Increased release of matrix components from articular cartilage in experimental canine osteoarthritis

Chondrotoxic effects of intra-articular injection of local anaesthetics in the rabbit temporomandibular joint

The aim of this study was to investigate the chondrotoxic effects of a single-dose intra-articular injection of articaine, lidocaine, and bupivacaine on the rabbit temporomandibular joint (TMJ). Twenty-four rabbits were divided into four groups: control (group 1), articaine (group 2), lidocaine (group 3), and bupivacaine (group 4). Synovial fluid samples and venous blood were taken to evaluate matrix metalloproteinase 3 (MMP-3) levels. One millilitre of local anaesthetic solution was injected in the study groups and saline solution in the control group. The rabbits were euthanized after 4 weeks and the mandibular condyles and articular discs were evaluated. On histological examination, the study group samples had irregular joint surfaces, decreased collagen, and a thinner cartilage layer. Apoptotic cells were evaluated with the TUNEL method. TUNEL-positive apoptotic cell counts were higher in all study groups compared to the control group, and the difference was significant (P < 0.001). The mean preoperative serum MMP-3 level for all groups was 5.71 ± 3.33 ng/mL, while the mean postoperative level was 22.61 ± 6.36 ng/mL; this difference was significant (P < 0.001). A single-dose intra-articular injection of local anaesthetic had apoptotic effects on chondrocytes, leading to degenerative changes in the TMJ articular structures. Articaine was found to have less harmful effects than lidocaine and bupivacaine. Intra-articular injection of local anaesthetics should be limited in the TMJ because of the potential toxic effects.

Biomechanics, obesity, and osteoarthritis. The role of adipokines: When the levee breaks

Osteoarthritis is a high-incidence painful and debilitating disease characterized by progressive degeneration of articular joints, which indicates a breakdown in joint homeostasis favoring catabolic processes. Biomechanical loading, associated with inflammatory and metabolic imbalances of joint, strongly contributes to the initiation and progression of the disease. Obesity is a primary risk factor for disease onset, and mechanical factors increased the risk for disease progression. Moreover, inflammatory mediators, in particular, adipose tissue-derived cytokines (better known as adipokines) play a critical role linking obesity and osteoarthritis. The present article summarizes the knowledge about the role of adipokines in cartilage and bone function, highlighting their contribution to the imbalance of joint homeostasis and, consequently, pathogenesis of osteoarthritis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:594-604, 2018.

Canine Adult Adipose Tissue-Derived Multipotent Stromal Cell Isolation and Characterization

Adult multipotent stromal cells (MSCs) are increasingly popular for direct therapeutic applications and bioengineering. Canine patients constitute a major component of veterinary practice, and the dog is an established preclinical animal model for numerous traumatic, degenerative, and disease conditions. Current information supports the presence and relative abundance of adipose tissue-derived multipotent stromal cells (ASCs) in various canine adipose tissue depots. Refined isolation and characterization techniques contribute to collective knowledge of ASC phenotypes and subpopulations for customized, targeted applications. Continued efforts to augment understanding of canine ASCs is critical to progressive treatment advances and high-impact study outcomes. This chapter contains a description of techniques to isolate and characterize canine ASCs.

Association between quantitative MRI and ICRS arthroscopic grading of articular cartilage

PURPOSE

To investigate the association of quantitative magnetic resonance imaging (qMRI) parameters with arthroscopic grading of cartilage degeneration. Arthroscopy of the knee is considered to be the gold standard of osteoarthritis diagnostics; however, it is operator-dependent and limited to the evaluation of the articular surface. qMRI provides information on the quality of articular cartilage and its changes even at early stages of a disease.

METHODS

qMRI techniques included T 1 relaxation time, T 2 relaxation time, and delayed gadolinium-enhanced MRI of cartilage mapping at 3 T in ten patients. Due to a lack of generally accepted semiquantitative scoring systems for evaluating severity of cartilage degeneration during arthroscopy, the International Cartilage Repair Society (ICRS) classification system was used to grade the severity of cartilage lesions. qMRI parameters were statistically compared to arthroscopic grading conducted with the ICRS classification system.

RESULTS

qMRI parameters were not linearly related to arthroscopic grading. Spearman's correlation coefficients between qMRI and arthroscopic grading were not significant. The relative differences in qMRI parameters of superficial and deep cartilage varied with degeneration, suggesting different macromolecular alterations in different cartilage zones.

CONCLUSIONS

Results suggest that loss of cartilage and the quality of remaining tissue in the lesion site may not be directly associated with each other. The severity of cartilage degeneration may not be revealed solely by diagnostic arthroscopy, and thus, qMRI can have a role in the investigation of cartilage degeneration.

Role of the Wnt/β-catenin signaling pathway in the response of chondrocytes to mechanical loading

In order to better understand the mechanisms by which chondrocytes respond to mechanical stimulation, ATDC5 mouse embryonic carcinoma cells were induced to differentiate into chondrocytes and then exposed to mechanical loading. To specifically elucidate the role of this pathway, the localization and expression of proteins involved in the Wnt/β-catenin signaling pathway were observed. Chondrogenic-differentiated ATDC5 cells were exposed to a 12% cycle tension load for 1, 2, 4, or 8 h. At each time point, immunofluorescence staining, western blot analysis, and qPCR were used to track the localization of β-catenin and glycogen synthase kinase-3β (GSK-3β) expression. In addition, the mRNA expression of Wnt3a, disheveled homolog 1 (Dvl-1), GSK-3β, and collagen type II were also detected. Activation of the Wnt/β-catenin signaling pathway was investigated in cells treated with Dickkopf-related protein 1 (DKK-1). β-catenin and GSK-3β protein expression increased initially and then decreased over the mechanical loading period, and the corresponding mRNA levels followed a similar trend. After application of the inhibitor DKK-1, Wnt/β‑catenin signaling was suppressed, and the mRNA expression of collagen II was also reduced. Thus, stimulation of chondrocytes with mechanical strain loading is associated with the translocation of active β-catenin from the cytoplasm to the nucleus.

Biomechanical factors in osteoarthritis

Biomechanical factors play an important role in the health of diarthrodial joints. Altered joint loading - associated to obesity, malalignment, trauma or joint instability - is a critical risk factor for joint degeneration, whereas exercise and weight loss have generally been shown to promote beneficial effects for osteoarthritic joints. The mechanisms by which mechanical stress alters the physiology or pathophysiology of articular cartilage or other joint tissues likely involve complex interactions with genetic and molecular influences, particularly local or systemic inflammation secondary to injury or obesity. Chondrocytes perceive physical signals from their environment using a variety of mechanisms, including ion channels, integrin-mediated connections to the extracellular matrix that involve membrane, cytoskeletal and intracellular deformation. An improved understanding of the biophysical and molecular pathways involved in chondrocyte mechanotransduction can provide insight into the development of novel therapeutic approaches for osteoarthritis.

