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PubMed2004

Articular calcified cartilage canals in the third metacarpal bone of 2-year-old thoroughbred racehorses.

We describe morphological aspects of the articular calcified cartilage mineralizing front 'tidemark' in the distal joint surface of the third metacarpal bone from 14 horses. Compositional backscattered electron scanning electron microscopy and confocal scanning light microscopy were conducted on polymethylmethacrylate (PMMA)-embedded medio-lateral slices. After maceration, scanning electron microscopy (SEM) was used to study the calcified cartilage surface in the 'wedges' intervening between the slices. An anatomically reproducible clustering of canals in the calcified cartilage was found at one site on the sagittal ridge in all the horses. The site is one that is relatively less loaded during joint function. These canals through calcified cartilage result from osteoclastic resorption (cutting cones) penetrating from bone through to the non-mineralized hyaline articular cartilage. Their presence may indicate a pathway for connection between bone and cartilage extracellular fluid. In one horse, repair of such canals by plugging with new calcified cartilage was demonstrated. Differences in the degree of mineralization of regions of cartilage were seen in the combined compositional-cum-topographical backscattered SEM images of the macerated 'tidemark' front. More-or-less circular patches of lower mineralization density were frequently centred on (and may possibly originate from) canals. These microanatomical features should be searched for in other joints, at other ages and in other species to discover their frequency and significance.

Animals↗
PubMed1995

Localized amyloid deposition in cartilage is glycosaminoglycans-associated.

Localized amyloid deposition is known to occur commonly in the articular cartilage of elderly patients. Its pathogenesis is uncertain and it is not known if other cartilage-containing tissues also contain amyloid deposits. Systemic amyloid deposits are known to contain highly sulphated glycosaminoglycans, a major constituent of cartilage. As the composition of articular cartilage glycosaminoglycans is known to change with age, we sought to identify whether localized amyloid deposition in cartilage was glycosaminoglycan-related. We examined specimens of articular cartilage over a wide age range and also examined a variety of cartilaginous tumours and tumour-like lesions for the presence or absence of amyloid deposits. Using mucin histochemistry (alcian blue: MgCl2 critical electrolyte concentration) and immunohistochemistry, we found that highly sulphated glycosaminoglycans (0.9 M and 1 M MgCl2), in particular keratan sulphate, localized to amyloid deposits in both articular cartilage and loose bodies derived from the articular surface. Other cartilaginous lesions (including loose bodies of primary synovial chondromatosis) were negative for amyloid and did not contain highly sulphated glycosaminoglycans. These findings suggest that changes in specific highly sulphated glycosaminoglycans may play a role in localized amyloid deposition in articular cartilage.

Adolescent↗
PubMed1987

Regression of blood vessels precedes cartilage differentiation during chick limb development.

We have previously investigated distinct areas of vascular regression in the developing vascular system of the chick limb bud. Avascular areas appear in a characteristic spatial and temporal pattern, and are correlated with the position of developing cartilage. In the present study, we examined limb-bud sections which had been double labeled for endothelial cells and developing cartilage in order to determine the relationship between the appearance of cartilage and the disappearance of capillaries. Endothelial cells, which specifically take up acetylated low-density lipoprotein (acLDL), were labeled by intravenously injecting fluorescent acLDL (DiIacLDL) into chick embryos at Hamburger and Hamilton stages 26-30. Avascular zones, which correspond to the developing digits, were clearly visible within the fluorescently labeled distal vasculature. The same sections were labeled with monoclonal antibodies specific for cartilage. We found that progressing avascularity in the digital regions was followed by increased staining for cartilage antigens in the same areas. Zones of avascularity always developed earlier than morphologically and immunologically detectable cartilage in all planes of section and were always larger than the areas of cartilage. These results demonstrate that blood vessels disappear in predictable areas prior to the overt differentiation of cartilage.

