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1.  Macrophage migration inhibitory factor: a mediator of matrix metalloproteinase-2 production in rheumatoid arthritis 
Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by destruction of bone and cartilage, which is mediated, in part, by synovial fibroblasts. Matrix metalloproteinases (MMPs) are a large family of proteolytic enzymes responsible for matrix degradation. Macrophage migration inhibitory factor (MIF) is a cytokine that induces the production of a large number of proinflammatory molecules and has an important role in the pathogenesis of RA by promoting inflammation and angiogenesis.
In the present study, we determined the role of MIF in RA synovial fibroblast MMP production and the underlying signaling mechanisms. We found that MIF induces RA synovial fibroblast MMP-2 expression in a time-dependent and concentration-dependent manner. To elucidate the role of MIF in MMP-2 production, we produced zymosan-induced arthritis (ZIA) in MIF gene-deficient and wild-type mice. We found that MMP-2 protein levels were significantly decreased in MIF gene-deficient compared with wild-type mice joint homogenates. The expression of MMP-2 in ZIA was evaluated by immunohistochemistry (IHC). IHC revealed that MMP-2 is highly expressed in wild-type compared with MIF gene-deficient mice ZIA joints. Interestingly, synovial lining cells, endothelial cells, and sublining nonlymphoid mononuclear cells expressed MMP-2 in the ZIA synovium. Consistent with these results, in methylated BSA (mBSA) antigen-induced arthritis (AIA), a model of RA, enhanced MMP-2 expression was also observed in wild-type compared with MIF gene-deficient mice joints. To elucidate the signaling mechanisms in MIF-induced MMP-2 upregulation, RA synovial fibroblasts were stimulated with MIF in the presence of signaling inhibitors. We found that MIF-induced RA synovial fibroblast MMP-2 upregulation required the protein kinase C (PKC), c-jun N-terminal kinase (JNK), and Src signaling pathways. We studied the expression of MMP-2 in the presence of PKC isoform-specific inhibitors and found that the PKCδ inhibitor rottlerin inhibits MIF-induced RA synovial fibroblast MMP-2 production. Consistent with these results, MIF induced phosphorylation of JNK, PKCδ, and c-jun. These results indicate a potential novel role for MIF in tissue destruction in RA.
doi:10.1186/ar2021
PMCID: PMC1779381  PMID: 16872482
2.  MT1-MMP is a crucial promotor of synovial invasion in human rheumatoid arthritis 
Arthritis and rheumatism  2009;60(3):686.
Objective
A hallmark of rheumatoid arthritis (RA) is invasion of the synovial pannus into cartilage and this step requires degradation of the collagen matrix. The aim of this study was to explore the role of one of the collagen-degrading matrix metalloproteinases (MMPs), membrane-type 1 MMP (MT1-MMP), in synovial pannus invasiveness.
Methods
Expression and localization of MT1-MMP in human RA pannus were investigated by Western blot analysis of primary synovial cells and immunohistochemistry of RA joints specimens. The functional role of MT1-MMP was analyzed by 3D collagen invasion assays and a cartilage invasion assay in the presence or absence of tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, or GM6001. The effect of adenoviral expression of a dominant negative MT1-MMP construct lacking a catalytic domain was also examined.
Results
MT1-MMP was highly expressed at the pannus-cartilage junction of RA joints. Freshly isolated rheumatoid synovial tissues and isolated RA synovial fibroblasts invaded into a 3D collagen matrix in an MT1-MMP-dependent manner. Invasion was blocked by TIMP-2 and GM6001, but not by TIMP-1. It was also inhibited by the over-expression of a dominant negative MT1-MMP which inhibits collagenolytic activity and proMMP-2 activation by MT1-MMP on the cell surface. Synovial fibroblasts also invaded into cartilage in an MT1-MMP-dependent manner. This process was further enhanced by removing aggrecan from the cartilage matrix.
Conclusion
MT1-MMP is an essential collagen-degrading proteinase during pannus invasion in human RA. Specific inhibition of MT1-MMP-dependent invasion may form a novel therapeutic strategy for RA.
doi:10.1002/art.24331
PMCID: PMC2819053  PMID: 19248098
MT1-MMP; synovial pannus; rheumatoid arthritis
3.  Transcriptional regulation of collagenase (MMP-1, MMP-13) genes in arthritis: integration of complex signaling pathways for the recruitment of gene-specific transcription factors 
Arthritis Research  2001;4(3):157-164.
Matrix metalloproteinase (MMP)-1, MMP-8 and MMP-13 are interstitial collagenases that degrade type II collagen in cartilage; this is a committed step in the progression of rheumatoid arthritis and osteoarthritis. Of these enzymes, the expression of MMP-1 and MMP-13 is substantially increased in response to IL-1 and tumor necrosis factor-α, and elevated levels of these collagenases are observed in arthritic tissues. Therefore, cytokine-mediated MMP-1 and MMP-13 gene regulation is an important issue in arthritis research. In this review, we discuss current models of MMP-1 and MMP-13 transcriptional regulation, with a focus on signaling intermediates and transcription factors that may be future targets for the development of new arthritis drugs.
PMCID: PMC128926  PMID: 12010565
arthritis; matrix metalloproteinases; mitogen-activated protein kinases; nuclear factor κB; transcription
4.  Induction of multiple matrix metalloproteinases in human dermal and synovial fibroblasts by Staphylococcus aureus: implications in the pathogenesis of septic arthritis and other soft tissue infections 
Infections of body tissue by Staphylococcus aureus are quickly followed by degradation of connective tissue. Patients with rheumatoid arthritis are more prone to S. aureus-mediated septic arthritis. Various types of collagen form the major structural matrix of different connective tissues of the body. These different collagens are degraded by specific matrix metalloproteinases (MMPs) produced by fibroblasts, other connective tissue cells, and inflammatory cells that are induced by interleukin-1 (IL-1) and tumor necrosis factor (TNF). To determine the host's contribution in the joint destruction of S. aureus-mediated septic arthritis, we analyzed the MMP expression profile in human dermal and synovial fibroblasts upon exposure to culture supernatant and whole cell lysates of S. aureus. Human dermal and synovial fibroblasts treated with cell lysate and filtered culture supernatants had significantly enhanced expression of MMP-1, MMP-2, MMP-3, MMP-7, MMP-10, and MMP-11 compared with the untreated controls (p < 0.05). In the S. aureus culture supernatant, the MMP induction activity was identified to be within the molecular-weight range of 30 to >50 kDa. The MMP expression profile was similar in fibroblasts exposed to a combination of IL-1/TNF. mRNA levels of several genes of the mitogen-activated protein kinase (MAPK) signal transduction pathway were significantly elevated in fibroblasts treated with S. aureus cell lysate and culture supernatant. Also, tyrosine phosphorylation was significantly higher in fibroblasts treated with S. aureus components. Tyrosine phosphorylation and MAPK gene expression patterns were similar in fibroblasts treated with a combination of IL-1/TNF and S. aureus. Mutants lacking staphylococcal accessory regulator (Sar) and accessory gene regulator (Agr), which cause significantly less severe septic arthritis in murine models, were able to induce expression of several MMP mRNA comparable with that of their isogenic parent strain but induced notably higher levels of tissue inhibitors of metalloproteinases (TIMPs). To our knowledge, this is the first report of induction of multiple MMP/TIMP expression from human dermal and synovial fibroblasts upon S. aureus treatment. We propose that host-derived MMPs contribute to the progressive joint destruction observed in S. aureus-mediated septic arthritis.
