[Antigenic properties of the articular cartilage].
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Antigens↗
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[The structure of normal and pathologic articular cartilage].
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Cartilage↗
Functional thickness variations of human articular cartilage.
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Cartilage↗
[Biological and structural characteristics of human articular cartilage].
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Cartilage↗
The effects of bupivacaine and neostigmine on articular cartilage and synovium in the rabbit knee joint.
We investigated the effects of intra-articular injections of bupivacaine and neostigmine on articular cartilage and the synovial membrane of rabbit knee joints. Saline, bupivacaine or neostigmine were each administered intra-articularly into 15 knee joints. Five joints per drug treatment were prepared for histopathological examination 24 h, 48 h and 10 days after injection. A pathologist examined the histological samples for inflammation of the articular cartilage, inflammatory cell infiltration, hypertrophy and hyperplasia of the synovial membrane, in a blinded manner. There no histopathological in the saline-treated control joints. Joints treated with bupivacaine and neostigmine showed significantly more histopathological changes than control joints. Joints treated with neostigmine showed significantly more histopathological changes than those treated with bupivacaine, except for articular cartilage inflammation on day 10. We conclude that intra-articular bupivacaine and neostigmine cause histopathological changes in rabbit knee joints, with neostigmine having a greater effect than bupivacaine.
Anesthetics, Local↗
The effect of serum on biosynthesis of proteoglycans by bovine articular cartilage in culture.
Proteoglycan synthesis by slices of adult bovine articular cartilage is stimulated two-to threefold when tissue is cultured in the presence of fetal calf serum for 5-6 days. After this, essentially steady-state conditions are achieved for up to 14 days in which the high synthetic rates are maintained and the amount of proteoglycan in the tissue remains nearly constant. In the absence of fetal calf serum, synthesis declines to a lower level and there is a gradual, net loss of proteoglycan from the tissue. Tissue maintained without serum for several days rapidly increases synthetic rates to the higher levels over 2-3 days after transferring into medium with serum, and vice versa, indicating that the response of the chondrocytes to serum factors is reversible. The structures of the proteoglycans synthesized under all medium conditions were typical for cartilage. Only small differences in glycosaminoglycan chain sizes and a consistent decrease in the relative amount of keratan sulfate to chondroitin sulfate during the first days in the culture were observed. The net capacity of the cells for chondroitin sulfate synthesis, as estimated by incubation in the presence of exogenous beta-xyloside acceptor, increased (or decreased) in parallel with the changes in endogenous proteoglycan synthesis when cultures were transferred from medium without to medium with serum (or vice versa), suggesting that changes in the net amounts of the enzymes for chondroitin sulfate synthesis are closely coordinated with changes in the amount of core protein being processed to proteoglycans. The responses of calf articular cartilage in the same system were somewhat different. Serum in the medium was required to maintain initial high levels of synthesis. The proteoglycans synthesized contained a lower proportion of keratan sulfate than those initially synthesized in the adult tissue, and there was no change in this proportion with time in culture. The maintenance of steady-state conditions for proteoglycan metabolism by either adult or calf tissue in the presence of serum in these cultures should provide a useful model for studying the regulation of synthesis and catabolism of proteoglycans by chondrocytes residing in a nearly normal extracellular matrix for long periods of time.
Animals↗
Effects of cyclic hydrostatic pressure on proteoglycan synthesis in cultured chondrocytes and articular cartilage explants.
