Synovial Lining Cells Research Articles

Expression Pattern of iNOS, BCL-2 and MMP-9 in the Hip Synovium Tissue of Patients with Osteoarthritis.

Hip osteoarthritis (HOA) is characterized by degradation of the cartilage and synovitis. However, the pathohistological effects of synovial tissue inflammation on HOA are not clear. The aim of this study was to evaluate the expression of iNOS, BCL-2 and MMP-9 markers in different synovial cell populations. A total of 32 patients were evaluated retrospectively. Age, sex, height, weight, body mass index were recorded and lymphocyte, fibrocytes and macrophages were analysed in tissue sections. Osteoarthritis cartilage histopathology assessment system (OARSI), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Krenn score, Harris Hip Score (HHS) and Kellgren–Lawrence (K-L) grading of the hip joints were performed. Total hip arthroplasty was performed on 32 patients and controls. Patients were divided into two groups according to their disease severity. The tissues were immunohistochemically analysed. K-L grade and Krenn score differ between all three groups, but also between moderate and severe OA. Synovial lining cell layer, resident cells in stroma and especially inflammatory infiltration were increasing with severity of OA. iNOS expression in both intima and subintima was positively correlated with Krenn score in moderate and severe osteoarthritis (OA) groups. Expression of BCL-2 in intima of severe OA patients was positively correlated with Krenn score. In conclusion, iNOS, BCL-2 and MMP-9 are involved in the regulation of HOA. Our study indicates a relationship between the pathohistological features, the synovial inflammation and the cartilage condition at the time of hip replacement due to OA or femoral neck fracture.

There is a correlation between histopathological findings of joint capsule and synovium, and postoperative clinical outcomes and treatment in patients with isolated type II superior labrum anterior posterior lesions.

Objectives This study aims to histologically examine the joint capsule and synovium to determine the correlation between histopathological findings and postoperative clinical outcomes in patients with isolated type II superior labrum anterior posterior (SLAP) lesions.Patients and methods Thirty-eight patients (24 males, 14 females; mean age 53.2±6.6 years; range, 45 to 67 years) who underwent arthroscopic treatment of type II SLAP lesions between June 2017 and September 2018 were evaluated prospectively. Visual analog scale (VAS), Simple Shoulder Test (SST), and American Shoulder and Elbow Surgeons (ASES) scores of all patients were recorded preoperatively, and at 6th and 12th months postoperatively. Biceps tenotomy was applied as arthroscopic surgical treatment in all patients. Biopsy materials obtained from rotator interval joint capsule and synovium during the arthroscopy were evaluated histopathologically. The density of the vessels in the specimens was defined as low, medium, and high by the pathologist. The patients with medium or low vessel density in specimens were group 1 (n=14) and those with high vessel density group 2 (n=24).Results In group 2, preoperative VAS score was significantly higher. There was no difference between the scores of the groups except for the sixth month SST score which was significantly higher in group 1. Histopathological evaluation revealed that the number of lymphocytes, fibroblasts, mast cells, myofibroblast, synovial lining cells, macrophages, and amount of collagen in connective tissue were significantly higher in group 2. In five patients of group 2, the rehabilitation program was interrupted due to pain and difficulty in gaining a range of motion during the first four weeks postoperatively. Four of these patients recovered with medication and long-duration physiotherapy. Shoulder stiffness developed in one patient who required arthroscopic release and further rehabilitation.ConclusionThere is a correlation between histopathological findings of joint capsule and synovium, and postoperative clinical outcomes and treatment in patients with isolated type II SLAP lesions. Almost 20% of patients who had pathologic histological findings in joint capsule and synovium needed pain control and long-duration rehabilitation program after arthroscopic surgery for better shoulder function recovery and prevention of shoulder stiffness.

Optimal Treatment for Tenosynovial Giant Cell Tumor of the Hand.

