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Osteoarthritis (OA) prevalence increases as the population ages. Diagnosing osteoarthritis often occurs in the late stages when cartilage degradation is severe, making it difficult to distinguish from other types of arthritis. Accurate differentiation of primary osteoarthritis from other arthritic conditions is crucial for effective treatment planning. A new diagnostic test has been developed that uses a dual‐biomarker algorithm to inform osteoarthritis diagnosis. Synovial fluid from patients with confirmed primary osteoarthritis showed elevated levels of cartilage oligomeric matrix protein. However, this biomarker alone could not distinguish primary osteoarthritis from other inflammatory conditions that also cause cartilage deterioration. Therefore, a combinatorial algorithm using cartilage oligomeric matrix protein and Interleukin‐8 concentrations was developed to differentiate primary osteoarthritis from inflammatory arthritis. Clinical decision limits for cartilage oligomeric matrix protein concentration and the cartilage oligomeric matrix protein to Interleukin‐8 ratio were established and validated using 171 human knee synovial fluid specimens. The osteoarthritis algorithm demonstrated clinical sensitivity and specificity of 87.0% and 88.9%, respectively. This is the first report of a biomarker test that can differentiate primary osteoarthritis from inflammatory arthritis with a high degree of accuracy. Clinical Significance: This study introduces a novel dual‐biomarker algorithm utilizing synovial fluid analysis, offering a significant advancement in accurately diagnosing osteoarthritis, particularly in distinguishing it from inflammatory arthritis. This approach holds promise for improving clinical decision‐making and patient outcomes, addressing a critical unmet need in arthritis diagnosis. [ABSTRACT FROM AUTHOR]

Objective·To further clarify the mechanism of podocyte damage by studying the expression of cartilage oligomeric matrix protein (COMP) in glomerular podocytes and its relationship with podocyte autophagy under high glucose environment.Methods·The gene expression dataset GSE104948 was downloaded from the GENE EXPRESSION OMNIBUS (GEO) database, and differentially expressed genes (DEGs) were obtained via GEO2R. The molecular functions and signaling pathways related to differential genes were summarized. The most correlated key genes (hub genes) were acquired by Weighted Gene Co-Expression Network Analysis (WGCNA) and the protein-protein interaction network (PPI) of DEGs was constructed with STRING database. The enrichment analysis was performed again. Conditionally immortalized mouse podocyte cells were cultured in vitro. After being fully differentiated, they were stimulated with high glucose, and the expressions of COMP, mammalian target of rapamycin (mTOR), microtubule-associated protein 1 light chain3 (LC3) and other proteins in podocytes were detected by Western blotting. The shRNA constructed by lentiviral vector was further used to infect podocytes to inhibit the expression of COMP, and the stable cell strains were screened by puromycin. The expression of COMP, mTOR, and LC3 of stable strains were detected by Western blotting, in order to observe the effect of COMP on autophagy.Results·A total of 362 DEGs were filtered for subsequent analysis. Among these DEGs, 284 genes were up-regulated and 78 genes were down-regulated. The results of Gene Onotology (GO) term analysis showed that DEGs in diabetic nephropathy (DN) were mainly enriched in cell surface receptor signaling pathway, receptor binding, etc. The main enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways included phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) signaling pathway, extracellular matrix (ECM)-receptor interaction, etc. Sixty-four hub genes were refined through the intersection of WGCNA and PPI hub genes, and the hub genes with significantly increased or decreased expression were sifted. The hub genes were annotated with KEGG again, and it was found that most of the hub genes were enriched in "ECM-receptor interaction" and "PI3K/AKT signaling pathway". The PI3K/AKT/mTOR signaling pathway is a classic autophagy pathway, and COMP was absolutely overexpressed (logFC>2) in the 64 hub genes, suggesting that it may affect autophagy through this pathway. Western blotting showed that compared with the mannitol control group and the low glucose group, the expression of COMP in podocytes was significantly increased under high glucose stimulation. Compared with the control group, the expression of LC3-II in the high glucose group was significantly decreased, indicating that the autophagy initiation of podocytes was inhibited under the high glucose environment. Compared with the negative control, the expression of LC3-II in renal podocytes of mice with knockdown of COMP was significantly increased, and the mTOR decreased with the decrease of the expression of COMP, indicating that inhibiting COMP contributed to the recovery of autophagy in podocytes.Conclusion·COMP is highly expressed in DN patients and highly enriched in ECM receptor and PI3K/AKT signaling pathway. Autophagy in mouse renal podocytes is inhibited under high glucose conditions, and the high expression of COMP induced by high glucose may be a key factor in autophagy inhibition. Inhibiting COMP helps to restore autophagy in mouse renal podocytes.

Abstract Objective Intervertebral disc degeneration (IVDD) is a major cause of morbidity and disability. Our study aimed to investigate the potential of cartilage oligomeric matrix protein (COMP) and ADAMTS7 (A disintegrin and metalloproteinases with thrombospondin motifs 7) as biomarkers for IVDD together with their functional relationship. Methods IVD tissues and peripheral blood samples were collected from IVDD rabbit models over 1–4 weeks. Tissues and blood samples were also collected from clinical patients those were stratified into four equal groups according to Pfirrmann IVDD grading (I–V) with baseline data collected for each participant. COMP and ADAMTS7 expression were analyzed and biomarker characteristics were assessed using linear regression and receiver operating curve (ROC) analyses. Results COMP and ADAMTS7 expression increased in tissues and serum during IVDD progression. Serum COMP (sCOMP) and serum ADAMTS7 (sADAMTS7) levels increased in a time-dependent manner following IVD damage in the rabbit model while significant positive correlations were detected between sCOMP and sADAMTS7 and Pfirrmann grade in human subjects. ROC analysis showed that combining sCOMP and sADAMTS7 assay results produced an improved diagnostic measure for IVDD compared to individual sCOMP or sADAMTS7 tests. In vitro assays conducted on human cell isolates revealed that COMP prevented extracellular matrix degradation and antagonized ADAMTS7 expression although this protective role was uncoupled under microenvironmental conditions mimicking IVDD. Conclusions Increases in circulating COMP and ADAMTS7 correlate with IVDD progression and may play regulatory roles. Assays for sCOMP and/or sADAMTS7 levels can discriminate between healthy subjects and IVDD patients, warranting further clinical assessment.

