The nature and designation of osteoarthritis determined by its histopathology

Specimens of synovial tissue and articular cartilage removed at operations of patients with primary degenerative joint disease were scrutinized for defined histopathological parameters. The findings in the synovial membrane were subsequently compared as to frequency and intensity with identical parameters ascertained in specimens removed from patients with definite rheumatoid arthritis. These examinations disclosed the presence of synovial inflammatory features, although at lesser incidence and intensity than in rheumatoid arthritis; therefore the designation of arthritis is indicated. On the basis of the concurrently examined tissue specimens of the articular cartilage, and in consensus with the generally acknowledged start of the degenerative joint disease by disintegrating changes in the articular cartilage, the prefix of chondrosis is appropriate.     

Contribution of synovial mesenchymal cells to the pathogenesis of rheumatoid arthritis.

Rheumatoid joint destruction is caused by (1) enzymatic digestion from articular surfaces of cartilage, (2) pannus formation, and (3) lysis of the matrix by activated chondrocytes. Pannus, a vascular and fibrous granulation tissue arising from the perichondral synovial membrane, extends onto cartilage surfaces as a layer of morphologically quiescent fibroblastic mesenchymal cells. Pannus subsequently starts invasion into cartilage matrix with the appearance of macrophagelike cells. Synovial mesenchymal cells are thought to play important roles in the pathogenesis of rheumatoid joint destruction in relation to la expression and antigen presentation as well as the elaboration of inflammatory cytokines such as interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha. By experimentally inducing antigen-induced arthritis in H-2-c-fos transgenic mice whose immunoglobulin G antibody response against immunizing antigen was defective, the investigators produced destructive arthritis without lymphocyte infiltration. The only cells invading the joints in these mice were similar to a previously recognized subset of human synovial cells that had a mesenchymal appearance. These mesenchymal cells invaded the cartilage matrix upon in vitro culture. The role of synovial mesenchymal cells in the pathogenesis of rheumatoid joint destruction is discussed.     

Appearance of calpain correlates with arthritis and cartilage destruction in collagen induced arthritic knee joints of mice.

OBJECTIVES--To determine the relevance of calpain in murine collagen induced arthritis (CIA) and to correlate the presence of m-calpain with the appearance of arthritis and cartilage destruction. METHODS--The immunohistochemical appearance and localisation of m-calpain at different stages of arthritis were analysed and compared with the histological changes occurring during type II CIA. The arthritic knee joint lavage was also examined for m-calpain by immunoelectrophoretic blotting. RESULTS--Immunohistochemical staining demonstrated a clear positive correlation between the appearance of m-calpain and both a histological grade of arthritis and an acute phase of cartilage destruction. Further development of the disease showed continual presence of m-calpain but with reduced intensity. Intra-articular inflammatory cells (mainly polymorphonuclear leucocytes, synovial lining cells, and sublining fibroblasts) were found to be the most positively stained, but extracellular localisation of m-calpain on the surface of cartilage and synovium, and in the articular cartilage matrix and chondrocyte lacunae, was also observed. In the knee joint lavage obtained at the most intensive stage of acute arthritis, m-calpain was detectable by immunoelectrophoretic blotting. CONCLUSIONS--The findings suggest that m-calpain may act at an early phase of CIA as a matrix proteinase and take part in the destruction of articular cartilage or activate other destructive enzymes.     

Synovial fluid analysis of two groups of proteoglycan epitopes distinguishes early and late cartilage lesions.

