Identification of the major fibroblast growth factors released spontaneously in inflammatory arthritis as platelet derived growth factor and tumour necrosis factor-alpha

Real-life data of etanercept efficacy and safety in juvenile idiopathic arthritis: a 24-month retrospective study at a single center

OBJECTIVE

The aim of this study was to assess the efficacy and safety of etanercept (ETA) use in juvenile idiopathic arthritis (JIA).

METHODS

The 24-month data of patients with JIA on etanercept in a single center were evaluated retrospectively. Response to treatment was assessed according to 10-joint Juvenile Arthritis Disease Activity Score (JADAS10), and JIA-American College of Rheumatology (ACR) improvement criteria. Safety assessments were based on adverse event (AE) reports.

RESULTS

The study included 152 patients with JIA. The mean age at diagnosis of JIA was 8.5 ± 4.4 years, and treatment with ETA started at a mean age of 11.1 ± 4.4 years. The mean duration of ETA use was 16 ± 11.1 months. The mean JADAS10 score at baseline was 18.5 ± 5.9. By the third month, it had reduced to 8.6 ± 6.6 and by the sixth month to 5.7 ± 6. By the twelfth month, the JADAS10 score was 4.9 ± 6.7, and by the twenty-fourth month, it had worsened to 7.3 ± 7.8. ACR50 response was achieved in 79.6% of patients at 3 months, 67.1% at 6 months, 79.3% at twelfth months, 70.7% at the twenty-fourth month. During ETA treatment, 10 patients required hospitalization for serious infections.

CONCLUSION

Etanercept is a safe and effective option for patients with JIA. However, variations in response between JIA subtypes highlight the need for individualized treatment strategies.

A large-scale Boolean model of the rheumatoid arthritis fibroblast-like synoviocytes predicts drug synergies in the arthritic joint

Rheumatoid arthritis (RA) is a complex autoimmune disease with an unknown aetiology. However, rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) play a significant role in initiating and perpetuating destructive joint inflammation by expressing immuno-modulating cytokines, adhesion molecules, and matrix remodelling enzymes. In addition, RA-FLS are primary drivers of inflammation, displaying high proliferative rates and an apoptosis-resistant phenotype. Thus, RA-FLS-directed therapies could become a complementary approach to immune-directed therapies by predicting the optimal conditions that would favour RA-FLS apoptosis, limit inflammation, slow the proliferation rate and minimise bone erosion and cartilage destruction. In this paper, we present a large-scale Boolean model for RA-FLS that consists of five submodels focusing on apoptosis, cell proliferation, matrix degradation, bone erosion and inflammation. The five-phenotype-specific submodels can be simulated independently or as a global model. In silico simulations and perturbations reproduced the expected biological behaviour of the system under defined initial conditions and input values. The model was then used to mimic the effect of mono or combined therapeutic treatments and predict novel targets and drug candidates through drug repurposing analysis.

Transformation of fibroblast-like synoviocytes in rheumatoid arthritis; from a friend to foe

Swelling and the progressive destruction of articular cartilage are major characteristics of rheumatoid arthritis (RA), a systemic autoimmune disease that directly affects the synovial joints and often causes severe disability in the affected positions. Recent studies have shown that type B synoviocytes, which are also called fibroblast-like synoviocytes (FLSs), as the most commonly and chiefly resident cells, play a crucial role in early-onset and disease progression by producing various mediators. During the pathogenesis of RA, the FLSs' phenotype is altered, and represent invasive behavior similar to that observed in tumor conditions. Modified and stressful microenvironment by FLSs leads to the recruitment of other immune cells and, eventually, pannus formation. The origins of this cancerous phenotype stem fundamentally from the significant metabolic changes in glucose, lipids, and oxygen metabolism pathways. Moreover, the genetic abnormalities and epigenetic alterations have recently been implicated in cancer-like behaviors of RA FLSs. In this review, we will focus on the mechanisms underlying the transformation of FLSs to a cancer-like phenotype during RA. A comprehensive understanding of these mechanisms may lead to devising more effective and targeted treatment strategies.

An overview of carbonic anhydrases and membrane channels of synoviocytes in inflamed joints

The highly aggressive fibroblast-like synoviocytes (FLSs) are inflammatory mediators involved in synovial joint destruction. Membrane channels and transporters are essential components of the cell migration apparatus and are involved in various cellular functions. Although evidence is emerging that cell migration is a physiological/pathological process, the mechanism of highly dynamic synoviocytes linked to the membrane channels and carbonic anhydrases (CAs) in inflamed joints is only partially understood. In this review, topics covered will give a brief overview of CAs and the membrane channels of synoviocytes. We have also systematically focused on the role of FLS channels and transporters under various conditions, including rheumatoid arthritis (RA), to understand the pathophysiology of the migration of synoviocytes as inflammatory mediators in joints.

Interactions between cadherin-11 and platelet-derived growth factor receptor-alpha signaling link cell adhesion and proliferation

Cadherins are homophilic cell-to-cell adhesion molecules that help cells respond to environmental changes. Newly formed cadherin junctions are associated with increased cell phosphorylation, but the pathways driving this signaling response are largely unknown. Since cadherins have no intrinsic signaling activity, this phosphorylation must occur through interactions with other signaling molecules. We previously reported that cadherin-11 engagement activates joint synovial fibroblasts, promoting inflammatory and degradative pathways important in rheumatoid arthritis (RA) pathogenesis. Our objective in this study was to discover interacting partners that mediate cadherin-11 signaling. Protein array screening showed that cadherin-11 extracellular binding domains linked to an Fc domain (cad11Fc) induced platelet-derived growth factor (PDGFR)-α phosphorylation in synovial fibroblasts and glioblastoma cells. PDGFRs are growth factor receptor tyrosine kinases that promote cell proliferation, survival, and migration in mesodermally derived cells. Increased PDGFR activity is implicated in RA pathology and associates with poor prognosis in several cancers, including sarcoma and glioblastoma. PDGFRα activation by cadherin-11 signaling promoted fibroblast proliferation, a signaling pathway independent from cadherin-11-stimulated IL-6 or matrix metalloproteinase (MMP)-3 release. PDGFRα phosphorylation mediated most of the cad11Fc-induced phosphatidyl-3-kinase (PI3K)/Akt activation, but only part of the mitogen-activated protein kinase (MAPK) response. PDGFRα-dependent signaling did not require cell cadherin-11 expression. Rather, cad11Fc immunoprecipitated PDGFRα, indicating a direct interaction between cadherin-11 and PDGFRα extracellular domains. This study is the first to report an interaction between cadherin-11 and PDGFRα and adds to our growing understanding that cadherin-growth factor receptor interactions help balance the interplay between tissue growth and adhesion.

