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PubMed2003

Cartilage interstitial fluid load support in unconfined compression.

Under physiological conditions of loading, articular cartilage is subjected to both compressive strains, normal to the articular surface, and tensile strains, tangential to the articular surface. Previous studies have shown that articular cartilage exhibits a much higher modulus in tension than in compression, and theoretical analyses have suggested that this tension-compression nonlinearity enhances the magnitude of interstitial fluid pressurization during loading in unconfined compression, above a theoretical threshold of 33% of the average applied stress. The first hypothesis of this experimental study is that the peak fluid load support in unconfined compression is significantly greater than the 33% theoretical limit predicted for porous permeable tissues modeled with equal moduli in tension and compression. The second hypothesis is that the peak fluid load support is higher at the articular surface side of the tissue samples than near the deep zone, because the disparity between the tensile and compressive moduli is greater at the surface zone. Ten human cartilage samples from six patellofemoral joints, and 10 bovine cartilage specimens from three calf patellofemoral joints were tested in unconfined compression. The peak fluid load support was measured at 79 +/- 11% and 69 +/- 15% at the articular surface and deep zone of human cartilage, respectively, and at 94 +/- 4% and 71 +/- 8% at the articular surface and deep zone of bovine calf cartilage, respectively. Statistical analyses confirmed both hypotheses of this study. These experimental results suggest that the tension-compression nonlinearity of cartilage is an essential functional property of the tissue which makes interstitial fluid pressurization the dominant mechanism of load support in articular cartilage.

Adult↗
PubMed1996

A comparative study of perichondrial tissue in mammalian cartilages.

The general organization, cellular and extracellular components, and structural variation of perichondrium have been studied in different mammalian cartilages by polarized light and transmission electron microscopy. The overall structure is that of a dense connective tissue composed of variable numbers of thin, stratified, closely-packed lamellae, themselves composed of closely-matted collagen fibres running in the plane of the cartilage surface, but oriented at various angles to each other. Variations mainly concern the arrangement of the fibre bundles in the transition zones between perichondrial and cartilage matrices, and between perichondrium and surrounding tissues. Perichondrial cells have the characteristics of fibrocytes. A cambial layer of undifferentiated stem cells was never observed. A layer of 'perichondrial lining cells' with distinctive ultrastructural characteristics was observed in some cartilage units, which separates the perichondrium from the surrounding loose connective tissue. The ultrastructural results demonstrate that the cartilage and perichondrial extracellular matrices are distinct, and what have been designated perichondrial 'transition' and 'proliferative' zones are in fact parts of the most superficial cartilage layer. Variations in perichondrial structure appear to correlate with diversity of cartilage function and we conclude that each cartilage unit plus perichondrium forms a tightly-integrated entity, best regarded as a unitary organ within the skeletal system.

Adult↗
PubMed1998

Factors related to degradation of articular cartilage in osteoarthritis: a review.

OBJECTIVES: Osteoarthritis (OA) is a common joint deterioration initiated by multiple factors. To better understand related factors in the development of this disease, we focused on the mechanical stress loaded on articular cartilage. MATERIALS AND METHODS: The anterior cruciate ligaments of rabbit knee joints were transected, and expression of protein kinase C (PKC) examined immunohistochemically. The PKC activator 12-o-tetradecanoyl-phorbol-13-acetate (TPA) was then administered intraarticularly. To determine the involvement of gas mediators, a cartilage defect was made on the medical femoral condyle of rabbit knee joints. Hydrostatic pressure was loaded on the cartilage taken from the surrounding defects, and levels of superoxide anion and nitric oxide (NO) were measured. Bovine chondrocytes were subjected to cyclic mechanical stretch using a Flexercell Strain Instrument. Proteoglycan synthesis and PKC activity were measured. Expression of matrix metalloproteinase (MMP)-3 and tissue inhibitor of metalloproteinase (TIMP)-1 in articular cartilages obtained from OA patients were examined using Northern blots. RESULTS: Chondrocytes from experimentally induced OA were stained positively with anti-alpha-PKC antibody. Intraarticular administration of TPA prevented the development of OA changes. Cyclic tensile stretch loaded on chondrocytes decreased proteoglycan synthesis and PKC activity. Thus, PKC is involved in the stress-mediated degradation of articular cartilage. Cartilage defects led to degradation of surrounding cartilage and to enhanced superoxide anion and NO synthesis. We also noted increased and decreased expressions of MMP-3 and TIMP-1 mRNA in human OA cartilage, respectively. CONCLUSION: PKC, gas mediators (superoxide anion, NO), and proteinases are all involved in OA.

