Regulation of synovial cell growth. Coexpression of transforming growth factor beta and basic fibroblast growth factor by cultured synovial cells

Gene delivery of TGF-β1 induces arthrofibrosis and chondrometaplasia of synovium in vivo

To understand the cellular and molecular events contributing to arthrofibrosis, we used an adenovirus to deliver and overexpress transforming growth factor-beta 1 (TGF-β1) cDNA (Ad.TGF-β1) in the knee joints of immunocompromised rats. Following delivery, animals were killed periodically, and joint tissues were examined macroscopically and histologically. PCR-array was used to assay alterations in expression patterns of extracellular matrix (ECM)-associated genes. By days 5 and 10, TGF-β1 induced an increase in knee diameter and complete encasement of joints in dense scar-like tissue, locking joints at 90° of flexion. Histologically, massive proliferation of synovial fibroblasts was seen, followed by their differentiation into myofibroblasts. The fibrotic tissue displaced the normal architecture of the joint capsule and fused with articular cartilage. RNA expression profiles showed high levels of transcription of numerous MMPs, matricellular and ECM proteins. By day 30, the phenotype of the fibrotic tissue had undergone chondrometaplasia, indicated by cellular morphology, matrix composition and >100-fold increases in expression of collagen type II and cartilage link protein. Pre-labeling of articular cells by injection with recombinant lentivirus containing eGFP cDNA showed fibrotic/cartilaginous tissues appeared to arise almost entirely from local proliferation and differentiation of resident fibroblasts. Altogether, these results indicate that TGF-β1 is a potent inducer of arthrofibrosis, and illustrate the proliferative potential and plasticity of articular fibroblasts. They suggest the mechanisms causing arthrofibrosis share many aspects with tumorigenesis.

Expression of β-catenin in rheumatoid arthritis fibroblast-like synoviocytes

OBJECTIVE

β-Catenin is the key mediator of the Wnt signal and also a component of E-cadherin complexes at the intercellular adhering junction, which mediates cell-cell adhesion. We hypothesized that β-catenin might be involved in the long-lasting changed phenotype of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) and could play a role in the pathogenesis of RA. In this study we investigated the expression of β-catenin in RA-FLS.

METHODS

Synovial tissues were obtained during joint replacement surgery or arthroscopy from six patients with RA, six patients with osteoarthritis (OA), and six patients with joint trauma (Trauma group). Immunohistochemical analysis of β-catenin was performed in the synovial tissues from the three groups. Synovial tissues from three patients in each group were selected at random for FLS isolation. Expression of β-catenin in FLS from the three groups was evaluated at the protein level by western blotting and at the mRNA level by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Immunohistochemistry revealed that the expression of β-catenin in synovial lining cells of the RA samples was significantly greater than that of the OA or trauma samples (p < 0.01). Western blotting and RT-PCR showed that β-catenin expression was elevated in RA-FLS compared with that in OA-FLS or Trauma-FLS (p < 0.05) at the protein level but no difference was found at the mRNA level.

CONCLUSIONS

Expression of β-catenin is elevated in RA-FLS, not only in vitro but also in vivo. The increase is due to activation of Wnt/β-catenin signalling. Wnt/β-catenin signalling is activated in RA-FLS, and contributes to the stable activation of RA-FLS.

TGF-beta and fibrosis in different organs - molecular pathway imprints

The action of transforming-growth-factor (TGF)-beta following inflammatory responses is characterized by increased production of extracellular matrix (ECM) components, as well as mesenchymal cell proliferation, migration, and accumulation. Thus, TGF-beta is important for the induction of fibrosis often associated with chronic phases of inflammatory diseases. This common feature of TGF-related pathologies is observed in many different organs. Therefore, in addition to the description of the common TGF-beta-pathway, this review focuses on TGF-beta-related pathogenetic effects in different pathologies/organs, i. e., arthritis, diabetic nephropathy, colitis/Crohn's disease, radiation-induced fibrosis, and myocarditis (including their similarities and dissimilarities). However, TGF-beta exhibits both exacerbating and ameliorating features, depending on the phase of disease and the site of action. Due to its central role in severe fibrotic diseases, TGF-beta nevertheless remains an attractive therapeutic target, if targeted locally and during the fibrotic phase of disease.

Increased Expression of Cyclooxygenase-2 (COX-2) in Radiation-Induced Small Bowel Injury in Rats

BACKGROUND

Radiation therapy is a widely used adjuvant therapy for various abdominal and pelvic cancers. On the other hand, it is not a benign treatment modality, as most radiation patients suffer from some kind of radiation enteritis. Currently available treatments are only palliative and no ideal compound has as yet been discovered. The aim of this study was to evaluate cyclooxygenase-2 (COX-2) expression, and to investigate the possible protective effect of the selective COX-2 inhibitor, Rofecoxib, in acute and late stages of radiation-induced intestinal injury in rats.

