Crucial role of macrophages in matrix metalloproteinase-mediated cartilage destruction during experimental osteoarthritis: involvement of matrix metalloproteinase 3.

Objective: To explore the involvement of synovial macrophages in early cartilage damage in osteoarthritis (OA), and to identify the role of matrix metalloproteinase 3 (MMP-3) in the pathology of early and late OA.

Methods: The role of synovial macrophages in MMP-mediated damage in OA was studied by depleting synovial macrophages prior to elicitation of a collagenase-induced instability model of OA. The expression of MMP in synovium and cartilage was monitored using TaqMan analysis.

NADPH-oxidase-driven oxygen radical production determines chondrocyte death and partly regulates metalloproteinase-mediated cartilage matrix degradation during interferon-gamma-stimulated immune complex arthritis.

In previous studies we have found that FcgammaRI determines chondrocyte death and matrix metalloproteinase (MMP)-mediated cartilage destruction during IFN-gamma-regulated immune complex arthritis (ICA). Binding of immune complexes (ICs) to FcgammaRI leads to the prominent production of oxygen radicals. In the present study we investigated the contribution of NADPH-oxidase-driven oxygen radicals to cartilage destruction by using p47phox-/- mice lacking a functional NADPH oxidase complex.

Joint inflammation and chondrocyte death become independent of Fcgamma receptor type III by local overexpression of interferon-gamma during immune complex-mediated arthritis.

Objective: It has previously been shown that the onset and the degree of joint inflammation during immune complex (IC)-mediated arthritis depend on Fcgamma receptor type III (FcgammaRIII). Local adenoviral overexpression of interferon-gamma (IFNgamma) in the knee joint prior to onset of IC-mediated arthritis aggravated severe cartilage destruction. In FcgammaRI(-/-) mice, however, chondrocyte death was not enhanced by IFNgamma, whereas matrix metalloproteinase (MMP)-mediated aggrecan breakdown was markedly elevated, suggesting a role for the activating FcgammaRIII in the latter process.

Local IL-13 gene transfer prior to immune-complex arthritis inhibits chondrocyte death and matrix-metalloproteinase-mediated cartilage matrix degradation despite enhanced joint inflammation.

During immune-complex-mediated arthritis (ICA), severe cartilage destruction is mediated by Fcgamma receptors (FcgammaRs) (mainly FcgammaRI), cytokines (e.g. IL-1), and enzymes (matrix metalloproteinases (MMPs)).

Synovial lining macrophages mediate osteophyte formation during experimental osteoarthritis.

Objective: In human osteoarthritis (OA), various forms of pathology are observed. Besides cartilage damage and fibrosis, neogenesis of bone, osteophyte formation, also occurs. Osteophytes are thought to limit joint movement and cause pain.

Liposomal targeting of glucocorticoids to synovial lining cells strongly increases therapeutic benefit in collagen type II arthritis.

Objective: To investigate the effect of a single intravenous treatment with glucocorticoids (GC) encapsulated in long-circulating PEG-liposomes on both joint inflammation and cartilage destruction and to investigate the phenomenon of selective homing of these liposomes in the inflamed synovium.

Methods: Mice with collagen type II-induced arthritis (CIA) were intravenously treated with liposomal and free prednisolone phosphate (PLP) a few days after the first signs of the disease. Joint inflammation was scored during 1 week after treatment, after which sections of the knee joints were prepared for assessment of cartilage damage.

Crucial role of synovial lining macrophages in the promotion of transforming growth factor beta-mediated osteophyte formation.

Objective: To investigate in vivo and in vitro whether macrophages have an intermediate role in transforming growth factor beta (TGFbeta)-induced osteophyte formation.

Methods: In vivo, synovial lining macrophages were selectively depleted by injection of clodronate-laden liposomes 7 days prior to injection of 20 ng or 200 ng of TGFbeta into murine knee joints 3 times, on alternate days. Total knee joint sections were obtained on day 7 after the last injection and stained with Safranin O.

