Differential levels of synovial fluid aggrecan aggregate components in experimental osteoarthritis and joint disuse

Therapeutic Effects of Olive and Its Derivatives on Osteoarthritis: From Bench to Bedside

Osteoarthritis is a major cause of morbidity among the elderly worldwide. It is a disease characterized by localized inflammation of the joint and destruction of cartilage, leading to loss of function. Impaired chondrocyte repair mechanisms, due to inflammation, oxidative stress and autophagy, play important roles in the pathogenesis of osteoarthritis. Olive and its derivatives, which possess anti-inflammatory, antioxidant and autophagy-enhancing activities, are suitable candidates for therapeutic interventions for osteoarthritis. This review aimed to summarize the current evidence on the effects of olive and its derivatives, on osteoarthritis and chondrocytes. The literature on animal and human studies has demonstrated a beneficial effect of olive and its derivatives on the progression of osteoarthritis. In vitro studies have suggested that the augmentation of autophagy (though sirtuin-1) and suppression of inflammation by olive polyphenols could contribute to the chondroprotective effects of olive polyphenols. More research and well-planned clinical trials are required to justify the use of olive-based treatment in osteoarthritis.

Elevated aggrecanase activity in a rat model of joint injury is attenuated by an aggrecanase specific inhibitor

OBJECTIVE

To evaluate aggrecanase activity after traumatic knee injury in a rat model by measuring the level of aggrecanase-generated Ala-Arg-Gly-aggrecan (ARG-aggrecan) fragments in synovial fluid, and compare with ARG-aggrecan release into joint fluid following human knee injury. To evaluate the effect of small molecule inhibitors on induced aggrecanase activity in the rat model.

METHOD

An enzyme-linked immunosorbent assay (ELISA) was developed to measure ARG-aggrecan levels in animal and human joint fluids. A rat model of meniscal tear (MT)-induced joint instability was used to assess ARG-aggrecan release into joint fluid and the effects of aggrecanase inhibition. Synovial fluids were also obtained from patients with acute joint injury or osteoarthritis and assayed for ARG-aggrecan.

RESULTS

Joint fluids from human patients after knee injury showed significantly enhanced levels of ARG-aggrecan compared to uninjured reference subjects. Similarly, synovial fluid ARG-aggrecan levels increased following surgically-induced joint instability in the rat MT model, which was significantly attenuated by orally dosing the animals with AGG-523, an aggrecanase specific inhibitor.

CONCLUSIONS

Aggrecanase-generated aggrecan fragments were rapidly released into human and rat joint fluids after injury to the knee and remained elevated over a prolonged period. Our findings in human and preclinical models strengthen the connection between aggrecanase activity in joints and knee injury and disease. The ability of a small molecule aggrecanase inhibitor to reduce the release of aggrecanase-generated aggrecan fragments into rat joints suggests that pharmacologic inhibition of aggrecanase activity in humans may be an effective treatment for slowing cartilage degradation following joint injury.

Novel synovial fluid recovery method allows for quantification of a marker of arthritis in mice

OBJECTIVE

We evaluated three methodologies--a calcium sodium alginate compound (CSAC), polyacrylate beads (PABs), and Whatman paper recovery (WPR)--for the ability to recover synovial fluid (SF) from mouse knees in a manner that facilitated biochemical marker analysis.

METHODS

Pilot testing of each of these recovery vehicles was conducted using small volumes of waste human SF. CSAC emerged as the method of choice, and was used to recover and quantify SF from the knees of C57BL/6 mice (n=12), six of which were given left knee articular fractures. SF concentrations of cartilage oligomeric matrix protein (COMP) were measured by enzyme-linked immunosorbent assay.

RESULTS

The mean concentration ratio [(COMP(left knee))/(COMP(right knee))] was higher in the mice subjected to articular fracture when compared to the non-fracture mice (P=0.026). The mean total COMP ratio (taking into account the quantitative recovery of SF) best discriminated between fracture and non-fracture knees (P=0.004).

CONCLUSIONS

Our results provide the first direct evidence of accelerated joint tissue turnover in a mouse model responding to acute joint injury. These data strongly suggest that mouse SF recovery is feasible and that biomarker analysis of collected SF samples can augment traditional histological analyses in mouse models of arthritis.

