Synthesis of underpolymerized hyaluronic acid by fibroblasts cultured from rheumatoid and non-rheumatoid synovitis

Synovial fibroblasts in juvenile idiopathic arthritis: A scoping review

Synovial fibroblasts and their role in juvenile idiopathic arthritis have received limited attention compared to other immune mediated disease such as rheumatoid arthritis. Furthermore, no review exists regarding synovial fibroblasts, their interaction with immune cells and their potential involvement in juvenile idiopathic arthritis pathogenesis. This scoping review set out to identify and compile the current knowledge of all peer-reviewed studies on synovial fibroblasts from patients with juvenile idiopathic arthritis. The aim was to map the current knowledge and to produce a tool to assist future studies. The entire MEDLINE, EMBASE and Web of Science databases were used to identify all published studies in English regarding synovial fibroblasts from patients with juvenile idiopathic arthritis. We identified 18 eligible studies out of a total of 1778 screened entries. The majority of studies identified synovial fibroblast subsets or functional characteristics that may be involved in disease pathogenesis. We identified mechanisms of cell-cell interaction with leukocytes, pro-inflammatory signaling and unfavorable connective tissue homeostasis that may contribute to cartilage damage or bony overgrowth. All included studies identified mechanisms potentially linking synovial fibroblasts to specific disease traits in juvenile idiopathic arthritis. Most findings were similar to mechanisms also described in synovial fibroblast from adults with arthritis. However, the limited number of studies found identifies an unmet need for additional studies on synovial fibroblasts and their potential role in juvenile idiopathic arthritis.

Induction of CEMIP in Chondrocytes by Inflammatory Cytokines: Underlying Mechanisms and Potential Involvement in Osteoarthritis

In patients with osteoarthritis (OA), there is a decrease in both the concentration and molecular size of hyaluronan (HA) in the synovial fluid and cartilage. Cell migration-inducing hyaluronidase 1 (CEMIP), also known as hyaluronan (HA)-binding protein involved in HA depolymerization (HYBID), was recently reported as an HA depolymerization-related molecule expressed in the cartilage of patients with OA. However, the underlying mechanism of CEMIP regulation is not well understood. We found that CEMIP expression was transiently increased by interleukine-1β (IL-1β) stimulation in chondrocytic cells. We also observed that ERK activation and NF-κB nuclear translocation were involved in the induction of CEMIP by IL-1β. In addition, both administration of HA and mechanical strain attenuated the CEMIP induction in IL-1β-stimulated chondrocytes. In conclusion, we clarified the regulatory mechanism of CEMIP in chondrocytes by inflammatory cytokines and suggested the potential involvement in osteoarthritis development.

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.

Regulation of Hyaluronan (HA) Metabolism Mediated by HYBID (Hyaluronan-binding Protein Involved in HA Depolymerization, KIAA1199) and HA Synthases in Growth Factor-stimulated Fibroblasts

Regulation of hyaluronan (HA) synthesis and degradation is essential to maintenance of extracellular matrix homeostasis. We recently reported that HYBID (HYaluronan-Binding protein Involved in hyaluronan Depolymerization), also called KIAA1199, plays a key role in HA depolymerization in skin and arthritic synovial fibroblasts. However, regulation of HA metabolism mediated by HYBID and HA synthases (HASs) under stimulation with growth factors remains obscure. Here we report that TGF-β1, basic FGF, EGF, and PDGF-BB commonly enhance total amount of HA in skin fibroblasts through up-regulation of HAS expression, but molecular size of newly produced HA is dependent on HYBID expression levels. Stimulation of HAS1/2 expression and suppression of HYBID expression by TGF-β1 were abrogated by blockade of the MAPK and/or Smad signaling and the PI3K-Akt signaling, respectively. In normal human skin, expression of the TGF-β1 receptors correlated positively with HAS2 expression and inversely with HYBID expression. On the other hand, TGF-β1 up-regulated HAS1/2 expression but exerted only a slight suppressive effect on HYBID expression in synovial fibroblasts from the patients with osteoarthritis or rheumatoid arthritis, resulting in the production of lower molecular weight HA compared with normal skin and synovial fibroblasts. These data demonstrate that although TGF-β1, basic FGF, EGF, and PDGF-BB enhance HA production in skin fibroblasts, TGF-β1 most efficiently contributes to production of high molecular weight HA by HAS up-regulation and HYBID down-regulation and suggests that inefficient down-regulation of HYBID by TGF-β1 in arthritic synovial fibroblasts may be linked to accumulation of depolymerized HA in synovial fluids in arthritis patients.