Histone demethylase JMJD3 regulates fibroblast-like synoviocyte-mediated proliferation and joint destruction in rheumatoid arthritis

Rheumatoid arthritis (RA) is an immune-mediated disease with the characteristics of progressive joint destruction, deformity, and disability. Epigenetic changes have been implicated in the development of some autoimmune disorders, resulting in an alteration of gene transcription. Here, we investigated how Jumonji C family of histone demethylases (JMJD3) regulated the proliferation and activation of fibroblast-like synoviocytes (FLSs), which are involved in RA joint destruction and pathologic process. The JMJD3 expression and proliferation markers in RA-FLS were higher than those in healthy-FLS and were upregulated in platelet-derived growth factor (PDGF)-induced FLS. Elevated JMJD3 promoted the proliferation and migration of FLS. Treatment with JMJD3 small interfering RNA or inhibitor glycogen synthase kinase (GSK) J4 led to decreased proliferation and migration of FLS. Interestingly, induction of proliferating cell nuclear antigen (PCNA), a major player of the cell-cycle regulation, was correlated with trimethylated lysine 27 in histone H3 loss around the gene promoters. The knockdown of JMJD3 abolished PCNA expression in PDGF-induced FLS and further inhibited cell proliferation and migration, suggesting that JMJD3/PCNA played a crucial role in aspects of FLS proliferation and migration. In vivo, the ability of GSK J4 to hinder collagen-induced arthritis (CIA) in DBA/1 mice was evaluated. We found that GSK J4 markedly attenuated the severity of arthritis in CIA mice. The therapeutic effects were associated with ameliorated joint swelling and reduced bone erosion and destruction. This study revealed how JMJD3 integrated with epigenetic processes to regulate RA-FLS proliferation and invasion. These data suggested that JMJD3 might contribute to rheumatoid synovial hyperplasia and have the potential as a novel therapeutic target for RA.-Jia, W., Wu, W., Yang, D., Xiao, C., Su, Z., Huang, Z., Li, Z., Qin, M., Huang, M., Liu, S., Long, F., Mao, J., Liu, X., Zhu, Y. Z. Histone demethylase JMJD3 regulates fibroblast-like synoviocyte-mediated proliferation and joint destruction in rheumatoid arthritis.

Disease-Specific Effects of Matrix and Growth Factors on Adhesion and Migration of Rheumatoid Synovial Fibroblasts

In rheumatoid arthritis (RA), cartilage and bone matrix are degraded, and extracellular matrix (ECM) proteins, acting as cellular activators, are liberated. Similar to ECM proteins, matrix-bound chemokines, cytokines, and growth factors (GFs) influence functional properties of key cells in RA, especially synovial fibroblasts. The role of these molecules on attachment, migration, and proinflammatory and prodestructive activation of RASFs was analyzed. Adhesion/migration of RASFs were examined under GF-enriched (GF⁺) or -reduced (GF^-) conditions with or without addition of matrix-associated GFs, TGF-β, and platelet-derived GF to GF^- or culture supernatants. Fibroblast adhesion and alterations in proinflammatory/prodestructive properties (e.g., IL-6/matrix metalloproteinase 3-release) in response to matrix-associated molecules were compared. Effects of GF⁺, GF^-, and other ECM components on human RASF-mediated cartilage invasion were examined in the SCID mouse model. RASF adhesion under GF^- conditions was significantly lower compared with GF⁺ conditions (6.8- versus 8.3-fold). This effect was specific for RA because control cells showed opposite effects (e.g., osteoarthritis synovial fibroblasts [SF]; GF^- versus GF⁺: 10.7- versus 8-fold). Addition of TGF-β to GF^- increased RASF attachment (12.7-fold) compared with other matrices and components. RASF adhesion to GF⁺ matrix resulted in the strongest IL-6 and matrix metalloproteinase-3 release, and was even more pronounced compared with supplementation of single GFs. In vivo, GF^- matrix decreased RASF-mediated cartilage invasion compared with GF⁺ matrix. ECM components and especially GFs when bound within ECM actively enhance RASF attraction and cartilage adhesion. This observation was specific for RASFs as a reverse behavior was observed for controls.

Hydrogel is Superior to Fibrin Gel as Matrix of Stem Cells in Alleviating Antigen-Induced Arthritis

Recently, therapy with bone marrow mesenchymal stem cells (BMMSCs) has been attempted to relieve rheumatoid arthritis (RA) and reconstruct cartilage injury. However, treatment has been unsuccessful in complete prevention of persistent cartilage destruction and resulted in inferior outcomes of cartilage regeneration. Scaffolds are an important construct in the field of cartilage tissue engineering, but their role in arthritis treatment has not yet been fully examined. Here, we transplanted two types of scaffold-assisted BMMSCs: fibrin gel- and poly(l-lactide-co-glycolide)-poly(ethylene glycol)-poly(l-lactide-co-glycolide) (PLGA-PEG-PLGA) hydrogel-assisted BMMSCs referred as FGB and HGB groups, respectively, into subchondral defects for the treatment of antigen-induced arthritis. The administration of exogenous BMMSCs ameliorated joint swelling and decreased both joint surface temperature and inflammatory cytokine levels in both groups. Immune cell composition of the inflammation of surrounding synovium, protection of adjacent cartilage, and improved cartilage repair were also observed. Overall, the HGB group had a better therapeutic efficacy than the FGB group. In conclusion, local transplantation of BMMSCs in subchondral defects presents a novel approach in inducing RA remission and recovery of RA-induced cartilage injury. To induce these changes, the selection of scaffold for cell support is exceedingly important. Further studies are needed regarding the treatment options of subchondral defects in arthritis based on modified scaffold development, application of defined MSCs sources, combination of pharmacotherapeutics, and the addition of factors that inhibit the processes of RA remission, promote the recovery of RA-induced cartilage injury and the relationship between these factors.

The proto-oncogene survivin splice variant 2B is induced by PDGF and leads to cell proliferation in rheumatoid arthritis fibroblast-like synoviocytes

Survivin is an independent prognostic factor for joint destruction in rheumatoid arthritis (RA). However, the expression and function of survivin in RA synoviocytes remain unclear. We certified the expression of survivin in RA synovial tissues and performed the experiment using RA fibroblast-like synoviocytes (RA-FLS) treated with siRNA. As a result, the expression levels of wild type (WT) survivin and the 2B splice variants in RA synovial tissues were higher than those in osteoarthritis tissue samples, and, these variants were highly expressed in RA-FLS. The expression levels of survivin-WT and -2B in the RA-FLS were upregulated by PDGF. Treatment with siRNA against survivin-2B led to decreased viability of PDGF-treated RA-FLS due to cell cycle suppression and apoptosis promotion, while the siRNA against all survivin isoforms did not affect the viability. Moreover, an overexpression of survivin-2B in RA-FLS led to cell proliferation through cell cycle activation and by conferring resistance to apoptosis. In conclusion, survivin-2B has an important role in RA-FLS proliferation. These data suggest that survivin-2B might contribute to rheumatoid synovial hyperplasia, and have the potential as a novel therapeutic target for RA.

