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PubMed2004

Influence of tissue maturation and antioxidants on the apoptotic response of articular cartilage after injurious compression.

OBJECTIVE: To study the influence of tissue maturation and antioxidants on apoptosis in bovine articular cartilage induced by injurious compression. METHODS: Bovine articular cartilage disks were obtained from the femoropatellar groove of animals ages 0.5-23 months and placed in culture. Cartilage disks were preincubated overnight with the cell-permeable superoxide dismutase (SOD) mimetic Mn(III) porphyrin (0-12.5 microM) or alpha-tocopherol (0-50 microM) and then injured by a single unconfined compression to a final strain of 50% at a velocity of 1 mm/second. After 4 days of additional incubation, the disks were fixed and embedded for light and electron microscopy. Apoptotic cells were quantified morphologically by the appearance of nuclear blebbing on light microscopy. Biosynthetic activity was demonstrated by incorporation of radiolabeled proline. The antioxidative action of the SOD mimetic was confirmed by histologic examination of cartilage after incubation with nitroblue tetrazolium. RESULTS: Injurious compression induced significantly more apoptosis in cartilage disks from newborn calves (22% of cells) than in cartilage from more mature cows (2-6%). In cartilage from 22-month-old animals, the SOD mimetic reduced the percentage of apoptotic cells induced by injury in a dose-dependent manner (complete inhibition with 2.5 microM), while alpha-tocopherol had no effect. Neither antioxidant altered protein biosynthesis or cellular ultrastructure. CONCLUSION: Our data suggest that the apoptotic response of articular cartilage to mechanical injury is affected by maturation and is mediated in part by reactive oxygen species. The antioxidative status of the tissue might be important for the prevention of mechanically induced cell death in articular cartilage.

Age Factors↗
PubMed1996

Maintenance of equine articular cartilage explants in serum-free and serum-supplemented media, compared with that in a commercial supplemented medium.

OBJECTIVE: To evaluate the effects of a commercially defined, serum-free medium additive on equine articular cartilage explants, compared with effects of serum-free and serum-supplemented media. ANIMALS: Articular cartilage from a 3-year-old, mixed breed horse euthanatized for reasons other than musculoskeletal disease or sepsis. PROCEDURE: Media were changed every 48 hours, and the glycosaminoglycan (GAG) content was determined in media collected at each time point. Glycosaminoglycan synthesis by explant chondrocytes, and residual GAG content of articular cartilage (as a measure of explant GAG loss) were determined at the end of the study (day 8). RESULTS: Articular cartilage explants in serum-free medium and the commercial supplemented medium had significantly lower GAG synthesis and GAG content than did those incubated in serum-supplemented medium. There were no significant differences in GAG synthesis and content between serum-free and commercial supplemented medium groups. When comparing medium GAG content for all treatment groups, the GAG content in serum-free medium on day 8 was significantly greater than that in commercial supplemented medium, but significant differences were not evident in percentage of release of GAG (as an indicator of GAG degradation) among all 3 treatment groups. CONCLUSIONS: Commercial supplemented medium had effects on articular cartilage matrix GAG loss into medium equal to those of serum-supplemented medium (eg, both lost articular cartilage explant GAG to a similar degree). However, residual articular cartilage GAG content was higher in serum-supplemented medium, as was GAG synthesis. Commercial supplemented medium appears to either lack the proper ingredients to maintain steady-state GAG synthesis, or lacks proper concentrations of these ingredients.

Analysis of Variance↗
PubMed1996

Application of finite elements to the stress analysis of articular cartilage.

A common effect of arthritic disease processes in synovial joints is deterioration of the articular cartilage. Therefore, an improved understanding of the relationships between the composition and structure of articular cartilage and the mechanical behaviour is a subject of considerable interest. The numerical modelling tool of finite element (FE) analysis has been widely applied to analyse the behaviour of articular cartilage under compressive stress. FE analysis enables parameters and boundary conditions to be investigated which are not accessible experimentally or analytically. The biphasic theory describes the constitutive behaviour of soft hydrated biological tissues, such as articular cartilage, and has been successfully implemented using FE analysis. The development of successively more comprehensive biphasic models is described here detailing the use of FE analysis in modelling experimental configurations such as indentation. Key work in the area is reviewed in this paper.

