Constitutive upregulation of the transforming growth factor-beta pathway in rheumatoid arthritis synovial fibroblasts

Transcription factor ICBP90 regulates the MIF promoter and immune susceptibility locus

The immunoregulatory cytokine macrophage migration inhibitory factor (MIF) is encoded in a functionally polymorphic locus that is linked to the susceptibility of autoimmune and infectious diseases. The MIF promoter contains a 4-nucleotide microsatellite polymorphism (-794 CATT) that repeats 5 to 8 times in the locus, with greater numbers of repeats associated with higher mRNA levels. Because there is no information about the transcriptional regulation of these common alleles, we used oligonucleotide affinity chromatography and liquid chromatography-mass spectrometry to identify nuclear proteins that interact with the -794 CATT5-8 site. An analysis of monocyte nuclear lysates revealed that the transcription factor ICBP90 (also known as UHRF1) is the major protein interacting with the MIF microsatellite. We found that ICBP90 is essential for MIF transcription from monocytes/macrophages, B and T lymphocytes, and synovial fibroblasts, and TLR-induced MIF transcription is regulated in an ICBP90- and -794 CATT5-8 length-dependent manner. Whole-genome transcription analysis of ICBP90 shRNA-treated rheumatoid synoviocytes uncovered a subset of proinflammatory and immune response genes that overlapped with those regulated by MIF shRNA. In addition, the expression levels of ICBP90 and MIF were correlated in joint synovia from patients with rheumatoid arthritis. These findings identify ICBP90 as a key regulator of MIF transcription and provide functional insight into the regulation of the polymorphic MIF locus.

Bioinformatics-Based Identification of MicroRNA-Regulated and Rheumatoid Arthritis-Associated Genes

MicroRNAs (miRNAs) act as epigenetic markers and regulate the expression of their target genes, including those characterized as regulators in autoimmune diseases. Rheumatoid arthritis (RA) is one of the most common autoimmune diseases. The potential roles of miRNA-regulated genes in RA pathogenesis have greatly aroused the interest of clinicians and researchers in recent years. In the current study, RA-related miRNAs records were obtained from PubMed through conditional literature retrieval. After analyzing the selected records, miRNA targeted genes were predicted. We identified 14 RA-associated miRNAs, and their sub-analysis in 5 microarray or RNA sequencing (RNA-seq) datasets was performed. The microarray and RNA-seq data of RA were also downloaded from NCBI Gene Expression Omnibus (GEO) and Sequence Read Archive (SRA), analyzed, and annotated. Using a bioinformatics approach, we identified a series of differentially expressed genes (DEGs) by comparing studies on RA and the controls. The RA-related gene expression profile was thus obtained and the expression of miRNA-regulated genes was analyzed. After functional annotation analysis, we found GO molecular function (MF) terms significantly enriched in calcium ion binding (GO: 0005509). Moreover, some novel dysregulated target genes were identified in RA through integrated analysis of miRNA/mRNA expression. The result revealed that the expression of a number of genes, including ROR2, ABI3BP, SMOC2, etc., was not only affected by dysregulated miRNAs, but also altered in RA. Our findings indicate that there is a close association between negatively correlated mRNA/miRNA pairs and RA. These findings may be applied to identify genetic markers for RA diagnosis and treatment in the future.

Potential involvement of IL-9 and Th9 cells in the pathogenesis of rheumatoid arthritis

OBJECTIVE

IL-9 has been shown to be upregulated before the clinical onset of articular disease in RA. The exact role of IL-9 and Th9 cells in RA, however, has not yet been adequately studied. The aim of this study was to evaluate the expression of IL-9 and IL-9-expressing cells in RA patients.

METHODS

IL-9, IL-9R, PU.1, IL-9, thymic stromal lymphopoietin (TSLP), IL-4 and TGF-β expression was assessed by real-time-PCR in the synovial tissues of RA and OA patients. IL-9, IL-9R, IL-4, TSLP and TGF-β were also investigated by immunohistochemistry. Peripheral CD4(+) T cell subsets were studied by flow cytometry analysis before and after incubation with citrullinated peptides.

RESULTS

IL-9 was overexpressed in RA synovial tissues and correlated with the degree of histological organization of B and T cells in ectopic lymphoid structures. The majority of IL-9-producing cells were identified as CD3(+) cells. Increased mRNA and protein expression of IL-9R, IL-4, TSLP and TGF-β was also observed in RA synovial tissue. Blood peripheral Th9 cells were expanded by citrullinated peptides.

CONCLUSION

These results indicate that Th9 cells and IL-9 were frequently detected in peripheral blood mononuclear cells and synovia of RA patients. A possible pathogenic role for Th9 in RA is discussed.

Genetic Basis of Common Human Disease: Insight into the Role of Missense SNPs from Genome-Wide Association Studies

Recent genome-wide association studies (GWAS) have led to the reliable identification of single nucleotide polymorphisms (SNPs) at a number of loci associated with increased risk of specific common human diseases. Each such locus implicates multiple possible candidate SNPs for involvement in disease mechanism. A variety of mechanisms may link the presence of an SNP to altered in vivo gene product function and hence contribute to disease risk. Here, we report an analysis of the role of one of these mechanisms, missense SNPs (msSNPs) in proteins in seven complex trait diseases. Linkage disequilibrium information was used to identify possible candidate msSNPs associated with increased disease risk at each of 356 loci for the seven diseases. Two computational methods were used to estimate which of these SNPs has a significant impact on in vivo protein function. 69% of the loci have at least one candidate msSNP and 33% have at least one predicted high-impact msSNP. In some cases, these SNPs are in well-established disease-related proteins, such as MST1 (macrophage stimulating 1) for Crohn's disease. In others, they are in proteins identified by GWAS as likely candidates for disease relevance, but previously without known mechanism, such as ADAMTS13 (ADAM metallopeptidase with thrombospondin type 1 motif, 13) for coronary artery disease. In still other cases, the missense SNPs are in proteins not previously suggested as disease candidates, such as TUBB1 (tubulin, beta 1, class VI) for hypertension. Together, these data support a substantial role for this class of SNPs in susceptibility to common human disease.

Effect of MTHFR, TGFβ1, and TNFB polymorphisms on osteoporosis in rheumatoid arthritis patients

Diseases of the immune and the skeletal systems should be studied together for the deep interaction between them. Many studies consider osteoporosis (OP) as a risk factor for the prediction of disease progression in rheumatoid arthritis (RA). The aim of this research is to study the effect of four single nucleotide polymorphisms (SNPs) on RA patients with and without OP. The examined SNPs (MTHFR (C677T, and A1298C), TGFβ1 (T869C), and TNFB (A252G)) were tested by genotyping 17 RA patients with OP and 72 RA patients without OP. Associations were tested using four models (multiplicative, dominant, recessive, and co-dominant). The studied SNPs were not significantly associated with the risk of OP in RA. MTHFR, TGFβ1, and TNFB polymorphisms don't appear to be clinically useful genetic markers for predicting RA severity in Egyptian women population.