This review examines the following aspects of tenosynovial giant cell tumors (TSGCTs): the use of multiple names, the complex relationship between tumor growth pattern and location, the high rate of postoperative recurrence, local invasiveness, use of nonsurgical therapy with molecularly targeted drugs, and best current treatments. This tumor has been referred to by various names, but is now most frequently referred to as TSGCT. TSGCT is classified as localized and diffuse, in accordance with its growth characteristics. Most TSGCTs of the fingers are localized. TSGCT is likely a neoplastic process arising from synovial lining cells, in which tumor cells express the colony stimulating factor 1 (CSF1) gene. The postoperative recurrence rate of TSGCT is approximately 15%. The intrinsic characteristics of recurrence are not clear, and complete resection of the lesion is still the treatment mainstay. Moreover, TSGCT commonly grows out of a pseudocapsule. Therefore, to perform complete resection of TSGCT, surgery must be performed cautiously after appropriate preparation, by using anesthesia, a tourniquet, surgical loupe, and surgical microscopy. After accurate preoperative diagnosis, meticulous planning by surgeons is necessary. The lesion should be resected along with approximately 1-mm of healthy tissue at the adhesion site. In addition, because satellite lesions might be present near the tumor, careful dissection and observation of the color of surrounding tissue are important. International clinical trials of CSF1 receptor inhibitors for TSGCT treatment are ongoing.

Contracture and transient receptor potential channel upregulation in the anterior glenohumeral joint capsule of patients with end-stage osteoarthritis

During anatomic total shoulder arthroplasty (TSA) for primary glenohumeral osteoarthritis (GHOA), the anterior shoulder joint capsule (ASJC) is characterized grossly by contracture, synovitis, and fibrosis. In tissues that develop fibrosis, there is substantial cross-talk between macrophages, fibroblasts, and myofibroblasts, modulated by calcium signaling and transient receptor potential (TRP) channel signaling. The purpose of this study was to compare and characterize the degree of synovitis, inflammatory infiltrate, and TRP channel expression in ASJC harvested from shoulders with and without primary GHOA. The ASJC was resected from patients undergoing TSA for primary GHOA or other diagnoses and compared with ASJC from cadaveric donors with no history of shoulder pathology. ASJC was evaluated by immunohistochemistry to characterize synovial lining and capsular inflammatory cell infiltrate and fibrosis, and to evaluate for expression of TRPA1, TRPV1, and TRPV4, known to be involved in fibrosis in other tissues. Blinded sections were evaluated by 3 graders using a semiquantitative scale; then results were compared between diagnosis groups using nonparametric methods. Compared with normal control, the ASJC in primary GHOA had significantly increased synovitis, fibrosis, mixed inflammatory cell infiltrate including multiple macrophages subsets, and upregulation of TRP channel expression. These data support the clinical findings of ASJC and synovial fibrosis in primary GHOA, identify a mixed inflammatory response, and identify dysregulation of TRP channels in the synovium and joint capsule. Further studies will identify the role of synovial and capsular fibrosis early in the development of GHOA.

Implication of HYBID (Hyaluronan-Binding Protein Involved in Hyaluronan Depolymerization) in Hyaluronan Degradation by Synovial Fibroblasts in Patients with Knee Osteoarthritis

Cell migration-inducing hyaluronidase 1 (CEMIP), also known as hyaluronan (HA)-binding protein involved in HA depolymerization (HYBID), plays a role in HA degradation. CEMIP2, also known as transmembrane protein 2 (TMEM2), possessing a sequence similarity with HYBID, is reported as a hyaluronidase in mice. However, the expression of these molecules in osteoarthritic synovium and their involvement in HA degradation in synovial fluid (SF) from patients with knee osteoarthritis remain elusive. This study examined their expression in synovial tissue and the relationship with molecular weight of HA in SF in knee osteoarthritis patients. Quantification of mRNA demonstrated that HYBID expression is significantly (5.5-fold) higher in osteoarthritic synovium than in normal control synovium, whereas TMEM2 expression level is similar between the two groups. By immunohistochemistry, HYBID was localized mainly to CD68-negative and fibroblast-specific protein 1-positive synovial lining cells and sublining fibroblasts in osteoarthritic synovium. The mRNA expression levels of HYBID, but not TMEM2, in osteoarthritic synovium positively correlated with distribution of lower-molecular-weight HA with below 1000 kDa in SF. HA-degrading activity in osteoarthritic synovial fibroblasts was abrogated by siRNA-mediated knockdown of HYBID. Among the 12 factors examined, IL-6 significantly up-regulated the HYBID expression and HA-degrading activity in osteoarthritic synovial fibroblasts. These data suggest that HYBID overexpressed by IL-6-stimulated synovial fibroblasts is implicated in HA degradation in osteoarthritic synovium.

