Hyaluronic acid in synovial fluid. I. Molecular parameters of hyaluronic acid in normal and arthritis human fluids

Effect of high molecular weight hyaluronan on cartilage degeneration in a rabbit model of osteoarthritis

The effects of high molecular weight hyaluronan (HA) on cartilage degeneration were investigated in a partial menisectomy model of osteoarthritis (OA) in the rabbit knee. This study compared HA80 (0.8 x 10(6) Da, 1%), HA190 (1.9 x 10(6) Da, 0.01-1%) and saline. HA (0.1 ml/kg) or saline were injected intra-articularly twice a week immediately after surgery. Degenerative changes in femoral and tibial cartilages were graded histopathologically 2 and 4 weeks after surgery. Two weeks after surgery, HA190, only when used at a 1% concentration, resulted in a dramatic inhibition of cartilage degeneration in both the femoral condyle and the tibial plateau (P < 0.01). Two weeks after surgery, the protection against cartilage degeneration was significantly (P < 0.05) greater with HA190 than with HA80. Four weeks after surgery, only the femoral cartilage degeneration was significantly and similarly inhibited with HA190 (P < 0.01) and HA80 (P < 0.05). Scanning electron micrographs of femoral cartilage showed that cartilage degeneration was less severe with HA190 than with saline. These results might suggest that, in the rabbit model, intra-articular administration of higher molecular weight HA is more effective than lower molecular weight HA in inhibiting cartilage degeneration in early OA.

Effects of the addition of hyaluronate segments with different chain lengths on the viscoelasticity of hyaluronic acid solutions

The effects of the addition of sodium hyaluronate segments (sHA) with different chain lengths on the viscoelasticity of high molecular weight sodium hyaluronate (HA) aqueous solutions were studied. The additive effects of sHA depended on the chain length of sHA. Shorter sHA decreased storage (G') and loss (G") moduli, whereas longer sHA increased both moduli. In physiological saline, the effects of the addition of sHA depended on the chain length of sHA, as in aqueous solutions, except that shorter segments did not decrease both moduli. The effects of the addition of monosaccharides, i.e., N-acetyl glucosamine (GlcNAc) and sodium glucuronate (GlcANa), were also studied. Although GlcNAc increased G' and G", GlcANa decreased both moduli. A shift factor "A," which depended on chain-length effects, a sugar effect, and a salt effect, was developed to explain these additive effects quantitatively.

The structure and function of hyaluronan: An overview

Hyaluronan is a major component of synovial tissue and fluid as well as other soft connective tissues. It is a high-Mr polysaccharide which forms entangled networks already at dilute concentrations (< 1 mg/mL) and endows its solutions with unique rheological properties. Physiological functions of hyaluronan (lubrication, water homeostasis, macromolecular filtering, exclusion, etc.) have been ascribed to the properties of these networks. Recently a number of specific interactions between hyaluronan and a group of proteins named hyaladherins have also pointed towards a role of hyaluronan in recognition and the regulation of cellular activities. Many more or less well documented hypotheses have been proposed for the function of hyaluronan in joints, for example, that it should lubricate, protect cartilage surfaces, scavenge free radicals and debris, keep the joint cavities open, form flow barriers in the synovium and prevent capillary growth.

Quantitative analysis of hyaluronan in human synovial fluid using capillary electrophoresis

The glycosaminoglycan, hyaluronan, can be detected in human synovial fluid by capillary electrophoresis (CE). Variations in peak shape make this technique unsuitable for quantitative analysis of hyaluronan in raw synovial fluid. Quantitative analysis was achieved by hydrolysis of the polymeric hyaluronan to the tetrasaccharide by the action of testicular hyaluronidase and separation of the product using CE. A UV detector operating at 200 nm was used. The X-ray contrast material, omnipaque, a propriety aqueous solution of iohexol was used as internal standard. A second peak in the electropherogram of synovial fluid was quantified. The variation in concentrations of these two components correlate with the arthritic disease state of a joint.

The role of viscosupplementation with hylan G-F 20 (Synvisc) in the treatment of osteoarthritis of the knee: a Canadian multicenter trial comparing hylan G-F 20 alone, hylan G-F 20 with non-steroidal anti-inflammatory drugs (NSAIDs) and NSAIDs alone

To determine the safety and efficacy of viscosupplementation with hylan G-F 20, a cross-linked hyaluronan preparation, used either alone or in combination with continuous non-steroidal anti-inflammatory drug (NSAID) therapy, a randomized, controlled, multicenter clinical trial, assessed by a blinded assessor, was conducted in 102 patients with osteoarthritis (OA) of the knee. All patients were on continuous NSAID therapy for at least 30 days prior to entering the study. Patients were randomized into three parallel groups: (1) NSAID continuation plus three control arthrocenteses at weekly intervals; (2) NSAID discontinuation but with three weekly intra-articular injections of hylan G-F 20; and (3) NSAID continuation plus three injections, one every week, intra-articular injections of hylan G-F 20. Outcome measures of pain and joint function were evaluated by both the patients and an evaluator at baseline and weeks 1, 2, 3, 7 and 12, with a follow-up telephone evaluation at 26 weeks. At 12 weeks all groups showed statistically significant improvements from baseline, but did not differ from each other. A statistical test for the equivalence, the q-statistic, demonstrated that viscosupplementation with hylan G-F 20 was at least as good or better than continuous NSAID therapy for all outcome measurements except activity restriction. At 26 weeks both groups receiving hylan G-F 20 were significantly better than the group receiving NSAIDs alone. A transient local reaction was observed in three patients after hylan G-F 20 injection; only one patient withdrew from the study as a result and all recovered without any sequela. Hylan G-F 20 is a safe and effective treatment for OA of the knee and can be used either as a replacement for or an adjunct to NSAID therapy.

