Cartilage Plugs Research Articles

Influence of cyclic loading on the nutrition of articular cartilage.

Articular cartilage is avascular. Nutrients are transported to the cells mainly by diffusion from the synovial fluid. Nutrient transport is also sometimes thought to be assisted by movement of fluid in and out of cartilage in response to cyclic loading of the tissue ('pumping'). The influence of pumping on transport of solutes through cartilage was measured by subjecting plugs of human femoral head cartilage immersed in medium containing radioactive solutes to a simulated walking cycle of 2.8 MPa at 1 Hz. The rate of absorption or desorption of tracers from the cycled plugs was compared with that of unloaded control plugs. For small solutes (urea, NaI) fluid transport did not affect the rate of solute transport significantly. Most major nutrients, such as glucose and oxygen, are small solutes and thus nutrition should not be affected by pumping. The rate of desorption of a large solute (serum albumin), however, was increased by 30-100% in plugs subjected to cyclic loading.

Growth-Plate Chondrocyte Cultures for Reimplantation Into Growth-Plate Defects in Sheep

Damage to epiphyseal growth plates due to fracture, trauma, or infection can lead to invasion of bone across the cartilage and localized arrest of long-bone growth. The implantation of a viable de novo cartilage plug into such defects may provide the appropriate cartilage presence necessary to inhibit the initial formation of bony bridges across the epiphysis and so maintain the growth potential. De novo cartilage plugs were prepared from ovine growth plates by culturing isolated epiphyseal chondrocytes from fetal lambs. After 14 days of culture, these de novo cartilage discs were composed of chondroitin sulfate, a small amount (5%) of dermatan sulfate, and cartilage-specific collagen. The cellular morphology and the histochemistry resembled resting zones of normal growth-plate cartilage. Those de novo cartilage discs, which had been embedded in gelled Type I collagen, retained their morphology and could be easily manipulated. On the other hand, Type II collagen and a polyuronic acid gauze (Surgicel) were not satisfactory substrates to facilitate subsequent transplantation into growth-plate defects. The use of 5-carboxyfluorescein diacetate succinimidyl ester (CSFE) throughout the cultures of epiphyseal chondrocytes or prolonged incorporation of [3H]-thymidine appeared to label the cells with useful markers for following their fate subsequent to implantation in vivo.

Optical verification of a technique for in situ ultrasonic measurement of articular cartilage thickness

Several investigators have used pulse-echo ultrasonics to measure the thickness of articular cartilage in situ. The underlying assumption in all measurements was that the second reflection used in thickness calculations was from the calcified-cartilage/cartilage boundary (tidemark). To investigate this assumption, the thickness of 24 cartilage plugs excised from a human femoral head was measured both ultrasonically and optically. Measurements established that the second reflection was from the tidemark and validated the ultrasonic technique as a method of mapping the thickness distribution of articular cartilage in synovial joints in situ.

Mechanical Disruption of Human Patellar Cartilage by Repetitive Loading In Vitro

Plugs of cartilage and subchondral bone from patellae were subjected to cyclic compression consisting of rapid ramp loading for 0.3 seconds followed by a 2.7 second pause. At 1000 psi cyclic load, surface abrasion of the cartilage was noted at 250 cycles of compression. Primary fissures, which penetrated to the calcified cartilage, developed at 500 cycles. Secondary fissures, emanating from the primary fissures at 30 degrees-90 degrees angles, and penetrating to varying depths, were observed at 1000 cycles. Coalescence of fissures and undermining of cartilage fragments were noted at 8000 cycles. With greater loads, the same sequence of events occurred with fewer cycles except that primary fissures appeared before the surface was abraided. Fissure formation did not occur in specimens subjected to loads of 250 psi to 500 psi even if the superficial 100 micron of cartilage was removed and specimens were loaded for 120,860 cycles. The deeper layers of cartilage appear to be of prime importance in resisting fissure formation.

