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Osteoarthritis (OA) is a disease affecting articular cartilage, bone and soft tissues. It is the most common form of joint diseases and cause of musculoskeletal disability in the elderly. Despite its high frequency, OA has few efficient therapeutics, probably as a consequence of its late diagnosis. Physical examination and radiographic studies are relatively poor means for detecting disease early or predicting progression. Usually, OA progression is monitored by measurement of changes in joint space width on plain X-ray with a graduated magnifying lens or with a computer after digitisation of the radiograph. This must be considered a rather indirect measure of cartilage integrity, as articular cartilage itself is invisible on the radiographs and thus has to be assessed indirectly from the spacing between the subchondral bone ends of the joint. Furthermore, joint space width does not allow detection of early structural damage and remains difficult to use in daily practice. Magnetic resonance imaging (MRI) is a promising non-invasive tool for evaluation of cartilage, but access to this technique is confined and very expansive. Further, MRI, such as other standard X-ray, gives a static picture of the cartilage lesion, but fails to explore the metabolic changes occurring in OA cartilage. Alternatively, biochemical factors of bone, synovium or cartilage turnover have been proposed as potential tools for diagnostic, prognostic and monitoring treatment efficacy. Nevertheless, because cartilage degradation is a key feature of OA pathogenesis, a particular attention has been paid for molecules originating from cartilage. Cartilage is composed of two major proteins, aggrecan and type II collagen [1]  [2]. Among these proteins, type II collagen is possibly the ideal marker of cartilage degradation.

Recently, Bone and Cartilage Research Unit has then developed specific immunoassays (ELISA) for measuring in biological fluids Coll2-1 (108 HRGYPGLDG 116), a denaturation neo-epitope located in the NH2-terminal end of the triple helical domain of the type II collagen, in its native or nitrated form (Coll2-1NO2: 108 HRGY(NO2)PGLDG 116).


We used a new approach for quantifying type II collagen network degradation. This approach is based on the detection in urine, serum and synovial fluid of a peptide released from the triple helix of type II collagen in its native or nitrated form. Peptide nitration results from the reaction of aromatic amino acids with peroxynitrite (ONOO-), a strong oxidant formed by the reaction of nitric oxide (●NO) and superoxide anion (O2-). In OA, ●NO and O2- are produced by a large number of cells including macrophages and chondrocytes. Tyrosine, tryptophan and phenylalanine are particularly sensitive to nitration. Type II collagen contains two tyrosines, one located in the triple helix and the other in the telopeptide at the C-terminal end.

According the criteria of BIPED*classification, Coll2-1 and Coll2-1NO2 are a useful biomarker for the classification of individuals as diseased or no diseased, the assessment of severity or extent of osteoarthritis and the prediction of future onset or progression of osteoarthritis [2]. This classification is based on the data of clinical studies recently reported in the literature:

- Serum Coll2-1 and Coll2-1NO2 concentrations were not influenced by age and did not undergo diurnal variation.

- Serum Coll2-1 and Coll2-1NO2 concentrations were significantly higher in patients with osteoarthritis or with rheumatoid arthritis than in control individuals of the same age range [3].

- Serum Coll2-1NO2 concentration was higher in patients with rheumatoid arthritis than in those with osteoarthritis, and the ratio Coll2-1NO2:Coll2-1 discriminates between osteoarthritis and rheumatoid arthritis.

- Serum Coll2-1 concentration was normalized after joint replacement in patients with isolated unilateral knee or hip osteoarthritis, indicating that Coll2-1 is useful for monitoring the pathological changes that occur in a single joint [4].

- The one-year increase in urinary Coll2-1 and Coll2-1NO2 were negatively correlated with the 3-year change in joint space width, indicating that increase in levels of Coll2-1 in urine reflected radiological osteoarthritis progression [5].

