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PubMed2003

A growth mixture theory for cartilage with application to growth-related experiments on cartilage explants.

In this paper, we present a growth mixture model for cartilage. The main features of this model are illustrated in a simple equilibrium boundary-value problem that is chosen to illustrate how a mechanical theory of cartilage growth may be applied to growth-related experiments on cartilage explants. The cartilage growth mixture model describes the independent growth of the proteoglycan and collagen constituents due to volumetric mass deposition, which leads to the remodeling of the composition and the mechanical properties of the solid matrix. The model developed here also describes how the material constants of the collagen constituent depend on a scalar parameter that may change over time (e.g., crosslink density); this leads to a remodeling of the structural and mechanical properties of the collagen constituent. The equilibrium boundary-value problem that describes the changes observed in cartilage explants harvested at different stages of a growth or a degenerative process is formulated. This boundary-value problem is solved using existing experimental data for developing bovine cartilage explants harvested at three developmental stages. The solution of the boundary-value problem in conjunction with existing experimental data suggest the types of experimental studies that need to be conducted in the future to determine model parameters and to further refine the model.

Aging↗
PubMed1976

Metalloproteases of human articular cartilage that digest cartilage proteoglycan at neutral and acid pH.

Extracts of human articular cartilage contain proteases capable of degrading the proteoglycan component of cartilage matrix at neutral and acid pH. These enzymes have been partially purified by ion exchange chromotography and characterized by disc electrophoresis, inhibition patterns, and action of proteoglycan. Three distinct metalloproteases are described. A neutral protease that digests proteoglycan subunit optimally at pH 7.25 has been purified up to 900-fold. It is strongly inhibited by o-phenanthroline, alpha-2-macroglobulin, and egg white, and to a lesser extent by D-penicillamine and EDTA. Inhibition by chelating agents is reversed by cobalt, zinc, and ferrous ions. Two acid metalloproteases, distinct from cathespins B1, D, and F, digest proteoglycan subunit at pH 4.5 and 5.5. Both are inhibited by o-phenanthroline and activity is restored by cobalt, zinc, or ferrous ions. With electron microscopy, it was found that cartilage slices were depleted of ruthenium red-staining matrix proteoglycan after incubation in vitro with a partially purified cartilage extract at neutral pH. Sedimentation, gel chromatography, sodium dodecyl sulfate-gel electrophoresis, and immuno-diffusion studies of digests of isolated proteoglycan fraction produced by the partially purified cartilage extract at neutral and acid pH confirmed that the cartilage enzymes act only on the protein component of proteoglycan subunit, producing fragments with 5 to 12 chondroitin sulfate chains. The link proteins were not digested.

Cartilage, Articular↗
PubMed1999

Expression of anchorin CII (cartilage annexin V) in human young, normal adult, and osteoarthritic cartilage.

In its tissue-specific function as a collagen receptor of chondrocytes, cartilage annexin V (anchorin CII) occupies a key position in the organization of the cell-extracellular matrix (ECM) junction for the tissue. The general role of annexin V (Anx V) in other tissues suggests involvement in cellular secretory processes and in regulation of apoptosis. Immunohistochemical analysis of Anx V in growth plate cartilage, confirmed by in situ hybridization, suggests that Anx V is prominently expressed and forms a major constituent of growth plate chondrocytes. Anx V epitopes are also located in the pericellular matrix of hypertrophic cartilage. In adult articular cartilage the expression is downregulated, with the highest levels of immunostaining found in the upper third of the articular cartilage layers and almost no antigen found in the deep layers. Osteoarthritic (OA) cartilage is characterized by a significant upregulation of message and protein throughout the entire depth of the tissue, an accumulation of cytoplasmic annexin V epitopes, and a release of epitopes into the pericellular and interterritorial matrix, in part co-localized with granular structures. Therefore, Anx V expression and tissue distribution may serve as a histological marker for metabolic alterations and for changes in the cellular phenotype associated with OA.

Adult↗
PubMed1995

Osteochondrosis of the articular-epiphyseal cartilage complex in young horses: evidence for a defect in cartilage canal blood supply.