doi:10.1186/ar2086
PMCID: PMC1794521  PMID: 17129374
5.  Inhibition of cartilage and bone destruction in adjuvant arthritis in the rat by a matrix metalloproteinase inhibitor 
Considerable evidence has associated the expression of matrix metalloproteinases (MMPs) with the degradation of cartilage and bone in chronic conditions such as arthritis. Direct evaluation of MMPs' role in vivo has awaited the development of MMP inhibitors with appropriate pharmacological properties. We have identified butanediamide, N4- hydroxy-2-(2-methylpropyl)-N1-[2-[[2-(morpholinyl)ethyl]-,[S- (R*,S*)] (GI168) as a potent MMP inhibitor with sufficient solubility and stability to permit evaluation in an experimental model of chronic destructive arthritis (adjuvant-induced arthritis) in rats. In this model, pronounced acute and chronic synovial inflammation, distal tibia and metatarsal marrow hyperplasia associated with osteoclasia, severe bone and cartilage destruction, and ectopic new bone growth are well developed by 3 wk after adjuvant injection. Rats were injected with Freund's adjuvant on day 0. GI168 was was administered systemically from days 8 to 21 by osmotic minipumps implanted subcutaneously. GI168 at 6, 12, and 25 mg/kg per d reduced ankle swelling in a dose-related fashion. Radiological and histological ankle joint evaluation on day 22 revealed a profound dose related inhibition of bone and cartilage destruction in treated rats relative to rats receiving vehicle alone. A significant reduction in edema, pannus formation, periosteal new bone growth and the numbers of adherent marrow osteoclasts was also noted. However, no significant decrease in polymorphonuclear and mononuclear leukocyte infiltration of synovium and marrow hematopoietic cellularity was seen. This unique profile of antiarthritic activity indicates that GI168 is osteo- and chondro-protective, and it supports a direct role for MMP in cartilage and bone damage and pannus formation in adjuvant- induced arthritis.
PMCID: PMC2192113  PMID: 7629505
6.  Collagenase-3 (MMP-13) deficiency protects C57BL/6 mice from antibody-induced arthritis 
Arthritis Research & Therapy  2013;15(6):R222.
Introduction
Matrix metalloproteinases (MMPs) are important in tissue remodelling. Here we investigate the role of collagenase-3 (MMP-13) in antibody-induced arthritis.
Methods
For this study we employed the K/BxN serum-induced arthritis model. Arthritis was induced in C57BL/6 wild type (WT) and MMP-13-deficient (MMP-13–/–) mice by intraperitoneal injection of 200 μl of K/BxN serum. Arthritis was assessed by measuring the ankle swelling. During the course of the experiments, mice were sacrificed every second day for histological examination of the ankle joints. Ankle sections were evaluated histologically for infiltration of inflammatory cells, pannus tissue formation and bone/cartilage destruction. Semi-quantitative PCR was used to determine MMP-13 expression levels in ankle joints of untreated and K/BxN serum-injected mice.
Results
This study shows that MMP-13 is a regulator of inflammation. We observed increased expression of MMP-13 in ankle joints of WT mice during K/BxN serum-induced arthritis and both K/BxN serum-treated WT and MMP-13–/– mice developed progressive arthritis with a similar onset. However, MMP-13–/– mice showed significantly reduced disease over the whole arthritic period. Ankle joints of WT mice showed severe joint destruction with extensive inflammation and erosion of cartilage and bone. In contrast, MMP-13–/– mice displayed significantly decreased severity of arthritis (50% to 60%) as analyzed by clinical and histological scoring methods.
Conclusions
MMP-13 deficiency acts to suppress the local inflammatory responses. Therefore, MMP-13 has a role in the pathogenesis of arthritis, suggesting MMP-13 is a potential therapeutic target.
doi:10.1186/ar4423
PMCID: PMC3979078  PMID: 24369907
7.  Immunolocalization of matrix metalloproteinase 3 (stromelysin) in rheumatoid synovioblasts (B cells): correlation with rheumatoid arthritis. 
Annals of the Rheumatic Diseases  1989;48(8):645-653.
Metalloproteinases produced by connective tissue cells may play a key part in the destruction of joints in rheumatoid arthritis. Matrix metalloproteinase 3 (MMP-3; stromelysin) capable of degrading cartilage proteoglycans and type IX collagen and of activating procollagenase was immunolocalised in hyperplastic synovial lining cells in rheumatoid synovium, but not in the cells of normal synovium. Cells responsible for synthesis of MMP-3 have the phenotype of synovioblasts (B cells) by immunoelectron microscopy, but not of phagocytic synovial macrophages (A cells). Cultured monolayer of rheumatoid synovial cells synthesises MMP-3 only under treatment with macrophage conditioned medium. Immunolocalisation of MMP-3 in rheumatoid synovium and cultured synovial cells was possible when the specimens were treated with a monovalent ionophore, monensin. These results suggest that MMP-3 is synthesised and secreted continuously without storage from hyperplastic synovioblasts stimulated by factor(s) derived from activated macrophages present in the synovium.