In vitro model of hyaluronan synthase gene expression associated with lipopolysaccharide-induced inflammation in SW982 cell line

The present study aimed to demonstrate the phenomena of hyaluronan synthesis in response to lipopolysaccharide-induced inflammation in SW982, a human synovial sarcoma cell line. The expression of IL-1ß, including Toll-like receptor 4 and IL-1ß-converting enzyme, was proved to be induced by a reverse transcription-polymerase chain reaction. The expression of HAS genes encoding enzyme hyaluronan synthase 2 and 3, including CD44 gene which encodes the cell surface receptor of hyaluronan were upregulated in association with the activation of inflammation, along with an increase in hyaluronan level in the culture medium. The highest expression of HAS2 and HAS3 was found at 9 h after treatment with lipopolysaccharide. However, HAS1 gene expression was not detectable neither with the non-treatment nor with the treatment with lipopolysaccharide. Dexamethasone at 30 nM significantly suppressed lipopolysaccharide-induced HAS genes expression, leading to the decline of the hyaluronan level in the culture medium. Our results demonstrated the effective tool for studying hyaluronan synthesis in association with inflammation in the SW982 cell line.

KIAA1199, a deafness gene of unknown function, is a new hyaluronan binding protein involved in hyaluronan depolymerization

Hyaluronan (HA) has an extraordinarily high turnover in physiological tissues, and HA degradation is accelerated in inflammatory and neoplastic diseases. CD44 (a cell surface receptor) and two hyaluronidases (HYAL1 and HYAL2) are thought to be responsible for HA binding and degradation; however, the role of these molecules in HA catabolism remains controversial. Here we show that KIAA1199, a deafness gene of unknown function, plays a central role in HA binding and depolymerization that is independent of CD44 and HYAL enzymes. The specific binding of KIAA1199 to HA was demonstrated in glycosaminoglycan-binding assays. We found that knockdown of KIAA1199 abolished HA degradation by human skin fibroblasts and that transfection of KIAA1199 cDNA into cells conferred the ability to catabolize HA in an endo-β-N-acetylglucosaminidase-dependent manner via the clathrin-coated pit pathway. Enhanced degradation of HA in synovial fibroblasts from patients with osteoarthritis or rheumatoid arthritis was correlated with increased levels of KIAA1199 expression and was abrogated by knockdown of KIAA1199. The level of KIAA1199 expression in uninflamed synovium was less than in osteoarthritic or rheumatoid synovium. These data suggest that KIAA1199 is a unique hyaladherin with a key role in HA catabolism in the dermis of the skin and arthritic synovium.

Viscosupplementation treatment of arthritis pain

With the aging of the baby boomer generation, the number of patients with osteoarthritis (OA) is expected to swell, posing treatment challenges. Viscosupplementation, in which hyaluronic acid (HA) is injected into the knee joint, has evolved into an important part of our current therapeutic regimen in addressing the patient with knee pain due to OA. Although suffering from lack of an "evidence-based" approach, and largely funded by industry, there is a growing body of outcome data demonstrating the efficacy of HA in decreasing pain and improving function in patients with knee OA, although no evidence indicates that HA is in any way chondroprotective. The clinical success of HA has led to the ongoing introduction of various forms of HA, although little data are available to justify one over the other.

Biomechanical and biochemical characteristics of the mandibular condylar cartilage

The human masticatory system consists of a mandible which is able to move with respect to the skull at its bilateral temporomandibular joint (TMJ) through contractions of the masticatory muscles. Like other synovial joints, the TMJ is loaded mechanically during function. The articular surface of the mandibular condyle is covered with cartilage that is composed mainly of collagen fibers and proteoglycans. This construction results in a viscoelastic response to loading and enables the cartilage to play an important role as a stress absorber during function. To understand its mechanical functions properly, and to assess its limitations, detailed information about the viscoelastic behavior of the mandibular condylar cartilage is required. The purpose of this paper is to review the fundamental concepts of the biomechanical behavior of the mandibular condylar cartilage. This review consists of four parts. Part 1 is a brief introduction of the structure and function of the mandibular condylar cartilage. In Part 2, the biochemical composition of the mandibular condylar cartilage is summarized. Part 3 explores the biomechanical properties of the mandibular condylar cartilage. Finally, Part 4 relates this behavior to the breakdown mechanism of the mandibular condylar cartilage which is associated with the progression of osteoarthritis in the TMJ.

Degenerative Disorders of the Temporomandibular Joint: Etiology, Diagnosis, and Treatment

Temporomandibular joint (TMJ) disorders have complex and sometimes controversial etiologies. Also, under similar circumstances, one person’s TMJ may appear to deteriorate, while another’s does not. However, once degenerative changes start in the TMJ, this pathology can be crippling, leading to a variety of morphological and functional deformities. Primarily, TMJ disorders have a non-inflammatory origin. The pathological process is characterized by deterioration and abrasion of articular cartilage and local thickening. These changes are accompanied by the superimposition of secondary inflammatory changes. Therefore, appreciating the pathophysiology of the TMJ degenerative disorders is important to an understanding of the etiology, diagnosis, and treatment of internal derangement and osteoarthrosis of the TMJ. The degenerative changes in the TMJ are believed to result from dysfunctional remodeling, due to a decreased host-adaptive capacity of the articulating surfaces and/or functional overloading of the joint that exceeds the normal adaptive capacity. This paper reviews etiologies that involve biomechanical and biochemical factors associated with functional overloading of the joint and the clinical, radiographic, and biochemical findings important in the diagnosis of TMJ-osteoarthrosis. In addition, non-invasive and invasive modalities utilized in TMJ-osteoarthrosis management, and the possibility of tissue engineering, are discussed.