The objectives of this study were to determine in horses 1) the ages at which viable cartilage canal vessels are present in the articular-epiphyseal cartilage complex of three predilection sites and one nonpredilection site of osteochondrosis (OC), 2) the prevalence of lesions of OC in these sites, and 3) whether there was an association of lesions of OC with necrotic cartilage canal blood vessels. The medial femoral condyle, lateral femoral trochlear ridge, and distal ends of the tibia and proximal phalanx were examined grossly, microradiographically, and histologically in 35 horses 18 months old or younger. Cartilage canals containing patent blood vessels were present in all sites examined in foals less than 3 weeks old and were absent from all sites by 7 months of age. The overall prevalence of lesions of OC at one or more of the sites examined was 12/35 (34%). Prevalence increased to 11/22 (50%) in horses 2 months old and older. These lesions occurred primarily in the medial condyle of the femur (n = 5) and the intermediate ridge of the distal tibia (n = 5). All lesions seen in horses between 3 weeks and 5 months of age were associated with necrotic cartilage canal blood vessels. In horses 7 months of age and older, lesions of OC were considered chronic because of extensive involvement of the subchondral bone and bone marrow. These results suggest that OC lesions develop prior to 7 months of age and that ischemic necrosis of cartilage secondary to a defect in vascular supply is an important factor in the pathogenesis of this disease in horses.

Aging↗
PubMedDate not supplied

Differences in cartilage formed intramuscularly or in joint surface defects by syngeneic rat chondrocytes isolated from the articular-epiphyseal cartilage complex.

Syngeneic rat chondrocytes isolated from the articular-epiphyseal cartilage complex were suspended in hyaluronic acid and transplanted intramuscularly or into joint surface defects. Transplants were fixed in ruthenium hexammonium trichloride and embedded in glycol methacrylate. In cartilage nodules produced intramuscularly, chondrocyte hypertrophy and matrix calcification were observed after 2 wk. Partial ossification occurred after 4 wk and the cartilage was almost completely replaced by an ossicle after 8 wk. Only small, dispersed groups of chondrocytes remained within the ossicle. In cartilage formed in joint surface defects a superficial and a deep zone were distinguished. Chondrocytes in the superficial zone did not hypertrophy and cartilage remained unossified. In the deep zone matrix calcification and bone formation occurred. These processes were, however, retarded in comparison with intramuscular transplants. Thus, either intraarticular environment exerted an inhibitory effect on chondrocyte hypertrophy and matrix calcification or articular chondrocytes present among transplanted cells accumulated close to the joint lumen and reconstructed normal articular cartilage.

Animals↗
PubMed2003

A novel chordin-like BMP inhibitor, CHL2, expressed preferentially in chondrocytes of developing cartilage and osteoarthritic joint cartilage.

We have identified a novel chordin-like protein, CHL2, which is structurally most homologous to CHL/neuralin/ventroptin. When injected into Xenopus embryos, CHL2 RNA induced a secondary axis. Recombinant CHL2 protein interacted directly with BMPs in a competitive manner to prevent binding to the type I BMP receptor ectodomain, and inhibited BMP-dependent induction of alkaline phosphatase in C2C12 cells. Thus, CHL2 behaves as a secreted BMP-binding inhibitor. In situ hybridization revealed that CHL2 expression is restricted to chondrocytes of various developing joint cartilage surfaces and connective tissues in reproductive organs. Adult mesenchymal progenitor cells expressed CHL2, and its levels decreased during chondrogenic differentiation. Addition of CHL2 protein to a chondrogenic culture system reduced cartilage matrix deposition. Consistently, CHL2 transcripts were weakly detected in normal adult joint cartilage. However, CHL2 expression was upregulated in middle zone chondrocytes in osteoarthritic joint cartilage (where hypertrophic markers are induced). CHL2 depressed chondrocyte mineralization when added during the hypertrophic differentiation of cultured hyaline cartilage particles. Thus, CHL2 may play negative roles in the (re)generation and maturation of articular chondrocytes in the hyaline cartilage of both developing and degenerated joints.

