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PubMed2005

Enhanced repair of articular cartilage defects in vivo by transplanted chondrocytes overexpressing insulin-like growth factor I (IGF-I).

Traumatic articular cartilage lesions have a limited capacity to heal. We tested the hypothesis that overexpression of a human insulin-like growth factor I (IGF-I) cDNA by transplanted articular chondrocytes enhances the repair of full-thickness (osteochondral) cartilage defects in vivo. Lapine articular chondrocytes were transfected with expression plasmid vectors containing the cDNA for the Escherichia coli lacZ gene or the human IGF-I gene and were encapsulated in alginate. The expression patterns of the transgenes in these implants were monitored in vitro for 36 days. Transfected allogeneic chondrocytes in alginate were transplanted into osteochondral defects in the trochlear groove of rabbits. At three and 14 weeks, the quality of articular cartilage repair was evaluated qualitatively and quantitatively. In vitro, IGF-I secretion by implants constructed from IGF-I-transfected chondrocytes and alginate was 123.2+/-22.3 ng/10(7) cells/24 h at day 4 post transfection and remained elevated at day 36, the longest time point evaluated. In vivo, transplantation of IGF-I implants improved articular cartilage repair and accelerated the formation of the subchondral bone at both time points compared to lacZ implants. The data indicate that allogeneic chondrocytes, transfected by a nonviral method and cultured in alginate, are able to secrete biologically relevant amounts of IGF-I over a prolonged period of time in vitro. The data further demonstrate that implantation of these composites into deep articular cartilage defects is sufficient to augment cartilage defect repair in vivo. These results suggest that therapeutic growth factor gene delivery using encapsulated and transplanted genetically modified chondrocytes may be applicable to sites of focal articular cartilage damage.

Alginates↗
PubMed1998

[Pressure devices for NMR microscopy studies of the loading behavior of articular cartilage].

High-resolution MRI offers a unique opportunity to non-invasively image collagen-mediated structures within articular cartilage. Visualization of the stress response of the anisotropic collagenous network in particular, provides more comprehensive knowledge of the biomechanical properties and integrity of articular cartilage, which in turn form a very promising starting point for the present ongoing developments in the noninvasive diagnosis of early stages or arthrosis. The detection of stress-induced changes in the collagenous network, however, requires an MRI probe that permits in vitro measurements under conditions similar to those in the joint, and different orientations relative to the static magnetic field. Here we describe two MR microimaging probes that enable the investigation of the viscoelastic properties of articular cartilage via visualization of the pressure-dependent modifications of anisotropic collagenous structures.

Cartilage, Articular↗
PubMed2003

Growth of immature articular cartilage in vitro: correlated variation in tensile biomechanical and collagen network properties.

Articular cartilage biochemical composition and mechanical properties evolve during in utero and in vivo growth, with marked differences between fetus, newborn, and young adult. The objectives of this study were to test whether in vitro growth of bovine fetal and newborn calf articular cartilage explants resulted in changes in biochemical and tensile properties during up to 6 weeks of free-swelling culture in serum-supplemented medium. During this culture period, both fetal and calf cartilage grew markedly in size, increasing in dry and wet mass by 150-270%. This was due in part to increases in sulfated glycosaminoglycan (+248%), collagen (+96%), and pyridinoline cross-link (+133%). This was accompanied by an increase in water content so that the concentration of matrix components decreased, despite the overall net increase in mass. The ratio of pyridinoline cross-link to collagen remained low and characteristic of immature tissue. The equilibrium and dynamic tensile moduli and strength of both fetal and calf cartilage decreased during the culture period. The biochemical and biomechanical properties of the cartilage explants were correlated, such that the low values of modulus and strength were associated with low concentrations of collagen and pyridinoline. Thus, the tested culture conditions supported growth and maintenance cartilage in an immature state, but did not induce biomechanical or collagen network maturation.

Animals↗
PubMed1997

Loss of decorin from the surface zone of articular cartilage in a chick model of osteoarthritis.