Localization of CD44 and hyaluronan in the synovial membrane of the rat temporomandibular joint

Previous studies have pointed out a lack of adhesion structures in the synovial lining layer of the rat temporomandibular joint (TMJ) despite showing an epithelial arrangement. CD44, a major cell adhesion molecule, plays crucial roles as an anchor between cells and extracellular matrices by binding hyaluronan (HA) for the development of organs or the metastasis of tumors. The present study examined the localization of CD44 in the synovial membrane of the rat TMJ by immunocytochemistry for OX50, ED1, and Hsp25, which are markers for the rat CD44, macrophage-like type A, and fibroblast-like type B synoviocytes, respectively. Histochemistry for HA-binding protein (HABP) was also employed for the detection of HA. OX50 immunoreactions were found along the cell surface and, in particular, accumulated along the surface of the articular cavity. Observations by a double immunostaining and immunoelectron microscopy revealed that all the OX50-immunopositive cells were categorized as fibroblastic type B cells, which had many caveolae and a few vesicles reactive to intense OX50. However, the macrophage-like type A cells did not have any OX50 immunoreaction in the synovial lining layer. A strong HABP reaction was discernable in the extracellular matrix surrounding both OX50-positive and -negative cells in the synovial lining layers, exhibiting a meshwork distribution, but weak in its sublining layer. This localization pattern of CD44 and HABP might be involved in the formation of the epithelial arrangement of the synovial lining layer. Furthermore, OX50 immunonegativity in the type A cells suggests their low phagocytotic activity in the rat TMJ under normal conditions.

Size selectivity of hyaluronan molecular sieving by extracellular matrix in rabbit synovial joints

In joint fluid the polymer hyaluronan (HA) confers viscous lubrication and greatly attenuates trans-synovial fluid loss (outflow buffering). Outflow buffering arises from the molecular sieving (reflection) and concentration polarization of HA at the synovial membrane surface. Outflow buffering declines if HA chain length is reduced, as in arthritis, and this has been attributed to reduced HA reflection. This was tested directly in the present study. Infused solutions of HA of approximately 2200 kDa (HA2000, 0.2 mg ml(-1)) or approximately 500 kDa (HA500, 0.2 mg ml(-1)) or approximately 140 kDa (HA140, 0.2-4.0 mg ml(-1)) were filtered across the synovial lining of the knee joint cavity of anaesthetized rabbits at a constant rate, along with a freely permeating reference solute, 20 kDa fluorescein-dextran (FD20). After a priming period the femoral lymph was sampled over 3 h. Mixed intra-articular (i.a.) fluid and subsynovial fluid were sampled at the end. Fluids were analysed by gel exclusion chromatography. The trans-synovial concentration profile was found to depend on polymer size. The i.a. concentration of HA2000 increased substantially relative to infusate and the subsynovial and lymph concentrations fell substantially. For HA500 and HA140 the trans-synovial concentration gradients were less pronounced, and absent for FD. The reflected fractions for HA2000, HA500 and HA140 across the cavity-to-lymph barrier were 0.65 +/- 0.05 (n = 10), 0.43 +/- 0.09 (n = 3) and 0.19 +/- 0.05 (n = 7), respectively, at matched filtration rates (P < 0.0001, analysis of variance). Reflected fractions calculated from HA i.a. accumulation or subsynovial dilution showed the same trend. The results demonstrate size-selective molecular sieving by the synovial extracellular matrix, equivalent to steric exclusion from cylindrical pores of radius 33-59 nm. The findings underpin the concentration polarization-outflow buffering theory and indicate that reduced HA chain length in arthritis exacerbates lubricant loss from a joint.