The inhibitory receptor FcgammaRII reduces joint inflammation and destruction in experimental immune complex-mediated arthritides not only by inhibition of FcgammaRI/III but also by efficient clearance and endocytosis of immune complexes.

Studies of FcgammaRII-/- mice identified the inhibitory function of this receptor in joint inflammation and cartilage destruction induced with immune complexes (ICs). To extend our insight in the role of FcgammaRII in arthritis, we explored the role of FcgammaRII in the absence of activating receptors I and III using FcgammaRI/III-/- as well as FcgammaRI/II/III-/- mice. When antigen-induced arthritis (AIA) was elicited, which is a mixture of T cell and IC-driven inflammation, arthritis was almost absent at day 7 in FcgammaRI/III-/- mice.

FcgammaRI up-regulation induced by local adenoviral-mediated interferon-gamma production aggravates chondrocyte death during immune complex-mediated arthritis.

Using various FcgammaR-deficient mice, we have obtained suggestive evidence that FcgammaRI on macrophages is responsible for severe cartilage destruction during arthritis mediated by immune complexes (ICs). This role of FcgammaRI is pronounced in the presence of activated Th1 cells and a likely Th1 cell-derived cytokine mediating up-regulation of FcgammaRI expression is interferon (IFN)-gamma. We now investigated whether local overexpression of IFN-gamma using an adenoviral vector is able to elevate cartilage destruction during experimental immune complex-mediated arthritis (ICA) and to what extent this process is FcgammaRI-mediated.

Skewed balance in basal expression and regulation of activating v inhibitory Fcgamma receptors in macrophages of collagen induced arthritis sensitive mice.

Background: Recently, it has been found that collagen type II arthritis susceptible mouse strains are hyperreactive to immune complexes (ICs), locally deposited into their knee joints.

Objective: To investigate whether this strain specific knee joint hyperreactivity is related to a disturbed regulation of activatory and inhibitory FcgammaR on their macrophages before and after stimulation with ICs.

Methods: Macrophages from collagen induced arthritis susceptible strains (DBA/1 and B10.

Increased expression of Fcgamma receptors II and III on macrophages of rheumatoid arthritis patients results in higher production of tumor necrosis factor alpha and matrix metalloproteinase.

Objective: To evaluate Fcgamma receptor (FcgammaR) expression on synovial macrophages from rheumatoid arthritis (RA) patients and to determine whether this expression correlates with the production of the proinflammatory cytokines tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), IL-12, and matrix metalloproteinase 1 (MMP-1). We also sought to determine whether mature macrophages from RA patients express aberrant levels of FcgammaRI, FcgammaRII, and FcgammaRIII, and to determine the production of inflammatory mediators after immune complex (IC) stimulation.

Methods: Immunohistochemistry was performed on cryostat sections of synovial biopsy specimens obtained from 27 RA patients and 5 controls.

Coordinate expression of activating Fc gamma receptors I and III and inhibiting Fc gamma receptor type II in the determination of joint inflammation and cartilage destruction during immune complex-mediated arthritis.

Objective: To study the role of the activating Fc gamma receptor types I and III (Fc gamma RI and Fc gamma RIII, respectively) and the inhibiting Fc gamma receptor II (Fc gamma RII) in inflammation and in various aspects of cartilage destruction during arthritis that is solely induced by immune complexes.

Methods: Immune complex-mediated arthritis (ICA) was passively induced by lysozyme-antilysozyme complexes in Fc gamma RI-, Fc gamma RIII-, and Fc gamma RII-knockout mice and their wild-type controls. Total knee joints were isolated to study inflammation and cartilage destruction (loss of proteoglycans [PGs], chondrocyte death, matrix metalloproteinase [MMP]-mediated neoepitope [VDIPEN] expression, and erosion).

Local overexpression of adeno-viral IL-4 protects cartilage from metallo proteinase-induced destruction during immune complex-mediated arthritis by preventing activation of pro-MMPs.