Animals↗
PubMed1989

The analysis of mineral deposits and proteoglycans content in the cartilage of mouse trachea using PIXE in combination with proton microprobe.

The tracheal cartilage of mature mice have been investigated using PIXE (proton induced X-ray emission) in combination with a proton microprobe on snap frozen cryosectioned material. The localization and quantitative measurements of P, S, Cl, K, Ca, Fe, and Zn concentrations as well as direct and indirect assessment of glycosaminoglycans by measurement of S content and measurement of bound colloidal iron at pH = 1.8 has been performed. Adjacent sections were stained with the Hale method in Müller modifications and the v. Koss method for sulphated mucins and inorganic deposits respectively. It has been found that hyaline cartilage in trachea contains mineral deposits and that P + Ca amounts up to 22% of cartilage dry mass. The Ca/P ratio approaches 2 what indicates hydroxyapatite type crystals. The cartilage contains substantial amounts of S reflecting the presence of sulphate groups. It was found that the cartilage binds also colloidal iron at low pH. There is a good correlation between places with high amount of bound colloidal iron assessed by PIXE and places showing strong Prussian Blue staining. The Fe/S ratio was, however, much lower in the cartilage than in other tissues what indicates that the colloidal iron method does not give quantitative results. There were no regions showing substantial decrease in Fe/S ratio which we found previously as typical for degenerating and calcifying growth plate cartilage. This may be connected with a relatively low degree of calcification degree of the tracheal cartilage.

Animals↗
PubMed2000

Macroencapsulation of human cartilage implants: pilot study with polyelectrolyte complex membrane encapsulation.

Autogenous cartilage transplantation is a generally accepted method in reconstructive surgery. A promising alternative to this established method could be represented by in vitro engineering of cartilage tissue. In both methods of autogenous transplantation, host response induces reduction of transplant size and transplant instability to an unforeseeable extent. To investigate if polyelectrolyte complex (PEC) membranes were able to avoid host-induced effects on implanted tissues without neglecting the tissue metabolism, human septal cartilage was encapsulated with polyelectrolyte complex membranes and subcutaneously implanted on the back of nude mice. Septal cartilage implants, without encapsulation served as control group. Histochemical and electron microscopic investigations were performed 1, 4, 8 and 16 weeks after implantation. In the case of an intact PEC-membrane no interactions between the host and the implant could be observed. In some implants, the capsule was torn in several areas and signs of chronic inflammation with the cartilage having been affected mildly could be observed. Implanted cartilage protected with PEC-encapsulation showed no signs of degeneration and significantly lower level of after effects of chronic inflammation than implanted cartilage without PEC-encapsulation. Therefore, it could be expected, that PEC membrane encapsulation offers a novel approach to protect cartilage implants from host response after autogenous transplantation.

Animals↗
PubMed2001

[Cartilage: from biomechanics to physical therapy].

OBJECTIVES: To review the current knowledge about the relationship between physical activities, cartilage biology, osteoarthritis and rehabilitation. METHOD: PubMed, Ovid, Cochrane Data base were interrogated for the period 1966-2000. Key words were: chondrocyte, cartilage, osteoarthritis, mechanical stimulation, exercises, physical therapy, rehabilitation. Were reviewed: the mechanical biology of the chondrocytes and the cartilage, the mechanisms of transduction, the metabolic response of the chondrocytes to mechanical stresses; the effects of physical activity and immobilization on the cartilage in animal models, the main studies on the epidemiology of limbs osteoarthritis and clinical trials on rehabilitation. RESULTS: In vitro studies have demonstrated that some molecules are involved in the transduction of mechanical stress into intracellular biological event. Chondrocytes and cartilage are sensitive to mechanical stress and cartilage extracellular matrix synthesis and degradation can be modulated by mechanical events. Applications of cyclic loads usually lead to an enhanced matrix synthesis while static loads usually decrease matrix production. In animal models, intensive physical activity or immobilization lead to cartilage alteration mimicking osteoarthritis. In human, intensive and prolonged physical activities are probably associated with hip and knee osteoarthritis. However, there is evidence that exercise therapy and continuous passive motion have beneficial effects on patients with knee or hip osteoarthritis. Fundamental and clinical studies are still needed to determine if exercise programs could have an effect on chondromodulation. Continuous passive motion could help, in the future, to better understand the relationship between mechanical stimulation and cartilage homeostasis. CONCLUSION: Rehabilitation could be beneficial in the therapeutic management of limbs osteoarthritis. The protocols of rehabilitation should however be more evaluated in controlled trials.