OBJECTIVE. To investigate whether fragmentation of proteoglycans in arthritis results in domains that have different levels of release from cartilage at different stages of the disease. METHODS. Two regions of the proteoglycan, the hyaluronan-binding region and the glycosaminoglycan-rich region of the core protein, were measured, by immunoassay, in knee joint synovial fluids of patients with rheumatoid arthritis or reactive arthritis. RESULTS. Synovial fluid concentrations of the glycosaminoglycan-rich region were highest in rheumatoid arthritis patients who had little cartilage damage as determined by radiography, whereas release of the hyaluronan-binding region predominated in patients with advanced cartilage destruction. In reactive arthritis, release of the glycosaminoglycan-rich region predominated. CONCLUSION. These findings indicate that the hyaluronan-binding region is initially retained in the tissue during the development of cartilage destruction. The combined analysis of these markers offers a new avenue for assessment of the degree of cartilage damage in arthritis.     

Subtyping of osteoarthritic synoviopathy

OBJECTIVE: Osteoarthritis research is traditionally concentrating on events within the degenerated articular cartilage. Changes in the synovial membrane are largely neglected. In fact, they are generally interpreted as secondary to the cartilage changes and not pathogenetically involved in the disease process. In this study, we present a systematic analysis of the synovial reaction pattern in early and late stages of the osteoarthritic disease process. METHODS: A large series of synovial specimens derived from early and late stage osteoarthritic cartilage disease were investigated by histological and immunohistochemical means for tissue architecture and inflammatory cell infiltrates. For comparison, also samples with rheumatoid arthritis, seronegative arthritis, and septic arthritis were included as well as normal synovial membrane specimens. RESULTS: In all specimens derived from patients with diagnosed osteoarthritis alterations of the synovial tissue were observed. A large spectrum of alterations was found in different stages of osteoarthritic joint disease and four different basic pattern of synovial reactions could be identified: (i) hyperplastic, (ii) inflammatory, (iii) fibrotic, and (iv) detritus-rich synoviopathy. CONCLUSION: We show that in all cases of clinically overt osteoarthritic joint disease significant synovial pathology is associated. Furthermore, our study clearly documents that in osteoarthritic synovium significant inflammation can occur. This is suggestive of a distinct pathogenetic role of the synovium also in osteoarthritic cartilage degeneration at least in a subset of cases.     

A new model for rheumatoid arthritis generated by engraftment of rheumatoid synovial tissue and normal human cartilage into scid mice

Objective. A new animal model was used to study the interaction between rheumatoid synovial cells and cartilage and to explore the cellular basis of rheumatoid joint destruction. Methods. Fresh synovial tissue derived from patients with rheumatoid arthritis was implanted with normal human cartilage into SCID mice, either subcutaneously or under the renal capsule, for up to 304 days. The implants were analyzed by light and electron microscopy, as well as by immunohistochemistry and in situ hybridization. Results. Human synovial tissue and cartilage implanted in SCID mice are maintained by the animals for up to 304 days. After 35 days, focal erosions occur at the site of attachment of synovial lining cells to the cartilage. After 105 days, a pannus-like formation, consisting of proliferating synovial fibroblast-like cells invading the cartilage, is observed. The fibroblast nature of these cells was supported by observation of only focal expression of the macrophage markers CD14 and CD68. Cells at the immediate site of cartilage destruction express messenger RNA for cathepsin L, whereas cathepsin D messenger RNA was detected in subsynovial regions away from the site of destruction. The human origin of the tissue involved in cartilage destruction was demonstrated using monoclonal antibodies to HLA-ABC and human type IV collagen. Conclusion. The present approach introduces a novel in vivo model of rheumatoid arthritis for the study of the molecular and cellular mechanisms of rheumatoid joint destruction at sites of synovial attachment to cartilage. In this model, the SCID mouse acts as a useful host for studying the properties of rheumatoid synovium in the absence of circulating human blood components.     