The immune suppressive function of transforming growth factor-β (TGF-β) in human diseases

Transforming growth factor-β (TGF-β) functions as an immune suppressor by influencing immune cells' development, differentiation, tolerance induction and homeostasis. In human diseases, TGF-β has been revealed as an essential regulator of both innate and adaptive functions in autoimmune diseases. Furthermore, it plays a significant role in cancer by inhibiting immunosurveillance in the tumor-bearing host. A variety of TGF-β neutralizing anti-cancer therapies have been investigated based on the role of TGF-β in immunosuppression. New studies are focusing on combining TGF-β blockade with tumor vaccinations and immunogene therapies.

TGFβ responsive tyrosine phosphatase promotes rheumatoid synovial fibroblast invasiveness

OBJECTIVE

In rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) that line joint synovial membranes aggressively invade the extracellular matrix, destroying cartilage and bone. As signal transduction in FLS is mediated through multiple pathways involving protein tyrosine phosphorylation, we sought to identify protein tyrosine phosphatases (PTPs) regulating the invasiveness of RA FLS. We describe that the transmembrane receptor PTPκ (RPTPκ), encoded by the transforming growth factor (TGF) β-target gene, PTPRK, promotes RA FLS invasiveness.

METHODS

Gene expression was quantified by quantitative PCR. PTP knockdown was achieved using antisense oligonucleotides. FLS invasion and migration were assessed in transwell or spot assays. FLS spreading was assessed by immunofluorescence microscopy. Activation of signalling pathways was analysed by Western blotting of FLS lysates using phosphospecific antibodies. In vivo FLS invasiveness was assessed by intradermal implantation of FLS into nude mice. The RPTPκ substrate was identified by pull-down assays.

RESULTS

PTPRK expression was higher in FLS from patients with RA versus patients with osteoarthritis, resulting from increased TGFB1 expression in RA FLS. RPTPκ knockdown impaired RA FLS spreading, migration, invasiveness and responsiveness to platelet-derived growth factor, tumour necrosis factor and interleukin 1 stimulation. Furthermore, RPTPκ deficiency impaired the in vivo invasiveness of RA FLS. Molecular analysis revealed that RPTPκ promoted RA FLS migration by dephosphorylation of the inhibitory residue Y527 of SRC.

CONCLUSIONS

By regulating phosphorylation of SRC, RPTPκ promotes the pathogenic action of RA FLS, mediating cross-activation of growth factor and inflammatory cytokine signalling by TGFβ in RA FLS.

The role of transforming growth factor β signaling in fibroblast-like synoviocytes from patients with oligoarticular juvenile idiopathic arthritis: dysregulation of transforming growth factor β signaling, including overexpression of bone morphogenetic protein 4, may lead to a chondrocyte phenotype and may contribute to bony hypertrophy

OBJECTIVE

This study was designed to investigate the pathogenic contributions of fibroblast-like synoviocytes (FLS) to juvenile idiopathic arthritis (JIA) by identifying pathways with dysregulated gene expression in FLS from patients with oligoarticular JIA.

METHODS

FLS were derived from synovial fluid obtained by arthrocentesis from patients with JIA undergoing intraarticular steroid injections and from orthopedic control patients. Gene expression profiles of the JIA and control FLS were obtained using the Affymetrix platform, with application of Ingenuity Pathway Analysis and Gene Set Enrichment Analysis software to define gene sets in dysregulated pathways and networks of potential pathologic relevance in this disease. Biologically relevant differentially expressed genes were confirmed by RNA and protein analysis.

RESULTS

Exploration of global gene expression profiles of the JIA FLS revealed important dysregulated pathways, including the transforming growth factor β (TGFβ) signaling, as well as endochondral bone formation, cartilage formation, and β-catenin networks. Importantly, bone morphogenetic protein 4 (BMP-4) was significantly overexpressed in the JIA FLS. FLS from patients with oligoarticular JIA exhibit a chondrocyte phenotype, as evidenced by expression of type II collagen and aggrecan.

CONCLUSION

Dysregulation of the pathways involved in the pathogenesis of oligoarticular JIA were revealed through gene expression profiling. JIA FLS displayed dysregulated TGFβ signaling and exhibited a hypertrophic chondrocyte phenotype. These characteristics, along with contributions from the β-catenin network may have implications for endochondral bone formation and local growth disturbances in oligoarticular JIA. Overexpression of BMP-4 in FLS from patients with oligoarticular JIA in particular may play an important role in disease pathogenesis, with a direct effect on functional outcome and with implications for future treatment.

Mesenchymal stem cells, autoimmunity and rheumatoid arthritis

The vast majority of literature pertaining to mesenchymal stem cells (MSC) immunomodulation has focussed on bone marrow-derived MSC that are systemically infused to alleviate inflammatory conditions. Rheumatoid arthritis (RA) is the commonest autoimmune joint disease that has witnessed significant therapeutic advances in the past decade, but remains stubbornly difficult to treat in a subset of cases. Pre-clinical research has demonstrated that bone marrow, adipose, synovial and umbilical cord-derived MSC all suppress the functions of different immune cells thus raising the possibility of new therapies for autoimmune diseases including RA. Indeed, preliminary evidence for MSC efficacy has been reported in some cases of RA and systemic lupus erythromatosis. The potential use of bone marrow-MSC (BM-MSC) for RA therapy is emerging but the use of synovial MSC (S-MSC) to suppress the exaggerated immune response within the inflamed joints remains rudimentary. Synovial fibroblasts that are likely derived from S-MSCs, also give rise to a cell-cultured progeny termed fibroblast-like synoviocytes (FLS), which are key players in the perpetuation of joint inflammation and destruction. A better understanding of the link between these cells and their biology could be a key to developing novel MSC-based strategies for therapy. The review briefly focuses on BM-MSC and gives particular attention to joint niche synovial MSC and FLS with respect to immunoregulatory potential therapy roles.

Analysis of differentially expressed genes between rheumatoid arthritis and osteoarthritis based on the gene co-expression network

The aim of the current study was to investigate disease-associated genes and related molecular mechanisms of osteoarthritis (OA) and rheumatoid arthritis (RA). Using GSE7669 datasets downloaded from Gene Expression Omnibus databases, the differentially expressed genes (DEGs) between RA and OA synovial fibroblasts (SFBs) (n=6 each) were screened. DEG-associated co-expression and topological properties were analyzed to determine the rank of disease-associated genes. Specifically, the fold change of differentially expressed genes, the clustering coefficient and the degree of differential gene co-expression were integrated to determine the disease-associated gene ranking. The underlying molecular mechanisms of these crucial disease-associated genes were investigated by gene ontology (GO) enrichment analysis. A total of 1313 DEGs, including 1068 upregulated genes and 245 downregulated genes were observed. The top 20 disease-associated genes were identified, including proteoglycan 4, inhibin β B, carboxypeptidase M, alcohol dehydrogenase 1C and integrin β2. The major GO biological processes of these top 20 disease-associated genes were highly involved in the immune system, such as responses to stimuli, immune responses and inflammatory responses. This large-scale gene expression study observed disease-associated genes and their associated GO function in RA and OA, which may provide opportunities for biomarker development and novel insights into the molecular mechanisms of these two diseases.