The objective of this study was to immunolocalize decorin and to assess changes as a result of pyridoxine (PN) deficiency in chick articular cartilage from femoral condyles. After maintenance on a normal diet for the first two weeks after hatching, 15 broiler chickens were deprived of this vitamin for 6 weeks. It was previously shown that the ankle joints of PN-deficient animals are swollen with effusions. They also present an abnormal gait, enlarged bony margins, and fissuring of the articular cartilages. Milder changes (no fissures) were also shown in the knee joints. Data from a previous study were suggestive that sulfated glycosaminoglycans are lost from the knee cartilage surface into synovial fluid. The current study was focused on the small proteoglycan, decorin, which coats the surface of collagen fibrils and may regulate their morphology. To examine decorin in normal and PN-deficient articular cartilage, a monoclonal antibody to an epitope on the protein core of decorin was used for immunohistochemical staining of tissue sections and for Western Blot analysis of cartilage extracts. Reduction of staining with the antibody was demonstrated in the tangential surface zone of PN-deficient cartilage, and Western Blot analysis showed reduced intensity of decorin bands compared to normal controls. These data suggest that a lack of decorin may play a role in the enlargement of collagen bundles in the tangential zone of PN-deficient articular cartilage as observed in a previous electron microscopic study.

Animals↗
PubMed2003

Different in vitro activity of flurbiprofen and its enantiomers on human articular cartilage.

The 2-arylpropionic acid derivatives or 'profens' are an important group of non-steroidal anti-inflammatory drugs that have been used for the symptomatic treatment of various forms of arthritis. These compounds are chiral and the majority of them are still marketed as racemate although it is known that the (S)- form is the principal effective in the cyclooxygenase inhibition. However, recent findings suggest that certain pharmacological effect of 2-arylpropionic acids cannot be attributed exclusively to the (S)-(+) enantiomer. To obtain further insights into the pharmacological effect of profens, the present study investigated the influence of racemic and pure enantiomers of flurbiprofen on the production of nitric oxide and glycosaminoglycans, key molecules involved in cartilage destruction. The culture of human articular cartilage stimulated by interleukin-1beta (IL-1beta), which plays an important role in the degradation of cartilage, has been established, as a profit experimental model, for reproducing the mechanisms involved in the pathophysiology of arthritic diseases. Our results show that mainly (S)-(+)-flurbiprofen decreases, at therapeutically concentrations, the IL-1beta induced cartilage destruction.

Cartilage, Articular↗
PubMed1992

Fibronectin fragments cause chondrolysis of bovine articular cartilage slices in culture.

Elevated fibronectin (Fn) and Fn fragment concentrations are found in the synovial fluid of osteoarthritic and rheumatoid arthritic patients. Fn has been shown to affect expression of chondrocytic matrix proteins, and Fn fragments have been shown to elevate gene expression of neutral proteinases in synoviocytes. For these reasons, we tested the effects of Fn fragments on protease release and resultant proteoglycan release from cartilage in serum-free bovine articular cartilage explant cultures. We have found that 1 microM amino-terminal 29- and 50-kDa gelatin-binding Fn fragments caused over a 50-fold enhancement of gelatinolytic and collagenolytic proteinase release with a 23-fold enhancement of proteoglycan (PG) release. Release was significant at fragment concentrations as low as 20 nM. An integrin-binding 140-kDa fragment mixture was the least active fragment, whereas native Fn had little activity. The relative activities of the fragments correlated with their relative abilities to bind to cartilage. The RGDS integrin-recognition peptide also caused release, although sequence mutants did not. PG release was blocked by actinomycin D, cycloheximide, and deoxyglucose. Fn fragment-mediated PG release was decreased in 10% serum by over 10-fold but was still 2-fold greater than in controls. In the presence of insulin-like growth factor-1, PG release was as great as without serum. We suggest that Fn fragments, as found in diseased synovial fluid, may contribute to protease-mediated damage to cartilage.

Animals↗
PubMed1990

Nonactivatability of latent proteoglycanases in intact adult articular cartilage.

Para-aminophenylmercuric acetate activates collagenases and proteoglycanases in vitro only in cartilage plugs but not in intact articular cartilage. This suggests that activation of latent proteoglycanases is only possible after damage of the tissue's integrity. Therefore isolated plugs of cartilage seem not to be suitable for determining proteoglycan turnover. For these investigations we propose the use of intact joint areas from whole half-joints.

Animals↗
PubMed1985

Intercellular network in articular cartilage of pigs with experimentally induced arthritis. I. Fact or artifact?