Peroxidase enzymes regulate collagen extracellular matrix biosynthesis

Myeloperoxidase and eosinophil peroxidase are heme-containing enzymes often physically associated with fibrotic tissue and cancer in various organs, without any direct involvement in promoting fibroblast recruitment and extracellular matrix (ECM) biosynthesis at these sites. We report herein novel findings that show peroxidase enzymes possess a well-conserved profibrogenic capacity to stimulate the migration of fibroblastic cells and promote their ability to secrete collagenous proteins to generate a functional ECM both in vitro and in vivo. Mechanistic studies conducted using cultured fibroblasts show that these cells are capable of rapidly binding and internalizing both myeloperoxidase and eosinophil peroxidase. Peroxidase enzymes stimulate collagen biosynthesis at a post-translational level in a prolyl 4-hydroxylase-dependent manner that does not require ascorbic acid. This response was blocked by the irreversible myeloperoxidase inhibitor 4-amino-benzoic acid hydrazide, indicating peroxidase catalytic activity is essential for collagen biosynthesis. These results suggest that peroxidase enzymes, such as myeloperoxidase and eosinophil peroxidase, may play a fundamental role in regulating the recruitment of fibroblast and the biosynthesis of collagen ECM at sites of normal tissue repair and fibrosis, with enormous implications for many disease states where infiltrating inflammatory cells deposit peroxidases.

TNFα, PDGF, and TGFβ synergistically induce synovial lining hyperplasia via inducible PI3Kδ

OBJECTIVES

To determine the mechanism underlying hypertrophic synovium in rheumatoid arthritis (RA).

METHODS

We examined micromass cultures of fibroblast-like synoviocytes (FLSs) stimulated with tumor necrosis factor α (TNFα), platelet-derived growth factor (PDGF), and/or transforming growth factor β (TGFβ). The hypertrophic architecture of the micromasses, expression of phosphoinositide 3 kinase (PI3K) isoforms, and persistent activation of PI3K-Akt pathways were investigated. FLSs transfected with siRNA were also examined in the micromass cultures.

RESULTS

The combination of TNFα, PDGF, and TGFβ (TPT condition) induced obvious hypertrophic architecture of the intimal lining layer in FLSs in micromass cultures, and was accompanied by upregulated expression of matrix metalloproteinase-3 (MMP3), Cadherin-11, and PI3Kδ. In monolayer FLSs, the TPT condition enhanced the expression of PI3Kδ and persistent activation of the PI3K-Akt pathway. Knockdown of PI3Kδ significantly inhibited the formation of the hypertrophic synovial lining in the TPT condition.

CONCLUSIONS

These results collectively indicate that inducible PI3Kδ plays a crucial role in persistent activation of PI3K-Akt in FLSs, and in the formation of a hypertrophic synovial lining. PI3Kδ may be an alternative treatment target for the regulation of proliferative synovium in RA.

Platelet-derived growth factor and transforming growth factor beta synergistically potentiate inflammatory mediator synthesis by fibroblast-like synoviocytes

Introduction

The objective of this study was to model the effects of transforming growth factor beta (TGF-β) and platelet-derived growth factor (PDGF), both present in rheumatoid arthritis (RA) synovia, on the behavior of fibroblast-like synoviocytes (FLS) in response to pro-inflammatory cytokine (interleukin (IL)1β, tumor necrosis factor-alpha (TNFα)) challenge.

Methods

Gene and protein expression by fibroblast-like synoviocytes in vitro was studied by quantitative Polymerase Chain Reaction (qPCR), ELISA and multiplex bead cytokine assays. Intracellular signaling pathway activation was determined by Western blot for phospho-kinases and the use of specific inhibitors.

Results

In combination, TGF-β and PDGF (2GF) synergistically augmented TNFα- or IL1β-induced matrix metalloproteinase 3 (MMP3), IL6, IL8, and macrophage inflammatory protein 1 alpha (MIP1α) secretion by FLS. Other FLS-derived mediators remained unaffected. Individually, neither growth factor significantly potentiated TNFα or IL1β-induced MMP3 secretion, and only slightly enhanced IL6. The effect of 2GF on TNFα-induced gene expression was transcriptionally mediated; blocked by imatinib mesylate; and occurred even if 2GF was added as much as four hours prior to TNFα. In addition, a 15-minute pulse of 2GF four hours prior to TNFα stimulation yielded a synergistic response. The extracellular-signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K) signaling pathways were induced for at least four hours by 2GF, as demonstrated by persistently upregulated levels of phospho-Akt and phospho-ERK. However, pharmacologic inhibitor studies demonstrated that the potentiating action of 2GF was dependent on PI3 kinase only, and not on ERK.

Conclusions

The combination of PDGF and TGF-β dramatically potentiates FLS response to cytokines in a receptor-mediated and PI3 kinase-dependent fashion. These data suggest that 2GF contribute to synovitis by directing synovial fibroblasts toward a more aggressive phenotype in response to TNFα. Therefore, inhibition of growth factor signaling may constitute a complementary therapeutic approach to cytokine-targeted treatments for RA.

Imatinib mesylate inhibited rat adjuvant arthritis and PDGF-dependent growth of synovial fibroblast via interference with the Akt signaling pathway

Overgrowth of the synovium plays an important role in the pathogenesis of rheumatoid arthritis (RA). Platelet-derived growth factor (PDGF) is one of the most potent mitogenic factors of synovial cells, and imatinib mesylate (imatinib) is a specific inhibitor of the PDGF receptor tyrosine kinase. The aim of this study was to elucidate the anti-rheumatic activity of imatinib. The in vivo effects of imatinib were assessed by evaluating the sequential manifestation of adjuvant-induced arthritis in rats using paw volume and clinical scores. Imatinib was found to inhibit rat adjuvant-induced arthritis, but the inhibitory effects were incomplete. To confirm the mechanism of anti-rheumatic-activity of imatinib, we assessed the in vitro effects of imatinib on the proliferation of RA synovial fibroblast-like cells (RASFs) using a MTT assay. Intracellular signaling of PDGF was evaluated by Western blot analysis. Platelet-derived growth factor was found to induce a significant proliferation of RASFs, while imatinib inhibited PDGF-induced proliferation of RASF. Imatinib also inhibited PDGF-induced phosphorylation of the PDGF receptor and Akt, whereas constitutive activated extracellular signal-regulated kinase was not inhibited by imatinib. In contrast, imatinib did not inhibit transforming growth factor beta- and basic fibroblast growth factor-induced proliferation of RASF. Oral administration of imatinib ameliorated adjuvant-induced arthritis in rats, and it inhibited PDGF-induced RASF proliferation through disruption of the PDGF-R to Akt kinase signaling pathway. Because imatinib cannot inhibit the non-PDGF-dependent proliferation of RASFs, the anti-rheumatic effect of imatinib may be incomplete. The development of inhibitors of RASF proliferation may lead to the successful treatment of RA.