MATERIALS AND METHODS

Forty-eight male Sprague-Dawley rats were randomly divided into eight groups. After abdominal irradiation of all of the animals except the six in the control group, the expression of the enzyme cyclooxygenase-2 (COX-2) was evaluated in different cell types present in the intestinal wall 2 h post exposure (study day 0) and again on study days 4, 14, and 60. The effects of Rofecoxib on histological damage, intestinal myeloperoxidase (MPO) activity, and malondialdehyde (MDA) levels were also measured.

RESULTS

Expression of COX-2 in vascular endothelial cells was found to be significantly increased on post exposure days 4 and 14 (2.4 and 2.9 stained vessels/high power field [hpf] respectively compared to 1.3 vessels/hpf for controls) (P = 0.002). Expression of COX-2 in fibroblasts increased immediately after irradiation (29 cells/hpf 2 h after irradiation compared to 12 cells/hpf for non-irradiated control animals) and remained high during the entire study period (P < 0.001), whereas there was a peak COX-2 expression (54.9 cells/hpf) on day 14 that was similar to what was observed in endothelial cells. Irradiation of rats significantly increased intestinal epithelial damage, MPO activity, and MDA levels in comparison to the control group in a time-dependent fashion. Treatment with rofecoxib significantly decreased these elevations except on day 4 of the study.

CONCLUSION

The current study suggests that the COX-2 pathway is involved in radiation induced intestinal injury and that targeting COX-2 may be useful in limiting radiation enteritis.

The importance of T cell interactions with macrophages in rheumatoid cytokine production

The analysis of suppression of cytokines in rheumatoid synovial tissue and fluid pioneered the studies of human cytokines in diseased tissue due to the relative ease of staining samples, even at the height of the inflammatory process. These studies led to the study of synovial cytokine regulation, and the identification of TNF as a therapeutic target, which has been amply validated in clinical trials and now routine therapy. The next key question was how is TNF disregulated in synovium. Are there differences between the mechanisms of synovial TNF production compared to the production of protective TNF during an immune response? Are there differences between the induction of the pro-inflammatory TNF and the anti inflammatory IL-10? The analysis of the interaction of the two most abundant synovial cells, T lymphocytes and macrophages has provided interesting clues to new therapeutic approaches based on disrupting T-macrophage interaction.

Regulation of neurokinin-1 receptor messenger RNA expression in synovial fibroblasts of patients with rheumatoid arthritis

We examined whether soluble mediators regulate the expression of tachykinin receptor mRNAs in synovial fibroblasts of patients with rheumatoid arthritis (RA). mRNAs encoding long and short isomers of neurokinin 1 receptor (NK1R), and neurokinin 2 receptor (NK2R) were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) analysis. Level of long, but not the short, of NK1R mRNA was increased by treatment with 10-100 ng/ml basic fibroblast growth factor (bFGF) or 20 ng/ml tumor necrosis factor-alpha (TNF-alpha), but not with 1ng/ml interleukin 1beta (IL-1beta). TNF-alpha upregulated NK2R mRNA as well as long NK1R mRNA whereas bFGF had no effect on NK2R mRNA. Expression of neurokinin 3 receptor (NK3R) mRNA was not observed in RA fibroblasts, and its expression was not induced by bFGF and TNF-alpha. The basal and increased levels of long NK1R mRNA were inhibited by treatment with 20 microM SU5402, an inhibitor of the tyrosine kinase activity of FGF receptor 1 (FGFR1), or 10 ng/ml transforming growth factor-beta1 (TGF-beta1). SU5402 and TGF-beta1 had no effect on the basal level of short NK1R mRNA. Immunocytochemistry revealed the enhancement by bFGF of immunoreactive NK1Rs in the cells at 24 h after treatment. These results suggest that bFGF, TGF-beta1, and TNF-alpha in synovial tissue and fluid play a role in the regulation of long NK1R expression in synovial fibroblasts of RA patients. It appears that the pathway of downregulation by TGF-beta1 is more dominant in the long NK1R mRNA expression than that of upregulation by bFGF or TNF-alpha. Furthermore, the regulation of short NK1R mRNA expression seems to be performed via a different pathway from that of long isomer mRNA.

