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PubMed1986

Mechanical and biochemical properties of human articular cartilage from the femoral head after subcapital fracture.

Articular cartilage from the femoral heads of 27 patients having an arthroplasty for subcapital fracture was studied, and its mechanical and chemical properties compared to those of a group of 33 age-matched macroscopically normal autopsy specimens. Water and proteoglycan contents were measured, as were swelling ability, compressive and tensile strength of the cartilage, and the density of the underlying bone. Cartilage from the fracture specimens had a significantly reduced proteoglycan content, as measured by fixed charge density, and increased swelling ability. These results indicate that this group differs from the "normal" population and care should be taken before they are accepted as control material for studies on osteoarthritic cartilage. Another finding was that bone density was much the same in the fracture and the normal group. This casts some doubt upon the concept that patients who sustain subcapital fractures are more osteoporotic than the average for the same age range.

Adolescent↗

PubMed1983

Proteoglycan alterations in rabbit knee articular cartilage following physical exercise and immobilization.

Rabbit knee articular cartilage was studied after the joint was submitted to immobilization, running or increased weight bearing for 24-27 days. Immobilization with a plastic splint reduced the fraction of proteoglycans not extractable with 4 M guanidinium chloride (GdnHCl). In the immobilized joints the chondroitin sulfate content was elevated as calculated from the galactosamine/glucosamine ratio. The ability of these proteoglycans to reform aggregates with endogenous hyaluronic acid in Sepharose CL-2B chromatography was reduced. Increased exercise was associated with an elevation of proteoglycans extractable with 4 M GdnHCl. The increased weight bearing occurring in the contralateral knee elevated the content of proteoglycans not extractable with 4 M GdnHCl. Other effects of weight bearing included increased glucosamine concentration, suggesting accumulation of keratan sulfate-rich proteoglycans, and an elevated hydroxyproline concentration.

Animals↗

PubMed1985

En bloc staining of articular cartilage and bone.

Blocks of canine and porcine articular cartilage were stained en bloc with Weigert's iron hematoxylin or Harris' hematoxylin with or without eosin Y counterstaining and cleared in methyl salicylate. The morphology and three-dimensional relationships of chondrocytes were best demonstrated with Weigert's iron hematoxylin. The morphology of the cartilage and chondrocytes was superior to that in sections of routine hematoxylin and eosin stained, paraffin processed samples. The three-dimensional localization of intracellular lipids in individual and clones of chondrocytes was observed when cartilage samples were stained with oil red O and mounted directly in a water-based medium. Blocks of decalcified bone were stained en bloc with Weigert's iron hematoxylin and cleared with methyl salicylate. The three-dimensional orientation of osteocytes around osteonal canals, in circumferential lamellae, and in interstitial lamellae was demonstrated. The morphology of "cutting cones" in cortical bone also was observed.

Animals↗

PubMed1989

The effects of "matrigenin" activity from bovine bone on the glycosaminoglycans of bovine articular cartilage in culture. A model for cartilage repair by bone derived factors.

A bovine articular cartilage longterm culture system was used to study proteoglycan synthesis by a pulse labeling technique. A brief preincubation of the cartilage slices with bacterial collagenase was found to be an effective method of depleting proteoglycan. The addition of a fraction from bovine bone that contained partially purified "matrigenin" activity to the cultures resulted in the stimulation of incorporation of radioactive precursors into cartilage chondroitin sulfate, suggesting increased proteoglycan synthesis. The stimulatory effect of matrigenin activity was observed earlier and was more sustained if the cartilage slices were preincubated with collagenase. The system appears to be useful for testing the hypothesis that bone derived factors stimulate the repair of damaged cartilage.

Animals↗

PubMed1989

[Morphological studies on structure and function of the superficial zone of the articular cartilage].

Mechanical response of the superficial zone of articular cartilage was examined with a cryoscanning electron microscope. The superficial zone to which no load was applied had a smooth surface, and the thickness of the zone was from 150 to 280 microns. The loaded zone was compressed to several micra in thickness within the first 2 seconds. The superficial zone was shown to respond sensitively to mechanical stresses. To elucidate the structure of the superficial zone each of three major constituent elements was separately removed, and the morphological changes were observed. From the results the superficial zone was considered to have a honeycomb structure which had fluid-containing hyaluronate within. In the lubrication experiment the friction coefficient increased remarkably when the zone was destroyed by scrubbing off or by collagenase digestion. The honeycomb structure of the superficial zone was thought to play an important role in animal joint lubrication.