Osteoarthritis in older patients. Optimum treatment

A number of therapeutic options to control pain, maintain function and decrease disability are available for older patients with osteoarthritis. The indication for pharmacological therapy should be restricted to periods with pain. Great attention should be given to nonpharmacological interventions such as education, exercise, lifestyle modification and emotional support. If medication is necessary, most patients require only pure analgesics such as paracetamol (acetaminophen); nonsteroidal anti-inflammatory drugs (NSAIDs) should be used if patients do not respond to simpler measures. All medication should be carefully monitored considering the frequency of adverse drug reactions in older patients.

Serum hyaluronic acid level as a predictor of disease progression in osteoarthritis of the knee

OBJECTIVE

To investigate the prognostic value of serum hyaluronic acid (HA) and keratan sulfate (KS) levels in relation to tibiofemoral osteoarthritis (OA) of the knee.

METHODS

Clinical and demographic data were collected on 94 patients. Radiographs were obtained at study entry and at 5-year followup. Disease progression was defined as 2 mm of joint space narrowing of any tibiofemoral compartment, and/or knee joint surgery during the study period. Serum HA and KS were measured and levels were correlated with entry data and disease progression.

RESULTS

At entry, HA levels were significantly related to disease duration (P = 0.036), minimum joint space (P = 0.049), and previous surgery (P = 0.001). After these variables were taken into account, patients whose disease had progressed were shown to have had significantly higher levels of HA at baseline compared with those whose disease had not progressed (P = 0.019). However, there were no significant differences in levels of serum KS between those with and those without disease progression, at entry (P = 0.779) or at subsequent visits.

CONCLUSION

These results suggest that serum HA levels predict disease outcome in OA of the knee and confirm that a single measurement of the serum level of KS is not useful as a prognostic marker in OA.

Expression of CD44 in normal and rheumatoid synovium and cultured synovial fibroblasts

OBJECTIVE

To determine if expression of CD44, the principal receptor for hyaluronan, was altered in rheumatoid (RA) synovium and cultured rheumatoid synovial fibroblasts.

METHODS

Synovium was obtained from normal adult human joints (n = 4) and from joints of patients with RA (n = 5). Specific monoclonal antibodies to CD44 were used in immunofluorescence of whole synovium and cultured synovial fibroblasts and in quantitative Western blotting and ELISA of CD44 in cultured synovial fibroblasts.

RESULTS

CD44 was restricted to the lining layer in normal synovium but present, in reduced concentrations, throughout rheumatoid synovium. Cultured rheumatoid cells were 19% larger in area and showed far fewer and less extensive CD44-positive cytoplasmic extensions, together with reduced staining intensity compared with normal. Quantitative Western blotting normalised for cell protein showed a 75% reduction (normal = 1754 (835), rheumatoid = 409 (84) mean (SD) arbitrary units) in the amount of CD44 in rheumatoid cells compared with normal, and enzyme linked immunosorbent assay (ELISA) of cultured cell monolayers normalised for cell number indicated a 29% reduction (normal = 0.707 (0.110), rheumatoid = 0.504 (0.103), mean (SD) optical density at 405 nm).

CONCLUSIONS

Rheumatoid synovial cells showed altered morphology and reduced CD44 expression compared with normal cells. CD44, by means of modulated associations with the cytoskeleton, may be involved in cell shape change.

Interactions of hyaluronan (hyaluronic acid) with phospholipids as determined by gel permeation chromatography, multi-angle laser-light-scattering photometry and 1H-NMR spectroscopy

The chain flexibility of solutions of hyaluronan (HA) of different molecular weights was determined by 1H-NMR spectroscopy in the absence and presence of the phospholipid dipalmitoyl-D,L-alpha-phosphatidylcholine (DPC). Sonication of high- or low-molecular-weight HA with DPC for periods of up to 120 min markedly increased HA chain flexibility as determined by observing the half-peak linewidths (delta V1/2) for the methyl protons of the acetamidodeoxyglucose residues of the HA molecules. Gel permeation chromatography of mixtures of purified high-molecular-weight HA (Healon) with 3H-DPC or 3H-platelet activating factor (PAF) showed exclusion of these radioactively labelled molecules from the gel in the presence of HA but not in its absence. Studies using multi-angle laser-light-scattering (MALLS) photometry of sonicates of DPC and Healon after Superose 6 chromatography revealed increases in HA Mw, Mn, Mz and their corresponding root mean square radii relative to control sonicates of HA without DPC. From these data, we have deduced that DPC binds to HA by competing for those hydrophobic centres along the HA chain which are normally responsible for the inter- and intra-chain interactions and which confer stiffness to the HA molecule. It is proposed that such interactions in arthritic joints could reduce synovial fluid viscoelasticity thereby diminishing the ability of this medium to protect articular cartilage from mechanical injury.

