Thickness of human articular cartilage in joints of the lower limb.
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OBJECTIVES: (a) To determine the topographical variations in cartilage thickness over the entire surfaces of cadaveric lower limb joints, and (b) to examine the correlations between: cartilage thickness and its site specific modulus; cartilage thickness and donor age, weight, height, and body mass index. METHODS: The cartilage thickness of 11 sets of cadaveric human joints each comprising an ankle, knee, and hip was measured using a needle probe technique. Statistical analysis was used to compare the cartilage thickness of the different lower limb joints and the differences in cartilage thickness over the surface of individual joints. It was further examined whether cartilage had a correlation with its stiffness, and any of the details of the specimen donors such as age, weight, height, and body mass index. RESULTS: The mean cartilage thickness of the knee was significantly greater than that of the ankle and hip (p < 0.001) in all 11 sets of joints, while the cartilage thickness of the hip was significantly greater than that of the ankle in 10 sets of joints (p < 0.001). The mass of specimen donors was found to correlate with the mean cartilage thickness of all three lower limb joints. A correlation was also found between the height of donors and the mean cartilage thickness of the knee and hip joints, while only in the ankle joint was a correlation found between the mean cartilage thickness and the body mass index of the specimen donors. A further correlation was found between cartilage thickness and its modulus; the thinner the cartilage, the higher the modulus. CONCLUSIONS: The thickness of articular cartilage seems to be related to the congruance of a joint; thin cartilage is found in congruent joints such as the ankle, whereas thick cartilage is found in incongruent joints such as the knee. The correlations in this study imply that the larger and heavier was a donor the thicker was the cartilage in the lower limb joints. The data further suggest the presence of an inverse relation between the mean cartilage thickness and mean compressive modulus in each of the joints examined. (+info)
Material properties and biosynthetic activity of articular cartilage from the bovine carpo-metacarpal joint.
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OBJECTIVE: To determine the site variation of material properties and cellular biosynthetic activity, and to compare these at each site, of articular cartilage from the bovine carpo-metacarpal joint in order to test its usefulness as a model system for investigating the metabolic effects of mechanical stimuli. DESIGN: The mechanical properties and composition of full-depth biopsies of articular cartilage were measured at defined sites in bovine carpometacarpal joints. Metabolic activity at the same sites was assessed by incubating further biopsies in medium containing 35S-sulfate and 3H-leucine then measuring the incorporated radioisotope and cell density. These results were compared with an estimate of the distribution of forces across the joint. RESULTS: Topographical variation of water content, stiffness, cell count or incorporated radioisotope was not significant whereas collagen and glycosaminoglycan varied in different ways. A moderate correlation was found between water and collagen contents, but the correlation between water and glycosaminoglycan contents was poor. Neither compressive stiffness nor creep compliance was predicted strongly by any of the composition measurements. A negative correlation was found between metabolic activity and cell density. CONCLUSIONS: Defining the variation of tissue properties across the bovine carpometacarpal joint and the lack of variation in biosynthetic activity will enable proper matching of experimental and control groups of biopsies in studies of the effects of mechanical stimuli on the composition and mechanical properties of articular cartilage. In addition, the lack of correlation between stiffness, water and glycosaminoglycan contents is further evidence that the mechanical properties of the tissue depend significantly on factors other than these broad measures of composition. (+info)
Maturation-related compressive properties of rabbit knee articular cartilage and volume fraction of subchondral tissue.