Animals↗
PubMed2003

The zonal distributions of alkaline phosphatase, adenosine triphosphatase, laminin, fibronectin and chondroitin 4-sulphate in growing rat humerus proximal epiphyseal cartilage: a histochemical and an immunohistochemical study.

Although there are many studies about epiphyseal cartilage extracellular matrix (ECM) macromolecules in bone formation, studies of their distribution and role in the mineralization of these components in growing rat humerus proximal epiphyseal cartilage have not been sufficiently detailed. The aim of this study was to determine the distributions of alkaline phosphatase (ALP), adenosine triphosphatase (ATPase), laminin, fibronectin and chondroitin 4-sulphate in growing rat humerus proximal epiphyseal cartilage. The rats were killed by cervical dislocation, and the humeri were removed, sectioned (6 and 10 microm) on a cryotome or paraffin microtome, and stained using histochemical and immunohistochemical methods. ALP and ATPase were markedly observed in the hypertrophy and calcifying cartilage. In addition, ATPase was found to be very strongly positive in the tangential zone of articular cartilage. Results of immunohistochemical staining for laminin, fibronectin and chondroitin 4-sulphate showed that the immunostaining was the heaviest in the tangential zone of articular cartilage. In growing epiphyseal plates, there were differences in the density of these macromolecules of chondrocytes as a function of the maturation process. In conclusion, these ECM macromolecules of epiphyseal cartilage may regulate the cell-cell and cell-matrix interactions as well as the matrix calcification during the ossification of epiphyseal cartilage.

Adenosine Triphosphatases↗
PubMed2006

Osteochondritis dissecans of the elbow: histopathological assessment of the articular cartilage and subchondral bone with emphasis on their damage and repair.

Osteochondritis dissecans (OCD) of the elbow is a localized injury of the articular cartilage and subchondral bone that is commonly seen in the young athlete. In the present study, the extent of damage and repair on the articular cartilage and subchondral bone was examined histologically using specimens of 25 osteochondral cylinders and seven loose bodies obtained from 25 young athletes who had undergone osteochondral autograft surgery. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assays for detecting apoptotic cells and immunohistochemistry of matrix metalloproteinases (MMP) were performed on the osteochondral cylinder specimens. The histological findings of the OCD of the elbow showed that the articular cartilage exhibited degenerative change, mimicking osteoarthritis, and was markedly damaged as the lesion progressed. TUNEL-positive cells and MMP-3- and -13-expressing cells were distributed in the degenerative articular cartilage and reparative fibrocartilage tissue. Separation occurred at either the deep articular cartilage or the subchondral bone, with the former being dominant in the early OCD lesions. The present results suggest that the primary pathological changes in OCD of the elbow were due to damage of articular cartilage induced by repeated stress following degenerative and reparative process of articular cartilage and subchondral fracturing, and separation subsequently occurred on the cartilage and developed onto the subchondral bone in its advanced stages.

Adolescent↗
PubMed2005

The role of cartilage canals in endochondral and perichondral bone formation: are there similarities between these two processes?

We investigated the development of cartilage canals to clarify their function in the process of bone formation. Cartilage canals are tubes containing vessels that are found in the hyaline cartilage prior to the formation of a secondary ossification centre (SOC). Their exact role is still controversial and it is unclear whether they contribute to endochondral bone formation when an SOC appears. We examined the cartilage canals of the chicken femur in different developmental stages (E20, D2, 5, 7, 8, 10 and 13). To obtain a detailed picture of the cellular and molecular events within and around the canals the femur was investigated by means of three-dimensional reconstruction, light microscopy, electron microscopy, histochemistry and immunohistochemistry [vascular endothelial growth factor (VEGF), type I and II collagen]. An SOC was visible for the first time on the last embryonic day (E20). Cartilage canals were an extension of the vascularized perichondrium and its mesenchymal stem cell layers into the hyaline cartilage. The canals formed a complex network within the epiphysis and some of them penetrated into the SOC were they ended blind. The growth of the canals into the SOC was promoted by VEGF. As the development progressed the SOC increased in size and adjacent canals were incorporated into it. The canals contained chondroclasts, which opened the lacunae of hypertrophic chondrocytes, and this was followed by invasion of mesenchymal cells into the empty lacunae and formation of an osteoid layer. In older stages this layer mineralized and increased in thickness by addition of further cells. Outside the SOC cartilage canals are surrounded by osteoid, which is formed by the process of perichondral bone formation. We conclude that cartilage canals contribute to both perichondral and endochondral bone formation and that osteoblasts have the same origin in both processes.

