RA and followed cartilage volume in a group of RA patients for 12 months. 23 RA patient volunteers were recruited for knee imaging. Six subjects were imaged at baseline only, six were imaged at baseline and again within an hour in the same imaging session, six subjects were imaged at baseline and 7 days, and 17 subjects were imaged at baseline, 4+/-2 months and 12 months. Imaging was performed at 1.0 T using a three-dimensional spoiled gradient-echo sequence with fat-suppression. Manual image segmentation was performed once or twice on the lateral tibial, medial tibial, patellar and femoral compartment by either one or two segmenters. Coefficients of variation (CoV) for repeated volume measurement of total cartilage were 2.2% (same segmenter, same scan), 5.2% (different segmenter, same scan), 4.9% (same segmenter, different scan, same session), and 4.4% (same segmenter, different scan, different session). Over the 12 month duration of the study there was no significant change in total cartilage volume, nor were there significant changes in volume in any individual compartment. This measurement technique is reproducible, but any net change in cartilage volume over 1 year is very small.

Magnetic resonance imaging measurement of knee cartilage volume in a multicentre study.

OBJECTIVE: To investigate the variability between different high-field scanners in magnetic resonance imaging (MRI) measurement of knee cartilage volume in healthy female volunteers. METHODS: Five volunteers had both knees scanned using three different MRI scanners. Cartilage volume in each compartment was measured from the images by image segmentation. The data were analysed using analysis of variance models. RESULTS: The mean total cartilage volume of the 10 knees scanned at three different centres was 16.15, 16.40 and 15.63 ml for the Siemens, GE and Philips scanners respectively. Small systematic differences were seen in the total knee cartilage volume results. CONCLUSIONS: Although there were small systematic differences in knee cartilage volume, the three MRI scanners gave broadly similar results.

Characterisation of the guinea pig model of osteoarthritis by in vivo three-dimensional magnetic resonance imaging.

OBJECTIVE: To characterise longitudinal changes in joint integrity and cartilage volume in vivo in the guinea pig spontaneous osteoarthritis (OA) model by magnetic resonance imaging (MRI). METHODS: Guinea pigs knee were imaged in vivo by high-resolution three-dimensional (3D) MRI between the ages of 3 and 12 months. Image analysis was performed to assess qualitative knee joint changes between 3 and 12 months (n=16) and quantitative volumetric changes of the medial tibial cartilage between 9 and 12 months (n=7). After imaging, animals were killed and knees were assessed macroscopically and histologically. RESULTS: From 3 to 6 months qualitative observation by MRI and histopathology indicated localised cartilage swelling on the medial tibial plateau. At 6 months, bone cysts had developed in the epiphysis. At 9 months, we observed by MRI and histopathology, fragmentation of the medial tibial cartilage in areas not protected by the meniscus. Cartilage degeneration had intensified at 12 months with evidence of widespread loss of cartilage throughout the tibial plateau. Segmentation of the MR cartilage images showed a 36% loss of volume between 9 and 12 months. CONCLUSIONS: We have achieved 3D image acquisition and segmentation of knee cartilage in a guinea pig model of chronic OA, which permits measurements previously only possible in man. High resolution and short acquisition time allowed qualitative longitudinal characterisation of the entire knee joint and enabled us to quantify for the first time longitudinal tibial cartilage volume loss associated with disease progression.

No loss of cartilage volume over three years in patients with knee osteoarthritis as assessed by magnetic resonance imaging.