Fiber-optic Raman spectroscopy of joint tissues

In this study, we report adaptation of Raman spectroscopy for arthroscopy of joint tissues using a custom-built fiber-optic probe. Differentiation of healthy and damaged tissue or examination of subsurface tissue, such as subchondral bone, is a challenge in arthroscopy because visual inspection may not provide sufficient contrast. Discrimination of healthy versus damaged tissue may be improved by incorporating point spectroscopy or hyperspectral imaging into arthroscopy where the contrast is based on the molecular structure or chemical composition. Articular joint surfaces of knee cadaveric human tissue and tissue phantoms were examined using a custom-designed Raman fiber-optic probe. Fiber-optic Raman spectra were compared against reference spectra of cartilage, subchondral bone and cancellous bone collected using Raman microspectroscopy. In fiber-optic Raman spectra of the articular surface, there was an effect of cartilage thickness on recovery of signal from subchondral bone. At sites with intact cartilage, the bone mineralization ratio decreased but there was a minimal effect in the bone mineral chemistry ratios. Tissue phantoms were prepared as experimental models of the osteochondral interface. Raman spectra of tissue phantoms suggested that optical scattering of cartilage has a large effect on the relative cartilage and bone signal. Finite element analysis modeling of light fluence in the osteochondral interface confirmed experimental findings in human cadaveric tissue and tissue phantoms. These first studies demonstrate the proof of principle for Raman arthroscopic measurement of joint tissues and provide a basis for future clinical or animal model studies.

In vitro expansion and differentiation of fresh and revitalized adult canine bone marrow-derived and adipose tissue-derived stromal cells

The objective of this study was to determine the tissue density, in vitro expansion and differentiation of canine adipose tissue-derived (ASC) and bone marrow-derived (BMSC) stromal cells. Primary (P0) and cell passages 1-6 (P1-6) cell doubling numbers (CD) and doubling times (DT) were determined in fresh cells. The P0, P3, and P6 adipogenic (CFU-Ad), osteogenic (CFU-Ob), and fibroblastic (CFU-F) colony forming unit frequencies, lineage specific mRNA levels in differentiated P3 cells and composition of P3 and P6 chondrogenic pellets were assessed in cryogenically preserved cells. Cell yields from bone marrow were significantly higher than adipose tissue. Overall ASC and BMSC CDs and DTs and P3 and P6 CFU-F, CFU-Ad, and CFU-Ob were comparable. The P0 BMSC CFU-Ob was significantly higher than ASC. Lineage specific mRNA levels were higher in differentiated versus control cells, but similar between cell types. Protein was significantly greater in P3 versus P6 ASC chondrogenic pellets. Based on these findings, fresh and revitalized canine ASCs are viable alternatives to BMSCs for stromal cell applications.

In vitro adult canine adipose tissue-derived stromal cell growth characteristics

Stromal cells are undifferentiated cells found in embryonic and adult tissues. Adult mesenchymal stromal cells (MSCs) possess the properties of self renewal, long-term viability, multipotentiality, and immune privilege, which make them attractive candidates for regenerative medicine applications. In order to develop targeted adult stromal cell therapies for diseased and injured tissues in animals and humans, it is essential to have large-animal models. The dog represents not only a patient population, but is also a valuable experimental model. The dog has contributed significantly to the understanding of various human diseases such as genetic and musculoskeletal disorders. In order to optimize the use of stromal cell therapy in the dog as a patient or disease model, a comprehensive characterization of the cells is required.

Changes in serum and synovial fluid biomarkers after acute injury (NCT00332254)

INTRODUCTION

Acute trauma involving the anterior cruciate ligament is believed to be a major risk factor for the development of post-traumatic osteoarthritis 10 to 20 years post-injury. In this study, to better understand the early biological changes which occur after acute injury, we investigated synovial fluid and serum biomarkers.

METHODS

We collected serum from 11 patients without pre-existing osteoarthritis from a pilot intervention trial (5 placebo and 6 drug treated) using an intra-articular interleukin-1 receptor antagonist (IL-1Ra) therapy, 9 of which also supplied matched synovial fluid samples at presentation to the clinic after acute knee injury (mean 15.2 ± 7.2 days) and at the follow-up visit for reconstructive surgery (mean 47.6 ± 12.4 days). To exclude patients with pre-existing osteoarthritis (OA), the study was limited to individuals younger than 40 years of age (mean 23 ± 3.5) with no prior history of joint symptoms or trauma. We profiled a total of 21 biomarkers; 20 biomarkers in synovial fluid and 13 in serum with 12 biomarkers measured in both fluids. Biomarkers analyzed in this study were found to be independent of treatment (P > 0.05) as measured by Mann-Whitney and two-way ANOVA.

RESULTS

We observed significant decreases in synovial fluid (sf) biomarker concentrations from baseline to follow-up for (sf)C-Reactive protein (CRP) (P = 0.039), (sf)lubricin (P = 0.008) and the proteoglycan biomarkers: (sf)Glycosaminoglycan (GAG) (P = 0.019), and (sf)Alanine-Arginine-Glycine-Serine (ARGS) aggrecan (P = 0.004). In contrast, we observed significant increases in the collagen biomarkers: (sf)C-terminal crosslinked telopeptide type II collagen (CTxII) (P = 0.012), (sf)C1,2C (P = 0.039), (sf)C-terminal crosslinked telopeptide type I collagen (CTxI) (P = 0.004), and (sf)N-terminal telopeptides of type I collagen (NTx) (P = 0.008). The concentrations of seven biomarkers were significantly higher in synovial fluid than serum suggesting release from the signal knee: IL-1β (P < 0.0001), fetal aggrecan FA846 (P = 0.0001), CTxI (P = 0.0002), NTx (P = 0.012), osteocalcin (P = 0.012), Cartilage oligomeric matrix protein (COMP) (P = 0.0001) and matrix metalloproteinase (MMP)-3 (P = 0.0001). For these seven biomarkers we found significant correlations between the serum and synovial fluid concentrations for only CTxI (P = 0.0002), NTx (P < 0.0001), osteocalcin (P = 0.0002) and MMP-3 (P = 0.038).

CONCLUSIONS

These data strongly suggest that the biology after acute injury reflects that seen in cartilage explant models stimulated with pro-inflammatory cytokines, which are characterized by an initial wave of proteoglycan loss followed by subsequent collagen loss. As the rise of collagen biomarkers in synovial fluid occurs within the first month after injury, and as collagen loss is thought to be irreversible, very early treatment with agents to either reduce inflammation and/or reduce collagen loss may have the potential to reduce the onset of future post-traumatic osteoarthritis.

TRIAL REGISTRATION

The samples used in this study were derived from a clinical trial NCT00332254 registered with ClinicalTrial.gov.

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.

Products resulting from cleavage of the interglobular domain of aggrecan in samples of synovial fluid collected from dogs with early- and late-stage osteoarthritis

OBJECTIVE

To investigate interglobular domain (IGD) cleavage of aggrecan in dogs with naturally developing osteoarthritis (OA).

SAMPLE POPULATION

Samples of synovial fluid (SF) obtained from 3 cubital (elbow) joints and 3 stifle joints of 4 clinically normal dogs, 24 elbow joints of 12 dogs with early-stage OA, 8 stifle joints of 5 dogs with early-stage OA, and 10 stifle joints of 9 dogs with late-stage OA.

PROCEDURE

Fractions of SF were assayed for total glycosaminoglycan (GAG) content and also subjected to Western blot analysis by use of monoclonal antibodies against neoepitopes generated by cleavage of the IGD of the aggrecan protein core by matrix metalloproteinase (MMP; BC-14) and aggrecanase (BC-3).