Animals↗

PubMed1988

A biomechanical profile across the patellar groove articular cartilage: implications for defining matrix health.

Macroscopically normal articular cartilage across all bovine patellar grooves studied exhibited a smooth gradation in mechanical properties. Rigorous standardisation of microtensile and microcompressive testing showed that stiffness in tension of the deep matrix, its tendency to rupture and compressive stiffness all dropped progressively across the medial margin and trough of the groove, and reached their lowest values at approximately one quarter of the distance up the lateral margin. The changes in mechanical properties were correlated with ultrastructural differences. The deep matrix of very stiff tissue from the medial margin showed a dense arrangement of fibril segments orientated with varying degrees of obliquity about a radial mean. The more compliant tissue had a markedly less dense fibrillar array with a pronounced radial orientation. It is suggested that the gradation in mechanical properties results from differential loading of the joint surface. From the available evidence it seems likely that the compliance of the cartilage increases proportionately with the reduction in load. The results are discussed with reference to Broom's (1986b) model of the fibrillar architecture of cartilage. It is proposed that increasing compliance is related to a graduated reduction across the joint surface in the number and/or strength of the interfibrillar bonds, resulting from differential loading. A proportionate number of fibrils would have a reduced number of short-period lateral deflections and thus an increasingly overall radial orientation. This would result in a concomitant graded reduction in the degree of constraint exerted by the three dimensional fibrillar network on the hydrated proteoglycans.

Animals↗

PubMed1987

Proteoglycan-degrading metalloproteases of human articular cartilage.

Two metalloproteases have been purified from human articular cartilage. These attack the core protein of proteoglycan with pH optima of 5.3 and 7.2. The acid protease retains 40% of its activity at physiological pH. The two proteases are related in their properties of latency, activation, substrate specificity, and inhibitor pattern. They differ in pI, pH optimum, molecular weight, calcium requirement, and action on gelatin. Both activities are elevated 3-5 fold in osteoarthritic cartilage. Both proteases attack Ala-Leu and Tyr-Leu bonds in the B-chain of insulin. It is postulated that the entire family of metalloproteases acting on extracellular matrix shares a common specificity for Gly(Ala)-Leu(Ile) bonds.

Cartilage, Articular↗

PubMed1977

Age changes in Alcian blue staining of glycosaminoglycans in sheep articular cartilage.

Alcian blue staining of glycosaminoglycans in sheep articular cartilage is described and discussed. Chodrocytes contain mainly low molecular weight chondroitin sulphate in the outer layers but keratan sulphate increases with depth. Protein-polysaccharide interaction increases with age but the cellular staining decreases in intensity with age. Lacunar capsules contain material of higher molecular weight, much of which is chondroitin sulphate, but no protein-polysaccharide interaction occurs. The matrix of the outer layers is deeply stained while that of the inner layer is pale and consists mainly of keratan sulphate. When stained in high salt concentrations (greater than 0-7 M) the matrix of the middle layer shows two zones; hyaluronidase treatment allows these zones to be differentiated at lower salt concentrations.

Aging↗

PubMed1975

Morphological changes in the articular cartilage after meniscectomy. An experimental study in the monkey.

The medial meniscus was resected from the right knees of twelve young grivet monkeys that were killed at intervals of twenty-one to 252 days after operation. The knees operated upon and the control knees were investigated radiologically and histologically. Degenerative changes occurred in the medial femoral and tibial condyles. At first there was loss of cells from the superficial layer of the articular cartilage, with a marked decrease in the acid mucopolysaccharide content of the matrix. The chondrocytes in the deeper layer of the non-calcified zone proliferated to form clones before finally degenerating. The acellular cartilage showed splitting, and with progress of the degenerative process there was thinning and erosion of the cartilage. Eventually there was complete loss of articular cartilage with thickening and exposure of the subchondral bone. These degenerative changes were confined to a small area of the articular cartilage and had occurred despite regeneration of the meniscus. The rest of the cartilage looked normal. It is concluded that articular cartilage deprived of the protection of a meniscus may undergo arthritic changes.