Evaluation of serum chondroitin sulfate and hyaluronan: biomarkers for osteoarthritis in canine hip dysplasia

Hip dysplasia (HD) is one of the most important bone and joint diseases in dogs. Making the radiographic diagnosis is sometime possible when the disease has markedly progressed. Chondroitin sulfate (CS) and hyaluronan (HA) are the most important cartilage biomolecules that are elevated in the serum taken from dogs with osteoarthritis. The serum CS and HA can be detected by an ELISA technique, with using monoclonal antibodies against CS epitope 3B3 and WF6 and the HA chain as the primary antibodies. The aim of this study was to compare the levels of serum CS (both epitopes) and HA in non-HD and HD dogs. All 123 dogs were categorized into 2 groups. The non-HD group was composed of 98 healthy dogs, while the HD group was comprised of 25 HD dogs. Blood samples were collected for analyzing the serum CS and HA levels with using the ELISA technique. The results showed that the average serum level of the CS epitope WF6 in the HD group (2,594 ± 3,036.10 ng/ml) was significantly higher than that in the non-HD group (465 ± 208.97 ng/ml) (p < 0.01) while the epitope 3B3 in the HD group (105 ± 100.05 ng/ml) was significantly lower than that in the non-HD group (136 ± 142.03 ng/ml) (p < 0.05). The amount of serum HA in the HD group (134.74 ± 59.71 ng/ml) was lower than that in the non HD group (245.45 ± 97.84 ng/ml) (p < 0.05). The results indicate that the serum CS and HA levels might be used as biomarkers for osteoarthritis in HD dogs.

Serum and synovial fluid concentrations of keratan sulfate and hyaluronan in dogs with induced stifle joint osteoarthritis following cranial cruciate ligament transection

OBJECTIVE

To examine longitudinal changes in serum and synovial fluid concentrations of keratan sulfate (KS) and hyaluronan (HA) after cranial cruciate ligament (CCL) transection in dogs.

ANIMALS

12 clinically normal adult mixed-breed dogs.

PROCEDURE

Following CCL transection in the right stifle joint, KS and HA concentrations were determined in serum and neat (undiluted) synovial fluid prior to and 1, 2, 3, and 12 months after surgery. Postsurgical dilution of synovial fluid was corrected by use of urea as a passive marker.

RESULTS

Synovial fluid KS and HA concentrations decreased at 1, 2, and 3 months after surgery in operated stifle joints, compared with baseline values. Synovial fluid KS concentration decreased in unoperated stifle joints at 1 month. A decrease in synovial fluid KS concentration was found in operated stifle joints, compared with unoperated stifle joints, at 2 and 3 months, and a decrease in synovial fluid HA concentrations was also found in operated stifle joints, compared with unoperated stifle joints, at 1, 2, and 3 months. Serum KS concentrations increased from baseline values at 3 months after surgery. Hyaluronan concentrations in operated stifle joints were lower than baseline values at 1, 2, and 3 months. Urea-adjusted synovial fluid concentrations revealed that dilution did not account for the decline in biomarker concentrations.

CONCLUSIONS AND CLINICAL RELEVANCE

The initial decrease and subsequent increase in synovial fluid concentrations of HA and KS may be caused by an acute inflammatory response to surgical intervention that negatively affects cartilage metabolism or an increase in production of immature proteoglycans.

Temporal regulation of chondrocyte metabolism in agarose constructs subjected to dynamic compression

The temporal response of chondrocyte metabolism in agarose constructs subjected to different dynamic compression regimes was investigated. The current study explored the effects of continuous or intermittent compression using various duty cycles of dynamic compressive loading, over a 48 h culture period. For the continuous compression experiments, duty cycles ranged from 5400 to 172,800 and intermittent compression delivered a total of 86,400 cycles. Large numbers of duty cycles significantly stimulated proteoglycan synthesis with maximal levels obtained for constructs subjected to 12h of intermittent compression. The shortest duration of intermittent compression suggested that further cycles are inhibitory for cell proliferation. Nitrite release was independent of the length or type of compressive regime applied. The uncoupled nature of the metabolic response determined in this study suggests that mechanical conditioning regimes may be fine tuned to selectively stimulate key metabolic parameters of relevance to cartilage tissue engineering.

A comparison of various therapeutic exercises on the functional status of patients with knee osteoarthritis

OBJECTIVE

To investigate the therapeutic effects of different muscle-strengthening exercises on the functional status of patients with knee osteoarthritis (OA).

