The effects of synovial fluid macrophages and interleukin-1 on hyaluronic acid synthesis by normal synovial fibroblasts

Cartilage Wear Particles Induce an Inflammatory Response Similar to Cytokines in Human Fibroblast-Like Synoviocytes

The synovium plays a key role in the development of osteoarthritis, as evidenced by pathological changes to the tissue observed in both early and late stages of the disease. One such change is the attachment of cartilage wear particles to the synovial intima. While this phenomenon has been well observed clinically, little is known of the biological effects that such particles have on resident cells in the synovium. The present work investigates the hypothesis that cartilage wear particles elicit a pro-inflammatory response in diseased and healthy human fibroblast-like synoviocytes, like that induced by key cytokines in osteoarthritis. Fibroblast-like synoviocytes from 15 osteoarthritic human donors and a subset of three non-osteoarthritic donors were exposed to cartilage wear particles, interleukin-1α or tumor necrosis factor-α for 6 days and analyzed for proliferation, matrix production, and release of pro-inflammatory mediators and degradative enzymes. Wear particles significantly increased proliferation and release of nitric oxide, interleukin-6 and -8, and matrix metalloproteinase-9, -10, and -13 in osteoarthritic synoviocytes, mirroring the effects of both cytokines, with similar trends in non-osteoarthritic cells. These results suggest that cartilage wear particles are a relevant physical factor in the osteoarthritic environment, perpetuating the pro-inflammatory and pro-degradative cascade by modulating synoviocyte behavior at early and late stages of the disease. Future work points to therapeutic strategies for slowing disease progression that target cell-particle interactions. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1979-1987, 2019.

A Functional Tissue-Engineered Synovium Model to Study Osteoarthritis Progression and Treatment

IMPACT STATEMENT

The synovium envelops the diarthrodial joint and plays a key regulatory role in defining the composition of the synovial fluid through filtration and biosynthesis of critical boundary lubricants. Synovium changes often precede cartilage damage in osteoarthritis. We describe a novel in vitro tissue engineered model, validated against native synovium explants, to investigate the structure-function of synovium through quantitative solute transport measures. Synovium was evaluated in the presence of a proinflammatory cytokine, interleukin-1, or the clinically relevant corticosteroid, dexamethasone. We anticipate that a better understanding of synovium transport would support efforts to develop more effective strategies aimed at restoring joint health.

Toward understanding the role of cartilage particulates in synovial inflammation

OBJECTIVE

Arthroscopy with lavage and synovectomy can remove tissue debris from the joint space and the synovial lining to provide pain relief to patients with osteoarthritis (OA). Here, we developed an in vitro model to study the interaction of cartilage wear particles with fibroblast-like synoviocytes (FLS) to better understand the interplay of cartilage particulates with cytokines on cells of the synovium.

METHOD

In this study sub-10 μm cartilage particles or 1 μm latex particles were co-cultured with FLS ±10 ng/mL interleukin-1α (IL-1α) or tumor necrosis factor-α (TNF-α). Samples were analyzed for DNA, glycosaminoglycan (GAG), and collagen, and media samples were analyzed for media GAG, nitric oxide (NO) and prostaglandin-E2 (PGE2). The nature of the physical interaction between the particles and FLS was determined by microscopy.

RESULTS

Both latex and cartilage particles could be phagocytosed by FLS. Cartilage particles were internalized and attached to the surface of both dense monolayers and individual cells. Co-culture of FLS with cartilage particulates resulted in a significant increase in cell sheet DNA and collagen content as well as NO and PGE2 synthesis compared to control and latex treated groups.

CONCLUSION

The proliferative response of FLS to cartilage wear particles resulted in an overall increase in extracellular matrix (ECM) content, analogous to the thickening of the synovial lining observed in OA patients. Understanding how cartilage particles interface with the synovium may provide insight into how this interaction contributes to OA progression and may guide the role of lavage and synovectomy for degenerative disease.