血清软骨寡聚基质蛋白检测在关节炎患者中的意义研究

目的 探讨血清软骨寡聚基质蛋白(COMP)在各类关节炎患者中的差别及对类风湿关节炎(RA)软骨破坏放射学改变的早期预测价值.方法 采用酶联免疫吸附试验(ELISA)方法测定并对比分析154例各类关节炎患者血清COMP水平的差异,RA患者各项临床指标及2年后关节放射学改良SHARP(vdH-Sharp)指数评分与COMP行相关性分析.结果 与仅有滑膜损害的其他关节炎患者及正常人群比较,RA患者血清COMP显著升高(P＜0.05).骨关节炎(OA)、银屑病关节炎(PSA)患者与正常人群比较血清COMP亦有差异,而与其他滑膜关节炎患者比较差异不大.RA、OA、PSA患者间血清COMP值比较差异无统计学意义.RA患者2年随访发现COMP与患者关节X线的改良SHARP评分前后差值呈正相关(P＜0.01,r=0.848).但与初诊时的抗环瓜氨酸肽(CCP)抗体、类风湿因子(RF)、关节功能、改良SHARP评分均无相关性,与初诊时的红细胞沉降率(ESR)、C反应蛋白(CRP)、晨僵时间、关节肿胀、压痛指数相关(P＜0.05).结论 COMP在各类软骨受侵犯关节炎尤其是RA患者血清中异常增高,提示其可为RA软骨病变早期诊断及判断软骨病变进展、预后和治疗效果的一项理想指标.     

Synovial fluid analysis of two groups of proteoglycan epitopes distinguishes early and late cartilage lesions

Objective. To investigate whether fragmentation of proteoglycans in arthritis results in domains that have different levels of release from cartilage at different stages of the disease. Methods. Two regions of the proteoglycan, the hyaluronan-binding region and the glycosaminoglycanrich region of the core protein, were measured, by immunoassay, in knee joint synovial fluids of patients with rheumatoid arthritis or reactive arthritis. Results. Synovial fluid concentrations of the glycosaminoglycan-rich region were highest in rheumatoid arthritis patients who had little cartilage damage as determined by radiography, whereas release of the hyaluronan-binding region predominated in patients with advanced cartilage destruction. In reactive arthritis, release of the glycosaminoglycan-rich region predominated. Conclusion. These findings indicate that the hyaluronan-binding region is initially retained in the tissue during the development of cartilage destruction. The combined analysis of these markers offers a new avenue for assessment of the degree of cartilage damage in arthritis.     

Angiogenesis and rheumatoid arthritis: pathogenic and therapeutic implications.

Rheumatoid arthritis can be considered as one of the family of 'angiogenesis dependent diseases'. Angiogenesis in rheumatoid arthritis is controlled by a variety of factors found in the synovial fluid and pannus tissue. Modulation of the angiogenic component of the disease may alter the pathogenesis of the condition, and subsequent cartilage and joint destruction, by reducing the area of the endothelium in the pannus and restricting pannus growth. Current therapeutic strategies exert, to varying extents, an inhibitory effect on the angiogenic process. In particular, the mode of action of the slow acting antirheumatic drugs may be due to their effect on the angiogenic response. The development of novel angiostatic treatments for chronic inflammatory joint disease may lead to a new therapeutic approach in controlling disease progression.     

Etiopathogenesis of the rheumatoid arthritis-like disease in MRL/l mice. I. The histomorphologic basis of joint destruction

MRL/l mice spontaneously develop a hindlimb arthropathy, as well as a number of immunologic abnormalities, including circulating rheumatoid factors. Although previous studies have suggested that this arthropathy is primarily an inflammatory process, we performed a comprehensive histomorphologic study which indicated that inflammation is a late manifestation of MRL/l arthritis. The pathologic changes that occur in the joints of these mice can be divided into 3 stages. The first stage develops between the ages of 7 and 13 weeks and consists of synovial cell proliferation in the joint recesses. The second stage is characterized by continued proliferation of synovial cells which take on an appearance similar to that of transformed mesenchymal cells. The earliest destructive changes occur in the second stage and include marginal erosions, followed soon after by progressive destruction of articular and meniscal cartilage. The final stage is characterized by a diminution of synovial cel proliferation, extensive cartilage destruction, formation of scar tissue and fibrocartilage, and a very moderate infiltration of the synovial stroma by mononuclear and polymorphonuclear inflammatory cells. Throughout the disease progression there is a striking dissociation between inflammatory cell infiltration or exudation and tissue destruction. The histomorphologic similarities between human rheumatoid synovitis and the arthritis of MRL/l mice, as well as the presence of rheumatoid factors, make this mouse strain an excellent model for studying human rheumatoid arthritis.     