Role of hyaluronan chain length in buffering interstitial flow across synovium in rabbits

1. Synovial fluid drains out of joints through an interstitial pathway. Hyaluronan, the major polysaccharide of synovial fluid, attenuates this fluid drainage; it creates a graded opposition to outflow that increases with pressure (outflow 'buffering'). This has been attributed to size-related molecular reflection at the interstitium-fluid interface. Chain length is reduced in inflammatory arthritis. We therefore investigated the dependence of outflow buffering on hyaluronan chain length. 2. Hyaluronan molecules of mean molecular mass approximately 2200, 530, 300 and 90 kDa and concentration 3.6 mg ml-1 were infused into the knees of anaesthetized rabbits, with Ringer solution as control in the contralateral joint. Trans-synovial drainage rate was recorded at known joint pressures. Pressure was raised in steps every 30-60 min (range 2-24 cmH2O). 3. With hyaluronan-90 and hyaluronan-300 the fluid drainage rate was reduced relative to Ringer solution (P < 0.001, ANOVA) but increased steeply with pressure. The opposition to outflow, defined as the pressure required to drive unit outflow, did not increase with pressure, i.e. there was no outflow buffering. 4. With hyaluronan-530 and hyaluronan-2000 the fluid drainage rate became relatively insensitive to pressure, causing a near plateau of flow. Opposition to outflow increased markedly with pressure, by up to 3.3 times over the explored pressures. 5. Hyaluronan concentration in the joint cavity increased over the drainage period, indicating partial reflection of hyaluronan by synovial interstitium. Reflected fractions were 0.12, 0.33, 0.25 and 0.79 for hyaluronan-90, -300, -530 and -2200, respectively. 6. Thus the flow-buffering effect of hyaluronan depended on chain length, and shortening the chains reduced the degree of molecular reflection. The latter should reduce the concentration polarization at the tissue interface, and hence the local osmotic pressure opposing fluid drainage. In rheumatoid arthritis the reduced chain length will facilitate the escape of hyaluronan and fluid.

Amelioration of disease severity by intraarticular hylan therapy in bilateral canine osteoarthritis

Because of its high molecular weight, the glycosaminoglycan molecule hyaluronan is responsible for the viscoelastic properties of normal synovial fluid. In osteoarthritis, the concentration and molecular weight of hyaluronan in synovial fluid is diminished: this impairs the ability of synovial fluid to effectively lubricate joints, absorb loads, and exert anti-inflammatory effects. Using a bilateral anterior cruciate-ligament transection and partial neurectomy canine model of osteoarthritis, this study examined the effect of viscosupplementation with hylan G-F 20 as a treatment for osteoarthritis. Twelve dogs underwent bilateral arthroscopic anterior cruciate-ligament transections and partial neurectomy of the knee joints. Beginning 1 week after the operation, six dogs received three weekly 500-microl injections of hylan G-F 20 in one knee and a sham injection of saline solution in the contralateral knee (early-treatment group). The remaining six animals underwent the same treatment 2 months following the procedure (late-treatment group). All dogs were killed at 8 months, and both knees were evaluated for gross pathology, histology, and proteoglycan content. In addition, with use of 500-MHz [1H] magnetic resonance spectroscopy, the synovial fluid from both knees was assessed for changes in metabolic profile. Differences in outcome were analyzed with paired t tests. Gross pathological and histological examination revealed significantly less severe changes of osteoarthritis in knees treated with hylan G-F 20 2 months after surgery than in the contralateral untreated knees. Magnetic resonance spectroscopy of the specimens in this late-treatment group showed significantly decreased glucose concentrations and significantly elevated isoleucine levels in the synovial fluid from knees treated with hylan G-F 20 compared with the controls. Previous magnetic resonance spectroscopy had shown that glucose concentrations increase with the onset of osteoarthritis and eventually diminish in end-stage osteoarthritis. The three injections of hylan were given after osteoarthritis was established, and the severity of the disease was ameliorated in the treated knees 6 months after treatment. This occurred although hylan G-F 20 is almost certainly cleared from joints by lymphatics within 4 weeks of injection, suggesting that hylan therapy can retard the progression of osteoarthritis for periods of time extending beyond the intraarticular residence time of the injected molecules and that hylan injections given at relatively early stages of osteoarthritis may have a chondroprotective effect. No changes in outcome were noted in the animals that received hylan G-F 20 immediately following surgery.

The pathobiology of osteoarthritis and the rationale for the use of pentosan polysulfate for its treatment

OBJECTIVES

Structure-modifying osteoarthritis (OA) drugs (SMOADs) may be defined as agents that reverse, retard, or stabilize the underlying pathology of OA, thereby providing symptomatic relief in the long-term. The objective of this review was to evaluate the literature on sodium pentosan polysulfate (NaPPS) and calcium pentosan polysulfate (CaPPS), with respect to the pathobiology of OA to ascertain whether these agents should be classified as SMOADs.

METHODS

Published studies on NaPPS and CaPPS were selected on the basis of their relevance to the known pathobiology of OA, which also was reviewed.