OBJECTIVE: Magnetic resonance imaging (MRI) has the potential to provide accurate quantification of structural changes in joint disease, with sensitivity to change, as it can provide direct visualization of the cartilage and bone. In this study, we investigated whether knee cartilage volume, as assessed by MRI, is sensitive to change over time in patients with osteoarthritis (OA). DESIGN: Sixteen patient volunteers (10 male, six female) with established OA of the knee were entered into the study and demographic data recorded. At baseline, 12 months and 37+/-2 months, patients underwent simple measures of disease severity, as well as extended weight-bearing AP knee X-rays. In addition the patient's index knee was imaged using MR at 1.0 T using a 3-D spoiled gradient-echo sequence with fat-suppression, repetition time 50 ms, echo time 11 ms, flip-angle 40 degrees, sagittal slice thickness 1.56 mm and in-plane pixel resolution 0.55 mm. Manual image segmentation was performed on all knee cartilage compartments and the respective cartilage volumes determined. RESULTS: Eleven of the original patients recruited completed the 3-year study. Radiographic features indicated that the majority had a spectrum of well-established OA at entry. The average decrease in medial tibiofemoral joint space width was 0.21+/-0.37 mm (mean+/-S.D.). Comparison of MR images at baseline and 37+/-2 months indicated little evidence of cartilage lesion shape or size change in any of the compartments. There was no significant MRI volume change in any of the knee cartilage compartments over the course of 1 year. The change in total knee cartilage volume, as measured by MRI, was a loss of only 1.6%, or 0.36+/-1.3 ml (mean+/-S.D.), over the 3 years. CONCLUSIONS: The failure to identify loss of cartilage volume over 3 years in this cohort of patients with established knee OA using MRI challenges the face validity of this endpoint to assess structural changes in OA.

Novel cartilage-specific splice variants of fibronectin.

OBJECTIVE: To determine the nature of alternatively spliced isoforms of fibronectin expressed in healthy bovine articular cartilage and cartilage derived from human osteoporotic and osteoarthritic joints. DESIGN: Our study focused on a single alternatively spliced region of the fibronectin gene, the variable region. Bovine cartilage samples were obtained within 12h of slaughter and human cartilage samples were obtained within 8h of the time of joint replacement surgery. RNA was extracted and alternatively spliced isoforms of fibronectin were amplified using RT-PCR. RESULTS: Two novel alternatively spliced forms of fibronectin designated (V+I-10)(-) and (V+III-15)(-) were identified in bovine articular cartilage. Fibronectin is composed of multiple repeats of three types of homologous units and these two novel isoforms specifically splice out single individual repeating units. Expression of all these isoforms was dependent upon the presence of an extracellular matrix. In the human samples the expression profiles obtained with osteoporotic hip and osteoarthritic knee cartilage was not uniform. The (V+C)(-) isoform was present in all samples and the (V+I-10)(-) isoform was distributed between both osteoporotic and osteoarthritic cartilage. However, the (V+III-15)(-) isoform was shown to be associated with osteoarthritic cartilage with statistical significance (P< 0.015 ). In addition a third novel splice variant was identified and designated as III-15X. Translation of the III-15X isoform results in a truncated form of fibronectin lacking a significant portion of the C-terminus. Further RT-PCR analysis of several other tissue types suggests that these variants are cartilage specific. CONCLUSION: Our results demonstrate the existence of three new cartilage specific isoforms of fibronectin and indicate that expression of one or more may be associated with osteoarthritis. Published by Elsevier Science Ltd. All rights reserved.

Distribution of aggrecanase (ADAMts 4/5) cleavage products in normal and osteoarthritic human articular cartilage: the influence of age, topography and zone of tissue.

OBJECTIVE: To develop and characterize a polyclonal antiserum (RAM 3.2), which recognizes the neo-C terminal cleavage product generated by the action of aggrecanase (ADAMts 4/5) on the G1-domain of human aggrecan. We also intend to use this antiserum to investigate normal, age-related changes in human articular cartilage. METHOD: The antiserum was raised in rabbits and its localization in cryosections of normal articular cartilage was investigated by immunohistochemistry. The concentration of the aggrecanase neo-epitope was also investigated in extracts of the tissue using SDS-PAGE and electrophoresis in large pore/agarose gels. RESULTS: The product of aggrecanase action appears to accumulate in the extracellular matrix during normal aging of the tissue. Furthermore, the concentration of the fragment depended on the topographical site on the femoral condyle from which the sample was selected. Electrophoretic and immunohistochemical analysis of the fragment in normal cartilage showed that in immature cartilage it was deposited mainly in the surface layers, whereas in mature samples it was distributed throughout the depth of the tissue. In contrast, immunoreactivity of osteoarthritic cartilage was always less and the distribution was more variable than in normal cartilage of the same age. CONCLUSIONS: (1) The proteolytic cleavage of aggrecan by aggrecanase is a normal homeostatic event and much of the neo-C terminal fragment produced by the enzyme is retained in the tissue. (2) The presence of this immunoreactive product in normal cartilage can be used as an indication of aggrecan turnover. (3) That in osteoarthritic cartilage there is a reduction in the concentration of the G1-fragments.