RESULTS

Total GAG content of SF from joints of clinically normal dogs did not differ from that of dogs with early-stage OA. The GAG content of SF from joints of dogs with late-stage OA was significantly lower, compared with GAG content for other SF samples. Aggrecanase-generated fragments were detected in SF from all groups but not in all samples. Matrix metalloproteinase-generated fragments were not detected in any SF samples. In early-stage OA, high-molecular-weight aggrecanase-generated aggrecan catabolites were evident.

CONCLUSIONS AND CLINICAL RELEVANCE

GAG content of SF obtained from dogs with late-stage OA is significantly decreased, suggesting proteoglycan depletion of cartilage. Aggrecanases, but not MMPs, are the major proteolytic enzymes responsible for IGD cleavage of aggrecan in canine joints. Analyses of SF samples to detect aggrecanase-generated catabolites may provide an early biomarker for discriminating early- and late-stage OA in dogs.

Effects of helium-neon laser on the mucopolysaccharide induction in experimental osteoarthritic cartilage

OBJECTIVE

To investigate the effects of mucopolysaccharide induction after treatment by low power laser for experimental osteoarthritis (OA).

METHODS

Seventy-two rats with three different degrees of papain induced OA over right knee joints were collected for helium-neon (He-Ne) laser treatment. The severity of induced arthritis was measured by 99mTc bone scan and classified into three groups (I-III) by their radioactivity ratios (right to left knee joints). The rats in each group were further divided into study subgroups (Is, IIs, and IIIs) and control subgroups (Ic, IIc, and IIIc) randomly. The arthritic knees in study subgroups received He-Ne laser treatment, and those in controls received sham laser treatment. The changes of arthritic severity after treatment and follow-up 2 months later were measured. The histopathological changes were evaluated through light microscope after disarticulation of sections (H.E. stain), and the changes of mucopolysaccharide density in cartilage matrix were measured by Optimas scanner analyzer after Alcian blue (AB) stain. The densities of mucopolysaccharide induced after treatment in arthritic cartilage were compared and correlated with their histopathological changes.

RESULTS

The density of mucopolysaccharide rose at the initial stage of induced arthritis, and decreased progressively in later stages. The densities of mucopolysaccharide in treated rats increased upon complete laser treatment more than those of the controls, which is closely related with the improvement in histopathological findings, but conversely with the changes in arthritic severity.

CONCLUSION

He-Ne laser treatment will enhance the biosynthesis of arthritic cartilage, and results in the improvement of arthritic histopathological changes.

Proteoglycan fragments in anterior cruciate ligament reconstructed knees: a comparative study of two different surgical techniques

Proteoglycan fragments (PF) as chondroitin sulphate were monitored and compared in two groups of patients who had anterior cruciate ligament reconstruction with either patellar tendon (PT) or quadruple semitendinosus tendon (ST) autografts. There were 20 ST and 21 PT reconstructions. No difference existed between the groups in terms of associated lesion and time from injury to surgery. Synovial sample was collected at 6 weeks, 3 months and 18 months after the operation. No difference was noted between the groups at 18 months in terms of activity level and functional scores. Both groups demonstrated a sudden increase of PF at 6 weeks with respect to preoperative quantities (p<0.0001). A significant decrease occurred in the PT group at 3 months (p<0.008). Even at 18 months, it was significantly below the preoperative values (p<0.004). However, the decrease in ST cases relative to 6 weeks was insignificant at 3 months and quantities did not drop below the preoperative levels at 18 month (p=0.79). These results confirm again a gradual decrease of PF values in PT-reconstructed knees depending on time and surgery. Reconstruction with quadruple ST does not seem to have the same effect until 18 months postoperatively. Achievement of almost the same level of activity and function in both groups does not necessarily reflect the molecular status.

The role of biomechanics and inflammation in cartilage injury and repair

Osteoarthritis is a painful and debilitating disease characterized by progressive degenerative changes in the articular cartilage and other joint tissues. Biomechanical factors play a critical role in the initiation and progression of this disease, as evidenced by clinical and animal studies of alterations in the mechanical environment of the joint caused by trauma, joint instability, disuse, or obesity. The onset of these changes after joint injury generally has been termed posttraumatic arthritis and can be accelerated by factors such as a displaced articular fracture. Within this context, there is considerable evidence that interactions between biomechanical factors and proinflammatory mediators are involved in the progression of cartilage degeneration in posttraumatic arthritis. In vivo studies have shown increased concentrations of inflammatory cytokines and mediators in the joint in mechanically induced models of osteoarthritis. In vitro explant studies confirm that mechanical load is a potent regulator of matrix metabolism, cell viability, and the production of proinflammatory mediators such as nitric oxide and prostaglandin E2. Knowledge of the interaction of inflammatory and biomechanical factors in regulating cartilage metabolism would be beneficial to an understanding of the etiopathogenesis of posttraumatic osteoarthritis and in the improvement of therapies for joint injury.

An in situ calibration of an ultrasound transducer: a potential application for an ultrasonic indentation test of articular cartilage

A change in mechanical properties of articular cartilage would be considered one of the most reliable signs of cartilage degeneration. While an indentation method has the potential to measure the cartilage properties in vivo, an accurate measurement of cartilage thickness in situ is technically difficult. An ultrasound transducer has often been used to measure the cartilage thickness. However, its accuracy is limited by the lack of an accurate measurement of the ultrasound speed of cartilage, for the ultrasound speed varies according to the pathological conditions of the tissue. Therefore, the objective of this study is to develop an in situ calibration method of predicting the true ultrasound speed of cartilage and thus allow the ultrasound transducer to measure the thickness of the tissue with great accuracy. By simultaneously implementing an indentation testing protocol using the ultrasound transducer as an indenter, this method can also provide an indentation stiffness measurement of cartilage. The feasibility of the proposed method was examined using normal and proteoglycan-depleted cartilage specimens. It was found that the true ultrasound speed measured by the in situ calibration method was sensitive to the proteoglycan depletion (1735+/-35 m/s for normal, and 1598+/-28 m/s for proteoglycan-depleted cartilage), and that the measured cartilage thickness was consistently accurate regardless of the tissue condition. The measured indentation stiffness of articular cartilage was also sensitive to the tissue condition. Thus, this study demonstrates that the proposed ultrasonic indentation technique can be used to accurately identify the abnormality of articular cartilage in situ.

Synovial fluid markers of osteoarthritis in dogs

Although none of these markers currently have any clinical applications, researchers have made strong advances in understanding molecular markers of OA and remain optimistic that the goal of identifying clinically useful markers of OA is attainable.(3-6,8,9) Much of this positive sentiment arises from the large array of molecules that have been identified.(8) Molecular markers of the greatest potential clinical use will be those that allow early detection of OA, permit disease progression to be monitored, or allow efficacy of various treatment regimens to be assessed. Earlier and more sensitive detection of OA changes may increase effective opportunities for treatment intervention during reversible phases of the OA disease process and allow more objective assessment of treatment efficacy and prognosis.(6)

Effect of load on articular cartilage matrix and the development of guinea-pig osteoarthritis

OBJECTIVE

To study the biochemical changes in the early development of primary guinea-pig knee osteoarthritis (OA) and its dependence on load.

METHODS

Load distribution was modified with below-knee amputation or femur valgus osteotomy in 9-month-old guinea-pigs. Soft tissue sham operated animals served as controls. The composition of uncalcified and calcified articular cartilage at the medial and lateral tibial condyle was studied by analysing small and large proteoglycans (PG) by gel electrophoresis and sulfation pattern with high-performance liquid chromatography. Collagen concentration was also determined.

