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Introduction

Adrenomedullin is a potent vasodilatory and hypotensive peptide as well as an endogenous immunomodulatory factor with predominantly anti-inflammatory effects. The purpose of the present study was to evaluate the therapeutic effects of adrenomedullin in rabbits with antigen-induced arthritis, an experimental model of rheumatoid arthritis.

Methods

Following the induction of arthritis in both knee joints by ovalbumin injection into the joint spaces of pre-immunized rabbits, increasing daily doses of adrenomedullin were injected into the knee joint spaces or saline was injected into the contralateral knee joint spaces as the control. For time-course experiments, adrenomedullin and saline were injected into the knee joint spaces daily for 7 days and 20 days. The degree of joint swelling and the histological change in the knee joints injected with adrenomedullin were compared with the control knee joints. Histological evaluation of the infrapatellar fat pads and synovial tissue was performed. TNFα, IL-6, vascular endothelial growth factor and transforming growth factor-beta mRNA levels in the synovial tissue were measured using real-time quantitative PCR.

Results

Daily injections of adrenomedullin into the knee joint spaces of rabbits with antigen-induced arthritis decreased joint swelling. Histological examination revealed that adrenomedullin reduced edematous changes and the infiltration of inflammatory cells in the synovial tissues. Analysis of mRNA levels showed that adrenomedullin significantly reduced TNFα mRNA expression by 21% to 49% in a dose-dependent manner, and dose-dependently increased IL-6 mRNA expression by 45% to 121%.

Conclusions

These results suggest that daily injections of adrenomedullin into the knee joint spaces of rabbits with antigen-induced arthritis ameliorated the inflammatory response in arthritic joints. Adrenomedullin may thus be useful as a treatment for rheumatoid arthritis; however, the effect of adrenomedullin on IL-6 production in the synovial tissue may be an undesirable adverse effect in rheumatoid arthritis therapy.

Rheumatoid arthritis (RA) is recognized to be an autoimmune disease that causes preclinical systemic abnormalities and eventually leads to synovial inflammation and destruction of the joint architecture. Recently identified genetic risk factors and novel insights from animal models of spontaneous arthritis have lent support to the concept that thymic selection of an autoreactive T-cell repertoire is an important risk factor for this disease. With advancing age, defects in the homeostatic control of the T-cell pool and in the setting of signaling thresholds lead to the accumulation of pro-inflammatory T-effector cell populations and loss of tolerance to neo-antigens, such as citrullinated peptides. As the breakdown of tolerance to modified self-antigens can precede synovitis by decades, repair of homeostatic defects may open a unique window of opportunity for preventive interventions in RA. The end result of RA, destruction of cartilage and bone, appears to be driven by cytokine- and cell contact-induced activation of synoviocytes and monocytic cells, some of which differentiate into tissue-destructive osteoclasts. Targeting mediators involved in this process has greatly improved the management of this chronic inflammatory syndrome.

OBJECTIVE—To investigate the development of chronic joint symptoms in patients presenting with acute oligoarthritis including knee joint synovitis with effusion and explore whether prognostic information can be derived from initial synovial fluid concentrations of aggrecan and cartilage oligomeric matrix protein (COMP) for development of chronic joint symptoms.
METHODS—Retrospective follow up of 25 patients identified in a bank of knee joint synovial fluids collected consecutively from patients presenting with knee joint synovitis and symptoms from at most three additional joints and in whom no diagnosis could be established at presentation.
RESULTS—The 10 patients who developed chronic joint symptoms were characterised by lower knee joint synovial fluid concentrations of aggrecan as well as lower aggrecan/COMP ratios (p<0.001) than the 15 patients who had a transient arthritis. No other clinical or laboratory differences between the groups were apparent at the time of presentation.
CONCLUSIONS—The synovial fluid content of aggrecan is a potential tool in acute arthritis for distinguishing patients with a benign disease course from those who will develop a chronic joint disorder.



Introduction

Osteoarthritis (OA) is a degenerative disease characterized by cartilage breakdown in the synovial joints. The presence of low-grade inflammation in OA joints is receiving increasing attention, with synovitis shown to be present even in the early stages of the disease. How the synovial inflammation arises is unclear, but proteins in the synovial fluid of affected joints could conceivably contribute. We therefore surveyed the proteins present in OA synovial fluid and assessed their immunostimulatory properties.