Comparative study of HO-1 expressing synovial lining cells between RA and OA

Objectives We aimed to clarify the characteristics of heme oxygenase (HO)-1 expressing cells in the synovium from rheumatoid arthritis (RA) and osteoarthritis (OA), and to investigate the co-expression of HO-1 and IgG-Fc/HLA-DR complex. Methods The characteristics of HO-1 expressing cells in the synovium were investigated by using immunohistochemistry. The co-expression of HO-1 and IgG-Fc/HLA-DR complex was examined by an in situ proximity ligation assay (PLA) with immunofluorescence. HO-1 mRNA was investigated by reverse transcription-polymerase chain reaction. Results The number of HO-1+ cells from the RA synovium is higher than that from OA synovium. The double positive cells of HO-1 and IgG-Fc/HLA-DR complex were detected by the in situ PLA with immunofluorescence in RA synovium. HO-1 mRNA was detected in both RA and OA synovium. Conclusion A portion of HO-1+ cells with IgG-Fc/HLA-DR complex in lining layer of RA may be concluded as one of antigen presenting cells in RA and may be involved in production of RF.

Xenotransplantation of human dental pulp stem cells in platelet-rich plasma for the treatment of full-thickness articular cartilage defects in a rabbit model.

Stem cells in platelet-rich plasma (PRP) scaffolds may be a promising treatment for cartilage repair. Human dental pulp stem cell (hDPSC) subpopulations have been identified to have substantial angiogenic, neurogenic and regenerative potential when compared with other stem cell sources. The present study evaluated the potential of hDPSCs in a PRP scaffold to regenerate full-thickness cartilage defects in rabbits. Full-thickness articular cartilage defects were created in the patellar groove of the femur of 30 rabbits allocated into three experimental groups: Those with an untreated critical defect (CTL), those treated with PRP (PRP) and those treated with stem cells in a PRP scaffold (PRP+SC). The patellar grooves of the femurs from the experimental groups were evaluated macroscopically and histologically at 6 and 12 weeks post-surgery. The synovial membranes were also collected and evaluated for histopathological analysis. The synovial lining cell layer was enlarged in the CTL group compared with the PRP group at 6 weeks (P=0.037) but not with the PRP+SC group. All groups exhibited low-grade synovitis at 6 weeks and no synovitis at 12 weeks. Notably, macroscopic grades for the area of articular cartilage repair for the PRP+SC group were significantly improved compared with those in the CTL (P=0.001) and PRP (P=0.049) groups at 12 weeks. Furthermore, histological scores (modified O'Driscoll scoring system) of the patellar groove articular cartilage in the PRP+SC and PRP groups, in which the articular cartilage was primarily hyaline-like, were significantly higher compared with those in the CTL group at 12 weeks (P=0.002 and P=0.007, respectively). The present results support the therapeutic use of hDPSCs for the treatment of full-thickness articular cartilage defects.

Effect of vitamin D3 on glucocorticoid-induced impairments of rat hippocampus morphology and behavior

During anatomic total shoulder arthroplasty (TSA) for primary glenohumeral osteoarthritis (GHOA), the anterior shoulder joint capsule (ASJC) is characterized grossly by contracture, synovitis, and fibrosis. In tissues that develop fibrosis, there is substantial cross-talk between macrophages, fibroblasts, and myofibroblasts, modulated by calcium signaling and transient receptor potential (TRP) channel signaling. The purpose of this study was to compare and characterize the degree of synovitis, inflammatory infiltrate, and TRP channel expression in ASJC harvested from shoulders with and without primary GHOA.The ASJC was resected from patients undergoing TSA for primary GHOA or other diagnoses and compared with ASJC from cadaveric donors with no history of shoulder pathology. ASJC was evaluated by immunohistochemistry to characterize synovial lining and capsular inflammatory cell infiltrate and fibrosis, and to evaluate for expression of TRPA1, TRPV1, and TRPV4, known to be involved in fibrosis in other tissues. Blinded sections were evaluated by 3 graders using a semiquantitative scale; then results were compared between diagnosis groups using nonparametric methods.Compared with normal control, the ASJC in primary GHOA had significantly increased synovitis, fibrosis, mixed inflammatory cell infiltrate including multiple macrophages subsets, and upregulation of TRP channel expression.These data support the clinical findings of ASJC and synovial fibrosis in primary GHOA, identify a mixed inflammatory response, and identify dysregulation of TRP channels in the synovium and joint capsule. Further studies will identify the role of synovial and capsular fibrosis early in the development of GHOA.

Clinicopathological value of programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) expression in synovium of patients with rheumatoid arthritis.

