WP 5. Cartilage and bone markers for prediction of outcome and response to therapy – including use of radiography as the current standard

This area of work will be lead by Partner 11(Lund) with input from Partner 3 (Berlin), Partner 6 (AMC Amsterdam) Partner 8 (Nijmegen) and Partner 19 (Warsaw) and partner 21 (EULAR)

The objective is to develop and evaluate molecular markers for cartilage and bone that can be used to monitor tissue processes in experimental in vitro systems, in experimental arthritis and in human arthritis for elucidating the structural events during development and progression of rheumatoid arthritis and also to use the technology as a tool to explore the tissue protective potential of novel treatment modalities.

Workplan

During the first period of the project we plan to develop immunoassays suitable for these purposes for CILP (cartilage intermediate layer protein), a cartilage specific protein recently described by Pilar Lorenzo, currently a postdoc in our laboratory (Lorenzo et al. J Biol Chem 1998;273:23463-23466). Due to the known characteristics of the protein it is anticipated that more than one assay using different antibodies will be used for different purposes. A prototype assay using a polyclonal antibody has shown the utility of CILP for serum and synovial fluid analyses in samples from RA and osteoarthritis patients. To ensure availability of reagents recombinant CILP will be produced.

Furthermore we will evaluate proof of concept for refinement of the assay for selected fragments of COMP (cartilage oligomeric matrix protein), where the currently available assays do not discriminate between intact and fragmented protein (Saxne & Heinegård. Br J Rheumatol 1992; 31:583-591).

Concomitantly characterisation of another matrix protein, CHAD (chondroadherin), will continue and development of immunoassay is planned (Månsson et al.. J Biol Chem 2001; 276:32883-32888). This protein, which has cell-regulating properties, seems to be released in very early phases of arthritis and may thus be a very early indicator of disturbed cartilage metabolism.

A further line of the project focuses on fibromodulin, a protein involved in the stabilisation of the collagen network. We have identified neoepitopes generated during enzymatic cleavage of the protein, importantly such being released in pathological conditions but not during normal turnover (Heathfield et al, J Biol Chem. 2004; 20:6286-95). Assays for these neoepitopes will be developed.

Data from the use of all these biomarkers will be compared with data using established radiographic methodologies (see section 4, B4). We have access to several well characterised cohorts of patients where radiographic information as well as serum specimens are available (see WP 2-4) and these materials will be used in order to define the predictive values of the various biomarkers in relation to the X-ray findings. These studies will also permit us to define the relationship between destruction and inflammation in the individual patient, something that will be important in choosing the optimal therapy for this individual patient with RA.

These studies should also allow us to define whether and which patients are experiencing repair, and to determine which biomarkers that correlate with the activation of a repair process in the joints