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OBJECTIVE: Knowledge about the physiologic change in cartilage biomechanics, accompanying the structural remodeling of the cartilage bone unit during maturation, may have relevance to understand the development of joint disease. The purpose of this study was to investigate maturation-dependent changes of compressive properties of articular cartilage and volume fraction of subchondral tissue in healthy rabbit knees. METHODS: Cartilage compressive properties (instantaneous and creep moduli) were tested at seven defined knee joint regions of five young (ten weeks), five adolescent (eighteen weeks) and five adult (above thirty-one weeks) healthy rabbits with in-situ indentation tests. Morphometric analysis of volume fraction of subchondral tissue was carried out at four regions. RESULTS: Cartilage stiffness (instantaneous modulus) decreased between infancy and adolescence (P < 0.009), and stayed then the same. A simultaneous significant change in (50-second) creep modulus was only observed at one region, but both moduli correlated to each other. Subchondral tissue consisted of cancellous bone in the young, and formed a more solid bone plate not before adolescence. Its volume fraction increased from infancy to adolescence (P < 0.001), but stayed then the same. There was a significant inverse correlation between the volume fraction of subchondral tissue and cartilage stiffness at the four measured regions (R2 = -0.59). The arrangement of collagen fiber bundles in the deeper cartilage layers changed from a mesh-like structure in the young to a more perpendicular alignment in the adolescent and adult. CONCLUSION: The maturation-related change in compressive properties coincided with a conspicuous change in volume fraction of the subchondral tissue. The main change appeared around puberty. (+info)
Proteoglycan turnover during development of spontaneous osteoarthrosis in guinea pigs.
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OBJECTIVE: The study was performed to clarify the metabolic background of the variations in proteoglycan concentrations, relating to ageing and the spontaneous development of osteoarthrosis in guinea pigs. METHODS: Six-, 9- and 12-month-old Hartley guinea pigs were injected intraperitoneally with Na2(35)SO4. The incorporation and degradation of various proteoglycans were analyzed in different areas of tibial articular cartilage during the development of osteoarthrosis. RESULTS: Proteoglycan synthesis was most active in the uncalcified cartilage of 6-month animals and highest in the medial compartment with its presumably higher load. The breakdown of proteoglycans decreased with age. The onset of osteoarthrosis was associated with decreased synthesis of large and small proteoglycans, while the rate of degradation remained unchanged. CONCLUSION: During onset of osteoarthrosis the synthesis of large proteoglycans gradually becomes insufficient to compensate for the simultaneous degradation. This differs from findings in more rapidly progressing, experimental secondary osteoarthrosis, where a substantial increase in the rate of degradation is more conspicuous. (+info)
Collagen type I antisense and collagen type IIA messenger RNA is expressed in adult murine articular cartilage.
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OBJECTIVE: Articular cartilage has only limited capacities for repair and it is not known what is the exact mechanism of matrix restoration. It was investigated whether the reparative process in murine articular cartilage after moderate proteoglycan depletion is accompanied by a change in the chondrocyte phenotype either to hypertrophy or to a less differentiated phenotype as assayed by the expression of specific collagen subtypes. DESIGN: Moderate proteoglycan depletion was induced by injection of papain whereafter the expression of collagen type I mRNA, collagen IIA and IIB mRNA and type X collagen mRNA in patellar cartilage, as markers for chondrocyte phenotype, was investigated by RT-PCR during normal cartilage physiology and matrix restoration. In addition, in-situ expression of collagen subtypes was assayed by immunolocalisation. RESULTS: In normal articular cartilage collagen I, collagen IIB and collagen type X transcripts were easily detected. Surprisingly, collagen type I sense as well as antisense mRNA was detected and in addition to IIB transcripts collagen IIA transcripts were detected in a number of samples. During cartilage matrix restoration no change in the expression of collagen I, collagen IIA or IIB or collagen type X mRNA transcripts could be detected. Immunolocalization demonstrated the presence of type I (pericellular) and type II collagen in the extracellular matrix. The pericellular matrix of hypertrophic chondrocytes showed collagen type X staining in the calcified cartilage in normal and papain-injected knee joints. Increased staining for collagen type X was found in the upper cartilage layer in the interterritorial matrix from day 7 after papain injection. CONCLUSION: The absence of changes in collagen mRNA expression indicates that alteration of chondrocyte phenotype does not occur during the successful repair process after moderate proteoglycan depletion. Collagen type X appears to be deposited in the upper cartilage layer during this process. (+info)
Stimulation of proteoglycan production by glucosamine sulfate in chondrocytes isolated from human osteoarthritic articular cartilage in vitro.
