[ADAPTATION OF ARTICULAR CARTILAGE TO THE SLIDING OF INTRA-ARTICULAR TENDONS].
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Acclimatization↗
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Imaging the physical and morphological properties of a multi-zone young articular cartilage at microscopic resolution.
PURPOSE: To characterize a number of physical and morphologic properties of young articular cartilage. These properties include the anisotropy of T(2) relaxation, optical retardation, orientation of the collagen fibrils, total thickness of the tissue, number of histologic sub-zones in the tissue, width of individual sub-zones, and correlation between the depths of the local T(2) maxima and the local retardation minima. MATERIALS AND METHODS: Microscopic magnetic resonance imaging (mciro MRI) and polarized light microscopy (PLM) were used to examine three side-by-side specimens from a humeral head of a three-month-old beagle that exhibited a unique topographic heterogeneity from three-zones centrally to multi-zone peripherally. RESULTS: The centrally located specimen showed that the collagen fibrils across the tissue depth have a pattern of the classic three histologic sub-zones (tangential, transitional, and radial). A much more complicated multi-zone structure was found in the specimen located peripherally, with a second transitional zone and a second tangential zone located at the deep part of the tissue. We also showed that the orientation of the collagen fibrils that form the cocoon-shaped territorial matrix surrounding the clusters of chondrocytes can be imaged by our PLM technique. CONCLUSION: The results from the young animal in this report, together with our observations from older animals, demonstrate that MRI and PLM can be used to study the epiphyseal expansion of cartilage in young animals during its growth and subsequent loss in older animals. An illustrative model for the structure of collagen fibrils in a humeral head is suggested as an extension to the classic three-zone model for young articular cartilage.
Animals↗
Articular cartilage depicted at optimized angular position of Laue angular analyzer by X-ray dark-field imaging.
Using 36.0 keV X-ray from synchrotron radiation, we examined the optimized angular position of Laue analyzer for depicting articular cartilage of an intact human finger by X-ray dark-field imaging. The surface of articular cartilage was depicted clearly by adopting the offset angle of 0.04 arcsec to lower angular side to the analyzer whilst the contour of articular cartilage was delineated clearly at the other angular positions of the analyzer within the width of the rocking curve.
Anisotropy↗
Effects of different irrigation liquids and times on articular cartilage: an experimental, biomechanical study.
To characterize the suitability of different solutions [6% Dextran, 5% sorbitol (I); 5% fructose (II); 5% mannitol (III); Ringer's solution (IV)] for arthroscopy, bovine knee articular cartilage specimens (n = 52) were immersed for 0, 2, 4, or 20 h before indentation creep testing, known as a sensitive probe for tissue degeneration. Immersion in liquid I for up to 20 h produced significant softening of articular cartilage [p < 0.05, Friedman two-way analysis of variance (ANOVA)]. Liquids II-III produced no statistically significant changes in the deformational characteristics of articular cartilage. After 2 h of immersion in liquid IV deformation increased and remained elevated over the observation period (p < 0.05, Friedman two-way ANOVA). Based on these results, the first and most remarkable softening of cartilage took place with Ringer's solution as compared with nonionic solutions. Therefore, the nonionic solutions, such as 5% fructose or mannitol, may have potential for use as an irrigation liquid during arthroscopic procedures.
Analysis of Variance↗
Evaluation of articular cartilage: radiographic and cross-sectional imaging techniques.
Many diagnostic modalities may be used to evaluate articular cartilage. Plain radiography remains the preferred initial study for cartilage evaluation, although even specialized views such as weight-bearing, tunnel, and flexion lateral projections are insensitive in the detection of early cartilage loss. Compared with newer modalities, conventional arthrography has limited capacity for the assessment of cartilage. Computed tomography performed after intraarticular injection of contrast material (ie, CT arthrography) has improved accuracy but is essentially limited to the axial plane. Magnetic resonance (MR) imaging, with its superb soft-tissue contrast and multiplanar capabilities, has shown promise in depicting articular cartilage. Cartilage is best depicted when an "arthrogram effect" is present, achieved with T2-weighted spin-echo imaging, with some gradient-echo pulse sequences, and when intraarticular contrast material is used. If performed with such techniques, MR imaging is the method of choice for evaluating specific cartilage loss, osteochondritis dissecans, and other osteochondral abnormalities.
Arthrography↗
The reactions of articular cartilage to experimental wounding: role of apoptosis.