The relationship between mucosal cyclooxygenase-2 (COX-2) expression and experimental radiation-induced mucositis

Although cycloooxygenase-2 (COX-2) is upregulated by factors associated with oral mucositis, its role in the pathogenesis of mucositis has not been studied. We investigated the kinetics of mucosal COX-2 expression following radiation exposure, and assessed its relationship to the development of oral mucositis in an established animal model using immunohistochemical endpoints. While little or no COX-2 expression was observed in unirradiated mucosa or in tissue taken 2 days after radiation, COX-2 expression was dramatic on days 10 and 16, especially in submucosal fibroblasts and endothelium. The kinetics of COX-2 expression paralleled mucositis severity. A burst of angiogenic activity was seen on day 21 following peak COX-2 expression. The kinetics of COX-2 expression relative to mucositis progression suggests that COX-2 is not a primary driver of radiation injury, but instead plays an amplifying role.

Immunohistochemical study of the proliferation modality of synovium in rat adjuvant arthritis

To investigate the proliferative potencies of the two types of synovial lining cells (types A and B), we used immunohistochemical techniques under light and electron microscopy to survey the complete process of arthritis in a rat model system. Complete Freund's adjuvant (0.1 ml) containing 5 mg of heat-inactivated Mycobacterium butyricum was administered intradermally into the right hind paws of 25 male Sprague-Dawley rats. Five animals were killed at weeks 1, 2, 3, and 4 after the immunological challenge, respectively, and the infrapatellar adipose synovium was removed from each animal. Using proliferative cell nuclear antigen (PCNA) as a cell proliferation marker, we quantified the locations of proliferative cells under light microscopy and then identified the cell type with immunoelectron microscopy. The number of PCNA-positive cells was high in the deep layer at week 2, and most of them were determined to be B cells. At week 3, the number of PCNA-positive cells increased in the superficial layer, and most were identified as A cells. Our results support the idea that cells of the synovial lining proliferate in situ during the course of arthritis.

Pathologic thrombopoiesis of rheumatoid arthritis

Rheumatoid arthritis (RA) is frequently complicated by thrombocytosis correlated with disease activity. The exact pathogenetic mechanism(s) that cause increased platelet counts in RA are still unknown. Recent investigations indicate that proinflammatory pleiotropic cytokines of RA also have megakaryocytopoietic/thrombopoietic properties. Moreover, several lineage-dominant hematopoietic cytokines can also act as acute phase responders and contribute to the inflammation. This review focuses on the current literature and our experience regarding the dual relationships of the pathologic thrombopoiesis of RA. Growth factors contributing to it, namely interleukin (IL)-6, IL-11, stem cell factor, leukemia inhibitory factor, granulocyte colony stimulating factor, thrombopoietin (TPO), and the regulation of megakaryocytopoiesis during the inflammatory cascade are reviewed. Some data indicate that thrombopoietin could contribute to the reactive thrombocytosis of RA. In the non-lineage-specific gp130 cytokine family, IL-6 appears to predominate for the induction of megakaryopoiesis. However, other cytokines and growth factors may also contribute to the pathologic megakaryocytopoiesis of RA. Those pleiotropic mediators seem to act in concert to regulate this enigmatic process. Clarification of the pathobiologic basis of thrombopoiesis in RA may improve understanding of the disease pathogenesis and management of the inflammatory thrombocytosis.

Angiopoietin-1 is expressed in the synovium of patients with rheumatoid arthritis and is induced by tumour necrosis factor alpha

OBJECTIVES

To examine the potential role of the angiogenic growth factor angiopoietin-1 (Ang-1) in inflammatory arthritis.

METHODS

Eighteen synovial tissue samples were obtained from 17 patients with a clinical diagnosis of rheumatoid arthritis (RA) and compared with six synovial tissue samples from six patients with osteoarthritis (OA). Ang-1 expression in synovial tissues was determined by immunohistochemistry and in situ hybridisation. Ang-1 mRNA and protein expression were also examined by northern blot analysis and enzyme linked immunosorbent assay (ELISA) in cultured synovial fibroblasts and human umbilical vein endothelial cells (HUVECs) before and after treatment with tumour necrosis factor (TNF)alpha.

RESULTS

Ang-1 protein expression was detected by immunohistochemistry in 16/18 RA synovial tissue samples. Ang-1 protein was frequently observed in the synovial lining layer and in cells within the sublining synovial tissue, in both perivascular areas and in areas remote from vessels. In contrast, Ang-1 was only weakly detected in these sites in OA samples. Ang-1 mRNA and protein were also expressed in cultured synovial fibroblasts derived from patients with RA. In addition, induction of Ang-1 mRNA and protein was observed by northern blot analysis and ELISA after stimulation of RA synovial fibroblasts, but not HUVECs, with the proinflammatory cytokine TNF alpha.

CONCLUSIONS

Ang-1 mRNA and protein are expressed in the synovium of patients with RA, and are up regulated in synovial fibroblasts by TNF alpha. Ang-1 may therefore be an important regulator of angiogenesis in inflammatory arthritis.