Animals↗
PubMedDate not supplied

Pulsed carbon dioxide laser for cartilage vaporization and subchondral bone perforation in horses. Part II: Morphologic and histochemical reactions.

A pulsed carbon dioxide laser was used to vaporize articular cartilage in four horses, and perforate the cartilage and subchondral bone in four horses. Both intercarpal joints were examined arthroscopically and either a 1 cm cartilage crater or a series of holes was created in the third carpal bone of one joint. The contralateral carpus served as a control. After euthanasia at week 8, the treated and control joints were examined for gross changes, and samples of cartilage and subchondral bone, synovial membrane, and peripheral lymph nodes were examined histologically. Depletion of cartilage matrix glycosaminoglycan was assessed by safranin-O histochemical staining of the laser site and adjacent cartilage. Cartilage removal by laser vaporization resulted in rapid regrowth, with fibrous and fibrovascular tissue and occasional regions of fibrocartilage at week 8. The subchondral bone, synovial membrane, and draining lymph nodes appeared essentially unaffected by the laser cartilage vaporization procedure. Conversely, carbon dioxide laser drilling of subchondral bone resulted in poor penetration, extensive areas of thermal necrosis of bone, and significant secondary damage to the apposing articular surface of the radial carpal bone.

Animals↗
PubMedDate not supplied

Upper airway dysfunction associated with collapse of the apex of the corniculate process of the left arytenoid cartilage during exercise in 15 horses.

OBJECTIVE: To report dynamic collapse of the apex of the left corniculate process under the right corniculate process into the airway at the dorsal apposition of the paired arytenoid cartilages during exercise as a cause of upper airway dysfunction in horses. DESIGN: Retrospective study. ANIMALS: Fifteen horses with a history of poor performance and/or upper respiratory tract noise during exercise. METHODS: Video recordings of all horses referred for upper airway evaluation using high-speed treadmill videoendoscopy (HSTV) between January 1998 and December 2003 were reviewed. Records of horses that developed dynamic collapse of the apex of the left corniculate process into the airway were included. Clinical history, age, gender, breed, and use of the horse were retrieved. RESULTS: Of 309 horses referred for examination for poor performance and/or upper respiratory tract noise during exercise, 15 (4.9%) had collapse of the apex of the left corniculate process under the right and into the airway at the dorsal apposition between the paired arytenoid cartilages during HSTV. There were 3 females and 13 males, aged from 2 to 5 years. Five horses had previous surgery for left recurrent laryngeal neuropathy (RLN): 2 had nerve muscle pedicle graft and 3 had laryngeal prosthesis. During HSTV, all 15 horses had progressive collapse of the apex of the left corniculate process under the right at the dorsal apposition of the 2 arytenoid cartilages, and into the dorsal aspect of the rima glottidis. Review of video recordings revealed that collapse of the apex of the corniculate process was followed by progressive collapse of the left aryepiglottic fold and left vocal fold. The ventral aspect of the left corniculate cartilage maintained abduction in all horses. Two horses also had progressive collapse of the right vocal fold, 1 had rostral displacement of the palatopharyngeal arch, and another had dorsal displacement of the soft palate. CONCLUSIONS: Dynamic collapse of the apex of the left corniculate process of the arytenoid cartilage under the right is an uncommon cause of upper airway dysfunction in horses and the pathogenesis is unclear. We speculate that the left arytenoideus transversus muscle is unable to support the dorsal apposition between the arytenoid cartilages. This loss of support allows the elastic cartilage of the left corniculate process to collapse under the right and into the airway, as inspiratory pressure increases during exercise. This condition may be associated with an unusually advanced neuropathy of the adductor components of the left recurrent laryngeal nerve and may be an unusual manifestation of RLN; however, this is speculative and further investigation is required to determine its cause. CLINICAL RELEVANCE: Dynamic collapse of the apex of the left corniculate process and into the airway at the dorsal apposition between the paired arytenoid cartilages can only be diagnosed during HSTV. It is an uncommon cause of upper airway dysfunction but may affect the athletic potential of racing Thoroughbreds and Standardbreds.