Activities of Daily Living↗
PubMed1982

The type of collagen made by the articular cartilage in joints of dogs with degenerative joint disease.

The collagen in the degenerated articular cartilage from dysplastic canine hip joints was characterized as to type by examining cartilage directly and also after labeling cartilage slices with 14C-proline in vitro. Collagen analysis was by sodium dodecylsulfate-polyacrylamide gel electrophoresis of 14C-labeled collagen, and of 14C-peptides which had been cleaved by cyanogen bromide. Amino acid analysis was done on hydrolysates of whole cartilage and of purified collagens to quantify the ratio of hydroxyproline to hydroxylysine. Data revealed that type II collagen was the radiolabeled product synthesized in all samples of degenerated cartilage and was the only collagen detected in biochemical tests in the cartilage of joints with degenerative joint disease as well as in disease free hip joints. Results suggested that chondrocytes in degenerated cartilage of canine joints did not switch their collagen phenotype, but continued to synthesize type II collagen. Cartilage degeneration in joints of dogs with hip dysplasia proceeded without a change in collagen phenotype.

Animals↗
PubMed2003

Measurement of the mechanical condition of articular cartilage with an ultrasonic probe: quantitative evaluation using wavelet transformation.

OBJECTIVE: To develop a new diagnostic technology to evaluate articular cartilage quantitatively by introducing an ultrasonic probe into the knee joint under arthroscopy and analyzing the A-mode echogram by means of wavelet transformation. DESIGN: Quantitative evaluation using comparison of two indices on the wavelet map and macroscopic evaluation using the Outerbridge classification. As the quantitative indices on the wavelet map, the maximum magnitude and the echo duration which was defined as the length of time that included 95% of echo signal were selected. BACKGROUND: Quantitative evaluation of articular cartilage in situ is required for new tissue-engineered cartilage but an evaluation system that fully meets this requirement has yet to be established for clinical use. METHODS: Human articular cartilage specimens were analyzed using an ultrasonic probe after macroscopic evaluation and the cartilage characteristics on the echo duration-maximum magnitude graph were examined. RESULTS: There were significant differences between grade 1 and 3, and grade 2 and 3 in the echo duration and maximum magnitude. The cartilage specimens had a L-shaped distribution in echo duration-maximum magnitude graph. CONCLUSIONS: The present study is the new quantitative evaluation system of the articular cartilage in situ and a clinical trial under arthroscopy is presently underway. The ultrasonic measurement is highly reproducible, so we can expect this system to be suitable for in situ reliable examination under arthroscopy. RELEVANCE: Precise evaluation of articular cartilage is of particular importance for longitudinal clinical trials for determination of best surgical option or effect of new chondroprotective drugs in arthritic disease and rheumatoid arthritis.

Adult↗
PubMed2002

Real-time ultrasound analysis of articular cartilage degradation in vitro.

The sensitivity of the reflection coefficient, attenuation and velocity to the enzymatic degradation of bovine patellar cartilage was evaluated in real-time with high-frequency ultrasound (US) (29.4 MHz). These parameters were estimated from the radiofrequency (RF) signal, which was recorded at 5-min intervals during the digestion of the tissue by collagenase or by trypsin. The coefficient of reflection at cartilage surface decreased by 78.5% and 10.5% (p < 0.05) after 6 h of exposure to collagenase and 4 h of exposure to trypsin, respectively. During the trypsin digestion, the attenuation in cartilage increased by 0.274 dB/mm (p < 0.05) and the velocity decreased by 7 m/s (p < 0.05). The coefficient of reflection at the cartilage surface was the most sensitive acoustic parameter to the enzymatic degradation of cartilage and may be the easiest to implement for clinical diagnosis of cartilage quality. US velocity was found to be insensitive to degradation. The small difference in mean velocity between the control and degraded cartilage suggests that a constant predefined US velocity value can be used to obtain diagnostically acceptable measurement of the cartilage thickness.

Animals↗
PubMed1998

Automatic three-dimensional reconstruction and characterization of articular cartilage from high-resolution ultrasound acquisitions.