Porcine articular cartilage from cases of experimentally induced Erysipelas arthritis was examined with different histological techniques and by electron microscopy. A small percentage of specimens of osteoarthritic cartilage revealed an interlacunar network in the extracellular matrix. These "matrix-streaks" showed characteristic features of densely packed fibrillar elements and collagenous fibrils, as narrow bands connecting adjacent chondrocytes. In a given cartilage site the network had a constant pattern. It is hypothesized that the network formation is correlated with altered joint metabolism and represents regressive changes in cartilage matrix as a result of external mechanical forces. Using a variety of methods, the possibility of the network being an artifact of histological processing could virtually be ruled out. As there are so far only few and contradictory reports on the interlacunar network of articular cartilage, its precise biological significance remains to be established.

Animals↗
PubMed2005

[Treatment of focal articular cartilage lesions of the knee with autogenous osteochondral grafts].

PURPOSE OF THE STUDY: A chondral/osteochondral defect involving the articular surface of a joint is still a therapeutic problem. Many surgical techniques have been studied in an attempt to restore the damaged articular cartilage. Autogenous osteochondral graft has gained in clinical popularity because of its technical feasibility and cost effectiveness, however, only a few series have been reported in the literature. MATERIAL: A retrospective study included 14 patients with 14 knees with focal full thickness articular cartilage defects hospitalised in our department between January 1997 and June 2000. The diagnoses included six knees with osteonecrosis, five knees with osteochondritis dissecans and three knees with traumatic cartilage defect. METHODS: All these patients underwent an osteochondral autografts of the knee with 2 years follow-up. The evaluations were based on functional assessments, which included pain, giving way, locking, recurrent effusion, knee scores, functional scores and Lysholm scores. The postoperative values of functional assessments among the three categories of diagnosis were compared statistically using Kruskal-Wallis test. Radiographs of the knees were examined for joint congruence, joint space narrowing and degenerative changes. RESULTS: The study showed good or excellent clinical results in over than 85%. The duration of pain of the knees relief ranged from six to 16 weeks after surgery. DISCUSSION: There was no correlation of the clinical results with the underlying diagnosis, including osteonecrosis, osteochondritis dissecans and traumatic cartilage defect. Improvement in symptoms appeared time-dependent, ranging from 6 to 16 weeks, suggesting that postoperative protection of the graft is warranted. There was no radiographic progression of degenerative changes of the knee on the medium-term follow-up. CONCLUSION: There was no correlation of the clinical results with the underlying diagnoses. It appears that an osteochondral graft has the potential to prevent or delay the development of degenerative changes of the knee in the medium-term follow-up. Autogenous osteochondral graft is considered as a good method in the treatment of knees with moderately sized articular cartilage defects.

Adult↗
PubMed2000

Detection of articular cartilage lesions: experimental evaluation of low- and high-field-strength MR imaging at 0.18 and 1.0 T.

The objective of this study was to compare the diagnostic performance of a dedicated orthopedic magnetic resonance (MR) imaging system (0.18 T) and a conventional MR imaging system (1.0 T) in the detection of articular cartilage lesions. Fifty knee joint specimens of pigs with artificially created articular cartilage lesions of different diameters, grades (2-3), and localizations, as well as 50 joints with intact articular cartilage, were imaged at 0. 18 and 1.0 T. Diagnostic performance was determined by means of receiver operating characteristics (ROC) analysis with three independent observers. For none of the pulse sequences used at 0.18 T or 1.0 T areas under ROC curves (A(z)) showed significant differences between the three observers. A(z) values from averaged data were as follows: a) 0.18 T: T1-weighted spin echo (SE): 0.70, proton-density-weighted SE: 0.59, T2-weighted SE: 0.61, two-dimensional (2D) gradient-echo (GRE): 0.73, 3D GRE: 0.75; and b) 1.0 T: T1-weighted SE: 0.73, fat-suppressed T2-weighted turbo-SE: 0. 79, 2D fast low-angle shot (FLASH): 0.79, fat-suppressed 3D FLASH: 0. 96, and water-excited 3D double-echo steady state (DESS): 0.96. With the use of 3D pulse sequences, the high-field system demonstrated a significantly better diagnostic performance than the low-field system in the detection of grades 2 and 3 articular cartilage lesions (P < 0.001).

Animals↗
PubMed1997

An investigation of the stress distribution generated in articular cartilage by crystal aggregates of varying material properties.