Etiopathogenesis of the rheumatoid arthritis–like disease in MRL/1 mice. I. The histomorphologic basis of joint destruction

MRL/1 mice spontaneously develop a hindlimb arthropathy, as well as a number of immunologic abnormalities, including circulating rheumatoid factors. Although previous studies have suggested that this arthropathy is primarily an inflammatory process, we performed a comprehensive histomorphologic study which indicated that inflammation is a late manifestation of MRL/1 arthritis. The pathologic changes that occur in the joints of these mice can be divided into 3 stages. The first stage develops between the ages of 7 and 13 weeks and consists of synovial cell proliferation in the joint recesses. The second stage is characterized by continued proliferation of synovial cells which take on an appearance similar to that of transformed mesenchymal cells. The earliest destructive changes occur in the second stage and include marginal erosions, followed soon after by progressive destruction of articular and meniscal cartilage. The final stage is characterized by a diminution of synovial cell proliferation, extensive cartilage destruction, formation of scar tissue and fibrocartilage, and a very moderate infiltration of the synovial stroma by mononuclear and polymorphonuclear inflammatory cells. Throughout the disease progression there is a striking dissociation between inflammatory cell infiltration or exudation and tissue destruction. The histomorphologic similarities between human rheumatoid synovitis and the arthritis of MRL/1 mice, as well as the presence of rheumatoid factors, make this mouse strain an excellent model for studying human rheumatoid arthritis.     

Osteopontin deficiency protects joints against destruction in anti-type II collagen antibody-induced arthritis in mice

Rheumatoid arthritis is one of the most critical diseases that impair the quality of life of patients, but its pathogenesis has not yet been fully understood. Osteopontin (OPN) is an extracellular matrix protein containing Arg-Gly-Asp (RGD) sequence, which interacts with alpha(v)beta3 integrins, promotes cell attachment, and cell migration and is expressed in both synovial cells and chondrocytes in rheumatoid arthritis; however, its functional relationship to arthritis has not been known. Therefore, we investigated the roles of OPN in the pathogenesis of inflammatory process in a rheumatoid arthritis model induced by a mixture of anti-type II collagen mAbs and lipopolysaccharide (mAbs/LPS). mAbs/LPS injection induced OPN expression in synovia as well as cartilage, and this expression was associated with joint swelling, destruction of the surface structures of the joint based on scanning electron microscopy, and loss of toluidine blue-positive proteoglycan content in the articular cartilage in wild-type mice. In contrast, OPN deficiency prevented the mice from such surface destruction, loss of proteoglycan in the articular joint cartilage, and swelling of the joints even when the mice were subjected to mAbs/LPS injection. Furthermore, mAbs/LPS injection in wild-type mice enhanced the levels of CD31-positive vessels in synovia and terminal deoxynucleotidyltransferase-mediated UTP end labeling-positive chondrocytes in the articular cartilage, whereas such angiogenesis as well as chondrocyte apoptosis was suppressed significantly in OPN-deficient mice. These results indicated that OPN plays a critical role in the destruction of joint cartilage in the rheumatoid arthritis model in mice via promotion of angiogenesis and induction of chondrocyte apoptosis.     