Higher expression of latency-associated peptide on the surface of peripheral blood monocytes in patients with rheumatoid arthritis may be protective against articular erosions

Latency-associated peptide (LAP) forms small latent complexes with transforming growth factor beta 1 (TGF-β1). TGF-β-LAP complexes can be detected on the surfaces of immune cells and have been recently shown to play a role in immune regulation through TGF-β1-mediated functions. A study was undertaken to investigate the correlation of LAP expression on the surface of immune cells and presence of articular erosions in patients with rheumatoid arthritis (RA). Venous blood was obtained from patients with severe RA as well as from healthy control subjects. Surface expression of LAP on peripheral blood mononuclear cells was analyzed by flow cytometry, measured as flow cytometric intensity separately on CD14(+) and CD14(-) cells, and compared between RA patients and healthy subjects. Patients with RA demonstrated higher surface expression of LAP on both CD14(+) and CD14(-) mononuclear cells than healthy individuals. Patients with erosive RA had significantly reduced intensity of anti-LAP staining on the CD14(+) cells when compared to RA patients without erosions (p = 0.01). The intensity of anti-LAP staining on CD14(-) cells was not different between groups of RA patients. Higher expression of LAP on the surface of the cells of monocyte lineage may be protective of formation of articular erosions in RA. Further studies are needed to elaborate the mechanism of this phenomenon.

Xylopia aethiopica (Annonaceae) fruit extract suppresses Freund's adjuvant-induced arthritis in Sprague-Dawley rats

ETHNOPHARMACOLOGICAL RELEVANCE

Xylopia aethiopica is used in a decoction of the dried fruit to treat bronchitis, asthma, arthritis, rheumatism, headache, neuralgia and colic pain. The aim of the study is to evaluate the anti-arthritic effects of a 70% aqueous ethanol extract of the fruit of Xylopia aethiopica in a chronic inflammatory model.

MATERIALS AND METHODS

Adjuvant arthritis was induced in Sprague-Dawley rats by intraplantar injection of Complete Freund's adjuvant into the right hind paw. Foot volume was measured by water displacement plethysmometry. The oedema component of inflammation was evaluated as the percentage change in paw swelling and the total oedema induced calculated as area under the time course curves. In addition to X-ray radiography, histopathology of ankle joints supported by haematological analysis was used to assess the anti-arthritic action of the extract of Xylopia aethiopica (XAE).

RESULTS

Xylopia aethiopica extract (100, 300 and 600 mg kg(-1)) modified the time course curve significantly reducing hind paw oedema in the ipsilateral paw at all dose levels when administered both prophylactically and therapeutically. In addition XAE significantly suppressed the systemic spread of the arthritis from the ipsilateral to the contralateral limbs. The radiological pictures of the joints particularly metatarsal, phalanges and the ankle joint space of rats in the XAE-treated group showed protective effect against adjuvant-induced arthritis while histopathology revealed significant reduction in mononuclear infiltration, pannus formation and bone erosion. The haematological analysis in the test animals revealed significant improvement relative to the CFA model group.

CONCLUSION

Xylopia aethiopica XAE suppresses joint inflammation and destruction in arthritic rats.

Understanding the origin, activation and regulation of matrix-producing myofibroblasts for treatment of fibrotic disease

Fibrosis and scar formation results from chronic progressive injury in virtually every tissue and affects a growing number of people around the world. Myofibroblasts drive fibrosis, and recent work has demonstrated that mesenchymal cells, including pericytes and perivascular fibroblasts, are their main progenitors. Understanding the cellular mechanisms of pericyte/fibroblast-to-myofibroblast transition, myofibroblast proliferation and the key signalling pathways that regulate these processes is essential to develop novel targeted therapeutics for the growing patient population suffering from solid organ fibrosis. In this review, we summarize the current knowledge about different progenitor cells of myofibroblasts, discuss major pathways that regulate their transdifferentiation and discuss the current status of novel targeted anti-fibrotic therapeutics in development.

Transforming growth factor (TGF)-β signalling is increased in rheumatoid synovium but TGF-β blockade does not modify experimental arthritis

The aim of this study was to analyse the distribution of regulatory and inhibitory mothers against decapentaplegic homologue (Smad) proteins as markers of active transforming growth factor (TGF)-β signalling in rheumatoid arthritis (RA) synovial tissue and to investigate the effect of TGF-β blockade in the development and progression of collagen-induced arthritis. The expression of Smad proteins in synovial tissues from RA, osteoarthritic and healthy controls was analysed by immunohistochemistry. Arthritis was induced in DBA/1 mice by immunization with chicken type-II collagen (CII). TGF-β was blocked in vivo with the specific peptide p17 starting at the time of immunization or on the day of arthritis onset. T cell population frequencies and specific responses to CII were analysed. The expression of cytokines and transcription factors was quantified in spleen and joint samples. Statistical differences between groups were compared using the Mann-Whitney U-test or one-way analysis of variance (anova) using the Kruskal-Wallis test. p-Smad-2/3 and inhibitory Smad-7 expression were detected in RA and control tissues. In RA, most lymphoid infiltrating cells showed nuclear p-Smad-2/3 without Smad-7 expression. Treatment with TGF-β antagonist did not affect clinical severity, joint inflammation and cartilage damage in collagen-induced arthritis. Frequency of T cell subsets, mRNA levels of cytokines and transcription factors, specific proliferation to CII, serum interleukin (IL)-6 and anti-CII antibodies were comparable in p17 and phosphate-buffered saline (PBS)-treated groups. The pattern of Smad proteins expression demonstrates active TGF-β signalling in RA synovium. However, specific TGF-β blockade does not have a significant effect in the mice model of collagen-induced arthritis.

Matrix Producing Cells in Chronic Kidney Disease: Origin, Regulation, and Activation

Chronic injury to the kidney causes kidney fibrosis with irreversible loss of functional renal parenchyma and leads to the clinical syndromes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Regardless of the type of initial injury, kidney disease progression follows the same pathophysiologic processes characterized by interstitial fibrosis, capillary rarefaction and tubular atrophy. Myofibroblasts play a pivotal role in fibrosis by driving excessive extracellular matrix (ECM) deposition. Targeting these cells in order to prevent the progression of CKD is a promising therapeutic strategy, however, the cellular source of these cells is still controversial. In recent years, a growing amount of evidence points to resident mesenchymal cells such as pericytes and perivascular fibroblasts, which form extensive networks around the renal vasculature, as major contributors to the pool of myofibroblasts in renal fibrogenesis. Identifying the cellular origin of myofibroblasts and the key regulatory pathways that drive myofibroblast proliferation and transdifferentiation as well as capillary rarefaction is the first step to developing novel anti-fibrotic therapeutics to slow or even reverse CKD progression and ultimately reduce the prevalence of ESRD. This review will summarize recent findings concerning the cellular source of myofibroblasts and highlight recent discoveries concerning the key regulatory signaling pathways that drive their expansion and progression in CKD.