Release of growth factors after arthroscopic acromioplasty

It has recently been postulated that a variety of growth factors may be released from cancellous bone after an acromioplasty. The aim of this study was to demonstrate the presence of growth factors in the subacromial space after acromioplasty. Between October 2006 and March 2007, 23 patients underwent arthroscopic acromioplasty. A sample of at least 3 ml of fluid from the shoulder was obtained 15 min after the end of the procedure. At the same time another sample of 3 ml of the patient's venous blood was obtained as a control. The concentrations of growth factors in the fluids collected were determined using enzyme-linked immunosorbent assay (ELISA). The growth factors assayed were platelet-derived growth factor-AB (PDGF-AB), basic fibroblast growth factor basic (bFGF) and transforming growth factor beta 1 (TGF-beta1). The concentrations of TGF-beta1 (p = 0.0001), PDGF-AB (p = 0.02), and bFGF (p < 0.0001) were significantly higher in the fluid from the subacromial space than in the blood sample. There are high concentrations of several growth factors in the subacromial space after acromioplasty.

Platelet-derived growth factor as a therapeutic target for systemic autoimmune diseases

Some systemic rheumatic diseases and disorders, especially fibrotic and vascular disorders, are often refractory to corticosteroid therapy. Recently, ever accumulating evidence suggests that platelet-derived growth factor (PDGF) is involved in those refractory diseases. Imatinib mesylate inhibits the activation of PDGF receptor as well as c-Abl, Bcr-Abl and c-Kit tyrosine kinases. It has therefore been widely used for the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors. Imatinib effectively suppresses the activation and proliferation of fibroblasts, mesangial cells and smooth muscle cells both in vitro and in vivo. Additionally, it has recently been reported that some patients with rheumatoid arthritis or idiopathic pulmonary arterial hypertension demonstrated a good clinical response to imatinib therapy. Imatinib may therefore overcome the limitations of current therapeutic strategy with corticosteroids and immunosuppressive agents for refractory diseases, such as systemic sclerosis and interstitial lung diseases, without clinical intolerability.

Platelet-derived growth factor as a therapeutic target for systemic autoimmune diseases

Some systemic rheumatic diseases and disorders, especially fibrotic and vascular disorders, are often refractory to corticosteroid therapy. Recently, ever accumulating evidence suggests that platelet-derived growth factor (PDGF) is involved in those refractory diseases. Imatinib mesylate inhibits the activation of PDGF receptor as well as c-Abl, Bcr-Abl and c-Kit tyrosine kinases. It has therefore been widely used for the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors. Imatinib effectively suppresses the activation and proliferation of fibroblasts, mesangial cells and smooth muscle cells both in vitro and in vivo. Additionally, it has recently been reported that some patients with rheumatoid arthritis or idiopathic pulmonary arterial hypertension demonstrated a good clinical response to imatinib therapy. Imatinib may therefore overcome the limitations of current therapeutic strategy with corticosteroids and immunosuppressive agents for refractory diseases, such as systemic sclerosis and interstitial lung diseases, without clinical intolerability.

Pharmacokinetics, efficacy, and safety of short-term (12 weeks) etanercept for methotrexate-refractory polyarticular juvenile idiopathic arthritis in Japan

We examined and evaluated the pharmacokinetics, efficacy, and safety of etanercept in patients with methotrexate (MTX)-refractory polyarticular juvenile idiopathic arthritis (JIA) in Japan. All MTX-refractory polyarticular JIA patients 4-17 years old received 0.4 mg of etanercept per kilogram of body weight subcutaneously twice weekly for up to 3 months in the open-label, prospective, and multicenter trial. A response was defined as an improvement of 30%, 50%, 70%, or more from baseline in at least three of six indicators of disease activity, with no more than one indicator worsening by more than 30% from baseline (30%, 50%, or 70% definition of improvement, respectively), and disease activity score (DAS28) by EULAR (European League Against Rheumatism) response criteria. At the end of the 12-week study, 20 of the 22 patients (90.9%) had responses with both 30% and 50% definition of improvement after etanercept treatment. To our surprise, 15 of 22 patients (68.2%) had a response with 70% definition of improvement. Moreover, in DAS28, eight patients were evaluated as having a good response and there were no patients with a poor response to etanercept. Treatment had to be stopped in one patient who developed joint contracture during the study period, but there were no significant adverse events in the other patients. In conclusion, treatment with etanercept leads to significant improvement in patients with active polyarticular JIA in Japan. Etanercept is well tolerated by pediatric patients as well as adults.

Imatinib mesylate inhibits proliferation of rheumatoid synovial fibroblast-like cells and phosphorylation of Gab adapter proteins activated by platelet-derived growth factor

Receptors for platelet-derived growth factor (PDGF) are abundantly expressed on synovial fibroblast-like (SFL) cells from patients with rheumatoid arthritis (RA), and stimulation with PDGF enhances both the anchorage-dependent and -independent growth of RA-SFL cells. To elucidate the molecular mechanisms responsible for the excessive growth of RA-SFL cells and to seek a novel molecular-targeting therapy for RA, we examined the expression of adapter proteins and the effect of the specific inhibition of PDGF receptor activation by imatinib mesylate. Cultured SFL cells were used in the present study after 2-5 passages. The anchorage-dependent and -independent growth patterns of the SFL cells were evaluated using a tetrazolium-based assay and colony formation in 0.3% agar, respectively. Adapter proteins Gab1 and Gab2 were expressed in RA-SFL cells, and both proteins were rapidly (< 1 min) tyrosine-phosphorylated after the stimulation of RA-SFL cells with 10 ng/ml of PDGF and, to a lesser extent, after stimulation with 100 ng/ml of epidermal growth factor (EGF). The inhibition of PDGF receptor tyrosine kinase activation by 1 microM or less of imatinib mesylate specifically suppressed the PDGF-dependent, but not EGF-dependent, tyrosine phosphorylation of various proteins. Moreover, imatinib mesylate abolished both the anchorage-dependent and -independent proliferation of RA-SFL cells induced by PDGF stimulation. These results suggest that Gab adapter proteins are expressed and likely to be involved in the growth signalling of rheumatoid synovial cells and that imatinib mesylate, a key drug in the treatment of chronic myeloid leukaemia, may also be effective for the treatment of RA.

Imatinib mesylate inhibits platelet derived growth factor stimulated proliferation of rheumatoid synovial fibroblasts

Synovial fibroblast is the key cell type in the growth of the pathological synovial tissue in arthritis. Here, we show that platelet-derived growth factor (PDGF) is a potent mitogen for synovial fibroblasts isolated from patients with rheumatoid arthritis. Inhibition of PDGF-receptor signalling by imatinib mesylate (1muM) completely abrogated the PDGF-stimulated proliferation and inhibited approximately 70% of serum-stimulated proliferation of synovial fibroblasts. Similar extent of inhibition was observed when PDGF was neutralized with anti-PDGF antibodies, suggesting that imatinib mesylate does not inhibit pathways other than those mediated by PDGF-receptors. No signs of apoptosis were detected in synovial fibroblasts cultured in the presence of imatinib. These results suggest that imatinib mesylate specifically inhibits PDGF-stimulated proliferation of synovial fibroblasts, and that inhibition of PDGF-receptors could represent a feasible target for novel antirheumatic therapies.