Methods

We used mass spectrometry to survey the proteins present in the synovial fluid of patients with knee OA. We used a multiplex bead-based immunoassay to measure levels of inflammatory cytokines in serum and synovial fluid from patients with knee OA and from patients with rheumatoid arthritis (RA), as well as in sera from healthy individuals. Significant differences in cytokine levels between groups were determined by significance analysis of microarrays, and relations were determined by unsupervised hierarchic clustering. To assess the immunostimulatory properties of a subset of the identified proteins, we tested the proteins' ability to induce the production of inflammatory cytokines by macrophages. For proteins found to be stimulatory, the macrophage stimulation assays were repeated by using Toll-like receptor 4 (TLR4)-deficient macrophages.

Results

We identified 108 proteins in OA synovial fluid, including plasma proteins, serine protease inhibitors, proteins indicative of cartilage turnover, and proteins involved in inflammation and immunity. Multiplex cytokine analysis revealed that levels of several inflammatory cytokines were significantly higher in OA sera than in normal sera, and levels of inflammatory cytokines in synovial fluid and serum were, as expected, higher in RA samples than in OA samples. As much as 36% of the proteins identified in OA synovial fluid were plasma proteins. Testing a subset of these plasma proteins in macrophage stimulation assays, we found that Gc-globulin, α1-microglobulin, and α2-macroglobulin can signal via TLR4 to induce macrophage production of inflammatory cytokines implicated in OA.

Conclusions

Our findings suggest that plasma proteins present in OA synovial fluid, whether through exudation from plasma or production by synovial tissues, could contribute to low-grade inflammation in OA by functioning as so-called damage-associated molecular patterns in the synovial joint.

Mediators of acute immunologic injury have been studied in vivo by producing arthritis in rabbit knee joints. A reversed passive Arthus lesion was produced by injecting antibody into the joint space and antigen intravenously. Injury was assessed by measuring leakage of serum proteins and circulating radiolabeled proteins into the joint space and by the accumulation of neutrophils in the joint fluid. Inflammatory exudate was recovered for study by a standardized irrigation technique.

Maximal vascular permeability developed 2 hr after injection as neutrophils accumulated about immune complexes in venule walls to produce structural injury. After 5 hr the number of neutrophils in the joint space rose rapidly, followed by a second rise in permeability at 8 hr. Neutrophil depletion abolished both peaks of permeability. It was then possible to reconstitute the synovial lesion in neutrophil-depleted rabbits by intra-articular injection of purified suspensions of neutrophils.

A requirement for complement was demonstrated in development of the lesion. Rabbits genetically deficient in C6 showed delay in vascular permeability, appearance of neutrophils, and histologic lesions. The delay was longer in normal rabbits depleted of C3. In C6-deficient rabbits depleted of C3, still further reduction in injury occurred.

Evidence was obtained as well for a chemotactic attraction of neutrophils in vivo. Antigen-antibody-complement complexes in the walls of blood vessels attracted neutrophils placed in the joint space of neutrophil-depleted rabbits. Omission of either antigen or antibody from this replacement reaction prevented the migration of neutrophils.

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OBJECTIVES—By repeated magnetic resonance imaging (MRI) to study synovial membrane regeneration and recurrence of synovitis after arthroscopic knee joint synovectomy in patients with rheumatoid arthritis (RA) and other (non-RA) causes of persistent knee joint synovitis.
METHODS—Contrast enhanced MRI was performed in 15 knees (nine RA, six non-RA) before and one day, seven days, two months, and 12 months after arthroscopic synovectomy. Synovial membrane volumes, joint effusion volumes, and cartilage and bone destruction were assessed on each MRI set. Baseline microscopic and macroscopic assessments of synovitis and baseline and follow up standard clinical and biochemical examinations were available.
RESULTS—Synovial membrane and joint fluid volumes were significantly reduced two and 12 months after synovectomy. However, MRI signs of recurrent synovitis were already present in most knees at two months. No significant differences between volumes in RA and non-RA knees were seen. Synovial membrane volumes at two months were significantly inversely correlated with the duration of clinical remission, for all knees considered together (Spearman's correlation rs=−0.67; p<0.05), for RA knees (rs=−0.76; p<0.05), and for non-RA knees (rs=−0.83; p<0.05). Baseline volumes were not significantly correlated with clinical outcome. Only three knees (all RA) showed erosive progression. The rate of erosive progression was not correlated with MRI volumes or with clinical or biochemical parameters.
CONCLUSION—The synovial membrane had regenerated two months after arthroscopic knee joint synovectomy and despite significant volume reductions compared with baseline it often showed signs of recurrent synovitis. MRI seems to be valuable as a marker of inflammation, destruction and, perhaps, as a predictor of therapeutic outcome in arthritis.



