Cartilage Assay Overview
Publication: Overview of the IBEX Assays by Dr. Robin Poole
Measuring Collagen Synthesis and Degradation
During growth, there is active assembly of the extracellular matrix. This synthesis is then markedly reduced in the adult to very low levels. In healthy cartilage, there is some synthesis and degradation of type II collagen as well as the proteoglycan aggrecan. The degraded matrix molecule fragments are then released into the synovial fluid, blood and urine.
Cartilage metabolism is altered in OA and RA resulting in an imbalance between collagen synthesis and degradation. As a consequence, there is a loss of cartilage leading to joint degradation. In arthritis, type II collagen loss is the result of extensive cleavage by the activity of enzymes (collagenases including MMP-1, MMP-8 and MMP-13).
IBEX assays allow for the study of both the synthesis and degradation of connective tissue components and are powerful tools when used together since they can provide a direct means of investigating joint damage.
Collagen Degradation Assays
- C2C – The C2C assay measures type II collagen destruction. This assay is optimized for serum; for human urine, please see IB-C2C-HUSA™. This ELISA with specific monoclonal antibody to type II collagen primary cleavage site recognizes the α-chain fragments containing an approximate 9 amino acid sequence from the carboxy terminus of the three-quarter length piece produced by collagenase cleavage (MMP-1, MMP-8, MMP-13) of type II collagen.
- C1,2C – The C1,2C assay, also known as COL2 ¾ C short, measures type I and type II collagen destruction. This ELISA with specific polyclonal antibody to type I and type II collagen primary cleavage site recognizes the α-chain fragments containing an approximate 8 amino acid sequence from the carboxy terminus of the three-quarter length piece produced by collagenase cleavage (MMP-1, MMP-8, MMP-13) of type II collagen.
Collagen and Aggregan Synthesis Assays
- CPII – The CPII assay, also known as Procollagen II C-Propeptide, measures type II collagen synthesis. This ELISA assay with polyclonal antibody to type II collagen measures intact C-propeptide and many of its degradation products. It has been reported that in rheumatoid arthritis, there is an increased level of CPII in serum. Conversely, in osteoarthritis, there is a decreased level in serum and an increased level in synovial fluid.
- CS846 – The CS846, also known as aggrecan chondroitin sulfate 846 epitope, measures newly formed aggrecan. This ELISA assay with specific IgM monoclonal antibody recognizes an epitope present in fetal aggrecan and large aggrecan produced to repair cartilage damage when tissue is affected by RA or OA.