Objective: Intervertebral disc degeneration (IVDD) is a major cause of morbidity and disability. Our study aimed to investigate the potential of cartilage oligomeric matrix protein (COMP) and ADAMTS7 (A disintegrin and metalloproteinases with thrombospondin motifs 7) as biomarkers for IVDD together with their functional relationship. Methods: IVD tissues and peripheral blood samples were collected from IVDD rabbit models over 1–4 weeks. Tissues and blood samples were also collected from clinical patients those were stratified into four equal groups according to Pfirrmann IVDD grading (I–V) with baseline data collected for each participant. COMP and ADAMTS7 expression were analyzed and biomarker characteristics were assessed using linear regression and receiver operating curve (ROC) analyses. Results: COMP and ADAMTS7 expression increased in tissues and serum during IVDD progression. Serum COMP (sCOMP) and serum ADAMTS7 (sADAMTS7) levels increased in a time-dependent manner following IVD damage in the rabbit model while significant positive correlations were detected between sCOMP and sADAMTS7 and Pfirrmann grade in human subjects. ROC analysis showed that combining sCOMP and sADAMTS7 assay results produced an improved diagnostic measure for IVDD compared to individual sCOMP or sADAMTS7 tests. In vitro assays conducted on human cell isolates revealed that COMP prevented extracellular matrix degradation and antagonized ADAMTS7 expression although this protective role was uncoupled under microenvironmental conditions mimicking IVDD. Conclusions: Increases in circulating COMP and ADAMTS7 correlate with IVDD progression and may play regulatory roles. Assays for sCOMP and/or sADAMTS7 levels can discriminate between healthy subjects and IVDD patients, warranting further clinical assessment. [ABSTRACT FROM AUTHOR]

• When expressed in E. coli inclusion bodies, Stx1B and Stx2B formed pentamers. • Stx1B pentamer protected mice against Stx1 challenge. • Stx2B pentamer did not protect mice against Stx2 challenge. • Stx2B pentamer was leashed and bundled by a pentameric coiled-coil domain. • This form of Stx2B pentamer protected mice against Stx2 challenge. Vaccines against Shiga toxin (Stx)-producing Escherichia coli (STEC) have not yet been developed. Two immunologically distinct serotypes of Stx (Stx1 and Stx2) are the main virulence factors of STEC. Thus, blocking their B subunits (StxB) from binding to the cell surface receptor globotriaosylceramide (Gb3) efficiently prevents the action of these toxins. We expressed Stx1B and Stx2B in E. coli inclusion bodies and reassembled them into pentamers by a stepwise dialysis. Stx1B pentamer fully protected mice against Stx1 challenge, but Stx2B pentamer failed to protect mice against Stx2 challenge. To explain those observations, we proposed that the pentamer of Stx2B readily dissociates into its constituent monomers, especially under in vivo conditions, thus being unable to induce pentamer-specific immunity. To increase pentamer stability, we fused the B subunit to a pentameric coiled-coil domain of the cartilage oligomeric matrix protein (COMP). This "five-to-five" fusion hybrid molecule (Stx2B–COMP) was shown to be protective against Stx2 challenge, demonstrating that the Stx2B subunit when leashed and bundled by a rigid pentameric coiled-coil domain mount a pentamer-specific immune response and efficiently neutralize the toxin both in vitro and in vivo. Our data strongly suggest that the Stx2B subunit moiety fluctuates between a pentameric and monomeric state within the fusion protein, which may increase the likelihood of the immune system recognizing the pentameric conformation for toxin neutralization. [ABSTRACT FROM AUTHOR]

Background: The protein encoded by the cartilage oligomeric matrix protein (COMP) gene is a noncollagenous extracellular matrix (ECM) protein that is important for chondrocyte formation and growth. Variations in the COMP gene cause pseudoachondroplasia (PSACH), which is mainly characterized by short‐limbed dwarfing in the clinic. Aims: To characterize the function of a rare pathogenic variant in the COMP gene (c.875G > A, p.Cys292Tyr). Materials & Methods: We performed 3D structural analysis, in vitro expression analysis, and immunofluorescence to characterize the effects of the variant on protein structure, expression, and cellular localization respectively. Results: Variation modeling showed that the interactions between amino acids were changed after the variation, and there were 31 changes in the secondary structure of mutant COMP (MT‐COMP). Western blot showed that the intracellular quantity of MT‐COMP was higher than the wild‐type COMP (WT‐COMP). Cellular immunofluorescence results showed that WT‐COMP was less abundant and homogenously distributed in cells, while the MT‐COMP accumulated in the cytoplasm. Discussion: Herein, we report a variant of COMP in a Chinese family with PSACH. We have shown that the rare missense variant, COMP c.875G > A, previously reported in ClinVar and identified in our patient, results in excessive accumulation of mutant protein in the cytoplasm, and is therefore pathogenic. Conclusion: Through in silico and experimental analyses, we provide evidence that COMP c.875G > A is the likely cause of PSACH in a Chinese family. [ABSTRACT FROM AUTHOR]

Introduction: Cartilage Oligomeric Matrix Protein (COMP) is an oncogenic protein that has been associated with a decrease in infiltrating T-cells in periampullary adenocarcinoma. This study aimed to investigate whether this is also the case for colorectal cancer (CRC) and to evaluate the relationship between COMP expression and clinopathological features Methods: Immunohistochemistry was used to determine the expression levels of COMP in tumor cells and stroma in primary tumors from a cohort of 537 CRC patients. The expression of immune cell markers, including CD3+, CD8+, FoxP3+, CD68+, CD56+, CD163+, and PD-L1, was evaluated previously. Tumor fibrosis was assessed by Sirius Red staining and evaluation of collagen fiber organization. Results: COMP expression correlated positively with TNM-stage and grade of differentiation. Patients with CRC expressing high levels of COMP had significantly shorter OS than those with low COMP expression (p<0.0001), and fewer infiltrating T-cells were detected in tumors with high COMP expression. Additionally, a negative correlation was identified between the expression of COMP and PD-L1 on both tumor cells and immune cells. Cox regression analysis showed that tumors expressing high levels of COMP had significantly shorter OS, independent of all evaluated immune cell markers. Tumor fibrosis was correlated with high expression of COMP in the stroma (p<0.0001), and tumors with high levels of COMP expression and denser fibrosis displayed more sparse immune cell infiltration. Discussion: The results suggest that COMP expression in CRC may exert an immune regulatory effect by increasing dense fibrosis and decreasing immune cell infiltration. These findings support the notion that COMP is an important factor in the development and progression of CRC. [ABSTRACT FROM AUTHOR]

IntroductionCartilage Oligomeric Matrix Protein (COMP) is an oncogenic protein that has been associated with a decrease in infiltrating T-cells in periampullary adenocarcinoma. This study aimed to investigate whether this is also the case for colorectal cancer (CRC) and to evaluate the relationship between COMP expression and clinopathological features.MethodsImmunohistochemistry was used to determine the expression levels of COMP in tumor cells and stroma in primary tumors from a cohort of 537 CRC patients. The expression of immune cell markers, including CD3+, CD8+, FoxP3+, CD68+, CD56+, CD163+, and PD-L1, was evaluated previously. Tumor fibrosis was assessed by Sirius Red staining and evaluation of collagen fiber organization.ResultsCOMP expression correlated positively with TNM-stage and grade of differentiation. Patients with CRC expressing high levels of COMP had significantly shorter OS than those with low COMP expression (p