RESULTS

The articular surfaces with a presumed higher load after surgery had a slight, but consistent, higher water content. Decreased load-on the ipsilateral medial condyle after femur osteotomy, and on the ipsilateral medial and lateral condyles following tibia amputation-was associated with an increased concentration of PGs, while this concentration decreased in condyles with increased load. Collagen concentration followed a similar pattern in the osteotomy group. In the amputated animals collagen concentration went down in all condyles, regardless of change of load. The aggregability and proportion of large and small PGs, the concentration of hyaluronan and the sulfation pattern of chondroitin sulfate was not affected by load. No consistent changes in PG, collagen or HA concentration, HA aggregability or sulfation pattern were seen in the calcified cartilage.

CONCLUSIONS

Primary guinea-pig knee OA is a reproducible model similar to human OA. It develops slowly and biochemical changes seem to appear before the morphological lesions become evident. The biochemical events are affected by load redistribution and correlate closely to morphological changes. These changes eventually result in a cartilage devoid in aggrecan, as also has been demonstrated in advanced human OA. All of this makes primary guinea-pig OA a suitable model for studying early OA changes.

Serum and synovial fluid levels of chondroitin sulfate in patients with osteoarthritis of the knee joint

We measured serum and synovial fluid levels of chondroitin sulfate (CS) in patients with osteoarthritis (OA) of the knee joint to clarify whether CS levels differ in various stages of OA, and whether measurement of CS levels is useful in evaluating the pathology of OA. The study population was 117 OA patients and 23 healthy young volunteers. Synovial fluid was obtained from 69 of 117 OA patients. The mean serum level of C4S in all of the OA patients was significantly higher than that in the controls (p< 0.05). However, there was little difference between respective OA stages. A small amount of serum C6S (0.2 to 0.6 nmol/ml) was detected in 31.6% of the OA patients and in 26.1%of the control subjects. The mean serum C0S level in all OA patients was significantly higher than that in the controls (p< 0.01). However no significant difference was found between respective OA stages. As for synovial fluid CS, the C4S level in the early stage of OA tended to be higher than that in the advanced stage. C6S levels showed a markedly decreasing trend with advancing OA stage. C0S was not detected in synovial fluid. The present study demonstrated that serum levels of C4S and C0S in OA patients are elevated compared with normal subjects, and that synovial fluid levels of C4S and C6S may provide useful in assessing the pathology of OA.

Concentrations of chondroitin sulfate epitopes 3B3 and 7D4 in synovial fluid after intra-articular and extracapsular reconstruction of the cranial cruciate ligament in dogs

OBJECTIVE

To evaluate effects of intra-articular and extracapsular reconstruction of the cranial cruciate ligament (CCL) on metabolism of articular cartilage as reflected by concentrations of chondroitin sulfate epitopes 3B3 and 7D4 in synovial fluid.

ANIMALS

13 adult dogs.

PROCEDURE

Each dog underwent unilateral CCL transection (CCLT). One month after CCLT, sham CCL reconstruction (3 dogs), intra-articular CCL reconstruction (5), or extracapsular CCL reconstruction (5) was performed. Synovial fluid was collected by direct arthrocentesis from CCLT and contralateral stifle joints immediately before (time 0) and 1, 3, and 5 months after CCLT. Fluid was examined for concentrations of 3B3 and 7D4 epitopes and total sulfated glycosaminoglycan (GAG) content.

RESULTS

Concentrations of 3B3, 7D4, and GAG, 3B3:GAG, or 7D4:GAG in CCLT joints did not differ significantly among treatment groups nor in the ratios of these variables in CCLT joints to contralateral joints at 3 months. In a longitudinal analysis, concentrations of 3B3 and 7D4, 3B3:GAG, and 7D4:GAG in CCLT joints in all groups changed significantly with time, but we did not detect time X group interactions.

CONCLUSIONS AND CLINICAL RELEVANCE

Transection of CCL resulted in significant perturbation in articular cartilage metabolism as reflected by alterations in concentrations of 3B3 and 7D4 in synovial fluid. These changes over time were not significantly influenced by method of CCL reconstruction. We did not find evidence that surgical stabilization of CCL-deficient joints by intra-articular or extracapsular techniques had any effect on preventing alterations in composition of synovial fluid that have been associated with secondary osteoarthritis.

Effects of an orally administered mixture of chondroitin sulfate, glucosamine hydrochloride and manganese ascorbate on synovial fluid chondroitin sulfate 3B3 and 7D4 epitope in a canine cruciate ligament transection model of osteoarthritis

OBJECTIVE

To evaluate effects of an orally administered mixture of chondroitin sulfate, glucosamine hydrochloride and manganese ascorbate (CS-G-M) on articular cartilage metabolism in dogs with cranial cruciate ligament (CCL) deficient and reconstructed knees, as reflected by concentrations of synovial fluid 3B3, 7D4 and total sulfated glycosaminoglycan (GAG).

METHODS

Sixteen adult dogs that underwent unilateral CCL transection were randomized into four groups. Thereafter, group I (N=3) had a sham CCL reconstruction, group II (N=3) had CS-G-M and sham CCL reconstruction, group III (N=5) had CCL reconstruction, and group IV (N=5) had CS-G-M and CCL reconstruction. Synovial fluid collected at 0, 1, 3 and 5 months was examined by ELISA for 3B3 and 7D4 epitope, and by DMMB assay for total GAG.

RESULTS

Synovial fluid from CCL transected knees of CS-G-M treated dogs contained significantly elevated concentrations of 3B3 (P=0.029), 7D4 (P=0.036) and 7D4/GAG (P=0.007) in comparison to controls, in a cross-sectional analysis at 3 months. Furthermore, 7D4 and 7D4/GAG concentrations remained significantly elevated (P=0.012) in CCL transected knees of CS-G-M treated dogs over the 5 month period. However, when epitope concentrations were expressed as a ratio of CCL-transected to contralateral non-operated knee, treatment effect of CS-G-M was no longer significant. Reconstruction of the CCL had no significant effect on synovial fluid epitope.

CONCLUSIONS

Administration of CS-G-M was associated with altered concentrations of 3B3 and 7D4 epitope in synovial fluid, suggesting that these compounds may act to modulate articular cartilage matrix metabolism in vivo.

Mitogen-activated protein kinase signaling in bovine articular chondrocytes in response to fluid flow does not require calcium mobilization

In the present study, the role of mitogen-activated protein kinases (MAPKs) in chondrocyte mechanotransduction was investigated. We hypothesized that MAPKs participate in fluid flow-induced chondrocyte mechanotransduction. To test our hypothesis, we studied cultured chondrocytes subjected to a well-defined mechanical stimulus generated with a laminar flow chamber. The extracellular signal-regulated kinases 1 and 2 (ERK1/2) were activated 1.6-3-fold after 5-15 min of fluid flow exposure corresponding to a chamber wall shear stress of 1.6 Pa. Activation of ERK1/2 was observed in the presence of both 10% FBS and 0.1% BSA, suggesting that the flow effects do not require serum agonists. Treatment with thapsigargin or EGTA had no significant effect on the ERK1/2 activation response to flow, suggesting that Ca2+ mobilization is not required for this response. To assess downstream effects of the activated MAPKs on transcription, flow studies were performed using chondrocytes transfected with a chimeric luciferase construct containing 2.4 kb of the promoter region along with exon 1 of the human aggrecan gene. Two-hour exposure of transfected chondrocytes to fluid flow significantly decreased aggrecan promoter activity by 40%. This response was blocked by treatment of chondrocytes with the MEK-1 inhibitor PD98059. These findings demonstrate that, under the conditions of the present study, fluid flow-induced signals activate the MEK-1/ERK signaling pathway in articular chondrocytes, leading to down-regulation of expression of the aggrecan gene.

