Oxidative changes and signalling pathways are pivotal in initiating age-related changes in articular cartilage.

Objective: To use a computational approach to investigate the cellular and extracellular matrix changes that occur with age in the knee joints of mice.

Methods: Knee joints from an inbred C57/BL1/6 (ICRFa) mouse colony were harvested at 3-30 months of age. Sections were stained with H&E, Safranin-O, Picro-sirius red and antibodies to matrix metalloproteinase-13 (MMP-13), nitrotyrosine, LC-3B, Bcl-2, and cleaved type II collagen used for immunohistochemistry.

Baseline serum MMP-3 levels in patients with Rheumatoid Arthritis are still independently predictive of radiographic progression in a longitudinal observational cohort at 8 years follow up.

Introduction: At present, there is no reliable tool for predicting disease outcome in patients with rheumatoid arthritis (RA). We previously demonstrated an association between specific baseline biomarkers/clinical measures including matrix metalloproteinase-3 (MMP-3) and 2-year radiographic progression in patients with RA. This study further evaluates the predictive capability of these baseline variables with outcome extended over 8-years.

Leptin produced by joint white adipose tissue induces cartilage degradation via upregulation and activation of matrix metalloproteinases.

Objectives: To investigate the effect of leptin on cartilage destruction.

Methods: Collagen release was assessed in bovine cartilage explant cultures, while collagenolytic and gelatinolytic activities in culture supernatants were determined by bioassay and gelatin zymography. The expression of matrix metalloproteinases (MMP) was analysed by real-time RT-PCR.

Lipophilic statins prevent matrix metalloproteinase-mediated cartilage collagen breakdown by inhibiting protein geranylgeranylation.

Objective: To investigate if statins prevent cartilage degradation and the production of collagenases and gelatinases in bovine nasal and human articular cartilage after proinflammatory cytokine stimulation.

Methods: In a cartilage degradation model, the effects of several statins were assessed by measuring proteoglycan degradation and collagen degradation, while collagenolytic and gelatinolytic activity in culture supernatants were determined by collagen bioassay and gelatin zymography. The production of matrix metalloproteinases (MMPs) in cartilage and chondrocytes were analysed by real-time reverse transcriptase PCR and immunoassay.

Lithium protects cartilage from cytokine-mediated degradation by reducing collagen-degrading MMP production via inhibition of the P38 mitogen-activated protein kinase pathway.

Objectives: To determine the effects and mechanism of action of lithium chloride (LiCl) on cartilage destruction induced by the pro-inflammatory cytokines IL-1, IL-1 + oncostatin M and TNF-α.

Methods: The release of collagen was assessed in bovine cartilage explant cultures, whereas collagenolytic activities (active and total) in conditioned culture supernatants were determined by bioassay. The expression and production of MMP from chondrocytes were analysed by real-time RT-PCR and ELISA.

Matriptase is a novel initiator of cartilage matrix degradation in osteoarthritis.

Objective: Increasing evidence implicates serine proteinases in pathologic tissue turnover. The aim of this study was to assess the role of the transmembrane serine proteinase matriptase in cartilage destruction in osteoarthritis (OA).

Methods: Serine proteinase gene expression in femoral head cartilage obtained from either patients with hip OA or patients with fracture to the neck of the femur (NOF) was assessed using a low-density array.

HDAC-mediated control of ERK- and PI3K-dependent TGF-β-induced extracellular matrix-regulating genes.

Histone deacetylases (HDACs) regulate the acetylation of histones in the control of gene expression. Many non-histone proteins are also targeted for acetylation, including TGF-β signalling pathway components such as Smad2, Smad3 and Smad7. Our studies in mouse C3H10T1/2 fibroblasts suggested that a number of TGF-β-induced genes that regulate matrix turnover are selectively regulated by HDACs.

In vitro model of cartilage degradation.