Hypermethylation of EBF3 and IRX1 genes in synovial fibroblasts of patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease of unknown origin, which exhibits a complex heterogeneity in its pathophysiological background, resulting in differential responses to a range of therapies and poor long-term prognosis. RA synovial fibroblasts (RASFs) are key player cells in RA pathogenesis. Identification of DNA methylation biomarkers is a field that provides potential for improving the process of diagnosis and prognosis of various human diseases. We utilized a genome-wide technique, methylated DNA isolation assay (MeDIA), in combination with a high resolution CpG microarray for discovery of novel hypermethylated genes in RASFs. Thirteen genes (APEX1, EBF3, EGR2, EN1, IRX1, IRX6, KIF12, LHX2, MIPOL1, SGTA, SIN3A, TOLLIP, and ZHX2) with three consecutive hypermethylated probes were isolated as candidate genes through two CpG microarrays. Pyrosequencing assay was performed to validate the methylation status of TGF-β signaling components, EBF3 and IRX1 genes in RASFs and osteoarthritis (OA) SFs. Hypermethylation at CpG sites in the EBF3 and IRX1 genes was observed with a high methylation index (MI) in RASFs (52.5% and 41.4%, respectively), while a lower MI was observ ed in OASFs and h ealthy SFs (13.2% for EBF3 and 4.3% for IRX1). In addition, RT-PCR analysis showed a remarkable decrease in their mRNA expression in the RA group, compared with the OA or healthy control, and their reduction levels correlated with MI. The current findings suggest that methylation-associated down-regulation of EBF3 and IRX1 genes may play an important role in a pathogenic effect of TGF-β on RASFs. However, further clinical validation with large numbers of patients is needed in order to confirm our findings.

RNA-seq analysis of synovial fibroblasts brings new insights into rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic autoimmune-disease of unknown origin that primarily affects the joints and ultimately leads to their destruction. Growing evidence suggests that synvovial fibroblasts play important roles in the initiation and the perpetuation of RA but underlying molecular mechanisms are not understood fully. In the present study, Illumina RNA sequencing was used to profile two human normal control and two rheumatoid arthritis synvovial fibroblasts (RASFs) transcriptomes to gain insights into the roles of synvovial fibroblasts in RA.

Results

We found that besides known inflammatory and immune responses, other novel dysregulated networks and pathways such as Cell Morphology, Cell-To-Cell Signaling and Interaction, Cellular Movement, Cellular Growth and Proliferation, and Cellular Development, may all contribute to the pathogenesis of RA. Our study identified several new genes and isoforms not previously associated with rheumatoid arthritis. 122 genes were up-regulated and 155 genes were down-regulated by at least two-fold in RASFs compared to controls. Of note, 343 known isoforms and 561 novel isoforms were up-regulated and 262 known isoforms and 520 novel isoforms were down-regulated by at least two-fold. The magnitude of difference and the number of differentially expressed known and novel gene isoforms were not detected previously by DNA microarray.

Conclusions

Since the activation and proliferation of RASFs has been implicated in the pathogenesis of rheumatoid arthritis, further in-depth follow-up analysis of the transcriptional regulation reported in this study may shed light on molecular pathogenic mechanisms underlying synovial fibroblasts in arthritis and provide new leads of potential therapeutic targets.

Differential expression of wound fibrotic factors between facial and trunk dermal fibroblasts

Clinically, wounds on the face tend to heal with less scarring than those on the trunk, but the causes of this difference have not been clarified. Fibroblasts obtained from different parts of the body are known to show different properties. To investigate whether the characteristic properties of facial and trunk wound healing are caused by differences in local fibroblasts, we comparatively analyzed the functional properties of superficial and deep dermal fibroblasts obtained from the facial and trunk skin of seven individuals, with an emphasis on tendency for fibrosis. Proliferation kinetics and mRNA and protein expression of 11 fibrosis-associated factors were investigated. The proliferation kinetics of facial and trunk fibroblasts were identical, but the expression and production levels of profibrotic factors, such as extracellular matrix, transforming growth factor-β1, and connective tissue growth factor mRNA, were lower in facial fibroblasts when compared with trunk fibroblasts, while the expression of antifibrotic factors, such as collagenase, basic fibroblast growth factor, and hepatocyte growth factor, showed no clear trends. The differences in functional properties of facial and trunk dermal fibroblasts were consistent with the clinical tendencies of healing of facial and trunk wounds. Thus, the differences between facial and trunk scarring are at least partly related to the intrinsic nature of the local dermal fibroblasts.

Expression profile analysis of mycotoxin-related genes in cartilage with endemic osteochondropathy Kashin-Beck Disease

BACKGROUND

Kashin-Beck Disease (KBD) is an endemic osteochondropathy. Mycotoxins are believed to play an important role in the pathogenesis of KBD. Because the molecular mechanism of mycotoxin-induced cartilage lesions remains unclear, there is not effective treatment for KBD now. To identify key genes involved in the mycotoxin-induced cartilage lesions, we compared the expression profiles of mycotoxin-related genes (MRG) between KBD cartilage and healthy cartilage.

METHODS

Total RNA was isolated from cartilage samples, following by being amplified, labeled and hybridized to Agilent human whole genome microarray chip. qRT-PCR was conducted to validate the microarray data. 1,167 MRG were derived from the environmentally related genomic database Toxicogenomics. The microarray data of MRG was subjected to single gene and gene ontology (GO) expression analysis for identifying differently expressed genes and GO.

RESULTS

We identified 7 up-regulated MRG and 2 down-regulated MRG in KBD cartilage, involved in collagen, apoptosis, metabolism and growth & development. GO expression analysis found that 4 apoptosis-related GO and 5 growth & development-related GO were significantly up-regulated in KBD cartilage.

CONCLUSIONS

Based on the results of previous and our studies, we suggest that mycotoxins might contribute to the development of KBD through dysfunction of MRG involved in collagen, apoptosis and growth & development in cartilage.

Features of wound healing shown by fibroblasts obtained from the superficial and deep dermis

Dermal fibroblasts (DF) obtained from the superficial dermal layer and those from the deep dermal layer have different cellular functions. These differences are often associated with excessive scarring; they also influence early wound healing. We therefore investigated the differences between superficial and deep dermal fibroblasts with special emphasis on their contractile properties, and ability to produce connective tissue. We investigated their proliferation kinetics, ability to contract collagen lattices, and chronological mRNA expression of eight genes associated with wound healing. To estimate the changes in the differences between them during the early phase of wound healing, we investigated mRNA expression in bFGF supplemented medium because bFGF is a representative cytokine that is familiar to clinicians. Superficial DF proliferate faster than deep DF in culture, whereas deep DF are better at contracting collagen lattices than superficial ones. In realtime analysis of polymerase chain reaction, the expression of type I and III collagen, fibronectin, TGF β1 and β3, and connective tissue growth factor were higher in deep DF than in superficial DF, while the expression of TGF β2 was higher in superficial DF. After bFGF supplementation, the relative dominance of mRNA expression between superficial and deep DF remained constant except for the expression of collagenase. According to our analysis, deep DF are superior to superficial DF at promoting wound healing (particularly contraction and production of connective tissue). The intradermal distribution of DF is appropriate for efficient wound healing.