Animals↗

PubMed2004

Effects of long-term estrogen replacement therapy on articular cartilage IGFBP-2, IGFBP-3, collagen and proteoglycan levels in ovariectomized cynomolgus monkeys.

OBJECTIVE: The purpose of this study was to determine the effects of long-term estrogen replacement therapy (ERT) on insulin-like growth factor binding protein (IGFBP)-2, IGFBP-3, collagen and proteoglycan levels in the articular cartilage of the knee joint in a well-characterized monkey model of naturally occurring osteoarthritis (OA). A secondary aim was to evaluate the effect of soy phytoestrogen treatment on these articular cartilage components. DESIGN: Monkeys were ovariectomized and given ERT, soy phytoestrogen treatment or no treatment (control) for 3 years. Ten animals were randomly selected from each of the three groups and the cartilage was dissected from the proximal tibia and distal femur of the knee. Levels of IGFBP-2, IGFBP-3, and total protein were measured in cartilage desorptions, and proteoglycan levels and collagen levels were measured in the cartilage tissue. Sections from the tibial plateau of the opposite knee were immunostained using antibodies directed against IGFBPs and evaluated subjectively. RESULTS: IGFBP-3 levels were significantly higher, and total protein levels were significantly lower in the cartilage desorption samples from the estrogen-treated animals compared to the control animals. There were no significant differences in IGFBP-2, collagen or proteoglycan levels between the estrogen-treated and control groups. Soy phytoestrogen treatment had no significant effect on the levels of any of the cartilage components that were measured. The staining patterns observed by immunohistochemistry suggested local production of IGFBP-2 and IGFBP-3 by articular cartilage chondrocytes. CONCLUSIONS: Long-term estrogen treatment results in increased IGFBP-3 levels in articular cartilage without a significant change in IGFBP-2, collagen or proteoglycan content, and IGFBP-3 appears to be synthesized by articular cartilage chondrocytes. Long-term soy phytoestrogen treatment did not have a statistically significant effect on the levels of IGFBP-2, IGFBP-3, collagen or proteoglycan.

Animals↗

PubMed1996

Cryoscanning electron microscopy of loaded articular cartilage with special reference to the surface amorphous layer.

The surface layer (i.e. the surface lamina) of articular cartilage, which is devoid of a collagen fibril network or cells, was investigated in the pig and human. It overlies the collagenous main part of the articular cartilage which contains chondrocytes and is thought to be important biomechanically. In order to examine morphological changes in this layer when under load, knee articular cartilage of the pig, along with the underlying subchondral bone, was compressed with a cylindrical indenter. The specimen was frozen by immersion in liquid nitrogen to maintain the loaded condition and was then freeze-fractured at the indented region. The fracture face was examined with a cryoscanning electron microscope. The surface layer was compressed beneath the indenter regardless of loading pressure or period and was expanded around the indenter to form a triangular bulge in cross section. The height of the bulge was related to the applied pressure and not to the loading period. Recovery of the cartilage from indentation was also examined. Immediately after removal of the indenter, the bulge of the surface layer moved back into the previously indented region. The region was covered by a thick surface layer after 2 s. The response of the surface layer to and recovery from indentation was largely instantaneous and elastic. Under heavy load conditions, the main part of the cartilage under the indenter was observed to have a striped pattern which was made up of bands of densely packed collagen fibrils with fibrillar networks remaining between them. These morphological findings agree well with previously reported biomechanical hypotheses and can be explained by the flow of interstitial fluid provoked by stress application.

Animals↗

PubMed1992

[Relation of ultrastructural changes of articular cartilage and the arthroscopic classification in osteoarthritic knee].