Synovial fluid markers in osteoarthritis

Exploration of the mechanisms responsible for breakdown and repair of articular cartilage in osteoarthritis has promoted interest in the potential use of cartilage-derived molecules as markers of cartilage metabolism in this disease. Many of the macromolecules detectable in synovial fluid have been evaluated as possible surrogate markers of the severity or activity of disease processes. Measurements of the synovial fluid concentration of any marker without due consideration of the fate of the molecule in the joint cavity are likely to be misleading and insufficient to cement a relationship between marker concentration and the severity of articular pathology.

Immune responses to cartilage link protein and the G1 domain of proteoglycan aggrecan in patients with osteoarthritis

OBJECTIVE

To determine whether patients with osteoarthritis (OA) express cellular immunity to cartilage link protein (LP) and the G1 globular domain of proteoglycan (PG) aggrecan, and whether immunity to the G1 domain is influenced by the removal of keratan sulfate (KS).

METHODS

LP and the G1 globular domain of PG were isolated from human and/or bovine cartilage and used in proliferation assays with peripheral blood lymphocytes (PBL) from 42 patients with OA and 40 healthy control subjects.

RESULTS

Patients with OA expressed a higher prevalence of cellular immunity to human cartilage LP (42.4%) compared with the control group (13.3%). The prevalence of immune reactivity to bovine LP in patients with OA was lower (35.7%) compared with the immunity to human LP, but remained similar in the control group (13.8%). PBL from patients with OA exhibited low reactivity to the native G1 domain of bovine PG. However, removal of KS chains from the G1 globular domain resulted in increased cellular immune responses to the G1 domain in OA patients (45.8%) compared with the control group (7.7%).

CONCLUSION

These results indicate the presence of immunity to cartilage-derived LP and the G1 globular domain of PG aggrecan in patients with OA and the inhibitory effect of KS chains on the G1 domain on the expression of this immunity in OA patients. This immune reactivity is commonly observed in patients with inflammatory joint disease and can experimentally induce arthritis. Thus, it may be involved in the pathogenesis of OA.

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.

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.

Changes in messenger RNA and protein levels of proteoglycans and link protein in human osteoarthritic cartilage samples

OBJECTIVE

To determine the steady-state messenger RNA (mRNA) levels and corresponding protein contents of major matrix components in osteoarthritic (OA) cartilage.

METHODS

Steady-state levels of gene-specific mRNA (relative to GAPDH) were measured by quantitative polymerase chain reaction (PCR), and the relative levels of the corresponding proteins were determined by Western blotting.

RESULTS

All mRNA levels and corresponding protein contents of aggrecan and versican (hyaluronan-binding large proteoglycans), decorin, biglycan, fibromodulin, and lumican (small proteoglycans), and link protein were higher in OA cartilage samples than in age-matched normal samples. The ratio of increase, however, was different for each component. The mRNA and protein levels of biglycan, decorin, and fibromodulin increased synchronously, whereas message for link protein and lumican were several-fold higher than expected by their measured protein contents. Versican was also detected in OA cartilage; however, the versican protein content was associated with a relatively low mRNA level.

CONCLUSION

The expression of matrix components was increased in chondrocytes of OA cartilage, especially the expression of small proteoglycans, most likely due to the repair processes. A discoordinate gene expression accompanied with imbalanced accumulation of noncollagenous matrix components may contribute to the disorganization of the cartilage and the development of OA processes.

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.

Histochemical and immunohistochemical studies of the effects of experimental anterior disc displacement on sulfated glycosaminoglycans, hyaluronic acid, and link protein of the rabbit craniomandibular joint

PURPOSE

The purpose of this study was to determine the effects of surgically induced anterior disc displacement (ADD) on sulfated glycosaminoglycans (GAGs) such as keratan sulfate (KS), chondroitin-4-sulfate (C4S), and chondroitin-6-sulfate (C6S), hyaluronic acid (HA), and link protein (LP) of the rabbit craniomandibular joint (CMJ) using histochemical and immunohistochemical techniques.

MATERIALS AND METHODS

The right joint of 20 rabbits was exposed surgically, and all discal attachments were severed except for the posterior attachment. The disc was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as nonoperated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) after surgery. Discs, bilaminar zones, condyles, and articular eminences were excised. Condyles and articular eminences were decalcified in ethylenediaminetetraacetic acid (EDTA). All tissues were sectioned at 10 microns in a cryostat. Sections were incubated with alcian blue and monoclonal antibodies directed against KS, C4S, C6S, HA, or LP. After incubation in the appropriate fluorescein isothiocyanate (FITC)-labeled secondary antibodies, tissue sections were studied under the fluorescence microscope.

RESULTS

The results showed a reduction in alcian blue staining and KS, C4S, C6S, HA, and LP immunostaining in the disc and articular surfaces at 2 weeks after induction of ADD. This reduction was followed by an increase in their immunostaining at 6 weeks. Also, there was a progressive increase in alcian blue staining, and KS, C4S, C6S, and HA immunostaining in the bilaminar zone at 2 and 6 weeks.

CONCLUSION

It was concluded that surgical induction of ADD in the rabbit CMJ leads to alterations in KS, C4S, C6S, HA, and LP content, consistent with similar changes accompanying osteoarthritis of other synovial joints.

Intra-articular morphine and saline injections induce release of large molecular weight proteoglycans into equine synovial fluid

Both morphine and physiologic saline injected intra-articularly into healthy equine tarsocrural joints induced a release of large molecular size proteoglycan (PG) subunits into the synovial fluid (SF) analysed 24 h postinjection. High-performance liquid chromatography (HPLC) with a size-exclusion column was used to assess the high molecular weight proteoglycans in equine synovial fluid (SF). The PG peaks of SF samples eluated separately from SF hyaluronate and other molecular components of the SF in the HPLC chromatographies indicating no interaction between hyaluronate and PG in the SF. Individual elution profiles varied between joints and horses. The amount of PG release was measured by relative area index from the HPLC chromatograms. The synovial fluid PG content was significantly increased (P < 0.05) after morphine but not in saline injected joints compared with pretreatment but there were no significant differences between the two groups. It was concluded that intra-articular injections of both morphine and physiologic saline are able to elicit a marked PG release into the SF from articular cartilage within 24 h of injection.