Three-dimensional (3D) high-resolution ultrasonography has proved to be useful for in vitro assessment of cartilage remodeling due to osteoarthritis. The diagnosis is performed by computation of the mean thickness of the cartilage, which reveals hypertrophy or thinning, and by 3D reconstruction of the data, which provides essential information about the size, extent, and localization of the lesion. In both cases, preliminary segmention of the cartilage is necessary. This article proposes an algorithm for automatic segmentation of the cartilage from 3D ultrasonic acquisitions of the rat patella, which includes the detection of the cartilage surface and the cartilage/bone interface. The method was designed on the assumption of regularity and smoothness of the interfaces. The use of a global threshold was sufficient to separate the patella area from the background. The cartilage/bone interface was detected by selection of regions of interest (ROIs) encompassing the interface, followed by the detection of the interface within these ROIs using the graph theory. The method was applied to 162 samples. The detection accuracy was judged to be very good or good in 99% of the cases for the cartilage surface and in 86% of the cases for the cartilage/bone interface. The mean cartilage thickness value in the central part of the patella obtained from the automatic detection method was compared to that obtained manually. The coefficient of correlation between the two measurements was 0.92. These results show that our method is reliable. Thus, fast processing of a large number of acquisitions and a more complete analysis of the cartilage surface become possible.

Aging↗
PubMed2001

Degradation of the cartilage collagen matrix associated with changes in chondrocytes in osteoarthrosis. Assessment by loss of background fluorescence and immunodetection of matrix components.

Articular cartilage damage and eventual loss is the primary pathological change seen in osteoarthrosis (OA). In this study we have investigated the link between turnover of the collagen matrix and changes in chondrocytes. The background fluorescence of articular cartilage, as indicated by its emission spectrum and resistance to extraction was generated by the slow non-enzymic modification of the collagen matrix by advanced glycation end products (AGEs). Assessment of changes in background fluorescence in sections of articular cartilage provided a narrative of collagen degradation. Patients without OA pathology typically had a uniform strong background fluorescence throughout the depth of the cartilage. Cartilage from OA patients showed a range of changes in background fluorescence dependent on depth from the articular surface and proximity to overt lesions. Loss of background fluorescence was centered on chondrocytes, more extensive near the surface and associated with detection of the proteoglycan epitope 7D4. Expression of type X collagen was seen in articular cartilage in the region of the interface of with subchondral bone in most OA patients but was not associated with prominent, pericellular, loss of background fluorescence. These observations are consistent with progressive cartilage damage in OA, whereby collagen turnover and loss of surface integrity is associated with chondrocyte activity similar to that seen in immature articular cartilage.

Aged↗
PubMed2001

The effect of tibial lengthening using the Ilizarov method on the cartilage and the menisci of the knee joint.

In order to investigate possible acute damage to the knee joint cartilage and the menisci during tibial lengthening, sixteen young beagle dogs underwent 30% lengthening of the right tibia of 2.5 cm by callus distraction at a distraction rate of twice 0.5 mm per day. A further four dogs comprised the control group with fixator and osteotomy but without lengthening. After a distraction period of 25 days half the dogs were killed (group A) while the other half (eight dogs with limb lengthening and two dogs without) were killed after a further period of 25 days (group B). At the end of the study, the menisci were removed together with three cartilage-bone cylinders from both femoral condyles from the weight-bearing zones as well as from the corresponding tibial condyles. Serial sections from the menisci were stained with haematoxylin and eosin (H&E) and Elastica van Gieson. Sections of the cartilage-bone cylinders were stained with H&E and safranin-O. Cartilage thickness was measured and the glycosaminoglycan content of the joint cartilage was determined using microspectrophotometry. None of the histological preparations obtained from the untreated and distracted sides showed any signs of damage to the cartilage or to the menisci. There were no significant differences between cartilage thickness and proteoglycan content of the untreated side and the lengthened side. Thus, tibial lengthening using the llizarov method does not appear to cause acute damage to the cartilage of the knee joint or to the menisci.

Animals↗
PubMed2001

Chondrocyte necrosis and apoptosis in impact damaged articular cartilage.