Isolation and characterization of rheumatoid arthritis synovial fibroblasts from primary culture--primary culture cells markedly differ from fourth-passage cells

To reduce culture artifacts by conventional repeated passaging and long-term culture in vitro, the isolation of synovial fibroblasts (SFB) was attempted from rheumatoid arthritis (RA) synovial membranes by trypsin/collagenase digest, short-term in vitro adherence (7 days), and negative isolation using magnetobead-coupled anti-CD14 monoclonal antibodies. This method yielded highly enriched SFB (85% prolyl-4-hydroxylase+/74% Thy-1/CD90+ cells; <2% contaminating macrophages; <1% leukocytes/endothelial cells) that, in comparison with conventional fourth-passage RA-SFB, showed a markedly different phenotype and significantly lower proliferation rates upon stimulation with platelet-derived growth factor and IL-1beta. This isolation method is simple and reliable, and may yield cells with features closer to the in vivo configuration of RA-SFB by avoiding extended in vitro culture.

Potential role ofHOXD9 in synoviocyte proliferation

OBJECTIVE

To investigate the role of HOXD9 in the proliferation activity of cultured synoviocytes as well as the mechanisms that regulate HOXD9 transcription.

METHODS

Synoviocytes from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) were transfected with HOXD9 complementary DNA to establish stable transformants that overexpressed HOXD9. HOXD9 expression was detected by Western blotting with anti-HOXD9 antibody. The growth properties of the transformants were investigated by proliferation and colony formation assays. The expression of basic fibroblast growth factor (bFGF), tumor necrosis factor alpha (TNFalpha), interleukin-1beta, c-Fos, and c-Myc was examined by Western blotting. Transcriptional regulation of HOXD9 was examined by transient cotransfection.

RESULTS

HOXD9 protein was highly expressed in RA synoviocytes, but there was no expression in OA synoviocytes. HOXD9 transfection induced stable HOXD9 protein expression in synoviocytes and showed an increased proliferation rate under both normal and serum-starved conditions, as well as an enhanced capacity to proliferate anchorage independently to form colonies in soft agar cultures, compared with control transfectants. Higher levels of bFGF and c-Fos were detected in HOXD9 transformants than in controls. Transient cotransfection assays of NIH3T3 fibroblasts and synoviocytes showed that HOXD9 activated the luciferase reporter construct containing the highly conserved region (HCR), an autoregulatory element of HOXD9 promoter. This activation was significantly increased by bFGF, suppressed by TNFalpha, and unchanged by transforming growth factor beta in synoviocytes. Human T lymphotropic virus type I tax also activated the luciferase reporter construct containing the HCR and had a synergistic effect with HOXD9 on HCR promoter activation.

CONCLUSION

Our data suggest that HOXD9 plays a potential role in synovial proliferation. In addition, they suggest that the involvement of HOXD9 in the regulation of cellular growth might be mediated, at least in part, by up-regulation of growth-related factors such as bFGF and c-Fos and/or might result from increased transcription activity by its regulators.

The regulation of PGE(2) biosynthesis in MG-63 osteosarcoma cells by IL-1 and FGF is cell density-dependent

We investigated the molecular mechanisms by which treatment of the human osteoblast-like cell line MG-63 with interleukin 1beta (IL-1) and/or fibroblast growth factor 1 (FGF-1) elicited prostaglandin biosynthesis. IL-1 induced a 5-fold increase in PGE(2) production compared to controls. While treatment with FGF-1 alone did not affect PGE(2) biosynthesis, it enhanced the formation of PGE(2) by IL-1 by an additional 3- to 5-fold. IL-1-induced PGE(2) biosynthesis accompanied increases in steady-state levels of mRNAs encoding cPLA(2) (10- to 15-fold) and PGHS-2 (>3-fold) and concomitant increases in cPLA(2) protein (>3-fold) and PGHS-2 protein (>1. 5-fold). FGF-1 treatment did not affect PGHS-2 gene expression, but enhanced the effect of IL-1 on PGHS-2 expression by an additional 2- to 3-fold. FGF-1 alone enhanced cPLA(2) expression (5-fold), and the combined effects of FGF-1 and IL-1 on cPLA(2) expression were additive. There was no measurable effect of either agonist on PGHS-1 expression. We also discovered that induction of PGE(2) biosynthesis in response to IL-1 or IL-1/FGF-1 was affected by the density of MG-63 cells in culture. Subconfluent cultures displayed a 3- to 10-fold greater response to IL-1 or IL-1/FGF-1 than confluent cultures. The decreased PGE(2) induction by IL-1 in confluent cultures was associated with reduced IL-1 receptor expression. We conclude that the signaling pathways resulting in PGE(2) biosynthesis in response to proinflammatory agents like IL-1 are subject to complex regulation by additional soluble mediators as well as cell-cell or cell-extracellular matrix interactions.