Surgical synovectomy to remove the inflammatory synovium can temporarily ameliorate rheumatoid inflammation and delay the progress of joint destruction. An efficient medically induced programmed cell death (apoptosis) in the rheumatoid synovium might play a role similar to synovectomy but without surgical tissue damage. Gene transfer of Fas ligand (FasL) has increased the frequency of apoptotic cells in mouse and rabbit arthritic synovium. In this study, we investigated whether repeated FasL gene transfer could remove human inflammatory synovial tissue in situ and function as a molecular synovectomy. Briefly, specimens of human synovium from joint replacement surgeries and synovectomies of rheumatoid arthritis (RA) patients were grafted subcutaneously into male C.B-17 severe combined immunodeficiency (SCID) mice. Injections of a recombinant FasL adenovirus (Ad-FasL) into the grafted synovial tissue at the dosage of 1011 particles per mouse were performed every two weeks. Three days after the fifth virus injection, the mice were euthanized by CO2 inhalation and the human synovial tissues were collected, weighed and further examined. Compared to the control adenovirus-LacZ (Ad-LacZ) and phosphate buffered saline (PBS) injected RA synovium, the Ad-FasL injected RA synovium was dramatically reduced in size and weight (P < 0.005). The number of both synoviocytes & mononuclear cells was significantly reduced. Interestingly, an approximate 15-fold increased frequency of apoptotic cells was observed in RA synovium three days after Ad-FasL injection, compared with control tissues. In summary, our in vivo investigation of gene transfer to human synovium in SCID mice suggests that repeated intra-articular gene transfer of an apoptosis inducer, such as FasL, may function as a 'gene scalpel' for molecular synovectomy to arrest inflammatory synovium at an early stage of RA.

A dose-dependent chronic synovitis was induced in rabbit knees after the intra-articular injection of both Mycoplasma arthritidis and Mycoplasma pulmonis. The inflammation progressed from an initial acute phase at 1 week characterized by edema, infiltration of the synovium with monocytes and heterophils, and desquamation of lining cells, to a more chronic phase at 1 and 3 months, in which villus hyperplasia, lymph "nodules," mononuclear cell infiltration, fibroplasia, and collagen deposition were prominent. With one exception, mycoplasmas could no longer be cultivated from the joints 1 month postinoculation. Both mycoplasma species evoked a humoral antibody response that was more marked in synovial fluids than in peripheral blood. A cell-mediated immune reaction, as evidence by enhanced uptake by [3H]thymidine by sensitized blood, spleen, or node lymphocytes in the presence of homologous antigen, was detected only in rabbits injected with M. pulmonis. Lymphocytes taken from arthritic rabbits were no more cytotoxic toward synovial cells derived from normal or arthritic rabbits than were normal lymphocytes. The models of synovitis described in this study offer a convenient probe for determining the mechanisms of mycoplasma-induced inflammation, since they require only a single injection of the initiating agent and, in addition, utilize an animal host large enough for detailed investigation into the nature of mycoplasma/synovium interactions.

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Morpholino oligonucleotides (MOs) are an effective, gene-specific antisense knockdown technology used in many model systems. Here we describe the application of MOs in zebrafish (Danio rerio) for in vivo functional characterization of gene activity. We summarize our screening experience beginning with gene target selection. We then discuss screening parameter considerations and data and database management. Finally, we emphasize the importance of off-target effect management and thorough downstream phenotypic validation. We discuss current morpholino limitations, including reduced stability when stored in aqueous solution. Advances in MO technology now provide a measure of spatiotemporal control over MO activity, presenting the opportunity for incorporating more finely tuned analyses into MO-based screening. Therefore, with careful management, MOs remain a valuable tool for discovery screening as well as individual gene knockdown analysis.

Considering the relation between synovial inflammation and global disease activity in rheumatoid arthritis (RA) and the distinct but heterogeneous histology of spondyloarthropathy (SpA) synovitis, the present study analyzed whether histopathological features of synovium reflect specific phenotypes and/or global disease activity in SpA. Synovial biopsies obtained from 99 SpA and 86 RA patients with active knee synovitis were analyzed for 15 histological and immunohistochemical markers. Correlations with swollen joint count, serum C-reactive protein concentrations, and erythrocyte sedimentation rate were analyzed using classical and multiparameter statistics. SpA synovitis was characterized by higher vascularity and infiltration with CD163+ macrophages and polymorphonuclear leukocytes (PMNs) and by lower values for lining-layer hyperplasia, lymphoid aggregates, CD1a+ cells, intracellular citrullinated proteins, and MHC–HC gp39 complexes than RA synovitis. Unsupervised clustering of the SpA samples based on synovial features identified two separate clusters that both contained different SpA subtypes but were significantly differentiated by concentration of C-reactive protein and erythrocyte sedimentation rate. Global disease activity in SpA correlated significantly with lining-layer hyperplasia as well as with inflammatory infiltration with macrophages, especially the CD163+ subset, and with PMNs. Accordingly, supervised clustering using these synovial parameters identified a cluster of 20 SpA patients with significantly higher disease activity, and this finding was confirmed in an independent SpA cohort. However, multiparameter models based on synovial histopathology were relatively poor predictors of disease activity in individual patients. In conclusion, these data indicate that inflammatory infiltration of the synovium with CD163+ macrophages and PMNs as well as lining-layer hyperplasia reflect global disease activity in SpA, independently of the SpA subtype. These data support a prominent role for innate immune cells in SpA synovitis and warrant further evaluation of synovial histopathology as a surrogate marker in early-phase therapeutic trials in SpA.