Animals↗
PubMed1984

Synthesis of fibronectin in normal and osteoarthritic articular cartilage.

The content and the biosynthesis of fibronectin was examined in disease-free articular cartilage and in articular cartilage from osteoarthritic canine joints. Fibronectin content was increased in extracts of cartilage from osteoarthritic joints. Incubation of cartilage in vitro with [3H]phenylalanine and subsequent isolation of [3H]fibronectin from a gelatin affinity column and characterization by SDS-polyacrylamide gel electrophoresis and by immunoprecipitation indicated that disease-free and osteoarthritic cartilage explants synthesized fibronectin. About 50% of the [3H]fibronectin was recovered in the incubation medium. The osteoarthritic cartilage synthesized and accumulated up to 5-fold more [3H]fibronectin than disease-free cartilage.

Cartilage, Articular↗
PubMed2001

Collagen of articular cartilage.

The extracellular framework and two-thirds of the dry mass of adult articular cartilage are polymeric collagen. Type II collagen is the principal molecular component in mammals, but collagens III, VI, IX, X, XI, XII and XIV all contribute to the mature matrix. In developing cartilage, the core fibrillar network is a cross-linked copolymer of collagens II, IX and XI. The functions of collagens IX and XI in this heteropolymer are not yet fully defined but, evidently, they are critically important since mutations in COLIX and COLXI genes result in chondrodysplasia phenotypes that feature precocious osteoarthritis. Collagens XII and XIV are thought also to be bound to fibril surfaces but not covalently attached. Collagen VI polymerizes into its own type of filamentous network that has multiple adhesion domains for cells and other matrix components. Collagen X is normally restricted to the thin layer of calcified cartilage that interfaces articular cartilage with bone.

Cartilage, Articular↗
PubMed2000

Topographical variation of the elastic properties of articular cartilage in the canine knee.

Equilibrium response of articular cartilage to indentation loading is controlled by the thickness (h) and elastic properties (shear modulus, mu, and Poisson's ratio, nu) of the tissue. In this study, we characterized topographical variation of Poisson's ratio of the articular cartilage in the canine knee joint (N=6). Poisson's ratio was measured using a microscopic technique. In this technique, the shape change of the cartilage disk was visualized while the cartilage was immersed in physiological solution and compressed in unconfined geometry. After a constant 5% axial strain, the lateral strain was measured during stress relaxation. At equilibrium, the lateral-to-axial strain ratio indicates the Poisson's ratio of the tissue. Indentation (equilibrium) data from our prior study (Arokoski et al., 1994. International Journal of Sports Medicine 15, 254-260) was re-analyzed using the Poisson's ratio results at the test site to derive values for shear and aggregate moduli. The lowest Poisson's ratio (0.070+/-0.016) located at the patellar surface of femur (FPI) and the highest (0.236+/-0.026) at the medial tibial plateau (TMI). The stiffest cartilage was found at the patellar groove of femur (micro=0.964+/-0.189MPa, H(a)=2.084+/-0. 409MPa) and the softest at the tibial plateaus (micro=0.385+/-0. 062MPa, H(a)=1.113+/-0.141MPa). Comparison of the mechanical results and the biochemical composition of the tissue (Jurvelin et al., 1988. Engineering in Medicine 17, 157-162) at the matched sites of the canine knee joint indicated a negative correlation between the Poisson's ratio and collagen-to-PG content ratio. This is in harmony with our previous findings which suggested that, in unconfined compression, the degree of lateral expansion in different tissue zones is related to collagen-to-PG ratio of the zone.

Analysis of Variance↗
PubMed1991

Biochemical changes in knee joint articular cartilage after cemented prosthetic hip hemiarthroplasty in dogs.