Animals↗
PubMedDate not supplied

Ultrasonographic evaluation of tarsocrural joint cartilage in normal adult horses.

Ultrasonographic examination of the tarsus was performed on four clinically and radiographically normal limbs of adult horses. Particular attention was paid to the articular cartilage surfaces of the trochlear ridges of the talus and the distal intermediate ridge of the tibia. Two separate measurements of articular cartilage thickness were acquired from a longitudinal view at each site. Anatomy was confirmed with post mortem dissection. Ultrasonography was found to be a practical method for imaging the articular cartilage over the trochlear ridges of the talus and distal intermediate ridge of the tibia. The cartilage appeared as a hypoechoic band overlying the hyperechoic subchondral bone. The mean cartilage thickness over the lateral and medial trochlear ridges of the talus and the distal intermediate ridge of the tibia were 0.57 mm, 0.58 mm and 0.7 mm respectively. These measurements may have value for comparison to thickened cartilage and lesions of osteochondrosis and abnormally thinned cartilage of osteoarthritis. Ultrasound examination was not helpful in evaluating the proximal and distal intertarsal and tarsometatarsal joints, the close proximity of the articular surfaces obscured visualization of the articular cartilage.

Animals↗
PubMed1999

Effect of exercise on the proteoglycan metabolism of articular cartilage in growing foals.

In this study, the effect of different exercise regimens on proteoglycan metabolism of articular cartilage was examined in 43 newborn foals randomly divided into 3 groups: a) box-rest, b) box-rest with training and c) free pasture exercise. They were subjected to these exercise regimens from ages 1 week to 5 months and at 5 months, 24 foals (8 from each group) were sacrificed to assess short-term exercise effects. The remaining 19 foals were subjected to the same regimen of light exercise for an additional 6 months before being sacrificed to evaluate possible long-term effects. Articular cartilage explants were cultured and proteoglycan synthesis, both ex vivo and after 4 days of serum stimulation, release of endogenous and newly synthesised proteoglycans, and DNA- and GAG contents were measured to determine the metabolic state of the cartilage. Cartilage metabolic parameters in the box-rest group at 5 months indicated a retardation in development of the cartilage but, after an additional 6 months, this retardation had almost completely disappeared. The training regimen induced an increase in proteoglycan synthesis at 5 months in cartilage that was, however, accompanied by an increase in proteoglycan release. In the training group at the long-term, the ability of cartilage to increase proteoglycan synthesis when stimulated was severely reduced. We consider this extra proteoglycan synthesis capacity of great importance to repair small injuries and hence as essential to prevent an early onset of degenerative disorders such as osteoarthritis. Therefore, although extrapolation of in vitro data to the in vivo situation always should be done with the utmost care, it is concluded that pasture exercise is best for the development of healthy cartilage resistant to injury and other exercise protocols may carry harmful long-term effects.

Animals↗
PubMed1991

Differential responses of human and rat cartilage to degrading stimuli in-vitro.