Intracellular signal transduction for serum activation of the hyaluronan synthase in eukaryotic cell lines

Hyaluronan synthase was activated in B6 cells or 3T3 fibroblasts by foetal calf serum with maximal activity after 6 h. Activation was inhibited by cycloheximide or by the protein kinase inhibitors H-7 or H-8, indicating that transcription as well as phosphorylation was required for activation. The activation by serum was markedly prolonged, when serum was added together with cholera toxin or theophylline. Without serum stimulation the hyaluronan synthase could also be activated by phorbol-12-myristate-13-acetate, by dibutyryl-c-AMP, or by forskolin. Increasing the intracellular Ca-ion concentration with a Ca-ionophore also led to an activation. The activation of the drugs was not synergistic. In isolated plasma membranes the synthase activity could be decreased by phosphatase treatment and enhanced by ATP in B6 cells and by ATP in the presence of phorbol-12-myristate-13-acetate in 3T3 fibroblasts. Stimulation correlated with increased transcription and phosphorylation of the 52 kD hyaluronan synthase at serine residues. The results led to the conclusion that hyaluronan synthase is induced by transcription and activated by phosphorylation by protein kinase C, c-AMP-dependent protein kinases, or Ca-ion-dependent protein kinases.

The glycosaminoglycans in cultures of stimulated rat peritoneal macrophages. 2. Gel chromatographic studies and the behaviour of heparan sulfate

The molecular weight distribution of pMP-derived glycosaminoglycans (GAG), i.e. non-sulfated GAG, chondroitin sulfate (CS), and heparin sulfate (HS)-like material was determined. The peritoneal macrophages (pMP) were harvested from rats normal or stimulated by i.p. injection of thioglycolate, carrageenan or BCG, and maintained in culture. The GAG of cell layer and medium were isolated separately after labeling with 35S-sulfate and 3H-acetate. Treatment with nitrous acid served to remove HS-like material. Labeling with 3H-acetate served to detect synthesis of the high m. w. hyaluronic acid (HA). Gel chromatic separation was done using Sephadex G-200 columns. The maximal size of 35S-labeled GAG, especially HS (36 kDa), was reduced in cultural medium and cell layer after stimulation in vivo. Reduction was most pronounced after application of carrageenan followed by thioglycolate and BCG/LPS stimulation. The extracellular GAG of BCG-stimulated pMP were smallest, probably due to degradation. Heparan sulfate-like material made up a larger proportion in monolayer and medium, comprising the total m.w. range up to 36 kDa. The GAG sensitive to nitrous acid were maximal in cultures of carrageenan-stimulated pMP and minimal in those of thioglycolate-stimulated pMP. This type of HS was sensitive to hyaluronidase, too. Any synthesis of high molecular hyaluronic acid was not found in normal or stimulated rat pMP. Therefore MP-associated HA must be adsorbed from other sources or synthesized by early forms of macrophages.

Does hyaluronan have a role in endothelial cell proliferation of the synovium?

Hyaluranate (HA) is a major constituent of synovial fluid, but its concentration and molecular size differ in normal and inflamed joints. HA can induce or inhibit angiogenesis depending on both its size and its concentration. Endothelial-cell endocytose-labeled macromolecular HA and HA oligosaccharides and binding studies have identified an HA-specific receptor on the endothelial cell surface (KD, 10(-10) mol/L; approximately 2,000/cell). The molecular weight of HA-binding proteins was found to be 90 to 125, 78, and 46 kd.

Evaluation of sodium hyaluronate therapy in induced septic arthritis in the horse

This study was conducted to determine the efficacy of sodium hyaluronate (SH) with antibiotic therapy and joint lavage for reducing acute inflammatory and degenerative changes induced by septic arthritis. Septic arthritis was induced in six adult horses by inoculating the tarsocrural joints with 1 x 10(4) colony-forming units of Staphylococcus aureus. When clinical signs appeared, trimethoprim-sulphamethoxazole (30 mg/kg bodyweight [bwt] daily) and phenylbutazone (4.4 mg/kg bwt sid) were administered and continued until termination of the study (Treatment Day 18). Twenty-four hours post inoculation, all joints were lavaged with sterile lactated Ringer's solution. Following lavage, one joint of each horse was injected with 10 mg of SH, and the contralateral joint served as the control. Sodium hyaluronate treated joints showed significant reductions in lameness, tarsal circumference and synovial fluid protein and WBC concentrations. The synovial membrane of the SH-treated joints contained less cellular infiltrate, less granulation tissue formation and retained a more normal villous structure compared with controls. The total glycosaminoglycan loss from the articular cartilage in the SH treated joints was consistently less than that from the control joints; however, this difference was not statistically significant. Sodium hyaluronate with joint lavage appears to be more beneficial than lavage alone for treatment of septic arthritis.