This paper reported the ultrastructural changes found in the diseased articular cartilages of 43 osteoarthritic knee joints, which were assessed according to the "Arthroscopic classification of the articular cartilage". The electron microscopic findings and the arthroscopic classification of the articular lesions were correlated. The lesioned articular cartilage revealed two categories of pathological changes. 1. The changes on the part of the articular chondrocytes comprised (1) The nucleus showed pyknosis and karyorrhexis. (2) The cytoplasm exhibited fat droplets, glycogen granules, and/or microfilaments. Lysosomes also emerged frequently. The mitochondria swelled and the rough-surfaced endoplasmic reticulum dilated and became vesiculated. At the same time there was detachment of cell processes or of the cytoplasmic membrane. The chondrocyte underwent necrosis, contracted and eventually disintegrated into lipid debris. These changes increased in extent and degree with the lesion and the severity went parallel with the sequence of the "Arthroscopic stage classification". 2. The changes on the part of the matrix included appearance of electron-dense lipid debris and numerous, coarse and banded collagen fibrils. They resided both in the pericellular matrix and in the general matrix. Sometimes fibroblast-like cells made their appearance in the matrix. These cells also revealed degenerative changes. All these changes went parallel with the sequence of the "Arthroscopic grade classification".

Arthroscopy↗

PubMed1988

Morphological investigation of cavity formation in articular cartilage induced by ofloxacin in rats.

Ofloxacin, a quinolone antibacterial agent, induced blisters and/or erosions in the articular cartilage of the humeral trochlea, femoral condyle, and femoral head of immature rats. Histologically, cavity formation was seen in the middle zone of the articular cartilage. Changes were detected as early as 5 hr after a single oral administration of 1000 or 3000 mg/kg. These changes were characterized by condensation, atrophy, and deformation of the nuclei of chondrocytes distributed in the middle zone. In such nuclei, aggregation of heterochromatin was observed. Degenerated cells with vacuolated and partially disintegrated cytoplasms were also seen in this zone. These lesions were followed by edema of the matrix accompanied with markedly decreased stainability with safranin-O, and a cavity was formed later by liquefaction of the cartilage. The changes were reversible, with rebounding occurring even with continued treatment with ofloxacin. The proliferation of chondrocytes around the lesion chiefly contributed to the repair. Ofloxacin had no adverse effects on the articular cartilage in rats when treatment was initiated at 8 weeks of age or later.

Animals↗

PubMed2005

Functional outcome of knee articular cartilage repair in adolescent athletes.

BACKGROUND: Limited information exists about the treatment of full-thickness articular cartilage lesions of the knee in adolescent athletes. PURPOSE: To evaluate the functional outcome and athletic activity after articular cartilage repair in the knees of adolescent athletes. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Twenty adolescent athletes with full-thickness articular cartilage lesions of the knee were treated with autologous chondrocyte transplantation. Functional outcome was evaluated by subjective patient outcome rating, knee activity scores, and level of athletic participation. RESULTS: At a mean of 47 months after autologous chondrocyte transplantation, 96% of adolescents reported good or excellent results with significant increases in postoperative Tegner activity scores and Lysholm scores. Ninety-six percent returned to high-impact sports and 60% to an athletic level equal or higher than that before knee injury. Return to preinjury sports correlated with shorter preoperative symptoms and a lower number of prior operations. All adolescents with preoperative symptoms < or =12 months returned to preinjury-level athletics, compared to 33% with preoperative intervals longer than 12 months. CONCLUSION: Treatment of full-thickness articular injuries of the knee in adolescent athletes with autologous chondrocyte transplantation yields a high rate of functional success at a mean follow-up of 47 months. The rate of return to demanding athletic activities is higher in cases in which the preoperative duration of symptoms is 12 months or less.

Adolescent↗

PubMed1988

Electron probe X-ray microanalysis of the composition of hyaline articular and non-articular cartilage in young and aged rats.

Blocks of articular cartilage were taken from tibiae of young adult (8 week) and aged adult (50-60 week) rats; xiphisternal cartilage was obtained from young adult rats. Specimens were quench-frozen in nitrogen slush, freeze-fractured and examined by low-temperature scanning electron microscopy. The results of X-ray microanalysis of frozen-hydrated bulk cartilage are semi-quantitative. The composition of chondrocyte nuclei and cytoplasm are only marginally different. Xiphisternal chondrocytes contain lipid inclusions which show an absence of element peaks and are designated as being neutral lipid. Intra- and extracellular Na, P, S, Cl, K and Ca count rates are significantly different. Cartilage from older rats contains more S and Ca, and less K and Cl in the intercellular matrix than that from young rats. Intracellular K levels are lower in aged than in young rats. The intercellular matrix of xiphisternal cartilage contains larger amounts of S, Na and K, and a smaller amount of Cl compared to that of tibial articular cartilage.