Chondroprogenitor cells of synovial tissue

OBJECTIVE

To assess the chondrogenic potential of cells within the synovium.

METHODS

Explants of synovium taken from various sites in the joint were embedded in agarose and cultured with transforming growth factor beta1 (TGFbeta1) to assess their chondrogenic potential. Isolated synovial cells were also tested for their chondrogenic potential by culturing them as aggregates in a chemically defined medium with TGFbeta1. Cartilage formation was determined with histologic staining and immunohistochemistry. The osteochondral potential of the isolated cells was also assessed after subcutaneous implantation of the cells, loaded into porous calcium phosphate ceramic cubes, in athymic mice.

RESULTS

A total of 48 synovial explants were cultured in agarose with TGFbeta1. The formation of cartilage was observed in the outer region of 21 explants, and type II collagen was localized in that region by immunohistochemistry. A larger percentage of TGFbeta1+ explants from the inner synovium sites formed cartilage compared with those from the outer synovium sites. Chondrogenesis occurred in aggregates incubated with TGFbeta1 as early as day 7, and by day 14, all TGFbeta1+ aggregates demonstrated chondrogenesis. In contrast with the results of the in vitro aggregate assay for chondrogenesis, no formation of cartilage or bone was evident in any section containing synovial cell-loaded ceramic cubes that were harvested at either 3 or 6 weeks after implantation subcutaneously in athymic mice.

CONCLUSION

Synovial explants and isolated synovial cells will undergo chondrogenesis when cultured in the presence of TGFbeta1. The data indicate a possible synovial origin for the chondrocytic cells found in rheumatoid pannus. Furthermore, these data are consistent with the clinical findings of synovial chondrogenesis leading to synovial chondromatosis.

Tyrosine phosphorylated proteins in synovial cells of rheumatoid arthritis

Two of the key events in the pathogenesis of rheumatoid arthritis are the synovial cell proliferation and lymphocyte infiltration into the synovium. The resulting synovitis is longlasting and leads to destructive arthritis, which is a hallmark of rheumatoid arthritis. Accumulating evidence suggests that one of the key biochemical events in the altered cell function of RA is phosphorylation of the tyrosine residues of proteins. In this paper we review the cellular components participating in the chronic inflammation of RA joints. We present the results of analyzing tyrosine phosphorylated proteins of synovial cells from RA patients and discuss a possible pathogenic role of non-receptor tyrosine kinase in RA.

Role of pro-inflammatory cytokines in rheumatoid arthritis

Rheumatoid arthritis (RA) is well known to be a chronic autoimmune/inflammatory disease which leads to progressive joint damage and destruction. Less well known is the fact that in severe cases of RA, with extra-articular manifestations and multiple joint involvement, there is also a significant reduction in life expectancy [28]. Hence the need for new therapeutic agents. With the cloning of cDNAs encoding cytokines in the early to mid 1980s, it became possible to use new assays to evaluate cytokine expression in the local site of autoimmunity, the rheumatoid synovium. There were two goals. First would understanding cytokine expression help us understand the pathogenesis of RA? Secondly, would it be possible to learn enough about the cytokine network to establish possible therapeutic targets? While a complete understanding of either of these questions remains elusive, here we review the state of knowledge in early 1998, which shows that much progress has been made and that these goals have been partly reached. The clinical benefits of this knowledge are documented elsewhere in this compilation, as is the role of chemokines, anti-inflammatory cytokines and the cytokines involved in neovascularisation.

Changes in third carpal bone articular cartilage after synovectomy in normal and inflamed joints

OBJECTIVE

To determine if arthroscopic synovectomy in normal and inflamed joints had temporal or site-related effects on articular cartilage.

STUDY DESIGN

Alterations in equine third carpal bone articular cartilage were studied at two time periods: groups 1 and 2 (6 weeks) and groups 3 and 4 (2 weeks) after synovectomy in normal (groups 2 and 4) and inflamed carpi (groups 1 and 3).

ANIMAL POPULATION

16 carpi from eight horses.

METHODS

Biochemical and biomechanical properties of dorsal and palmar articular cartilage were determined by radioloabeling, proteoglycan (PG) extraction, chromatography, electrophoresis, and indentation testing.

RESULTS

Synovectomy in inflamed joints produced the greatest concentration of newly synthesized PG in articular cartilage by 2 weeks. Synovectomy in normal joints produced significantly greater newly synthesized PG in articular cartilage by 6 weeks. Dorsal sites had greater newly synthesized and endogenous PG in some groups. Chromatographic profiles of newly synthesized PG demonstrated early and late PG peaks. Electrophoresis of late PG peak showed a toluidine blue-positive band that comigrated with human A1D1 PG monomer in the two groups with the most newly synthesized PG> This band was reactive with monoclonal antibody 1C6 specific for the hyaluronic acid-binding region of aggrecan. For the material properties evaluated, only Poisson's ratio was significantly decreased between groups as a function of time (6 weeks < 2 weeks). and this was most pronounced in the thicker dorsal sites.