Human cartilage biopsies incubated for 2 days in-vitro with 15% synovial fluid from rheumatoid arthritis patients contained less glycosaminoglycans (GAG) than control biopsies. Recombinant human (rHu)-interleukin-1 alpha (IL-1 alpha) and IL-1 beta at 10 or 100 ng mL-1 had no effect on human cartilage GAG levels. Similarly, GAG loss from human cartilage biopsies into medium over 5 days was significantly increased by synovial fluid but unaffected by 100 ng mL-1 IL-1 alpha or IL-1 beta compared with controls. However, when rat femoral head cartilage samples were incubated with 100 ng mL-1 rHu-IL-1 alpha or IL-1 beta for 5 days there was a significant increase in GAG loss from the cartilage into medium, whilst human synovial fluid significantly decreased the loss of GAG from rat cartilage into medium, compared with controls. The results demonstrate that human and rat cartilage differ from each other in their responses to degrading stimuli and suggest that animal cartilage may have limited application for the screening of drugs intended for the treatment of human arthritides.

Animals↗
PubMed2003

Experimental verification of the roles of intrinsic matrix viscoelasticity and tension-compression nonlinearity in the biphasic response of cartilage.

A biphasic-CLE-QLV model proposed in our recent study [2001, J. Biomech. Eng., 123, pp. 410-417] extended the biphasic theory of Mow et al. [1980, J. Biomech. Eng., 102, pp. 73-84] to include both tension-compression nonlinearity and intrinsic viscoelasticity of the cartilage solid matrix by incorporating it with the conewise linear elasticity (CLE) model [1995, J. Elasticity, 37, pp. 1-38] and the quasi-linear viscoelasticity (QLV) model [Biomechanics: Its foundations and objectives, Prentice Hall, Englewood Cliffs, 1972]. This model demonstrates that a simultaneous prediction of compression and tension experiments of articular cartilage, under stress-relaxation and dynamic loading, can be achieved when properly taking into account both flow-dependent and flow-independent viscoelastic effects, as well as tension-compression nonlinearity. The objective of this study is to directly test this biphasic-CLE-QLV model against experimental data from unconfined compression stress-relaxation tests at slow and fast strain rates as well as dynamic loading. Twelve full-thickness cartilage cylindrical plugs were harvested from six bovine glenohumeral joints and multiple confined and unconfined compression stress-relaxation tests were performed on each specimen. The material properties of specimens were determined by curve-fitting the experimental results from the confined and unconfined compression stress relaxation tests. The findings of this study demonstrate that the biphasic-CLE-QLV model is able to describe the strain-rate-dependent mechanical behaviors of articular cartilage in unconfined compression as attested by good agreements between experimental and theoretical curvefits (r2 = 0.966 +/- 0.032 for testing at slow strain rate; r2 = 0.998 +/- 0.002 for testing at fast strain rate) and predictions of the dynamic response (r2 = 0.91 +/- 0.06). This experimental study also provides supporting evidence for the hypothesis that both tension-compression nonlinearity and intrinsic viscoelasticity of the solid matrix of cartilage are necessary for modeling the transient and equilibrium responses of this tissue in tension and compression. Furthermore, the biphasic-CLE-QLV model can produce better predictions of the dynamic modulus of cartilage in unconfined dynamic compression than the biphasic-CLE and biphasic poroviscoelastic models, indicating that intrinsic viscoelasticity and tension-compression nonlinearity of articular cartilage may play important roles in the load-support mechanism of cartilage under physiologic loading.

Animals↗
PubMed1994

Cartilage stresses in the human hip joint.

The total surface stress measured in vitro on acetabular cartilage when step-loaded by an instrumented hemiprosthesis are partitioned into fluid and cartilage network stresses using a finite element model of the cartilage layer and measurements of the layer consolidation. The finite element model is based on in situ measurements of cartilage geometry and constitutive properties. Unique instrumentation was employed to collect the geometry and constitutive properties and pressure and consolidation data. When loaded, cartilage consolidates and exudes its interstitial fluid through and from its solid network into the inter-articular gap. The finite element solutions include the spatial distributions of fluid and network stresses, the normal flow velocities into the gap, and the contact network stresses at the cartilage surface, all versus time. Even after long-duration application of physiological-level force, fluid pressure supports 90 percent of the load with the cartilage network stresses remaining well below the drained modulus of cartilage. The results support the "weeping" mechanism of joint lubrication proposed by McCutchen.

