Synovial Constituents Research Articles

Influence of synovia constituents on tribological behaviors of articular cartilage

Abstract The extremely low friction and minimal wear in natural synovial joints appear to be established by effective lubrication mechanisms based on appropriate combination of articular cartilage and synovial fluid. The complex structure of cartilage composed of collagen and proteoglycan with high water content contributes to high load-carrying capacity as biphasic materials and the various constituents of synovial fluid play important roles in various lubrication mechanisms. However, the detailed differences in functions of the intact and damaged cartilage tissues, and the interaction or synergistic action of synovia constituents with articular cartilage have not yet been clarified. In this study, to examine the roles of synovia constituents and the importance of cartilage surface conditions, the changes in friction were observed in the reciprocating tests of intact and damaged articular cartilage specimens against glass plate lubricated with lubricants containing phospholipid, protein and/or hyaluronic acid as main constituents in synovial fluid. The effectiveness of lubricant constituents and the influence of cartilage surface conditions on friction are discussed. In addition, the protectiveness by synovia constituents for intact articular cartilage surfaces is evaluated.

AB0952 Intra-articular low molecular weight hyaluronate reduces platelet influx and matrix metalloproteinase-2 levels in synovial fluid of patients with knee osteoarthritis

BackgroundMatrix metalloproteinaeses (MMPs) are a large family of zinc-dependent endoproteinases that cleave several components of the extracellular matrix (ECM) and that are tightly regulated by tissue type MMP inhibitors (TIMPs)....

Comparative studies on biochemical and cytological constituents of synovial fluids in some farm animals

The goal of the present study was to evaluate the difference in the synovial fluid constituents in cattle, buffaloes, camels, and donkeys. A total number of 20 clinically healthy adult male animals (cattle (N = 5), buffaloes (N = 5), camels (N = 5), and donkeys (N = 5) were subjected to study. Synovial fluid samples were collected from the metacarpophalangeal joint under complete aseptic conditions. The samples were examined physically, cytologically, and biochemically. Synovial fluid analysis revealed significant variations in specific gravity, total leukocyte counts, total proteins, albumin, globulins, glucose levels, and alkaline phosphatase activity among investigated animal species.

Tribocorrosion behavior of β titanium alloys in physiological solutions containing synovial components

In this work, the tribocorrosion behavior of Ti–12.5Mo, Ti–13Nb–13Zr and Ti–29Nb–13Ta–4.6Zr β titanium alloys which are candidate biomaterials for joint prostheses is studied against ultra high molecular weight polyethylene in Hank's balanced salt solution. Ti–6Al–4Fe α+β titanium alloy is also tested for comparison. Experiments were carried out at open circuit potential and at a passive applied potential using a pin-on-flat reciprocating sliding tribo-electrochemical apparatus. The potential, anodic current and friction coefficient were measured in situ as a function of time. The β alloys exhibited a tendency to repassivate during sliding at passive and open circuit potential. The predominant wear mechanism of the metal-polyethylene pairs was 3 body wear, exhibited by the transfer of polyethylene to all titanium alloys. Polyethylene showed a comparatively low wear against β titanium alloys. The effect of the addition of synovial fluid constituents, namely bovine serum albumin, hyaluronic acid and dipalmitoyphosphatidylcholine on the tribocorrosion of Ti–29Nb–13Ta–4.6Zr alloy was also studied. The presence of additives affected the friction coefficient, induced an increase of the wear volume, and a modification of the dominant wear mechanism which was identified as abrasion without transfer of polyethylene.