CDP-870 (certolizumab) in rheumatoid arthritis

The development of biological anti-TNF-alpha therapy has revolutionised the treatment of rheumatoid arthritis and other inflammatory diseases, and has identified a worldwide market for expensive yet effective therapies for chronic diseases. Certolizumab (CDP-870) is a new agent that employs a novel strategy to neutralise TNF-alpha--namely the prokaryotic expression of TNF-alpha-specific Fab antibody fragments, coupled to polyethylene glycol--to produce a drug that is potentially less expensive to manufacture than other anti-TNF-alpha agents and which may be administered by subcutaneous injection once a month. The background to the ongoing development of this new agent and its clinical effects are discussed in this article.

Etanercept: an updated review of its use in rheumatoid arthritis, psoriatic arthritis and juvenile rheumatoid arthritis

Etanercept is a subcutaneously administered biological response modifier that binds and inactivates tumour necrosis factor-alpha, a proinflammatory cytokine. In patients with early active rheumatoid arthritis, etanercept 25mg twice weekly was associated with a more rapid improvement in disease activity and a significantly greater cumulative response than methotrexate over 12 months of treatment in a randomised, double-blind trial. In addition, etanercept recipients showed a slower rate of radiographic progression and a more rapid improvement in quality of life than methotrexate recipients. The efficacy of etanercept was maintained at 3 years' follow-up. Etanercept was also significantly better than placebo at reducing disease activity in patients who had an inadequate response to previous treatment with disease-modifying antirheumatic drugs (DMARDs) in several well controlled trials. At study end (after 3 or 6 months' treatment), the percentage of patients achieving an American College of Rheumatology 20% (ACR20) response with etanercept (25mg or 16 mg/m(2) twice weekly) was 59 to 75% as monotherapy and 71% in combination with methotrexate; corresponding placebo response rates were 11 to 14% and 27%, respectively. Response has been maintained in patients who continued treatment for up to 5 years. In patients with psoriatic arthritis, etanercept 25mg twice weekly significantly reduced disease activity and improved skin lesions in two double-blind, placebo-controlled, 12- to 24-week trials. In the 24-week study, ACR20 response rates (50 vs 13%), psoriatic arthritis response rates (70 vs 23%) and the median improvement in skin lesions (33 vs 0%) were significantly greater in etanercept than in placebo recipients. In patients with polyarticular-course juvenile rheumatoid arthritis, etanercept resulted in improvements in all measures of disease activity and was significantly more effective than placebo at reducing disease flare. Eighty percent of patients receiving etanercept achieved a >or=30% reduction in disease activity over 7 months of treatment, and this was maintained for up to 2 years in a trial extension. Etanercept was generally well tolerated in children and adults in clinical trials; the most commonly occurring adverse effects included injection site reactions, infection, headache, rhinitis and dizziness. In conclusion, etanercept has emerged as an important new treatment option in inflammatory arthritis. Etanercept provides rapid and sustained improvements in disease activity in patients with early and DMARD-refractory rheumatoid arthritis and has been shown to inhibit radiographic progression in those with early disease. Well controlled studies have also demonstrated the efficacy of etanercept in patients with psoriatic arthritis or polyarticular-course juvenile rheumatoid arthritis.

Elevated angiogenin levels in synovial fluid from patients with inflammatory arthritis and secretion of angiogenin by cultured synovial fibroblasts

Angiogenesis is a key process in the pathogenesis of inflammatory arthritis. Angiogenin is one of the most potent inducers of neovascularization in experimental models in vivo. To look for evidence that angiogenin is involved in inflammatory joint disease, we examined plasma and synovial fluid (SF) samples from rheumatology patients and synovial fibroblast cell culture supernatants. Angiogenin levels were determined by radioimmunoassay and ELISA. Plasma angiogenin concentrations ranged from 96 to 478 ng/ml, with no significant difference between patients and normal controls. In SF, angiogenin concentrations were significantly higher in patients with acute or chronic synovitis (rheumatoid arthritis (RA): median, 104 ng/ml; range 13-748, n = 14; crystal-induced arthritis (CIA): median, 149 ng/ml; range, 37-616, n = 14, and other chronic inflammatory arthritis: median, 42 ng/ml; range, 15-205; n = 9) than in the 18 patients with osteoarthritis (OA) (median, 20 ng/ml; range 8-116) (P < 0.0001, anova). Angiogenin levels in SF from RA patients in remission with secondary OA were similar to those achieved in primary OA, and decreased in parallel with the resolution of acute gout. Angiogenin protein was released by cultured synovial fibroblasts from OA and RA patients, and reached 1.18 ng/106 cells/day. These data suggest that angiogenin may mediate local inflammation in arthritis via effects on angiogenesis and leucocyte regulation.

Results of a phase-I/II randomized, masked, placebo-controlled trial of recombinant human interleukin-11 (rhIL-11) in the treatment of subjects with active rheumatoid arthritis

Interleukin-11 (IL-11) is a pleiotropic cytokine that regulates the growth and development of hematopoietic stem cells and decreases the proinflammatory mediators of cytokine and nitric oxide production. In animal models of arthritis, treatment with recombinant human IL-11 (rhIL-11) reduces both the level of synovitis and the histologic lesion scores in the joints. The goal of this phase-I/II study in adults with rheumatoid arthritis (RA) was to evaluate the safety and clinical activity of different doses and schedules of rhIL-11 in patients with active RA for whom treatment with at least one disease-modifying antirheumatic drug had failed. This was a multicenter, randomized, placebo-controlled trial that evaluated the safety and tolerability of rhIL-11 in 91 patients with active RA. rhIL-11 was administered subcutaneously; patients were randomized into one of five treatment groups (ratio of rhIL-11 to placebo, 4:1). Patients were treated for 12 weeks with either 2.5 or 7.5 microg/kg of rhIL-11 or placebo twice per week or 5 or 15 microg/kg of rhIL-11 or placebo once per week. The status of each subject's disease activity in accordance with the American College of Rheumatology (ACR) criteria was assessed before, during, and after completion of administration of the study drug. Administration of rhIL-11 was well tolerated at all doses and schedules. The most frequent adverse event was a reaction at the injection site. The data suggest a statistically significant reduction in the number of tender joints (P < 0.008) at the 15 microg/kg once-weekly dose schedule but showed no overall significant benefit at the ACR criterion of a 20% response. The trial showed rhIL-11 to be safe and well tolerated at a variety of doses and schedules over a 12-week treatment period in patients with active RA. The only adverse event clearly associated with rhIL-11 administration was reaction at the injection site.