Aging↗

PubMed1988

Quantitation of structural features characterizing weight- and less-weight-bearing regions in articular cartilage: a stereological analysis of medial femoral condyles in young adult rabbits.

The structural organization of articular cartilage from the medial femoral condyle of young adult rabbits has been examined after processing according to an improved fixation procedure. By using recently developed stereological methods, a quantitative analysis of chondrocyte number, surface area, volume, and matrix volume per cell was carried out in the light microscope; at the electron microscopic level, quantities of cytoplasmic components within chondrocytes (including organelles) were estimated. These measurements were made for each of the four zones from the (articular cartilage) surface down to the tidemark, and the results (for each zone) were compared between weight- and less-weight-bearing regions. In general, articular cartilage revealed considerable heterogeneity in structure throughout its depth. The number of cells per unit volume is maximal beneath the surface and decreases toward the tidemark. The size of chondrocytes, and the mean matrix volume surrounding each, increases from the surface toward the deeper zones. Comparison between weight- and less-weight-bearing regions reveals striking differences. The numerical volume density of cells in the superficial zone of regions bearing high physiological load is less than half of that in less-weight-bearing regions, chondrocyte death being principally responsible for this reduction. A comparison between the midzones of weight- and less-weight-bearing areas reveals that the former is characterized by a decrease in cell density and an approximately threefold increase in cell size in relation to the latter. The increase in cell volume is attributable principally to an accumulation of intermediate filaments and glycogen particles, and represents an adaptation to increased functional requirements. Near the tidemark, numerical volume densities of chondrocytes in both weight- and less-weight-bearing locations are similar, but the larger cell size in the former still persists.

Animals↗

PubMed1991

[Proteolytic enzymes and the destruction of articular cartilage in arthritis and chronic polyarthritis].

The extracellular matrix (ECM) of articular cartilage is subject to a steady remodelling process. The collagenous components of the ECM are characterized by a very low rate of metabolism, whereas the proteoglycans exhibit an active turnover. The main proteolytic enzymes degrading the ECM components are collagenase, gelatinase and stromelysin. These enzymes undergo under pathological circumstances a remarkable enhancement of synthesis and activity. Although each of these enzymes appears to degrade one ECM component specifically, there is evidence for synergistic effects of most of them. Gelatinase acts synergistically with collagenase in degrading insoluble interstitial collagens and stromelysin activates collagenase. Thus a cascade mechanism may exist in which the cartilage-ECM is completely degraded. Yet, it is not crucial which part of the ECM (collagens or proteoglycans) is primarily degraded. The integrity of the ECM rather depends on the balance between anabolic and catabolic processes, the upset of which results in damage of the articular cartilage. Cartilage destruction in rheumatoid arthritis and osteoarthritis is considered to be a result of this imbalance in favour of the catabolic processes. This would lead to a decrease in proteoglycans which causes fibronectin deposition in the cartilage ECM. Due to chemotaxic effects of fibronectin on fibroblasts, the enrichment of this glycoprotein in the ECM gives rise to cartilage fibrosis and early degeneration.

Arthritis, Rheumatoid↗

PubMed1998

COMP (cartilage oligomeric matrix protein) is synthesized in ligament, tendon, meniscus, and articular cartilage.

The presence of cartilage oligomeric matrix protein (COMP) in extracts of ligament, tendon, meniscus, and canine articular cartilage was demonstrated by Western blot analysis using anti-dog COMP antibody. When the tissues were cultured in the presence of [35-S]methionine/cysteine, metabolically labeled COMP was purified from the culture media and from tissue extracts by DEAE-cellulose gel chromatography. SDS-Polyacrylamide gel electrophoresis (SDS-PAGE) followed by autoradiography and immunoblotting under reducing and non-reducing conditions revealed that COMP is synthesized by the cells of these connective tissues. Increased levels of COMP in samples of both synovial fluid and serum of patients with various joint diseases may not only be derived from cartilage but also from ligaments and tendons. COMP is not a highly tissue-specific cartilage molecule.

Animals↗