Hyaluronan in canine arthropathies

Soluble hyaluronan (HA), which has been considered as a marker for joint disease in man, was measured in serum and synovial fluid (SF) from dogs with osteoarthritis (OA), rheumatoid arthritis (RA), and rupture of the cranial cruciate ligament (CCL) and from normal dogs (control). Dogs with OA and RA had significantly increased serum HA (P < 0.001) and decreased synovial fluid HA (P < 0.001), as did dogs with CCL rupture (serum, P < 0.05; synovial fluid, P < 0.005). In OA, HA was lower in the SF from the affected joint than in that from the clinically normal (inactive) contralateral joint; no such difference was seen in dogs with CCL rupture. Dogs with liver disease (portocaval shunts, viral infectious hepatitis, metastatic neoplasm and disease secondary to diabetes mellitus) had increased serum HA concentrations (P < 0.001). There was a significant overlap of HA values in the diseased and normal dogs. Therefore, it is unlikely that the measurement of this cartilage breakdown product would be of value for diagnosis or prognosis in canine arthropathies.

Circulating and synovial fluid hyaluronan levels. Effects of intraarticular corticosteroid on the concentration and the rate of turnover

OBJECTIVE

To assess the effect of intraarticular (IA) corticosteroid on hyaluronan (HA) concentrations in synovial fluid (SF) and serum and the clearance of 131I-labeled albumin from the joints of patients with rheumatoid arthritis (RA), osteoarthritis (OA), and ankylosing spondylitis (AS).

METHODS

SF and serum were collected before and 2 weeks and 2 months after IA steroid injection. The HA concentration was assessed using an enzyme-linked immunosorbent assay and 131I-albumin clearance from joints was assessed using an external gamma counter.

RESULTS

In RA patients, HA concentrations in the SF were increased following IA steroids, while the serum concentrations were decreased. In OA patients, HA concentrations in SF tended to increase initially (decreasing thereafter), and were associated with increased HA concentrations in serum. There were less marked alterations in the AS patients. Albumin clearance rates were decreased significantly (2 weeks postinjection) only in the RA patients. Estimated HA flux revealed discrepancies between the HA concentration and the rate of flux in RA and AS patients.

CONCLUSIONS

These findings suggest that IA steroid injection is associated with a restoration in the relationship between SF and serum HA concentrations toward normal levels.

Intraarticular injections of hyaluronan in patients with cartilage abnormalities and knee pain. A one-year double-blind, placebo-controlled study

OBJECTIVE

To compare the effect of intraarticular injections of hyaluronan and placebo (vehicle, saline) in patients with knee pain on exertion and with joint cartilage abnormalities.

METHODS

Fifty-two patients with arthroscopically verified deep cartilage fissures and villus-like flakes in the symptomatic knee were randomly assigned to receive intraarticular injections of 2.5 ml of either hyaluronan or vehicle, weekly for 5 weeks. The effect was evaluated by both primary and secondary parameters of efficacy at 2, 4, 13, 26, and 52 weeks.

RESULTS

At the followup visits, both groups had improvement from baseline; however, there was no difference between the groups in any of the relevant variables at any time point.

CONCLUSION

The effects of intraarticular hyaluronan do not differ significantly from those of placebo in patients with knee pain and cartilage disease.

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.

Serum concentration of hyaluronan, IgM and IgA rheumatoid factors in a population based study of juvenile chronic arthritis

Increased serum levels of hyaluronan (HA) have been found in patients with liver diseases, psoriasis, malignancies as well as in rheumatoid arthritis and osteoarthritis. In the two latter groups serum HA levels may reflect the extent of synovial involvement and inflammation, rather than only unspecific information. This study was performed to elucidate the value of measuring HA in children with juvenile chronic arthritis (JCA) and to study its relation to class specific rheumatoid factors (IgM Rf and IgA Rf). HA was analysed in sera from 271 patients with JCA and 130 controls using a radiometric assay and IgM Rf and IgA Rf were analysed using an enzyme immunoassay. The results were analysed in relation to JCA subgroup, disease activity and functional outcome. In patients and controls higher levels of HA were found in young children than in older. Raised levels of HA and IgM Rf were mainly found in children with polyarticular disease. Impaired functional outcome was related to raised HA levels. No correlation was found between HA levels and IgM Rf or IgA Rf. Measurement of HA levels in JCA is of no diagnostic value because of low sensitivity. Quantification of HA may, however, have prognostic value in a subgroup of patients belonging to the polyarticular subgroup.

Effects of the molecular weight of hyaluronic acid and its action mechanisms on experimental joint pain in rats

OBJECTIVES

It has been shown previously that hyaluronic acid (HA) has an analgesic action on bradykinin induced pain in the knee joints of rats. This study further clarifies the effects of the molecular weight of HA and its mechanism of action in the same model using HA of molecular weight 800 to 2.3 x 10(6) daltons and a bradykinin antagonist.