The etiology of rheumatoid arthritis (RA) is thought to involve dysfunction of the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) pathway; PD-1 negatively regulates autoimmunity by interacting with its ligand, PD-L1. We therefore investigated PD-1/PD-L1 expression in synovial tissue of patients with RA. We immunohistochemically stained synovial specimens from 51 patients with RA and assessed the association between PD-1/PD-L1 expression and rheumatoid factor (RF), the total count of infiltrating T cells, C-reactive protein (CRP), and Krenn's synovitis score. PD-1 expression on infiltrating lymphocytes was detected in 34/51 RA cases (66.7%), while PD-1 expression was very mildly correlated only with the number of total infiltrating T cells (R2 = 0.1011, P = 0.0230). On the other hand, PD-L1 expression on synovial lining cells was observed in 37/51 RA cases (72.5%). Furthermore, a higher PD-L1 expression was significantly associated with RF positive state (P = 0.0454), and the correlations between PD-L1 expression and the number of infiltrating T cells (R2 = 0.5571, P < 0.0001), CRP (R2 = 0.4060, P < 0.0001), and Krenn's synovitis score (R2 = 0.7785, P < 0.0001) were confirmed. PD-1 was expressed on infiltrating lymphocytes, while PD-L1 was expressed on synovial lining cells; the expression of PD-L1 on synovial lining cells was significantly correlated with the active state of the disease. These data suggest that PD-1/PD-L1 pathway may have an important role in the pathogenesis of RA.

Toll-Like Receptor 4 (TLR4) Stimulates Synovial Injury of Temporomandibular Joint in Rats Through the Activation of p38 Mitogen-Activated Protein Kinase (MAPK) Signaling Pathway.

BackgroundSynovitis is an important disease that cause intractable pain in temporomandibular joint (TMJ), and the inflammation process played a crucial role in the initiation and development of temporomandibular joint disorder. A series of investigations suggested that the increasing expression of interleukin-(IL) 1β secreted by synovial lining cells plays an important role in synovial inflammation and cartilage destruction in TMJ. In this present study, we investigated the signaling pathways which regulate the expression of IL-1β.Material/MethodsThe occlusal interference animal model was created to induce synovial injury. Forty-eight rats were divided into 4 groups: 1) control group, 2) occlusal interference group, 3) TAK-242 (a specific inhibitor targeting the Toll-like receptor (TLR)-4) group, and 4) SB203580 (a specific inhibitor targeting the p38) group. The inflammation changes were observed, and the expression of p38 and IL-1β in the synovial membranes were assayed.ResultsThe results showed that downstream p38 MAPK (mitogen-activated protein kinase) signaling was triggered following the activation of TLR4. Moreover, the injection of SB203580 could inhibit the inflammatory reactions and the increased expression of IL-1β at both mRNA and protein levels.ConclusionsThe results prompted us that TLR4 may stimulates synovial inflammatory reactions and increased expression of IL-1β in rats through the activation of p38 MAPK signaling pathway, p38 was an important mediator in the mechanisms of the initiation and development of synovial injury by regulating the expression of IL-1β in synovial membranes.

Immunohistochemical Analysis of Inflammatory Rheumatoid Synovial Tissues Using Anti-Human Podoplanin Monoclonal Antibody Panel.

Podoplanin (PDPN) is a transmembrane sialoglycoprotein, which is expressed in several normal tissues and malignant tumors. Although PDPN expression in rheumatoid arthritis (RA) has been reported, the role of PDPN in RA and other arthritic conditions has not been fully elucidated. In this study, we examined PDPN expression in inflammatory synovial tissues using an anti-human PDPN (hPDPN) monoclonal antibody (mAb) panel to select the most useful one for evaluation of synovitis. Synovial tissue samples were obtained from 11 RA patients and 9 osteoarthritis (OA) patients undergoing joint surgery. PDPN-positive cells were immunostained by a panel of PDPN mAbs (NZ-1, LpMab-3, LpMab-7, LpMab-10, LpMab-12, LpMab-13, and LpMab-17), followed by cell grading of inflammation and cell counting of PDPN-positivity by a quantitative analyzer. Immunohistochemistry showed that PDPN was markedly expressed in both macrophage-like type A and fibroblast-like type B lining cells of the hyperplastic synovial lining cell layer, and macrophages and fibroblasts in the stroma of RA. Among anti-PDPN mAbs, LpMab-12 showed the highest score. In inflammatory OA synovium, PDPN expression was also detectable. Although LpMab-12 also showed the highest score in OA, the difference was not statistically significant. The inflammatory synovitis score of RA was significantly higher than that of OA. PDPN was expressed in inflammatory lining cells and sublining stroma of RA and OA synovium. In the seven anti-hPDPN antibodies examined, LpMab-12 was the most stainable antibody for PDPN in RA synovitis. Thus, LpMab-12 for PDPN has a possible and promising specific biomarker for evaluating synovitis in RA and inflammatory OA.