Objective: To determine whether IL-4 protects against metalloproteinase-induced cartilage destruction during immune complex mediated arthritis and to elucidate its mechanism.

Methods: Experimental immune complex arthritis (ICA) was raised by injecting lysozyme into the knee joints of mice which previously were given anti-lysozyme antibodies. Three days before ICA induction, mice were injected into the right knee joint with either IL-4 expressing or empty control recombinant human type 5 adenovirus.

Role of activatory Fc gamma RI and Fc gamma RIII and inhibitory Fc gamma RII in inflammation and cartilage destruction during experimental antigen-induced arthritis.

IgG-containing immune complexes, which are found in most RA joints, communicate with hematopoietic cells using three classes of Fc receptors(Fc gamma RI, -II, -III). In a previous study we found that if a chronic T-cell-mediated antigen-induced arthritis (AIA) was elicited in knee joints of FcR gamma-chain-deficient mice that lack functional Fc gamma RI and Fc gamma RIII, joint inflammation was comparable but severe cartilage destruction was absent. We now examined the individual role of the stimulatory Fc gamma RI and Fc gamma RIII and inhibitory Fc gamma RII in inflammation and functional cartilage damage in knee joints with AIA using Fc gamma RI-, Fc gamma RII-, and Fc gamma RIII-deficient mice.

Uptake of apoptotic leukocytes by synovial lining macrophages inhibits immune complex-mediated arthritis.

Previously we have shown that synovial lining macrophages (SLMs) determine the onset of experimental immune complex-mediated arthritis (ICA). During joint inflammation, many leukocytes undergo apoptosis, and removal of leukocytes by SLMs may regulate resolution of inflammation. In this study we investigated binding and uptake of apoptotic leukocytes by SLMs and its impact on the onset of murine experimental arthritis.

Fc gamma R expression on macrophages is related to severity and chronicity of synovial inflammation and cartilage destruction during experimental immune-complex-mediated arthritis (ICA).

STATEMENT OF FINDINGS: We investigated the role of Fc gamma receptors (Fc gamma Rs) on synovial macrophages in immune-complex-mediated arthritis (ICA). ICA elicited in knee joints of C57BL/6 mice caused a short-lasting, florid inflammation and reversible loss of proteoglycans (PGs), moderate chondrocyte death, and minor erosion of the cartilage. In contrast, when ICA was induced in knee joints of Fc receptor (FcR) gamma-chain(-/-) C57BL/6 mice, which lack functional Fc gamma RI and RIII, inflammation and cartilage destruction were prevented.

Role of Fc receptor gamma chain in inflammation and cartilage damage during experimental antigen-induced arthritis.

Objective: To study the role of Fc receptor (FcR) gamma chain in inflammation and cartilage destruction during antigen-induced arthritis (AIA).

Methods: FcR gamma-/- mice and controls were immunized with methylated bovine serum albumin (mBSA) in Freund's complete adjuvant, followed by induction of arthritis by local injection of mBSA into the right knee joint. Joint inflammation was studied by 99mTc uptake and by histology.

Immune complexes, but not streptococcal cell walls or zymosan, cause chronic arthritis in mouse strains susceptible for collagen type II auto-immune arthritis.

In this study we investigated mechanisms involved in the chronic character of experimental collagen type II induced arthritis (CIA). We compared the knee joints of mouse strains which are prone to develop this autoimmune disease (DBA/1,B10RIII) with other nonsusceptible mouse strains (C57Bl/6,BALB/c) in their reaction to different stimuli: immune complexes (IC), zymosan and streptococcal cell walls (SCW). Inflammation was evaluated by(99m)Tc uptake measurements and in haematoxylin- and eosin-stained knee-joint sections.

Active matrix metalloproteinases are present in cartilage during immune complex-mediated arthritis: a pivotal role for stromelysin-1 in cartilage destruction.