Background: Ultrasonography allows assessment of soft tissue structures and has become a valued tool for diagnosing synovitis.

Objective: To assess the learning curve for ultrasonography in evaluating synovitis of the small joints in rheumatoid arthritis.

Methods: Metacarpophalangeal (MCP), metatarsophalangeal (MTP), and proximal interphalangeal (PIP) joints were evaluated using ultrasonography (Esaote AU 5 Epi, linear probe 10–13 MHz) by four rheumatologists, the first being experienced (senior), the others having no (fellows 1 and 2) or little (fellow 3) experience in ultrasonography. For each fellow, the learning curve was divided into blocks. In each block the fellow examined five consecutive patients with the senior; then, blinded to the senior's results, two further patients alone (seven patients examined per block). For each evaluation, the MCP, PIP, and MTP joints were individually tagged as having synovitis or not. The ultrasonography results were compared between fellow and senior for the two last patients of each block, using proportions of agreement and κ statistics.

Results: 70 patients were evaluated (seven practice patients, followed by nine blocks). For fellows 1 and 2, the proportions of agreement were respectively 42% and 47% (κ = 0 and 0) at the first evaluation, and rose progressively to 82% and 82% (κ = 0.63 and 0.62) at the ninth evaluation. For fellow 3, initially good results were followed by decreased accuracy.

Conclusions: Detecting synovitis of the MCP, PIP, and MTP joints using ultrasonography can be done accurately by rheumatologists initially not experienced in this technique. At least 70 examinations were necessary to develop competence.

Synovitis secondary to penetrating plant thorn injuries is not frequently reported. Historically, it is considered aseptic and treated with removal of the intraarticular foreign body and affected synovial lining. We report a 57-year-old healthy man who was admitted 2 weeks after being injured by a rose (Rosacea) thorn with subacute and mild synovitis with effusion of his right knee. No intraarticular foreign body was retained. Pantoea agglomerans was identified in the synovial fluid. Contrary to former teaching, effusions from joints violated by thorns should not be presumed sterile. Bacterial growth is reported infrequently, but when reported, Pantoea agglomerans is the most common organism found. We recommend removal of foreign bodies if present, arthroscopic total synovectomy, and beginning empiric antibiotic treatment with coverage against Gram-negative enteric pathogens in all cases of thorn synovitis until the results of culture specimens are known. Improved physician awareness can result in more rapid diagnosis and improved clinical outcome in affected individuals.

The merger of the Pediatric Oncology Group, Children's Cancer Group, the Intergroup Rhabdomyosarcoma Study Group, and the National Wilms Tumor Study Group in 2000 offered the newly formed Children's Oncology Group (COG), an opportunity to study rare cancers that had not been the subject of organized evaluation within the context of a cooperative group. In 2002, the COG formed the rare tumor committee which is comprised of four subcommittees. This article details the experience of the infrequent tumor subcommittee for the period of 2002 to 2007. During the initial implementation of this strategy, we have observed low rates of registration within the COG registry and low levels of participation in open banking, biology, and first-line therapeutic studies. This initial experience has allowed us to develop alternative strategies to increase registration rates and clinical trial enrollments. It is hoped that these new plans will allow us to increase our ability to better understand the biology and improve the treatment outcome of young patients with infrequent cancers. Furthermore, our initial experience has demonstrated to us the potential power of expanded cooperation and collaboration at a global level.

Metastasis suppressor proteins regulate multiple steps in the metastatic cascade, including cancer cell invasion, survival in the vascular and lymphatic circulation, and colonization of distant organ sites. Understanding the biology of metastasis suppressors provides valuable mechanistic insights that may translate to therapeutic opportunities. Several reports have explored novel strategies for restoring metastasis suppressor function, including gene transfer, induction of previously suppressed gene expression and exogenous administration of gene product. Pathways activated downstream of metastasis suppressor loss can also be targeted. Although none of these strategies are yet in routine clinical use, several are being tested preclinically and in clinical trials.