Alkaline Phosphatase↗
PubMed1996

Transmission of rapidly applied loads through articular cartilage. Part 2: Cracked cartilage.

A model of articular cartilage suffering rapidly applied loads and containing splits and fissures is presented. The possibility of cracks propagating through the cartilage collagen network is analysed using elastic fracture mechanics. Cracks are modelled using the distributed dislocation technique and the crack tip stress intensity factors are thereby evaluated. The mode I (tensile) stress intensity factors are generally much larger than the mode II (shearing) factors for cracks at the articular surface and close to, and at oblique angles to, the cartilage-bone interface, two regions where cartilage cracks have been observed. This suggests an opening, tensile mode of failure. The mode II factors are larger for cracks running along the interface. The rapidly loaded cracked cartilage model may explain the splits observed in osteoarthrotic cartilage.

Biomechanical Phenomena↗
PubMed2005

SKI306X suppresses cartilage destruction and inhibits the production of matrix metalloproteinase in rabbit joint cartilage explant culture.

SKI306X was previously found to have cartilage protective effects in the experimental osteoarthritis (OA) model. To investigate the chondro-protective benefits of SKI306X for its capacity in altering changes in cartilage metabolism and molecular mechanisms of cartilage protective action, SKI306X is studied in rabbit cartilage explants culture. To investigate the protective effect of SKI306X on cartilage catabolism, we assessed collagen degradation in rabbit cartilage explants treated with interleukin-1alpha up to 3 weeks. To examine the reaction mechanism, matrix metalloproteinase (MMPs) were investigated by fluorimetric and Western blotting analysis. In addition, its effects on the activation process of proenzyme MMP-3 were determined by gelatin zymography. SKI306X significantly inhibited collagen degradation and inhibited the activities of several MMPs. Total MMPs activities in cultured medium were substantially increased in the third week at the time of collagen degradation with the absence of SKI306. However, the introduction of SKI306X decreased MMPs activities in cultured medium. Furthermore, Western blotting analysis proved that these inhibitory effects of this drug were the result of inhibiting MMPs expression. SKI306X also inhibited the activation of proenzyme MMP-3 to the active form of MMP-3. These results indicate that SKI306X inhibits matrix degradation by down regulating MMPs expression and secretion, inhibition of MMPs activity, and inhibiting activation of MMP-3 during the collagen breakdown process.

Animals↗
PubMed2001

Developmental distribution of collagen type XII in cartilage: association with articular cartilage and the growth plate.

Collagen type XII is a member of the fibril-associated collagens and is characterized by a short triple-helical domain with three extended noncollagenous NC3 domains. Previous studies suggested that collagen XII is a component of cartilage but little is known about its spatial-temporal distribution. This study uses a polyclonal antibody to the purified NC3 domain to investigate its developmental distribution in rat forelimb. Collagen XII was present at the joint interzone on embryonic day 16 (E16d) and restricted to the presumptive articular cartilage by E18d. Labeling of the articular surface intensified as development progressed postnatally (day 1 [1d] to 28d) and extended approximately six cell diameters deep. In juvenile rats, collagen XII antibodies also labeled the longitudinal and transverse septa of stacked chondrocytes in the growth plate. However, collagen XII was not associated at any developmental stage with the cartilaginous secondary ossification center and was only weakly expressed in epiphyseal cartilage. Ultrastructural localization of the NC3 domain epitope showed labeling of the surface of collagen II fibrils both in tissue and in isolated fibrils. The results presented provide further evidence that articular cartilage differs substantially from the underlying epiphyseal cartilage and that different chondrocytic developmental fates are reflected in the composition of their extracellular matrix starting early in development. In addition, collagen XII was distributed in areas of cartilage with more organized fibril orientation and may have a role in promoting alignment or stabilizing such an organization, thereby creating a matrix capable of withstanding load-bearing forces.

Animals↗
PubMed1993

Calcified cartilage zone and its dimensional relationship to the articular cartilage in the human temporomandibular joint of elderly individuals.

