The value of cartilage biomarkers in progressive knee osteoarthritis: cross-sectional and 6-year follow-up study in middle-aged subjects.

To determine the possible diagnostic and prognostic value of cartilage biomarkers in early-stage progressive and nonprogressive knee osteoarthritis (OA) in a population-based cohort of middle-aged subjects with chronic knee pain. Design tibiofemoral (TF) and patellofemoral (PF) radiographs were graded in 128 subjects (mean age at baseline, 45 ± 6.2 years) in 2002, 2005, and 2008. Cartilage degradation was assessed by urinary C-telopeptide fragments of type II collagen (uCTx-II), synthesis by serum type II A procollagen N-terminal propeptide (sPIIANP), and articular tissue turnover in general by cartilage oligomeric matrix protein (sCOMP). Several diagnostic associations were found between all studied biomarkers and progressive osteophytosis. COMP and CTx-II had a predictive value for subsequent progressive osteophytosis in multiple knee compartments and in case of CTx-II-also for progressive JSN. Over the first 3 years (2002-2005), significant associations were observed between COMP and progressive osteophytosis, whereas 3 years later (2005-2008) between CTx-II and progressive JSN. Thus, the associations between cartilage markers (COMP, CTx-II) and progression of radiographic OA features--osteophytes and JSN--were different between 2002-2005 and 2005-2008. Logistic regression revealed that for every unit increase in COMP level, there was 33 % higher risk for TF osteophyte progression. During early-stage OA, the presence and progression of osteophytosis is accompanied by increased level of cartilage biomarkers. This is the first study to demonstrate biochemical differences over the course of knee OA, illustrating a phasic nonpersistent character of OA with periods of progression and stabilization.

The prevalence and progression of radiographic knee osteoarthritis over 6 years in a population-based cohort of middle-aged subjects.

Details of the development of early knee osteoarthritis (OA) are largely unknown. The prevalence and progression of radiographic knee OA over 6 years in middle-aged subjects with chronic knee pain is investigated. In a prospective population-based study, tibiofemoral (TF) and patellofemoral (PF) radiographs were graded in 128 subjects (mean age 45 ± 6.2 years) for the presence of osteophytes and joint space narrowing (JSN). Radiographic progression was defined as: (i) the presence of osteophytes and/or JSN in subjects with no previous OA or (ii) an increase in the grade and/or number of already existing osteophytes and/or JSN. Altogether 56% (72/128) of subjects had knee OA, the majority of them was diagnosed with OA grade 1. In 57% of cases, radiographic OA was based on the presence of osteophytes alone versus 13% on JSN. More than 1/3 of subjects had isolated PF joint involvement. Knee OA progression rate over 6 years was 56% (71/128). During 6 years, a non-linear course of radiographic OA progression with intermittent periods of progression and stabilization was observed. Individual course of OA revealed distinct subsets of radiographic progression. Osteophytosis is an important early radiographic sign of OA and its progression. Isolated PF joint involvement is a frequent expression of knee OA. In middle-aged subjects, the progression rate of knee OA over 6 years was 56%. A non-linear course of radiographic OA progression was observed. Several radiographic subsets refer to the heterogeneity of the OA process.

Genetic variation in the SMAD3 gene is associated with hip and knee osteoarthritis.

OBJECTIVE: Smad3 (or, MADH3) is a key intracellular messenger in the transforming growth factor beta signaling pathway. In mice, Smad3 deficiency accelerates growth plate chondrocyte maturation and leads to an osteoarthritis (OA)-like disease. We undertook this study to investigate the role of genetic variation in SMAD3 in the risk of large-joint OA in humans. METHODS: Ten tag single-nucleotide polymorphisms (SNPs) in the SMAD3 gene region were tested in a discovery set: 313 patients who had undergone total knee replacement, 214 patients who had undergone total hip replacement, and 520 controls from the UK. The SNP associated with both hip and knee OA was subsequently genotyped in 1,221 controls and 1,074 cases from 2 cohorts of patients with hip OA and 2,537 controls and 1,575 cases from 4 cohorts of patients with knee OA. RESULTS: A SNP (rs12901499) mapping to intron 1 of SMAD3 was associated with both knee and hip OA (P < 0.0022 and P < 0.021, respectively) in the discovery set. In all study cohorts, the major allele (G) was increased among OA patients relative to controls. A meta-analysis for knee OA yielded an odds ratio (OR) of 1.22 (95% confidence interval [95% CI] 1.12-1.34), P < 7.5 x 10(-6). For hip OA, the OR was 1.22 (95% CI 1.09-1.36), P < 4.0 x 10(-4). No evidence for heterogeneity was found (I(2) = 0%). CONCLUSION: Our data indicate that genetic variation in the SMAD3 gene is involved in the risk of both hip OA and knee OA in European populations, confirming the results from animal models on the potential importance of this molecule in the pathogenesis of OA.