METHODS

Bradykinin and the test HA preparations were given to rats by intra-articular injection, and the severity of pain was evaluated by a change in the walking behaviour.

RESULTS

HA with a molecular weight greater than 40 kilodaltons produces analgesic effects with a simultaneous or earlier injection. The ID50 values of HA with molecular weight 40, 310, 860, and 2300 kilodaltons were greater than 2.5, 0.6, 0.07, and 0.06 mg/joint respectively. The duration of the analgesic effect of 860 and 2300 kilodalton HA was 72 hours at 10 mg/ml, whereas that of 310 kilodalton HA was short, being undetectable after 24 hours. The analgesic action of HA of 860 kilodaltons was not changed by pretreatment with four saccharide HA and inhibited by pretreatment with HA larger than six to eight saccharides, capable of binding to HA receptors. Further, HA did not interfere with the analgesic action of the bradykinin antagonist, indicating that HA does not directly bind with bradykinin receptors.

CONCLUSIONS

HA with a molecular weight of greater than 40 kilodaltons produced an analgesic effect, and HA of 860 and 2300 kilodaltons produced high and long-lasting analgesia. These effects of HA appear to be caused by the interaction between HA and HA receptors.

The role of synovial fluid filtration by cartilage in lubrication of synovial joints--I. Mixture model of synovial fluid

A mathematical model of lubrication of human synovial joints under squeeze-film conditions is presented in this several-part paper. Squeeze-film action leads to a concentration of hyaluronic-acid-protein macromolecular complex in the synovial fluid between the approaching cartilage surfaces as a result of the diffusion of water and low molecular weight substances through the cartilage surfaces or along the gap. Increasing viscosity of synovial fluid delays the approach of these surfaces and the formation of stable gels then protects cartilage, if sliding motion ensues, before fluid film lubrication is restored. In Part I of the present paper synovial fluid is considered as a mixture of two incompressible fluids. The material parameters of this mixture of fluids are found using previously published experimental results. Squeeze-film analysis is carried out for the axially symmetric synovial film.

Differential effects of reactive oxygen species on native synovial fluid and purified human umbilical cord hyaluronate

The ability of reactive oxygen species produced by triggered neutrophilic leukocytes, hypoxanthine/xanthine oxidase (HX/XAO), hydrogen peroxide, and hypochlorous acid/myeloperoxidase (HOCl/MPO) systems to degrade hyaluronate (HA) in human synovial fluid (SF) and purified umbilical cord HA was compared by measuring the molecular weight distribution of HA using high-performance liquid chromatography with a size-exclusion column. The exposure of noninflammatory SF to phorbol myristic acetate (PMA)-activated neutrophils or to hydrogen peroxide (H2O2) caused depolymerization of SF HA to the degree corresponding to that found in rheumatoid SFs. When HX/XAO was used as radical generator, the molecular weight of SF HA decreased from 3.42 x 10(6) to 1.40 x 10(4) daltons with concomitant decrease of SF viscosity to 36% from the original value. The HOCl/MPO system caused no depolymerization of SF HA, even at very high unphysiological HOCl concentrations that induced the precipitation of SF HA together with SF proteins. This effect was found to be comparable to conventional mucin clot formation in SF. However, purified human umbilical cord HA was easily depolymerized with HOCl/MPO or with H2O2, but these effects were sensitive to the hydroxyl radical scavenger mannitol and iron chelator desferrioxamine, indicating that the formation of reactive hydroxyl radical (OH.) is likely to participate in these reactions. Thus we conclude that in inflammatory SF HA is mainly depolymerized by OH. produced by decomposition of H2O2 catalyzed by iron, free or locally bound to HA itself. In contrast to what has been reported earlier, HOCl/MPO only depolymerizes purified umbilical cord HA (in a hydroxyl radical-dependent manner) but does not depolymerize HA in SF. As a matter of fact, HOCl/MPO has a scavenging action on SF HA by consuming H2O2 and thus preventing the formation of reactive hydroxyl radicals.

The kinetics of hyaluronan in normal and acutely inflamed synovial joints: observations with experimental arthritis in sheep

The metabolic half-life of hyaluronan (HA) in synovial fluid was estimated in sheep from the rate of appearance of 3H2O in plasma after injection of highly polymerized labeled HA. This material is substituted with 3H in its acetyl group and is rapidly and almost completely degraded in sheep and other species to yield 3H2O. Previously sensitized sheep were studied before and after induction of acute monoarticular arthritis by intraarticular challenge with type II collagen. In both circumstances 3H was released from the joint in a monophasic exponential pattern and appeared in plasma only as 3H2O. Before challenge, the mean metabolic half-life of [3H]HA was 20.8 hours (range, 15.8 to 27.9 hours, n = 5); an estimate in a single unsensitized sheep (27.0 hours) fell within this range. After challenge, swelling occurred around the joint without frankly increased synovial fluid. The mean half-life fell to 11.5 hours (range, 9.0 to 16.8 hours), with a corresponding increase in mean fractional turnover from 3.5%/h to 6.3%/h; an increased amount of the label was also retained within the peripheral tissues. It is concluded that a relatively mild acute inflammation can induce major changes in the metabolic turnover of synovial HA without the development of gross effusions. In the course of this study, mean synovial fluid volume in the normal sheep hock joint was estimated to be 1.54 mL; the concentration and content of HA were 0.54 mg/mL and 0.84 mg, respectively. These data add to other evidence that the volume and HA content of normal synovial fluid vary widely in different joints and species.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of intraarticular administration of hyaluronan in a model of early osteoarthritis in sheep. I. Gait analysis and radiological and morphological studies