Anthropometry↗
PubMed2004

Methotrexate (MTX) and albumin coupled with MTX (MTX-HSA) suppress synovial fibroblast invasion and cartilage degradation in vivo.

OBJECTIVE: To investigate the effect of methotrexate (MTX) and albumin coupled with methotrexate (MTX-HSA) on cartilage invasion and induction of perichondrocytic degradation by rheumatoid arthritis synovial fibroblasts (RA SF) in vivo. METHODS: Human cartilage and RA SF were co-transplanted in three groups of severe combined immunodeficient mice (SCID), which received 1 mg/kg free MTX (n = 9), 1 mg/kg MTX-HSA (n = 6), or 0.9% NaCl (n = 5), respectively, intraperitoneally twice a week. After 4 weeks' treatment, the mice were killed and the implants analysed histologically. RESULTS: The control group had a mean (SEM) score for cartilage invasion of RA SF of 2.0 (0.26) and for perichondrocytic cartilage degradation of 1.5 (0.34). In contrast, mice which received MTX showed a significantly reduced invasion (0.78 (0.14), p<0.01) and a reduction in perichondrocytic cartilage degradation scores (0.69 (0.2), p<0.05) in comparison with the control group. Mice treated with MTX-HSA also had significantly reduced scores for RA SF invasion into the cartilage (0.92 (0.41), p<0.05) and for cartilage degradation (0.83 (0.44), p<0.05) compared with controls. The effects of MTX and MTX-HSA were not significantly different between these two groups. CONCLUSION: Treatment with MTX or MTX-HSA significantly ameliorates cartilage destruction in the SCID mouse model for human RA.

Albumins↗
PubMed2005

Accuracy of quantitative magnetic resonance imaging in the detection of ex vivo focal cartilage defects.

BACKGROUND: No established, non-invasive diagnostic procedure for quantifying focal cartilage defects is currently available. OBJECTIVE: To test the accuracy of quantitative magnetic resonance imaging (qMRI) for reliable determination of cartilage defect size in various compartments of the human knee. METHODS: 24 tibial and patellar cartilage plates were harvested during knee arthroplasty. 74 cylindrical defects with diameters of 3, 5, and 8 mm were created with a punch. In 15 specimens (51 defects), the cartilage cylinders (inside the punch) were removed (approach 1), while in 9 specimens (23 defects) the surrounding tissue was removed mechanically and the cartilage cylinder was left in place (approach 2). All plates were imaged with a T(1) weighted water excitation gradient echo sequence at a resolution of 1.5 mm x 0.31 mm x 0.31 mm. The defect size was computed from the image data after interactive segmentation and compared with the known dimensions of the cylinders. RESULTS: Although there was a significant overestimation of the defect size by qMRI in 3 mm defects (mean (SD) +1.3 (0.58) mm = +/-42%; p<0.001), the overestimation was only +1.0 (0.57) mm (+/-21%; p<0.05) in 5 mm defects and +0.1 (0.39) mm (+/-4%; p = 0.31) in 8 mm defects (approach 1). Values were similar for approaches 1 and 2 and for patellar and tibial cartilage plates. CONCLUSIONS: These findings show that qMRI allows accurate quantification of focal cartilage defects. It may therefore represent a valuable tool in the diagnosis of traumatic cartilage lesions, osteochondrosis dissecans, and osteochondral fractures, and in monitoring their responsiveness to surgical or other treatments.

Cartilage, Articular↗
PubMed2006

Effect of pulsed electromagnetic fields on proteoglycan biosynthesis of articular cartilage is age dependent.