The aim was to describe the appearance of the calcified cartilage zone (CCZ) and to determine its dimensional relationship to the articular cartilage thickness in the normal human temporomandibular joint. An autopsy material comprising 21 joints from 12 elderly individuals was examined microscopically. The appearance of the CCZ was examined, and the thickness of the CCZ and of the total articular cartilage was measured in 18 different positions in each joint. The CCZ was outlined by a flat or gently undulating tidemark and an irregular osteochondral junction. The cellularity of the CCZ varied extensively. The cells were numerous in the CCZ when the overlying articular cartilage displayed high cellularity. Statistical analysis of the measurements demonstrated a relationship (p < 0.001) between the thickness of the CCZ and of the articular cartilage. Our findings, both qualitative and quantitative, indicate a close relationship between the physiology of the CCZ and of the overlying articular cartilage.

Aged↗
PubMed2001

In vitro expression of cartilage-specific markers by chondrocytes on a biocompatible hydrogel: implications for engineering cartilage tissue.

Natural cartilage tissue has a limited self-regenerative capacity; thus, strategies to replenish the lost cartilage are desired in reconstructive and plastic surgery. Tissue-engineered cartilage using biodegradable polymeric scaffolds is one such approach gaining wide attention. We have earlier demonstrated the biocompatible nature and ability of chitosan-gelatin hydrogel to maintain differentiated populations of respiratory epithelial cells. The aim of the present study was to evaluate its suitability as a substratum for inducing chondrocyte growth and differentiation. Electron microscopic (SEM) analysis of freeze-dried hydrogels showed a highly porous morphology with interconnections as seen in cross section. Chondrocytes were observed to attach and exhibited a differentiated phenotype with proper cell-cell contact on three-dimensional freeze-dried hydrogels. When cultured on two-dimensional hydrogel films they showed higher growth rates (4-6%) compared with a polystyrene (TCPS) control until 6 days (p > 0.05), which slowed down after 10 days. Immunofluorescent microscopic studies revealed that chondrocytes on hydrogel films exhibited comparable expression of beta1 integrin (CD29) to TCPS controls, indicating the ability of the hydrogel substrate to maintain normal expression of beta1 integrin. RT-PCR analysis of chondrocytes grown on hydrogel films showed that chondrocytes express the mRNA for extracellular matrix proteins such as collagen type IIalpha1 (COL IIalpha1), COL III, COL IXalpha3. Expression of COL I was less prominent than COL II as indication of differentiation. Expression of COL X could not be detected, suggesting an absence of chondrocyte hypertrophy. Chondrocytes also showed weak mRNA expression of aggrecan, a cartilage-specific proteoglycan. All of these results point out the ability of the chitosan-gelatin hydrogel to induce the expression of mRNAs for cartilage-specific extracellular matrix proteins by nasal septal chondrocytes. This hydrogel needs to be further evaluated for its ability to support chondrocyte-specific marker expression to explore the possibility of forming a tissue resembling natural cartilage in vitro.

Aggrecans↗
PubMedDate not supplied

Diacerein reduces the level of cartilage chondrocyte DNA fragmentation and death in experimental dog osteoarthritic cartilage at the same time that it inhibits caspase-3 and inducible nitric oxide synthase.

OBJECTIVE: The primary objective of this study was to evaluate the ex vivo therapeutic efficacy of diacerein and its active metabolite, rhein, on osteoarthritic (OA) cartilage chondrocyte DNA fragmentation and death in the experimental canine model of OA. The study also aimed to explore the effect of the drug on the level of important factors involved in this phenomenon, i.e., caspase-3 and inducible nitric oxide synthase (iNOS). METHODS: OA knee cartilage was obtained from dogs that had received surgical sectioning of the anterior cruciate ligament (ACL) and were sacrificed 12 weeks after surgery. Cartilage explants were cultured in the presence or absence of therapeutic concentrations of diacerein (20 micrograms/ml) or rhein (20 micrograms/ml). Cartilage specimens were stained for TUNEL reaction and immunostained using specific antibodies for active caspase-3 and iNOS. Morphometric analyses were also performed. RESULTS: In OA cartilage specimens, a large number of chondrocytes in the superficial layers stained positive for TUNEL reaction. Treatment with therapeutic concentrations of diacerein (20 micrograms/ml) or rhein (20 micrograms/ml) significantly reduced the level of chondrocyte DNA fragmentation to about the same extent in both treatment groups (P < 0.006, P < 0.002, respectively). The levels of caspase-3 and iNOS in cartilage explants were also significantly decreased (caspase-3, diacerein P < 0.04; caspase-3, rhein P < 0.0003; and iNOS, rhein P < 0.009, respectively) when compared to the control group. CONCLUSIONS: This study shows that diacerein/rhein can effectively reduce the level of OA chondrocyte DNA fragmentation and death under the present experimental conditions. This effect is mediated by a decrease in the level of caspase-3 expression, which could possibly be related in part to the reduced level of iNOS and secondarily to NO production. These findings provide additional new information about the mechanisms of action of diacerein on the progression of OA.