OBJECTIVE: To determine the cellular and matrix responses to experimental wounding of articular cartilage. METHODS: Immature and mature bovine articular cartilage was used as an in vitro model system to study the cellular responses to cartilage wounding. Explant cultures were wounded centrally with a trephine and maintained for up to 10 days. TUNEL labeling together with ultrastructural analyses were used to assess the nature of the observed cell death. In vitro labeling with 3H-thymidine was used to detect cell proliferation, and 2 antibodies (COL2-3/4M and BC-13) were used to detect changes in matrix turnover. RESULTS: Cell death was observed as a response to wounding and was considered to be a combination of necrosis and apoptosis. In immature tissue, cell death was more pronounced, particularly in the articular surface region. Within the area of cell death, many cells that did not die subsequently underwent proliferation. The collagenous network showed evidence of denaturation in the area of the wound, but "aggrecanase" activity was not detected. CONCLUSION: There are 2 contrasting, but related, responses to cartilage wounding--apoptosis and proliferation. In order to improve cartilage repair, future studies need to elucidate the regulatory mechanisms that determine these responses.
Animals↗
Depth- and strain-dependent mechanical and electromechanical properties of full-thickness bovine articular cartilage in confined compression.
Compression tests have often been performed to assess the biomechanical properties of full-thickness articular cartilage. We tested whether the apparent homogeneous strain-dependent properties, deduced from such tests, reflect both strain- and depth-dependent material properties. Full-thickness bovine articular cartilage was tested by oscillatory confined compression superimposed on a static offset up to 45%. and the data fit to estimate modulus, permeability, and electrokinetic coefficient assuming homogeneity. Additional tests on partial-thickness cartilage were then performed to assess depth- and strain-dependent properties in an inhomogeneous model, assuming three discrete layers (i = 1 starting from the articular surface, to i = 3 up to the subchondral bone). Estimates of the zero-strain equilibrium confined compression modulus (H(A0)), the zero-strain permeability (kp0) and deformation dependence constant (M), and the deformation-dependent electrokinetic coefficient (ke) differed among individual layers of cartilage and full-thickness cartilage. HiA0 increased from layer 1 to 3 (0.27 to 0.71 MPa), and bracketed the apparent homogeneous value (0.47 MPa). ki(p0) decreased from layer 1 to 3 (4.6 x 10(-15) to 0.50 x 10(-15) m2/Pa s) and was less than the homogeneous value (7.3 x 10(-15) m2/Pa s), while Mi increased from layer 1 to 3 (5.5 to 7.4) and became similar to the homogeneous value (8.4). The amplitude of ki(e) increased markedly with compressive strain, as did the homogeneous value: at low strain, it was lowest near the articular surface and increased to a peak in the middle-deep region. These results help to interpret the biomechanical assessment of full-thickness articular cartilage.
Animals↗
[Structure of the articular cartilage in the middle aged].
In persons 17-83 years of age having no articular disorders 39 samples of the patellar articular cartilage, the articulated surface and the femoral head have been studied histochemically, histometrically and electron microscopically. Age involution of the articular cartilage is revealed after 40 years of age as a progressive decrease in chondrocytes density in the superficial and (to a less degree) in the intermediate zones. This is accompanied with a decreasing number of 3- and 4-cellular lacunae and with an increasing number of unicellular and hollow lacunae. In some chondrocytes certain distrophic and necrotic changes are revealed. In the articular matrix the zone with the minimal content of glycosaminoglycans becomes thicker and keratansulfate content in the territorial matrix of the cartilage deep zone grows large.
Adult↗
Osteoarthritic changes in the biphasic mechanical properties of the chondrocyte pericellular matrix in articular cartilage.
The pericellular matrix (PCM) is a narrow region of cartilaginous tissue that surrounds chondrocytes in articular cartilage. Previous modeling studies indicate that the mechanical properties of the PCM relative to those of the extracellular matrix (ECM) can significantly affect the stress-strain, fluid flow, and physicochemical environments of the chondrocyte, suggesting that the PCM plays a biomechanical role in articular cartilage. The goals of this study were to measure the mechanical properties of the PCM using micropipette aspiration coupled with a linear biphasic finite element model, and to determine the alterations in the mechanical properties of the PCM with osteoarthritis (OA). Using a recently developed isolation technique, chondrons (the chondrocyte and its PCM) were mechanically extracted from non-degenerate and osteoarthritic human cartilage. The transient mechanical behavior of the PCM was well-described by a biphasic model, suggesting that the viscoelastic response of the PCM is attributable to flow-dependent effects, similar to that of the ECM. With OA, the mean Young's modulus of the PCM was significantly decreased (38.7+/-16.2 kPa vs. 23.5+/-12.9 kPa, p < 0.001), and the permeability was significantly elevated (4.19+/-3.78 x10(-17) m(4)/Ns vs. 10.2+/-9.38 x 10(-17) m(4)/Ns, p < 0.01). The Poisson's ratio was similar for both non-degenerate and OA PCM (0.044+/-0.063 vs. 0.030+/-0.068, p > 0.6). These findings suggest that the PCM may undergo degenerative processes with OA, similar to those occurring in the ECM. In combination with previous theoretical models of cell-matrix interactions in cartilage, our findings suggest that changes in the properties of the PCM with OA may have an important influence on the biomechanical environment of the chondrocyte.