Purpose: The main function of cartilage oligomeric matrix protein (COMP) is to maintain the synthesis and stability of the extracellular matrix by interacting with collagen. At present, there are relatively few studies on the role of this protein in tumors. This study aimed to explore the relationship between COMP and pan-cancer, and analyzed its diagnostic and prognostic value. Methods: The Cancer Genome Atlas database, the Genotype-Tissue Expression database and the Cancer Cell Line Encyclopedia database was used for gene expression analysis. The receiver operating characteristic curve was used to assess the diagnostic value of COMP in pan-cancer. Kaplan–Meier plots were used to assess the relationship between COMP expression and prognosis of cancers. R software v4.1.1 was used for statistical analysis, and the ggplot2 package was used for visualization. Results: COMP was significantly overexpressed in 15 human cancers and showed significantly difference in 12 molecular subtypes and 16 immune subtypes. In addition, the expression of COMP is associated with tumor immune evasion. The ROC curve showed that the expression of COMP could predict the occurrence of 16 kinds of tumors with relative accuracy, including adrenocortical carcinoma (ACC) (AUC = 0.737), breast invasive carcinoma (BRCA) (AUC = 0.896), colon adenocarcinoma (COAD) (AUC = 0.760), colon adenocarcinoma/rectum adenocarcinoma esophageal carcinoma (COADREAD) (AUC = 0.775), lymphoid neoplasm diffuse large B-cell lymphoma (DLBC) (AUC = 0.875), kidney renal papillary cell carcinoma (KIRP) (AUC = 0.773), kidney chromophobe (KICH) (AUC = 0.809), ovarian serous cystadenocarcinoma (OV) (AUC = 0.906), prostate adenocarcinoma (PRAD) (AUC = 0.721), pancreatic adenocarcinoma (PAAD) (AUC = 0.944), rectum adenocarcinoma (READ) (AUC = 0.792), skin cutaneous melanoma (SKCM) (AUC = 0.746), stomach adenocarcinoma (STAD) (AUC = 0.711), testicular germ cell tumors (TGCT) (AUC = 0.823), thymoma (THYM) (AUC = 0.777) and uterine carcinosarcoma (UCS) (AUC = 0.769). Furthermore, COMP expression was correlated with overall survival (OS), disease-specific survival (DSS) and progression-free interval (PFI) in ACC (OS, HR = 4.95, DSS, HR = 5.55, PFI, HR = 2.79), BLCA (OS, HR = 1.59, DSS, HR = 1.72, PFI, HR = 1.36), KIRC (OS, HR = 1.36, DSS, HR = 1.94, PFI, HR = 1.57) and COADREAD (OS, HR = 1.46, DSS, HR = 1.98, PFI, HR = 1.43). We selected previously unreported bladder urothelial carcinoma (BLCA) for further study and found that COMP could be an independent risk factor for OS, DSS and PFI. Moreover, we found differentially expressed genes of COMP in BLCA and obtained top 10 hub genes, including LGR4, LGR5, RSPO2, RSPO1, RSPO3, RNF43, ZNRF3, FYN, LYN and SYK. Finally, we verified the function of COMP at the cellular level by using J82 and T24 cells and found that knockdown of COMP could significantly inhibit migration and invasion. This finding supports that COMP could be a potential biomarker for pan-cancer diagnosis and prognosis encompassing tumor microenvironment, disease stage and prognosis. Conclusion: This finding supports that COMP could be a potential biomarker for pan-cancer diagnosis and prognosis encompassing tumor microenvironment, disease stage and prognosis. [ABSTRACT FROM AUTHOR]

Cartilage oligomeric matrix protein (COMP) was a protective factor in the cardiovascular system. Previous studies showed that hypoxia led to decreased COMP in rat models of pulmonary hypertension. However, the expression pattern of COMP in the pulmonary hypertension population was unclear. A total of 35 patients newly diagnosed with pulmonary hypertension and 70 controls were enrolled in the study. Circulating COMP concentrations of serum samples were measured by enzyme‐linked immunosorbent assay and were analyzed the association with multiple clinical variables. Serum COMP concentrations in the pulmonary hypertension group were significantly declined in comparison with age‐ and sex‐matched normal controls, especially in the female subgroup. No significant difference of COMP concentrations was observed in the etiological classification, heart function classification, and risk stratification. Major hemodynamic parameters, six‐minute walk distance, N‐terminal pro brain natriuretic peptide, and short‐term prognosis were not statistically associated with COMP. However, some echocardiography parameters, like tricuspid annular plane systolic excursion and mean right atrial pressure, were found the negative relation to COMP concentrations. In conclusion, serum COMP levels were decreased in the patients with pulmonary hypertension, which was in accordance with its known biological effects. Its association with long‐term prognosis was worth further exploring.

Background: Accumulating evidence shows that pleomorphic adenoma (PA) exhibits a unique capsular invasion and with a crucial role in recurrence. This study was designed to explore RNA expression profiles in salivary gland PA in an attempt to further analyse genes associate with capsule invasion. Methods: We evaluated the expression profiles of 4 salivary gland PA patients by RNA‐sequencing. The principal functions of the differentially expressed mRNAs (DEGs) were explored using GO and KEGG analysis. Then, RT‐qPCR and correlation analyses were performed to verify the candidate DEGs in 59 PA patients, and immunohistochemical examinations were conducted to validate candidate DEGs. Finally, the COMP‐related genes were screened using correlation and biological pathway enrichment analysis, and further validated by RT‐qPCR. Results: A total of 974 DEGs were significantly upregulated, and 1464 were downregulated (fold change ≥2.0; p < 0.05). Based on GO and KEGG analyses, extracellular matrix organization and the PI3K‐Akt signalling pathway might play pivotal roles in the tumorigenesis of PA. 40 DEGs were screened and validated by RT‐qPCR, 11 upregulated and 5 downregulated DEGs were consistent with the sequencing results. Cartilage oligomeric matrix protein (COMP) was identified to have a significant correlation with the capsular invasion of PA and expression of COMP in patients with invasive capsular PA was significantly stronger than PA. Finally, further results could reveal that 5 highest scoring genes were screened as hub genes for COMP. Conclusions: These findings suggested that COMP may be a prognostic target for PA and might contribute to its capsular invasion. [ABSTRACT FROM AUTHOR]

Abstract Background Multiple epiphyseal dysplasia (MED) is a skeletal disorder characterized by delayed and irregular ossification of the epiphyses and early-onset osteoarthritis. At least 66% of the reported autosomal dominant MED (AD-MED) cases are caused by COMP mutations. Methods We recruited a four-generation Chinese family with early-onset hip osteoarthritis, flatfoot, brachydactyly, and mild short stature. An assessment of the family history, detailed physical examinations, and radiographic evaluations were performed on the proband and other family members, followed by the performance of whole-exome sequencing (WES). The pathogenicity of the candidate mutation was also analyzed. Results An AD-MED family with 10 affected members and 17 unaffected members was recruited. The main radiographic findings were symmetrical changes in the dysplastic acetabulum and femoral heads, irregular contours of the epiphyses, a shortened femoral neck, and flatfoot. Lower bone density was also observed in the ankle joints, wrist joints, and knees, as well as irregular vertebral end plates. In the proband, we identified the missense mutation c.1153G > T (p. Asp385Tyr), located in exon 11 of the COMP gene. This mutation was assessed as 'pathogenic' because of its low allele frequency and its high likelihood of co-segregation with disease in the reported family. Sanger sequencing validated the novel heterozygous mutation c.1153G > T (p. Asp385Tyr) in exon 11 of COMP in all affected individuals in the family. Conclusions Our results underlined a key role of the Asp385 amino acid in the protein function of COMP and confirmed the pathogenicity of the COMP (c.1153G > T; p. Asp385Tyr) mutation in AD-MED disease. We have therefore expanded the known mutational spectrum of COMP and revealed new phenotypic information for AD-MED.