Animals↗
PubMed2005

Prothrombin gene expression in articular cartilage with a putative role in cartilage degeneration secondary to joint immobility.

OBJECTIVE: To test the hypothesis that thrombin is expressed by chondrocytes from human and animal articular cartilage and to monitor its levels of expression during cartilage degeneration induced by joint immobility in a rat model. METHODS: Rat knees were immobilized for periods of 2 or 4 weeks, after which the articular cartilage was harvested, total RNA extracted, and the differential display (ddPCR) protocol applied to identify differentially expressed genes. One differentially expressed fragment showed 100% homology with the prothrombin gene. Results were verified by RT-PCR, Northern and Western blot analysis, and immunohistochemistry in human, rat, and rabbit articular cartilage. RESULTS: In our rat model of cartilage degeneration induced by joint immobilization, increases in the levels of prothrombin mRNA, thrombin protein, and fibrin deposition were observed. Expression of the prothrombin gene by chondrocytes was confirmed by ddPCR (rat), RT-PCR (rat and human), and by Northern blot analysis (rabbit). In addition, thrombin-like immunoreactivity was increased in chondrocytes after a 4 week immobilization period compared with rat knees receiving sham surgery. Thrombin activity was reflected by the presence of fibrin immunoreactivity in operated rat knee joints. CONCLUSION: Articular chondrocytes express the prothrombin gene and its local expression in joints is translated into thrombin protein. Prothrombin expression is increased in response to joint immobility. Our results support generation of thrombin locally in joints and an upregulation of thrombin expression in cartilage degeneration secondary to immobility. These results may provide information on the source of increased thrombin activity in various animal models and in clinical forms of arthritis.

Animals↗
PubMed2006

A comparative study of articular cartilage thickness in the stifle of animal species used in human pre-clinical studies compared to articular cartilage thickness in the human knee.

Histological measurements of the thickness of non-calcified and calcified cartilage, as well as the subchondral bone plate in five locations on the femoral trochlea and medial femoral condyles of species were used in preclinical studies of articular cartilage and compared to those of the human knee. Cadaver specimens were obtained of six human knees, as well as six equine, six goat, six dog, six sheep and six rabbit stifle joints (the animal equivalent of the human knee). Specimens were taken from the lateral trochlear ridge, medial trochlear ridge and medial femoral condyle. After histopathological processing, the thickness of non-calcified and calcified cartilage layers, as well as the subchondral bone plate, was measured. Average articular cartilage thickness over five locations were 2.2-2.5 mm for human, 0.3 mm for rabbit, 0.4-0.5 mm for sheep, 0.6-1.3 mm for dog, 0.7-1.5 mm for goat and 1.5-2 mm for horse. The horse provides the closest approximation to humans in terms of articular cartilage thickness, and this approximation is considered relevant in pre-clinical studies of cartilage healing.

Animals↗
PubMed1990

An 18-kDa glycoprotein from bovine nasal cartilage. Isolation and primary structure of small, cartilage-derived glycoprotein.