Risk Assessment of the Progression of Early Knee Osteoarthritis by Collagen Neoepitope C2C: A Longitudinal Study of an Estonian Middle-Aged Cohort.

One of the unmet needs to be addressed is prognostic biomarkers for early knee osteoarthritis (kOA). We aimed to study the association of urinary collagen type-II C-terminal cleavage neoepitope (uC2C) with the emergence and progression of kOA. The longitudinal data of 330 subjects (aged 32-60 years) from an Estonian population-based cohort were used. The radiographic progression was evaluated by the grading system of Nagaosa et al. of knee compartments at baseline and three years later. The emerging kOA consisted of subjects with developing osteophytes or joint space narrowing, whereas kOA progressors showed aggravation of radiographic grade. Baseline uC2C levels were measured by the IBEX-uC2C assay. At baseline, the subjects were middle-aged (mean age, 47.6 years) and overweight (mean BMI, 28.0 kg/m2), and the majority of them (51.2%) had a diagnosis of kOA grade 1. Multiple logistic regression models adjusted for sex, age, and BMI were used for risk calculations. We demonstrate that increased uC2C accurately predicted the risk of emerging of kOA (OR = 5.87 (1.71-20.22); AUC = 0.79) compared with controls without radiographic kOA over 12 years. However, the most accurate prediction of progression by the biomarker was found in women (OR = 23.0 (2.2-245), AUC = 0.91). In conclusion, uC2C may be a promising candidate as a prognostic biomarker for kOA progression, particularly of emerging kOA in women.

Cartilage collagen neoepitope C2C in urine as an integrative diagnostic marker for early knee osteoarthritis.

Objective: To investigate the suitability of urinary collagen type-II C-terminal cleavage neoepitope (uC2C) as a marker for early knee osteoarthritis (kOA). Design: We examined 302 Estonian subjects (mean age, 49 years): 186 subjects with and 20 control subjects without knee symptoms, and 96 patients treated by arthroscopy. For the latter, cartilage lesions were characterized using Société Francaise d'Arthroscopie (SFA) scores. Standardized radiographs of bilateral tibiofemoral (TF) and patellofemoral (PF) joints were assessed for osteoarthritis (OA) features. Osteophytes (Ophs) and joint space narrowing (JSN) were graded separately. uC2C was measured by the uC2C-HUSA assay. Logistic and linear regression models were used for data analysis. Results: Of the kOA cases, 50% were isolated (TF or PF) grade 1; 10% were grade 2. JSN with Ophs was more frequent in females than in males (52% vs. 34%, p = 0.01). Increased uC2C level was associated with gradual increase in the risk of kOA grade of severity (odds ratio = 2.14-3.7) including grade 1 vs. 0. TF-OA and PF-OA equally predicted uC2C concentration (R 2 = 0.33-0.35). uC2C prediction was better for females than for males (R 2 = 0.42 vs. 0.22 by TF-OA). The best predictive model for uC2C level (R 2 = 0.75) included three OA features: macroscopic cartilage lesions, TF Ophs, and PF-JSN. Conclusions: uC2C as an integrative marker of kOA is associated with cartilage degradation and Oph formation in the PF- and TF-joints. Increased uC2C concentration could be used as an early diagnostic marker for kOA in clinical studies.

Association between ultrasonographic findings and bone/cartilage biomarkers in patients with early-stage knee osteoarthritis.

Little is known regarding the association between ultrasonographic (US) findings and biomarkers of bone and cartilage in individuals with knee osteoarthritis (OA). We investigated (1) US findings in early-stage knee OA and (2) the association between US findings and bone/cartilage biomarkers. A population cohort aged 35-55 years (n = 106) with early-stage knee OA was investigated. US examination was performed according to European League against Rheumatism (EULAR) guidelines using a 7.5-MHz probe. Biomarkers of bone resorption (CTx-I) and formation (PINP), cartilage resorption (U-CTx-II) and synthesis (S-PIIANP), and general bone and cartilage biomarkers (OC, COMP) were assessed. The most prevalent US findings were tendon calcification, synovial thickening, and suprapatellar effusion. In women, the presence of tendon calcification and Baker's cysts could predict 36% of the variability in U-CTx-II levels. The presence of osteophytes and tendon calcification predicted up to 38% of the variability of PIIANP concentration. Defects in subchondral bone, meniscal changes, and effusion predicted up to 29% of the variability in COMP levels. Tendon calcification was related to cartilage synthesis (based on PIIANP levels) in men and to cartilage degradation (based on U-CTx-II concentrations) in women. US signs of synovitis were reflected metabolically by markers of joint tissue metabolism. Tendon calcification, synovial thickening, and effusion were common US findings in early-stage knee OA. US-detectable findings were substantially responsible for the variability in bone and cartilage biomarkers, associations reflective of the active metabolism of soft tissues in early-stage OA.