Primary chondrocyte cell cultures and explants of bovine articular cartilage were subjected to cyclic hydrostatic pressure in a novel computer-controlled pressure chamber designed for this purpose. The cultures were labeled with 5 microCi/ml 35SO4 and simultaneously pressurized with 5 MPa load for 1.5 or 20 h with pressure cycles of 0.0167, 0.05, 0.25, and 0.5 Hz. The chondrocyte cell cultures were also subjected to 0.0082 and 0.0034 Hz cycles. Sulfate incorporation was significantly inhibited in cell cultures subjected to the 0.5, 0.25, or 0.05 Hz cyclic loads for 1.5 h, but stimulated in explant cultures with a 0.5 Hz cyclic 1.5-h load. Chondrocyte cultures subjected to longer (20 h) loading showed a stimulation of sulfate incorporation with 0.5 and 0.25 Hz cycles, but an inhibition with 0.0167 Hz. The results indicate that cyclic hydrostatic pressures of presumably physiological magnitude have significant influences on proteoglycan synthesis in articular cartilage chondrocytes. Comparison of the cell and explant cultures under identical pressure conditions suggested that chondrocyte interactions with extracellular matrix are involved in this regulation by cyclic hydrostatic pressure. The responses of the chondrocytes to pressurization also varied according to the total length of the treatment, a finding compatible with the idea of multiple metabolic steps in chondrocytes, both pre- and post-translational, controlled by the ambient hydrostatic pressure.
Animals↗
Calcium pentosan polysulfate inhibits the catabolism of aggrecan in articular cartilage explant cultures.
OBJECTIVE: The catabolism of aggrecan and loss of aggrecan fragments from articular cartilage is a key event in the pathogenesis of arthritic diseases such as osteoarthritis. The catabolism of aggrecan is mediated by the specific proteolytic activity termed aggrecanase. The aim of this study was to investigate the effect of the chondroprotective agent calcium pentosan polysulfate (CaPPS) on the aggrecanase-mediated catabolism of aggrecan. METHODS: The catabolism of 35S-labeled aggrecan and loss of tissue glycosaminoglycans (GAGs) were investigated using bovine articular cartilage explant cultures maintained in medium containing varying concentrations of CaPPS (1-100 microg/ml) in the presence or absence of 10(-6)M retinoic acid or 7 ng/ml recombinant human interleukin-1alpha (rHuIL-1alpha). In addition, the effect of CaPPS on the degradation of aggrecan monomers by aggrecanase activity present in conditioned medium from joint capsule explant cultures was investigated. RESULTS: CaPPS inhibited the catabolism of 35S-labeled aggrecan in a dose-dependent manner, particularly when retinoic acid or rHuIL-1alpha was used to stimulate aggrecan catabolism. These effects were reflected in the tissue levels of GAG remaining in these cultures at the end of the experiment. CaPPS inhibited the degradation of aggrecan monomers by soluble aggrecanase activity. CONCLUSION: CaPPS inhibits the catabolism of aggrecan by articular cartilage in a dose-dependent manner, particularly when the processes responsible for aggrecan loss are stimulated. This effect occurs, at least in part, through direct inhibition of aggrecanase activity. CaPPS did not adversely affect overall chondrocyte metabolism, as shown by the incorporation of 35S-sulfate and 3H-leucine into macromolecules and by lactate production in cartilage explant cultures.
Aggrecans↗
Healing of defects in canine articular cartilage: distribution of nonvascular alpha-smooth muscle actin-containing cells.
The objective of this study was to evaluate the types of tissue resulting from spontaneous healing of surgically created defects in adult canine articular cartilage up to 29 weeks postoperatively, with specific attention directed toward the presence and distribution of cells containing the contractile actin isoform, alpha-smooth muscle actin. Two 4-mm diameter defects were made in the trochlear groove to the depth of the tidemark in 20 adult mongrel dogs. The areal percentage of specific tissue types in the reparative material was determined histomorphometrically. Immunohistochemistry was employed to evaluate the percentage of alpha-smooth muscle actin-containing cells. The results showed that approximately 50% of the chondrocytes in the superficial zone of the uninvolved articular cartilage expressed alpha-smooth muscle actin. A significantly lower percentage of alpha-smooth muscle actin-positive chondrocytes appeared in the uninvolved deep zone. Notably, the deep zone adjacent to the defect contained a greater percentage of such cells than in the uninvolved deep zone. Also of interest was that a greater percentage of nonvascular cells in the hyaline cartilage and fibrocartilage of the reparative tissue contained alpha-smooth muscle actin-positive cells, compared to the fibrous tissue in the defects. The findings of this study revealed that canine articular cartilage has some potential for spontaneous regeneration, including integration with the calcified cartilage zone. By 29 weeks, up to 40% of an areal cross section of an untreated full-thickness chondral defect was found to fill with hyaline cartilage, with up to 19% judged histologically similar to articular cartilage. The results warrant further consideration of the role of alpha-smooth muscle actin in chondrocytes in normal articular cartilage and in reparative tissue.