Aim: comparative assessment of the state of joint (hyaline) cartilage, pro-inflammatory component of cytokine profile and enzyme element of blood antioxidant system in healthy individuals and patients at the early stages of gonarthrosis. Materials and Methods. The content of cartilage oligomeric matrixprotein (COMP), superoxide dismutase-2 (mitochondrial) (SOD-2) and interleukin-1 (3 (IL-1 (3) was studied in 34 individuals with initial signs of gonarthrosis (main group) and in 20 conventionally healthy individuals (control group) in blood serum by ELISA. Results. In the serum of patients with GA, the content of COMP (Me=20.67 pg/ml; 25% quartile 14.70; 75% quartile 27.15) and IL-1(3 (Me=4.74 pg/ml; 25% quartile 3.93; 75% quartile 5.90) was statistically significantly higher (p

Background: Multiple epiphyseal dysplasia (MED) is a skeletal disorder characterized by delayed and irregular ossification of the epiphyses and early-onset osteoarthritis. At least 66% of the reported autosomal dominant MED (AD-MED) cases are caused by COMP mutations. Methods: We recruited a four-generation Chinese family with early-onset hip osteoarthritis, flatfoot, brachydactyly, and mild short stature. An assessment of the family history, detailed physical examinations, and radiographic evaluations were performed on the proband and other family members, followed by the performance of whole-exome sequencing (WES). The pathogenicity of the candidate mutation was also analyzed. Results: An AD-MED family with 10 affected members and 17 unaffected members was recruited. The main radiographic findings were symmetrical changes in the dysplastic acetabulum and femoral heads, irregular contours of the epiphyses, a shortened femoral neck, and flatfoot. Lower bone density was also observed in the ankle joints, wrist joints, and knees, as well as irregular vertebral end plates. In the proband, we identified the missense mutation c.1153G > T (p. Asp385Tyr), located in exon 11 of the COMP gene. This mutation was assessed as 'pathogenic' because of its low allele frequency and its high likelihood of co-segregation with disease in the reported family. Sanger sequencing validated the novel heterozygous mutation c.1153G > T (p. Asp385Tyr) in exon 11 of COMP in all affected individuals in the family. Conclusions: Our results underlined a key role of the Asp385 amino acid in the protein function of COMP and confirmed the pathogenicity of the COMP (c.1153G > T; p. Asp385Tyr) mutation in AD-MED disease. We have therefore expanded the known mutational spectrum of COMP and revealed new phenotypic information for AD-MED. [ABSTRACT FROM AUTHOR]

Background: Serum cartilage oligomeric matrix protein (COMP) is a non-collagen glycoprotein produced by the cartilage, synovium, tendon, and meniscus. Recent studies showed that COMP is a reliable factor for monitoring cartilage damage. Objective: To determine the relationship between serum COMP concentration and the severity of rheumatoid arthritis (RA). Methods: This cross-sectional study lasted from 2013 to 2015 at the Rheumatology Clinic of Ghaem Hospital, Mashhad, Iran. The study population consisted of eligible patients who presented to our clinic during the study period. Four groups (150 subjects) were included as early RA (50 patients), late RA (50 patients), grades II and III OA (osteoarthritis) (25 cases, 17 grade II and 8 grade III joint destruction), and healthy controls (25 individuals). These were included consecutively. Serum COMP level was assessed by sandwich ELISA technique. In addition, ESR, hs-CRP, serum RF, and anti-CCP were assayed. X-rays of the knees (in OA) and hands (in RA) were examined for the degree of joint damage/erosion using the Short Erosion Scale (SES) in RA and Kellgren-Lawrence grading in OA. Analysis of variance (ANOVA) to compare mean COMP level among the groups and ROC (Receiver Operating Characteristic) analysis to determine the diagnostic accuracy of COMP in diagnosis of late RA were used by SPSS software (ver. 20.0). Results: Mean (±SD) serum COMP levels were 18 (±10.6) U/L in early RA, 19.3 (±9.6) U/L in late RA, 10.9 (±4.5) U/L in OA, and 4.2 (±3.8) in controls; p

The purpose of this work was to establish, whether rat chondrocyte associated antigen, transmembrane Tmp21 protein belonging to the p24 protein family may immunize rats and thus be included into the panel of immunogens potentially involved in cartilage pathology. For immunization of rats extract from cultured chondrocytes containing surface chondrocyte proteins suspended in incomplete Freund's adjuvant was used. Control animals were injected with incomplete Freund's adjuvant without chondrocyte extract. Morphological observations indicated that both in control and experimental animals occurred subperiosteal resorption of bone, suggesting that it arised as the response to adjuvant. In trachea, however, resorption of cartilage and inflammatory changes in the respiratory epithelium and lamina propria were present only in animals exposed to antigen. Unexpectedly, sera from immunized rats strongly reacted with other antigen, which we were able to identify by Western blot and protein sequencing as cartilage oligomeric matrix protein (COMP). COMP is attached to chondrocyte membrane by integrins and its presence in chondrocyte extract is not surprising. Antibody response to COMP raises a question whether the observed changes in tracheal cartilage and epithelium represent anti-COMP reaction or were caused by some other, no specified factors. COMP is used as the marker of osteoarthritis progression, but its role in polychondritis, cartilage pathology involving i.a. tracheal cartilage resorption remains unknown. Thus, our observations may serve as the starting point for future studies in this direction. [ABSTRACT FROM AUTHOR]

Current methods for diagnosing early stage osteoarthritis (OA) based on the magnetic resonance imaging and enzyme-linked immunosorbent assay methods are specific, but require specialized laboratory facilities and highly trained personal to obtain a definitive result. In this work, a user friendly and non-invasive quartz crystal microbalance (QCM) immunosensor method has been developed to detect Cartilage Oligomeric Matrix Protein (COMP) for early stage OA diagnosis. This QCM immunosensor was fabricated to immobilize COMP antibodies utilizing the self-assembled monolayer technique. The surface properties of the immunosensor were characterized by its FTIR and electrochemical impedance spectra (EIS). The feasibility study was based on urine samples obtained from 41 volunteers. Experiments were carried out in a flow system and the reproducibility of the electrodes was evaluated by the impedance measured by EIS. Its potential dynamically monitored the immunoreaction processes and could increase the efficiency and sensitivity of COMP detection in laboratory-cultured preparations and clinical samples. The frequency responses of the QCM immunosensor changed from 6 kHz when testing 50 ng/mL COMP concentration. The linear regression equation of frequency shift and COMP concentration was determined as: y = 0.0872 x + 1.2138 (R2 = 0.9957). The COMP in urine was also determined by both QCM and EIS for comparison. A highly sensitive, user friendly and cost effective analytical method for the early stage OA diagnosis has thus been successfully developed.

Aim of the work The objective of our study was to determine the utility of serum cartilage oligomeric matrix protein (COMP) as a serum biomarker for hemophilic arthropathy and to evaluate the degree of joint damage radiologically using plain X-ray and functionally using functional independence score of hemophilia (FISH) and to study their relation with COMP. Patients and methods The study was carried out on 30 boys with hemophilic arthropathy (group I) and 20 healthy boys as control (group II). All hemophiliacs patients were scored for FISH and radiological changes (Pettersson’s score). Factor activity level was measured in group I while COMP was measured in both groups. Results The patients’ age ranged from 6 to 16 years (mean 10.6 ± 2.7 years). The knee was the most commonly affected joint (83.3%). Fifteen patients (50%) had severe hemophilia, 7 had moderate and 8 had mild hemophilia. Mean serum levels of COMP in hemophilic patients (529 ± 288.1 ng/ml) were significantly higher than in control (285 ± 63.2 ng/ml) ( p = 0.014). The COMP level was significantly higher in patients with severe hemophilia compared to those with moderate or mild disease ( p < 0.001). The serum COMP significantly correlated with joint space narrowing ( r = 0.64, p < 0.001) and with the total Pettersson score ( r = 0.42, p = 0.02) and negatively with the FISH score ( r = −0.44, p = 0.016). Conclusions Serum COMP level is indicative of the amount of joint damage in patients with hemophilic arthropathy. The combined scoring of functional independence and Pettersson score in addition to serum levels of COMP give a good overview of the degree of hemophilic arthropathy. [ABSTRACT FROM AUTHOR]