METHODS

One hundred thirty-two patients with bilateral knee OA (Altman Grade II) were sequentially divided into 4 random groups (GI to GIV). The patients in group I received isokinetic muscle-strengthening exercise, group II received isotonic muscle-strengthening exercise, group III received isometric muscle-strengthening exercise, and group IV acted as controls. The changes of muscle power of leg flexion and extension were measured with a Kinetic Communicator dynamometer, and patients' functional status was evaluated by visual analogue scale, ambulation speed, and Lequesne index before and after treatment, and at the follow-up 1 year later.

RESULTS

The results showed that the patients with OA in each treated group had significant improvement in pain reduction, disability reduction, and in walking speed after treatment and at follow-up when compared with their initial status. Isotonic exercise had the greatest effect on pain reduction after treatment, and fewer participants discontinued the treatment because of exercise knee pain. Isokinetic exercise caused the greatest increase of walking speed and decrease of disability after treatment and at follow-up. The greatest muscle-strength gain in 60 degrees /second angular velocity peak torques was found in the isokinetic and isotonic exercise groups. A significant muscle-strength gain in 180 degrees /second angular velocity peak torques was found only in the isokinetic group after treatment.

CONCLUSION AND RELEVANCE

Isotonic exercise is suggested for initial strengthening in patients with OA with exercise knee pain, and isokinetic exercise is suggested for improving joint stability or walking endurance at a later time.

Inhibition of articular cartilage degradation by glucosamine-HCl and chondroitin sulphate

Glucosamine and chondroitin sulphate in many animal and human trials has improved joint health. In vitro studies are beginning to clarify their mode of action. The objective of this research was to: 1) determine at what concentrations glucosamine-HCl (GLN) and/or chondroitin sulphate (CS) would inhibit the cytokine-induced catabolic response in equine articular cartilage explants and 2) to determine if a combination of the 2 was more effective at inhibiting the catabolic response than the individual compounds. Articular cartilage was obtained from carpal joints of horses (age 1-4 years). Cartilage discs (3.5 mm) were biopsied and cultured. Explants were incubated with lipopolysaccharide (LPS) in the presence of varying concentrations of GLN, CS, or both. Control treatments included explants with no LPS and LPS without GLN or CS. Media were analysed for nitric oxide (NO), prostaglandin E2 (PGE2) and keratan sulphate. Cartilage was extracted for analysis of metalloproteinases (MMP). Four experiments were conducted. In all experiments, GLN at concentrations as low as 1 mg/ml decreased NO production relative to LPS stimulated cartilage without GLN over the 4 day period. In general, CS at either 0.25 or 0.5 mg/ml did not inhibit NO production. The addition of CS to GLN containing media did not further inhibit NO production. GLN at concentrations as low as 0.5 mg/ml decreased PGE2 production, whereas CS did not effect on PGE2. The combination of GLN/CS decreased MMP-9 gelatinolytic activity but had no effect on MMP-2 activity. The combination in 2 experiments tended to decrease MMP-13 protein concentrations and decreased keratan sulphate levels in media. Overall, the combination of GLN (1 mg/ml) and CS (0.25 mg/ml) inhibited the synthesis of several mediators of cartilage degradation. These results further support the effort to understand the role of GLN and CS in preserving articular cartilage in athletic horses.

Altered swelling behavior of femoral cartilage following joint immobilization in a canine model

Periods of reduced joint loading have been shown to induce changes in the biochemical composition. metabolism and mechanics of articular cartilage. In this study, changes in cartilage swelling behavior were studied following a 4-week period of joint immobilization, using a recently developed osmotic loading technique [J. Biomech, 32 (1999) 401-408]. The magnitude and distribution of swelling strains were measured in cartilage-bone samples equilibrated in physiological and hypotonic saline, relative to a hypertonic reference NaCl solution. Physicochemical parameters (glycosaminoglycan fixed charge density and water volume fraction) were determined in site-matched cartilage samples. The experimental data for swelling strains, fixed charge density and water volume fraction were used with a triphasic mechano-chemical theory [J. Biomech. Eng. 113 (1991) 245-258] to determine the effect of joint immobilization on the tensile modulus of the cartilage solid matrix. Four weeks of immobilization resulted in a significant increase in the magnitude of swelling-induced strains, and a significant decrease in fixed charge density in cartilage, as compared with the contralateral controls. Joint immobilization also resulted in decreases in values for the modulus of cartilage, as compared with the contralateral controls. Our results suggest that 4 weeks of joint immobilization had a significant effect on cartilage mechanical function that may be linked to collagen changes in the cartilage extracellular matrix.