Etanercept in children with polyarticular juvenile rheumatoid arthritis. Pediatric Rheumatology Collaborative Study Group

BACKGROUND

We evaluated the safety and efficacy of etanercept, a soluble tumor necrosis factor receptor (p75):Fc fusion protein, in children with polyarticular juvenile rheumatoid arthritis who did not tolerate or had an inadequate response to methotrexate.

METHODS

Patients 4 to 17 years old received 0.4 mg of etanercept per kilogram of body weight subcutaneously twice weekly for up to three months in the initial, open-label part of a multicenter trial. Those who responded to treatment then entered a double-blind study and were randomly assigned to receive either placebo or etanercept for four months or until a flare of the disease occurred. A response was defined as an improvement of 30 percent or more in at least three of six indicators of disease activity, with no more than one indicator worsening by more than 30 percent.

RESULTS

At the end of the open-label study, 51 of the 69 patients (74 percent) had had responses to etanercept treatment. In the double-blind study, 21 of the 26 patients who received placebo (81 percent) withdrew because of disease flare, as compared with 7 of the 25 patients who received etanercept (28 percent) (P=0.003). The median time to disease flare with placebo was 28 days, as compared with more than 116 days with etanercept (P<0.001). In the double-blind study, there were no significant differences between the two treatment groups in the frequency of adverse events.

CONCLUSIONS

Treatment with etanercept leads to significant improvement in patients with active polyarticular juvenile rheumatoid arthritis. Etanercept is well tolerated by pediatric patients.

Involvement of fibroblast growth factor-2 in joint destruction of rheumatoid arthritis patients

OBJECTIVE

To investigate the effect of the synovial fluid from knee joints of rheumatoid arthritis (RA) patients with different severities of joint destruction on osteoclastogenesis and bone resorption.

METHODS

Synovial fluid was harvested from the knee joints of 59 RA patients and 37 ostcoarthritis (OA) patients. RA patients with Larsen's knee grade 1-3 were classified as mild RA (n = 30) and those with grade 4 or 5 as severe RA (n = 29). Cytokine concentrations in synovial fluid were measured by ELISA. Osteoclastogenesis was measured by tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cell (MNC) formation in a co-culture of mouse osteoblastic cells and bone marrow cells, and bone resorption by 45Ca release from pre-labelled cultured neonatal mouse calvariae.

RESULTS

The synovial fluid of severe RA patients significantly stimulated TRAP-positive MNC formation and 45Ca release compared to those of mild RA and OA patients. Among the bone-resorptive cytokines fibroblast growth factor-2 (FGF-2), tumour necrosis factor alpha (TNF-alpha), interleukin-1alpha (IL-1alpha), IL-6 and soluble IL-6 receptor (sIL-6R), only FGF-2 concentration in the synovial fluid was positively correlated to Larsen's grade, and severe RA patients showed significantly higher FGF-2 concentrations than mild RA patients. Osteoclastogenesis in a co-culture system which was stimulated by the synovial fluid of severe RA patients was significantly inhibited by a neutralizing antibody against FGF-2 and this inhibition was stronger than antibodies against other cytokines.

CONCLUSION

The increase in endogenous FGF-2 levels in the synovial fluid of RA patients may play a role in the joint destruction by inducing osteoclastogenesis.

Etanercept: a review of its use in rheumatoid arthritis

Etanercept, a fusion protein consisting of the extracellular ligand-binding domain of the 75kD receptor for tumour necrosis factor-alpha and the constant portion of human IgG1, is administered by subcutaneous injection and is the first specific anti-cytokine therapy approved for rheumatoid arthritis. In patients with active rheumatoid arthritis [American College of Rheumatology (ACR) functional class I to III] who had failed to respond to previous treatment with > or = 1 disease-modifying antirheumatic drug (DMARD), etanercept, alone or in combination with methotrexate, produced improvements in all components included in the ACR core set of disease activity measures. A dose-response effect was apparent with etanercept 0.25 to 16 mg/m2 twice weekly in a randomised, double-blind study in 180 patients. The mean number of swollen or tender joints at the end of the 12-week study decreased by >50% in patients treated with etanercept 16 mg/m2 twice weekly and by <25% in patients treated with placebo. In a 24-week multicentre, randomised, double-blind study in 234 patients who were not allowed to use DMARDs, etanercept 10 or 25mg twice weekly had a rapid onset of effect. Significantly more patients treated with etanercept 25mg twice weekly than placebo experienced 20 (ACR 20), 50 (ACR 50) or 70% (ACR 70) improvement in ACR criteria after 3 and 6 months. Limited evidence suggests that the therapeutic effects of etanercept are maintained for up to 2 years. Etanercept 25mg twice weekly produced significant improvement in patients receiving oral or subcutaneous methotrexate 10 to 25 mg/week in a multicentre, randomised, double-blind, placebo-controlled study. A significantly greater proportion of patients treated with etanercept plus methotrexate (71%) than placebo plus methotrexate (27%) achieved the ACR 20 criteria after 6 months. Moreover, 39 and 15% of patients treated with etanercept plus methotrexate, but no placebo plus methotrexate recipients, had achieved the ACR 50 and ACR 70 criteria at this time. Etanercept 0.4 mg/kg twice weekly reduced disease activity in a preliminary, noncomparative study in 69 children aged > or =4 years with refractory juvenile rheumatoid arthritis. Although the overall frequency of infections was similar in patients treated with etanercept or placebo, upper respiratory tract infections were more common in patients treated with etanercept (29%) than placebo (16%). Injection site reactions occurred more frequently in etanercept- than placebo-treated patients, but did not bias the results of any study.

CONCLUSIONS

When etanercept is administered alone or in combination with methotrexate in patients with refractory rheumatoid arthritis, significant reductions in disease activity occur within 2 weeks and are sustained for at least 6 months. Thus, etanercept appears to be particularly well suited for use in patients who fail to respond to treatment with DMARDs.

A trial of etanercept, a recombinant tumor necrosis factor receptor:Fc fusion protein, in patients with rheumatoid arthritis receiving methotrexate

BACKGROUND

Patients treated with methotrexate for rheumatoid arthritis often improve but continue to have active disease. This study was undertaken to determine whether the addition of etanercept, a soluble tumor necrosis factor receptor (p75):Fc fusion protein (TNFR:Fc), to methotrexate therapy would provide additional benefit to patients who had persistent rheumatoid arthritis despite receiving methotrexate.

METHODS

In a 24-week, double-blind trial, we randomly assigned 89 patients with persistently active rheumatoid arthritis despite at least 6 months of methotrexate therapy at a stable dose of 15 to 25 mg per week (or as low as 10 mg per week for patients unable to tolerate higher doses) to receive either etanercept (25 mg) or placebo subcutaneously twice weekly while continuing to receive methotrexate. The primary measure of clinical response was the American College of Rheumatology criteria for a 20 percent improvement in measures of disease activity (ACR 20) at 24 weeks.