OBJECTIVE: To investigate the effects of a pulsed electromagnetic field (EMF) on articular cartilage matrix biosynthesis with regard to age and cartilage damage using a matrix depleted cartilage explant model. METHODS: Cartilage explants were obtained from metacarpophalangeal joints of calves and adult cows. After depletion of the extracellular matrix by trypsin digestion, samples were maintained in serum-free basal medium with and without the addition of interleukin 1beta (IL1beta). Half the samples were subjected to an EMF for 24 minutes daily; the other half were left untreated. Undigested and untreated explants served as negative controls. After 7 days, biosynthesis of matrix macromolecules was assessed by [35S]sulphate incorporation and values were normalised to hydroxyproline content. RESULTS: The EMF increased matrix macromolecule synthesis in undigested, untreated explants (p<0.009). In matrix depleted samples the EMF had no stimulatory effect on proteoglycan biosynthesis. IL1beta significantly decreased the de novo synthesis of matrix macromolecules (p<0.00004) in young and adult samples, but an EMF partly counteracted this inhibitory effect in cartilage samples from young, but not old animals. CONCLUSION: EMF promoted matrix macromolecule biosynthesis in intact tissue explants but had no stimulatory effect on damaged articular cartilage. The supressive effects of IL1beta were partially counteracted by EMF exposure, exclusively in cartilage derived from young animals. An EMF has age dependent chondroprotective but not structure modifying properties when cartilage integrity is compromised.

Aging↗
PubMed1983

Inhibition of cartilage breakdown by hydrocortisone in a tissue culture model of rheumatoid arthritis.

Bovine nasal cartilage discs cocultured with human rheumatoid synovial membrane or synovial-membrane-conditioned media release proteoglycan largely as a result of cartilage breakdown. We assessed the effects of hydrocortisone on proteoglycan distribution between cartilage and culture medium, and on cartilage breakdown expressed as the release of either proteoglycan or 35S-products from prelabelled discs. The presence of synovial membrane inhibited the capacity for net proteoglycan synthesis, preventing its accumulation in cartilage; this was little affected by hydrocortisone. The major response to pharmacological concentrations of hydrocortisone was suppression of both spontaneous and synovial-membrane-induced cartilage breakdown. The autolysis of synovial protein that normally occurred during culture was similarly prevented by comparable doses of corticosteroid. Changes in chromatographic distribution of the 35S-labelled degradation products released from cartilage conformed with a corticosteroid-induced inhibition of endogenous lysosomal or related proteinase activity. Additionally, inhibition of the early events in synovial membrane that are responsible for chondrocyte-mediated breakdown of cartilage may contribute significantly to the overall corticosteroid effect.

Animals↗
PubMed1988

Differential response to compressive loads of zones of canine hyaline articular cartilage: micromechanical, light and electron microscopic studies.

Thin (100 micron) perpendicular slices of canine femoral condylar cartilage were placed horizontally on the stage of a Nachet microscope and viewed by transmitted light in the differential interference contrast mode. Each slice was held on the microscope stage by a loading rig and tested mechanically in compression. Measured loads to a maximum of approximately 2-3 MN/m2 were applied to the end of the slice corresponding to the articular surface. Photographs were taken of the cartilage before and during loading, and the distance by which selected chondrocytes were displaced was used as an index of mechanical strain, i.e., of change in length/original length. Maximum strains were observed in the superficial cartilage zone. Minimum strains were recorded in the mid-zone, at a depth corresponding to approximately 75% of the total cartilage thickness. The relative concentrations of cartilage collagen (COL) and proteoglycan (PG) were assessed by the light and electron microscopic histochemical study of cartilage sections taken from contiguous blocks. Superficial cartilage, which deformed most, had high concentrations of oriented COL fibres, low concentrations of PG. Mid-zone cartilage, which deformed least, had lower concentrations of randomly arrayed COL fibres but relatively high concentrations of PG.

Animals↗