Using a model of early osteoarthritis (OA) induced in ovine joints by medial meniscectomy, the intraarticular effects of two hyaluronic acid (HA) preparations (AHA and DHA) were investigated. DHA was an HA preparation with an average molecular weight (MW) of approximately 2.0 x 10(6) d, and AHA had a MW of approximately 8 x 10(5) d. Animals (n = 5) were injected intraarticularly with 1 mL (10 mg/mL) of either HA preparation once a week for 5 weeks beginning 16 weeks after initiation of arthropathy. Meniscectomized, saline (1.0 mL)-injected animals (n = 5) and nonoperated sheep (n = 5) were used for controls. Force-plate analysis of gait and radiographic changes in joints were evaluated in these groups before and after intraarticular treatment. At necropsy, cartilage gross morphology, osteophyte development, and cartilage histopathology were examined. Meniscectomized joints were characterized by erosions and fissuring of cartilage of the medial compartment with areas of decreased matrix staining for proteoglycans. Osteophytes were present at the medial joint margins. Saline-treated meniscectomized animals showed reduced loading of the operated limb using the force plate. Force-plate analysis of walking animals before and after treatment with either AHA or DHA indicated some normalization of joint loading. However, osteophyte scores for meniscectomized joints injected with AHA and DHA were higher after treatment than those of the corresponding saline-treated group. Although the gross cartilage damage was lower than in saline-treated controls for both the HA-treated groups, the histological scores did not support this conclusion. Indeed, the tibial score for the DHA group was higher than for the AHA group (P < .05). These studies confirmed previous reports that meniscectomy of sheep stifle (knee) joints resulted in matrix changes similar to those described for early OA in humans. Both HA preparations appeared to improve gait, suggesting decreased lameness. Increased joint loading associated with gait improvement may account for the higher osteophyte scores in the treated groups. However, cartilage damage with DHA was found to be higher than when the lower-MW HA preparation (AHA) was used.

Pentosan polysulphate and glycosaminoglycan polysulphate stimulate the synthesis of hyaluronan in vivo

Pentosan polysulphate (PPS) and glycosaminoglycan polysulphate (GAGPS) were examined for their ability to alter hyaluronan synthesis in vivo. The inflamed rat subcutaneous air pouch model was used for the study. PPS or GAGPS injected into the air pouch at a dose of 2.5 mg/kg daily for 7 days resulted in higher molecular weight hyaluronan in the pouch fluid compared with control non-drug-treated pouch fluid. The quantity of the hyaluronan was increased by PPS, but not by GAGPS. We concluded that both drugs could be beneficial in the treatment of inflammatory arthritides in which a decrease in normal synovial hyaluronan concentration and molecular weight occurs.

Uridine diphosphoglucose dehydrogenase activity in synovial lining cells in the experimental antigen induced model of rheumatoid arthritis: an indication of synovial lining cell function

Uridine diphosphoglucose dehydrogenase (UDPGD) is the enzyme responsible for the production of uridine diphospho(UDP)-glucuronate, an essential monosaccharide in the biosynthesis of hyaluronan, which is found in high concentrations in normal synovial fluid. Synovial lining cells have been implicated in the synthesis of hyaluronan, but the degree to which they are adapted metabolically to this function in normal and inflamed synovium has not been established. Using a quantitative cytochemical method it was shown that synovial lining cells from chronically inflamed rabbit synovium had significantly lower UDPGD activity per cell than the lining cells of normal synovium. These findings suggest that the lining cells of normal non-inflamed synovium may be enzymatically adapted for the synthesis of hyaluronan and that this may be an indication of a specific role of synovial lining cells in the maintenance of normal joint function.

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.

Catabolism of hyaluronan in the knee joint of the rabbit

Catabolism of hyaluronan was studied by injecting hyaluronan labelled with [125I]-tyramine cellobiose ([125I]-TC) into knee joints of rabbits. After endocytosis [125I]-TC remains intracellularly allowing localization of the site of catabolism. At 6 hours after injection 63% could be recovered in and around the joint, while at 48 hours 32% remained locally. Chromatography showed that 12% of the injected tracer was degraded in joint tissues at 6 hours, increasing to 33% at 24 hours. There was no apparent degradation within the joint fluid. No tracer was found in the regional lymph glands, but 16% of the injected tracer was detected in the liver at 24 hours. This investigation demonstrates that hyaluronan in the joint can be degraded both locally and in the liver.

Hyaluronan solution as a cartilage antidesiccant

During arthrotomy, desiccation of the articular cartilage of synovial joints by the ambient environment of the operating room causes chondrocyte death and may promote degenerative changes within the joint. This study documents the efficacy of a biomaterial, hyaluronan (HY) solution, to maintain chondrocyte viability during desiccation. Rabbit patellar articular cartilage was air-dried for 2 h with and without application of the HY solution. As assessed by 35SO4 uptake and autoradiography, the HY solution helped maintain chondrocyte viability, when compared to air dried specimens (p less than or equal to 0.02). HY solution applied to the articular surfaces of joints undergoing arthrotomy may offset the detrimental effects of desiccation, such as chondrocyte death and degenerative joint changes.