Synovial fibroblasts self‐direct multicellular lining architecture and synthetic function in three‐dimensional organ culture

To define the intrinsic capacity of fibroblast-like synoviocytes (FLS) to establish a 3-dimensional (3-D) complex synovial lining architecture characterized by the multicellular organization of the compacted synovial lining and the elaboration of synovial fluid constituents. FLS were cultured in spherical extracellular matrix (ECM) micromasses for 3 weeks. The FLS micromass architecture was assessed histologically and compared with that of dermal fibroblast controls. Lubricin synthesis was measured via immunodetection. Basement membrane matrix and reticular fiber stains were performed to examine ECM organization. Primary human and mouse monocytes were prepared and cocultured with FLS in micromass to investigate cocompaction in the lining architecture. Cytokine stimuli were applied to determine the capacity for inflammatory architecture rearrangement. FLS, but not dermal fibroblasts, spontaneously formed a compacted lining architecture over 3 weeks in the 3-D ECM micromass organ cultures. These lining cells produced lubricin. FLS rearranged their surrounding ECM into a complex architecture resembling the synovial lining and supported the survival and cocompaction of monocyte/macrophages in the neo-lining structure. Furthermore, when stimulated by cytokines, FLS lining structures displayed features of the hyperplastic rheumatoid arthritis synovial lining. This 3-D micromass organ culture method demonstrates that many of the phenotypic characteristics of the normal and the hyperplastic synovial lining in vivo are intrinsic functions of FLS. Moreover, FLS promote survival and cocompaction of primary monocytes in a manner remarkably similar to that of synovial lining macrophages. These findings provide new insight into inherent functions of the FLS lineage and establish a powerful in vitro method for further investigation of this lineage.

Friction force microscopy of lubricin and hyaluronic acid between hydrophobic and hydrophilic surfaces

Lubricin and hyaluronic acid (HA), molecular constituents of synovial fluid, have long been theorized to play a role in joint lubrication and wear protection. While lubricin has been shown to function as a boundary lubricant, conflicting evidence exists as to the boundary lubricating ability of hyaluronic acid. Here, we use colloidal force microscopy to explore the friction behavior of these two molecules on the microscale between chemically uniform hydrophilic (hydroxyl-terminated) and hydrophobic (methyl-terminated) surfaces in physiological buffer solution. Behaviors on both surfaces are physiologically relevant since the heterogeneous articular cartilage surface contains both hydrophilic and hydrophobic elements. Friction between hydrophobic surfaces was initially high (μ=1.1, at 100nN of applied normal load) and was significantly reduced by lubricin addition while friction between hydrophilic surfaces was initially low (μ=0.1) and was slightly increased by lubricin addition. At lubricin concentrations above 200 µg/ml, friction behavior on the two surfaces was similar (μ=0.2) indicating that nearly all interaction between the two surfaces was between adsorbed lubricin molecules rather than between the surfaces themselves. In contrast, addition of HA did not appreciably alter the frictional behavior between the model surfaces. No synergistic effect on friction behavior was seen in a physiological mixture of lubricin and HA. Lubricin can equally mediate the frictional response between both hydrophilic and hydrophobic surfaces, likely fully preventing direct surface-to-surface contact at sufficient concentrations, whereas HA provides considerably less boundary lubrication.

Influences of lubricant composition on forming boundary film composed of synovia constituents

In this study, the influences of lubricant composition on adsorption behavior of proteins and stability of protein boundary film were investigated by using total internal reflection fluorescence microscopy (TIRFM). In addition, the adsorption of hyaluronic acid (HA) on rubbed surface was also observed. It was found that the forming of bottom layer of protein boundary film mainly composed of γ-globulin is a key factor to form a stable boundary film and the friction-induced enhancement of forming protein boundary film occurred in appropriate lubricant. In addition, the adsorption of HA on rubbed surface was enhanced by coexistence with γ-globulin and frictional action. It was indicated that a gel-like film is formed due to the introduction of hydrophilic HA molecules into boundary film and it contributes to reduce friction.