This 14-day model of cartilage breakdown involves stimulation of bovine nasal cartilage with a combination of interleukin-1 and oncostatin M. Media is harvested on days 7 and 14 and the conditioned media and remaining cartilage at day 14 assayed for the levels of proteoglycan and collagen fragments using biochemical assays.

Proteinases involved in matrix turnover during cartilage and bone breakdown.

The joint is a discrete unit that consists of cartilage, bone, tendon and ligaments. These tissues are all composed of an extracellular matrix made of collagens, proteoglycans and specialised glycoproteins that are actively synthesised, precisely assembled and subsequently degraded by the resident connective tissue cells. A balance is maintained between matrix synthesis and degradation in healthy adult tissues.

Sulfasalazine blocks the release of proteoglycan and collagen from cytokine stimulated cartilage and down-regulates metalloproteinases.

Objective: To investigate the effect of SSZ on the release of GAG and collagen fragments from bovine nasal cartilage and MMP and ADAMTS (a disintegrin and metalloproteinase domain with thrombospondin motifs) proteinases from human articular chondrocytes (HACs) stimulated with IL-1alpha and oncostatin M (OSM).

Methods: SSZ was added to bovine nasal explant cultures stimulated to resorb with IL-1alpha and OSM, and the release of GAG and collagen has been determined. Collagenolytic activity was measured using the radio-labelled collagen bioassay.

A novel paradigm for dendritic cells as effectors of cartilage destruction.

Objective: Dendritic cells (DCs) are enriched in RA synovium and have been implicated in the pathogenesis of RA primarily through their ability to present autoantigen and activate T cells. However, whether DCs play an effector role in cartilage destruction is unknown. The aim of this study was to investigate whether DCs can induce collagen release from cartilage and the mechanism involved.

Measurement of activity of collagenolytic MMP and inhibitors of MMPs using radiolabeled collagen substrate.

This protocol describes how to purify and radiolabel collagen for use as a substrate to assay collagenolytic members of the matrix metalloproteinases (MMPs). This assay measures enzymes that specifically cleave native triple helical collagen. After incubation of the MMP enzyme with the collagen substrate at 37 degrees C, undigested collagen is removed by centrifugation.

Synergistic collagenase expression and cartilage collagenolysis are phosphatidylinositol 3-kinase/Akt signaling-dependent.

The phosphatidylinositol 3-kinase (PI3K) signaling pathway has emerged as a major regulator of cellular functions and has been implicated in several pathologies involving remodeling of extracellular matrix (ECM). The end stage of inflammatory joint diseases is characterized by excessive ECM catabolism, and in this study we assess the role of PI3K signaling in the induction of collagenolytic matrix metalloproteinases (MMPs) in human chondrocytes. We used the most potent cytokine stimulus reported to promote cartilage ECM catabolism, namely interleukin-1 (IL-1) in combination with oncostatin M (OSM).

Assessment of collagenase activity in cartilage.

Assay of collagenase activity involves the use of radiolabeled collagen. Stimulation of cartilage with proinflammatory cytokines results in the upregulation of collagenases and the subsequent release of degraded collagen fragments. These enzymes can be localized in both osteoarthritic and rheumatoid arthritis cartilage and synovial tissues.

Research in hand osteoarthritis: time for reappraisal and demand for new strategies. An opinion paper.

Background: Osteoarthritis of the hands is a prevalent musculoskeletal disease with a considerable effect on patients' lives, but knowledge and research results in the field of hand osteoarthritis are limited. Therefore, the Disease Characteristics in Hand OA (DICHOA) initiative was founded in early 2005 with the aim of addressing key issues and facilitating research into hand osteoarthritis.

Objective: To review and discuss current knowledge on hand osteoarthritis with regard to aetiopathogenesis, diagnostic criteria, biomarkers and clinical outcome measures.

Activity of matrix metalloproteinase-9 against native collagen types I and III.