Specific high performance liquid chromatographic determination of the molecular weight and concentration of hyaluronic acid in complex mixtures by labelled hyaluronate binding proteins

A simple High performance liquid chromatographic (HPLC) method for the specific determination of the molecular weight and concentration of hyaluronic acid (HA) in complex mixtures has been developed. Hyaluronate-binding proteins isolated from bovine cartilage labelled by 125I or fluoresceinisothiocyanate were used as specific markers. The specific binding affinities of the markers were compared and were found to have association constants of 1.6 x 10(7) M-1 and 1.2 x 10(7) M-1 respectively. The HA levels and molecular weight distributions can be easily determined in the range 10-500 ng/mL in complex mixtures by the use of markers, molecular sieving HPLC columns and appropriate detectors. It has been demonstrated clearly that the method is useful for the highly specific determination of the parameters in complex biological samples such as serum and synovial fluids and is recommended for clinical applications.

Serum hyaluronate level as a predictor of radiologic progression in early rheumatoid arthritis

Increased serum levels of hyaluronate (HA) have been found in patients with rheumatoid arthritis (RA). This probably reflects increased leakage of HA from the inflamed joints into the circulation. In a prospective study of 40 patients with early RA, we evaluated the relationship of serum HA to clinical, laboratory, and radiologic parameters of disease activity. The patients were followed for 12 months; all had active disease at study entry. We confirmed the previous finding of higher serum HA concentrations in RA patients compared with healthy controls. At study entry, the patients' serum HA levels correlated positively with clinical and laboratory parameters of acute inflammation. Despite marked clinical improvement during therapy with second-line drugs, the serum HA levels increased during the followup period. At the end of 1 year, these levels correlated with the radiologic progression of joint lesions, whereas they showed a less pronounced correlation with clinical or laboratory parameters of inflammation. We conclude that, in early RA, serum HA levels may reflect ongoing joint destruction and may even predict subsequent joint damage.

Serum hyaluronate levels reflect disease activity in experimental arthritis models

Serum hyaluronate (HA) levels were measured in rats subjected to adjuvant or type II collagen induced arthritis. As the arthritic lesions developed, both models showed an increase in serum HA levels of approximately 5 times, from a baseline level of 61-126 ng/ml (range). Furthermore a positive correlation was found between HA level and arthritic score. The increase in HA was not related to metabolic impairment, as the half life of serum HA in adjuvant arthritic rats was similar to that of normal rats. Serum HA may thus serve as a useful variable for evaluation of the severity of experimental arthritis.

Assay of serum hyaluronic acid in clinical application

A sandwich-binding protein assay to determine the concentration of hyaluronic acid (HA) in body fluids has been developed. In this method, a hyaluronic acid binding protein (HABP) was adsorbed to the surface of a solid phase, and HA bound to HABP on the solid phase was detected by biotin-conjugated HABP. The method could assay HA levels within 6 hours using precoated microwells with HABP. HA could be determined in the range of 2-500 micrograms/l by this method using 50 microliters of serum. Within-run precision (CV) was 5.2-10.2%. The specificity of HABP to HA was confirmed by the elimination of the reaction with treatment by hyaluronidase digestion. Serum HA levels (median; range) of patients with rheumatoid arthritis (34; 2-187 micrograms/l) were shown to be higher than those with osteoarthritis (1; 1-21 micrograms/ml) and healthy controls (2; 1-8 micrograms/ml). No correlation between levels of HA and rheumatoid factor was found. HA was demonstrated to be a potential diagnostic marker for rheumatoid arthritis, and this HABP assay could be useful for determination of HA in clinical laboratory tests.

Elevated levels of serum hyaluronate and correlation with disease activity in experimental models of arthritis

The serum hyaluronate (HA) concentration was measured in groups of rats immunized for adjuvant or type II collagen arthritis. Serum HA increased as the arthritic lesions developed, correlating with the severity of the disease. This increase in HA was not related to metabolic impairment, because rats with adjuvant arthritis metabolized intravenously administered tritiated HA at a rate similar to that of normal rats. Serum HA levels may be useful as an indicator of synovitis in experimental and possibly in clinical arthritis. Further, this model could serve as an experimental approach for studies of HA metabolism in chronic joint inflammation.

Canine serum keratan sulfate and hyaluronate concentrations. Relationship to age and osteoarthritis

Elevated serum levels of keratan sulfate (KS) and hyaluronate (HA) in patients with osteoarthritis (OA) have been reported. We measured KS and HA in dogs to determine if there was an elevation of these serum glycosaminoglycans in a canine model of OA. A single intraarticular injection of 1 mg of chymopapain into a shoulder joint increased serum KS by tenfold, and HA by less than twofold, in 24 hours. Serum KS and HA levels were 3-5-fold higher in dogs younger than 2 months of age than in older dogs. Serum KS and HA concentrations and synovial fluid KS concentrations were unrelated to spontaneous cartilage degeneration in 1-year-old dogs. Higher KS levels in synovial fluid correlated with higher KS levels in serum (r = 0.54, P less than 0.025). The mean KS concentration in sera of older dogs (greater than 3 years old) with OA was 37% higher than that in disease-free controls, but the difference between the groups was not statistically significant. Thus, elevated levels of serum KS and HA do not appear to have clinical significance in this model of OA.