RESULTS

Both NaPPS and CaPPS exhibit a wide range of pharmacological activities. Of significance was the ability of these agents to support chondrocyte anabolic activities and attenuate catabolic events responsible for loss of components of the cartilage extracellular matrix in OA joints. Although some of the anti-catabolic activities may be mediated through direct enzyme inhibition, NaPPS and CaPPS also have been shown to enter chondrocytes and bind to promoter proteins and alter gene expression of matrix metalloproteinases and possibly other mediators. In rat models of arthritis, NaPPS and CaPPS reduced joint swelling and inflammatory mediator levels in pouch fluids. Moreover, synoviocyte biosynthesis of high-molecular-weight hyaluronan, which is diminished in OA, was normalized when these cells were incubated with NaPPS and CaPPS or after intraarticular injection of NaPPS into arthritic joints. In rabbit, canine, and ovine models of OA, NaPPS and CaPPS preserved cartilage integrity, proteoglycan synthesis, and reduced matrix metalloproteinase activity. NaPPS and CaPPS stimulated the release of tissue plasminogen activator (t-PA), superoxide dismutase, and lipases from vascular endothelium while concomitantly decreasing plasma levels of the endogenous plasminogen activator inhibitor PAI-1. The net thrombolytic and lipolytic effects exhibited by NaPPS and CaPPS may serve to improve blood flow through subchondral capillaries of OA joints and improve bone cell nutrition. In geriatric OA dogs, NaPPS and CaPPS reduced symptoms, as well as normalized their thrombolytic status, threshold for platelet activation, and plasma triglyceride levels. These hematologic parameters were shown to be abnormal in OA animals before drug treatment. Similar outcomes were observed in OA patients when CaPPS or NaPPS were given orally or parenterally in both open and double-blind trials.

CONCLUSIONS

The data presented in this review support the contention that NaPPS and CaPPS should be classified as SMOADs. However, additional long-term clinical studies employing methods of assessing joint structural changes will be needed to confirm this view.

Hyaluronan production in human rheumatoid fibroblastic synovial lining cells is increased by interleukin 1 beta but inhibited by transforming growth factor beta 1

OBJECTIVES

To investigate the regulatory roles of interleukin 1 beta (IL1 beta), tumour necrosis factor alpha (TNF alpha), interferon gamma (IFN gamma) or transforming growth factor beta 1 (TGF beta 1) on hyaluronan (HA) synthesis by human fibroblastic synovial lining cells.

METHODS

Concentrations of HA in culture supernatants of fibroblastic synovial lining cell line (RAMAK-1 cell line) with or without stimulation by IL1 beta, TNF alpha, IFN gamma or TGF beta 1 were measured by sandwich binding protein assay. Levels of HA synthase mRNA of the cells with or without stimulation were detected by reverse transcribed polymerase chain reaction. Molecular weights of HA in the culture supernatants of the cells with or without stimulation were measured using high performance gel permeation liquid chromatography.

RESULTS

HA synthesis by the cells was not significantly augmented by TNF alpha or by IFN gamma. It was significantly stimulated by IL1 beta but inhibited by TGF beta 1. Molecular weights of HA in the culture supernatants of the cells were unchanged by stimulation with TNF alpha. They were remarkably increased by stimulation with IL1 beta and IFN gamma, but reduced with TGF beta 1.

CONCLUSION

IL 1 beta is an up regulator of HA synthesis, while TGF beta 1 is a down regulator. HA production in the synovial lining cells of inflamed joints (for example, rheumatoid arthritis) might be regulated by the balance of these cytokines.

Quantitative analysis of hyaluronan in the synovial tissues of patients with joint disorders

Quantitative analysis of hyaluronan (hyaluronic acid; HA) in the synovial tissues of patients with joint disorders were performed. HA was found not only in the synovial intimal cells and matrices, but also especially in the alveolar lymphoid follicles and connective tissues surrounding blood vessels in the inflammatory granular synovium which formed the pannus. HA levels in the synovium of patients with rheumatoid arthritis (RA) (459.0+/-66.2 microg/g) where shown to be higher than those in patients with osteoarthritis (246.9+/-34.8 microg/g) and traumatic injury (227.7+/-35.4 microg/g). It follows from the present findings, HA in the synovium might contribute to the high amounts of serum levels of HA in patients with rheumatoid arthritis.

Enhanced synovial production of hyaluronic acid may explain rapid clinical response to high-dose glucosamine in osteoarthritis

Anecdotal reports of rapid symptomatic response to high-dose glucosamine in osteoarthritis are not credibly explained by the traditional view that glucosamine promotes synthesis of cartilage proteoglycans. An alternative or additional possibility is that glucosamine stimulates synovial production of hyaluronic acid (HA), which is primarily responsible for the lubricating and shock-absorbing properties of synovial fluid. Many clinical and veterinary studies have shown that intra-articular injections of high-molecular-weight HA produce rapid pain relief and improved mobility in osteoarthritis. HA has anti-inflammatory and analgesic properties, and promotes anabolic behavior in chondrocytes. The concentration and molecular weight of synovial fluid HA are decreased in osteoarthritis; by reversing this abnormality, high-dose glucosamine may provide rapid symptomatic benefit, and in the longer term aid the repair of damaged cartilage.