CONCLUSIONS

Synovectomy in inflamed joints produced site-specific, significantly greater responses in articular cartilage as compared with synovectomy in normal joints.

CLINICAL RELEVANCE

Synovectomy may not be beneficial to the articular cartilage in inflamed joints.

Cytokines in rheumatoid arthritis. Potential targets for pharmacological intervention

The ingress of inflammatory leucocytes into the synovium is a crucial step in the pathogenesis of rheumatoid arthritis (RA). Cytokines are mediators involved in the inflammatory events, adhesive mechanisms, angiogenesis and osteopenia associated with RA. Pro- and anti-inflammatory cytokines, growth factors and chemokines all have an important role in these processes. Because the efficacy of currently used antirheumatic therapy is often limited, there is a need for more specific intervention strategies. Anticytokine therapy may include the use of monoclonal antibodies, antagonistic cytokines, soluble cytokine receptors, cytokine receptor antagonists, somatic gene transfer or other approaches. Hopefully, the study of cytokines and their interactions will lead to the development of new immunomodulatory strategies that will benefit patients with RA.

Inhibition of rheumatoid synovial fibroblast proliferation by antisense oligonucleotides targeting proliferating cell nuclear antigen messenger RNA

OBJECTIVE

To evaluate the feasibility of antisense oligonucleotides as therapeutic agents to inhibit synovial cell growth in rheumatoid arthritis (RA).

METHODS

Fibroblast-like cells established from RA synovium were stimulated with interleukin-1beta (IL-1beta) and treated with antisense or sense oligonucleotides targeting proliferating cell nuclear antigen (PCNA) messenger RNA (mRNA). Proliferation of these cells was determined by 3H-thymidine incorporation. Effects of antisense oligonucleotides on the expression of mRNA and protein were evaluated by reverse transcriptase-polymerase chain reaction and immunohistochemical staining, respectively.

RESULTS

Antisense oligonucleotides targeting PCNA inhibited IL-1-stimulated fibroblast proliferation, whereas sense oligonucleotides had no effect. Both mRNA and protein levels of PCNA were suppressed in the cells treated with antisense oligonucleotides, indicating that the antiproliferative effect was occurring through an antisense mechanism.

CONCLUSION

These results suggest that antisense strategies designed to suppress PCNA expression have potential use as therapeutic agents for RA.

Transforming growth factor beta 1 and interleukin 4 induced alpha smooth muscle actin expression and myofibroblast-like differentiation in human synovial fibroblasts in vitro: modulation by basic fibroblast growth factor

OBJECTIVE

To discover if alpha smooth muscle actin expression and myofibroblastic differentiation are induced in synovial fibroblasts by cytokines found in the inflamed RA joint.

METHODS

Immunofluorescent microscopy and western blotting were used to examine different cultures of human synovial fibroblasts for expression of alpha actin in the presence of the cytokines transforming growth factor beta (TGF beta 1), interleukin 1 alpha (IL1 alpha), IL4, IL6, tumour necrosis factor alpha (TNF alpha), and basic fibroblast growth factor (FGF).

RESULTS

A small but significant population of cells (14.4 +/- 12.9%) expressed alpha actin under standard culture conditions. Upon treatment with TGF beta 1 there was a pronounced increase in the number of cells expressing alpha actin (68.1 +/- 5.49%), accompanied by a change in morphology to a myofibroblast-like phenotype. Other cytokines found within the inflamed joint such as IL1, TNF alpha, IL6, and basic FGF failed to induce alpha actin expression. However, IL4, which is normally absent or only present at low concentrations in the RA joint had a similar effect to TGF beta 1. It was also found that basic FGF inhibited the induction of alpha actin expression by TGF beta 1 and IL4.

CONCLUSION

In the presence of TGF beta 1 or IL4, fibroblasts derived from synovial tissue or synovial fluid are induced to differentiate into myofibroblast-like cells containing the alpha smooth muscle form of actin. This differentiation is inhibited by basic FGF. It is suggested that the balance between these particular cytokines may be important in the modulation of fibroblast behaviour, which could have significant effects on joint repair mechanisms and the generation of fibrous tissue within the rheumatoid joint.

Increased expression of integrins on fibroblast-like synoviocytes from rheumatoid arthritis in vitro correlates with enhanced binding to extracellular matrix proteins

OBJECTIVE

To compare in vitro expression of beta 1, beta 3, and beta 4 integrins in normal fibroblast-like synoviocytes (FBS) and in FBS from rheumatoid arthritis (RA) synovium and to investigate the adhesion of normal FBS and RA-FBS to the integrin binding extracellular matrix (ECM) proteins: collagen type IV, fibronectin, laminin, and tenascin.