Coll2-1 and Coll2-1NO2 provides useful information for clinical and research applications. Our markers can also be used to monitored horse, dog, mice and guinea pig osteoarthritis [6] [7]

*The BIPED (B = burden of disease; I = investigative; P = prognostic; E = efficacy of intervention; D = diagnostic) classification was proposed by the Osteoarthritis Biomarkers Network (a consortium of five US National Institutes of Health designated sites) [8].

Differential proteomic analyze provide a powerfull tool to identify new biomarkers of osteoarthritis. This approach is not restricted to consider proteins derived from the degradation of cartilage. It allows the identification of specific proteins whose concentration is modified significantly in different biological from patients with OA. The pattern of expression of these proteins in a particular biological compartment can therefore serve as a biological marker of the disease.

The technique of 2D-DIGE (two dimensionnal-differential in gel electrophoresis) allows us to compare the composition of normal and pathological samples in a quantitative manner: a protein present in a sample are labelled by a fluorochrome with specific wavelength of excitation and emission (Cydye 2, 3 or 5). An internal standard, consisting of a mixture equivalent samples to compare itself is labelled by a third fluorochrome. The samples are mixed together and migrate on the same gel during electrophoresis. The relative abundance of peptides is compared on the basis of their fluorescence intensity. The proteins of interest are then identified by tandem mass spectrometry.




With this technology, we hope to find new biomarkers of osteoarthritis. Then, we will develop immunoassays to measure the concentration of these markers in the blood or urine.


[1] Henrotin Y, Deberg M, Dubuc JE, Quettier E, Christgau S, Reginster JY. Type II collagen peptides for measuring cartilage degradation. Biorheology 2004;41: 543-7. [Pubmed]
[2] Henrotin Y, Addison S, Kraus V, Deberg M. Type II collagen markers in osteoarthritis: what do they indicate? Curr Opin Rheumatol 2007;19: 444-50. [Pubmed]
[3] Deberg M, Labasse A, Christgau S, Cloos P, Bang Henriksen D, Chapelle JP, Zegels B, Reginster JY, Henrotin Y. New serum biochemical markers (Coll 2-1 and Coll 2-1 NO2) for studying oxidative-related type II collagen network degradation in patients with osteoarthritis and rheumatoid arthritis. Osteoarthritis Cartilage 2005;13: 258-65. [Pubmed]
[4] 4. Deberg M, Dubuc JE, Labasse A, Sanchez C, Quettier E, Bosseloir A, Crielaard JM, Henrotin Y. One year follow-up of Coll2-1, Coll2-1NO2 and myeloperoxydase serum levels in OA patients after hip or knee replacement. Ann Rheum Dis 2007 (In press).
[5] Deberg MA, Labasse AH, Collette J, Seidel L, Reginster JY, Henrotin YE. One-year increase of Coll 2-1, a new marker of type II collagen degradation, in urine is highly predictive of radiological OA progression. Osteoarthritis Cartilage 2005;13: 1059-65. [Pubmed]
[6] Gangl M, Serteyn D, Lejeune JP, Schneider N, Grulke S, Peters F, Vila T, Deby-Dupont G, Deberg M, Henrotin Y. A type II-collagen derived peptide and its nitrated form as new markers of inflammation and cartilage degradation in equine osteochondral lesions. Res Vet Sci 2007;82: 68-75. [Pubmed]
[7] Ameye LG, Deberg M, Oliveira M, Labasse A, Aeschlimann JM, Henrotin Y. The chemical biomarkers C2C, Coll2-1, and Coll2-1NO2 provide complementary information on type II collagen catabolism in healthy and osteoarthritic mice. Arthritis Rheum 2007;56: 3336-46. [Pubmed]
[8] 6. Bauer DC, Hunter DJ, Abramson SB, Attur M, Corr M, Felson D, Heinegard D, Jordan JM, Kepler TB, Lane NE, Saxne T, Tyree B, Kraus VB. Classification of osteoarthritis biomarkers: a proposed approach. Osteoarthritis cart 2006; 14: 723-27.