A glycosylated protein (small, cartilage-derived glycoprotein, SCGP) of approximately 18 kDa with unknown function has been isolated from dissociative extracts of bovine nasal cartilage and its primary structure determined. The protein has 121 amino acids, giving a calculated protein molecular weight of 13,878, four disulfide bonds, two N-linked oligosaccharides and one O-linked oligosaccharide. In nasal cartilage, this glycoprotein is in molar concentrations equivalent to 1/5-1/2 that of the link protein of cartilage proteoglycan aggregates, and it has also been isolated from bovine articular cartilage and from bovine fetal epiphysis. The N-terminal, glycosylated region of the molecule is relatively rich in arginine, proline, glycine, and threonine. The C-terminal 82 amino acids (which contains all four of the disulfide bonds and none of the carbohydrate) can be found as a discrete entity in cartilage extracts, indicating that the N-terminal domain is readily removed by extracellular proteolytic attack.

Amino Acid Sequence↗
PubMed1977

[The cellularity of fibrillated articular cartilage. A comparative study of age-related and osteoarthrotic cartilage lesions from the human femoral head].

The cellularity of human femoral head cartilage has been studied in age-related and osteoarthrotic fibrillated samples and control intact samples. Age-related fibrillated cartilage shows a marked increase of the cell density which is directly related to the proliferation of cell clusters and to cartilage thinning. In osteoarthrotic cartilage lesions multicellular clusters are less frequent and cell density is decreased. A smooth aspect of the exposed cartilage surface and an increased subchondral bone mass are only found in osteoar/hrotic samples. The findings suggest that age-related and osteoarthrotic cartilage lesions are due to different mechanical stresses governing the cellularity of the tissue.

Aging↗
PubMed1988

Heterogeneity of the cartilage-marrow interface during uncalcified cartilage resorption in the chick embryo tibia.

The morphology of the cartilage-marrow interface in chick embryo tibiae has been studied from Day 11 to Day 14. The cartilage-marrow interface did not present a uniform aspect and three different areas could be defined. Most of the interface was lined by fibroblast-like cells, macrophage-like cells and multinucleate giant cells. Other areas were characterised by a paucity of cells and by the presence of much cell debris. In focal areas the cartilage surface was excavated and covered by several layers of closely packed cells. These cells presented longitudinal axes perpendicular to the cartilage surface and were characterised ultrastructurally by the presence of large amounts of rough endoplasmic reticulum and large cytoplasmic processes extending into the matrix. The presence of different cell associations along the cartilage-marrow interface seems to suggest that uncalcified cartilage resorption follows a phasic pattern.

Animals↗
PubMed1985

Ultrastructure of normal epiphyseal cartilage of the articular-epiphyseal cartilage complex in growing swine.

Normal epiphyseal cartilage from the articular-epiphyseal cartilage complex (A-E complex) of the distal parts of the femur and humerus of growing commercial crossbred boars was collected, embedded in plastic, and studied by light and electron microscopies. The morphology of this cartilage was determined to provide a basis for comparison with cartilage affected with osteochondrosis, an important clinical disease in swine. Normal epiphyseal cartilage from the A-E complex in growing swine was divided into 4 major regions of cells: resting, proliferating, hypertrophic, and calcifying regions. Cells in the resting zone contained prominent lipid and densely aggregated glycogen. As the cells proliferated and matured, the lipid and glycogen became less prominent. The lipid droplets became smaller and scarcer, and the glycogen became dispersed in the cytoplasm. Proliferating and hypertrophic cells clustered in roughly egg-shaped groups of 4 to 8 cells/plane of section. In the calcifying region, the interterritorial matrix (between cell clusters) calcified, and the territorial matrix (uniting cells in a cluster) remained uncalcified. Calcified matrix extended the depth of one cell group from the area of capillary penetration, and the capillaries invaded by entering a cluster of cells. Territorial matrices in all regions of A-E complex epiphyseal cartilage were composed of randomly oriented collagen fibrils with a granular fibrillar proteoglycan network dispersed between the fibrils. Heterogeneity of chondrocytes was characterized by the presence of both light- and dark-staining cells in the proliferating through calcifying regions and by 3 morphologically distinct light cell types in the late hypertrophic and calcifying regions.

Aging↗