METHODS

Expression of integrin receptors of cultured FBS was detected by flow cytometry. Attachment of FBS to ECM proteins was quantified by adhesion assays. Inhibition studies were performed using monoclonal antibodies to the integrin subunits.

RESULTS

Compared with normal FBS, RA-FBS showed increased expression of alpha 1 to alpha 6, beta 1, and beta 4 integrin subunits and enhanced binding of ECM proteins. Binding to ECM proteins was partly or completely blocked by an anti-beta 1 integrin antibody and antibodies to alpha 3, alpha 5, and alpha 6 integrin subunits. The blocking efficiency was significantly (P < 0.05) higher in RA-FBS than in normal FBS.

CONCLUSIONS

The enhanced expression of the beta 1 integrin receptors on cultured RA-FBS correlated with increased attachment to ECM proteins. Adhesion of normal and RA-FBS to ECM proteins is mediated through beta 1 integrin receptors. Therefore, the tight binding of rheumatoid FBS to the matrix via beta 1 integrins might play a role in ECM remodelling in the rheumatoid process in vivo.

Repair of partial-thickness defects in articular cartilage: cell recruitment from the synovial membrane

Partial-thickness defects evolving in mature articular cartilage do not heal spontaneously. This type of defect was created in the articular cartilage of adult rabbits and Yucatan minipigs, and the effects of chondroitinase ABC or trypsin, fibrin clots, and mitogenic growth factors on the healing process were examined histologically at intervals ranging from one to forty-eight weeks. The effect of chondroitinase ABC or trypsin was examined initially. Articular cartilage contains macromolecules, including proteoglycans, which render the surfaces of this tissue, and of partial-thickness defects within it, antiadhesive. Chondroitinase ABC digests the glycosaminoglycan chains of cartilage proteoglycans, and trypsin degrades their core proteins. To test the hypothesis that mesenchymal cells may be prevented from adhering to and migrating over the surfaces of partial-thickness defects by proteoglycans, we removed a superficial layer of these macromolecules from the surface of the defect with use of one of these enzymes. The treatment evoked an increase in the coverage of the defect surface with mesenchymal cells; when combined with the local application of a mitogenic growth factor (basic fibroblast growth factor, transforming growth factor-beta 1, epidermal growth factor, insulin-like growth factor-1, or growth hormone), the coverage was more extensive but mesenchymal cells did not extend into and completely fill the volume of the defect. When the surface of the defect was treated with chondroitinase ABC and the cavity of the defect was filled with a fibrin clot to furnish a matrix or scaffolding for the migration of cells therein, there was migration and proliferation of cells throughout the volume of the defect but at a low population density. Mesenchymal cells remodeled the deposited fibrin matrix, which was replaced by a loose fibrous connective tissue. When defects that had been treated with chondroitinase ABC were filled with a fibrin clot containing a mitogenic growth factor, mesenchymal cells filled the entire cavity of the defect, and the density of the cells was greatly increased, particularly when transforming growth factor-beta 1 was used. Histological studies revealed a continuous layer of mesenchymal cells extending from the synovial membrane across the superficial tangential zone of normal articular cartilage into the defect, indicating that the cells that were recruited for the repair process were of synovial origin. At forty-eight weeks, the entire cavity of the defect remained filled with a fibrous connective tissue.

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.

Transforming growth factor beta 1, a major stimulator of hyaluronan synthesis in human synovial lining cells

OBJECTIVE

To investigate the role of cytokines and growth factors in the regulation of hyaluronan synthesis in human synovial lining cells.

METHODS

Synovial lining cells were obtained from human knee joints, isolated by the explant method, and characterized by immunocytochemistry using monoclonal antibodies against monocyte/macrophage markers as well as antibodies against hyaluronan synthase. After stimulation by cytokines and growth factors, hyaluronan was measured by radiometric assay. The molecular weight distribution of the hyaluronan synthesized was determined by high-performance gel-permeation liquid chromatography. To test the effect of oxygen-derived free radicals, the concentration and molecular weight distribution of hyaluronan were determined in the presence and absence of catalase and superoxide dismutase.

RESULTS

Hyaluronan synthesis was stimulated in synovial lining cells by transforming growth factor beta 1 (TGF beta 1), interleukin-1 beta (IL-1 beta), and to a lesser extent by tumor necrosis factor alpha (TNF alpha). Analysis of the molecular weight distribution of hyaluronan after stimulation of synovial lining cells with TGF beta 1, IL-1 beta, and TNF alpha indicated that hyaluronan is synthesized in a high molecular weight form and might be degraded in the course of inflammatory processes by oxygen-derived free radicals.