Current Pathologic Scoring Systems for Metal-on-metal THA Revisions are not Reproducible

BackgroundThe aseptic lymphocyte vasculitis-associated lesion (ALVAL) score and the modified Oxford ALVAL score are frequently used scoring methods to evaluate the morphologic features of periprosthetic tissues around metal-on-metal (MoM) hip implants. Except for the initial studies of these two morphology scoring methods, to our knowledge, no other studies have reported on intraclass correlation coefficient (ICC) values for interobserver reliability of these scoring methods.Questions/purposesAre the ALVAL and Oxford ALVAL scores reproducible?MethodsThe periprosthetic tissue of 37 revisions of 36 patients with failed MoM THAs were independently scored by three experienced pathologists using ALVAL and Oxford ALVAL scoring methods. All patients were included who underwent revision surgery in our hospital until January 2013, with a large-head MoM prosthesis and also met the criteria: blood serum cobalt levels, available MRI scan, and intraarticular cobalt levels. The population included 26 patients with pseudotumors diagnosed by two radiologists using the method described by Matthies et al. The ALVAL describes morphologic features of the synovial lining, tissue organization, and inflammatory cell infiltrate in periprosthetic tissues. The Oxford-ALVAL score uses a semiquantitative measure of the immune response which should be easier to score.ResultsThe ALVAL score showed an ICC of 0.38 (95% CI, 0.18–0.58) (fair) for the sum score and this improved up to 0.50 (95% CI, 0.31–0.68) (moderate) using the modified Oxford ALVAL score. The individual parameters of the ALVAL score showed an ICC for the scoring of inflammatory infiltrate of 0.37 (95% CI, 0.17–0.57), an ICC of 0.32 (95% CI, 0.12–0.53) for the scoring of tissue organization, and an ICC of 0.14 (95% CI, −0.04 to 0.34) for synovial lining.ConclusionsScoring morphologic features of MoM tissue is not reproducible using the ALVAL score or the Oxford ALVAL score. This may reflect heterogeneous morphologic features in tumor tissue and between different tumor tissue samples that cannot be reliably quantified by pathologists using the parameters of these two scoring methods. An alternative, simplified scoring system should be developed to improve the interrater agreement.Level of EvidenceLevel III, diagnostic study.

Role of LIGHT in the pathogenesis of joint destruction in rheumatoid arthritis.

AIMTo characterise the role of substitutes for receptor-activator nuclear factor kappa-B ligand (RANKL) in rheumatoid arthritis (RA) joint destruction.METHODSSynovial fluid (SF) macrophages isolated from the knee joint of RA patients were incubated with 25 ng/mL macrophage-colony stimulating factor (M-CSF) and 50 ng/mL LIGHT (lymphotoxin-like, exhibits inducible expression and competes with herpes simplex virus glycoprotein D for herpes virus entry mediator, a receptor expressed by T lymphocytes) in the presence and absence of 25 ng/mL RANKL and 100 ng/mL osteoprotegerin (OPG) on glass coverslips and dentine slices. Osteoclastogenesis was assessed by the formation of multinucleated cells (MNCs) expressing tartrate-resistant acid phosphatase (TRAP) on coverslips and the extent of lacunar resorption pit formation on dentine slices. The concentration of LIGHT in RA and osteoarthritis (OA) synovial fluid was measured by an enzyme-linked immunosorbent assay (ELISA) and the expression of LIGHT in RA and OA synovium was determined by immunohistochemistry using an indirect immunoperoxidase technique.RESULTSIn cultures of RA SF macrophages treated with LIGHT and M-CSF, there was significant formation of TRAP + MNCs on coverslips and extensive lacunar resorption pit formation on dentine slices. SF-macrophage-osteoclast differentiation was not inhibited by the addition of OPG, a decoy receptor for RANKL. Resorption pits were smaller and less confluent than in RANKL-treated cultures but the overall percentage area of the dentine slice resorbed was comparable in LIGHT- and RANKL-treated cultures. LIGHT significantly stimulated RANKL-induced lacunar resorption compared with RA SF macrophages treated with either RANKL or LIGHT alone. LIGHT was strongly expressed by synovial lining cells, subintimal macrophages and endothelial cells in RA synovium and the concentration of LIGHT was much higher in RA compared with OA SF.CONCLUSIONLIGHT is highly expressed in RA synovium and SF, stimulates RANKL-independent/dependent osteoclastogenesis from SF macrophages and may contribute to marginal erosion formation.