Biomechanical Phenomena↗
A METHOD OF ESTIMATING THE "HEALTH" OF RABBIT ARTICULAR CARTILAGE BY ASSAYS OF RIBONUCLEIC ACID AND PROTEIN SYNTHESIS.
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Autoradiography↗
Material properties and biosynthetic activity of articular cartilage from the bovine carpo-metacarpal joint.
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.
Animals↗
Is the repair of articular cartilage lesion by costal chondrocyte transplantation donor age-dependent? An experimental study in rabbits.
The repair of chondral injuries is a very important problem and a subject of many experimental and clinical studies. Different techniques to induce articular cartilage repair are under investigation. In the present study, we have investigated whether the repair of articular cartilage folowing costal chondrocyte transplantation is donor age-dependent. Transplantation of costal chondrocytes from 4- and 24-week old donors, with artificially induced femoral cartilage lesion, was performed on fourteen 20-week-old New Zealand White male rabbits. In the control group, the lesion was left without chondrocyte transplantation. The evaluation of the cartilage repair was performed after 12 weeks of transplantation. We analyzed the macroscopic and histological appearance of the newly formed tissue. Immunohistochemistry was also performed using monoclonal antibodies against rabbit collagen type II. The newly formed tissue had a hyaline-like appearance in most of the lesions after chondrocyte transplantation. Positive immunohistochemical reaction for collagen II was also observed in both groups with transplanted chondrocytes. Cartilage from adult donors required longer isolation time and induced slightly poorer repair. However, hyaline-like cartilage was observed in most specimens from this group, in contrast to the control group, where fibrous connective tissue filled the lesions. Rabbit costal chondrocytes seem to be a potentially useful material for inducing articular cartilage repair and, even more important, they can also be derived from adult, sexually mature animals.
Aging↗
Equilibrium water partition in articular cartilage.
Water partition between the interstitial fluid in articular cartilage and an external bathing solution was found using a new in-situ method. This consisted of measuring the concentration of radioactive water allowed to diffuse through the articular surface of laterally constrained cartilage-subchondral bone plugs. Incubation times ranged from 15 minutes to 48 hours. Tracer solutions included: Hank's Balanced Salt Solution with and without antibiotics and enzyme inhibitors, and distilled water. Bulk partition coefficients ranged from 0.305 to 0.811. Both the hydration and partition coefficients varied spatially with depth, while no association was found between them. The macromolecular structure of the collagen and proteoglycan components are believed responsible for these findings.
Animals↗
Efficiency of magnetic liposomal transforming growth factor-beta 1 in the repair of articular cartilage defects in a rabbit model.
We evaluated the efficacy of a magnetic liposomal delivery system of transforming growth factor (TGF)-beta(1) in the treatment of articular cartilage defects in a rabbit model. Articular cartilage defects were created in the patellar groove of rabbits, and a permanent magnet or a nonmagnetic alloy was implanted in the defect site. Magnetic liposomal drugs, prepared by the conventional film method and sonication, were injected into the defect site 1 week after surgery. First, the efficacy of the magnetic liposomal delivery system was evaluated by using a model compound fluorescence-labeled dextran 40,000 (FD-40). Then, the therapeutic efficiency of magnetic liposomal TGF-beta(1) was evaluated by cartilage histological scoring at 4, 8, and 12 weeks after surgery. The injected magnetic liposomal FD-40 accumulated at the target site where a permanent magnet had been implanted. The histological score showed that the injection of magnetic liposomal TGF-beta(1) under magnetic force was significantly effective in the repair of the defect site over 12 weeks after surgery. Injection of TGF-beta(1) into the cartilage defect was effective as a magnetic liposomal preparation under magnetic force, resulting in acceleration of the cartilage repair, probably because of the desirable accumulation of TGF-beta(1) at the target site.
Animals↗
Chondrocyte biosynthesis correlates with local tissue strain in statically compressed adult articular cartilage.