Tumor necrosis factor-alpha (TNF-alpha) in canine osteoarthritis: Immunolocalization of TNF-alpha, stromelysin and TNF receptors in canine osteoarthritic cartilage

The presence and distribution of tumor necrosis factor-alpha (TNF-alpha), TNF receptors and stromelysin [matrix metalloproteinase 3 (MMP-3)] in articular cartilage were evaluated in an iatrogenically induced model of osteoarthritis (OA). Eleven adult male dogs were assigned randomly to a control group (N = 4) or an OA group (N = 7). Osteoarthritis was created by surgical transection of the cranial cruciate ligament of one stifle joint. Both femoral condyles were sampled 3 months post-surgery at necropsy and immunohistochemically analyzed for the presence of the aforementioned cytokines and receptors. Chondrocytes stained for TNF-alpha and TNF receptors in control articular cartilage, spanning an area encompassing most of the middle and deep zones. Positive matrical and chondrocytic staining for TNF-alpha, TNF receptors, and stromelysin was present in OA articular cartilage. Staining varied in intensity and distribution and was dependent of the severity of the lesion. Smooth muscle cells of arteries and arterioles (periarticular synovial membrane) were stained for only one (p55) of two TNF receptors; this staining was confined to control tissues. Results indicate that the differential expression of TNF-alpha and its receptors may be important in the normal maintenance of articular cartilage. The increased presence of TNF-alpha and its receptors in articular cartilage with mild osteoarthritic changes suggests a role in the development of early OA. Regulating TNF-alpha may be an important component in the treatment of OA.

Even low-grade synovitis significantly accelerates the clearance of protein from the canine knee. Implications for measurement of synovial fluid "markers" of osteoarthritis

OBJECTIVE

In recent studies, the synovial fluid concentration of molecules derived from the extracellular matrix of articular cartilage has been used to deduce the magnitude of cartilage destruction or repair in osteoarthritic (OA) joints. Because low-grade synovitis is often present in such joints, we assessed the effect of synovial inflammation on the clearance of a prototypical protein, albumin, from synovial fluid.

METHODS

131I-labeled albumin (RISA) was injected into 1 (control) knee of each of 14 dogs. The concentration of RISA in synovial fluid aspirated 7 hours after the injection and serial measurements of surface radioactivity were used to calculate the volume of distribution (Vd) and clearance of RISA. One week later, synovitis was induced in the contralateral knee by intraarticular injection of various quantities of calcium pyrophosphate dihydrate (CPPD) crystals, after which RISA was injected into that joint and these measurements were repeated.

RESULTS

Intraarticular injection of 500 micrograms of CPPD crystals produced intense synovitis, with a mean synovial fluid white blood cell (WBC) count of 43,200 cells/mm3, and values for RISA Vd and RISA clearance (36.5 ml and 33.7 microliters/minute) were much higher than those for saline-injected control knees (2.7 ml and 1.5 microliters/minute, respectively). Injection of 0.5 microgram of CPPD also produced marked synovitis and values for Vd and RISA clearance that were 2-3-fold greater than those in the contralateral knee. The low-grade synovitis produced by only 0.05 microgram of CPPD, which resulted in synovial fluid WBC counts as low as 1,000-2,000 cells/mm3, was accompanied by increases in the clearance and Vd of RISA to levels approximately 40% and approximately 80% higher, respectively, than those for the contralateral knee.

CONCLUSION

Even mild synovitis, as seen in OA, may significantly increase the clearance of a protein from the joint. Synovitis is a significant variable which must be considered in studies of putative chondroprotective drugs if conclusions about the effects of drugs on cartilage metabolism are to be drawn from changes in the synovial fluid concentration of a "marker" protein.

An immunohistochemical study of the effects of surgical induction of anterior disc displacement in the rabbit craniomandibular joint on type I and type II collagens

The right craniomandibular joint (CMJ) was exposed surgically and all the discal attachments severed except for the posterior one. The disc was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control; 10 other joints were used as non-operated controls. Deeply anaesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) after the induction of the anterior disc displacement (ADD). The articular disc, bilaminar zone, mandibular condyle and articular eminence were excised. The condyles and the articular eminences were demineralized in EDTA. All tissues were then sectioned at 10 microns in a cryostat. Sections were incubated with polyclonal antibodies directed against type I or type II collagens. Following incubation in the appropriate fluorescein isothiocyanate-labelled secondary antibodies, these specimens were studied under the fluorescence microscope. At 2 weeks there was a reduction in type II collagen immunostaining; some areas of the experimental condylar cartilage showed a switch from type II to type I collagen. However, at 6 weeks there was an increase in type II collagen immunostaining and a decrease in type I compared to the 2-week group. It is concluded that surgical induction of ADD in the rabbit CMJ leads to alteration in the condylar cartilage collagen phenotype similar to that reported for osteoarthritic cartilage of other synovial joints.

Large and small proteoglycans of osteoarthritic and rheumatoid articular cartilage

OBJECTIVE

To identify characteristic changes in large aggregating (aggrecan) and small proteoglycan (PG) populations in articular cartilages during osteoarthritis (OA) and rheumatoid arthritis (RA).

METHODS

Aggrecan populations in guanidine extracts of femoral condylar cartilages of 46 OA and 8 RA patients who underwent total knee arthroplasty, as well as of 2 fetuses and 6 normal adults, were separated in agarose-polyacrylamide composite gels. Small PGs (biglycan, decorin, and fibromodulin) in the same extracts were analyzed in 12% polyacrylamide gels. Gels were stained or electrophoretically transferred and probed with antibodies to aggrecan epitopes and to small PGs. Epitope contents of the samples were also compared by inhibition radioimmunoassay.

RESULTS

There were significant differences found among normal and diseased samples in their electrophoretic mobilities, band distributions, and antibody staining. OA and especially RA samples were heavily degraded, lacked certain aggrecan populations, and contained fewer keratan sulfate and chondroitin-6-sulfate epitopes compared with normal samples. Levels of chondroitin-4-sulfate and "fetal-type" epitopes were elevated in the OA samples compared with the normal ones. More core proteins of small PGs were found in diseased than in normal cartilages, but they were more heterogeneous in size and glycosaminoglycan substitution.

CONCLUSION

There is extensive degradation of both large and small PGs in diseased cartilages, but a repair process does exist, especially in OA cartilages. Chondrocytes of diseased cartilages are able to synthesize fetal-type aggrecans. Small PGs are glycosylated differently in diseased cartilages than in normal ones.

Increased proteoglycan synthesis in cartilage in experimental canine osteoarthritis does not reflect a permanent change in chondrocyte phenotype

OBJECTIVE

To determine whether chondrocytes in early experimental osteoarthritic (OA) cartilage continue to show increased synthesis and turnover of proteoglycans (PGs) during explant culture. A comparison was also made between the responsiveness of experimental OA and control cartilage to interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha) after 1 day and 3 days in culture.

METHODS

OA was induced in mature animals by sectioning of the anterior cruciate ligament followed by 3 months of normal exercise. PG synthesis in the articular cartilage was determined by measuring 35S-sulfate incorporation during explant culture over 1-3 days. Inhibition of PG synthesis was also determined with various concentrations of IL-1 beta and TNF alpha after 1 and 3 days in culture. PGs extracted from the articular cartilage over 1-3 days in culture were examined by agarose-polyacrylamide gel electrophoresis.

RESULTS

Up to 24 hours after excision from the joint, PG synthesis was higher in experimental OA cartilage than in control cartilage. It was also less sensitive to inhibition by TNF alpha. These differences were no longer detected after 48-72 hours in culture. There were no changes in the relative proportions of aggrecan and decorin/biglycan extracted from and synthesized by control and experimental OA cartilage over the 3 days in culture.