Images
PMCID: PMC1003840  PMID: 2675782
8.  Matrix metalloproteinase protein expression profiles cannot distinguish between normal and early osteoarthritic synovial fluid 
Background
Osteoarthritis (OA) and Rheumatoid arthritis (RA) are diseases which result in the degeneration of the joint surface articular cartilage. Matrix Metalloproteinases (MMPs) are enzymes that aid in the natural remodelling of tissues throughout the body including cartilage. However, some MMPs have been implicated in the progression of OA and RA as their expression levels and activation states can change dramatically with the onset of disease. Yet, it remains unknown if normal and arthritic joints demonstrate unique MMPs expression profiles, and if so, can the MMP expression profile be used to identify patients with early OA. In this study, the synovial fluid protein expression levels for MMPs 1, 2, 3, 7, 8, 9, 12 & 13, as well as those for the Tissue Inhibitors of MMPs (TIMPs) 1, 2, 3, & 4 were examined in highly characterized normal knee joints, and knee joints with clinically diagnosed OA (early and advanced) or RA. The purpose of this study was to determine if normal, OA, and RA patients exhibit unique expression profiles for a sub-set of MMPs, and if early OA patients have a unique MMP expression profile that could be used as an early diagnostic marker.
Methods
Synovial fluid was aspirated from stringently characterized normal knee joints, and in joints diagnosed with either OA (early and advanced) or RA. Multiplexing technology was employed to quantify protein expression levels for 8 MMPs and 4 TIMPs in the synovial fluid of 12 patients with early OA, 17 patients diagnosed with advanced OA, 15 with RA and 25 normal knee joints. Principle component analysis (PCA) was used to reveal which MMPs were most influential in the distinction between treatment groups. K – means clustering was used to verify the visual grouping of subjects via PCA.
Results
Significant differences in the expression levels of MMPs and TIMPs were observed between normal and arthritic synovial fluids (with the exception of MMP 12). PCA demonstrated that MMPs 2, 8 & 9 can be used to effectively separate individuals diagnosed with advanced arthritis from early osteoarthritic and normal individuals, however, these MMP profiles do not separate early OA from normal synovial fluid. An apparent separation between advanced OA and RA subjects was also revealed through PCA. K-means clustering verified the presence of 3 clusters: normal joints clustered with early OA, and separate clusters of advanced OA or RA.
Conclusions
This study demonstrates that unique MMP and TIMP expression profiles are present within normal, advanced OA and RA synovial fluid. These MMP profiles can be used to distinguish advanced OA & RA synovial fluid from early OA & normal synovial fluid, and even between synovial fluid samples from OA and RA joints. Although this methodology cannot be used for the diagnosis of early OA, high throughput multiplex technology of MMPs and TIMPs in synovial fluid may prove useful in determining the severity of the disease state, and/or quantifying the response of individuals to disease interventions.
doi:10.1186/1471-2474-13-126
PMCID: PMC3532375  PMID: 22824140
9.  High throughput screening of potentially selective MMP-13 exosite inhibitors utilizing a triple-helical FRET substrate 
Bioorganic & medicinal chemistry  2008;17(3):990-1005.
The major components of the cartilage extracellular matrix are type II collagen and aggrecan. Matrix metalloproteinase 13 (MMP-13) has been implicated as the protease responsible for collagen degradation in cartilage during osteoarthritis (OA). In the present study, a triple-helical FRET substrate has been utilized for high throughput screening (HTS) of MMP-13 with the MLSCN compound library (n ~ 65,000). Thirty-four compounds from the HTS produced pharmacological dose-response curves. A secondary screen using RP-HPLC validated 25 compounds as MMP-13 inhibitors. Twelve of these compounds were selected for counter-screening with 6 representative MMP family members. Five compounds were found to be broad-spectrum MMP inhibitors, 3 inhibited MMP-13 and one other MMP, and 4 were selective for MMP-13. One of the selective inhibitors was more active against MMP-13 triple-helical peptidase activity compared with single-stranded peptidase activity. Since the THP FRET substrate has distinct conformational features that may interact with MMP secondary binding sites (exosites), novel non-active site binding inhibitors may be identified via HTS protocols utilizing such assays.
doi:10.1016/j.bmc.2008.03.004
PMCID: PMC3298815  PMID: 18358729
10.  Matrix metalloproteinases and tissue inhibitors of metalloproteinases in synovial fluids from patients with rheumatoid arthritis or osteoarthritis 
Annals of the Rheumatic Diseases  2000;59(6):455-461.
OBJECTIVE—Matrix metalloproteinases (MMPs) are expressed in joint tissues of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). The objective of this study was to define the steady state levels of seven different MMPs and two tissue inhibitors of metalloproteinases (TIMPs) as well as the potential metalloproteinase activity in the synovial fluid (SF) to provide more insight into the role of MMPs in cartilage destruction in RA and OA.
METHODS—Levels of MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-13, TIMP-1, and TIMP-2 in SF aspirated from knee joints of 97 patients with RA and 103 patients with OA were measured by the corresponding one step sandwich enzyme immunoassays. Proteolytic activity of MMPs in these SFs was examined in an assay using [3H]carboxymethylated transferrin substrate in the presence of inhibitors of serine and cysteine proteinases after activation with p-aminophenylmercuric acetate (APMA). Destruction of RA knee joints was radiographically evaluated.
RESULTS—Levels of MMP-1, MMP-2, MMP-3, MMP-8, and MMP-9 were significantly higher in RA SF than in OA SF. MMP-7 and MMP-13 were detectable in more than 45% of RA SFs and in less than 20% of OA SFs, respectively. Among the MMPs examined, MMP-3 levels were extremely high compared with those of other MMPs. Direct correlations were seen between the levels of MMP-1 and MMP-3 and between those of MMP-8 and MMP-9 in RA SF. Although the levels of MMP-1 and MMP-3 increased even in the early stage of RA, those of MMP-8 and MMP-9 were low in the early stage and increased with the progression of RA. Molar ratios of the total amounts of the MMPs to those of the TIMPs were 5.2-fold higher in patients with RA than in OA, which was significant. APMA-activated metalloproteinase activity in SF showed a similar result, and a direct correlation was seen between the molar ratios and the activity in RA SF.
CONCLUSIONS—Our results show that high levels of MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, and TIMP-1 are present in RA SF and suggest that once these MMPs are fully activated, they have an imbalance against TIMPs, which may contribute to the cartilage destruction in RA.