Influence of protein and lipid concentration of the test lubricant on the wear of ultra high molecular weight polyethylene

To gain a better understanding of the ultra-high molecular weight polyethylene (UHMWPE) wear mechanism in the physiological environment, the effects of protein and lipid constituents of synovial fluid on the specific wear rate of UHMWPE were examined experimentally. The multidirectional sliding pin-on-plate wear tester was employed to simulate the simplified sliding condition of hip joint prostheses. Bovine serum γ-globulin and synthetic l- α-DPPC were used as model protein and lipid constituents of synovia, respectively. Results of the wear test indicated that the UHMWPE wear rate primarily depended on the protein concentration of the test lubricant. Lipids acted as a boundary lubricant and reduced polyethylene wear in the low protein lubricants. However, the polyethylene wear rate increased with increasing lipid concentrations if the protein concentration was within the physiological level. Increased interactions between protein and lipid molecules and lipid diffusion to polyethylene surface might be responsible for the increased wear.

Boundary lubrication of articular cartilage: Role of synovial fluid constituents

To determine whether the synovial fluid (SF) constituents hyaluronan (HA), proteoglycan 4 (PRG4), and surface-active phospholipids (SAPL) contribute to boundary lubrication, either independently or additively, at an articular cartilage-cartilage interface. Cartilage boundary lubrication tests were performed with fresh bovine osteochondral samples. Tests were performed using graded concentrations of SF, HA, and PRG4 alone, a physiologic concentration of SAPL, and various combinations of HA, PRG4, and SAPL at physiologic concentrations. Static (mu(static, Neq)) and kinetic (<mu(kinetic, Neq)>) friction coefficients were calculated. Normal SF functioned as an effective boundary lubricant both at a concentration of 100% (<mu(kinetic, Neq)> = 0.025) and at a 3-fold dilution (<mu(kinetic, Neq)> = 0.029). Both HA and PRG4 contributed independently to a low mu in a dose-dependent manner. Values of <mu(kinetic, Neq)> decreased from approximately 0.24 in phosphate buffered saline to 0.12 in 3,300 mug/ml HA and 0.11 in 450 mug/ml PRG4. HA and PRG4 in combination lowered mu further at the high concentrations, attaining a <mu(kinetic, Neq)> value of 0.066. SAPL at 200 mug/ml did not significantly lower mu, either independently or in combination with HA and PRG4. The results described here indicate that SF constituents contribute, individually and in combination, both at physiologic and pathophysiologic concentrations, to the boundary lubrication of apposing articular cartilage surfaces. These results provide insight into the nature of the boundary lubrication of articular cartilage by SF and its constituents. They therefore provide insight regarding both the homeostatic maintenance of healthy joints and pathogenic processes in arthritic disease.

1022 生体関節液成分から成る境界膜の形成のその場観察を通した人工軟骨候補材料の摩擦低減メカニズムの考察(G02-2 バイオエンジニアリング(2),G02 バイオエンジニアリング)

The aim of this study is to understand the mechanisms of friction reduction of PVA (poly (vinyl alcohol) hydrogel though in situ observation of forming boundary film composed of synovia constituents. It was found that lubricants that contain hyaluronic acid (HA) and γ-globulin formed thick adsorbed layers compared with those for protein solutions without HA. and the uniformity of boundary film changed with addition ratio of albumin to γ-globulin into lubricants. In addition. lubricants that formed uniform boundary film showed lower friction coefficient. These results indicate that coexistence of HA and protein accelerate the formation of boundary film. It is considered that complexes of HA and proteins form boundary film and the uniform boundary film that is effective in reduction of friction is formed in lubricant with appropriate constituents.

OS2-1-3 IN SITU OBSERVATION OF FORMING BOUNDARY FILM COMPOSED OF SYNOVIA CONSTITUENTS ON RUBBING SURFACE OF ARTIFICIAL CARTILAGE MATERIAL