Evaluation of Hyaluronic Acid Dilutions at Different Concentrations Using a Quartz Crystal Resonator (QCR) for the Potential Diagnosis of Arthritic Diseases.

The main objective of this article is to demonstrate through experimental means the capacity of the quartz crystal resonator (QCR) to characterize biological samples of aqueous dilutions of hyaluronic acid according to their viscosity and how this capacity may be useful in the potential diagnosis of arthritic diseases. The synovial fluid is viscous due to the presence of hyaluronic acid, synthesized by synovial lining cells (type B), and secreted into the synovial fluid thus making the fluid viscous. In consequence, aqueous dilutions of hyaluronic acid may be used as samples to emulate the synovial fluid. Due to the viscoelastic and pseudo-plastic behavior of hyaluronic acid, it is necessary to use the Rouse model in order to obtain viscosity values comparable with viscometer measures. A Fungilab viscometer (rheometer) was used to obtain reference measures of the viscosity in each sample in order to compare them with the QCR prototype measures.

Critical Role of Glucose Metabolism in Rheumatoid Arthritis Fibroblast-like Synoviocytes.

Up-regulation of glucose metabolism has been implicated not only in tumor cell growth but also in immune cells upon activation. However, little is known about the metabolite profile in rheumatoid arthritis (RA), particularly in fibroblast-like synoviocytes (FLS). This study was undertaken to evaluate whether changes in glucose metabolism in RA FLS could play a role in inflammation and joint damage. Synovium and FLS were obtained from patients with RA and patients with osteoarthritis (OA). The rate of glycolysis after stimulation of FLS with lipopolysaccharide and platelet-derived growth factor BB was measured using glycolysis stress test technology. FLS function was evaluated using a glycolysis inhibitor, 2-deoxy-d-glucose (2-DG). After stimulation of the FLS, a migration scratch assay, MTT assay, and enzyme-linked immunosorbent assay were performed to measure the effect of 2-DG on FLS migration, viability of the FLS, and cytokine secretion, respectively. IRDye 800CW 2-DG was used to assess glucose uptake in the arthritic joints and stromal cells of mice after K/BxN mouse serum transfer. The mice were injected daily, intraperitoneally, with 3-bromopyruvate (BrPa; 5 mg/kg) to assess the effect of inhibition of glycolysis in vivo. Compared to human OA FLS, the balance between glycolysis and oxidative phosphorylation was shifted toward glycolysis in RA FLS. Glucose transporter 1 (GLUT1) messenger RNA (mRNA) expression correlated with baseline functions of the RA FLS. Glucose deprivation or incubation of the FLS with glycolytic inhibitors impaired cytokine secretion and decreased the rate of proliferation and migration of the cells. In a mouse model of inflammatory arthritis, GLUT1 mRNA expression in the synovial lining cells was observed, and increased levels of glucose uptake and glycolytic gene expression were detected in the stromal compartment of the arthritic mouse joints. Inhibition of glycolysis by BrPa, administered in vivo, significantly decreased the severity of arthritis in this mouse model. Targeting metabolic pathways is a novel approach to understanding the mechanisms of disease. Inhibition of glycolysis may directly modulate synoviocyte-mediated inflammatory functions and could be an effective treatment strategy for arthritis.