Markers of connective tissue activation in aseptic hip prosthetic loosening

The fundamental role played by macrophages and fibroblasts of the synovial-like membrane in aseptic hip prosthesis loosening (AHPL) has recently been confirmed by numerous studies. In this study, the activity of these cells in patients with prosthetic loosening was analyzed by evaluating the main markers of fibroblast and macrophage activation in sera and in supernatants of cultured fibroblasts obtained from AHPL patients who underwent revision of a loose total hip arthroplasty implant. In these patients interleukin-1, hyaluronic acid (HA), and type III procollagen peptide were evaluated. The results were compared with those obtained in 13 patients with firmly fixed implants and 13 patients with osteoarthritis. Serum HA levels were significantly higher (779.3 +/- 951.6 micrograms/L) in patients with AHPL as compared with patients with firmly fixed implants (112.9 +/- 84.9 micrograms/L) and osteoarthritis (115.3 +/- 107.8 micrograms/L). Type III procollagen peptide levels were elevated in only 33.3% of patients with AHPL, whereas interleukin-1-beta (IL-1 beta) was detectable in 4 patients with AHPL but not in patients with firmly fixed implants or osteoarthritis. In supernatants, IL-1 beta was measurable in 4 of 6 fibroblast cultures, whereas type III procollagen peptide and HA were measurable in all cultures. The data confirm the existence of an inflammatory process in AHPL patients in which macrophages and fibroblasts play a key role. The detection, in these patients, of high circulating levels of IL-1 beta and HA is very important from a clinical point of view because they could be considered specific markers of inflammation.

Degradation of hyaluronan by peroxynitrite

Treatment of high-molecular-weight hyaluronan (HA) with peroxynitrite at neutral pH (ONOO-/ONOOH) results in altered mobility on agarose gel electrophoresis, as well as reduced limiting viscosity number. Both effects are consistent with a reduction in HA molecular weight. HA is protected from peroxynitrite attack to varying extents by addition of alternate target molecules. Thiourea is extremely effective as a protective agent, dimethyl sulfoxide is moderately effective, while sodium benzoate and mannitol are slightly effective. A similar pattern of protection is observed when HA is degraded by hydroxyl radical generated by a metal ion/hydrogen peroxide system. On the basis of these observations, peroxynitrite is proposed to have hydroxyl radical-like activity in degrading HA.

Hyaluronic acid. A review of its pharmacology and use as a surgical aid in ophthalmology, and its therapeutic potential in joint disease and wound healing

Hyaluronic acid is a naturally occurring polysaccharide with distinct physicochemical properties which underlie its application as a viscoelastic tool in ophthalmological surgery. In cataract surgery the role of hyaluronic acid in facilitating procedures and protecting the corneal endothelium is well established. Some benefit has also been gained with the use of hyaluronic acid in penetrating keratoplasty, trabeculectomy, retinal reattachment and trauma surgery, although its efficacy in these indications is less well-defined in the published literature. In addition to its lubricating and cushioning properties, demonstration of some in vitro anti-inflammatory activity and a possible disease-modifying effect for hyaluronic acid in animals has prompted its investigation as a treatment in osteoarthritis and, to a much lesser extent, in rheumatoid arthritis. Hyaluronic acid 20 mg, as weekly intra-articular injections for 3 to 7 weeks, improved knee pain and joint motion in patients with osteoarthritis. Although this occurred to a greater degree than with placebo in most comparisons, the effects of hyaluronic acid was similar to those of placebo in the largest trial. In the few available comparisons with other agents, hyaluronic acid appeared equivalent to methylprednisolone 40 mg (for 3 weeks) and to a single injection of triamcinolone 40 mg. Hyaluronic acid was distinguished from other therapies by providing a sustained effect after treatment discontinuation. Together with its very good tolerability profile, these properties justify further study of hyaluronic acid in patients with osteoarthritis. Some limited evidence of improvement in patients with rheumatoid arthritis, and a possible healing effect of hyaluronic acid on tympanic membrane perforations, represent additional areas of interest for future investigation. In summary, hyaluronic acid is a well-established adjunct to cataract surgery and may prove to be a promising option in the treatment of patients with osteoarthritis. Its very good tolerability provides further impetus for examination of its potential role in an extended scope of arthritic and ophthalmological indications, and in wound healing.

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.