A method for measuring synovial blood flow changes using the laser Doppler technique is described. Mean blood flow and mean pulse amplitude decreased by 50-70% in relation to the reference level when the intra-articular hydrostatic pressure in effusive knee joints of patients with rheumatoid arthritis was increased. As an increase of intra-articular pressure of as little as 20 mmHg decreased synovial blood flow significantly it is suggested that hypoxia may occur in vivo during joint use in the presence of an effusion. This may be of aetiopathogenetic importance for tissue destruction and the persistence of chronic synovitis.

Currently, treatment for rheumatoid arthritis and other inflammatory arthropathies is often ineffective in ameliorating the progression of the disease, particularly the invasive destruction of cartilage and bone by rheumatoid synovium. Multiple aspects of this inflammatory process are mediated by the synovial lining cells (synoviocytes). Genetic modification of these cells in vivo represents a potential method for the treatment of these conditions. In this report, we describe a novel technique for the genetic transduction of synovial lining cells in vivo using recombinant adenoviral vectors and intraarticular injection techniques. Purified high titer suspensions of a recombinant adenoviral vector containing the gene for Escherichia coli beta-galactosidase (AdCMVlacZ) were directly injected into the hind knees of New Zealand white rabbits. Synovial tissues were then examined for transgenic lacZ expression using a combination of in situ staining for beta-galactosidase activity, immunohistochemical staining, and transmission electron microscopy. High efficiency gene transfer and lacZ expression was observed in both type A and type B synoviocytes throughout the articular and periarticular synovium of the rabbit knee, with continued expression of transgenic lacZ detected for > or = 8 wk after infection.

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Computational mechanics has been advanced in every area of orthopedic biomechanics. The objective of this paper is to provide a general review of the computational models used in the analysis of the mechanical function of the knee joint in different loading and pathological conditions. Major review articles published in related areas are summarized first. The constitutive models for soft tissues of the knee are briefly discussed to facilitate understanding the joint modeling. A detailed review of the tibiofemoral joint models is presented thereafter. The geometry reconstruction procedures as well as some critical issues in finite element modeling are also discussed. Computational modeling can be a reliable and effective method for the study of mechanical behavior of the knee joint, if the model is constructed correctly. Single-phase material models have been used to predict the instantaneous load response for the healthy knees and repaired joints, such as total and partial meniscectomies, ACL and PCL reconstructions, and joint replacements. Recently, poromechanical models accounting for fluid pressurization in soft tissues have been proposed to study the viscoelastic response of the healthy and impaired knee joints. While the constitutive modeling has been considerably advanced at the tissue level, many challenges still exist in applying a good material model to three-dimensional joint simulations. A complete model validation at the joint level seems impossible presently, because only simple data can be obtained experimentally. Therefore, model validation may be concentrated on the constitutive laws using multiple mechanical tests of the tissues. Extensive model verifications at the joint level are still crucial for the accuracy of the modeling.

Introduction

Synovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome is a rare disorder. The etiology remains unknown and the treatment is still empirical. Synovitis is one of the major manifestations, but information on histopathological features is still lacking. In this case, we investigated the histopathological features of SAPHO syndrome synovitis.

Case presentation

We present the case of a 53-year-old Japanese woman with SAPHO syndrome accompanied by marked knee synovitis and palmoplantar pustulosis. We found abundant sterile joint fluid in the right knee, and a blood test showed abnormally high values of C-reactive protein (17.26 mg/dl) and matrix metalloproteinase-3 (800 ng/ml). Arthroscopic surgery revealed marked proliferation of villous synovial tissues similar to rheumatoid arthritis and standard microscopic findings were also similar to rheumatoid arthritis. Furthermore, for the first time, we demonstrated by immunohistochemistry the expression of tumor necrosis factor-alpha (TNF-α) converting enzyme, TNF-α and matrix metalloproteinase-3 in the proliferated synovial lining cells. After arthroscopic synovectomy, her knee symptoms immediately diminished and laboratory data (matrix metalloproteinase-3 and C-reactive protein) normalized within 2 weeks of surgery.

Conclusion

We demonstrate the expression of TNF-α converting enzyme, TNF-α and matrix metalloproteinase-3 in SAPHO syndrome synovitis for the first time and also show, both macro- and microscopically, the similarity between SAPHO syndrome and rheumatoid arthritis synovitis. These new findings support the recently reported successful treatment of SAPHO syndrome with antirheumatic drugs, especially with anti-TNF-α agents.