The effects of hyaluronic acid on macrophage Fc receptor binding and phagocytosis are independent of the mode of depolymerization

In order to determine whether exposure of hyaluronic acid to oxygen radicals caused an alteration in its properties, independent of the change in molecular weight induced, we examined its effect upon macrophage Fc receptor binding. High molecular weight hyaluronic acid (Healon-Pharmacia) caused a dose dependent inhibition of binding between the concentrations of 0.2-1 mg/ml. At a concentration of 0.3 mg/ml both oxygen radical depolymerized and enzymatically degraded hyaluronic acid caused an inhibition of Fc receptor binding at molecular weights of 1 x 10(6), 1.5 x 10(6) and 2 x 10(6). Oxygen radical degraded hyaluronic acid caused a stimulation of Fc receptor binding at molecular weights of 2 x 10(5) and 3.5 x 10(5), and enzyme degraded hyaluronic acid causes stimulation at a molecular weight of 2.5 x 10(6). Thus this "biological property" of hyaluronic acid is dependent upon molecular weight solely and not upon the mode of depolymerization.

Binding of haptoglobin, inter-alpha-trypsin inhibitor, and alpha 1 proteinase inhibitor to synovial fluid hyaluronate and the influence of these proteins on its degradation by oxygen derived free radicals

Synovial fluid from 201 normal and pathological knee joints was subjected to gel filtration by Sepharose CL-2B chromatography to separate hyaluronic acid (HA) from unbound proteins, which were retarded on this column. HA from all normal fluids was excluded from the gel and contained 1% or less bound protein. Synovial fluids taken from joints of patients with rheumatoid arthritis (RA) contained considerably more protein bound to HA. In 46% of RA samples the level of protein was greater than 4%, whereas only one fluid examined from osteoarthritic joints contained this amount. The proteins bound to HA from RA joints were identified by sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE) and immunodiffusion techniques as the acute phase proteins alpha 1 proteinase inhibitor, inter-alpha-trypsin inhibitor, and haptoglobin. The average relative percentages of these proteins bound to HA were 17.6%, 32.6%, and 29.2% respectively. These HA-protein complexes could be generated in vitro by mixing normal (low protein) HA with any one of the three acute phase proteins. The HA-protein complexes formed in vitro with inter-alpha-trypsin inhibitor or haptoglobin, and those isolated from RA synovial fluids, were more resistant to degradation by oxygen derived free radicals (ODFR) than HA from normal fluids. From these findings we conclude that certain acute phase proteins diffusing into synovial fluid during inflammatory episodes may play an important part in protecting HA from depolymerisation by activated phagocytes.

Analysis by high-performance gel permeation chromatography of hyaluronic acid in animal skins and rabbit synovial fluid

The simultaneous analysis of the molecular weight and concentration of hyaluronic acid in biological samples using high-performance liquid chromatography with two gel permeation columns is described. The elution volumes of various molecular weights of hyaluronic acids were linearily related to the logarithms of their molecular weights up to 600,000. The concentration of hyaluronic acid could be determined in the range from 20 to 100 micrograms/ml, i.e., from 4 to 20 micrograms per 200 microliter injected. The method was applied to the analysis of several animal skin extracts and rabbit synovial fluid. Skin extracts from mouse, rat, guinea-pig and rabbit could be chromatographed without prior isolation and purification. Hyaluronic acids in skin were separated clearly from chondroitin sulphates and their concentrations were determined. The molecular weights were estimated simultaneously to be more than 10(6). Rabbit synovial fluids from intact joints and saline- and carrageenin-treated joints could be chromatographed directly. The chromatograms showed that the concentration of hyaluronic acid in carrageenin-treated synovial fluid is lower than that in saline-treated fluid and the molecular weight distribution is broader. This technique enabled the rapid analysis of hyaluronic acid present at low levels in biological samples.

Clinical trial of intra-articular injection of sodium hyaluronate in patients with osteoarthritis of the knee

A multi-centre randomized, double-blind, parallel-group clinical trial was carried out in 63 patients with osteoarthritis of the knee to compare the efficacy and tolerability of a course of intra-articular injections of 20 mg sodium hyaluronate with a similar course of injections of placebo. Treatment consisted of up to 11 injections over a 23-week period. Evaluation was by means of subjective symptom and activity assessments, serially during the course of treatment and also 25 weeks thereafter. Ten patients (5 of 30 on active treatment; 5 of 33 on placebo) were withdrawn prematurely. Pain on movement, assessed by visual analogue scale (VAS) showed statistically significant (p less than 0.05 to p less than 0.0001) reductions in mean scores throughout the first 11 weeks of treatment with sodium hyaluronate but smaller, non-significant, reductions with placebo treatment. The difference between treatments was significant (p less than 0.05) at 5 weeks. Pain at rest, also assessed by VAS, showed little change in mean scores with placebo but with sodium hyaluronate there was a progressive reduction which was significant (p less than 0.01) throughout the period from 5 to 23 weeks. The difference between sodium hyaluronate and placebo was significant (p less than 0.05 to p less than 0.002) at Weeks 5, 11, 15, 19 and 23. 'Activities of daily living' were assessed using a standard scale. There were small improvements with both treatments, significant at some assessments and somewhat greater with sodium hyaluronate than placebo, but there were no statistically significant differences between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating hyaluronic acid levels vary with physical activity in healthy subjects and in rheumatoid arthritis patients. Relationship to synovitis mass and morning stiffness

