IntroductionAcute trauma involving the anterior cruciate ligament is believed to be a major risk factor for the development of post-traumatic osteoarthritis 10 to 20 years post-injury. In this study, to better understand the early biological changes which occur after acute injury, we investigated synovial fluid and serum biomarkers.MethodsWe collected serum from 11 patients without pre-existing osteoarthritis from a pilot intervention trial (5 placebo and 6 drug treated) using an intra-articular interleukin-1 receptor antagonist (IL-1Ra) therapy, 9 of which also supplied matched synovial fluid samples at presentation to the clinic after acute knee injury (mean 15.2 ± 7.2 days) and at the follow-up visit for reconstructive surgery (mean 47.6 ± 12.4 days). To exclude patients with pre-existing osteoarthritis (OA), the study was limited to individuals younger than 40 years of age (mean 23 ± 3.5) with no prior history of joint symptoms or trauma. We profiled a total of 21 biomarkers; 20 biomarkers in synovial fluid and 13 in serum with 12 biomarkers measured in both fluids. Biomarkers analyzed in this study were found to be independent of treatment (P > 0.05) as measured by Mann-Whitney and two-way ANOVA.ResultsWe observed significant decreases in synovial fluid (sf) biomarker concentrations from baseline to follow-up for sfC-Reactive protein (CRP) (P = 0.039), sflubricin (P = 0.008) and the proteoglycan biomarkers: sfGlycosaminoglycan (GAG) (P = 0.019), and sfAlanine-Arginine-Glycine-Serine (ARGS) aggrecan (P = 0.004). In contrast, we observed significant increases in the collagen biomarkers: sfC-terminal crosslinked telopeptide type II collagen (CTxII) (P = 0.012), sfC1,2C (P = 0.039), sfC-terminal crosslinked telopeptide type I collagen (CTxI) (P = 0.004), and sfN-terminal telopeptides of type I collagen (NTx) (P = 0.008). The concentrations of seven biomarkers were significantly higher in synovial fluid than serum suggesting release from the signal knee: IL-1β (P < 0.0001), fetal aggrecan FA846 (P = 0.0001), CTxI (P = 0.0002), NTx (P = 0.012), osteocalcin (P = 0.012), Cartilage oligomeric matrix protein (COMP) (P = 0.0001) and matrix metalloproteinase (MMP)-3 (P = 0.0001). For these seven biomarkers we found significant correlations between the serum and synovial fluid concentrations for only CTxI (P = 0.0002), NTx (P < 0.0001), osteocalcin (P = 0.0002) and MMP-3 (P = 0.038).ConclusionsThese data strongly suggest that the biology after acute injury reflects that seen in cartilage explant models stimulated with pro-inflammatory cytokines, which are characterized by an initial wave of proteoglycan loss followed by subsequent collagen loss. As the rise of collagen biomarkers in synovial fluid occurs within the first month after injury, and as collagen loss is thought to be irreversible, very early treatment with agents to either reduce inflammation and/or reduce collagen loss may have the potential to reduce the onset of future post-traumatic osteoarthritis.Trial registrationThe samples used in this study were deriv...

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The protein kinase C (PKC) signaling pathway is a major regulator of cellular functions and is implicated in pathologies involving extracellular matrix remodeling. Inflammatory joint disease is characterized by excessive extracellular matrix catabolism, and here we assess the role of PKC in the induction of the collagenases, matrix metalloproteinase (MMP)-1 and MMP-13, in human chondrocytes by the potent cytokine stimulus interleukin-1 (IL-1) in combination with oncostatin M (OSM). IL-1 ؉ OSM-stimulated collagenolysis and gelatinase activity were ameliorated by pharmacological PKC inhibition in bovine cartilage, as was collagenase gene induction in human chondrocytes. Small interfering RNA-mediated silencing of PKC gene expression showed that both novel (nPKC␦, nPKC) and atypical (aPKC, aPKC) isoforms were involved in collagenase induction by IL-1. However, MMP1 and MMP13 induction by IL-1 ؉ OSM was inhibited only by aPKC silencing, suggesting that only atypical isoforms play a significant role in complex inflammatory milieus. Silencing of either aPKC led to diminished IL-1 ؉ OSM-dependent extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription (STAT) 3 phosphorylation, and c-fos expression. STAT3 gene silencing or ERK pathway inhibition also resulted in loss of IL-1 ؉ OSM-stimulated c-fos and collagenase expression. Silencing of c-fos and c-jun expression was sufficient to abrogate IL-1 ؉ OSM-stimulated collagenase gene induction, and overexpression of both c-fos and c-jun was sufficient to drive transcription from the MMP1 promoter in the absence of a stimulus. Our data identify atypical PKC isozymes as STAT and ERK activators that mediate c-fos and collagenase expression during IL-1 ؉ OSM synergy in human chondrocytes. aPKCs may constitute potential therapeutic targets for inflammatory joint diseases involving increased collagenase expression.Inflammation is a major characteristic of joint diseases such as rheumatoid arthritis and osteoarthritis (OA), 3 during which inflammatory mediators released by infiltrating immune cells as well as resident joint cells induce alterations in gene expression that can lead to ECM degradation (1, 2). Cytokines such as interleukin (IL-)1, IL-17, and tumor necrosis factor ␣ (TNF␣) are key mediators thought to be involved in promoting inflammatory responses in such destructive joint diseases (3, 4). We have shown that the IL-6 family cytokines oncostatin M (OSM) and IL-6 markedly exacerbate the catabolic potential of these mediators, synergistically promoting cartilage ECM catabolism both in vitro and in vivo (5-9).Chondrocytes are the only resident cell type in normal articular cartilage and function to preserve homeostasis. This is achieved by balancing the expression of ECM components with catabolic factors such as the matrix metalloproteinases (MMPs), which collectively can degrade all the ECM macromolecules. During inflammatory joint diseases, chondrocytes are stimulated to secrete elevated levels of MMPs that, once activated, media...

The adhesion to mesothelial monolayers of eight cultured ovarian tumour cell lines was studied in multiwell plates as a model for some of the interactions of ovarian cancer in the peritoneal cavity. When only the upper half of the conditioned medium (CM) from a confluent mesothelial cell culture was aspirated, the adhesion of the tumour cells was low (3.5%-36%). When the medium was removed completely the adhesion increased. The tumour cell lines showing the greatest enhancement of adhesion were those which had previously been shown to express the highest amounts of CD44. By adding erythrocyte suspensions to mesothelial cells it was shown that there was a pericellular coat around the mesothelial cells that could be destroyed by aspirating the medium, or by treating the medium with hyaluronidase (Hase). Treatment of the CM with Hase also considerably increased tumour cell adhesion. Furthermore, CM was shown to contain high amounts of hyaluronic acid (HA). HA blocked adhesion in the absence of CM, but the effect was not as large as that produced by the pericellular coat. It is proposed that pericellular HA produced by mesothelial cells has an important role in the invasion of ovarian tumour cells in the peritoneal cavity.