In situ compressive stiffness, biochemical composition, and structural integrity of articular cartilage of the human knee joint

OBJECTIVE

Reduction of compressive stiffness of articular cartilage has been reported as one of the first signs of cartilage degeneration. For the measurement of in situ compressive stiffness, a hand-held indentation probe has recently been developed and baseline data for macroscopically normal knee joint cartilage were provided. However, the histological stage of degeneration of the measured cartilage was not known. The purpose of this study was to investigate whether there is a relationship between the in situ measured compressive stiffness, the histological stage of degeneration, and the biochemical composition of articular cartilage.

DESIGN

Instantaneous compressive stiffness was measured for the articular cartilage of 24 human cadaver knees. Additionally, biochemical composition (total proteoglycan and collagen content) and histological appearance (according to the Mankin score) were assessed for each measurement location.

RESULTS

Despite visually normal surfaces, various histological signs of degeneration were present. A high correlation between Mankin score and cartilage stiffness was observed for the lateral patellar groove (R(2)=0.81), the medial (R(2)=0.83) and the lateral femoral condyle (R(2)=0.71), whereas a moderate correlation was found for the medial patellar groove (R(2)=0.44). No correlation was observed between biochemical composition and cartilage compressive stiffness.

CONCLUSIONS

Our results are in agreement with others and show that the instantaneous compressive stiffness is primarily dependent on the integrity of the extracellular matrix, and not on the content of the major cartilage constituents. The high correlation between stiffness and Mankin score in mild osteoarthrosis suggests that the stage of cartilage degeneration can be assessed quantitatively with the hand-held indentation probe. Moderate and severe case of osteoarthrosis remains to be investigated.

Decline after immobilisation and recovery after remobilisation of synovial fluid IL1, TIMP, and chondroitin sulphate levels in young beagle dogs

OBJECTIVE

To monitor the concentration of markers of cartilage and synovium metabolism in the knee (stifle) joint synovial fluid of young beagles subjected to immobilisation and subsequent remobilisation.

METHODS

The right hind limb of 17 dogs was immobilised in flexion for 11 weeks. Simultaneously, the contralateral left knee was exposed to increased weight bearing. The remobilisation period lasted 50 weeks. Litter mates served as controls. The concentration in joint lavage fluid of interleukin 1alpha (IL1alpha) was measured by immunoassay, the activity of phospholipase A(2) (PLA(2)) was determined by an extraction method, chondroitin sulphate (CS) concentration by precipitation with Alcian blue, hyaluronan (HA) by an ELISA-like assay using biotinylated HA-binding complexes, matrix metalloproteinase 3 (MMP-3), and tissue inhibitor of metalloproteinases 1 (TIMP-1) by sandwich ELISA, and synovitis was scored by light microscopy.

RESULTS

Synovitis or effusion was absent in all experimental and control groups. Immobilisation decreased the joint lavage fluid levels of IL1alpha (p<0.05), TIMP (p< 0.05), and the concentration of CS down to 38% (p<0.05) in comparison with untreated litter mates with normal weight bearing. Immobilisation did not affect the activity of PLA(2), or the concentration of MMP-3 or HA in synovial fluid. Joint remobilisation restored the decreased concentrations of markers to control levels. Increased weight bearing did not change the concentrations of markers in comparison with the control joints with normal weight bearing.

CONCLUSIONS

11 weeks' joint immobilisation decreased the concentration of markers of cartilage and synovium metabolism in the synovial fluid, and remobilisation restored the concentrations to control levels. The changes in joint metabolism induced by immobilisation, as reflected by the markers, are thus different from those found in osteoarthritis, where increased levels of these markers are associated with enhanced degradation and synthesis. These findings suggest that the change induced in joint metabolism by immobilisation is reversible in its early stages.

In vitro evaluation of the effect of dimethyl sulfoxide on equine articular cartilage matrix metabolism

OBJECTIVE

To evaluate the effects of dimethyl sulfoxide (DMSO) on equine articular cartilage matrix metabolism.