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OBJECTIVE: This study investigated the in-vitro effects of a crystalline glucosamine sulfate (GS) preparation on DNA synthesis and on proteoglycan (PG) and type II collagen (coll II) production by human articular chondrocytes isolated from human osteoarthritic articular cartilage in a 3-dimensional culture system for 4, 8, and 12 days. MATERIALS AND METHODS: Human articular chondrocytes from osteoarthritic femoral heads were isolated from their matrix by collagenase digestion and then cultured in suspension. Under constant agitation, cells aggregated and formed a cluster within a few days. The effects of GS (1-100 micrograms/ml) on chondrocytes were determined by quantifying DNA synthesis (by measurement of [3H]-thymidine uptake) as well as PG and coll II production using radiommunoassays (RIAs) specific for coll II and to human human cartilage PG. Cross-reaction with GS in the RIAs was not detected. Moreover, PG size distribution was determined by exclusion chromatography under associative conditions to determine the association of PG monomers with hyaluronic acid (HA) to form large molecular weight PG aggregates. RESULTS: Under the above conditions, PG production in culture media and chondrocyte clusters was increased by GS (10-100 micrograms/ml). DNA synthesis and coll II production were not modified by GS. In addition, GS did not modify the physico-chemical form of PG produced by cells during culture. CONCLUSIONS: Glucosamine sulfate did not affect DNA synthesis nor coll II production but caused a statistically significant stimulation of PG production by chondrocytes from human osteoarthritic cartilage cultured for up to 12 days in 3-dimensional cultures. (+info)
Joint anatomy, design, and arthroses: insights of the Utah paradigm.
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This model of joint design argues 1) that excessive fatigue damage (MDx) in articular cartilage collagen can be the "final cause" of an arthrosis; 2) that known responses of a growing joint's anatomy and geometry, and modeling and maintenance activities, to mechanical loads minimize that cause and thus arthroses; 3) and many biomechanical, biochemical, cell-biologic, genetic and traumatic "first causes" of arthroses could lead to that final cause. The model depends partly on the following facts (marked by a single asterisk) and ideas (marked by a double asterisk). A) During growth a joint's total loads can increase over 20 times without causing an arthrosis, yet in adults an equal loading increase would cause one. B) Fatigue damage (MDx) occurs in joint tissues, larger strains increase it, and minimizing strains reduces it. C) Bone can repair amounts of MDx below an "MDx threshold," but larger amounts can escape repair and accumulate. The model assumes articular cartilage has similar features. D) Bone modeling makes bones strong enough to keep their strains below bone's MDx threshold and minimize MDx. Chondral modeling shapes and sizes joints during growth; that would keep articular cartilage strains below the chondral MDx threshold to minimize chondral MDx and arthroses. Normal chondral modeling nearly stops in adults, which might explain point A above. E) Throughout life maintenance activities preserve optimal physical, chemical and biologic properties of a joint's tissues. To past emphases on the biochemical, genetic, cellular and molecular biologic features of adult joint physiology, this model adds organ-level, tissue-level and vital-biomechanical features of growing joints that invite study and understanding at lower levels of biologic organization. (+info)
Validity of histopathological grading of articular cartilage from osteoarthritic knee joints.
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OBJECTIVES: To determine the validity of the histological-histochemical grading system (HHGS) for osteoarthritic (OA) articular cartilage. METHODS: Human articular cartilage was obtained from macroscopically normal (n = 13) and OA (n = 21) knee joints. Sections of central and peripheral regions of normal samples were produced. Sections of regions containing severe, moderate, and mild OA changes were produced from each OA sample. A total of 89 sections were graded by means of the HHGS (0-14) twice by three observers. RESULTS: Average scores for regions designated severe (8.64) and moderate (5.83) OA were less than the expected (10-14 and 6-9, respectively) according to the HHGS, whereas average scores for the region designated mild (5.29) OA and central and peripheral regions (2.19) of normal cartilage were higher than expected (2-5 and 0-1, respectively). The HHGS was capable of differentiating between articular cartilage from macroscopically normal and OA joints and between the region designated severe OA and other regions. However, the HHGS did not adequately differentiate between regions designated mild and moderate OA. Values for sensitivity, specificity, and efficiency for all regions varied considerably. CONCLUSION: The HHGS is valid for normal and severe OA cartilage, but does not permit distinction between mild and moderate OA changes in articular cartilage. (+info)