doi:10.1136/ard.59.6.455
PMCID: PMC1753174  PMID: 10834863
11.  Hypoxia upregulates angiogenesis and synovial cell migration in rheumatoid arthritis 
Introduction
Rheumatoid arthritis (RA) is characterised by invasion of cartilage, bone and tendon by inflamed synovium. Previous studies in our laboratory have shown that hypoxia is a feature of RA synovitis. In the present study, we investigated the consequences of hypoxia on angiogenesis and synovial fibroblast migration in RA.
Methods
Synovial tissue was harvested from RA patients, and synovial membrane cells were cultured under conditions either of hypoxia (1% oxygen) or normoxia (21% oxygen). Protein levels of matrix metalloproteinases (MMPs) and angiogenic factors were measured, while RNA was extracted for PCR quantification of MMPs/tissue inhibitors of MMP (TIMPs) and angiogenic factors. Migration of RA synovial fibroblasts through collagen, and the effect of RA synovial cell supernatants in an in vitro angiogenesis assay, were utilised to determine the functional relevance of changes in mRNA/protein.
Results
We observed upregulation under hypoxic conditions of MMPs responsible for collagen breakdown, specifically collagenase MMP-8, and the gelatinases MMP-2 and MMP-9, at both mRNA and protein levels. Increased MT1-MMP mRNA was also observed, but no effect on TIMP-1 or TIMP-2 was detected. RA fibroblast migration across collagen was significantly increased under hypoxic conditions, and was dependent on MMP activity. Furthermore, expression of angiogenic stimuli, such as vascular endothelial growth factor (VEGF), and VEGF/placental growth factor heterodimer, was also increased. Crucially, we show for the first time that hypoxia increased the angiogenic drive of RA cells, as demonstrated by enhanced blood vessel formation in an in vitro angiogenesis assay.
Conclusions
Hypoxia may be responsible for rendering RA synovial lining proangiogenic and proinvasive, thus leading to the debilitating features characteristic of RA.
doi:10.1186/ar2689
PMCID: PMC2714109  PMID: 19426483
12.  Over-expression of extracellular superoxide dismutase in mouse synovial tissue attenuates the inflammatory arthritis 
Experimental & Molecular Medicine  2012;44(9):529-535.
Oxidative stress such as reactive oxygen species (ROS) within the inflamed joint have been indicated as being involved as inflammatory mediators in the induction of arthritis. Correlations between extracellular-superoxide dismutase (EC-SOD) and inflammatory arthritis have been shown in several animal models of RA. However, there is a question whether the over-expression of EC-SOD on arthritic joint also could suppress the progression of disease or not. In the present study, the effect on the synovial tissue of experimental arthritis was investigated using EC-SOD over-expressing transgenic mice. The over-expression of EC-SOD in joint tissue was confirmed by RT-PCR and immunohistochemistry. The degree of the inflammation in EC-SOD transgenic mice was suppressed in the collagen-induced arthritis model. In a cytokine assay, the production of pro-inflammatory cytokines such as, IL-1β, TNFα, and matrix metalloproteinases (MMPs) was decreased in fibroblast-like synoviocyte (FLS) but not in peripheral blood. Histological examination also showed repressed cartilage destruction and bone in EC-SOD transgenic mice. In conclusion, these data suggest that the over-expression of EC-SOD in FLS contributes to the activation of FLS and protection from joint destruction by depressing the production of the pro-inflammatory cytokines and MMPs. These results provide EC-SOD transgenic mice with a useful animal model for inflammatory arthritis research.
doi:10.3858/emm.2012.44.9.060
PMCID: PMC3465746  PMID: 22718219
arthritis, experimental; reactive oxygen species; rheumatoid arthritis; superoxide dismutase; synovial membrane
13.  Matrix metalloproteinase-8 deficiency increases joint inflammation and bone erosion in the K/BxN serum-transfer arthritis model 
Arthritis Research & Therapy  2010;12(6):R224.
Introduction
Rheumatoid arthritis is an autoimmune disease in which joint inflammation leads to progressive cartilage and bone erosion. Matrix metalloproteinases (MMPs) implicated in homeostasis of the extracellular matrix play a central role in cartilage degradation. However, the role of specific MMPs in arthritis pathogenesis is largely unknown. The aim of the present study was to investigate the role of Mmp-8 (collagenase-2) in an arthritis model.
Methods
Arthritis was induced in Mmp8-deficient and wildtype mice by K/BxN serum transfer. Arthritis severity was measured by a clinical index and ankle sections were scored for synovial inflammation, cartilage damage and bone erosion. cDNA microarray analysis, real-time PCR and western blot were performed to identify differential changes in gene expression between mice lacking Mmp8 and controls.
Results
Mmp8 deficiency increased the severity of arthritis, although the incidence of disease was similar in control and deficient mice. Increased clinical score was associated with exacerbated synovial inflammation and bone erosion. We also found that the absence of Mmp8 led to increased expression of IL-1β, pentraxin-3 (PTX3) and prokineticin receptor 2 (PROKR2) in arthritic mice joints.
Conclusions
Lack of Mmp-8 is accompanied by exacerbated synovial inflammation and bone erosion in the K/BxN serum-transfer arthritis model, indicating that this Mmp has a protective role in arthritis.
doi:10.1186/ar3211
PMCID: PMC3046537  PMID: 21190566
14.  Basic Fibroblast Growth Factor Stimulates Matrix Metalloproteinase-13 via the Molecular Cross-talk between the Mitogen-activated Protein Kinases and Protein Kinase Cδ Pathways in Human Adult Articular Chondrocytes* 
The Journal of biological chemistry  2007;282(15):11110-11121.