We evaluated the possible influence of physical activity on serum levels of hyaluronic acid (HA), plasma levels of elastase, and serum levels of procollagen III peptide. In 15 healthy individuals, HA increased from 26 +/- 9 micrograms/liter (mean +/- SD) before arising from a night's sleep to 54 +/- 24 micrograms/liter 1 hour after arising and performance of normal morning activities (P less than 0.001). HA in 14 patients who had inflammatory arthritis increased from 124 +/- 104 micrograms/liter to 402 +/- 232 micrograms/liter under the same conditions (P less than 0.001). The elevation due to physical activity was significantly (P less than 0.001) higher in patients with rheumatoid arthritis (RA) than that found in controls. A slight increase of HA in the afternoon was also observed in healthy subjects who performed heavy exercise, but a marked increase was seen in RA patients who performed moderate exercise. In another group of 24 RA patients, a more standardized blood sampling was performed before arising and during normal morning activities. An increase in HA was significantly (P less than 0.001) correlated to the synovitis mass, estimated by the Ritchie articular index. Maximum increases of HA were seen 30 and 60 minutes after arising; thereafter, levels decreased to those measured at rest. During the morning activities, procollagen III peptide remained stable, while plasma elastase tended to increase. It is proposed that HA, produced in the joint tissue structures and accumulated at rest, is carried by the lymph vessels to the general circulation during physical activity.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Hyaluronate inhibition of cell proliferation

The proliferation of rabbit synovial cells, 3T3 cells, or simian virus-transformed 3T3 cells in cell culture was inhibited by the addition of hyaluronate to the culture medium. This effect was markedly dependent on the molecular weight and concentration of the hyaluronate. At the molecular weight and concentration of hyaluronate present in normal synovial fluid, proliferation was inhibited. At lower molecular weights or concentrations, as found in rheumatoid synovial fluid, hyaluronate was significantly less inhibitory. Thus, the changes in synovial fluid hyaluronate that are associated with arthropathies may contribute to a favorable environment for rheumatoid pannus expansion.

The role of hyaluronic acid in joint stability--a hypothesis for hip dysplasia and allied disorders

The concentration of hyaluronic acid (HA) and proteins in synovial fluids of hip and shoulder joints of a variety of canine breeds has been investigated. In the Australian Kelpie, a working dog with a low incidence of hip dysplasia, shoulder synovial fluid viscosity and HA concentration were higher than in similar joints of Alsatians in which hip dysplasia is relatively common. Moreover, the HA levels and viscosity in shoulder fluids of animals with clinically defined hip dysplasia were substantially lower than in all other breeds studied. On the basis of these findings, we propose that hip dysplasia and other joint abnormalities may arise as a consequence of a deficiency in the levels of HA in synovial fluids.

Hyaluronic acid degradation by ascorbic acid and influence of iron

The effects of ascorbic acid, iron and ADP on hyaluronic acid, a compound present in inflamed joints, were investigated in an in vitro system. Ascorbic acid induces degradation of hyaluronic acid which increased in the presence of FeCl3 and which is additionally stimulated by ADP chelated ferric ions. The hyaluronic acid degrading reactions induced by the Fe-III/ADP/ascorbic acid system were inhibited by catalase and formate to various extents whereas the presence of superoxide dismutase did not exert any inhibitory effect. Desferrioxamine, a specific iron chelator, completely inhibited hyaluronic acid depolymerisation by ascorbic acid as well as in combination with FeCl3 or FeCl3/ADP, respectively. We suggest that the ultimate hyaluronic acid degrading species is OH, generated via the Fe-III/ADP catalysed Haber Weiss reaction. There is also an indication for the involvement of perferryl or/and ferryl species in the degradation process.

Degradation of hyaluronic acid by polymorphonuclear leukocytes

Degradation (depolymerization) of hyaluronic acid is readily accomplished by superoxide-ion-generating systems, especially those which beget secondary free radicals. It has been presumed, but not confirmed, that this is the mechanism by which neutrophils might alter synovial fluid viscosity. We have demonstrated, in a neutrophil (PMN) superoxide system, physical disruption of the hyaluronate macromolecule using column chromatography and by measurement of intrinsic viscosity. In addition, comparison of calibrated free radical fluxes between a cell-free superoxide system and a neutrophil system revealed very close parallels in iron requirement, inhibition by free radical scavengers, and magnitude of effect. It is concluded that oxygen-derived free radicals are probably the major, if not sole, mechanism by which neutrophils might degrade hyaluronate.