The involvement of immune complexes during experimental arthritis in induction of metalloproteinases (MMP)-induced neoepitopes in aggrecan in cartilage, as well as the role of stromelysin-1 (SLN-1) in the induction of this neoepitope, was investigated. Passive immune complex arthritis was induced, and generation of the MMP-specific cleavage product (VDIPEN) was studied by immunolocalization. The role of SLN-1 was studied with use of SLN-1-deficient (SLN-1KO) mice.

Cleavage of aggrecan at the Asn341-Phe342 site coincides with the initiation of collagen damage in murine antigen-induced arthritis: a pivotal role for stromelysin 1 in matrix metalloproteinase activity.

Objective: The destruction of articular cartilage during arthritis is due to proteolytic cleavage of the extracellular matrix components. This study investigates the kinetic involvement of metalloproteinases (MMPs) in the degradation of the 2 major cartilage components, aggrecan and type II collagen, during murine antigen-induced arthritis (AIA). In addition, the role of stromelysin 1 (SLN-1) induction of MMP-induced neoepitopes was studied.

Kinetics of aggrecanase- and metalloproteinase-induced neoepitopes in various stages of cartilage destruction in murine arthritis.

Objective: Two major cleavage sites, one mediated by metalloproteinases (MMPs) and the other by an as-yet unidentified enzyme termed aggrecanase, have been observed in aggrecan. To learn more about the relative contribution of these enzymes during cartilage degradation, this study assessed the occurrence of both specific neoepitopes in cartilage during murine arthritis and examined the correlation between neoepitope formation and different aspects of cartilage damage.

Methods: Reversible cartilage damage was induced in mice in the zymosan-induced arthritis (ZIA) model, partly irreversible cartilage damage in the antigen-induced arthritis (AIA) model, and irreversible, destructive cartilage damage in the collagen-induced arthritis (CIA) model.

Increased vulnerability of postarthritic cartilage to a second arthritic insult: accelerated MMP activity in a flare up of arthritis.

Objective: Murine antigen induced arthritis (AIA) is a chronic, smouldering inflammation. Flares of arthritis can be induced by antigen rechallenge or exposure to inflammatory mediators like interleukin 1 (IL1). These flares are characterised by a fast and marked proteoglycan (PG) depletion if compared with the initial arthritis.

Local removal of phagocytic synovial lining cells by clodronate-liposomes decreases cartilage destruction during collagen type II arthritis.

Objective: To investigate whether local removal of phagocytic synovial lining cells (SLCs) from the knee joint before onset of collagen type II arthritis has an effect on development of cartilage destruction.

Methods: Phagocytic SLCs were selectively depleted by a single injection of clodronate laden liposomes in the knee joint seven days before induction of collagen type II arthritis (CIA). Clodronate laden liposomes were given in one knee joint either alone or in combination with a short-term oral treatment of dexamethasone.

Phagocytic synovial lining cells regulate acute and chronic joint inflammation after antigenic exacerbation of smouldering experimental murine arthritis.

Objective: To investigate the in vivo role of phagocytic synovial lining cells in inflammation after exacerbation of smouldering murine antigen induced arthritis.

Methods: Phagocytic synovial lining cells were selectively depleted, by intraarticular injection of clodronate laden liposomes, 2 weeks after induction of modified bovine serum albumin induced arthritis. Exacerbation of arthritis was induced at Week 3, intravenously or locally into the knee joint.

Monocytes/macrophages rather than PMN are involved in early cartilage degradation in cationic immune complex arthritis in mice.

We investigated the involvement of polymorphonuclear granulocytes (PMN) and monocytes in cartilage degradation in immune complex-mediated arthritis (ICA). ICA induced with lysozyme-antilysozyme in the murine knee joint is characterized by a major influx of PMNs followed by monocytes and marked cartilage proteoglycan (PG) depletion develops within 2 days. Around 60% of 35S-prelabeled PG is lost at day 2.