Magnetic resonance imaging in patients with inflammatory arthritis of the knee

Summary Magnetic resonance imaging (MRI) permits visualization of anatomic structures not appreciated by conventional radiographic imaging and may quantify inflammatory disease and its progression with greater sensitivity than available techniques. We therefore compared MRIwith clinical evaluation and with radiographic examination of 17 patients with inflammatory arthritis of the knee. We sought to determine anatomic integrity of bone, cartilage, menisci, and ligaments, and to quantify joint effusion and synovial proliferation. Patients studied had rheumatoid arthritis (10patients), juvenile rheumatoid arthritis (4patients), ankylosing spondylitis (1 patient), and monoarticular arthritis (2 patients). In all patients MRI revealed clinically important abnormalities not detected by physical or conventional radiographic exams. These included proliferative synovitis (13 patients), cartilage thinning (2 patients), cartilage erosion (8 patients), bone infarction (1 patient), meniscal injury (1 patient), and synovial invagination into bone (1 patient). Also MRI indicated inflammatory disease to be quantitatively greater than had been appreciated on clinical examination or routine X-ray studies-proliferative synovitis (12 patients), erosion (7 patients), effusion (8 patients), cartilage thinning (11 patients), and ligamentous/meniscal damage (1 patient). These findings led to reassessment of anatomic staging and influenced therapeutic decision for these patients. Thus MRI provides clinically important information about joint integrity and inflammatory disease, with a sensitivity and resolution considerably beyond conventional techniques.     

Therapeutic effect of cortistatin on experimental arthritis by downregulating inflammatory and Th1 responses

BACKGROUND: Rheumatoid arthritis is a chronic autoimmune disease of unknown aetiology characterised by chronic inflammation in the joints and subsequent destruction of the cartilage and bone. Aim: To propose a new strategy for the treatment of arthritis based on the administration of cortistatin, a newly discovered neuropeptide with anti-inflammatory actions. METHODS: DBA/1J mice with collagen-induced arthritis were treated with cortistatin after the onset of disease, and the clinical score and joint histopathology were evaluated. Inflammatory response was determined by measuring the levels of various inflammatory mediators (cytokines and chemokines) in joints and serum. T helper cell type 1 (Th1)-mediated autoreactive response was evaluated by determining the proliferative response and cytokine profile of draining lymph node cells stimulated with collagen and by assaying the content of serum autoantibodies. RESULTS: Cortistatin treatment significantly reduced the severity of established collagen-induced arthritis, completely abrogating joint swelling and destruction of cartilage and bone. The therapeutic effect of cortistatin was associated with a striking reduction in the two deleterious components of the disease-that is, the Th1-driven autoimmune and inflammatory responses. Cortistatin downregulated the production of various inflammatory cytokines and chemokines, decreased the antigen-specific Th1-cell expansion, and induced the production of regulatory cytokines, such as interleukin 10 and transforming growth factor beta1. Cortistatin exerted its effects on synovial cells through both somatostatin and ghrelin receptors, showing a higher effect than both peptides protecting against experimental arthritis. CONCLUSION: This work provides a powerful rationale for the assessment of the efficacy of cortistatin as a novel therapeutic approach to the treatment of rheumatoid arthritis.     

Mammalian target of rapamycin signaling is crucial for joint destruction in experimental arthritis and is activated in osteoclasts from patients with rheumatoid arthritis

Objective

Activation of the mammalian target of rapamycin (mTOR) pathway is important for immune cell activation and bone metabolism. To date, the contribution of mTOR signaling to joint inflammation and structural bone and cartilage damage is unknown. The aim of this study was to investigate the potential of inhibiting mTOR as a treatment of inflammatory arthritis.

Methods

Human tumor necrosis factor–transgenic mice in which inflammatory arthritis was developing were treated with 2 different mTOR inhibitors, sirolimus or everolimus. The effects of treatment on clinical disease activity, inflammation, and localized joint and cartilage destruction were studied. In addition, the effects of mTOR inhibition on osteoclast survival and expression of key molecules of osteoclast function were analyzed in vitro. Moreover, synovial tissue from patients with rheumatoid arthritis (RA) was assessed for activation of the mTOR pathway.