Biochemical changes in the distal femoral articular cartilage (knee joint) after cemented prosthetic replacement of the femoral head were determined. Femurs from dogs (n = 10) that had undergone cobalt-chromium prosthetic hip hemiarthroplasty (6-8 months postoperatively) were analyzed for articular cartilage lipids in the distal femur. The quantity of phosphatidylserine increased from 0.59 +/- 0.14 mg (uninvolved) to 1.52 +/- 0.23 mg (hemiarthroplasty) lipid phosphorus/100 g tissue, and the quantity of arachidonic acid in the articular cartilage increased from 0.23 +/- 0.07 mg (uninvolved) to 2.07 +/- 0.29 mg/100 g tissue (hemiarthroplasty). Likewise, hydroxyproline content was higher in the recipient femurs (77.4 +/- 1.58 micrograms/mg cartilage) versus uninvolved femurs (71.8 +/- 1.03 micrograms/mg cartilage); the activity of acid phosphatase was greater in the recipient distal femoral cartilage as compared with the uninvolved femur, 0.07 +/- 0.01 and 0.06 +/- 0.02 mol hydrolyzed per kilogram per hour, respectively, and the hexosamine content was lower in the recipient femur knee cartilage versus knee cartilage from uninvolved femurs, 54.5 +/- 1.51 and 63.1 +/- 1.37 micrograms/mg cartilage, respectively. These biochemical changes may suggest degeneration of the knee joint articular cartilage after cemented hip hemiarthroplasty.

Acid Phosphatase↗
PubMed1996

Magnetic resonance chondro-crassometry (MR CCM): a method for accurate determination of articular cartilage thickness?

A method for the assessment of articular cartilage thickness based on MRI is presented and its accuracy and reproducibility tested. Six specimens of human patellae were imaged, using a fat-suppressed FLASH 3D sequence, and sectioned with a high-precision band saw. The regional distribution of articular cartilage thickness was determined from the MR images and from the anatomical sections (intervals of 0.5 mm). With image analysis 50-90% of the image points were found to lie within exactly the same thickness interval in corresponding patterns, and less than 17% deviated more than 0.5 mm. More than 85% of all pixels were reproducible with MRI after new positioning of the joint. No influence of the read-out direction and no important differences between areas of thin and thick cartilage could be detected. The authors conclude that MR chondro-crassometry can provide accurate and reproducible information on cartilage thickness.

Adult↗
PubMed2003

The effect of cyclical compressive loading on gene expression in articular cartilage.

Osteoarthritis (OA) develops as a consequence of articular cartilage degeneration possibly initiated by excessive or abnormal loading of the joint, and potentially mediated through a proteinase/proteinase inhibitor imbalance. We have shown previously that physiological loads (0.5 MPa, 1 Hz, 3 hour) elicit increased expression and activation of the matrix metalloproteinases (MMPs) in articular cartilage explants in vitro. The objective of this study was to identify mechanically-regulated genes involved in the observed induction of MMP expression and enhanced activation. Differential RNA Display (DRD) was used to identify mechanically-regulated genes by comparing DRD products derived from loaded and unloaded cartilage. One gene up-regulated in cartilage after 10, 30 and 60 minute loading revealed 83% homology with Mus musculus thymosin beta_4 which is known to induce MMP gene expression. The identification of mechanically regulated genes will greatly enhance our understanding of matrix turnover providing an exciting future in elucidating the role of mechanically-regulated genes in the development of OA.

Animals↗
PubMed1991

Three-dimensional collagen architecture in bovine articular cartilage.

The three-dimensional architecture of bovine articular cartilage collagen and its relationship to split lines has been studied with scanning electron microscopy. In the middle and superficial zones, collagen was organised in a layered or leaf-like manner. The orientation was vertical in the intermediate zone, curving to become horizontal and parallel to the articular surface in the superficial zone. Each leaf consisted of a fine network of collagen fibrils. Adjacent leaves merged or were closely linked by bridging fibrils and were arranged according to the split-line pattern. The surface layer (lamina splendens) was morphologically distinct. Although ordered, the overall collagen structure was different in each plane (anisotropic) a property described in previous morphological and biophysical studies. As all components of the articular cartilage matrix interact closely, the three-dimensional organisation of collagen is important when considering cartilage function and the processes of cartilage growth, injury and repair.

Animals↗
PubMed2005

Contrasting alterations of apposed and unapposed articular cartilage during joint contracture formation.