STUDY DESIGN

Using a cartilage explant culture system, proteoglycan (PG) synthesis, PG release, lactate metabolism, chondrocyte viability, and metabolism recovery were determined after cartilage exposure to DMSO.

SAMPLE POPULATION

Cartilage harvested from metacarpophalangeal and metatarsophalangeal joints of 12 horses (age range, 1 to 10 years).

METHODS

Explants were exposed to concentrations of DMSO (1% to 20%) for variable times (3 to 72 hours). PG synthesis and release were determined by a radiolabel incorporation assay and dimethylmethylene blue (DMMB) dye assay, respectively. Lactate released into culture media was measured, and chondrocyte viability was assessed using the Formizan Conversion Assay and a paravital staining protocol. Metabolism recovery was assessed in explants that were allowed to recover in maintenance media after exposure to DMSO.

RESULTS

PG synthesis and lactate metabolism were inhibited in a dose- and time-dependent manner after exposure to DMSO concentrations > or = 5%; there was no significant alteration in PG release. No change in chondrocyte viability was detected after incubation with DMSO. PG synthesis and lactate metabolism returned to baseline rates when allowed a recovery period after exposure to DMSO.

CONCLUSIONS

DMSO concentrations > or = 5% suppress equine articular cartilage matrix metabolism. Suppression of PG synthesis and lactate metabolism is reversible and does not appear to be the result of chondrocyte death.

CLINICAL RELEVANCE

Equine clinicians adding DMSO to intraarticular lavage solutions should be aware that DMSO may have deleterious effects on equine articular cartilage matrix metabolism.

Longitudinal characterization of synovial fluid biomarkers in the canine meniscectomy model of osteoarthritis

Damage to the meniscus can lead to posttraumatic osteoarthritis. Early markers of joint injury and tissue disease may be useful in developing and administering clinical treatment. We investigated the effects of total medial meniscectomy on biomarkers measured serially in synovial lavage fluid each month for 3 months. Following meniscectomy in dogs, four biomarkers were evaluated: cartilage oligomeric matrix protein, keratan sulfate epitope (5D4), the 3B3(-) neoepitope of chondroitin-6-sulfate, and the 3B3(+) chondroitinase-generated epitope of chondroitin-6-sulfate. Meniscectomy led to statistically significant elevations of all four biomarkers, with levels peaking at 4 weeks. By 12 weeks, the level of the 5D4 epitope returned to the preoperative baseline level whereas that of cartilage oligomeric matrix protein, 3B3(-), and 3B3(+) remained above the baseline. Concentrations of these biomarkers in the knees not operated on did not change significantly from the baseline. The levels of cartilage oligomeric matrix protein and 3B3(-) relative to 3B3(+) remained constant in all knees. In contrast, the level of 5D4 relative to 3B3(+) declined over time in the knee operated on but remained constant in the knee not operated on. These results demonstrate a quantitative change in the molecular components of synovial fluid after meniscectomy, as well as a qualitative change evinced by an alteration in the relative proportions of these epitopes. Extensive analyses showed a strong correlation between serum levels of 3B3(-) from the femoral and cephalic veins; however, serum 3B3(-) was not correlated with synovial fluid 3B3(-). These findings support the hypothesis that the concentrations of select cartilage biomarkers in synovial fluid are altered following meniscectomy and are promising tools for objectively monitoring the induction of osteoarthritis in this model system.

Load-controlled compression of articular cartilage induces a transient stimulation of aggrecan gene expression

The effects of short- and long-term load-controlled compression on the levels of aggrecan mRNA have been determined. Results show that a compressive stress of 0.1 MPa on bovine articular cartilage explants for 1, 4, 12, and 24 h produces a transient up-regulation of aggrecan mRNA synthesis. At 1 h, aggrecan mRNA levels in loaded explants were increased 3.2-fold compared to control explants. At longer times (>/=4 h), the levels of aggrecan mRNA returned to baseline values or stayed slightly higher. There is a dose dependence in the response of the explant to increasing levels of compressive stress (0-0.5 MPa) for 1 h. Aggrecan mRNA levels increased 2- to 3-fold at 0-0.25 MPa. At 0.5 MPa, the level of aggrecan mRNA was lower than those at 0.1 and 0.25 MPa. This dose-dependent effect suggests a reversal of the stimulatory effects of compression on aggrecan gene expression at higher loads. After 24 h of compression, the levels of aggrecan mRNA in explants subjected to any of the stress levels were not significantly different from those in control explants. The stimulatory effect of 0.1 MPa compressive stress on aggrecan mRNA levels was blocked by Rp-cAMP and U-73122, indicating the involvement of the classical signal transduction pathways in the mechanical modulation of aggrecan gene expression. The responses of link protein mRNA to compression paralleled those of aggrecan, while there was no significant change in expression of the gene for the housekeeping protein elongation factor-1 alpha. The results indicate that articular cartilage chondrocytes can respond to short-term compressive loads by transiently up-regulating expression of the aggrecan gene. The fact that long-term compression did not significantly alter aggrecan mRNA levels suggests that previously observed inhibitory effects of prolonged static compression on proteoglycan synthesis in articular cartilage may be, for the most part, mediated through mechanisms other than suppression of aggrecan mRNA levels.

