The release of crosslinked peptides from type II collagen into human synovial fluid is increased soon after joint injury and in osteoarthritis

Abstract

Objective. To determine concentrations of crosslinked C-telopeptide fragments of type II collagen (CTX-II) in synovial fluid (SF) from patients with joint injury, osteoarthritis (OA), or other knee arthritides.Methods. Two study groups were used: a crosssectional group, which included healthy-knee volunteers (reference group [REF]) and patients with pseudogout (PPA), an anterior cruciate ligament tear with or without a meniscus tear (INJ), or primary knee OA (POA); and a longitudinal group, which included patients with arthroscopic cartilage changes or septic arthritis. CTX-II was quantified by competition enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody that recognized the C-terminus of the peptide EKGPDP as a proteolytic neoepitope. Aggrecan fragments, matrix metalloproteinases 1 and 3, and tissue inhibitor of metalloproteinases 1 were determined by ELISAs.Results. Concentrations of CTX-II in SF were higher in patients with PPA, INJ, and POA than in the REF group (P < 0.001). After joint injury, mean levels of CTX-II in SF were increased above REF levels at all time intervals (P < 0.001), and were highest within hours after trauma. In those in the longitudinal study group with joint cartilage damage, variation coefficients for CTX-II were 81% (between patients) and 64% (within patient), monitored over 1 year. In a patient with septic arthritis, SF CTX-II increased at the onset of symptoms, and peaked 30-fold higher than the baseline. Concentrations of all biomarkers decreased with successful treatment.Conclusion. This is the first report to describe the release into SF of soluble molecular fragments specific for the degradation of mature, crosslinked, type II collagen (CII) in human OA and joint injury. The results provide strong evidence that the integrity of the CII network of cartilage is compromised soon after joint injury and in arthritis. This early degradation of CII may represent an important treatment target.Osteoarthritis (OA) and joint injury are characterized by remodeling and degradation of cartilage, bone, and other joint tissues. The normally very slow turnover rate of cartilage matrix (1) is increased, as observed by several techniques in both animal OA models and human OA. Phasic changes in both synthesis and degradation of collagen and other matrix molecules (2-6) are associated with altered tissue structure and material properties (7-9).Increased joint tissue turnover after injury and in OA can be detected by a release of molecules and molecular fragments into synovial fluid (SF), blood, and urine. For example, the stimulated synthesis of type II collagen (CII) results in higher levels of CII C-propeptide in SF (10,11). Stimulated aggrecan synthesis results in more aggrecan fragments carrying the 846 epitope (12). Higher synovial concentrations of matrix metalloproteinases (MMPs), such as MMP-1 and MMP-3, and proteinase activity after joint injury and in OA are consistent with the observed expression of these

Decreased lubricin concentrations and markers of joint inflammation in the synovial fluid of patients with anterior cruciate ligament injury

“…Log 2 TNF␣ levels showed a statistically significant negative relationship with log 2 lubricin concentrations when levels were detectable (slope ϭ Ϫ0.23, SE ϭ 0.08, t [16] ϭ Ϫ3.00, P ϭ 0.0085) (Figure 4). There was no statistically significant relationship between levels of log 2 IL-1␤ (slope ϭ Ϫ0.12, SE ϭ 0.19, t [13] ϭ Ϫ0.62, P ϭ 0.5474), log 2 IL-6 (slope ϭ Ϫ0.08, SE ϭ 0.06, t [27] ϭ Ϫ1.52, P ϭ 0.1402), procathepsin B (slope ϭ Ϫ0.09, SE ϭ 0.29, t [28] ϭ Ϫ0.30, P ϭ 0.7629), or neutrophil elastase (slope ϭ Ϫ0.1717, SE ϭ 0.1931, t [17] ϭ Ϫ0.89, P ϭ 0.3865) and log 2 lubricin concentration.…”

“…When the lubricin levels were normalized to those in the contralateral knee, there was a significant increase in the lubricin concentration with time postinjury ( Figure 1B). The contralateral-normalized lubricin concentration in the injured limb was low shortly after injury but increased as a function of days since injury (slope ϭ 0.002, SE ϭ 0.0003, F [1,28] ϭ 65.89, P Ͻ 0.0001) ( Figure 1B).…”

“…Likewise, the proteoglycan turnover epitope 846 has also been shown to be elevated following ACL injury, and this was correlated with collagen turnover markers, including cartilage oligomeric matrix protein and C-propeptide of type II collagen (PIICP) (30). In addition, PIICP and the release of crosslinked type II collagen into SF have been shown to increase following ACL injury (28,31). These studies support the finding that cartilage metabolism is altered following injury and may be an indicator of OA in this patient population.…”

“…Various markers of cartilage matrix turnover have been previously evaluated following ACL injury (27)(28)(29)(30)(31). Lohmander et al reported a marked increase in SF proteoglycan fragments within 3-4 weeks of ACL injury that remained high in many patients up to 4 years after injury (29).…”

Mechanical injury of cartilage explants causes specific time‐dependent changes in chondrocyte gene expression

“…Previous clinical studies have shown an increase in the protein levels of matrix metalloproteinase 3 (MMP-3) and tissue inhibitor of metalloproteinases 1 (TIMP-1) as well as an increase in proteoglycan and type II collagen fragments in the synovial fluid of patients following a tear in the anterior cruciate ligament (ACL) or meniscus from 1 day to 20 years after the injury (5,6). During the first week after ACL injury, a significant increase in synovial fluid levels of tumor necrosis factor ␣ (TNF␣) and interleukin-1␤ (IL-1␤) can also occur.…”