CONCLUSION

Previous results indicated that PG synthesis and turnover in articular cartilage was increased for many months after induction of experimental OA. Our present results show that the enhanced rate of PG synthesis and turnover were evident in freshly explanted tissue, but the differences were lost over 3 days in culture. A decreased responsiveness to TNF alpha was also lost. The hypermetabolic activity of experimental OA chondrocytes was thus reversible and not a permanent change in chondrocyte phenotype.

Mechanical and biochemical changes in the superficial zone of articular cartilage in canine experimental osteoarthritis

The changes in the tensile mechanical properties and biochemical composition of the superficial zone of articular cartilage were examined in a canine model of early osteoarthritis generated by transection of the anterior cruciate ligament. Sixteen weeks following ligament transection, the tensile stiffness of the articular cartilage was decreased by 44% and the ion-induced stress relaxation of the tissue was increased by 57% compared with the contralateral control. Biochemical analyses indicated that the water content of the experimental tissue was increased by 13%, which was reflected as an apparent 37% decrease in the proteoglycan content and a 36% decrease in the collagen content (expressed per wet weight). The hydroxypyridinium crosslink density was decreased in the experimental tissue by 11%. A significant negative correlation was found between the ion-induced stress relaxation and the hydroxypyridinium crosslink density in both control tissue (R = -0.56) and experimental tissue (R = -0.70). No correlation was noted between the tensile stiffness and the biochemical composition of the tissue. These results suggest that, in the superficial zone of articular cartilage, the structure of the tissue may play a more important role than the composition in the determination of its mechanical properties. A major event observed in the model of early osteoarthritis appears to be the disruption and remodeling of the collagen network in the superficial zone of the articular cartilage.

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

The levels of proteoglycan aggregate components (link protein, keratan sulfate epitope, and total sulfated glycosaminoglycan) were determined in the synovial fluid lavages of dogs with experimental osteoarthritis or disuse atrophy. A model of experimental osteoarthritis was created by transection of the anterior cruciate ligament of the right knee; studies were carried out 6 and 12 weeks after surgery. Joint disuse was studied at 4 and 8 weeks after initiation of the disuse. Recovery after disuse also was studied in joints that had 3 weeks of remobilization after 4 or 8 weeks of disuse. Synovial fluid lavages from the right knee joints of untreated animals were used as controls. The concentrations of keratan sulfate epitope, sulfated glycosaminoglycan, and link protein in the synovial fluid lavages at 6 and 12 weeks after transection of the anterior cruciate were elevated compared with the control values. Similar analysis of the fluid after disuse showed that the levels of keratan sulfate epitope and sulfated glycosaminoglycan were increased compared with the control levels and the levels after transection. However, the concentration of link protein in the fluid after disuse was not significantly different from the control level. The levels of keratan sulfate epitope and sulfated glycosaminoglycan in the synovial fluid lavages after disuse with recovery were high, but the levels of link protein remained low. The results indicate that the catabolism of proteoglycan aggregates in articular cartilage during early osteoarthritis and disuse is different. The determination of keratan sulfate epitope in synovial fluid lavages appears to provide a relatively general indication of proteoglycan catabolism, whereas increased levels of link protein may be more indicative of cartilage degeneration.

Temporal patterns of stromelysin-1, tissue inhibitor, and proteoglycan fragments in human knee joint fluid after injury to the cruciate ligament or meniscus

Stromelysin-1, tissue inhibitor of metalloproteinases-1 (TIMP-1), and proteoglycan fragments were quantified in knee synovial fluid samples in a cross-sectional study of patients who had injury to the anterior cruciate ligament or the meniscus. The average concentrations of stromelysin-1 and TIMP-1 increased 25-fold and 10-fold within the first day after the trauma, respectively, and the concentration of proteoglycan fragments increased 4-fold. From approximately 1-6 months after injury, the levels of these markers were higher after injury to the cruciate ligament than after injury to the meniscus. From 6 months to 18 years after trauma, however, the levels of stromelysin-1 and TIMP-1 in patients who had an injury to the ligament were the same as the levels in patients who had a meniscal lesion, but the levels were increased compared with those for a reference group of healthy volunteers. The molar balance of stromelysin-1 to TIMP-1 in synovial fluid in both groups of injured joints changed from a balance representing an excess of free inhibitor in the normal joint to one representing an excess of free enzyme in the injured joint. The increased release of these markers to joint fluid both early and late after trauma may be caused by a change in the loading patterns in the knee with an injured ligament or meniscus or by synovitis induced by bleeding. The increased release may be associated with the frequent development of posttraumatic osteoarthritis in patients with these injuries.

In vitro effect of hormones and growth factors on the incorporation of [3H]leucine, [35S]sulfate and [3H]proline by chondrocytes of aging mice

The ability of parathyroid hormone (PTH 1-84), dexamethasone, prostaglandin E1 (PGE1), prostaglandin E2 (PGE2) and human transforming growth factor beta (hTGF-beta) to stimulate the synthesis of matrical components in articular cartilage of aging mice, was studied in an organ culture system. A marked age-dependent decrease was observed in the synthesis of sulfated glycosaminoglycans (GAGs), protein, collagen digestible protein (CDP) and non-collagen protein (NCP) between 1 and 18 months of age. The addition of hTGF-beta (1 ng/ml) into the culture medium resulted in a significant (P < 0.01) increase of both protein and sulfated GAGs in condylar cartilage from animals aged 1, 3, 6 and 12 months. PGE2 (10 micrograms/ml) induced [3H]leucine and [35S]SO4 incorporation into condylar cartilage from 1, 3 and 6 months old animals. A stimulatory effect of PGE1 (10 micrograms/ml) on [3H]leucine incorporation was noted at 1 and 3 months of age. The effect of PTH appeared to be stimulatory only for protein synthesis in young (1 and 3 months old) animals, whereas it had no effect at 6, 12 and 18 months of age. In contrast, dexamethasone exerted a stimulatory effect on young adults (6 months old) and in matured (12 months old) animals, respectively and a slight inhibitory effect on young (1 and 3 months old) animals. [3H]Proline incorporation was enhanced by all the factors tested in 1-month-old animals. In cultures from 6- and 18-month-old animals only PGE1 and PGE2 appeared to be stimulatory. It is concluded that synthesis of protein, sulfated GAGs and collagen by chondrocytes from maturing and osteoarthritic senescent animals can be stimulated by hormones and growth factors. The efficiency of this response, however, varied according to the animal's age and the factor studied.

Viscoelastic shear properties of articular cartilage and the effects of glycosidase treatments

The objectives of this study were to determine the viscoelastic shear properties of articular cartilage and to investigate the effects of the alteration of proteoglycan structure on these shear properties. Glycosidase treatments (chondroitinase ABC and Streptomyces hyaluronidase) were used to alter the proteoglycan structure and content of the tissue. The dynamic viscoelastic shear properties of control and treated tissues were measured and statistically compared. Specifically, cylindrical bovine cartilage specimens were subjected to oscillatory shear deformation of small amplitude (gamma degrees = 0.001 radian) over a physiological range of frequencies (0.01-20 Hz) and at various compressive strains (5, 9, 12, and 16%). The dynamic complex shear modulus was calculated from the measurements. The experimental results show that the solid matrix of normal articular cartilage exhibits intrinsic viscoelastic properties in shear over the range of frequencies tested. These viscoelastic shear properties were found to be dependent on compressive strains. Our data also provide significant insights into the structure-function relationships for articular cartilage. Significant correlations were found between the material properties (the magnitude of dynamic shear modulus, the phase shift angle, and the equilibrium compressive modulus), and the biochemical compositions of the cartilage (collagen, proteoglycan, and water contents). The shear modulus was greatly reduced when the proteoglycans were degraded by either chondroitinase ABC or Streptomyces hyaluronidase. The results suggest that the ability of collagen to resist tension elastically provides the stiffness of the cartilage matrix in shear and its elastic energy storage capability. Proteoglycans enmeshed in the collagen matrix inflate the collagen network and induce a tensile prestress in the collagen fibrils. This interaction of the collagen and proteoglycan within the cartilage matrix provides the complex mechanism that allows the tissue to resist shear deformation.