CONCLUSION

Our findings suggest that TGF beta 1 is a major stimulator of hyaluronan synthesis in human synovial lining cells and might be involved in the pathogenic mechanisms of joint swelling in inflammatory and degenerative joint diseases.

Synoviocytes in chronic synovitis in situ and cytokine stimulated synovial cells in vitro neo-express alpha 1, alpha 3 and alpha 5 chains of beta 1 integrins

The expression of the beta 1 integrins was examined immunohistochemically in synoviocytes from normal synovitis membrane and from chronic synovitis of different aetiology and intensity. Normal synoviocytes were alpha 6 beta 1-positive but lacked alpha 1 through alpha 5. In mild inflammation type A synoviocytes neo-expressed alpha 1, alpha 3, and alpha 5 chains. In severe inflammation both type A and B synoviocytes expressed alpha 3, alpha 4, alpha 5, and alpha 6 chains. The effects of inflammatory cytokines, as single agents or in combination, on the beta 1 integrin expression in cultured normal synoviocytes was determined by immunocytochemistry and flow cytometry. The alpha 1 chain, while absent in unstimulated synoviocytes, was induced by interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma). This effect was enhanced by combining IL-1 beta and TNF-alpha. Expression of the alpha 3 chain was up-regulated by IL-1 beta and, more intensely, by IFN-gamma. Transforming growth factor beta (TGF-beta) inhibited the up-regulating effect of IL-1 beta and antagonized the effect of IFN-gamma on alpha 3 chain expression. Expression of the alpha 5 chain was up-regulated significantly by co-stimulation through IL-1 beta together with TGF-beta or TNF-alpha. Thus, the beta 1 integrin profile of cytokine activated synoviocytes in vitro resembled that of synoviocytes in synovitis in situ. These data suggest that IL-1 beta, TNF-alpha, IFN-gamma, and TGF-beta are likely to be among the effectors regulating beta 1 integrin expression in synoviocytes in vivo.

Inhibition of neovascularization in vivo by gold compounds

As mononuclear cell infiltration and growth of pannus critically depend on synovial neovascularization in rheumatoid arthritis (RA), inhibition of the synovial blood vessels would have the potential to reduce rheumatoid inflammation. In this investigation, we studied the effect of gold sodium thiomalate (GST) and auranofin (AUR) on neovascularization in vivo by using a micropocket technique. Both GST and AUR suppressed rabbit corneal neovascularization in a dose-dependent fashion. Significant inhibition was observed by 3 mg/kg GST and 1 mg/kg AUR injected intravenously every other day. These injections maintained serum gold concentrations at the level of 2-5 micrograms/ml and less than 2 micrograms/ml in GST- and AUR-injected rabbits, respectively. These are concentrations attained in the serum or synovium of rheumatoid patients treated by gold compounds. Similar inhibition was observed by both intramuscular administration of GST and oral administration of AUR. In contrast, no inhibition was observed when non-steroidal anti-inflammatory drugs (NSAIDs; 20 mg/kg acetylsalicylic acid, 10 mg/kg ibuprofen and 10 mg/kg indomethacin) were injected intravenously on a daily basis. These results suggested that gold compounds have an antiangiogenic effect in vivo. The inhibition of neovascularization by gold compounds suggested that they may suppress rheumatoid synovitis by reducing the number of small blood vessels required for mononuclear cell infiltration and synovial tissue proliferation.

Expression of basic fibroblast growth factor in synovial tissues from patients with rheumatoid arthritis: detection by immunohistological staining and in situ hybridisation

OBJECTIVE

The distribution and production of basic fibroblast growth factor (bFGF) was examined on the synovium from patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

METHODS

The localisation of bFGF was determined by an immunohistochemical staining procedure using anti-bFGF monoclonal antibody. The expression of bFGF mRNA was detected by nonradioactive in situ hybridisation using bFGF antisense oligo DNA.

RESULTS

The bFGF was found in the synovial lining cell, sublining stromal fibroblast-like cells, and vascular endothelial cells from patients with RA and OA. Little or no bFGF was found in non-inflamed synovium. Immunostaining of bFGF in the synovial cells was more extensive and intense in synovium of patients with RA than that of patients with OA. The nuclei of the synovial lining cell layer were also immunostained. These nuclear staining were more intense in the lining cell layer from RA patients with moderate or severe proliferation of synovial cells than in RA patients with mild proliferation. The bFGF mRNA was also detected in the synovial lining cell layer of the inflamed synovium.

CONCLUSION

The synovial lining cells produced bFGF. The proliferation of synovial cells in the inflamed joints may be the results of stimulation by the bFGF in autocrine manner.