Excessive release of basic fibroblast growth factor (bFGF) during loading and/or injury of the cartilage matrix may contribute to the onset or progression of osteoarthritis. This pathological role may be related to the ability of bFGF to decrease proteoglycan synthesis and to antagonize the activity of anabolic growth factors in cartilage such as insulin-like growth factor-1 and bone morphogenetic protein 7 (BMP7 or OP-1). Matrix metalloproteinase-13 (MMP-13), a catabolic cartilage-degrading enzyme, is dramatically up-regulated by inflammatory cytokines or by fibronectin fragments in articular chondrocytes. In this study, we investigated MMP-13 production by bFGF using human articular chondrocytes. Endogenous concentration of bFGF in synovial fluids collected from arthritis patients and asymptomatic subjects showed a good linear correlation with the endogenous levels of MMP-13. bFGF stimulation of MMP-13 was mediated at the transcriptional level and, at least in part, by stimulation of interleukin-1 production. Also, our findings suggest that bFGF stimulation of MMP-13 required the activation of multiple MAPKs (ERK, p38, and JNK) by bFGF, and more importantly, bFGF activation of protein kinase C (PKC) δ played a key role in the MMP-13 stimulation. Indeed, PKCδ is the only isoform associated with MMP-13 stimulation among the PKC isoforms tested. PKCδ controls the bFGF response by regulating multiple MAPK pathways. Our results suggest that PKCδ activation is a principal rate-limiting event in the bFGF-dependent stimulation of MMP-13 in human adult articular chondrocytes. We propose that deregulation of cross-talk between MAPK and PKCδ signaling may contribute to the etiology of osteoarthritis in human patients.
doi:10.1074/jbc.M609040200
PMCID: PMC2895271  PMID: 17311929
15.  Local IL-13 gene transfer prior to immune-complex arthritis inhibits chondrocyte death and matrix-metalloproteinase-mediated cartilage matrix degradation despite enhanced joint inflammation 
Arthritis Research & Therapy  2005;7(2):R392-R401.
During immune-complex-mediated arthritis (ICA), severe cartilage destruction is mediated by Fcγ receptors (FcγRs) (mainly FcγRI), cytokines (e.g. IL-1), and enzymes (matrix metalloproteinases (MMPs)). IL-13, a T helper 2 (Th2) cytokine abundantly found in synovial fluid of patients with rheumatoid arthritis, has been shown to reduce joint inflammation and bone destruction during experimental arthritis. However, the effect on severe cartilage destruction has not been studied in detail. We have now investigated the role of IL-13 in chondrocyte death and MMP-mediated cartilage damage during ICA. IL-13 was locally overexpressed in knee joints after injection of an adenovirus encoding IL-13 (AxCAhIL-13), 1 day before the onset of arthritis; injection of AxCANI (an empty adenoviral construct) was used as a control. IL-13 significantly increased the amount of inflammatory cells in the synovial lining and the joint cavity, by 30% to 60% at day 3 after the onset of ICA. Despite the enhanced inflammatory response, chondrocyte death was diminished by two-thirds at days 3 and 7. The mRNA level of FcγRI, a receptor shown to be crucial in the induction of chondrocyte death, was significantly down-regulated in synovium. Furthermore, MMP-mediated cartilage damage, measured as neoepitope (VDIPEN) expression using immunolocalization, was halved. In contrast, mRNA levels of MMP-3, -9, -12, and -13 were significantly higher and IL-1 protein, which induces production of latent MMPs, was increased fivefold by IL-13. This study demonstrates that IL-13 overexpression during ICA diminished both chondrocyte death and MMP-mediated VDIPEN expression, even though joint inflammation was enhanced.
doi:10.1186/ar1502
PMCID: PMC1065337  PMID: 15743487
cartilage destruction; experimental arthritis; interleukin-13; Fcγ receptors; MMPs
16.  Cloning, expression, and type II collagenolytic activity of matrix metalloproteinase-13 from human osteoarthritic cartilage. 
Journal of Clinical Investigation  1996;97(3):761-768.
Proteolysis of triple-helical collagen is an important step in the progression toward irreversible tissue damage in osteoarthritis. Earlier work on the expression of enzymes in cartilage suggested that collagenase-1 (MMP-1) contributes to the process. Degenerate reverse transcription polymerase chain reaction experiments, Northern blot analysis, and direct immunodetection have now provided evidence that collagenase-3 (MMP-13), an enzyme recently cloned from human breast carcinoma, is expressed by chondrocytes in human osteoarthritic cartilage. Variable levels of MMP-13 and MMP-1 in cartilage was significantly induced at both the message and protein levels by interleukin-1 alpha. Recombinant MMP-13 cleaved type II collagen to give characteristic 3/4 and 1/4 fragments; however, MMP-13 turned over type II collagen at least 10 times faster than MMP-1. Experiments with intact type II collagen as well as a synthetic peptide suggested that MMP-13 cleaved type II collagen at the same bond as MMP-1, but this was then followed by a secondary cleavage that removed three amino acids from the 1/4 fragment amino terminus. The expression of MMP-13 in osteoarthritic cartilage and its activity against type II collagen suggest that the enzyme plays a significant role in cartilage collagen degradation, and must consequently form part of a complex target for proposed therapeutic interventions based on collagenase inhibition.
PMCID: PMC507114  PMID: 8609233
17.  Crystal Structure of an Active Form of Human MMP-1 
Journal of Molecular Biology  2006;362(1):78-88.
The extracellular matrix is a dynamic environment that constantly undergoes remodelling and degradation during vital physiological processes such as angiogenesis, wound healing, and development. Unbalanced extracellular matrix breakdown is associated with many diseases such as arthritis, cancer and fibrosis. Interstitial collagen is degraded by matrix metalloproteinases with collagenolytic activity by MMP-1, MMP-8 and MMP-13, collectively known as the collagenases. Matrix metalloproteinase 1 (MMP-1) plays a pivotal role in degradation of interstitial collagen types I, II, and III. Here, we report the crystal structure of the active form of human MMP-1 at 2.67 Å resolution. This is the first MMP-1 structure that is free of inhibitor and a water molecule essential for peptide hydrolysis is observed coordinated with the active site zinc. Comparing this structure with the human proMMP-1 shows significant structural differences, mainly in the relative orientation of the hemopexin domain, between the pro form and active form of the human enzyme.
doi:10.1016/j.jmb.2006.06.079
PMCID: PMC1885970  PMID: 16890240
MMP, matrix metalloproteinase; ECM, extracellular matrix; matrix metalloproteinases; fibroblast collagenase; collagen; X-ray crystallography; inhibitor-free
18.  Active synovial matrix metalloproteinase-2 is associated with radiographic erosions in patients with early synovitis 
Arthritis Research  2000;2(2):145-153.