The potential use of implanted radiolabelled bovine nasal cartilage in dialysis tubing to evaluate agents affecting cartilage degradation in vivo.

Cartilage which undergoes extensive autolysis in vitro (spontaneous or stimulated) is characterized by proteoglycan loss. Experimental conditions and inhibitor profils studies suggest neutral metalloproteinases induce the autolysis. In these preliminary studies we compared the degradation of Na2 35SO4 labeled bovine nasal cartilage (BNC) plugs placed in dialysis tubing in vitro and in vivo. The dialysis tubing was used to exclude large molecules (molecular weights greater than 2000) like proteinases, and proteinase inhibitors (e.g. alpha 2-macroglobulin) but not potential test agents from the implanted cartilage. Cartilage autolysis occurred with live tissue but not with heat-killed tissue in both the in vitro and in vivo systems. In addition retinoic acid and phenanthroline were effective when placed inside or outside the dialysis tubing. A potentially useful procedure to evaluate agents which affect cartilage degradation is described.

Effects of static and cyclic compressive loading on articular cartilage plugs in vitro.

The influence of static and intermittent stress on articular cartilage metabolism was examined in vitro. Full-thickness plugs of cartilage from femoral condyles of normal adult dogs were cultured while static or cyclic stresses were applied for 2 hours. The plugs were then incubated under atmospheric pressure for 2 hours in medium containing radioactive label, to provide measurements of net synthesis of glycosaminoglycan (GAG) or protein. As a control, cartilage from the same knee was cultured in the apparatus at atmospheric pressure. When cartilage plugs were exposed to static stress, or to cyclic stresses at a duty cycle of 60 seconds on/60 seconds off, net GAG synthesis was suppressed to 30-60% of that in controls. In contrast, when a duty cycle of 4 seconds on/11 seconds off was used, GAG synthesis was increased by 34%. The duty cycle which increased GAG synthesis did not affect protein synthesis or tissue contents of DNA, uronic acid, or water. At the cycle which suppressed GAG synthesis, protein synthesis and uronic acid content were decreased, and water content was increased. As judged by uptake of 14C-aminoisobutyric acid and 14C-xylose, the above changes in GAG synthesis do not appear to have been due to changes in diffusion of nutrient molecules through the cartilage during loading.

Structure of proteoglycans from different layers of human articular cartilage.

Full-depth plugs of adult human articular cartilage were cut into serial slices from the articular surface and analysed for their glycosaminoglycan content. The amount of chondroitin sulphate was highest in the mid-zone, whereas keratan sulphate increased progressively through the depth. Proteoglycans were isolated from each layer by extraction with 4M-guanidinium chloride followed by centrifugation in 0.4M-guanidinium chloride/CsCl at a starting density of 1.5 g/ml. The efficiency with which proteoglycans were extracted depended on slice thickness, and extraction was complete only when cartilage from each zone was sectioned at 20 microns or less. When thick sections (250 microns) were extracted, hyaluronic acid was retained in the tissue. Most of the proteoglycans, extracted from each layer under optimum conditions, could interact with hyaluronic acid to form aggregates, although the extent of aggregation was less in the deeper layers. Two pools of proteoglycan were identified in all layers by gel chromatography (Kav. 0.33 and 0.58). The smaller of these was rich in keratan sulphate and protein, and gradually increased in proportion through the cartilage depth. Chondroitin sulphate chain size was constant in all regions. The changes in composition and structure observed were consistent with the current model for hyaline-cartilage proteoglycans and were similar to those observed with increasing age in human articular cartilage.