Several joint diseases are associated with the deposition of crystals within the articular cartilage. A variety of crystal aggregates have previously been identified throughout the thickness of the cartilage. A linear elastic finite element model representing instantaneous, or short-term, loading conditions has been developed of a large crystal aggregate surrounded by articular cartilage. The material properties of the aggregate and the cartilage were varied and the resultant shear stress and equivalent strain distribution in the surrounding cartilage studied in order to provide some indication of the relative potential of various types of crystal aggregate to cause damage to the articular cartilage. Results indicated that aggregates with a Young's modulus either much less, or much greater, than that of the surrounding cartilage generated the maximum shear stress and equivalent strain concentrations at the interface between the aggregate and the cartilage. Also, that highly compressible aggregates, with a very low Poisson's ratio, generated higher shear stress and equivalent strain concentrations in the surrounding cartilage than aggregates of a more incompressible nature. Under conditions of short-term loading these results suggest that crystal aggregates present within the cartilage layer will increase the shear stress and equivalent strain concentrations in the surrounding cartilage, and therefore have the potential to cause damage to the cartilage.

Biomechanical Phenomena↗
PubMed1992

Long-lasting tolerance of articular cartilage after experimental intraoperative radiation in rabbits.

In experimental intraoperative irradiation, 18 adult rabbits received a single, 50-Gy dose of x-radiation at a unilateral knee joint, and subsequent changes in the articular cartilage were examined over a 15-month period by histology, scanning electron microscopy, and autoradiography. Although the subchondral bone showed histologically typical findings of osteonecrosis three to nine months postirradiation, the articular cartilage revealed no obvious degenerative changes during the entire study period. Scanning electron microscopy revealed normal collagen architecture in the irradiated cartilage for as long as 15 months postirradiation. Autoradiography demonstrated active RNA synthesis by the irradiated chondrocytes during the same period. These results indicate that articular cartilage tissue tolerates intraoperative radiotherapy without sustaining serious degenerative changes, unless possible collapse or contracture disturbs its biomechanical integrity. The survival of articular cartilage can be advantageous for this type of limb-salvage surgery in the treatment of malignant bone tumors around a synovial joint.

Animals↗
PubMed2004

The role of viscoelasticity of collagen fibers in articular cartilage: theory and numerical formulation.

The relative importance of fluid-dependent and fluid-independent transient mechanical behavior in articular cartilage was examined for tensile and unconfined compression testing using a fibril reinforced model. The collagen matrix of articular cartilage was modeled as viscoelastic using a quasi-linear viscoelastic formulation with strain-dependent elastic modulus, while the proteoglycan matrix was considered as linearly elastic. The collagen viscoelastic properties were obtained by fitting experimental data from a tensile test. These properties were used to investigate unconfined compression testing, and the sensitivity of the properties was also explored. It was predicted that the stress relaxation observed in tensile tests was not caused by fluid pressurization at the macroscopic level. A multi-step tensile stress relaxation test could be approximated using a hereditary integral in which the elastic fibrillar modulus was taken to be a linear function of the fibrillar strain. Applying the same formulation to the radial fibers in unconfined compression, stress relaxation could not be simulated if fluid pressurization were absent. Collagen viscoelasticity was found to slightly weaken fluid pressurization in unconfined compression, and this effect was relatively more significant at moderate strain rates. Therefore, collagen viscoelasticity appears to play an import role in articular cartilage in tensile testing, while fluid pressurization dominates the transient mechanical behavior in compression. Collagen viscoelasticity plays a minor role in the mechanical response of cartilage in unconfined compression if significant fluid flow is present.

Cartilage, Articular↗
PubMed1976

Cathepsin D activity in bovine articular cartilage, synovial membrane and fluid: degradation of cartilage proteoglycans from same joint.

Cathepsin D type proteases were extracted from articular cartilage, synovial membrane, and synovial fluid from normal, adult bovine knee joints. A sensitive enzyme assay made it possible to measure protease activity in the different tissues from individual joints. Highest activity was found in the synovial membrane, while cell free synovial fluids contained comparatively low activity. The degrading effect on articular cartilage proteoglycans (PGC and PGS), isolated from the same joints, was demonstrated by gelfiltration on Sepharose columns and by viscometry. Gelfiltration profiles of incubation mixtures indicated a proteolytic effect on PGC and on PGS), at pH 3.5, in concentrations of enzyme and proteoglycans found in cartilage tissue. No effect at neutral pH was obtained despite a 100-fold increase of enzyme concentration. These findings were supported by viscometry data. The degrading effect of enzymes from all sources was completely inhibited by pepstatin.

Animals↗