A decrease in chondrocyte numbers is one characteristic of osteoarthritic cartilage. This decrease may be the result of apoptosis or other forms of cell death induced by mechanical damage. Furthermore, cell death may contribute to the structural and metabolic changes found in osteoarthritic cartilage. Therefore, we investigated cell viability and the mode of cell death in cartilage subjected to an increasing severity of impact loads expected to cause compositional damage and osteoarthritic-like metabolic alterations. Canine cartilage explants were subjected to cyclic indentation impacts of 5 megapascals at 0.3 Hz for 0, 2, 20, and 120 min and then kept in culture for 2, 4, 48, and 144 h. Cell death was assessed by the TUNEL assay and by uptake of propidium iodide. Viable cells were detected by the ability to metabolize fluorescein diacetate. Nuclear morphology and ultrastructure of the cell were examined using Hoechst 33342 fluorescent staining and transmission electron microscopy (TEM). As controls for necrosis and apoptosis, cartilage was, respectively, frozen and thawed or incubated with mitomycin-C, an apoptosis inducer. In cartilage that had been loaded for 2 h, 32% of the chondrocytes in the loaded core took up propidium iodide within 2 h after loading. Most of these were in the middle to superficial zones and reflected leaky cell membranes usually characteristic of necrosis. Less than 1% of these chondrocytes were positive in the TUNEL assay after 4 h. After additional culture for 2 days, however, the proportion of chondrocytes which were positive in the TUNEL assay reached 73%. A dose dependent response to duration of loading was detected with the TUNEL assay at this time. The TUNEL assay was not specific for apoptosis since 92% of chondrocytes in freeze/thawed cartilage were TUNEL positive. However, some cells with apoptotic bodies and chromatin condensation characteristic of apoptosis were found in the transition zone between necrotic and normal chondrocytes, but not in the superficial and upper zones, in impact damaged cartilage. We concluded that in this study, necrosis occurred first, followed by apoptosis.

Animals↗
PubMed2001

A decreased subchondral trabecular bone tissue elastic modulus is associated with pre-arthritic cartilage damage.

In osteoarthritis, one postulate is that changes in the mechanical properties of the subchondral bone layer result in cartilage damage. The goal of this study was to examine changes in subchondral trabecular bone properties at the calcified tissue level in the early stages of cartilage damage. Finite element models were constructed from microCT scans of trabectilar bone from the proximal tibia of donors with mild cartilage damage and from normal donors. In the donors with cartilage damage, macroscopic damage was present only in the medial compartment. The effective tissue elastic moduli were determined using a combination of finite element models and mechanical testing. The bone tissue modulus was reduced by 60% in the medial condyle of the cases with cartilage damage compared to the control specimens. Neither the presence of cartilage damage nor the anatomic site (medial vs. lateral) affected the elastic modulus at the apparent level. The volume fraction of trabecular bone was higher in the medial compartment compared to the lateral compartment of tibiae with cartilage damage (but not the controls), suggesting that mechanical properties were preserved in part at the apparent level by an increase in the bone volume fraction. It seems likely that the normal equilibrium between cartilage properties, bone tissue properties and bone volume fraction is disrupted early in the development of osteoarthritis.

Aged↗
PubMed2001

Integration of engineered cartilage.

The structure and function of cartilaginous constructs, engineered in vitro using bovine articular chondrocytes, biodegradable scaffolds and bioreactors, can be modulated by the conditions and duration of tissue cultivation. We hypothesized that the integrative properties of engineered cartilage depend on developmental stage of the construct and the extracellular matrix content of adjacent cartilage, and that some aspects of integration can be studied under controlled in vitro conditions. Disc-shaped constructs (cultured for 5+/-1 days or 5+/-1 weeks) or explants (untreated or trypsin treated cartilage) were sutured into ring-shaped explants (untreated or trypsin treated cartilage) to form composites that were cultured for an additional 1-8 weeks in bioreactors and evaluated biochemically, histologically and mechanically (compressive stiffness of the central disk, adhesive strength of the integration interface). Immature constructs had poorer mechanical properties but integrated better than either more mature constructs or cartilage explants. Integration of immature constructs involved cell proliferation and the progressive formation of cartilaginous tissue, in contrast to the integration of more mature constructs or native cartilage which involved only the secretion of extracellular matrix components. Integration patterns correlated with the adhesive strength of the disc-ring interface, which was markedly higher for immature constructs than for either more mature constructs or cartilage explants. Trypsin treatment of the adjacent cartilage further enhanced the integration of immature constructs.

Animals↗
PubMed2001

Mechanisms of chondrocyte adhesion to cartilage: role of beta1-integrins, CD44, and annexin V.