OBJECTIVE: To quantify histologic articular cartilage alterations after immobilization, distinguishing between apposed and unapposed sites in an animal model of joint contracture. DESIGN: Experimental controlled trial. SETTING: Laboratory, in vivo study. ANIMALS: Adult male Sprague-Dawley rats (N=128). INTERVENTIONS: One hundred seventeen animals had 1 knee internally immobilized or sham-operated for 2, 4, 8, 16, or 32 weeks. One knee in 11 nonoperated animals served as controls. Main outcome measures On standardized sections, we identified femur and tibia cartilage sites that were apposed or that were unapposed. We quantified 4 characteristics: number of chondrocytes in the superficial and deep cartilage; matrix staining intensity to toluidine blue; surface irregularity of articular cartilage; and thickness of cartilage. RESULTS: Immobilized knees harbored fewer chondrocytes in the superficial cartilage at apposed sites and in the deep cartilage at unapposed sites. Matrix staining decreased only at unapposed sites. Cartilage surface became significantly more irregular at both sites but cartilage thickness remained unchanged. Noncartilaginous tissues appeared only at unapposed sites in the superficial and deep cartilage. CONCLUSIONS: Immobilization led to contrasting patterns of cartilage degeneration at apposed sites compared with unapposed sites. These results suggest distinct pathogenetic pathways for cartilage alterations, possibly through absence of mechanical forces (negative mechanotransduction) at unapposed sites and cyclic pressure at apposed sites. Considering the limited potential for cartilage self-repair, these results support the need for early diagnosis and aggressive mobilization of joints that are developing contractures.

Animals↗
PubMed1980

Age-related changes in the thickness of the calcified zone and the number of tidemarks in adult human articular cartilage.

The thickness of the calcified zone of the articular cartilage and the number of tidemarks at the junction between articular cartilage and bone has been determined in specimens from 41 femoral heads and 42 humeral heads from cadavers aged between 25 and 93. The thickness of the calcified zone decreased with age but the number of tidemarks increased, particularly over the age of 60. These observations suggest that remodelling of the bone ends occurs and that this process is accelerated with increasing age.

Adult↗
PubMed1998

[Repair of articular cartilage defect with a large area: an experimental study].

OBJECTIVE: To compare and evaluate potentialities and biological characteristics of grafts of chondrocytes cultured on fascia, periosteum and articular cartilage in repairing large defects of articular cartilage. METHOD: The large defects of articular cartilage were repaired with grafts of freeze-stored and fresh chondrocytes cultured on fascia, periosteum and articular cartilage, which were evaluated by a number of observation methods. RESULT: The fresh and freeze-stored fascial chondrocytes were superior to free grafts of chondrocytes in potentiality of formation of new cartilaginous tissue, structure and metabolism of newly formed tissue. Relatively good results were also obtained similarly by using fresh autografts of periosteum and cartilage. CONCLUSION: Chondrocytes can be cultured normally on fascia, which can be regarded as an ideal carrier of chondrocytes.

Animals↗
PubMed1986

Incorporation of purified plasma fibronectin into explants of articular cartilage from disease-free and osteoarthritic canine joints.

The purpose of this study was to determine if articular cartilage was able to accumulate fibronectin, a large molecule of 440,000 daltons, from the external medium, and if so, to compare the extent of accumulation by normal and osteoarthritic cartilage and to localize the sites of fibronectin accumulation within the articular cartilage. The uptake of canine serum albumin, another protein present in plasma and synovial fluid with a lower molecular weight (67,000 daltons) and a lower pI, was compared. Purified plasma fibronectin and canine albumin were labelled with 125I or N-hydroxysuccinimidobiotin by standard procedures and incubated with articular cartilage explants. The 125I-fibronectin that had bound to cartilage components was extracted with 4 M urea, and both extract and cartilage residues were counted. Cartilage accumulated fibronectin to a greater extent than albumin. For normal cartilage, a level of saturation appeared to be reached at an external concentration for fibronectin of about 150 micrograms/ml. Degenerated cartilage accumulated about 10-fold more fibronectin than normal cartilage. Biotinylated fibronectin was localized within frozen sections of articular cartilage by probing with peroxidase-linked avidin. Fibronectin accumulation in normal cartilage was restricted to the articular surface and the cut edge. In degenerated cartilage, penetration of fibronectin was more extensive but proceeded only from the articular surface. Staining of adjacent sections with peroxidase-linked antifibronectin antibody confirmed previous observations that endogenous fibronectin is present throughout the cartilage matrix. The possibility that synovial fluid fibronectin could be a source of cartilage fibronectin, especially in degenerated cartilage, was discussed.