RESULTS

The addition of etanercept to methotrexate therapy resulted in rapid and sustained improvement. At 24 weeks, 71 percent of the patients receiving etanercept plus methotrexate and 27 percent of those receiving placebo plus methotrexate met the ACR 20 criteria (P<0.001); 39 percent of the patients receiving etanercept plus methotrexate and 3 percent of those receiving placebo plus methotrexate met the ACR 50 criteria (for a 50 percent improvement) (P<0.001). Patients receiving etanercept plus methotrexate had significantly better outcomes according to all measures of disease activity. The only adverse events associated with etanercept were mild injection-site reactions, and no patient withdrew from the study because of adverse events associated with etanercept.

CONCLUSIONS

In patients with persistently active rheumatoid arthritis, the combination of etanercept and methotrexate was safe and well tolerated and provided significantly greater clinical benefit than methotrexate alone.

Genetic and immunologic studies of patients on procainamide

Forty (40) patients with cardiac arrhythmias receiving procainamide (PA) therapy and 24 patients who were receiving other drugs for their cardiac disorders were investigated for class II HLA phenotypes and their DRB1*04 and DQB1*03 subtypes. Other genetic marker evaluations in the PA patients included: 1) class III MHC C4A and C4B null alleles of complement; and, 2) acetylation phenotype. Twenty (20) of the PA patients were also tested for the ability of their stimulated cells to secrete Interleukin-1 (IL-1 beta) and tumor necrosis factor (TNF alpha). We also examined the spontaneous production of these cytokines by peripheral blood leukocytes (PBL) from patients who were receiving chronic PA treatment. The results revealed no association of acetylation phenotypes with the class II HLA phenotypes nor class III MHC C4 allotypes in these patients. The results did show a significant increase in class III C4 complement allotypes in the PA patients when compared to the controls. The results also showed a significant increase in autoantibodies and DQw3 phenotypes in the PA patient group when compared to control populations. Results of spontaneous IL-1 and TNF production suggested there may be an association of select class II HLA phenotypes in some patients and this may be relevant to host responsiveness to PA treatment.

Role of cytokines in rheumatoid arthritis

Analysis of cytokine mRNA and protein in rheumatoid arthritis tissue revealed that many proinflammatory cytokines such as TNF alpha, IL-1, IL-6, GM-CSF, and chemokines such as IL-8 are abundant in all patients regardless of therapy. This is compensated to some degree by the increased production of anti-inflammatory cytokines such as IL-10 and TGF beta and cytokine inhibitors such as IL-1ra and soluble TNF-R. However, this upregulation in homeostatic regulatory mechanisms is not sufficient as these are unable to neutralize all the TNF alpha and IL-1 produced. In rheumatoid joint cell cultures that spontaneously produce IL-1, TNF alpha was the major dominant regulator of IL-1. Subsequently, other proinflammatory cytokines were also inhibited if TNF alpha was neutralized, leading to the new concept that the proinflammatory cytokines were linked in a network with TNF alpha at its apex. This led to the hypothesis that TNF alpha was of major importance in rheumatoid arthritis and was a therapeutic target. This hypothesis has been successfully tested in animal models, of, for example, collagen-induced arthritis, and these studies have provided the rationale for clinical trials of anti-TNF alpha therapy in patients with long-standing rheumatoid arthritis. Several clinical trials using a chimeric anti-TNF alpha antibody have shown marked clinical benefit, verifying the hypothesis that TNF alpha is of major importance in rheumatoid arthritis. Retreatment studies have also shown benefit in repeated relapses, indicating that the disease remains TNF alpha dependent. Overall these studies demonstrate that analysis of cytokine expression and regulation may yield effective therapeutic targets in inflammatory disease.

Radiation and the lung: a reevaluation of the mechanisms mediating pulmonary injury

Recent data from several investigators, including our unit, have provided additional information on the etiology of radiation-induced lung damage. These data suggest that there are two quite separate and distinct mechanisms involved: (a) classical radiation pneumonitis, which ultimately leads to pulmonary fibrosis is primarily due to radiation-induced local cytokine production confined to the field of irradiation; and (b) sporadic radiation pneumonitis, which is an immunologically mediated process resulting in a bilateral lymphocytic alveolitis that results in an "out-of-field" response to localized pulmonary irradiation. Both animal experiments and human studies show that classical radiation pneumonitis has a threshold dose and a narrow sigmoid dose-response curve with increasing morbidity and mortality over a very small dose range. Clinical pneumonitis rarely causes death, whereas in the animal and human studies of classical radiation pneumonitis, all subjects will eventually suffer irreversible pulmonary damage and death. The description of classical radiation pneumonitis is that of an acute inflammatory response to lung irradiation, which is confined to the area of irradiation. Recent studies have also shown that irradiation induces gene transcription and results in the induction and release of proinflammatory cytokines and fibroblast mitogens in a similar fashion to other chronic inflammatory states, and which ultimately results in pulmonary fibrosis. The description of classical radiation pneumonitis does not adequately explain the following observed clinical characteristics: (a) the unpredictable and sporadic onset; (b) the occurrence in only a minority of patients; (c) the dyspnoea experienced, which is out of proportion to the volume of lung irradiated; and (d) the resolution of symptoms without sequelae in the majority of patients. We have demonstrated a bilateral lymphocytic alveolitis of activated T lymphocytes and a diffuse increase in gallium lung scan uptake in patients studied before and 4 to 6 weeks after strictly unilateral lung irradiation. This is suggestive of a hypersensitivity pneumonitis, which gives rise to an "out-of-field" response to localized lung irradiation and hence more accurately describes the clinical picture of radiation pneumonitis. Reevaluation of the mechanisms of pulmonary injury from irradiation suggest that (a) a new term, sporadic radiation pneumonitis, should be introduced to describe the clinical picture of radiation pneumonitis, which is not adequately explained by the classical description and is quite clearly an entirely different process; and (b) that the chronic response to localized lung irradiation that leads to pulmonary fibrosis is largely mediated through the induction and release of tissues cytokines.