Serum and synovial tissue expression of the matrix metalloproteinase (MMP)-2 and -9 and their molecular regulators, MMP-14 and TIMP-2 was examined in 28 patients with inflammatory early synovitis and 4 healthy volunteers and correlated with the presence of erosions in the patients. Immunohistological staining of MMP-2, MMP-14 and TIMP-2 localized to corresponding areas in the synovial lining layer and was almost absent in normal synovium. Patients with radiographic erosions had significantly higher levels of active MMP-2 than patients with no erosions, suggesting that activated MMP-2 levels in synovial tissue may be a marker for a more aggressive synovial lesion.
Introduction:
In cancer the gelatinases [matrix metalloproteinase (MMP)-2 and MMP-9] have been shown to be associated with tissue invasion and metastatic disease. In patients with inflammatory arthritis the gelatinases are expressed in the synovial membrane, and have been implicated in synovial tissue invasion into adjacent cartilage and bone. It is hypothesized that an imbalance between the activators and inhibitors of the gelatinases results in higher levels of activity, enhanced local proteolysis, and bone erosion.
Objectives:
To determine whether the expression and activity levels of MMP-2 and MMP-9, and their regulators MMP-14 and tissue inhibitor of metalloproteinase (TIMP), are associated with early erosion formation in patients with synovitis of recent onset.
Patients and method:
A subset of 66 patients was selected from a larger early synovitis cohort on the basis of tissue availability for the study of synovial tissue and serum gelatinase expression. Patients with peripheral joint synovitis of less than 1 years' duration were evaluated clinically and serologically on four visits over a period of 12 months. At the initial visit, patients underwent a synovial tissue biopsy of one swollen joint, and patients had radiographic evaluation of hands and feet initially and at 1year. Serum MMP-1, MMP-2, MMP-9, MMP-14, and TIMP-1 and TIMP-2 levels were determined, and synovial tissue was examined by immunohistology for the expression of MMP-2 and MMP-9, and their molecular regulators. Gelatinolytic activity for MMP-2 and MMP-9 was quantified using a sensitive, tissue-based gel zymography technique. Four healthy individuals underwent closed synovial biopsy and their synovial tissues were similarly analyzed.
Results:
Of the 66 patients studied, 45 fulfilled American College of Rheumatology criteria for rheumatoid arthritis (RA), with 32 (71%) being rheumatoid factor positive. Of the 21 non-RA patients, seven had a spondylarthropathy and 14 had undifferentiated arthritis. Radiographically, 12 of the RA patients had erosions at multiple sites by 1 year, whereas none of the non-RA patients had developed erosive disease of this extent. In the tissue, latent MMP-2 was widely expressed in the synovial lining layer and in areas of stromal proliferation in the sublining layer and stroma, whereas MMP-9 was expressed more sparsely and focally. MMP-14, TIMP-2, and MMP-2 were all detected in similar areas of the lining layer on consecutive histologic sections. Tissue expression of MMP-14, the activator for pro-MMP-2, was significantly higher in RA than in non-RA patients (8.4 ± 5 versus 3.7 ± 4 cells/high-power field; P = 0.009). In contrast, the expression of TIMP-2, an inhibitor of MMP-2, was lower in the RA than in the non-RA samples (25 ± 12 versus 39 ± 9 cells/high-power field; P = 0.01). Synovial tissue expressions of MMP-2, MMP-14, and TIMP-2 were virtually undetectable in normal synovial tissue samples. The synovial tissue samples of patients with erosive disease had significantly higher levels of active MMP-2 than did those of patients without erosions (Fig. 1). Tissue expression of MMP-2 and MMP-9, however, did not correlate with the serum levels of these enzymes.
With the exception of serum MMP-2, which was not elevated over normal, serum levels of all of the other MMPs and TIMPs were elevated to varying degrees, and were not predictive of erosive disease. Interestingly, MMP-1 and C-reactive protein, both of which were associated with the presence of erosions, were positively correlated with each other (r = 0.42; P < 0.001).
Discussion:
MMP-2 and MMP-9 are thought to play an important role in the evolution of joint erosions in patients with an inflammatory arthritis. Most studies have concentrated on the contribution of MMP-9 to the synovitis, because synovial fluid and serum MMP-9 levels are markedly increased in inflammatory arthropathies. Previously reported serum levels of MMP-9 have varied widely. In the present sample of patients with synovitis of recent onset, serum MMP-9 levels were elevated in only 21%. Moreover, these elevations were not specific for RA, the tissue expression of MMP-9 was focal, and the levels of MMP-9 activity were not well correlated with early erosions. Although serum MMP-2 levels were not of prognostic value, high synovial tissue levels of MMP-2 activity were significantly correlated with the presence of early erosions. This may reflect augmented activation of MMP-2 by the relatively high levels of MMP-14 and low levels of TIMP-2 seen in these tissues. We were able to localize the components of this trimolecular complex to the synovial lining layer in consecutive tissue sections, a finding that is consistent with their colocalization.
In conclusion, we have provided evidence that active MMP-2 complexes are detectable in the inflamed RA synovium and may be involved in the development of early bony erosions. These results suggest that strategies to inhibit the activation of MMP-2 may have the potential for retarding or preventing early erosions in patients with inflammatory arthritis.
PMCID: PMC17808  PMID: 11062605
early synovitis; erosion; metalloproteinase; matrix metalloproteinase-2; rheumatoid arthritis
19.  Differential expression patterns of matrix metalloproteinases and their inhibitors during development of osteoarthritis in a transgenic mouse model 
Annals of the Rheumatic Diseases  2002;61(7):591-597.
Objective: To characterise the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) during degeneration of articular cartilage in a transgenic Del1 mouse model for osteoarthritis.
Methods: Northern analysis was used to measure mRNA levels of MMP-2, -3, -8, -9, -13, and -14, and TIMP-1, -2, and -3 in total RNA extracted from knee joints of transgenic Del1 mice, harbouring a 15 amino acid deletion in the triple helical domain of the α1(II) collagen chain, using their non-transgenic littermates as controls. Immunohistochemistry was used to study the presence of cleavage products (neoepitopes) of type II collagen, and the distribution of MMP-13 and TIMP-1 in degenerating cartilage.