Abstract: Although effective therapies for haemophilia have been available for decades, the prevention and treatment of joint disease remain major clinical concerns for all haemophilia patients. Early identification of joint disease is vital to initiate or modify treatment, and prevent arthropathy. However, there remains a need for more sensitive and accurate methods, which may also detect improvement in patient outcome with new therapies or different prophylaxis regimens. These topics were explored at the Ninth Zürich Haemophilia Forum. A summary of our shared views on the limitations of current assessment methods, and the potential advantages of more recently developed tools, is provided. Ultrasonography enables more frequent routine monitoring and the early detection of joint disease. In addition, serological markers may provide suitable biomarkers of early arthropathy. To prevent arthropathy, in our opinion, prophylaxis is key to prevent joint bleeds and subsequent initiation of the ’vicious circle of joint disease’. However, issues remain, including when prophylaxis should be started, stopped, and if it is efficacious for inhibitor patients. Once joint bleeding has occurred, enhanced on-demand treatment should be considered. For more advanced stages of joint disease, the issues regarding the treatment options available are explored. Radiosynovectomy should be performed to treat chronic synovitis, and may prevent the need for elective orthopaedic surgery (EOS). Ultimately, however, EOS can be considered once all other treatment options have been explored. While, bypassing agents have facilitated the use of EOS in inhibitor patients, a multidisciplinary approach and careful surveillance is required for good patient outcome. [Copyright &y& Elsevier]

Abstract: Osteoarthritis (OA) is characterized by remodeling and degradation of joint tissues. Microarray studies have led to a better understanding of the molecular changes that occur in tissues affected by conditions such as OA; however, such analyses are limited to the identification of a list of genes with altered transcript expression, usually at a single time point during disease progression. While these lists have identified many novel genes that are altered during the disease process, they are unable to identify perturbed relationships between genes and gene products. In this work, we have integrated a time course gene expression dataset with network analysis to gain a better systems level understanding of the early events that occur during the development of OA in a mouse model. The subnetworks that were enriched at one or more of the time points examined (2, 4, 8, and 16weeks after induction of OA) contained genes from several pathways proposed to be important to the OA process, including the extracellular matrix–receptor interaction and the focal adhesion pathways and the Wnt, Hedgehog and TGF-β signaling pathways. The genes within the subnetworks were most active at the 2 and 4week time points and included genes not previously studied in the OA process. A unique pathway, riboflavin metabolism, was active at the 4week time point. These results suggest that the incorporation of network-type analyses along with time series microarray data will lead to advancements in our understanding of complex diseases such as OA at a systems level, and may provide novel insights into the pathways and processes involved in disease pathogenesis. [Copyright &y& Elsevier]

Abstract: During chondrogenesis, complex intracellular signalling pathways regulate an intricate series of events including condensation of chondroprogenitor cells and nodule formation followed by chondrogenic differentiation. Reversible phosphorylation of key target proteins is of particular importance during this process. Among protein kinases known to be involved in these pathways, protein kinase C (PKC) subtypes play pivotal roles. However, the precise function of PKC isoenzymes during chondrogenesis and in mature articular chondrocytes is still largely unclear. In this review, we provide a historical overview of how the concept of PKC-mediated chondrogenesis has evolved, starting from the first discoveries of PKC isoform expression and activity. Signalling components upstream and downstream of PKC, leading to the stimulation of chondrogenic differentiation, are also discussed. Although it is evident that we are only at the beginning to understand what roles are assigned to PKC subtypes during chondrogenesis and how they are regulated, there are many yet unexplored aspects in this area. There is evidence that calcium signalling is a central regulator in differentiating chondroprogenitors; still, clear links between intracellular calcium signalling and prototypical calcium-dependent PKC subtypes such as PKCalpha have not been established. Exploiting putative connections and shedding more light on how exactly PKC signalling pathways influence cartilage formation should open new perspectives for a better understanding of healthy as well as pathological differentiation processes of chondrocytes, and may also lead to the development of novel therapeutic approaches. [Copyright &y& Elsevier]

Abstract: Synaptic dysfunction has recently gained attention for its involvement in mood disorders. Electroconvulsive therapy (ECT) possibly plays a role in synaptic repair. However, the underlying mechanisms remain uncertain. Thrombospondin-1 (TSP-1), a member of the TSP family, is reported to be secreted by astrocytes and to regulate synaptogenesis. We investigated the effects of electroconvulsive seizure (ECS) on the expression of TSPs in the adult rat hippocampus. Single and repeated ECS significantly increased TSP-1 mRNA expression after 2h and returned to sham levels at 24h. Conversely, the TSP-2 and -4 mRNA levels did not change. Only repeated ECS induced TSP-1 proteins. ECS also induced glial fibrillary acidic protein (GFAP) expression. The GFAP expression occurred later than the TSP-1 mRNA expression following single ECS; however, it occurred earlier and was more persistent following repeated ECS. ECS had no effect on the α2δ-1 or neuroligin-1 expressions, both of which are TSP-1 receptors. Furthermore, chronic treatment with antidepressants did not induce the expression of TSP-1 or GFAP. These findings suggest that repeated ECS, but not chronic treatment with antidepressants, induces TSP-1 expression partially via the activation of astrocytes. Therefore, TSP-1 is possibly involved in the synaptogenic effects of ECS. [Copyright &y& Elsevier]

Abstract: Skin fibrosis is characterized by activated fibroblasts and an altered architecture of the extracellular matrix. Excessive deposition of extracellular matrix proteins and altered cytokine levels in the dermal collagen matrix are common to several pathological situations such as localized scleroderma and systemic sclerosis, keloids, dermatosclerosis associated with venous ulcers and the fibroproliferative tissue surrounding invasively growing tumors. Which factors contribute to altered organization of dermal collagen matrix in skin fibrosis is not well understood. We recently demonstrated that cartilage oligomeric matrix protein (COMP) functions as organizer of the dermal collagen I network in healthy human skin (Agarwal et al., 2012). Here we show that COMP deposition is enhanced in the dermis in various fibrotic conditions. COMP levels were significantly increased in fibrotic lesions derived from patients with localized scleroderma, in wound tissue and exudates of patients with venous leg ulcers and in the fibrotic stroma of biopsies from patients with basal cell carcinoma. We postulate enhanced deposition of COMP as one of the common factors altering the supramolecular architecture of collagen matrix in fibrotic skin pathologies. Interestingly, COMP remained nearly undetectable in normally healing wounds where myofibroblasts transiently accumulate in the granulation tissue. We conclude that COMP expression is restricted to a fibroblast differentiation state not identical to myofibroblasts which is induced by TGFβ and biomechanical forces. [Copyright &y& Elsevier]