Functional structure and strenght of the growth apparatus in normal and in uremic rats: 38

Epiphyseolysis is a rare condition in healthy children, but it is a common finding in children with chronic uremia.We therefore tried to analyse the tensile strenght and the functional structure of the proximal epiphyseal cartilage in normal and uremic rats. Material and methods Tibiae of Wistar rats (250g, uremia of four weeks duration, sham operated controls) were excised and freed from the surrounding soft tissue. In order to measure the tensile strenght of the growth apparatus, we prepared two bore wholes within the epiphyseal and diaphyseal bone, which served as a suspension in a ZWICK material testing machine.Non mineralized surfaces of cartilage, which were exposed by the final rupture, were prepared by the critical point drying method. Mineralized structures of cartilage and bone were exposed by digestion of unmineralized organic material by sodium hypochlorite. The specimens were analysed by scanning electron microscopy. Collagen fiber systems were either studied in serial sections using transmission electron microscopy, or by scanning electron microscopy after a dissolution procedure of the cartilage matrix by a papain treatment. Results Tensile strenght of normal rats was 56,73 +/-6,03 N. In uremic rats we found a significant reduction of tensile strenght of 39,90 +/- 4,96 N.Electron microscopical studies: Epiphyseal cartilage and epiphyseal bone are connected by numerous plugs of cartilage, which insert in holes of the epiphyseal bone plate. This structure prevents a sliding of the epiphysis.In columnar cartilage several columns are bound together to bundle pillars by collagen fibers. Longitudinally arranged fiber systems and a lattice system of shearing fibers can be identified in between these columns. Each pillar is connected with the epiphyseal bone plate by a radially orientated fiber system which resembles a system of shrouds. Neighbouring cells within the columns are bound together by a densely packed wickerwork of crossing fibers.In the zone of mineralization longitudinal septa of cartilage show globiform mineral deposits. These globiform surface structures enlarge the interface between the chondrocytes and the mineralized matrix, increasing the adhaesive strenght in this region.Longitudinal septa are gradually transformed into metaphvseal bone by enchondral ossification. Thus a continuous functional system of epiphyseal bone, growth cartilage and metaphyseal bone is formed.

A technique for the preparation of plugs of articular cartilage and subchondral bone

A technique for preparing plugs of articular cartilage and underlying subchondral bone wherein the surface of the tissue is both flat and perpendicular to the underlying bone is described. The tools needed to orient and cut the specimens, which were made for this purpose, are also described.

A Comparison of the Dynamic Force Transmitting Properties of Subchondral Bone and Articular Cartilage

Compression tests on plugs of bovine articular cartilage and of subchondral bone demonstrated that both are capable of deforming under pressure and thus attenuating peak dynamic forces applied to the plugs. Although cancellous bone is approximately ten times stiffer than articular cartilage per unit of thickness, subchondral bone in vivo is considerably thicker and would, therefore, seem capable of contributing to dynamic force attenuation as much as the cartilage does or more. Under physiological loads and loading rates, a film of synovial fluid on the cartilage added nothing to the ability of cartilage plugs to attenuate peak dynamic force; however, at very low load rates cartilage plugs coated with synovial fluid were consistently stiffer than specimens coated with veronate buffer. It is highly likely, from the evidence presented, that alterations in the quality of the subchondral bone could have a profound effect on the ability of a subchondral bone-articular cartilage system to withstand compressive dynamic forces.

Observations on the deposition of thorotrast in rat tissues.

Young growing rats were injected intravenously (tail vein) with colloidal thorium dioxide (thorotrast, 0.4-0.75 ml.) and the disposition of the material in the body was traced at various times after injection by autoradiographic techniques. In bone, the injected material was filtered from the blood and sequestered by macrophages in the marrow and intertrabecular regions. The distribution of these cells was nonuniform, and the autoradiographic pattern seemed to reflect growth processes. In the metaphysis of the long bone, the labeled cells (in fixed macrophages?) formed a band of high activity which became further removed from the epiphyseal cartilages with time, due to continued endochondral ossification. The rate at which the bones of the thorotrast-treated rats grew in length was normal. Nevertheless, irregular foci of endochondral bone formation were observed due to the formation of plugs of degenerate cartilage in the growth cartilages during the first 6 weeks, and focal hypertrophy of endosteal bone ...