The growth factor midkine may play a pathophysiological role in rheumatoid arthritis

Objectives: Midkine (MK) is involved in cell proliferation, differentiation, migration, and survival. In this study, we measured serum MK levels in rheumatoid arthritis (RA) and investigated the correlation of serum MK with RA disease activity. Expression and effect of MK in RA synovial tissue were also examined.Methods: Serum MK and production of inflammatory mediators by rheumatoid synovial fibroblasts (RSFs) were measured by enzyme-linked immunosorbent assay. MK expression in synovial tissue was examined by immunohistochemistry. MK receptor expression was analyzed by RT-PCR and Western blotting.Results: RA patients had a significantly higher serum MK level than healthy controls. In RA patients, the MK level was correlated with DAS28-ESR, disability index of the Health Assessment Questionnaire, and rheumatoid factor level. The serum MK level tended to be decreased by anti-TNF therapy. MK was expressed by synovial lining cells in RA synovial tissues and it enhanced the production of IL-6, IL-8, and CCL2 by RSFs. RSFs expressed LDL receptor-related protein 1, candidate receptor for MK.Conclusions: The serum MK level could be a marker of disease activity in RA and an indicator of a poor prognosis. MK may have a role in the pathogenesis of RA via induction of inflammatory mediators.

Intra-Articular Injection of Cross-Linked Hyaluronic Acid-Dexamethasone Hydrogel Attenuates Osteoarthritis: An Experimental Study in a Rat Model of Osteoarthritis.

Cross-linked hyaluronic acid hydrogel (cHA gel) and dexamethasone (Dex) have been used to treat knee osteoarthritis (OA) in clinical practice owing to their chondroprotective and anti-inflammatory effects, respectively. The aim of the present study was to compare the treatment effects of the cHA gel pre-mixed with/without Dex in a surgery-induced osteoarthritis model in rats. Anterior cruciate ligament transection (ACLT) surgery was performed on the right knee of rats to induce OA. Male 2-month-old Sprague-Dawley rats were randomly divided into five groups (n = 10/per group): (1) ACLT + saline; (2) ACLT + cHA gel; (3) ACLT + cHA-Dex (0.2 mg/mL) gel; (4) ACLT + cHA-Dex (0.5 mg/mL) gel; (5) Sham + saline. Intra-joint injections were performed four weeks after ACLT in the right knee. All animals were euthanized at 12 weeks post-surgery. Cartilage damage and changes in the synovial membrane were assessed by micro X-ray, Indian ink articular surface staining, Safranin-O/Fast Green staining, immunohistochemistry, hematoxylin and eosin staining of the synovial membrane, and quantitative reverse transcription-polymerase chain reaction for changes in gene expression. Micro X-ray revealed that the knee joint treated with the cHA-Dex gel was wider than those treated with cHA gel alone or saline. The cHA-Dex gel group had less Indian ink staining (indicator of cartilage fibrillation) than the cHA gel or saline injection groups. Safranin-O/Fast Green staining indicated that increased proteoglycan staining and less cartilage damage were found in the cHA-Dex gel group compared with the cHA gel or saline injection groups. Quantification of histology findings from saline, cHA gel, cHA-Dex (0.2 mg/mL) gel, cHA-Dex (0.5 mg/mL) gel, and sham groups were 5.84 ± 0.29, 4.50 ± 0.87, 3.00 ± 1.00, 2.00 ± 0.48, and 0.30 ± 0.58 (p < 0.05), respectively. A strong staining of type II collagen was found in both the cHA-Dex gel groups compared with saline group or cHA alone group. Similar result was found for the mRNA level of aggrecan and opposite result for type X collagen. Hematoxylin and eosin staining in the synovial membrane showed less synovial lining cell layers and reduced inflammatory cell infiltration in cHA-Dex gel-treated animals compared with saline or cHA only groups. Altogether, cHA-Dex gel has better chondroprotective and anti-inflammatory effects in rat surgery-induced osteoarthritis than cHA alone.

CTGF promotes articular damage by increased proliferation of fibroblast-like synoviocytes in rheumatoid arthritis

Objectives: Fibroblast-like synoviocytes (FLS) are a major component of the hyperplastic synovial pannus, which aggressively invades cartilage and bone during the course of rheumatoid arthritis (RA). Connective tissue growth factor (CTGF or CCN2) is a product of a growth factor-inducible immediate early gene and is involved in cell adhesion, proliferation, and differentiation. However, the role that CTGF plays in FLS proliferation has remained undetermined. The aim of this study was to identify the role of CTGF in regulating the proliferation of FLS derived from patients with RA.Method: CTGF levels in serum and synovial fluid (SF) were determined by enzyme-linked immunosorbent assay (ELISA). Expression of CTGF in FLS was determined using reverse transcription polymerase chain reaction (RT-PCR). FLS proliferation stimulated by CTGF was measured by thymidine incorporation. The influence of CTGF small interfering RNA (siRNA) on FLS apoptosis was detected by flow cytometry.Results: CTGF was overexpressed in serum and SF samples from RA patients compared with samples from normal controls. Elevated levels of CTGF in RA SF promoted the proliferation of FLS. Furthermore, in samples from RA patients, CTGF was found to protect FLS from apoptosis and to sustain the expression of survivin in FLS. The expression of CTGF in FLS can be up-regulated by tumour necrosis factor (TNF)-α.Conclusions: Our findings indicate that CTGF plays a crucial role in the proliferation of FLS in RA and probably contributes to synovial lining cell hyperplasia and eventually to joint destruction in patients with RA.