The initial adhesion of transplanted chondrocytes to surrounding host cartilage may be important in the repair of articular defects. Adhesion may position cells to secrete molecules that fill the defect and integrate repair tissue with host tissue. While chondrocytes are known to become increasingly adherent to cartilage with time, the molecular basis for this is unknown. The objective of this study was to investigate the role of beta1-integrin, CD44, and annexin V receptors in chondrocyte adhesion to cartilage. Chondrocytes were cultured in high density monolayer, released with trypsin, and allowed to recover in suspension for 2 h at 37 degrees C. Under these conditions, flow cytometry analysis showed that chondrocytes expressed beta1-integrins, CD44, and annexin V. In a rapid screening assay to assess chondrocyte adhesion to cartilage, cell detachment decreased from 79% at 10 min following transplantation to 10% at 320 min. Treatment of cells with a monoclonal antibody to block beta1-integrins significantly increased chondrocyte detachment from cartilage compared to untreated controls. Similarly, results from a parallel-plate shear flow adhesion assay showed that blocking beta1-integrins significantly increased chondrocyte detachment from cartilage compared to untreated controls at each level of applied shear (0-70 Pa). In both assays, treatment of cells with reagents that block CD44 (hyaluronan oligosaccharides or monoclonal Ab IM7) or annexin V (polyclonal Ab #8958) had no detectable effect on adhesion. With cartilage treated with chondroitinase ABC, blocking beta1-integrins also increased chondrocyte detachment, while blocking CD44 and annexin V also had no detectable effect. Under the conditions studied here, beta1-integrins appear to mediate chondrocyte adhesion to a cut cartilage surface. Delineation of the mechanisms of adhesion may have clinical implications by allowing cell manipulations or matrix treatments to enhance chondrocyte adhesion and retention at a defect site.

Animals↗
PubMed2002

Quantitative cartilage imaging of the human hind foot: precision and inter-subject variability.

Alterations of ankle cartilage are observed in degenerative and inflammatory joint disease, but cartilage cannot be directly visualized by radiography. The purpose of this study was therefore to analyze the feasibility and precision of quantitative cartilage imaging in the human hind foot (talocrural, talotarsal, and intertarsal joints), and to report the inter-subject variability for cartilage volume, thickness and surface areas. The feet of 16 healthy volunteers were imaged using a 3D gradient-echo magnetic resonance imaging sequence with water-excitation. After interpolation to a resolution of 1 x 0.125 x 0.125 mm3 the cartilage plates were segmented, and the cartilage volume, thickness, and surface areas determined. The precision (four repeated measurements) was examined in eight volunteers, the RMS average CV% being 2.1% to 10.9% in single joint surfaces, and < or = 3% for the cumulative values of all joints. The mean cartilage thickness ranged from 0.57+/-0.08 (navicular surface) to 0.89+/-0.19 mm (trochlear surface for tibia). In conclusion this study shows that it is feasible to quantify thin cartilage layers in the hind foot under in vivo imaging conditions, and that the precision errors are substantially smaller than the inter-subject variability in healthy subjects.

Adult↗
PubMed2003

Localization of insulin-like growth factor binding protein-2 in chondrocytes of bovine articular cartilage.

PURPOSE: Previous work indicated that transforming growth factor (TGF-beta) treatment of bovine articular cartilage resulted in an accumulation of insulin-like growth factor binding protein-2 (IGF-BP-2). The purpose of the work presented in this paper was to define the localization of the IGF-BP-2 in freshly excised articular cartilage and in slices cultured in the presence and absence of TGF-beta. METHOD: Newborn calf articular cartilage was dissected and immediately fixed or maintained in organ culture for five days under basal conditions (media without added serum or growth factors) or with basal media containing 15 ng/ml of TGF-beta1. Frozen or paraffin embedded sections were prepared, and immunohistochemistry using anti-IGF-BP-2 performed. RESULTS: The paraffin sections provided the best preservation of morphology and consistency of immunohistochemical staining patterns. In fresh cartilage slices, IGF-BP-2 was associated with most of the chondrocytes. The basal cultured cartilage showed positive immunostaining in some areas, but not others: the most consistently stained area was the upper radial zone. In all cases where a positive reaction was observed, it was associated mostly with chondrocytes. On the other hand, all the TGF-beta treated samples that were examined in this study were evenly stained, and most chondrocytes were positive in all areas from superficial to deep zones, thus closely resembling the pattern of fresh tissue. CONCLUSIONS: It is concluded that IGF-BP-2 is closely cell associated in bovine articular cartilage. Following culture of cartilage slices, TGF-beta increases the number of cells with positive immunostaining. These data help to support the postulate that TGF-beta exerts at least some of its actions in articular cartilage via cross-talk mechanisms involving the IGF-BP-2 system.

Animals↗