Thrombospondin1 in tissue repair and fibrosis: TGF-β-dependent and independent mechanisms

Thrombospondin 1 (TSP1) plays major roles in both physiologic and pathologic tissue repair. TSP1 through its type 1 repeats is a known regulator of latent TGF-β activation and plays a role in wound healing and fibrosis. Binding of the TSP N-terminal domain to cell surface calreticulin in complex with LDL-receptor related protein 1 stimulates intermediate cell adhesion, cell migration, anoikis resistance, collagen expression and matrix deposition in an in vivo model of the foreign body response. There is also emerging evidence that TSP EGF-like repeats alter endothelial cell-cell interactions and stimulate epithelial migration through transactivation of EGF receptors. The mechanisms underlying these functions of TSP1 and the implications for physiologic and pathologic wound repair and fibrosis will be discussed.

IL-33 regulates TNF-α dependent effects in synovial fibroblasts

The recently described IL-33 acts as a pro-inflammatory cytokine, inducing the expression of multiple responses in the target cells. Although a nuclear localization of IL-33 has been described, its exact functional relevance is presently unknown. The present study was conducted to analyze the effects of IL-33 on the TNF-α induced synthesis of the pro-inflammatory mediators IL-6, IL-8, and monocyte chemotactic protein-1 (MCP-1) and the pro-destructive molecules matrix metalloproteinase-1 (MMP-1), MMP-3, and TIMP-1 of rheumatoid arthritis synovial fibroblast (RA-SFs) using RNA overexpression and silencing. TNF-α significantly induced IL-33 mRNA expression and protein synthesis in RA-SFs. TNF-α-induced IL-33 protein expression was mediated via p38 signaling. Immunohistochemistry for IL-33 clearly showed that nuclear translocation of IL-33 was induced in TNF-α stimulated RA-SFs. IL-33 overexpression enhanced TNF-α-induced pro-inflammatory and pro-destructive functions in RA-SFs. IL-33 silencing significantly downregulated TNF-α-induced pro-inflammatory functions, whereas TNF-α-induced pro-destructive functions were less influenced by IL-33 silencing. This study identifies IL-33 as a critical regulator/enhancer of TNF-α-induced functions in RA-SFs, pointing to a central role of this cytokine in the perpetuation of pro-inflammatory and pro-destructive processes in rheumatoid arthritis (RA) and other inflammatory and degenerative diseases.

A systems biology approach to synovial joint lubrication in health, injury, and disease

The synovial joint contains synovial fluid (SF) within a cavity bounded by articular cartilage and synovium. SF is a viscous fluid that has lubrication, metabolic, and regulatory functions within synovial joints. SF contains lubricant molecules, including proteoglycan-4 and hyaluronan. SF is an ultrafiltrate of plasma with secreted contributions from cell populations lining and within the synovial joint space, including chondrocytes and synoviocytes. Maintenance of normal SF lubricant composition and function are important for joint homeostasis. In osteoarthritis, rheumatoid arthritis, and joint injury, changes in lubricant composition and function accompany alterations in the cytokine and growth factor environment and increased fluid and molecular transport through joint tissues. Thus, understanding the synovial joint lubrication system requires a multifaceted study of the various parts of the synovial joint and their interactions. Systems biology approaches at multiple scales are being used to describe the molecular, cellular, and tissue components and their interactions that comprise the functioning synovial joint. Analyses of the transcriptome and proteome of SF, cartilage, and synovium suggest that particular molecules and pathways play important roles in joint homeostasis and disease. Such information may be integrated with physicochemical tissue descriptions to construct integrative models of the synovial joint that ultimately may explain maintenance of health, recovery from injury, or development and progression of arthritis.

Synovial fluid of patients with rheumatoid arthritis induces alpha-smooth muscle actin in human adipose tissue-derived mesenchymal stem cells through a TGF-beta1-dependent mechanism

Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. Transforming growth factor-beta1 (TGF-beta1) is a secreted protein that promotes differentiation of synovial fibroblasts to alpha-smooth muscle actin (alpha-SMA)-positive myofibroblasts to repair the damaged joints. Synovial fluid from patients with RA (RA-SF) induced expression of alpha-SMA in human adipose tissue-derived mesenchymal stem cells (hASCs). RA-SF-induced alpha-SMA expression was abrogated by immunodepletion of TGF-beta1 from RA-SF with anti-TGF-beta1 antibody. Furthermore, pretreatment of hASCs with the TGF-beta type I receptor inhibitor SB431542 or lentiviral small hairpin RNA-mediated silencing of TGF-beta type I receptor expression in hASCs blocked RA-SF-induced alpha-SMA expression. Small interfering RNA-mediated silencing of Smad2 or adenoviral overexpression of Smad7 (an inhibitory Smad isoform) completely inhibited RA-SF-stimulated alpha-SMA expression. These results suggest that TGF-beta1 plays a pivotal role in RA-SF-induced differentiation of hASCs to alpha-SMA-positive cells.

The tumour-associated glycoprotein podoplanin is expressed in fibroblast-like synoviocytes of the hyperplastic synovial lining layer in rheumatoid arthritis

Introduction

Activated fibroblast-like synoviocytes (FLSs) in rheumatoid arthritis (RA) share many characteristics with tumour cells and are key mediators of synovial tissue transformation and joint destruction. The glycoprotein podoplanin is upregulated in the invasive front of several human cancers and has been associated with epithelial-mesenchymal transition, increased cell migration and tissue invasion. The aim of this study was to investigate whether podoplanin is expressed in areas of synovial transformation in RA and especially in promigratory RA-FLS.

Methods

Podoplanin expression in human synovial tissue from 18 RA patients and nine osteoarthritis (OA) patients was assessed by immunohistochemistry and confirmed by Western blot analysis. The expression was related to markers of synoviocytes and myofibroblasts detected by using confocal immunofluoresence microscopy. Expression of podoplanin, with or without the addition of proinflammatory cytokines and growth factors, in primary human FLS was evaluated by using flow cytometry.

Results

Podoplanin was highly expressed in cadherin-11-positive cells throughout the synovial lining layer in RA. The expression was most pronounced in areas with lining layer hyperplasia and high matrix metalloproteinase 9 expression, where it coincided with upregulation of α-smooth muscle actin (α-sma). The synovium in OA was predominantly podoplanin-negative. Podoplanin was expressed in 50% of cultured primary FLSs, and the expression was increased by interleukin 1β, tumour necrosis factor α and transforming growth factor β receptor 1.