Knee joint immobilization decreases aggrecan gene expression in the meniscus

Aggrecan is the major proteoglycan of the meniscus, and its primary function is to give the meniscus its viscoelastic compressive properties. The objective of this study was to determine the effect of joint immobilization on aggrecan gene expression in the meniscus. The right hindlimbs of six mature beagles were knee cast-immobilized in 90 degrees of flexion and supported by a sling to prevent weightbearing, while the contralateral limb was left free to bear weight. The animals were sacrificed at 4 weeks, and the anterior and posterior halves of the medial and lateral menisci were analyzed separately. Analysis of aggrecan gene expression by quantitative polymerase chain reaction showed decreased aggrecan gene expression in menisci from immobilized knees (P < 0.01, two-way analysis of variance). Aggrecan gene expression decreased by a factor of 2 to 5.5 in the different regions examined. Analysis of the composition of the meniscus also showed decreased proteoglycan content and increased water content with immobilization (P < 0.05, two-way analysis of variance). These results show that joint immobilization can significantly affect meniscal cellular activity and composition and can therefore potentially affect meniscal function.

Proteoglycans in the synovial fluid of the temporomandibular joint as an indicator of changes in cartilage metabolism during primary and secondary osteoarthritis

PURPOSE

The specific aim of this investigation was to assess differences between primary and secondary osteoarthritis (OA) of the temporomandibular joint (TMJ) using clinical evaluation and synovial fluid analysis for proteoglycans.

MATERIALS AND METHODS

Arthroscopic surgery was performed on 101 TMJs from patients with significant pain or dysfunction and who had failed to respond to treatment. Joints were assessed for primary and secondary osteoarthritis. Synovial fluid aspirates were obtained and analyzed to determine the levels of keratan sulfate (KS) epitope and a novel 3B3(-) epitope by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Fifty-four patients and 67 joints had OA diagnosed by both clinical examination and arthroscopy. Primary OA was diagnosed in 14 joints (20%), and the remaining 53 joints were regarded as having secondary OA. No differences were detected in the levels of KS in the synovial fluid from the primary and secondary OA joints. Furthermore, the 3B3(-) epitope was not detectable in the synovial fluid aspirates of any TMJ.

CONCLUSION

Secondary OA is a common disorder of the TMJ. However, there is no apparent difference in the metabolism of the joints with primary and secondary OA as assessed by proteoglycans in the synovial fluid. The apparent absence of the 3b3(-) epitope, in contrast to its presence in OA of other major synovial joints, suggests that there are some differences between the cartilage metabolism of the TMJ and these other joints during OA.

Dwarfism and age-associated spinal degeneration of heterozygote cmd mice defective in aggrecan

Mouse cartilage matrix deficiency (cmd) is an autosomal recessive disorder caused by a genetic defect of aggrecan, a large chondroitin sulfate proteoglycan in cartilage. The homozygotes (-/-) are characterized by cleft palate and short limbs, tail, and snout. They die just after birth because of respiratory failure, and the heterozygotes (+/-) appear normal at birth. Here we report that the heterozygotes show dwarfism and develop spinal misalignment with age. Within 19 months of age, they exhibit spastic gait caused by misalignment of the cervical spine and die because of starvation. Histological examination revealed a high incidence of herniation and degeneration of vertebral discs. Electron microscopy showed a degeneration of disc chondrocytes in the heterozygotes. These findings may facilitate the identification of mutations in humans predisposed to spinal degeneration.