The effects of intraarticular administration of hyaluronan in a model of early osteoarthritis in sheep. II. Cartilage composition and proteoglycan metabolism

A model of early osteoarthritis (OA) induced in ovine joints by medial meniscectomy was used to study the effects of two hyaluronan (HA) preparations (AHA and DHA) on cartilage composition and proteoglycan (PG) metabolism. DHA was an HA preparation with an average molecular weight (MW) of approximately 2.0 x 10(6) d, and AHA had an MW of approximately 8.0 x 10(5) d. Both preparations were administered intraarticularly once a week for 5 weeks starting 16 weeks after meniscectomy, and animals (n = 5) were killed 5 weeks after the last injection. Meniscectomized, saline-injected (n = 5) and nonoperated (n = 5) animals were used for controls. At necropsy, 3-mm-diameter full-depth cartilage plugs were sampled under sterile conditions from specific locations on the medial and lateral femoral condyles, tibial plateaus, patella, and trochlear groove. The cartilage plugs were cultured in Hams-F12 medium supplemented with 10% fetal calf serum for 24 hours, then for a further 48 hours in the presence of H2(35)SO4 to determine the biosynthesis of PGs. The percentage of 35S-PGs and sulfated glycosaminoglycans released into the media was also ascertained. The cartilage adjacent to the plugs was analyzed for collagen and proteoglycan content and differential extractability with guanidine hydrochloride (GuHCl) solutions. The extractability of PGs with 0.4 mol/L GuHCl (nondissociative conditions) was lower from the medial femoral cartilages of the DHA-treated group than from the corresponding saline-treated group. In contrast, the release of 35S-PGs from the tibial cartilages of the DHA-treated animals was higher than in the saline-treated group. The biosynthesis of 35S-PGs, determined in vitro, for cartilage derived from the medial compartment was generally lower than for the lateral regions of the meniscectomized joints. The biosynthetic activity was further reduced in joints injected with the two HA preparations, but DHA reduced 35SO4 incorporation into PGs more than AHA. It was concluded that reduced biosynthesis of 35S-PGs and secretion into media was a consequence of increased loading of joints in the HA-treated animals rather than a direct effect of these preparations on chondrocyte metabolism.

Elevated synovial fluid levels of interleukin-6 and tumor necrosis factor associated with early experimental canine osteoarthritis

OBJECTIVE

To measure levels of cytokines, proteases, and glycosaminoglycans (GAG) in synovial fluid (SF) from the knees of animals with experimental osteoarthritis (OA) and from their contralateral (control) knees, and to compare and correlate these values with each other as well as with measures of proteoglycan synthesis in the corresponding articular cartilage. This study will help to identify cytokines of potential importance in the early stages of the development of OA.

METHODS

OA was induced in 12 mature animals by sectioning the anterior cruciate ligament. After 3 months, SF from the operated and contralateral (control) knee joints was assayed for interleukin-6 (IL-6), tumor necrosis factor (TNF), IL-1, latent metalloproteinase, and sulfated GAG. Proteoglycan synthesis in the corresponding articular cartilage was also measured.

RESULTS

IL-6 levels in SF from the operated joint compared with the control joint were significantly elevated in 11 of 12 animals. TNF levels were also elevated in 10 of 11 SF samples from operated joints, but to a lesser extent than those of IL-6. IL-1 and IL-1 inhibitors were undetectable in either the operated or control joint SF. The GAG concentration was elevated in SF from experimental OA joints. This elevation correlated with that of TNF, but not IL-6. There was no significant difference in the concentration of APMA-activatable metalloproteinase. The rate of proteoglycan synthesis was higher in the cartilage from the operated joint in 8 of 12 animals, and the mean rate of synthesis was significantly higher than in the control joint. There was a positive correlation between this increase in cartilage proteoglycan synthesis (operated versus control) and the increase in SF IL-6, but there was no correlation with the levels of TNF or GAG.

CONCLUSION

This is the first study of SF levels of cytokines in early experimental OA. Our results show surprisingly high levels of IL-6 in operated joints, where the cytokine could act directly on the chondrocytes, and thus play a role in mediating their responses to cartilage injury.

The quantitation of a native chondroitin sulfate epitope in synovial fluid lavages and articular cartilage from canine experimental osteoarthritis and disuse atrophy

OBJECTIVE

Previous studies have shown the presence of a native chondroitin sulfate epitope in articular cartilage proteoglycans from canine knee joints with experimental early osteoarthritis (OA), but not in normal cartilage. The objective of this study was to quantitate the native epitope recognized by monoclonal antibody 3-B-3 in synovial fluids and articular cartilage of diseased joints.

METHODS

An immunoassay with monoclonal antibody 3-B-3, which recognizes a native chondroitin-6-sulfate structure, was developed and used to analyze synovial fluid lavage material and extracts of articular cartilage from canine knee joints with early experimental OA or with mild disuse atrophy, and from control animals.

RESULTS

The concentration of epitope in the OA fluids was elevated 33-35-fold, and in the OA articular cartilage extracts it was elevated > 200-fold, compared with samples from the control group. No significant difference was detected in the levels of 3-B-3 epitope in the synovial fluid lavage material or cartilage extracts from the joints of the disuse group versus the control group.

CONCLUSION

The native 3-B-3 epitope in articular cartilage and synovial fluids may be a specific marker of ongoing anabolic events in early degenerative joint disease.

The effect of naproxen and interleukin-1 on proteoglycan catabolism and on neutral metalloproteinase activity in normal articular cartilage in vitro

The events in inflammatory and degenerative joint diseases involve major changes in the metabolic events in the articular cartilage. The effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on articular cartilage metabolism remain unclear, however. The objective of this catabolism of proteoglycans in articular cartilage explants maintained in culture. Release of proteoglycan from the cartilage was compared with release of neutral metalloproteinase activity. The effect of the drug also was determined on the IL-1-stimulated release of proteoglycan and neutral metalloproteinase activity from the explants. At concentrations that included those present in synovial fluids of patients treated with the drug, naproxen sodium was found to suppress the release of proteoglycan and neutral metalloproteinase activity from the articular cartilage extracts. This is in contrast to the well-documented effect of interleukin-1 (IL-1), which was shown to stimulate release of proteoglycan and neutral metalloproteinase activity from articular cartilage. The effect of naproxen sodium on the IL-1-stimulated release was to suppress, but not totally overcome, the increased release of proteoglycan and neutral metalloproteinase activity. In summary, these in vitro studies of cartilage metabolism indicate that naproxen sodium has the potential to suppress catabolic activities in articular cartilage, including those that are motivated by IL-1.