Clinical correlations and prognosis based on hyaluronic acid serum levels in patients with progressive systemic sclerosis

The serum levels of hyaluronic acid (sHA) were measured using an affinoimmunoenzymatic assay in patients with distal (n = 16) and proximal (n = 15) progressive systemic sclerosis (PSS) and in 31 controls. The severity of PSS was evaluated using a standardized organ-involvement score. The mean sHA was significantly higher in the patients with PSS than in controls (mean +/- SD:80 +/- 43.4 micrograms/l vs. 42.3 +/- 19.1 micrograms/l, P less than 0.001). sHA was significantly higher in patients with proximal PSS than in patients with distal PSS (106.4 +/- 44.6 micrograms/l vs. 55.4 +/- 23.8 micrograms/l, P less than 0.001). A positive correlation was found between sHA and the disease score (r = 0.67, P less than 0.001). sHA was also correlated with lung diffusion capacity for carbon monoxide (r = 0.70, P less than 0.001), but only in the those patients who had abnormal lung function, and therefore presumably had lung PSS involvement. We suggest that sHA could be an indicator of the degree of systemic involvement in PSS. Its prognostic value and possible use in the follow up of patients with PSS remain to be clarified.

Arthritis-associated changes in flow cytometric characteristics of cultured synovial fibroblasts

Synovial fibroblasts cultured from patients with rheumatoid or reactive arthritis and from controls were studied by flow cytometry, spectroscopy, and electron microscopy. Analysis of 29 cell lines revealed consistent differences between arthritic and normal fibroblasts. Cells cultured from inflamed synovial tissue exhibited higher autofluorescence than did control fibroblasts, and displayed exceptional light scatter properties in flow cytometry, indicating changes in cytoplasmic structures. Electron microscopic examination of the fibroblasts from arthritic synovial tissue revealed large numbers of round, swollen, laminated, mitochondrion-like bodies, which were not observed in the control fibroblasts. The changes observed by flow cytometry (light scatter and autofluorescence) coincided with the presence of the mitochondrion-like organelles. The strong autofluorescence observed in the arthritic fibroblasts resembled the fluorescence spectrum of mitochondrial flavoproteins. These data suggest that persistent metabolic and structural changes have occurred in the mitochondria of synovial fibroblasts and inflammatory synovial tissue. The usefulness of flow cytometry in identifying such cells is described.

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.

The synthesis of hyaluronic acid by human synovial fibroblasts is influenced by the nature of the hyaluronate in the extracellular environment

Various cell lines of human synovial fibroblasts derived from synovium obtained at the time of biopsy or total joint-replacement surgery have been established. The synthesis of 3H-labelled hyaluronic acid (HA) in these cells has been determined, and the effects of adding HA of varying molecular size to the cultured cells examined. The results obtained clearly show that the in vitro synthesis of HA by these cells is influenced by the concentration and molecular weight (MW) of the HA in their extracellular environment. Synovial fibroblasts derived from an osteoarthritic joint demonstrated the most marked response on exposure to exogenous HA, showing a stimulation of HA synthesis with preparations of weight-average molecular weight (Mw) greater than 5 X 10(5) in a concentration dependent manner. HA preparations with Mw less than 5 X 10(5) showed little or no effect except at high concentrations where a suppression of biosynthesis was observed. A model to explain these findings is proposed.

Extracellular mammalian polysaccharides: glycosaminoglycans and proteoglycans

This review of the mammalian extracellular matrix polysaccharides covered the glycosaminoglycans (GAGs) and their association into proteoglycans. As they necessarily pertain to the chromatographic and electrophoretic separations of these molecules, the structural features of the five principal GAGs were briefly reviewed. Much of the current structural work as well as the separation technology has been concerned with the sulfation state and copolymeric sequences of the individual classes of GAGs. The separation methods discussed included electrophoresis by agarose, acrylamide and cellulose acetate, high-performance liquid chromatography (HPLC), ion-exchange, gel permeation and biospecific affinity methods. Since detection systems are an integral part of chemical separation technology, current thoughts about the best methods to assay GAGs or detect column fractions were discussed. These included polysaccharide-specific detection systems such as Alcian blue dye, 1,9-dimethylmethylene blue, bovine serum albumin-Coomassie blue, as well as non-specific carbohydrate detection systems such as the carbazole or indole hydrochloride methods. Instrumentation used in the detection of chromatography fractions for these molecules was discussed, since the usual ultraviolet detector, standard with HPLC equipment, is often unsatisfactory. The most sensitive specific detection method for GAGs is the use of monoclonal antibodies, which are only now becoming commercially available. The use of these antibodies, combined with HPLC separation, appears to be the best available biochemical technology for studying the extracellular matrix polysaccharides. Finally, the association between proteoglycans, GAGs and mammalian disease processes was reviewed, emphasizing mucopolysaccharidoses and arthritis. The early detection of both of these diseases is desired for effective counselling and treatment. Many of the methods discussed here have been applied, but others are yet to be tried in efforts to further that goal.