Correlation between arthroscopic diagnosis of osteoarthritis and synovitis of the human temporomandibular joint and keratan sulfate levels in the synovial fluid

PURPOSE

The specific aims of this investigation were to determine if there is a relationship between an arthroscopic diagnosis of synovitis and osteoarthritis, and if the presence of synovitis influences the level of cartilage degradation, as evidenced by keratan sulfate levels in the synovial fluid.

PATIENTS AND METHODS

Arthroscopic surgery was performed on 114 temporomandibular joints in 88 patients who had significant pain or dysfunction and whose condition had failed to improve with conservative treatment. Synovial fluid aspirates were obtained immediately before arthroscopy and used for the determination of keratan sulfate levels. Arthroscopic examination included assessment of the presence or absence of osteoarthritis and synovitis.

RESULTS

Synovitis was present in 90% of joints, and osteoarthritis was present in 62% of joints examined arthroscopically. Both osteoarthritis and synovitis existed in 57% of the joints. Joints with an arthroscopic diagnosis of synovitis had significantly lower levels of keratan sulfate in the synovial fluid aspirates than joints with osteoarthritis. Synovial fluid aspirates from temporomandibular joints with osteoarthritis had significantly higher levels of keratan sulfate than synovial fluids from joints without osteoarthritis.

CONCLUSIONS

Osteoarthritis and synovitis are common diagnoses and are often present concurrently in patients with symptomatic temporomandibular joints. Osteoarthritis is associated with elevated keratan sulfate levels; however, the elevation of keratan sulfate is less in patients with concomitant synovitis.

Biochemical markers in synovial fluid identify early osteoarthritis of the glenohumeral joint

The objective of this study on the glenohumeral joint was to assess the (1) accuracy of clinical diagnosis of osteoarthritis compared with arthroscopic diagnosis, and (2) the ability of biochemical markers in synovial fluid to detect osteoarthritis. Patients (96) were examined clinically and the preoperative diagnosis of osteoarthritis was recorded. At surgery (arthroscopy or arthroplasty), the glenohumeral joint was inspected for signs of osteoarthritis, and the joint osteoarthritis grade (I-IV) was recorded. At surgery, synovial fluid lavage was obtained from the joint, and later analyzed to determine levels of aggrecan components: total sulfated glycosaminoglycan and keratan sulfate epitope, link protein and the chondroitin sulfate epitope recognized by antibody 3B3 (3B3(-)). Compared with arthroscopic diagnosis of osteoarthritis, the results showed that the clinical diagnosis did not wrongly identify joints without osteoarthritis, and was always able to identify joints with advanced (Grade IV) osteoarthritis. Grade II osteoarthritis was rarely identified (10% of the time), and Grade III osteoarthritis was identified 50% of the time. Biochemical assessment of the synovial fluid showed that the catabolic markers (sulfated glycosaminoglycan, keratan sulfate and link protein) were elevated in fluids from joints with moderate (Grade III) and advanced osteoarthritis (Grade IV), and the 3B3(-) epitope was elevated in Grades II, III, and IV. These results show that arthroscopic diagnosis for osteoarthritis, of the glenohumeral joint is particularly useful for early and moderate osteoarthritis, where clinical (nonarthroscopic) diagnosis is poor, and that biochemical analysis of the synovial fluids corresponds well to arthroscopic diagnosis of shoulder osteoarthritis.

Changes in proteoglycan synthesis of chondrocytes in articular cartilage are associated with the time-dependent changes in their mechanical environment

Explant loading experiments were conducted to investigate the effect of load duration on proteoglycan synthesis. A compressive load of 0.1 MPa applied for 10 min was found to stimulate proteoglycan synthesis, while the same load applied for 20 h suppressed synthesis. This bimodal response suggests that the cells are responding to different mechanical stimuli as time progresses. A theoretical model has therefore been developed to describe the mechanical environment perceived by cells within soft hydrated tissues (e.g. articular cartilage) while the tissue is being loaded. The cells are modeled, using the biphasic theory, as fluid-solid inclusions embedded in and attached to a biphasic extracellular matrix of distinct material properties. A method of solution is developed which is valid for any axisymmetric loading configuration, provided that the cell radius, a, is small relative to the tissue height, h (i.e. h/a >> 1). A closed-form analytical solution for this inclusion problem is then presented for the confined compression configuration. Results from this model show that the mechanical environment in and around the cells is time dependent and inhomogeneous, and can be significantly influenced by differences in properties between the cell and the extracellular matrix.