Results: Each of the MMP and TIMP mRNAs analysed exhibited distinct expression patterns during development and osteoarthritic degeneration of the knee joint. The most striking change was up regulation of MMP-13 mRNA expression in the knee joints of Del1 mice at the onset of cartilage degeneration. However, the strongest immunostaining for MMP-13 and its inhibitor TIMP-1 was not seen in the degenerating articular cartilage but in synovial tissue, deep calcified cartilage, and subchondral bone. The localisation of type II collagen neoepitopes in chondrocytes and their pericellular matrix followed a similar pattern; they were not seen in cartilage fibrillations, but in adjacent unaffected cartilage.
Conclusion: The primary localisation of MMP-13 and TIMP-1 in hyperplastic synovial tissue, subchondral bone, and calcified cartilage suggests that up regulation of MMP-13 expression during early degeneration of articular cartilage is a secondary response to cartilage erosion. This interpretation is supported by the distribution of type II collagen neoepitopes. Synovial production of MMP-13 may be related to removal of tissue debris released from articular cartilage. In the deep calcified cartilage and adjacent subchondral bone, MMP-13 probably participates in tissue remodelling.
doi:10.1136/ard.61.7.591
PMCID: PMC1754156  PMID: 12079898
20.  Hyaluronan modulates accumulation of hypoxia-inducible factor-1 alpha, inducible nitric oxide synthase, and matrix metalloproteinase-3 in the synovium of rat adjuvant-induced arthritis model 
Introduction
Hypoxia is a feature of the inflamed synovium in rheumatoid arthritis (RA). Intra-articular injection of hyaluronan (HA) may be considered a potential way to treat RA. However, the exact molecular mechanism of HA on decreased cellular responses to hypoxic environment is unclear. The present study has been designed to use the adjuvant-induced arthritis model to examine the effects of HA on the changes of immunohistochemical expressions of hypoxia-inducible factor-1alpha (HIF-1alpha), inducible nitric oxide synthase (iNOS), and matrix metalloproteinase-3 (MMP3) in the synovial tissues at the early phase of arthritic inflammation.
Methods
Monoarthritis was induced in adult male Sprague-Dawley (250-300 g) via intraarticular injection of complete Freund's adjuvant (CFA) into the tibiotarsal joint. The CFA-induction arthritis animals were divided into three groups: treatment (intraarticular injection of HA), placebo (intraarticular injection of saline) and controls (no treatments). Functional evaluations of edema and pain behavior, histology, and HIF-1alpha, iNOS, and MMP3 immunohistochemistry were performed before, after the first injection, three injections, and on the follow-up injection of the treatments.
Results
Intra-articular injection of HA also significantly suppressed the mechanical allodynia (p < 0.001) and overexpressions of HIF-1alpha (p < 0.001), iNOS (p = 0.004) and MMP3 (p < 0.001) immunoreactivity in synovium.
Conclusions
This study demonstrated that early intervention of HA is an effective protection against accumulation of inflammation-induced HIF-1alpha, iNOS, and MMP3 to limit erosive damage in CFA-induced model of arthritis.
doi:10.1186/ar3365
PMCID: PMC3218905  PMID: 21679445
21.  VDIPEN, a metalloproteinase-generated neoepitope, is induced and immunolocalized in articular cartilage during inflammatory arthritis. 
Journal of Clinical Investigation  1995;95(5):2178-2186.
The destruction of articular cartilage in immune inflammatory arthritic disease involves the proteolytic degradation of its extracellular matrix. The role of activated matrix metalloproteinases (MMPs) in the chondrodestructive process was studied by identifying a selective cleavage product of aggrecan in murine arthritis models initiated by immunization with either type II collagen or proteoglycan. We conducted semiquantitative immunocytochemical studies of VDIPEN341 using a monospecific polyclonal antibody requiring the free COOH group of the COOH-terminal Asn for epitope detection. This antibody recognizes the aggrecan G1 domain fragment generated by MMP [i.e., stromelysin (SLN) or gelatinase A] cleavage of aggrecan between Asn341-Phe342 but does not recognize intact aggrecan. VDIPEN was undetectable in normal mouse cartilage but was observed in the articular cartilage (AC) of mice with collagen-induced arthritis 10 d after immunization, without histological damage and clinical symptoms. This aggrecan neoepitope was colocalized with high levels of glycosaminoglycans (GAGs) in pericellular matrices of AC chondrocytes but was not seen at the articular surface at this early time. Digestion of normal (VDIPEN negative) mouse paw cryosections with SLN also produced heavy pericellular VDIPEN labeling. Computer-based image analysis showed that the amount of VDIPEN expression increased dramatically by 20 d (70% of the SLN maximum) and was correlated with GAG depletion. Both infiltration of inflammatory cells into the synovial cavity and early AC erosion were also very prominent at this time. Analysis of adjacent sections showed that both induction of VDIPEN and GAG depletion were strikingly codistributed within sites of articular cartilage damage. Similar results occurred in proteoglycan-induced arthritis, a more progressive and chronic model of inflammatory arthritis. These studies demonstrate for the first time the MMP-dependent catabolism of aggrecan at sites of chondrodestruction during inflammatory arthritis.
Images
PMCID: PMC295822  PMID: 7537757
22.  CD147 overexpression on synoviocytes in rheumatoid arthritis enhances matrix metalloproteinase production and invasiveness of synoviocytes 
Macrophage-like synoviocytes and fibroblast-like synoviocytes (FLS) are known as the most active cells of rheumatoid arthritis (RA) and are close to the articular cartilage in a position enabling them to invade the cartilage. Macrophage-like synoviocytes and FLS expression of matrix metalloproteinases (MMPs) and their interaction has aroused great interest. The present article studied the expression of CD147, also called extracellular matrix metalloproteinase inducer, on monocytes/macrophages and FLS from RA patients and its potential role in enhancing MMPs and the invasiveness of synoviocytes. Expression of CD147 on FLS derived from RA patients and from osteoarthritis patients, and expression of CD147 on monocytes/macrophages from rheumatic synovial fluid and healthy peripheral blood were analyzed by flow cytometry. The levels of CD147, MMP-2 and MMP-9 mRNA in FLS were detected by RT-PCR. The role of CD147 in MMP production and the cells' invasiveness in vitro were studied by the co-culture of FLS with the human THP-1 cell line or monocytes/macrophages, by gel zymography and by invasion assay. The results showed that the expression of CD147 was higher on RA FLS than on osteoarthritis FLS and was higher on monocytes/macrophages from rheumatic synovial fluid than on monocytes/macrophages from healthy peripheral blood. RT-PCR showed that the expressions of CD147, MMP-2 and MMP-9 mRNA was higher in RA FLS than in osteoarthritis FLS. A significantly elevated secretion and activation of MMP-2 and MMP-9 were observed in RA FLS co-cultured with differentiated THP-1 cells or RA synovial monocytes/macrophages, compared with those co-cultured with undifferentiated THP-1 cells or healthy control peripheral blood monocytes. Invasion assays showed an increased number of invading cells in the co-cultured RA FLS with differentiated THP-1 cells or RA synovial monocytes/macrophages. CD147 antagonistic peptide inhibited the MMP production and the invasive potential. Our studies demonstrated that the CD147 overexpression on monocytes/macrophages and FLS in RA patients may be responsible for the enhanced MMP secretion and activation and for the invasiveness of synoviocytes. These findings suggest that CD147 may be one of the important factors in progressive joint destruction of RA and that CD147 may be a potential therapeutic target in RA treatment.