Actins↗
Effects of physical stimulation with electromagnetic field and insulin growth factor-I treatment on proteoglycan synthesis of bovine articular cartilage.
OBJECTIVE: To investigate the single and combined effects of electromagnetic field (EMF) exposure and the insulin growth factor-I (IGF-I) on proteoglycan (PG) synthesis of bovine articular cartilage explants and chondrocytes cultured in monolayers. DESIGN: Bovine articular cartilage explants and chondrocyte monolayers were exposed to EMF (75Hz; 1.5mT) for 24h in the absence and in the presence of both 10% fetal bovine serum (FBS) and IGF-I (1-100ng/ml). PG synthesis was determined by Na(2)-(35)SO(4) incorporation. PG release into culture medium was determined by the dimethylmethylene blue (DMMB) assay. RESULTS: In cartilage explants, EMF significantly increased (35)S-sulfate incorporation both in the absence and in the presence of 10% FBS. Similarly, IGF-I increased (35)S-sulfate incorporation in a dose-dependent manner both in 0% and 10% FBS. At all doses of IGF-I, the combined effects of the two stimuli resulted additive. No effect was observed on medium PG release. Also in chondrocyte monolayers, IGF-I stimulated (35)S-sulfate incorporation in a dose-dependent manner, both in 0% and 10% FBS, however, this was not modified by EMF exposure. CONCLUSIONS: The results of this study show that EMF can act in concert with IGF-I in stimulating PG synthesis in bovine articular cartilage explants. As this effect is not maintained in chondrocyte monolayers, the native cell-matrix interactions in the tissue may be fundamental in driving the EMF effects. These data suggest that in vivo the combination of both EMF and IGF may exert a more chondroprotective effect than either treatment alone on articular cartilage.
Animals↗
[The effect of rupture and reconstruction of posterior cruciate ligament on the degeneration of articular cartilage in rabbit knee].
OBJECTIVE: To investigate the effect of rupture and reconstruction of the posterior cruciate ligament (PCL) on the degeneration of rabbit knee joint. METHODS: Thirty-three mature New Zealand white rabbits were divided into 3 groups. In experiment group I, the PCL of the right knees in 21 rabbits were resected, the contralateral joints as control group, in which only a medial arthrotomy was performed. In experiment group II, the PCL of the right knees in 12 rabbits were immediately reconstructed after PCL were resected. In experiment group I and control group the rabbits were respectively killed 6, 12 and 26 weeks after the operation. In experiment group II the rabbits were respectively killed 12, 26 weeks after the operation. The methods of ink staining, histology, immunohistochemistry and SEM were used to analyze the changes of articular cartilage of the joints. RESULTS: In experiment group I, the knee joints had obvious degeneration of articular cartilage at 26 weeks. The quantitative analysis of the results of the ink staining method showed the degeneration of knee articular cartilage was more serious at 26 weeks than that at 26 weeks in control group. Histological results demonstrated: the large area of fibrosis of cartilage could be seen in the medial condyle at 26 weeks; the fibrosis was deep into the deep layer of cartilage and the number of cells decreased; the average Mankin's score was 7.7. At 26 weeks, type I and III collagen were detected in fibrotic cartilage, while the staining of type II collagen was slight. In experiment group I, the injuries of cartilage in medial condyle could be seen at every stage through SEM, while the surface of cartilage demonstrated disorder in control group through SEM. In experiment group II, only a few specimens had mild injuries of cartilage, the degeneration of cartilage in medial condyle and trochlea were slighter at 26 weeks than that in experiment group I. CONCLUSIONS: PCL rupture can result in articular cartilage degeneration, which develops as time goes on. The degeneration of articular cartilage is more serious in medial compartment and patellofemoral joint than those in other positions. Immediate reconstruction of PCL can effectively prevent articular cartilage degeneration.