The aim of this study is to understand the mechanisms of wear reduction of PVA(poly(vinyl alcohol) hydrogel through in situ observation of forming boundary film composed of synovia constituents on the rubbing surface. In this study, reciprocating tester was constructed on the stage in inverted fluorescent microscope. A sliding pair of a spherical reciprocating upper specimen of PVA hydrogel and flat stationary lower specimen of cover glass was prepared. Solution of 0.5wt% sodium hyaluronate (HA) was used as base lubricant and fluorescent-labeled albumin and γ-globulin were used as additives. Rubbing surface was observed through a cover glass of lower specimen and images of rubbing surface were recorded at periodic interval. Lubricants with single protein showed that albumin adsorbed loosely on rubbing surface, whereas γ-globulin adsorbed tightly. When both of albumin and γ-globulin were added to lubricants, thickness of adsorbed layer was increased as compared to that for protein solutions without HA, and lubricant with 1:2 ratio of albumin to γ-globulin at total concentration of 2.1wt% formed the most uniform and stable boundary film. In addition, lubricants in which uniform boundary film was formed showed lower friction coefficient. These results indicate that coexistence of HA and proteins accelerate the formation of boundary film and it is considered that uniform boundary film that is effective in lowering friction is formed in lubricant with appropriate constituents.

Dependence of the Friction-Wear Characteristics of Artificial Joints on Contact Pressure

The purpose of this study was to examine the dependence of the friction-wear characteristics of artificial joints on contact pressure. Test specimens used were ultra-high molecular weight polyethylene (UHMWPE), Co-Cr-Mo alloy and alumina ceramics in the materials of artificial joints. Lubricating liquid was a water-based liquid that contained the principal constituents of synovial fluid. The wear of UHMWPE sliding against Co-Cr-Mo alloy and alumina ceramics decreased with the increase of contact pressure and indicated dependence on contact pressure. Surface roughness on the rubbed area of Co-Cr-Mo alloy and alumina ceramic discs had a tendency to decrease with the increase of contact pressure. Therefore, it was considered that the dependence on contact pressure was effected by the decrease of surface roughness on the rubbed area of the discs.

Kynurenic acid, an endogenous constituent of rheumatoid arthritis synovial fluid, inhibits proliferation of synoviocytes in vitro

Kynurenic acid is an antagonist of ionotropic glutamate receptors. It has been found that glutamate antagonists inhibit proliferation of different human tumor cells. Since the hyperplasia of synovial fibroblasts is one of the most striking features of inflammatory arthritis, the main goals of this study were detection and quantification of kynurenic acid in synovial fluid obtained from patients with rheumatoid arthritis, and determination of its effect on proliferation of synoviocytes in vitro. Presence of kynurenic acid was determined by HPLC in all 58 samples of synovial fluid. The mean concentration was 15.89 pmol/ml. Kynurenic acid inhibited synoviocyte proliferation with the IC50 value of 5.9 mM. In subthreshold concentration of 0.3 mM it enhanced antiproliferative action of celecoxib and nimesulide. In conclusion, the presence of kynurenic acid in synovial fluid was documented in patients with rheumatoid arthritis. Its potential role as an endogenous substance, controlling synoviocyte proliferation can be suggested.

1231 人工股関節における摩擦部位の温度が摩耗特性と摩耗粉形態に及ぼす影響(G02-5 関節と軟骨(2),G02 バイオエンジニアリング)

The temperature of femoral head in artificial hip joints rose up more than 40℃ during walking. If the temperature of 40℃ or higher is maintained for a long time, it may become the cause of the increase of wear. The purpose of this study was to investigate the influence of the temperature of friction part in femoral head on wear characteristics and wear debris in artificial hip joints. The temperature of friction part was adjusted at 30, 36, 40 and 42℃ with a temperature controller. Lubricating liquids used a phosphate buffered saline (PBS) and the PBS that contained the principal constituents of synovial fluid. Wear depth increased with the increase of the temperature of friction part. There were no significant differences in the wear debris between temperatures of 30 and 42℃.

Effect of Dissolved Oxygen in Lubricating Liquid on Tribological Characteristic of Metal-on-Metal Artificial Hip Joint.