Results

Inhibition of mTOR by sirolimus or everolimus reduced synovial osteoclast formation and protected against local bone erosions and cartilage loss. Clinical signs of arthritis improved after mTOR inhibition, and histologic evaluation showed a decrease in synovitis. In vitro, mTOR inhibition down‐regulated the expression of digestive enzymes and led to osteoclast apoptosis. Moreover, mTOR signaling was shown to be active in the synovial membrane of patients with RA, particularly in synovial osteoclasts.

Conclusion

Signaling through mTOR is an important link between synovitis and structural damage in inflammatory arthritis. Current pharmacologic inhibitors of mTOR could be effective in protecting joints against structural damage.

     

Mechanisms of tissue destruction and cellular activation in rheumatoid arthritis.

Rheumatoid arthritis is a chronic inflammatory disease of unknown etiology that is marked by synovial inflammation and destruction of articular extracellular matrix. Several studies of the pathogenesis of tissue destruction have focused on the production of metalloproteinases and their inhibitors in synovium as determinants of joint preservation. Also, the role of cytokines in the perpetuation of synovitis and of superantigens in synovial T-cell activation have led to novel hypotheses that attempt to explain abnormalities of synovial structure and function in rheumatoid arthritis. Recent studies that dealt with these topics are briefly reviewed in the context of current paradigms of inflammatory synovitis.     

Quantitative detection of keratan sulfate specific epitopes in synovial fluid in inflammatory and degenerative joint diseases

The release of keratan sulphate (KS) bearing proteoglycan fragments from the extracellular matrix of cartilage into the synovial fluid is believed to be an early event in most joint pathologies. Quantitative analysis of KS in body fluids is therefore regarded as having a certain potential in monitoring articular cartilage catabolism. We describe the application of a non-competitive enzyme linked immunosorbent assay (ELISA) for the quantitation of KS-epitope in synovial fluids, using a monoclonal anti-KS antibody. Synovial fluids from 75 patients were analyzed, comprising the following disease groups: i) rheumatoid arthritis (n = 42), ii) osteoarthritis (n = 20), iii) gouty arthritis (n = 5), and iv) reactive arthritis (Reiter's disease, n = 8). Highest concentrations of synovial KS-epitope were found in reactive arthritis (median = 1410 ng/ml), and in gouty arthritis (median = 2105 ng/ml). However, significantly lower concentrations of KS-epitope (p less than 0.01) were observed in synovial fluids from patients with rheumatoid arthritis (median = 197 ng/ml) and osteoarthritis (median = 337 ng/ml). Although considerable variation of individual values was observed in all groups, a weak and inverse correlation between synovial levels of KS-epitope and inflammatory disease activity was seen only in patients with rheumatoid arthritis. However, KS-epitope levels did not correlate with either the synovial IL-1 activity, nor the number of synovial leucocytes.     

Cytokines in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic disease characterized by synovial inflammation that leads to the destruction of cartilage and bone. In the last decade, there was a lot of successful research in the field of cytokine expression and regulation. It has become clear that pro- and antiinflammatory cytokines, derived predominantely from cells of macrophage lineage, play a major role in the initiation and perpetuation of the chronic inflammatory process in the RA synovial membrane. Monokines are abundant in rheumatoid synovial tissue, whereas low amounts of lymphokines are found. The involvement of pro-inflammatory cytokines, particularly interleukin (IL)-1 and tumor necrosis factor-alpha, in the pathogenesis of RA is well accepted. Recent data provide evidence that the pro-inflammatory cytokine IL-18 plays a crucial role in the development and sustenance of inflammatory joint diseases. There also appears to be a compensatory anti-inflammatory response in RA synovial membrane. It has become clear in the last few years that T cell-derived cytokines expressed preferentially by Th1 cells contribute to joint destruction and inflammation in RA. However, products from Th2 cells may be protective.