Animals↗
In vitro evaluation of the effect of dimethyl sulfoxide on equine articular cartilage matrix metabolism.
OBJECTIVE: To evaluate the effects of dimethyl sulfoxide (DMSO) on equine articular cartilage matrix metabolism. STUDY DESIGN: Using a cartilage explant culture system, proteoglycan (PG) synthesis, PG release, lactate metabolism, chondrocyte viability, and metabolism recovery were determined after cartilage exposure to DMSO. SAMPLE POPULATION: Cartilage harvested from metacarpophalangeal and metatarsophalangeal joints of 12 horses (age range, 1 to 10 years). METHODS: Explants were exposed to concentrations of DMSO (1% to 20%) for variable times (3 to 72 hours). PG synthesis and release were determined by a radiolabel incorporation assay and dimethylmethylene blue (DMMB) dye assay, respectively. Lactate released into culture media was measured, and chondrocyte viability was assessed using the Formizan Conversion Assay and a paravital staining protocol. Metabolism recovery was assessed in explants that were allowed to recover in maintenance media after exposure to DMSO. RESULTS: PG synthesis and lactate metabolism were inhibited in a dose- and time-dependent manner after exposure to DMSO concentrations > or = 5%; there was no significant alteration in PG release. No change in chondrocyte viability was detected after incubation with DMSO. PG synthesis and lactate metabolism returned to baseline rates when allowed a recovery period after exposure to DMSO. CONCLUSIONS: DMSO concentrations > or = 5% suppress equine articular cartilage matrix metabolism. Suppression of PG synthesis and lactate metabolism is reversible and does not appear to be the result of chondrocyte death. CLINICAL RELEVANCE: Equine clinicians adding DMSO to intraarticular lavage solutions should be aware that DMSO may have deleterious effects on equine articular cartilage matrix metabolism.
Analgesics, Non-Narcotic↗
Age-related changes in the antigenicity of human articular cartilage proteoglycans.
Rabbits were immunized with adult or foetal human articular cartilage proteoglycans and cell-mediated and antibody immunity assessed in vitro. Cellular immunity to proteoglycans of different ages was measured by the stimulation of 3H-thymidine incorporation into cultured spleen cells. Antibodies to proteoglycans in the rabbit sera were detected with an enzyme-linked immunosorbent assay. The ability of adult and foetal proteoglycans to preabsorb antibody activity in this assay was compared. The results from both the cellular and antibody studies support the same conclusion, that adult proteoglycans express all foetal antigenic determinants and have additional determinants not seen on foetal proteoglycans. The reactivity of rabbit spleen cells to proteoglycans of different ages indicated that these determinants appear during maturation when the major changes in proteoglycan structure occur. The results did not appear to be due to differences in chondroitin sulphate content of the preparations, since the same observations were made with chondroitinase ABC-digested proteoglycans. The observations might be explained by other differences in glycosylation between the preparations or by postulating the synthesis during maturation of an additional proteoglycan species with a different core-protein. Such changes in the antigenicity of articular cartilage proteoglycans with age could account for the development of autoimmunity to proteoglycans in inflammatory joint diseases and may play a role in their pathogenesis.
Adolescent↗
The effect of retinoic acid on proteoglycan biosynthesis in bovine articular cartilage cultures.