Conclusions

Here we show that podoplanin is highly expressed in FLSs of the invading synovial tissue in RA. The concomitant upregulation of α-sma and podoplanin in a subpopulation of FLSs indicates a myofibroblast phenotype. Proinflammatory mediators increased the podoplanin expression in cultured RA-FLS. We conclude that podoplanin might be involved in the synovial tissue transformation and increased migratory potential of activated FLSs in RA.

A comprehensive molecular interaction map for rheumatoid arthritis

Background

Computational biology contributes to a variety of areas related to life sciences and, due to the growing impact of translational medicine - the scientific approach to medicine in tight relation with basic science -, it is becoming an important player in clinical-related areas. In this study, we use computation methods in order to improve our understanding of the complex interactions that occur between molecules related to Rheumatoid Arthritis (RA).

Methodology

Due to the complexity of the disease and the numerous molecular players involved, we devised a method to construct a systemic network of interactions of the processes ongoing in patients affected by RA. The network is based on high-throughput data, refined semi-automatically with carefully curated literature-based information. This global network has then been topologically analysed, as a whole and tissue-specifically, in order to translate the experimental molecular connections into topological motifs meaningful in the identification of tissue-specific markers and targets in the diagnosis, and possibly in the therapy, of RA.

Significance

We find that some nodes in the network that prove to be topologically important, in particular AKT2, IL6, MAPK1 and TP53, are also known to be associated with drugs used for the treatment of RA. Importantly, based on topological consideration, we are also able to suggest CRKL as a novel potentially relevant molecule for the diagnosis or treatment of RA. This type of finding proves the potential of in silico analyses able to produce highly refined hypotheses, based on vast experimental data, to be tested further and more efficiently. As research on RA is ongoing, the present map is in fieri, despite being -at the moment- a reflection of the state of the art. For this reason we make the network freely available in the standardised and easily exportable .xml CellDesigner format at ‘www.picb.ac.cn/ClinicalGenomicNTW/temp.html’ and ‘www.celldesigner.org’.

Transcription factor regulation can be accurately predicted from the presence of target gene signatures in microarray gene expression data

Deciphering transcription factor networks from microarray data remains difficult. This study presents a simple method to infer the regulation of transcription factors from microarray data based on well-characterized target genes. We generated a catalog containing transcription factors associated with 2720 target genes and 6401 experimentally validated regulations. When it was available, a distinction between transcriptional activation and inhibition was included for each regulation. Next, we built a tool (www.tfacts.org) that compares submitted gene lists with target genes in the catalog to detect regulated transcription factors. TFactS was validated with published lists of regulated genes in various models and compared to tools based on in silico promoter analysis. We next analyzed the NCI60 cancer microarray data set and showed the regulation of SOX10, MITF and JUN in melanomas. We then performed microarray experiments comparing gene expression response of human fibroblasts stimulated by different growth factors. TFactS predicted the specific activation of Signal transducer and activator of transcription factors by PDGF-BB, which was confirmed experimentally. Our results show that the expression levels of transcription factor target genes constitute a robust signature for transcription factor regulation, and can be efficiently used for microarray data mining.

CTLA4-Ig interacts with cultured synovial macrophages from rheumatoid arthritis patients and downregulates cytokine production

Introduction

Co-stimulatory signal B7(CD80/CD86):CD28 is needed in order to activate T cells in immune response. Cytotoxic T lymphocyte-associated antigen-4-immunoglobulin (CTLA4-Ig) binding to the B7 molecules on antigen-presenting cells downregulates this activation and represents a recent biological treatment in rheumatoid arthritis (RA). Objectives of the study were to investigate the presence of the B7.2 (CD86) molecule and its masking by CTLA4-Ig on cultures of both RA synovial macrophages (RA SM), and of macrophages differentiated from THP-1 cells (M). In addition, the anti-inflammatory effects of CTLA4-Ig on co-cultures of RA SM and M with activated T cells were tested.

Methods

All macrophages were co-cultured for 24 hours with activated T cells, without or with CTLA4-Ig (10, 100, 500 μg/ml for 1 hour, 3 hours and overnight, respectively). Immunofluorescence (IF) staining for B7.2, and an analysis of inflammatory cytokine expression (interleukin (IL) -6, tumor necrosis factor (TNF) α, IL-1β, transforming growth factor (TGF) β) by immunocytochemistry (ICC), western blot (WB) and reverse transcriptase-polymerase chain reaction (RT-PCR) were performed.

Results

Macrophages showed intense B7.2 expression. CTLA4-Ig/B7.2 masking was evident for all macrophages, even after only 1 hour of cell culture (range from 10 to 100 μg/ml). ICC of co-cultures showed a dose-dependent decrease in inflammatory cytokines (P < 0.001 for IL-6, TNFα, IL-1β and TGFβ). Data were confirmed by WB and RT-PCR analysis.

Conclusions

Optimal concentrations of CTLA4-Ig for the CTLA4-Ig/B7.2 masking on activated macrophages were identified and were found to induce significant downregulation in the cell production of IL-6, TNFα, IL1-β and TGFβ. In conclusion, macrophages would appear to be a sensitive target for CTLA4-Ig treatment in RA.

Fibrocyte activation in rheumatoid arthritis

OBJECTIVES

RA is a common, relapsing autoimmune disease primarily affecting the joints. Fibroblast-like synovial (FLS) cells are thought to be responsible for pannus formation and secretion of factors that recruit leucocytes to affected joints, thereby promoting bone and cartilage destruction. Fibrocytes are multipotent circulating stem cells that may have a role in RA pathogenesis, perhaps as the precursors of the FLS cells, or by regulating FLS cell function.

METHODS

We utilized multidimensional phospho-specific flow cytometry to characterize the activation status of peripheral blood (PB) fibrocytes derived from human RA patients at different stages of disease and from mice with CIA.

RESULTS

Human PB fibrocytes from RA patients exhibited phosporylation activation of the p44/42 and p38 MAP kinases (MAPKs), and STAT3 (signal transducer and activator of transcription) and STAT-5 early in disease, within the first year of diagnosis. Similarly, in murine CIA, an increase in the total number of PB phosphoSTAT5-positive fibrocytes was observed at early time points in disease. Notably, in the affected paws of mice with CIA, we identified an increased number of fibrocytes, in contrast to the paws of control mice.

CONCLUSIONS

These data suggest that activated fibrocytes may influence the disease process in RA and may serve as surrogate markers for disease in the PB of affected patients.

The role of T helper type 17 cells in inflammatory arthritis

While T cells have been implicated in the pathogenesis of inflammatory arthritis for more than three decades, the focus on the T helper type 17 (Th17) subset of CD4 T cells and their secreted cytokines, such as interleukin (IL)-17, is much more recent. Proinflammatory actions of IL-17 were first identified in the 1990s, but the delineation of a distinct Th17 subset in late 2005 has sparked great interest in the role of these cells in a broad range of immune-mediated diseases. This review summarizes current understanding of the role of Th17 cells and their products in both animal models of inflammatory arthritis and human immune-driven arthritides.