The ADAM12 is upregulated in synovitis and postinflammatory fibrosis of the synovial membrane in patients with early radiographic osteoarthritis.

OBJECTIVE: To investigate the possible association between ADAM12 (disintegrin and metalloproteinase domain12) expression in the synovium and the histological synovitis of patients with radiographic knee osteoarthritis (rKOA). METHODS: The synovial biopsy samples were harvested from 44 subjects with chronic knee complaints during arthroscopy. In all subjects, the radiographs of both knee joints were performed for rKOA assessment. Histological features of synovitis were graded 0-3 in synovial samples. Messenger RNA (mRNA) of two ADAM12 splice variants [ADAM12-S(hort) and ADAM12-L(ong)] and the identical region for both-ADAM12-B(oth) were measured by real-time reverse transcription-PCR in all synovial samples (TaqMan® gene expression assay). Immunohistochemical staining of the synovial membrane with ADAM12 antibody was performed in 42 subjects. RESULTS: ADAM12 mRNA was expressed in all synovial samples, whereas the main part of overall expression consisted of its long isoform (ADAM12-L). ADAM12 protein expression was detected in 80% of the synovial samples and correlated with mRNA expression (ρ=0.30, P<0.05). The expression of ADAM12 mRNA and protein in synovium correlated with the severity of histological synovitis (ρ=0.28, P<0.05 for ADAM12-B mRNA, R2=0.20, P<0.05 for ADAM12 protein). Out of several features of synovitis the expression level of both splice variants correlated only with the grade of fibrosis in the synovium (ρ=0.30, P<0.05 for ADAM12-L and ρ=0.33, P<0.05 for ADAM12-S). CONCLUSIONS: ADAM12 is upregulated in the synovial tissue during synovitis on mRNA and protein level. We suggest that ADAM12 could be implicated in the development of KOA-associated synovitis, especially in the occurrence of postinflammatory fibrosis.

Two Single-Nucleotide Polymorphisms in ADAM12 Gene Are Associated with Early and Late Radiographic Knee Osteoarthritis in Estonian Population.

Objectives. To investigate associations of selected single-nucleotide polymorphisms (SNPs) in ADAM12 gene with radiographic knee osteoarthritis (rKOA) in Estonian population. Methods. The rs3740199, rs1871054, rs1278279, and rs1044122 SNPs in ADAM12 gene were genotyped in 438 subjects (303 women) from population-based cohort, aged 32 to 57 (mean 45.4). The rKOA features were evaluated in the tibiofemoral joint (TFJ) and patellofemoral joint. Results. The early rKOA was found in 51.4% of investigated subjects (72% women) and 12.3% of participants (63% women) had advanced stage of diseases. The A allele of synonymous SNP rs1044122 was associated with early rKOA in TFJ, predominantly with the presence of osteophytes in females (OR 1.57; 95% CI 1.08-2.29, P = 0.018). The C allele of intron polymorphism rs1871054 carried risk for advanced rKOA, mostly to osteophyte formation in TFJ in males (OR 3.03; 95% CI 1.11-7.53, P = 0.018). Also the CCAA haplotype of ADAM12 was associated with osteophytosis, again mostly in TFJ in males (P = 0.014). For rs3740199 and rs1278279, no statistically significant associations were observed. Conclusion. ADAM12 gene variants are related to rKOA risk during the early and late stages of diseases. The genetic risk seems to be predominantly associated with the appearance of osteophytes-a marker of bone remodelling and neochondrogenesis.

Large scale replication study of the association between HLA class II/BTNL2 variants and osteoarthritis of the knee in European-descent populations.

Osteoarthritis (OA) is the most common form of arthritis and a major cause of disability. This study evaluates the association in Caucasian populations of two single nucleotide polymorphisms (SNPs) mapping to the Human Leukocyte Antigen (HLA) region and deriving from a genome wide association scan (GWAS) of knee OA in Japanese populations. The frequencies for rs10947262 were compared in 36,408 controls and 5,749 knee OA cases from European-descent populations. rs7775228 was tested in 32,823 controls and 1,837 knee OA cases of European descent. The risk (major) allele at rs10947262 in Caucasian samples was not significantly associated with an odds ratio (OR)  = 1.07 (95%CI 0.94 -1.21; p = 0.28). For rs7775228 the meta-analysis resulted in OR = 0.94 (95%CI 0.81-1.09; p = 0.42) for the allele associated with risk in the Japanese GWAS. In Japanese individuals these two SNPs are in strong linkage disequilibrium (LD) (r(2) = 0.86) with the HLA class II haplotype DRB1*1502 DQA1*0103 DQB1*0601 (frequency 8%). In Caucasian and Chinese samples, using imputed data, these SNPs appear not to be in LD with that haplotype (r(2)<0.07). The rs10947262 and rs7775228 variants are not associated with risk of knee OA in European descent populations and they do not appear tag the same HLA class II haplotype as they do in Japanese individuals.