Effect of Toll-Like Receptor 4 on Synovial Injury of Temporomandibular Joint in Rats Caused by Occlusal Interference.

Synovitis is an important disease that causes intractable pain in TMJ. Some investigations suggested that the increasing expression of IL-1β secreted by synovial lining cells plays an important role in synovial inflammation and cartilage destruction in TMJ. In our previous research, the results demonstrated that TLR4 is involved in the expression of IL-1β in SFs from TMJ with lipopolysaccharide stimulation. However, the inflammatory response that occurred in synovial membrane is not caused by bacterial infection. In the current study, we investigated whether or not TLR4 participates in the inflammatory responses and the expression of IL-1β in synovial membrane of rats induced by occlusal interference. The results showed that obvious inflammation changes were observed in the synovial membranes and the expression of TLR4 and IL-1β was increased at both mRNA and protein levels in the occlusal interference rats. In addition, the inflammation reactions and the increased expression of IL-1β could be restrained by treatment with TAK-242, a blocker of TLR4 signaling. The results prompted us that the activation of TLR4 may be involved in the inflammatory reactions and increased expression of IL-1β in patients with synovitis and participate in the mechanisms of the initiation and development of synovial injury by regulating the expression of inflammatory mediators like IL-1β in synovial membranes.

Contribution of synovial lining cells to synovial vascularization of the rat temporomandibular joint.

The lining layer of the synovial membrane in the temporomandibular joint (TMJ) contains two types of lining cells: macrophage-like type A and fibroblast-like type B cells. The type B cells are particularly heterogeneous in their morphology and immunoreactivity, so that details of their functions remain unclear. Some of the type B cells exhibit certain resemblances in their ultrastructure to those of an activated capillary pericyte at the initial stage of the angiogenesis. The articular surface, composed of cartilage and the disc in the TMJ, has few vasculatures, whereas the synovial lining layer is richly equipped with blood capillaries to produce the constituent of synovial fluid. The present study investigated at both the light and electron microscopic levels the immunocytochemical characteristics of the synovial lining cells in the adult rat TMJ, focusing on their contribution to the synovial vascularization. It also employed an intravascular perfusion with Lycopersicon esculentum (tomato) lectin to identify functional vessels invivo. Results showed that several type B cells expressed desmin, a muscle-specific intermediate filament which is known as the earliest protein to appear during myogenesis as well as being a marker for the immature capillary pericyte. These desmin-positive type B cells showed immunoreactions for vimentin and pericyte markers (neuron-glial 2; NG2 and PDGFRβ) but not for the other markers of myogenic cells (MyoD and myogenin) or a contractile apparatus (αSMA and caldesmon). Immunoreactivity for RECA-1, an endothelial marker, was observed in the macrophage-like type A cells. The arterioles and venules inside the synovial folds extended numerous capillaries with RECA-1-positive endothelial cells and desmin-positive pericytes to distribute densely in the lining layer. The distal portion of these capillaries showing RECA-1-immunoreactivity lacked lectin-staining, indicating a loss of blood-circulation due to sprouting or termination in the lining layer. The desmin-positive type B and RECA-1-positive type A cells attached to this portion of the capillaries. Some capillaries in the lining layer also expressed ninein, a marker for sprouting endothelial cells, called tip cells. Since an activated pericyte, macrophage and tip cell are known to act together at the forefront of the vessel sprout during angiogenesis, the desmin-positive type B cell and RECA-1-positive type A cell might serve as these angiogenic cells in the synovial lining layer. Tomato lectin perfusion following decalcification would be a highly useful tool for research on the vasculature of the mineralized tissue. Use of this technique combined with immunohistochemistry should permit future extensive investigations on the presence of the physiological angiogenesis and on the function of the lining cells in the synovial membrane.