BACKGROUND: To understand cartilage oligomeric matrix protein (COMP) mechanism network from human normal adjacent tissues to lung adenocarcinoma. METHODS: COMP complete different activated (all no positive correlation, Pearson CC < 0.25) and uncomplete (partly no positive correlation except COMP, Pearson CC < 0.25) network were identified in higher lung adenocarcinoma compared with lower human normal adjacent tissues from the corresponding COMP-stimulated (&nvge;0.25) or inhibited (Pearson CC ≤ -0.25) overlapping molecules of Pearson correlation coefficient (CC) and GRNInfer, respectively. COMP complete different activated and inhibited (all no positive correlation, Pearson CC < 0.25) mechanisms networks of higher lung adenocarcinoma and lower human normal adjacent tissues were constructed by integration of Pearson CC, GRNInfer and GO. As visualized by integration of GO, KEGG, GenMAPP, BioCarta and Disease, we deduced COMP complete different activated and inhibited network in higher lung adenocarcinoma and lower human normal adjacent tissues. RESULTS: As visualized by GO, KEGG, GenMAPP, BioCarta and disease database integration, we proposed mainly that the mechanism and function of COMP complete different activated network in higher lung adenocarcinoma was involved in COMP activation with matrix-localized insulin-like factor coupling carboxypeptidase to metallopeptidase-induced proteolysis, whereas the corresponding inhibited network in lower human normal adjacent tissues participated in COMP inhibition with nucleus-localized vasculogenesis, B and T cell differentiation and neural endocrine factors coupling pyrophosphatase-mediated proteolysis. However, COMP complete different inhibited network in higher lung adenocarcinoma included COMP inhibition with nucleus-localized chromatin maintenance, licensing and assembly factors coupling phosphatase-inhibitor to cytokinesis regulators-mediated cell differentiation, whereas the corresponding activated network in lower human normal adjacent tissues contained COMP activation with cytolplasm-localized translation elongation factor coupling fucosyltransferase to ubiquitin-protein ligase-induced cell differentiation. CONCLUSION: COMP different networks were verified not only by complete and uncomplete COMP activated or inhibited networks within human normal adjacent tissues or lung adenocarcinoma, but also by COMP activated and inhibited network between human normal adjacent tissues and lung adenocarcinoma. [ABSTRACT FROM AUTHOR]

Abstract: A 2.75-year-old Chinese boy presented with typical clinical features of pseudoachondroplasia, including disproportionate short-limb short stature, brachydactyly, genu varus and waddling gait. Radiologically, tubular bones were short with widened metaphyses, irregular and small epiphyses; anterior tonguing or beaking of vertebral bodies were characteristic. DNA sequencing analysis of the COMP gene revealed a heterozygous mutation (c.1511G>A, p.Cys504Tyr) in the patient but his parents were unaffected without this genetic change. The missense mutation (c.1511G>A) was not found in 100 healthy controls and has not been reported previously. Our findings expand the spectrum of known mutations in COMP leading to pseudoachondroplasia. [Copyright &y& Elsevier]

Current methods for diagnosing early stage osteoarthritis (OA) based on the magnetic resonance imaging and enzyme-linked immunosorbent assay methods are specific, but require specialized laboratory facilities and highly trained personal to obtain a definitive result. In this work, a user friendly and non-invasive quartz crystal microbalance (QCM) immunosensor method has been developed to detect Cartilage Oligomeric Matrix Protein (COMP) for early stage OA diagnosis. This QCM immunosensor was fabricated to immobilize COMP antibodies utilizing the self-assembled monolayer technique. The surface properties of the immunosensor were characterized by its FTIR and electrochemical impedance spectra (EIS). The feasibility study was based on urine samples obtained from 41 volunteers. Experiments were carried out in a flow system and the reproducibility of the electrodes was evaluated by the impedance measured by EIS. Its potential dynamically monitored the immunoreaction processes and could increase the efficiency and sensitivity of COMP detection in laboratory-cultured preparations and clinical samples. The frequency responses of the QCM immunosensor changed from 6 kHz when testing 50 ng/mL COMP concentration. The linear regression equation of frequency shift and COMP concentration was determined as: y = 0.0872 x + 1.2138 (R² = 0.9957). The COMP in urine was also determined by both QCM and EIS for comparison. A highly sensitive, user friendly and cost effective analytical method for the early stage OA diagnosis has thus been successfully developed. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To measure serum and synovial COMP levels in rheumatoid arthritis (RA) and osteoarthritis (OA) patients and to assess their correlation with clinical, laboratory and ultrasonographic parameters. Methods: Two groups of patients were included in this study consisting of 32 patients with RA and 10 patients with knee OA. Ultrasonography of knee joints was performed and serum and synovial Cartilage oligomeric matrix protein (COMP) levels were measured using an inhibition ELISA. Results: The mean synovial COMP level was significantly higher in RA compared to OA patients (14.3 ± 5.19μg/mL and 9.26 ±2.42 μg/mL respectively, P< 0.01). Amongst RA patients, it was higher in those with erosions. COMP levels were higher in synovial fluid compared to serum levels in both groups (P <0.01). Amongst RA patients, synovial COMP levels showed a significant positive correlation with synovial membrane thickness on ultrasonography (P <0.001), and significant negative correlation with the cartilage thickness (P <0.001). In OA group, synovial and serum COMP level showed significant positive correlation with WOMAC index for the lower limbs (r= 0.64, P < 0.05, and r=0.92, P <0.001 respectively) and a significant negative correlation with cartilage thickness (P <0.001). Conclusion: The synovial COMP and ultrasonographic joint evaluation may be considered as markers of disease activity and cartilage destruction in both RA and OA patients. [Copyright &y& Elsevier]

The article presents a study which investigates the clinical relevance of the cartilage oligomeric matrix protein (COMP) in dogs' Cerebrospinal fluid (CSF) with intervertebral disc herniation (IVDH). It states that the CSF from the lumbar spine (L-spine) and cisterna magna (C-CSF) from the 19 dogs with IVDH were examined through inhibition enzyme-linked immunosorbent assay (ELISA). It mentions that the L-CSF in dogs with IVDH has higher values of ELISA than for C-CSF- on dogs with IVDH.

Marathon running is frequently associated with numerous cellular changes, but little information is available on the effects of exercise-mediated prolonged impact-stress on cartilage integrity. This study was undertaken to evaluate muscle and cartilage damage with different running distances. Twenty male marathoners and ultra-marathoners participated in the study. Serum COMP and plasma CPK and hs-CRP were measured as markers of cartilage and muscle damage and inflammation. Serum COMP was increased 1.6-fold at 10 km during a marathon race and declined to the pre-race level after 2 days recovery. In contrast, serum COMP was increased 1.9-fold after a 200-km race and maintained until day 3 of recovery, only returning to the pre-race level on day 6. Plasma CPK was increased at 10 km of the marathon race and up to threefold at the end of the race. This was further increased on day 1, only returning to pre-race level on day 6. Plasma CPK was increased 35-fold at the end of the 200-km race and remained increased until day 5. There was no change in plasma hs-CRP during the marathon race, but this was increased 3.4-fold by day 1, returning to the pre-race level on day 4. Plasma hs-CRP increased 40-fold by the end of the 200-km race and was still increased on day 6 of recovery. Therefore, longer distance running may induce more impact-stress both on muscle and cartilage. Further, the required time for recovery may vary with running distance and the tissue type, e.g. cartilage or skeletal muscle as in this case. [ABSTRACT FROM AUTHOR]