Laboratory findings and pathology of psoriatic arthritis

Over recent years there has been a great deal of interest in the immunology, molecular biology and pathology of psoriasis and PsA. The pathogenetic mechanisms in PsA are less well understood than those described for psoriasis. There are almost certainly genetic and immune components. What is not clear is whether there is a primary immune defect or whether unknown stimuli lead to the recruitment of the immune system and establishment of the disease; nor is it absolutely clear whether PsA is an extension of psoriasis in certain prone individuals. Vascular abnormalities are the earliest histopathological changes to occur in the psoriatic plaque and are also prominent in the psoriatic synovium. Espinoza et al (1982) have suggested there may be a primary vascular defect in PsA. The fact that vascular changes occur before infiltration of immunocompetent cells and are the first changes to resolve with treatment of psoriasis is likely to be significant. Abnormalities in the cellular kinetics and growth factor sensitivity of keratinocytes, fibroblasts and synoviocytes have been highlighted previously. The ability of these cells to produce growth factors and express HLA class II antigens demonstrates the potential for them to initiate and maintain inflammation. The development and possible increased incidence of PsA in patients with such profound immunodeficiency as acquired immune deficiency syndrome suggests that T helper cells do not play a significant role in the establishment of the disease (Arnett et al, 1991). Previously, many immune changes were described. Unfortunately they are non-specific and do not indicate a fundamental defect or marker of PsA. Vasey (1985) has suggested that insidious exposure to Gram-positive bacteria from the gut, tonsils and psoriatic plaques results in chronically stimulated monocytes, macrophages and dendritic cells. These cells are able to migrate throughout the body. Repeated microtrauma may result in the homing of these cells to sites of injury in the skin, synovium and tendons. Interaction with genetically hyperactive synoviocytes and keratinocytes with concomitant release of growth factors may precipitate early lesions of psoriasis and PsA. This hypothesis needs to be substantiated, but it ties together some of the varying observations seen. Many abnormal laboratory findings have been described. Unfortunately, none of the serological changes is sufficiently specific to be of great help in diagnosis. CRP levels and the ESR remain the best promise as markers of the inflammatory component of the arthritis, while other indicators correlate with certain facets of the disease pathology, but as yet have not found a true niche in the management of PsA.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of Tenidap on cytokine induced proliferation of human synovial fibroblasts in vitro

OBJECTIVES

Tenidap, a new anti-rheumatic agent, is a lipoxygenase and cyclooxygenase inhibitor, and is reported to inhibit the production and action of interleukin 1 (IL-1). Since eicosanoids, IL-1, and other cytokines may influence the growth of fibroblasts in the joint synovium the study was carried out to determine the effects of Tenidap on cytokine induced proliferation of these cells in vitro.

METHODS

Cell cultures derived from patients with a variety of rheumatic diseases were cultured in different concentrations of Tenidap sodium, with or without IL-1, tumour necrosis factor alpha (TNF), IL-6, basic fibroblast growth factor (bFGF), or transforming growth factor beta (TGF beta). Cell proliferation was measured using a crystal violet colourimetric assay. Prostaglandin E2 levels in culture supernatants were measured by radioimmunoassay.

RESULTS

Tenidap at concentrations above 10 micrograms/ml inhibited cell growth, while at 1.25-5 micrograms/ml there was a small but significant increase in proliferation compared with controls. A further increase in growth was obtained when cells were incubated with Tenidap+IL-1, TNF or bFGF, and this was significantly higher than in the presence of any cytokine alone. Stimulation of IL-1 induced growth by Tenidap was reduced by addition of high levels of exogenous PGE2 (100 ng/ml) although growth was still higher than in IL-1 alone.

CONCLUSIONS

Depending on concentration, Tenidap may inhibit or stimulate synovial fibroblast growth. Our results suggest that augmentation of growth by low concentrations cannot be explained by inhibition of PGE2 production alone. Tenidap may directly stimulate cell growth or may block other fibroblast factors which are involved in control of cytokine induced proliferation.

Fibroblast growth factors in connective tissue disease associated interstitial lung disease

Fibrosis is a major cause of morbidity and mortality in chronic inflammatory diseases, especially interstitial pulmonary disorders. Fibroproliferation is an important part of this fibrotic response, and is mediated largely through growth factors such as platelet-derived growth factor (PDGF), insulin-like growth factor (IGF) I and tumour necrosis factor-alpha (TNF-alpha). Although there is some evidence implicating these cytokines in fibrotic disorders, strong evidence in vivo is almost nonexistent. In order to ascertain the role that these factors play in inflammatory lung disorders associated with connective tissue diseases, alveolar mononuclear cells have been obtained from subjects by bronchoalveolar lavage and assessed for the spontaneous release of fibroblast growth factors. The study population consisted of subjects with a variety of different connective tissue disorders, both with and without inflammatory pulmonary complications. It was found that lavage cells spontaneously secreted fibroblast growth factor activity over 24 h with maximum activity detected at 6 to 12 h. Growth factor activity could be detected in most subjects with connective tissue disease-associated inflammatory lung disease and some normal subjects, but the amount of growth factor activity was much higher in the former than in the latter. By means of antibody depletion experiments all growth factor activity from lavage cells of normal patients was attributable to TNF-alpha while patients with interstitial lung disease secreted large amounts of PDGF and fibronectin in addition to TNF-alpha. Approximately 40-50% of the total released growth factor activity could be accounted for by PDGF, and 100% by the combination of PDGF, TNF-alpha and fibronectin. While TNF-alpha is released from the bronchoalveolar lavage cells of many subjects, in addition, many patients with interstitial lung disease also release spontaneously, large amounts of fibroblast growth factor activity attributable to PDGF and fibronectin.

Studies on carrageenan-induced arthritis in adult rats: presence of nerve growth factor and role of sympathetic innervation

Recent studies effected by our Institute indicate that various forms of human arthritis express both immunohistochemically and biologically active nerve growth factor (NGF) in the synovium. In the present study, we used a model of carrageenan-induced arthritis to further evaluate the effects of joint inflammation on NGF level. These studies showed that experimentally-induced arthritis in rats caused a significant increase in NGF in the perivascular area of the synovium. We also showed that injection into the synovium of purified NGF did not cause inflammation per se and that the destruction of peripheral sympathetic innervation significantly reduced both the inflammation and the level of NGF following carrageenan injection.

Peptide growth factors and their interactions during chondrogenesis

Peptide growth factors have been implicated in three aspects of cartilage growth and metabolism; the induction of mesoderm and differentiation of a cartilaginous skeleton in the early embryo, the growth and differentiation of chondrocytes within the epiphyseal growth plates leading to endochondral calcification, and the processes of articular cartilage damage and repair. Three peptide growth factor classes have been strongly implicated in these processes, the fibroblast growth factor family (FGF), the insulin-like growth factors (IGFs) including insulin, and transforming growth factor-beta (TGF-beta) and related molecules. Each of these peptide groups are expressed in the early embryo. Basic FGF, TGF-beta and the related activin have been shown to induce the appearance of mesoderm from primitive neuroectoderm. TGF-beta and related bone morphometric proteins can induce the differentiation of cartilage from primitive mesenchyme, and together with basic FGF and IGFs promote cartilage growth. Each class of growth factor is expressed within the epiphyseal growth plate where their autocrine/paracrine interactions regulate the rate of chondrocyte proliferation, matrix protein synthesis and terminal differentiation and mineralization. Basic FGF may prove useful in articular cartilage repair, while basic FGF, IGFs and TGF-beta are among a number of growth factors and cytokines that have been implicated in cartilage disease.