It is known that the metallic oxide film of bearing surfaces markedly affects the wear process. Influence of dissolved oxygen in the lubricating liquid containing principal constituents of synovial fluid on wear characteristics of Co-Cr-Mo alloy used in a metal-on-metal artificial hip joint has been investigated by using a pin-on-plate wear machine. Concentration of the dissolved oxygen was adjusted by N2 injection in the enclosure which covered pin and plate. It was observed that the decrease in oxygen concentration, which was similar to be in vivo, caused the wear to decrease. The material properties of the bearing surface were controlled by the oxygen concentration. The bearing surface tended to be smooth in lower oxygen concentrations. The friction coefficient increased in the low oxygen concentration. The experimental results indicated that the decrease in oxygen concentration made the adhesion between bearing surfaces increase. The increase in adhesion leads to a high frictional force. The high adhesion and frictional force brought about work hardening and fine structure of the bearing surface, so that the wear was decreased.

Surface fissures in articular cartilage: effect of pathological changes in synovial fluid

Objective. A unified mathematical model of two different modes of inception of fissures at the surface of articular cartilage in healthy and pathological joints. Design. The superficial tangential zone of articular cartilage is modeled as a three-phase medium consisting of collagen fibers, matrix, and of infiltrated thin constituent of synovial fluid. Background. The author’s general mesomechanical concept is applied to the analysis of deterioration of articular cartilage. Methods. Theoretical analysis based on the results of the author’s preceding paper. Results. The presented analysis shows that superficial fissures in articular cartilage can also be caused by pathological thinning of synovial fluid. Conclusions. Whereas in healthy joints the probable cause of creation of fissures at the surface of cartilage was shown to be fast impact loading, in joints with inflammatory synovial fluid the fissures can be caused by plain walking. Relevance Appearance of surface fissures in articular cartilage is a serious, still not fully clarified problem that deserves attention.

Intra-articular hyaluronan: A disease modifying therapy?

Hyaluronan (HA) is a macromolecular glycosaminoglycan which is an important constituent of both synovial fluid and the extracellular matrix of cartilage. Research into the functions of HA have suggested a number of different biophysical, biochemical and cell regulatory roles in joint synovial tissues. Intra-articular HA therapy is now widely used in various countries for the treatment of osteoarthritis (OA) in both humans and animals. Numerous high purity pharmaceutical preparations are commercially available which have a variety of forms and molecular weights ranging from less than 1.0 × 106 Da (generally regarded as low molecular weight) up to 3–6.0 × 106 Da (high molecular weight). This range of molecular weights in the commercially available preparations is a direct reflection of the variation in results derived from both in vitro and in vivo studies of the use of HA in various experimental models. Intra-articular HA therapy has been registered by some companies as a device rather than a drug, which reflects both the initial theory that HA exerted its action through viscosupplementation of deficient synovial fluid, and the current scientific debate as to the specific therapeutic effects of HA on synovial tissues. Significant research is ongoing to further define the likely multiple actions of HA on joint tissues. The discovery that HA is rapidly cleared from joints after intra-articular injection, coupled with the realization that the symptomatic relief experienced by human OA patients treated by intra-articular HA, together suggest that viscosupplementation is not the only mode of action of HA. Studies in various animal models of inflammation and pain have supported an anti-inflammatory action of HA in joint disease. In vivo animal studies using models of OA suggest that low molecular weight HA provides better protection of cartilage than high molecular weight preparations. This is in direct contrast to the results of in vitro studies using chondrocyte or cartilage explant cultures in which high molecular weight HA preparations were found to be more effective at protecting cartilage from degradation than low molecular weight preparations. Evidence that low molecular weight forms of HA penetrate the joint tissues more deeply is a partial explanation for this, as it is likely that the low molecular weight HA is able to achieve higher concentrations of the drug in the pericellular environment. However, recent research has provided additional evidence of specific interaction between HA, various cell receptors such as CD44. This, together with other studies in cell biology which have demonstrated that signal transduction and gene expression arise from HA receptor binding suggest an immunoregulatory role for HA. Our present knowledge of interactions of HA at the cellular and molecular level is still inadequate, but there is strong evidence from animal model experiments as well as from studies on human synovial biopsies that the positive effects exhibited by HA in OA joints are largely mediated by its anti-inflammatory, cytoprotective and immunoregulatory properties. There is significant scientific evidence that intra-articular HA therapy can provide cartilage protection. However, this probably does not arise from a direct effect of HA on chondrocytes, but rather is secondary to the down regulation of cytokine, free radical and proteolytic activities in the synovial fluid and synovium, all of which can adversely affect chondrocyte metabolism.