In this study, we determined serum cartilage oligomeric matrix protein (COMP) levels in systemic juvenile idiopathic arthritis (sJIA) patients during both the active and the remission phases to investigate how the growth cartilage turnover changed under tocilizumab treatment. Specimens were collected from 201 healthy children under 16 years of age with no growth impairment, and paired sera were collected from 11 sJIA patients treated with tocilizumab. Disease activity was assessed from white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and ferritin, and the COMP concentration was determined by sandwich enzyme-linked immunosorbent assay. Serum COMP concentrations were found independent of age, and the mean value in healthy children was 17.74 ± 5.6 U/L. The mean serum COMP in sJIA patients during the active phase was 10.75 ± 3.9 U/L, lower than that of healthy children. The mean serum COMP in the remission phase (14.89 ± 3.9 U/L) was significantly higher than that in the active period ( P < 0.05). These results suggested that in sJIA patients, a reduced serum COMP concentration is a useful marker of active disease and growth impairment, and that the growth cartilage turnover suppressed during the active phase is improved in the remission phase under tocilizumab treatment. [ABSTRACT FROM AUTHOR]

Abstract: Chondrodysplasias are a genetically heterogeneous group of skeletal disorders. Mutations in genes coding for cartilage oligomeric matrix protein (COMP), collagen IX and matrilin-3 have been described to cause the autosomal dominantly inherited form of multiple epiphyseal dysplasia (MED). Even though there is clear evidence that these cartilage matrix proteins interact with each other, their exact functions in matrix organisation and bone development still need to be elucidated. We generated a mouse model lacking both collagen IX and COMP to study the potential complementary role of these proteins in skeletal development. Mice deficient in both proteins exhibit shortened and widened long bones as well as an altered bone structure. They display severe growth plate abnormalities with large hypocellular areas in the central parts of the tibia. In addition, chondrocytes in the proliferative and hypertrophic zones do not show their typical columnar arrangement. These phenotypical traits were not observed in mice deficient only in COMP, while mice lacking only collagen IX showed similar growth plate disturbances and shorter and wider tibiae. The contribution of COMP to the phenotype of mice deficient in both collagen IX and COMP appears minor, even though clear differences in the deposition of matrilin-3 were detected. [Copyright &y& Elsevier]

Abstract: In humans, mutations in cartilage oligomeric matrix protein (COMP) cause autosomal dominantly inherited skeletal dysplasias. We have generated transgenic mouse lines to study the role of mutant D469Δ COMP in the pathogenesis of pseudoachondroplasia. Biochemical characterization of cartilage tissue demonstrated that transgenic and endogenous COMP subunits were able to form mixed, pentameric molecules in vivo. Mutant COMP was more difficult to extract than the wildtype protein, suggesting an altered anchorage within the matrix. Although both transgenic wildtype and mutant COMP were detected throughout the growth plate, mutant molecules were restricted to the pericellular matrix while wildtype COMP showed a uniform distribution throughout the extracellular matrix. Mice expressing the mutant transgene showed a slight gender specific growth retardation. In mutant animals, the columnar organization in the growth plate was disturbed, proteoglycans were lost and improperly formed collagen fibrils were observed. In some chondrocytes the endoplasmic reticulum was dilated, most probably due to an impaired secretion of mutant COMP similar to that observed in patients. Later in development, the growth plate was irregularly shaped and prematurely invaded by bony tissue. In addition, a fusion of the third and fourth sternebrae was frequently observed. [Copyright &y& Elsevier]

Advanced glycation end-product (AGE) pentosidine has previously been demonstrated in different tissues and body fluids. It was suggested as a novel marker for evaluating the pathologic activity in rheumatoid arthritis (RA). In this study we analyzed the relation between pentosidine and markers of inflammation, cartilage turnover, immune response, and disease status of RA. Using HPLC, we analyzed pentosidine in serum and synovial fluid from 39 patients with RA and in serum from 38 healthy controls. Cartilage oligomeric matrix protein (COMP) and antibodies to CCP (anti-CCP) were measured by ELISA. Clinical disease status was assessed by Disease Activity Score 28 (DAS 28) and functional status by Health Assessment Questionnaire (HAQ). We demonstrated significantly higher serum levels of pentosidine in RA patients in comparison with controls. Pentosidine in serum significantly correlated with pentosidine in synovial fluid. Serum pentosidine levels were associated with erythrocyte sedimentation rate (p<0.03) but not with CRP, COMP, anti-CCP antibodies, DAS 28, or HAQ. In contrast to previous studies, we could not show any correlation of pentosidine levels with inflammatory status, clinical disease activity, markers of immune response, or cartilage breakdown. However, AGEs can be suggested as important players participating in joint destruction rather than markers of disease activity. [ABSTRACT FROM AUTHOR]

Biochemical factors play an important role in osteoarthritis (OA) pathogenesis. The purpose of this study is to clarify whether the dermatan sulfate (DS) levels in the synovial fluid of patients with knee OA are related to residual cartilage. Synovial fluid was obtained from 51 OA patients. Knee radiographs were evaluated with the Kellgren–Lawrence (K/L) grading scale. The levels of the following disaccharides were measured by high-performance liquid chromatography (HPLC): DS (DSΔDi4S), chondroitin 6-sulfate (CSΔDi6S), and chondroitin 4-sulfate (CSΔDi4S). The concentration of cartilage oligomeric matrix protein (COMP) was measured by a sandwich ELISA. The levels of DSΔDi4S in Grades 0 and I OA were significantly higher than levels in Grade II ( P = 0.0458), Grade III ( P < 0.0001) and Grade IV ( P < 0.0001), and we found strong relationships between the levels of DSΔDi4S and those of CSΔDi6S ( P < 0.0001, r = 0.705), CSΔDi4S ( P < 0.0001, r = 0.750), and COMP ( P < 0.0001, r = 0.699). We conclude that the presence of DSΔDi4S reflects proteoglycan metabolism in the residual articular cartilage of OA patients. This suggests that metabolism of the small leucine-rich repeat proteoglycans decorin and biglycan, which contain chains of DSΔDi4S, is similar to that of aggrecan. [ABSTRACT FROM AUTHOR]

Cartilage oligomeric matrix protein (COMP) strengthens cartilage by binding to type II and type IX collagen-forming bridges between collagen fibrils. It was hypothesized that perhaps one or more anabolic growth factors such as insulin-like growth factor-I (IGF-I), fibroblast growth factor-1 (FGF-1) or platelet derived growth factor-BB (PDGF-BB) increase COMP gene expression. Their effects on primary human chondrocytes and the chondrogenic cell line ATDC5 were studied using real time reverse transcript-polymerase chain reaction (RT-PCR) for quantification. IGF-I, but not the FGF-1 or PDGF-BB, up-regulated COMP gene expression by approximate 5-fold in human adult chondrocytes in a dose- and time-dependent manner. IGF-I exerted similar effects on ATDC5 cells. Results from these real time RT-PCR experiments were confirmed by transfecting into ATDC5 cells a full-length mouse COMP promoter cloned upstream of a luciferase reporter gene. On stimulation with IGF-I, the luciferase reporter activity increased by about eight times. In conclusion, IGF-I seems to be an important positive regulator of COMP, which may play an important role in an attempted repair of either traumatized or degenerated cartilage. Edited by Ming-Hua XU [ABSTRACT FROM AUTHOR]