The addition of retinoic acid to adult bovine articular cartilage cultures produces a concentration-dependent decrease in both proteoglycan synthesis and the proteoglycan content of the tissue. Total protein synthesis was not affected by the presence of retinoic acid, indicating that the inhibition of proteoglycan synthesis was not due to cytotoxicity. The proteoglycans synthesized in the presence of retinoic acid were similar in hydrodynamic size, ability to form aggregates with hyaluronate, and glycosaminoglycan composition to those of control cultures. However, the presence of larger glycosaminoglycan chains suggests that the core protein was substituted with fewer but longer glycosaminoglycan chains. In cultures maintained with retinoic acid, a decreased ratio of the large proteoglycan was synthesized relative to the small proteoglycan compared to that measured in control cultures. In cultures maintained with retinoic acid for 1 day and then switched to medium with 20% (v/v) fetal calf serum, the rate of proteoglycan synthesis and hexuronate contents increased within 5 days to levels near those of control cultures. Within 2 days of switching to medium with 20% (v/v) fetal calf serum, the relative proportions of the proteoglycan species were similar to those produced in cultures maintained in medium with 20% (v/v) fetal calf serum throughout. The rate of proteoglycan synthesis by bovine articular cartilage cultures exhibited an exponential decay following exposure to retinoic acid, with estimated half-lives of 11.5 and 5.3 h for tissue previously maintained in medium alone or containing 20% (v/v) fetal calf serum, respectively. The addition of 1 mM benzyl beta-D-xyloside only partially reversed the retinoic acid-mediated inhibition of proteoglycan synthesis. This indicates that the inhibition of proteoglycan synthesis by retinoic acid was due to both a decreased availability of xylosylated core protein and a decreased capacity of the chondrocytes to synthesize chondroitin sulfate chains.
Animals↗
Articular cartilage superficial zone collagen birefringence reduced and cartilage thickness increased before surface fibrillation in experimental osteoarthritis.
OBJECTIVES: To investigate articular cartilage collagen network, thickness of birefringent cartilage zones, and glycosaminoglycan concentration in macroscopically normal looking knee joint cartilage of young beagles subjected to experimental slowly progressive osteoarthritis (OA). METHODS: OA was induced by a tibial 30 degree valgus osteotomy in 15 female beagles at the age of 3 months. Fifteen sisters were controls. Cartilage specimens were collected seven (Group 1) and 18 months (Group 2) postoperatively. Collagen induced optical path difference and cartilage zone thickness measurements were determined from histological sections of articular cartilage with smooth and intact surface by computer assisted quantitative polarised light microscopy. Volume density of cartilage collagen fibrils was determined by image analysis from transmission electron micrographs and content of glycosaminoglycans by quantitative digital densitometry from histological sections. RESULTS: In the superficial zone of the lateral tibial and femoral cartilage, the collagen induced optical path difference (birefringence) decreased by 19 to 71% (p < 0.05) seven months postoperatively. This suggests that severe superficial collagen fibril network deterioration took place, as 18 months postoperatively, macroscopic and microscopic OA was present in many cartilage areas. Thickness of the uncalcified cartilage increased while the superficial zone became thinner in the same sites. In operated dogs, glycosaminoglycan content first increased (Group 1) in the lateral tibial condyle and then decreased (Group 2) (p < 0.05). CONCLUSION: In this OA model, derangement of the superficial zone collagen network was the probable reason for birefringence reduction. This change occurred well before macroscopic OA.
Animals↗
Factors affecting articular cartilage thickness in osteoarthritis and aging.
OBJECTIVE: To test the hypothesis that both aging and osteoarthritis (OA) contribute to the variance of human articular cartilage thickness of the knee and whether these contributions occur predominantly at weight bearing cartilage sites. METHODS: Thin, sagittal magnetic resonance images (MRI) of both knees were examined in 52 patients with idiopathic OA of the knee of short duration (87%: < or = 4 years) and 40 reference subjects of comparable age and sex distribution. Articular cartilage thickness was measured at the weight bearing and nonweight bearing femoral condylar, tibial plateau, and posterior patellar sites. Multiple regression analyses were performed to examine the influence of OA, age, sex, obesity (body mass index), and bone size on cartilage thickness. RESULTS: Age accounted for a significant linear decrease (p < 0.001) in both lateral and medial weight bearing femoral cartilage thickness of both knees, but failed to account for any significant variance in thickness at other cartilage sites. OA accounted for a significant decrease (p < 0.02) in the thickness of the femoral articular cartilage in the medial and lateral right knee compartments and in the lateral left knee compartment, but not in the medial left knee compartment. Significant cartilage thinning could be detected by MRI in patients with OA, even when the joint space was normal radiographically. CONCLUSION: The asymmetric decrease in the left knee may reflect the effect of mechanical factors. Our data show that articular cartilage thickness decreases at the femoral weight bearing sites both with age and as a consequence of OA and that these contributions can be distinguished from one another.