Role of SARA (SMAD anchor for receptor activation) in maintenance of epithelial cell phenotype

By inducing epithelial-to-mesenchymal transition (EMT), transforming growth factor-beta (TGF-beta) promotes cancer progression and fibrosis. Here we show that expression of the TGF-beta receptor-associated protein, SARA (Smad anchor for receptor activation), decreases within 72 h of exposure to TGF-beta and that this decline is both required and sufficient for the induction of several markers of EMT. It has been suggested recently that expression of the TGF-beta signaling mediators, Smad2 and Smad3, may have different functional effects, with Smad2 loss being more permissive for EMT progression. We find that the loss of SARA expression leads to a concomitant decrease in Smad2 expression and a disruption of Smad2-specific transcriptional activity, with no effect on Smad3 signaling or expression. Further, the effects of inducing the loss of Smad2 mimic those of the loss of SARA, enhancing expression of the EMT marker, smooth muscle alpha-actin. Smad2 mRNA levels are not affected by the loss of SARA. However, the ubiquitination of Smad2 is increased in SARA-deficient cells. We therefore examined the E3 ubiquitin ligase Smurf2 and found that although Smurf2 expression was unaltered in SARA-deficient cells, the interaction of Smad2 and Smurf2 was enhanced. These results describe a significant role for SARA in regulating cell phenotype and suggest that its effects are mediated through modification of the balance between Smad2 and Smad3 signaling. In part, this is achieved by enhancing the association of Smad2 with Smurf2, leading to Smad2 degradation.

Early and long-standing rheumatoid arthritis: distinct molecular signatures identified by gene-expression profiling in synovia

Introduction

Rheumatoid arthritis (RA) is a heterogeneous disease and its underlying molecular mechanisms are still poorly understood. Because previous microarray studies have only focused on long-standing (LS) RA compared to osteoarthritis, we aimed to compare the molecular profiles of early and LS RA versus control synovia.

Methods

Synovial biopsies were obtained by arthroscopy from 15 patients (4 early untreated RA, 4 treated LS RA and 7 controls, who had traumatic or mechanical lesions). Extracted mRNAs were used for large-scale gene-expression profiling. The different gene-expression combinations identified by comparison of profiles of early, LS RA and healthy synovia were linked to the biological processes involved in each situation.

Results

Three combinations of 719, 116 and 52 transcripts discriminated, respectively, early from LS RA, and early or LS RA from healthy synovia. We identified several gene clusters and distinct molecular signatures specifically expressed during early or LS RA, thereby suggesting the involvement of different pathophysiological mechanisms during the course of RA.

Conclusions

Early and LS RA have distinct molecular signatures with different biological processes participating at different times during the course of the disease. These results suggest that better knowledge of the main biological processes involved at a given RA stage might help to choose the most appropriate treatment.

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.

Gene expression and activity of cartilage degrading glycosidases in human rheumatoid arthritis and osteoarthritis synovial fibroblasts

INTRODUCTION

Similar to matrix metalloproteinases, glycosidases also play a major role in cartilage degradation. Carbohydrate cleavage products, generated by these latter enzymes, are released from degrading cartilage during arthritis. Some of the cleavage products (such as hyaluronate oligosaccharides) have been shown to bind to Toll-like receptors and provide endogenous danger signals, while others (like N-acetyl glucosamine) are reported to have chondroprotective functions. In the current study for the first time we systematically investigated the expression of glycosidases within the joints.

METHODS

Expressions of beta-D-hexosaminidase, beta-D-glucuronidase, hyaluronidase, sperm adhesion molecule 1 and klotho genes were measured in synovial fibroblasts and synovial membrane samples of patients with rheumatoid arthritis and osteoarthritis by real-time PCR. beta-D-Glucuronidase, beta-D-glucosaminidase and beta-D-galactosaminidase activities were characterized using chromogenic or fluorogenic substrates. Synovial fibroblast-derived microvesicles were also tested for glycosidase activity.

RESULTS

According to our data, beta-D-hexosaminidase, beta-D-glucuronidase, hyaluronidase, and klotho are expressed in the synovial membrane. Hexosaminidase is the major glycosidase expressed within the joints, and it is primarily produced by synovial fibroblasts. HexA subunit gene, one of the two genes encoding for the alpha or the beta chains of hexosaminidase, was characterized by the strongest gene expression. It was followed by the expression of HexB subunit gene and the beta-D-glucuronidase gene, while the expression of hyaluronidase-1 gene and the klotho gene was rather low in both synovial fibroblasts and synovial membrane samples. Tumor growth factor-beta1 profoundly downregulated glycosidase expression in both rheumatoid arthritis and osteoarthritis derived synovial fibroblasts. In addition, expression of cartilage-degrading glycosidases was moderately downregulated by proinflammatory cytokines including TNFalpha, IL-1beta and IL-17.

CONCLUSIONS

According to our present data, glycosidases expressed by synovial membranes and synovial fibroblasts are under negative regulation by some locally expressed cytokines both in rheumatoid arthritis and osteoarthritis. This does not exclude the possibility that these enzymes may contribute significantly to cartilage degradation in both joint diseases if acting in collaboration with the differentially upregulated proteases to deplete cartilage in glycosaminoglycans.

Prediction of disease severity in patients with early rheumatoid arthritis by gene expression profiling

In order to test the ability of peripheral blood gene expression profiles to predict future disease severity in patients with early rheumatoid arthritis (RA), a group of 17 patients (1 ± 0.2 years disease duration) was evaluated at baseline for gene expression profiles. Disease status was evaluated after a mean of 5 years using an index combining pain, global and recoded MHAQ scores. Unsupervised and supervised algorithms identified "predictor genes" whose combined expression levels correlated with follow-up disease severity scores. Unsupervised clustering algorithms separated patients into two branches. The only significant difference between these two groups was the disease severity score; demographic variables and medication usage were not different. Supervised T-Test analysis identified 19 "predictor genes" of future disease severity. Results were validated in an independent cohort of subjects of established RA with using Support Vector Machines and K-Nearest-Neighbor Classification. Our study demonstrates that peripheral blood gene expression profiles may be a useful tool to predict future disease severity in patients with early and established RA.