Centrifugal and biochemical comparison of proteoglycan aggregates from articular cartilage in experimental joint disuse and joint instability

Two models involving altered joint loading were compared with regard to their effects on the biochemical composition and proteoglycan aggregate structure of articular cartilage. Disuse atrophy was created in greyhound dogs by nonrigid immobilization of the right knee in 90 degrees of flexion, and joint instability was created by transection of the anterior cruciate ligament. Similarities and differences between the two experimental groups at two different time periods were examined to investigate why joint instability induces progressive and irreversible changes to the articular cartilage, whereas joint disuse induces changes that may be reversible when the joint is remobilized. The following studies were performed on the cartilage from all experimental and control groups: (a) compositional analyses to determine water, uronate, and hydroxyproline contents; (b) high performance liquid chromatography for detection of hyaluronan and chondroitin sulfates; and (c) centrifugation analyses of nondissociatively extracted and purified proteoglycans to isolate and quantify the populations of monomers and slow and fast-sedimenting families of aggregates. In general, all cartilage was found to have a decreased ratio of proteoglycan to collagen after 4 weeks of disuse, and this ratio returned to control values at 8 weeks. In contrast, cartilage had an elevated ratio of proteoglycan to collagen as well as increased hydration at 12 weeks after transection of the anterior cruciate ligament. The most striking contrast between the two models was the finding of an approximately 80% decrease in the content of hyaluronan at both time periods after transection of the anterior cruciate ligament, with no evidence of a change after disuse. The results of centrifugation analyses indicated a significant decrease in the quantity of proteoglycan aggregates in both models. However, this decrease was associated primarily with a loss of slow-sedimenting aggregates after disuse and a loss of both slow and fast-sedimenting aggregates after transection of the anterior cruciate ligament. Furthermore, the population of fast-sedimenting aggregates was depleted to a greater extent than that of the slow-sedimenting aggregates. The preservation of fast-sedimenting aggregates as well as hyaluronan after periods of joint disuse but not joint instability suggests a possible mechanism for the reversibility of cartilage changes. Although the proteoglycan aggregates were depleted after disuse atrophy, it is possible that an aggregate-depleted matrix could recover when normal proteoglycan synthesis is resumed. In contrast, although synthesis may be maintained or elevated after transection of the anterior cruciate ligament, the matrix may not be repopulated with aggregates because there is an insufficient amount of hyaluronan.

Mechanical properties of canine articular cartilage are significantly altered following transection of the anterior cruciate ligament

The compressive, tensile, and swelling properties of articular cartilage were studied at two time periods following transection of the anterior cruciate ligament in the knee of greyhound dogs. An experimental protocol was designed to quantify the essential equilibrium and biphasic material properties of cartilage in tension, compression, and shear, as well as the parameters of isometric swelling behavior. All properties were measured at several sites to elicit differences between sites of frequent and less frequent contact. Hydration was determined at each site and was compared with the material properties of cartilage from corresponding sites. There were extensive changes in all compressive, tensile, and swelling properties of cartilage after transection of the anterior cruciate ligament. Twelve weeks after surgery, the intrinsic moduli were reduced significantly in compression (approximately 24% of control values), tension (approximately 64%), and shear (approximately 24%), and the hydraulic permeability was elevated significantly (approximately 48%). Significant increases in hydration (approximately 9%) also were observed, as well as a strong correlation of hydration with hydraulic permeability. The pattern of these changes was not found to differ with site in the joint, but significant differences were observed in the magnitude of change for cartilage from the femoral groove and the femoral condyle. The pattern and extent of changes in the material properties following transection of the anterior cruciate ligament indicate that altered loading of the joint severely compromises the overall mechanical behavior of articular cartilage. The observed loss of matrix stiffness in compression, tension, and shear is associated with increases in the deformation of the solid matrix, a diminished ability to resist swelling, and the increase in hydration observed in this study. The increased swelling and elevated water content were related directly to the increase in hydraulic permeability; this suggests an associated loss of fluid pressurization as the load support mechanism in the degenerated cartilage. Without a successful mechanism for repair, damage to the solid matrix may progress and lead to further degenerative changes in the biochemistry, morphology, and mechanical behavior of articular cartilage.