Adult↗
Characterization of mature vs aged rabbit articular cartilage: analysis of cell density, apoptosis-related gene expression and mechanisms controlling chondrocyte apoptosis.
OBJECTIVE: The prevalence of osteoarthritis (OA) is increased in aged individuals and a direct correlation between chondrocyte apoptosis and cartilage degradation secondary to OA has been demonstrated. To address the question of whether age predisposes articular cartilage to apoptosis, the objective of the present study was to characterize and compare in aged and mature non-OA rabbit articular cartilage, cell density and expression levels of specific genes associated with apoptosis. Mechanistic studies on the inhibition of induced apoptosis were also carried out. METHODS: Grade I (non-OA) femoral condyles and tibial plateaus from mature and aged rabbits were taken for assessment of viable cell density (VCD) and mRNA (reverse transcription-polymerase chain reaction) expression levels of the pro-apoptotic genes, Fas, Fas ligand (FasL), caspase-8, inducible nitric oxide synthase (iNOS) and p53. In vitro insulin-like growth factor (IGF-1)-mediated inhibition of nitric oxide (NO)-induced apoptosis was also examined using sodium nitroprusside (SNP) as NO donor. RESULTS: VCD was decreased 50-70% in aged articular cartilage relative to mature cartilage. mRNA expression levels of Fas, FasL, caspase-8 and p53 were higher in aged cartilage than in mature cartilage. iNOS expression was unchanged. IGF-1-mediated inhibition of NO-induced apoptosis was dose-dependent and reversed with addition of phosphatidylinositol-3 kinase inhibitor. CONCLUSIONS: This controlled animal model study demonstrates that age predisposes articular cartilage to changes in VCD and expression levels of specific pro-apoptotic genes. It is significant that these findings were demonstrated on cartilage that showed no prior signs of OA; it is also possible that such changes are a prelude to the age-related development of OA.
Aging↗
Effect of link protein concentration on articular cartilage proteoglycan aggregation.
Previous work has shown that alterations in proteoglycan aggregates are among the first changes detected with aging, disuse, and degeneration of articular cartilage, yet the cause or causes of these alterations remain unknown. To determine if differences in link protein concentration can explain alterations in the assembly, size, and stability of articular cartilage proteoglycan aggregates, we isolated proteoglycan monomer (aggrecan) and link protein from adult bovine articular cartilage and then assembled proteoglycan aggregates from aggrecan and 0.8% hyaluronan relative to aggrecan weight, in the presence of 0, 2, 4, 6, 8, 10, 15, and 20% concentrations of link protein relative to aggrecan weight. We determined the amount, sedimentation coefficient, and stability of the aggregates by analytical ultracentrifugation and measured their dimensions by electron microscopy with use of the monolayer technique. Increased aggregate size, as determined by ultracentrifugation, was directly correlated with an increased number of aggrecans per aggregate and with increased hyaluronan length, as determined by electron microscopy. The concentration of link protein significantly influenced aggregation: concentrations of 6-8% produced maximum aggregation, aggregate stability, and uniformity of aggrecan spacing; concentrations greater than 10% led to the formation of superaggregates (aggregates with sedimentation velocities greater than 100 S that may result from linking two or more hyaluronan filaments) but decreased aggregate stability; and concentrations of less than 4% link protein significantly decreased aggregation, the size and stability of aggregates, and the regularity of aggrecan spacing. The latter observations suggest that a decline in the concentration of link protein could decrease the organization and stability of the articular cartilage matrix.
Aggrecans↗