Animals↗
PubMed2006

Assessment of the use of RNA quality metrics for the screening of articular cartilage specimens from clinically normal dogs and dogs with osteoarthritis.

OBJECTIVE: To assess 2 methods of RNA purification by use of different quality metrics and identify the most useful metric for quality assessment of RNA extracted from articular cartilage from dogs with osteoarthritis. SAMPLE POPULATION: 40 articular cartilage specimens from the femoral heads of 3 clinically normal dogs and 37 dogs with osteoarthritis. PROCEDURES: RNA was extracted from articular cartilage by 2 purification methods. Quality metrics of each sample were determined and recorded by use of a UV spectrophotometer (Spec I; to determine the 260 to 280 nm absorbance ratio [A(260):A(280) ratio]), a second UV spectrophotometer (Spec II; to determine A(260):A(280) and A(260):A(230) absorbance ratios), and a microfluidic capillary electrophoresis analyzer (to determine the ribosomal peak ratio [RR], degradation factor [DF], and RNA integrity number [RIN]). The RNA was extracted from affected (osteoarthritic) articular cartilage and assessed with the same quality metrics. Metric results were compared with visual analysis of the electropherogram to determine the most useful RNA quality metric. RESULTS: No differences in methods of RNA purification were determined by use of quality metrics. The RNA extracted from unaffected (normal) cartilage was of higher quality than that extracted from affected (osteoarthritic) cartilage, as determined by the RIN and Spec II A(260):A(230) ratio. The RIN and RR were the most sensitive metrics for determining RNA quality, whereas the DF was most specific. A significant proportion (32%) of RNA extracted from osteoarthritic articular cartilage specimens was determined as being of low quality. CONCLUSIONS AND CLINICAL RELEVANCE: No single metric provided a completely sensitive and specific assessment of the quality of RNA recovered from articular cartilage.

Animals↗
PubMed1984

Lipid peroxides in human articular cartilage.

The hypothesis that increased generation of lipid peroxides (LP) causes articular cartilage damage in older patients and in those with osteoarthritis was tested by directly measuring LP tissue levels in various layers of human articular cartilage. The LP content was significantly greater in the superficial than in the deeper portion of the cartilage, but lower in cartilage than in liver, kidney, adrenal glands and synovium. When LP were related to the total lipid content of these tissues, a high peroxide per lipid ratio was obtained for articular cartilage. The relevance of these findings to the mechanism of cartilage fibrillation is discussed.

Adrenal Glands↗
PubMed1995

Tenascin-C and the development of articular cartilage.

In comparison to the vast literature on articular cartilage structure and function, relatively little is known about how articular cartilage forms during embryogenesis and is endowed with unique phenotypic properties, most notably the ability to persist and function throughout postnatal life. In this minireview, we summarize recent studies from our laboratory suggesting that the extracellular matrix protein tenascin-C is involved in the genesis and function of articular chondrocytes. These and other data have led us to propose that tenascin-C may be part of in vivo mechanisms whereby articular chondrocytes develop at the epiphysis of long bone models, remain functional throughout postnatal life, and avoid the endochondral ossification process undertaken by the bulk of chondrocytes located in the metaphysis and diaphysis of skeletal models.

Animals↗
PubMed1992

Ultrastructural analysis of the adaptation of articular cartilage to mechanical stimulation.

Ultrastructural analysis was conducted on samples of articular cartilage taken from both load-bearing and non-load-bearing areas with the aim of evaluating the morphologic adaptation of the articular cartilage to mechanical stimulation and identifying the mechanisms of interaction of the chondrocyte and the matrix. Through this analysis we were able to better define the adaptation process of the cartilage as well as the modalities of mechanical stress transmission. We believe that the complex formed by the chondrocyte, the pericellular matrix, and the pericellular capsule constitutes the biomechanical unit of the articular cartilage which serves as the sensor and transducer of mechanical stress. The arrangement of the collagen fibers and the proteoglycans which make up the pericellular capsule and membrane around the chondrocyte can be compared, from a mechanical standpoint, to a dynamic structure constructed in order to absorb the load stresses and protect the internal environment. From a biological standpoint, these are comparable to an extracellular-scaffold constructed with the aim of mediating the interaction between the chondrocyte and the territorial and inter-territorial compartments.

Adaptation, Physiological↗