Effect of interleukin-1 on hyaluronate synthesis by synovial fibroblastic cells

Interleukin-1 (IL-1) stimulates fibroblast-mediated hyaluronate (HA) synthesis in vitro. In the present study the degree of polymerization of such HA was studied using HPLC (high performance liquid chromatography) with a size exclusion column combined with 125I-HABP assay used to measure the HA concentration in various HA molecular weight fractions separated using HPLC. IL-1 stimulated HA was more polydisperse than that produced by resting fibroblasts with a molecular weight varying from more than 4 x 10(6) daltons to less than 7.1 x 10(3) daltons. This IL-1 effect may contribute to the low molecular weight HA produced by freshly explanted arthritic synovial tissue and to the low viscosity of arthritic synovial fluid in vivo.

Inflammation and cartilage metabolism in rheumatoid arthritis. Studies of the blood markers hyaluronic acid, orosomucoid, and keratan sulfate

Single analyses of peripheral blood of rheumatoid arthritis (RA) patients showed a significant reduction in the mean value for keratan sulfate (KS) compared with that in control subjects, but the mean value for orosomucoid (OM) was elevated compared with that in control subjects. Some RA patients displayed highly elevated levels of hyaluronic acid (HA), while others exhibited normal levels. There was a significant inverse correlation between OM and KS content in RA patients, as well as a direct correlation between HA and OM. In longitudinal studies of RA patients, parallel changes in OM and HA and inverse changes between KS and OM or HA were commonly observed. Clinical analyses revealed that there was an inverse correlation between KS and morning stiffness, and direct correlations between the number of tender joints and HA, and between HA or the erythrocyte sedimentation rate and the number of joints with effusions. The reason(s) for the inverse correlation between KS and OM as an index of systemic inflammation remains to be established. Circulating HA represents an index of joint inflammation, for which a marker has not been previously available.

Stimulation of the hyaluronic acid levels of human synovial fibroblasts by recombinant human tumor necrosis factor alpha, tumor necrosis factor beta (lymphotoxin), interleukin-1 alpha, and interleukin-1 beta

Monocyte/macrophage polypeptides (monokines) alter the properties of synovial cells. This interaction could explain some of the properties of the inflamed synovium in rheumatic disease. Only recently has it been possible to test the action of purified monokines on the target synovial cells. We report here that recombinant human tumor necrosis factor alpha, tumor necrosis factor beta (lymphotoxin), interleukin-1 alpha, and interleukin-1 beta stimulate the hyaluronic acid (HA) levels of human synovial fibroblast-like cells. The effect of monokines was generally inhibited by indomethacin, suggesting the involvement of an endogenous cyclooxygenase product in the stimulation, and by the glucocorticoid, dexamethasone. In contrast, all-trans-retinoic acid stimulated synovial cell plasminogen activator activity but did not increase the HA levels. These findings could help to explain the raised HA levels found in the joint fluids and in the circulation of patients with rheumatic disease.

Activated monocytes induce arthritis-associated changes in mitochondria of cultured synovial fibroblasts

We have recently shown that synovial fibroblasts cultured from patients with reactive or rheumatoid arthritis exhibit increased autofluorescence when compared with controls. Morphological studies suggested that this increase was related to the anomalous structure of mitochondria in cells cultured from rheumatoid or non-rheumatoid inflammatory synovial tissue. The present study describes attempts to find an explanation for these observations. The effects of conditioned media of cultured mononuclear cells were tested on normal synovial fibroblasts. Conditioned media of monocytes stimulated with lipopolysaccharide or poly-IC induced an increase in the cellular autofluorescence and changes in the morphology of mitochondria in normal fibroblasts. These changes were indistinguishable from those seen in synovial fibroblasts cultured from various arthritides. Indomethacin or gold salts did not abolish the effects of monocyte-conditioned media. Abnormal mitochondria could not be induced in the presence of cycloheximide. This study describes a new aspect of monocyte-fibroblast interactions during rheumatoid and non-rheumatoid inflammation of synovial tissue.