doi:10.1186/ar1899
PMCID: PMC1526600  PMID: 16507143
23.  Matrix Metalloproteinase-dependent turnover of cartilage, synovial membrane, and connective tissue is elevated in rats with collagen induced arthritis 
Background
Rheumatoid arthritis is a disease affecting the extracellular matrix of especially synovial joints. The thickness of the synovial membrane increases and surrounding tissue degrades, leading to altered collagen balance in the tissues. In this study, we investigated the altered tissue balance of cartilage, synovial membrane, and connective tissue in collagen induced arthritis (CIA) in rats.
Methods
Six newly developed ELISAs quantifying MMP-derived collagen degradation (C1M, C2M, and C3M) and formation (P1NP, P2NP, and P3NP) was used to detect cartilage turnover in rats with CIA. Moreover, CTX-II was used to detect alternative type II collagen degradation and as control of the model. 10 Lewis rats were injected with porcrine type II collagen twice with a 7 day interval and 10 rats was injected with 0.05 M acetic acid as control. The experiment ran for 26 days.
Results
A significant increase in the degradation of type I, II, and III collagen (C1M, C2M, and C3M, respectively) was detected on day 22 (P = 0.0068, P = 0.0068, P < 0.0001, respectively), whereas no significant difference in formation (P1NP, P2NP, and P3NP) was detected at any time point (P=0.22, P=0.53, P=0.53, respectively). The CTX-II level increased strongly from disease onset and onwards.
Conclusion
A nearly total separation between diseased and control animals was detected with C3M, making it a good diagnostic marker. The balance of type I, II, and III collagen was significantly altered with CIA in rats, with favour of degradation of the investigated collagens. This indicates unbalanced turnover of the surrounding tissues of the synovial joints, leading to increased pain and degeneration of the synovial joints.
doi:10.1186/1479-5876-10-195
PMCID: PMC3551788  PMID: 22992383
Collagen balance; Rheumatoid arthritis; Matrix metalloproteinase; Synovial membrane; Cartilage; Connective tissue
24.  Determination of interstitial collagenase (MMP-1) in patients with rheumatoid arthritis. 
Annals of the Rheumatic Diseases  1995;54(12):970-975.
OBJECTIVES--To investigate whether interstitial collagenase (MMP-1) concentration in synovial fluid can be useful as a marker for disease activity in rheumatoid arthritis (RA), to determine the main route by which collagenase degrades the matrix of articular cartilage, and to investigate if an imbalance between metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMP) is responsible for the activity of MMPs in RA. METHODS--Collagenase concentrations were measured in synovial fluid and paired serum samples using a specific sandwich enzyme linked immunosorbent assay. Collagenase activities were also assayed in synovial fluid samples. Synovial tissues obtained from the same patient were examined by immunohistochemical staining and the numbers of cells expressing collagenase were counted. RESULTS--Collagenase concentrations in synovial fluid did not correlate with C reactive protein and collagenase levels in serum, but did correlate positively with the degree of synovial inflammation, and increased with increasing numbers of cells identified as expressing collagenase in synovial tissue. Collagenase activities did not correlate with TIMP-1 concentrations, but did correlate strongly with the ratios of collagenase concentration to TIMP-1 (r = 0.73). CONCLUSION--The collagenase concentration in synovial fluid cannot be used as a marker for systemic disease activity, but can be used as a marker for the degree of synovial inflammation in the joint from which the sample is aspirated. In advanced RA, most of the collagenase is probably produced in synovial lining cells and released into synovial fluid, where it degrades the matrix of articular cartilage. An imbalance between MMP and TIMP may be of importance in the degradation of extracellular matrix of articular cartilage in RA.
Images
PMCID: PMC1010062  PMID: 8546529
25.  Fibroblast activation protein is expressed by rheumatoid myofibroblast-like synoviocytes 
Fibroblast activation protein (FAP), as described so far, is a type II cell surface serine protease expressed by fibroblastic cells in areas of active tissue remodelling such as tumour stroma or healing wounds. We investigated the expression of FAP by fibroblast-like synoviocytes (FLSs) and compared the synovial expression pattern in rheumatoid arthritis (RA) and osteoarthritis (OA) patients. Synovial tissue from diseased joints of 20 patients, 10 patients with refractory RA and 10 patients with end-stage OA, was collected during routine surgery. As a result, FLSs from intensively inflamed synovial tissues of refractory RA expressed FAP at high density. Moreover, FAP expression was co-localised with matrix metalloproteinases (MMP-1 and MMP-13) and CD44 splice variants v3 and v7/8 known to play a major role in the concert of extracellular matrix degradation. The pattern of signals appeared to constitute a characteristic feature of FLSs involved in rheumatoid arthritic joint-destructive processes. These FAP-expressing FLSs with a phenotype of smooth muscle actin-positive myofibroblasts were located in the lining layer of the synovium and differ distinctly from Thy-1-expressing and non-proliferating fibroblasts of the articular matrix. The intensity of FAP-specific staining in synovial tissue from patients with RA was found to be different when compared with end-stage OA. Because expression of FAP by RA FLSs has not been described before, the findings of this study highlight a novel element in cartilage and bone destruction of arthritic joints. Moreover, the specific expression pattern qualifies FAP as a therapeutic target for inhibiting the destructive potential of fibroblast-like synovial cells.
doi:10.1186/ar2080
PMCID: PMC1794515  PMID: 17105646

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