In this study, we investigated the depth-dependent metabolic and structural responses of adult articular cartilage to large-strain, static, unconfined compression. Changes in cell biosynthetic activity and several morphometry-based structural parameters (cell density, cell volume fraction, cell surface-area density, mean cell surface area, and mean cell volume) were measured at eight sites representing different depth-zones between the articular surface and the cartilage/bone border. In addition, local axial strain in the superficial, transitional, upper radial, and lower radial zones was estimated on the basis of the change in cell density values. Static compression of articular cartilage revealed a highly heterogeneous deformation profile through the depth of the sample as well as zone-specific changes in biosynthetic activity, as reflected by incorporation of [3H]proline. The axial strains in the top layers were greater than the applied surface-to-surface strain, whereas axial strains adjacent to the cartilage/bone border were significantly less than the applied strain. Zonal changes in cell density and axial strain that occurred during static compression correlated well with alterations in metabolic activity. These coordinated changes between cell biosynthesis and cartilage structure suggest that zone-specific variations in mechanical stimuli could be responsible for spatially varied patterns of cartilage metabolic activity under load.
Animals↗
Articular cartilage echography as a criterion of the evolution of osteoarthritis of the knee.
We propose a modification of the Aisen's technique by which precise reproducible measurements of articular cartilage thickness of the knee is possible. A group of 23 patients with severe osteoarthritis was studied by ultra-sound (US) before knee prosthesis surgery. Evaluation with US was performed by a real-time scanner with a 7.5 MHz linear probe with upper-patellar transverse scans tangent to the upper patellar pole at 90 degrees knee flexion. The cartilage thickness was measured within the weight-bearing area. After surgery, on the corresponding gross pathological specimen, US re-evaluation and histological measurements were made. Results of pre- and post-operative ultrasonography (US) data were compared with histological data and a good correlation between these measurements was found (p(t) > 10%). Preoperative measurements ranged from 2.4 to 0.3 mm. In order to obtain normal reference values of the articular cartilage within the weight-bearing area of the femoral trochlea for comparison, a group of 10 control subjects was also studied with US as above. The US data were then compared with computed tomography (arthro-CT) evaluations. No significant differences in mean values were found between the two imaging techniques (2.2 mm versus 2.3 mm for the lateral condyle and 2.3 versus 2.3 for the medial condyle, respectively). We conclude that ultra-sound measurement of articular cartilage thickness of femoral condyles is a sensitive and reproducible technique which permits early diagnosis and management of knee arthropathy and also quantification of cartilage damage.
Adolescent↗
Ultrastructural changes in articular cartilage after experimental section of the anterior cruciate ligament of the dog knee.
Ultrastructural changes in articular cartilage were studied in joint laxity induced by severing the anterior cruciate ligament of the right knee in sixteen mature dogs. The left knees provided controls; sham operations on six other dogs consisted of stab incision only, leaving the ligament intact. Cartilage from the medial tibial condyles was examined at intervals from two days to eighteen months later. In the superficial zone of the cartilage, collagen fibrils became abnormally widely spaced at four days, and narrower fibrils appeared from seven days after operation. Chondrocytes, particularly in the middle zone, became more active, with hypertrophy of cytoplasmic organelles detectable from four days. Superficial cells were initially healthy and became more numerous while their lipid content increased. The articular surface was fissured from two months and cell degeneration was rarely seen until several months after operation. These findings correlate with previous biochemical studies and are similar to early changes noted in degeneration of human articular cartilage.
Animals↗
Role of the chondrocytes in the breakdown of pig articular cartilage induced by complement-sufficient antiserum to pig erythrocytes.
Previous work showed that in organ culture pig articular cartilage is not affected by complement-sufficient antiserum to pig erythrocytes (AS plus C') unless it is associated with soft connective tissue. In the presence of synovial tissue the matrix becomes depleted of proteoglycan and may finally disintegrate. Immunoglobulin fails to enter normal cartilage matrix, but penetrates depleted matrix and reacts with the surfaces of the chondrocytes. The present experiments were made to see whether the breakdown of partially depleted cartilage matrix would progress in AS plus C' after removal of the synovial explant. Affronted explants of articular cartilage and synovial tissue were cultivated in AS plus C' for 10 days (primary cultures). The synovial tissue was then removed and the isolated cartilage maintained for a further period either in AS plus or C' or in one of a variety of control media (SECONDARY CULTURES). The behavior of the isolated cartilage during the secondary culture period depended on the degree of breakdown attained at the end of the primary period. If only proteoglycan but not collagen had been seriously depleted, degradation of the matrix did not progress in AS plus C' and slight regeneration of metachromatic materal sometimes took place; regneration of matrix was greater after transfer to control medium. If collagen as well as proteoglycan had been destrobyed, the chondrocytes assumed a fibroblastic form, their surfaces no longer reacted with IgG antibody, and in secondary culture they failed to regenerate new matrix.
Animals↗