Interstitial collagen types I, II and III are highly resistant to proteolytic attack, due to their triple helical structure, but can be cleaved by matrix metalloproteinase (MMP) collagenases at a specific site, approximately three-quarters of the length from the N-terminus of each chain. MMP-2 and -9 are closely related at the structural level, but MMP-2, and not MMP-9, has been previously described as a collagenase. This report investigates the ability of purified recombinant human MMP-9 produced in insect cells to degrade native collagen types I and III.

The phosphodiesterase type IV inhibitor cilomilast decreases pro-inflammatory cytokine production from primary bronchial epithelial cells in lung transplantation patients.

Background: Bronchiolitis obliterans syndrome (BOS) remains the major cause of long-term morbidity and mortality after lung transplantation, and new therapeutic measures are needed. We speculated that cilomilast might reduce mediators of airway inflammation and angiogenesis from the airway epithelium, supporting a potential value in the treatment of BOS. We used an ex vivo primary bronchial epithelial cell culture (PBEC) model to investigate this hypothesis.

Understanding the role of tissue degrading enzymes and their inhibitors in development and disease.

Cartilage and the underlying bone are destroyed in severe cases of arthritis preventing joints from functioning normally. Cartilage and bone collagen can be specifically cleaved by the collagenases, members of the matrix metalloproteinase family (MMPs), whilst cartilage aggrecan is degraded by members of the ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin repeats) family of proteinases. Intracellular cysteine proteinases are involved in bone resorption by osteoclasts and the serine proteinases are involved in activating MMPs.

Metalloproteinase and inhibitor expression profiling of resorbing cartilage reveals pro-collagenase activation as a critical step for collagenolysis.

Excess proteolysis of the extracellular matrix (ECM) of articular cartilage is a key characteristic of arthritis. The main enzymes involved belong to the metalloproteinase family, specifically the matrix metalloproteinases (MMPs) and a group of proteinases with a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS). Chondrocytes are the only cell type embedded in the cartilage ECM, and cell-matrix interactions can influence gene expression and cell behaviour.

The mammalian chitinase-like lectin, YKL-40, binds specifically to type I collagen and modulates the rate of type I collagen fibril formation.

YKL-40 is expressed in arthritic cartilage and produced in large amounts by cultured chondrocytes, but its exact role is unclear, and the identities of its physiological ligands remain unknown. Purification of YKL-40 from resorbing bovine nasal cartilage and chondrocyte monolayers demonstrated the existence of three isoforms, a major and minor form from resorbing cartilage and a third species from chondrocytes. Affinity chromatography experiments with purified YKL-40 demonstrated specific binding of all three forms to collagen types I, II, and III, thus identifying collagens as potential YKL-40 ligands.

Matrix metalloproteinase knockout studies and the potential use of matrix metalloproteinase inhibitors in the rheumatic diseases.

The matrix metalloproteinases (MMPs) comprise a family of enzymes that collectively can degrade all components of the extracellular matrix (ECM). MMPs play an important role in many physiological processes such as embryonic development and growth, tissue remodelling and repair. Overexpression and activation of MMPs contributes to many pathologies, including arthritis, cardiovascular disease, tumour progression and lung disease.

A model of inflammatory arthritis highlights a role for oncostatin M in pro-inflammatory cytokine-induced bone destruction via RANK/RANKL.

Oncostatin M is a pro-inflammatory cytokine previously shown to promote marked cartilage destruction both in vitro and in vivo when in combination with IL-1 or tumour necrosis factor alpha. However, the in vivo effects of these potent cytokine combinations on bone catabolism are unknown. Using adenoviral gene transfer, we have overexpressed oncostatin M in combination with either IL-1 or tumour necrosis factor alpha intra-articularly in the knees of C57BL/6 mice.

Cytokine synergy, collagenases and cartilage collagen breakdown.

We have investigated proteinases that degrade cartilage collagen. We show that pro-inflammatory cytokines act synergistically with oncastatin M to promote cartilage collagen resorption by the up-regulation and activation of matrix metalloproteinases (MMPs). The precise mechanisms are not known, but involve the up-regulation of c-fos, which binds to MMP promoters at a proximal activator protein-1 (AP-1) site.