Sex hormones modulate the effects of Leflunomide on cytokine production by cultures of differentiated monocyte/macrophages and synovial macrophages from rheumatoid arthritis patients

Immune response is greater in females than in males and lymphocytes/monocytes from female subjects (or tested in vitro with estrogens) show higher immune/inflammatory reactivity. In order to test in vitro the interactions between 17beta-estradiol (E2--10(-9) M), testosterone (T--10(-8) M) and the antiproliferative/immune suppressive drug Leflunomide metabolite A77 1726 (LEF-M--30 microM) employed in rheumatoid arthritis (RA), their combined effects were evaluated on inflammatory cytokine (CK) expression/production in cultures of differentiated macrophages (M) (from activated THP-1 monocytes) and primary cultures of RA synovial macrophages (SM). TNFalpha, IL-6 and TGFbeta were detected by immunocytochemistry (ICC), Western blot analysis (WB) and reverse transcriptase-polymerase chain reaction (RT-PCR). The ICC, WB and RT-PCR showed a significant down-regulation induced by LEF-M on CK expression by cultured M when compared to untreated cells (IL-6 p < 0.01, TNFalpha p < 0.001, TGFbeta p < 0.01). At ICC analysis E2 increased CK expression, whereas T decreased the expression, confirmed by WB and RT-PCR (range between p < 0.05 and p < 0.001). LEF-M treatment significantly downregulated the CK expression in E2/T treated M: the effect was more significant in LEF-M plus T-treated cells versus controls (range between p < 0.01 and p < 0.001). Concerning the RA SM, the results were replicated (range between p < 0.05 and p < 0.001). E2 seems to contrast, but T seems to synergize the LEF-M activity. Results might support a stronger therapeutical efficacy, at least for LEF, in male RA patients, as already reported by clinical evidences.

In vitro model for the analysis of synovial fibroblast-mediated degradation of intact cartilage

Introduction

Activated synovial fibroblasts are thought to play a major role in the destruction of cartilage in chronic, inflammatory rheumatoid arthritis (RA). However, profound insight into the pathogenic mechanisms and the impact of synovial fibroblasts in the initial early stages of cartilage destruction is limited. Hence, the present study sought to establish a standardised in vitro model for early cartilage destruction with native, intact cartilage in order to analyse the matrix-degrading capacity of synovial fibroblasts and their influence on cartilage metabolism.

Methods

A standardised model was established by co-culturing bovine cartilage discs with early-passage human synovial fibroblasts for 14 days under continuous stimulation with TNF-α, IL-1β or a combination of TNF-α/IL-1β. To assess cartilage destruction, the co-cultures were analysed by histology, immunohistochemistry, electron microscopy and laser scanning microscopy. In addition, content and/or neosynthesis of the matrix molecules cartilage oligomeric matrix protein (COMP) and collagen II was quantified. Finally, gene and protein expression of matrix-degrading enzymes and pro-inflammatory cytokines were profiled in both synovial fibroblasts and cartilage.

Results

Histological and immunohistological analyses revealed that non-stimulated synovial fibroblasts are capable of demasking/degrading cartilage matrix components (proteoglycans, COMP, collagen) and stimulated synovial fibroblasts clearly augment chondrocyte-mediated, cytokine-induced cartilage destruction. Cytokine stimulation led to an upregulation of tissue-degrading enzymes (aggrecanases I/II, matrix-metalloproteinase (MMP) 1, MMP-3) and pro-inflammatory cytokines (IL-6 and IL-8) in both cartilage and synovial fibroblasts. In general, the activity of tissue-degrading enzymes was consistently higher in co-cultures with synovial fibroblasts than in cartilage monocultures. In addition, stimulated synovial fibroblasts suppressed the synthesis of collagen type II mRNA in cartilage.

Conclusions

The results demonstrate for the first time the capacity of synovial fibroblasts to degrade intact cartilage matrix by disturbing the homeostasis of cartilage via the production of catabolic enzymes/pro-inflammatory cytokines and suppression of anabolic matrix synthesis (i.e., collagen type II). This new in vitro model may closely reflect the complex process of early stage in vivo destruction in RA and help to elucidate the role of synovial fibroblasts and other synovial cells in this process, and the molecular mechanisms involved in cartilage degradation.

Identification of intra-group, inter-individual, and gene-specific variances in mRNA expression profiles in the rheumatoid arthritis synovial membrane

Introduction

Rheumatoid arthritis (RA) is a chronic inflammatory and destructive joint disease characterized by overexpression of pro-inflammatory/pro-destructive genes and other activating genes (for example, proto-oncogenes) in the synovial membrane (SM). The gene expression in disease is often characterized by significant inter-individual variances via specific synchronization/desynchronization of gene expression. To elucidate the contribution of the variance to the pathogenesis of disease, expression variances were tested in SM samples of RA patients, osteoarthritis (OA) patients, and normal controls (NCs).

Method

Analysis of gene expression in RA, OA, and NC samples was carried out using Affymetrix U133A/B oligonucleotide arrays, and the results were validated by real-time reverse transcription-polymerase chain reaction. For the comparison between RA and NC, 568 genes with significantly different variances in the two groups (P ≤ 0.05; Bonferroni/Holm corrected Brown-Forsythe version of the Levene test) were selected. For the comparison between RA and OA, 333 genes were selected. By means of the Kyoto Encyclopedia of Genes and Genomes, the pathways/complexes significantly affected by higher gene expression variances were identified in each group.

Results

Ten pathways/complexes significantly affected by higher gene expression variances were identified in RA compared with NC, including cytokine–cytokine receptor interactions, the transforming growth factor-beta pathway, and anti-apoptosis. Compared with OA, three pathways with significantly higher variances were identified in RA (for example, B-cell receptor signaling and vascular endothelial growth factor signaling). Functionally, the majority of the identified pathways are involved in the regulation of inflammation, proliferation, cell survival, and angiogenesis.

Conclusion

In RA, a number of disease-relevant or even disease-specific pathways/complexes are characterized by broad intra-group inter-individual expression variances. Thus, RA pathogenesis in different individuals may depend to a lesser extent on common alterations of the expression of specific key genes, and rather on individual-specific alterations of different genes resulting in common disturbances of key pathways.

Thrombospondin-1 and transforming growth factor beta are pro-inflammatory molecules in rheumatoid arthritis

Thrombospondin-1 (TSP1/THBS1) plays a major role in the pathophysiology of rheumatoid arthritis (RA); however, its interface with the cytokine network involved in RA has not been delineated. Correlations were performed between plasma levels of TSP1 and selected cytokines from blood samples collected from 20 patients affected by RA and 13 healthy donors (control). Plasma levels of TSP1 and tissue growth factor beta (TGFbeta) were determined by standard enzyme-linked immunosorbent assay, and cytokines were measured by protein profiling rolling-circle amplification (RCA). TSP1 circulating levels in plasma were found significantly increased in the RA patients when compared with control individuals (P = 0.039). The plasma levels of TGFbeta were also increased in the RA patients, which indicates a statistical trend. Cytokine levels of interleukin (IL)-4, IL-5, IL-12, chemokine CXC 10 (CXCL10/IP10), and chemokine CC 4 (CCL4)/MIP1beta were significantly increased in the RA patients when compared with the control group. In summary, this study demonstrates increased plasma levels of TSP1, which correlated with increased levels of proinflammatory cytokines in plasma of RA patients. More detailed research is required to explore the cytokine imprint yielded by this study and its interface with TSP1 and TGFbeta.