211 人工関節用 Co-Cr-Mo 合金のトライボ特性に及ぼす潤滑液溶存酸素の影響

It has been proposed that the oxide film on metallic bearing surfaces improves its corrosion resistance and decreases wear. Influence of dissolved oxygen in the lubricating liquid containing principal constituents of synovial fluid on wear characteristics of Co-Cr-Mo alloy used in a metal-on-metal artificial hip joint has been investigated by using a pin-on-plate wear machine. Decrease in the concentration of dissolved oxygen caused the wear to decrease, in which the concentration was approximately the same value in vivo. The material properties of the bearing surface are probably controlled by the oxygen concentration. The friction coefficient increased in the low oxygen concentration. This indicates that the decrease in the oxygen concentration makes the adhesion between the bearing surfaces increase. The increase in the adhesion leads to the high frictional force. The high adhesion and frictional force affected work hardening and refinement of the bearing surface, so that the wear was decreased.

Is there a place for intra-articular hyaluronate in osteoarthritis of the knee?

Viscosupplementation refers to the intra-articular injection of hyaluronic acid (HA) as a hyaluronate to relieve pain and improve function, usually in patients with knee OA. HA is the major constituent of a 1–2-μm layer on the surface of articular cartilage as well as a major constituent of synovial fluid (SF). Solutions of HA can act as lubricants when movements are slow and as shock absorbers when movements are fast. In arthritis, the molecular weight of HA is reduced, and so are its properties. Viscosupplementation has been advocated as a way of reversing this, but intra-articular HA has other properties, such as an anti-inflammatory effect, which may also contribute to any therapeutic effect. There is a large placebo effect from intra-articular injections, and the benefits of intra-articular glucocorticoids may be only slightly better than this effect. In only one randomised, placebo-controlled trial was the difference in response significant. Studies of intra-articular HA also show a marked placebo response (where it has been measured), but some have suggested a measurable benefit, which may be more prolonged that that of glucocorticoids. There is only a single study in which the effects of intra-articular therapy with placebo, glucocorticoids and viscosupplementation can be compared. Here, HA may have had a slightly longer period of benefit than triamcinolone hexacetonide or placebo. The very large placebo response after aspiration of the knee may seriously mislead those engaged in uncontrolled therapeutic evaluation of intra-articular therapy. Current evidence suggests that viscosupplements probably provide a similar level of pain relief to glucocorticoids and do so for several months, but the onset is slower, and there is the potential for local adverse reactions.

Differences in the concentration of various synovial fluid constituents between the distal interphalangeal joint, the metacarpophalangeal joint and the navicular bursa in normal horses

As a prerequisite for the identification of navicular disease markers, the concentrations of cartilage oligomeric matrix protein (COMP), total glycosaminoglycans (GAG), hyaluronan, metalloproteinases (MMP) 2 and 9 and total protein were measured in synovial fluid samples obtained from the distal interphalangeal joint (DIP), the metacarpophalangeal joint (MCP) and the navicular bursa of 24 horses. Mean GAG, COMP and total protein levels were significantly higher in the DIP joint and in the navicular bursa compared to the MCP joint. Hyaluronan content was lower. MMP -2 activity was present in all fluids measured and had similar levels in different joints. MMP -9 was present in 42 per cent of MCP joint samples and 58 per cent of DIP joint samples and of navicular bursal samples. In relation to the constituents measured, the composition of navicular bursal fluid was similar to the articular synovial fluids, in particular that obtained from the DIP joint. Correlation between the constituents ofDIP joint fluid and navicular bursal fluid obtained from the same legs was statistically significant for all the parameters measured.