This study examined the serum and synovial fluid concentrations of cartilage oligomeric matrix protein (COMP) in relation to the evolution of joint cartilage damage and the requirement for surgery in 125 patients with rheumatoid arthritis (RA). We compared the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and matrix metalloproteinase-3 (MMP-3) levels with COMP levels determined by specific enzyme-linked immunosorbent assay (ELISA). Patients were divided into three groups: (1) patients with least erosive disease (LES); (2) patients with more erosive disease (MES); and (3) patients with mutilating disease (MUD). In addition, synovial fluid samples were collected from patients undergoing arthroscopic synovectomy of the knee joint (ASS) and total knee arthroplasty (TKA). Serum COMP levels correlated with the ESR (P<0.0001,r= 0.374,n= 125) and the CRP level (P= 0.0014,r= 0.281,n= 125). COMP levels did not correlate with the MMP-3 level (P= 0.182,r= 0.114,n= 125). The COMP levels of the LES group were significantly lower than those of the MES or MUD groups. Lastly, synovial fluid COMP levels in the TKA group were higher than in the ASS group. Therefore, these findings suggest that serum and synovial fluid COMP levels in patients with RA may reflect cartilage destruction and are correlated with the ESR and the CRP level, which are indicators of the acute-phase response. [ABSTRACT FROM AUTHOR]

Abstract: Pseudoachondroplasia (PSACH) is an autosomal dominant disease that mainly affects cartilage, resulting in skeletal dysplasias and early onset osteoarthritis. PSACH is caused by mutations in the cartilage oligomeric matrix protein (COMP) gene. PSACH chondrocytes accumulate unique COMP-containing lamellar structures in an expanded rough endoplasmic reticulum (rER). Although COMP is also present in tendon extracellular matrix (ECM), it does not accumulate in PSACH tendon cells, suggesting the disease involves a chondrocyte-specific trafficking problem. To investigate putative cell-specific trafficking differences, we generated a cell culture model utilizing expression of the common ΔD469 COMP mutation. In rat chondrosarcoma (RCS) cells, we find delayed secretion and ER accumulation of ΔD469 COMP, paralleling the altered trafficking defect in PSACH chondrocytes. Non-chondrocytic COS-1 cells, in contrast, efficiently trafficked and secreted both mutant and wild-type COMP. In chondrocytic cells, expression of ΔD469 COMP led to ER accumulation of type IX collagen, but did not affect aggrecan trafficking. Endogenous rat COMP accumulated in the ER along with expressed ΔD469 COMP in a stably expressing RCS clone, consistent with the dominant negative effect of PSACH. When these stably expressing cells were cultured to promote ECM deposition, the small amount of secreted mutant COMP disrupted assembly of the normal fibrillar meshwork and caused irregular aggregates of COMP and type IX collagen to form. Thus, in a new model that reflects the cellular pathology of PSACH, we establish trafficking differences for mutant COMP in chondrocytic and non-chondrocytic cells and demonstrate that mutant COMP interferes with assembly of a normal ECM. [Copyright &y& Elsevier]

Markers of cartilage degradation hold a great, but so far underutilized potential in the research and clinical management of joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA). With the rapid pace of development of such markers, they are likely to emerge as promising clinical tools for several uses. These roles may include: improving preclinical and clinical development in arthritis research; differentiation of patients with high and low turnover states at disease diagnosis; selection of optimal therapy and therapy dose for the individual patient; monitoring disease progression; and predicting disease outcome.This review focuses on the cartilage matrix components and the metabolites from this very special tissue that have been proposed as biochemical markers. Special attention is focused on the challenges facing the development of such markers to the standards required for widespread practical use. Examples are provided on the current use of cartilage derived biochemical markers and perspectives for the future use of markers and required clinical documentation are presented. [Copyright &y& Elsevier]

Background: Cartilage oligomeric matrix protein/thrombospondin 5 (COMP/TSP 5) is one of the most promising serologic markers with regard to an ability to prognose development of osteoarthritis (OA). Our aim was to map the epitopes of three monoclonal antibodies (mAb) to COMP and to develop and characterize a sandwich enzyme-linked immunosorbent assay (ELISA) for measuring COMP levels in human body fluids. Methods: COMP was digested with trypsin and the NH2-terminal sequence of the fragments recognized by each of the mAbs was determined. Steric competition among the mAbs was tested with an antibody capture assay. A sandwich ELISA was developed using unlabeled mAb 16-F12 as a capture antibody, and mAb 17-C10 labeled with biotin as the second antibody. Results: Epitopes of the three mAbs were mapped to three different domains within the COMP subunit (16-F12, NH2-terminal domain; 17-C10, EGF-like domain; 12-C4, COOH-terminal domain). These epitopes did not overlap. mAbs 17-C10 and 12-C4 yielded similar serum COMP results when used as the secondary antibodies. Serum COMP levels measured with the new sandwich ELISA using mAbs 16-F12 and 17-C10 correlated strongly with results based on an inhibition ELISA with mAb 17-C10 alone (r2=0.836; P<0.0001). We characterized the new sandwich ELISA with regards to inter- and intra-assay variability, the range of COMP levels that can be expected in human synovial fluids (SF) and sera (controls and OA and rheumatoid arthritis (RA) patients), and the day-to-day and diurnal variability of COMP levels in sera. Conclusions: We have developed and characterized a sandwich ELISA for COMP that is sensitive and yields highly reproducible COMP results upon analysis of human sera and synovial fluids. [Copyright &y& Elsevier]

Strain-induced tendinopathy is a common injury in both human and equine athletes, with increasing incidence associated with greater involvement in sport and an increasingly aged population. This paper reviews our studies on the abundant non-collagenous protein, cartilage oligomeric matrix protein (COMP), in equine tendons. Its variation between tendon type and site, age and exercise has provided an insight into how age and exercise influence tendon growth and maturation. Tendons can be broadly divided into two types, reflecting their different matrix composition and function: the energy-storing tendons used for weight-bearing and locomotion, which suffer a high incidence of strain-induced tendinopathy, and positional tendons involved in limb placement or manipulative skills. It would appear that while energy-storing tendon can respond to the mechanical forces applied to it during growth, there is no evidence that it can do so after skeletal maturity. Instead, cumulative fatigue damage causes degeneration at the molecular level, potentially weakening it and increasing the risk of clinical injury. Appropriate exercise regimes early in life may help to improve the quality of growing tendon, thereby reducing the incidence of injury during ageing or subsequent athletic career. [Copyright &y& Elsevier]

Recent work indicates that cartilage oligomeric matrix protein (COMP) plays an important role in extracellular matrix assembly and matrix–matrix protein interactions. In order to identify the proteins in extracellular matrix that interact with COMP, we used an ELISA-based solid-phase binding assay, which revealed a specific, high-affinity interaction between COMP and fibronectin. This interaction is concentration-dependent and saturable, and appears to occur under physiologically relevant conditions. Electron microscopy after negative staining and fragment binding analysis using the solid-phase assay revealed a predominant binding site for the COMP C-terminal globular domain to a molecular domain approximately 14 nm from the N-terminal domain of fibronectin, which can be inhibited by the presence of a polyclonal antibody specific for the C-terminal heptadecapeptide of COMP. This interaction is further demonstrated in vivo by colocalization of both COMP and fibronectin in the chondrocyte pericellular matrix by laser confocal microscopy of chondrocytes grown in agarose culture, and by appositional and colocalization of these proteins in the growth plate of primates by immunohistochemistry. [Copyright &y& Elsevier]