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

The effects of peripheral blood monocyte and rheumatoid synovial fluid macrophage conditioned media were studied on hyaluronic acid (HA) metabolism of normal synovial fibroblasts. Both media stimulated HA synthesis about two-fold compared to controls (1% fetal calf serum). The activated mononuclear phagocyte conditioned media did not contain HA-degrading activity in these experiments. The effects of various concentrations of interleukin-1 (IL-1) on HA synthesis and proliferation of synovial fibroblasts were studied. Even at very low concentrations (0.1 IU IL-1/ml) HA synthesis was stimulated. With increasing concentrations HA synthesis did not increase but proliferation was stimulated. Stimulated fibroblasts synthesized mainly high molecular weight HA. Thus with IL-1-activation, normal synovial fibroblasts could not produce increased amounts of abnormal HA with decreased molecular weight.

Hyaluronic acid production in vitro by synovial lining cells from normal and rheumatoid joints

Organ cultures and primary cell cultures were established from synovial tissue collected from patients with rheumatoid arthritis. Hyaluronic acid measured by the incorporation of [3H]glucosamine into the polysaccharide was found to be synthesised in the cultures immediately after transfer from in-vivo to in-vitro conditions. This was in contrast to the primary cultures established from cells isolated from normal joints. The latter cells did not synthesise any detectable hyaluronate. 90-100% of the cells in primary culture were found to be esterase positive, indicating their macrophage nature. The molecular weight of the hyaluronate produced by the pathological cells was low (approximately 50 000) compared with the molecular weight of hyaluronate found in joint fluid from normal or rheumatoid joints. Cell lines of fibroblasts established from rheumatoid joints and studied after four or seven passages also produced hyaluronate of low molecular weight. It is known that similar cell lines from normal joints produce a high molecular weight polymer.

Etiology of rheumatoid arthritis

Definite genetic associations with immunological cooperative HLA-D(R) antigens have been demonstrated for rheumatoid arthritis (RA). Microbial etiology has not been proven, but some hope for the supporters of this view is still given by small viruses, plasmids of enteric bacteria or perhaps oncogen-like DNA-sequences. Yet, electrophoretical analysis of membrane proteins or surface glycoproteins of RA synovial cells does not show any differences compared to reference cells. Autoimmunity to several tissue elements has been demonstrated, but most of it is of secondary nature. Antigenicities of type II and III collagens are probably only contributory factors for HLA-DR4 positive individuals. Proteoglycans or minor cartilage collagens have not been extensively studied, so far. Endocrine, dietary or psychological influences might be triggering events for otherwise 'preloaded' individuals.

Fibroblast activation in scleroderma

Skin fibroblast cultures started from 6 scleroderma patients and 5 controls were compared with respect to synthesis of collagen and glycosaminoglycans. Fibroblast strains started from skin biopsy material from patients with active localized disease exhibited appreciably increased synthesis of collagen, whereas cultures from old sclerodermatous areas showed normal or decreased rates for collagen synthesis. During subculturing, all fibroblast strains with a high initial rate of collagen synthesis exhibited a gradual decline to near-normal values by the 12th in vitro passage. No similar alterations were detected in glycosaminoglycan metabolism. The results suggest that fibroblast activation in scleroderma is due to exogenous factors; in cell culture their effects are lost and activation disappears.

Altered glycosaminoglycan production in cultured osteogenesis-imperfecta skin fibroblasts

Collagen and glycosaminoglycan syntheses were studied in skin fibroblasts cultured from patients with osteogenesis imperfecta (OI) and from age-matched controls. Collagen synthesis (measured as protein-bound [3H]hydroxyproline) was decreased in all four OI cell lines studied in the present experiments, comprising 16-24% of total protein synthesis (40% in normal cells). Hyaluronic acid production in OI skin fibroblasts per cell was higher than in age-matched controls, but the production of sulphated glycosaminoglycans was at the normal level. Thus the ratio of the hyaluronic acid and sulphated-glycosaminoglycan radioactivities was markedly higher in OI cultures than in control cultures, especially at the exponential phase of growth where the synthesis of hyaluronic acid was highest. Hyaluronic acid in OI had a normal molecular weight when determined by gel filtration on Sepharose 2B. The removal of high-molecular-weight hyaluronic acid from the medium by hyaluronidase had no effect on the rate of collagen secretion in OI cell line 1 (A.T.C.C. 1262), in which the rate of collagen secretion was lowest.

The effect of rheumatoid synovial fluid macrophages on DNA, glycosaminoglycan and collagen synthesis by synovial fibroblasts

The effects of soluble factors secreted by peripheral blood monocytes and rheumatoid synovial fluid macrophages were tested on human synovial fibroblast cultures. Both monocytes and macrophages liberated factors which reduced DNA synthesis (3H-thymidine incorporation) by synovial fibroblasts. Monocyte and macrophage factors stimulated hyaluronic acid synthesis. The activation obtained with rheumatoid synovial macrophages was considerably greater than that with monocytes. Foetal bovine serum was found to have a clear stimulatory effect on the synthesis of collagen and other proteins by fibroblasts. The effects of monocyte and macrophage factors on protein synthesis in synovial fibroblasts were small: collagen synthesis was slightly increased relative to other extracellular proteins.