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PubMed2003

Cartilage morphogenetic proteins: role in joint development, homoeostasis, and regeneration.

BACKGROUND: Articular cartilage homoeostasis is critical for joint function. The steady state homoeostasis of articular cartilage is a balance between anabolic morphogens such as cartilage derived morphogenetic proteins (CDMPs) and bone morphogenetic proteins (BMPs) of the BMP family and catabolic cytokines such as interleukin (IL)1, IL17, and tumour necrosis factor alpha. Although bone and articular cartilage are adjacent tissues, there is a profound difference in their regeneration potential. Bone has the highest potential for regeneration. On the other hand, articular cartilage is recalcitrant to repair. OBJECTIVE: To examine the hypothesis that the feeble innate regeneration ability of cartilage is due to the preponderance of catabolic cytokines such as IL1 and IL17. RESULTS: During a systematic investigation of CDMPs and cytokines IL17B (chondroleukin) was found in bovine articular cartilage. DISCUSSION AND CONCLUSIONS: BMP-7 and IL17B are present in articular cartilage and synthesised in chondrocytes as shown by northern blots and real-time reverse transcription-polymerase chain reaction. The coexistence of anabolic morphogens and catabolic cytokines in articular cartilage has important implications for cartilage homoeostasis and regeneration. The networks of signalling systems of morphogens and cytokines determine the net capacity for regenerative morphogenesis of articular cartilage. Finally, the feeble innate capacity for articular cartilage may be improved by targeted therapy by soluble receptors to block catabolic cytokines.

Animals↗
PubMed2003

Articular cartilage lesions of the glenohumeral joint: diagnostic effectiveness of MR arthrography and prevalence in patients with subacromial impingement syndrome.

PURPOSE: To determine the prevalence of articular cartilage lesions in patients with subacromial impingement syndrome and to assess the diagnostic effectiveness of magnetic resonance (MR) arthrography in detecting such cartilage abnormalities. MATERIALS AND METHODS: MR arthrographic images obtained in 52 consecutive patients (mean age, 45.8 years; age range, 17-73 years; 26 male and 26 female patients) were retrospectively evaluated for glenohumeral cartilage lesions. Two experienced musculoskeletal radiologists who were blinded to the arthroscopy report independently analyzed the articular cartilage. Humeral and glenoidal cartilage were assessed separately. The lesions were graded as either subtle or marked. Arthroscopic findings were the standard of reference. Sensitivity, specificity, accuracy, and interobserver agreement were calculated. RESULTS: At arthroscopy, humeral cartilage lesions were found in 15 patients (frequency, 29%). Four lesions were subtle, and 11 were marked. Cartilage lesions of the glenoid were less frequent (eight patients; frequency, 15%): Three were subtle, and five were marked. For reader 1 and reader 2, respectively, sensitivity of MR arthrography for humeral cartilage lesions was 53% and 100%, specificity was 87% and 51%, and accuracy was 77% and 65%; sensitivity for glenoidal cartilage lesions was 75% and 75%, specificity was 66% and 63%, and accuracy was 67% and 65%. Interobserver agreement for the grading of cartilage lesions with MR arthrography was fair (humeral lesions, kappa = 0.20; glenoidal lesions, kappa = 0.27). CONCLUSION: Glenohumeral cartilage lesions are found in up to one third of patients referred for MR arthrography for subacromial impingement syndrome. The performance of MR arthrography in the detection of glenohumeral cartilage lesions is moderate.

Adolescent↗
PubMed1981

Adenosine 3',5'-monophosphate: a modulator of embryonic chick cartilage growth.

We tested the hypothesis that cyclic AMP plays a significant role in modulating the growth of embryonic chick cartilage by determining whether cyclic AMP levels change in growing embryonic cartilage and whether cyclic AMP could stimulate embryonic cartilage growth in a long term in vitro organ culture. Cyclic AMP levels were low (0.1 pmol/mg wet wt) in 8-d chick embryo pelvic cartilage, and increased progressively through the 11th d of embryonic development at which time they reached a maximum (1.8 pmol/mg wet weight) and thereafter remained constant. We developed an in vitro organ culture system to determine whether cyclic AMP, a factor known to stimulate radiolabeled precursor incorporation into macromolecules in short-term studies does, in fact, stimulate growth of cartilage. Individual pelvic cartilages were isolated from 9-d chick embryos, placed in serum-free medium (BGJb-FJ modification) and incubated for 3 to 5 d during which time they increased in size (39 and 60% in length, respectively), wet weight (90 and 141%, respectively), and content of total soluble protein (30 and 48%, respectively). N6-monobutyryl cyclic AMP (BtcAMP) added to the medium caused a dose-dependent (0.05 to 1.0 mM) stimulation of growth. After 3 d of incubation, 1.0 mM BtcAMP increased wet weight (125%), [14C]leucine incorporation into protein (75%), and [3H]thymidine incorporation into DNA (48%) compared with control cartilages incubated in medium alone. 1-methyl-3-isobutyl xanthine, a phosphodiesterase inhibitor, also increased cartilage growth above control while sodium butyrate, AMP, and ATP had no effect. Histological examination of cartilage grown in medium was similar to that of cartilage developing in ovo, whereas, cartilage grown in medium containing BtcAMP showed marked hypercellularity with many immature chondrocytes. Our observations are compatible with the hypothesis that cyclic AMP can significantly modulate the growth of embryonic cartilage.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Preferential mRNA expression of prostromelysin relative to procollagenase and in situ localization in human articular cartilage.

An imbalance between extracellular proteinases and their inhibitors is thought to underlie cartilage degradation. In cultures of adult cartilage, prostromelysin mRNA levels were much higher than those for procollagenase and this differential was increased in cultures stimulated with IL-1 beta. Analysis of mRNA prepared from freshly isolated chondrocytes showed abundant amounts of prostromelysin mRNA in normal adult cartilage but low levels in the neonate. Not all adult cartilage may possess such high levels of prostromelysin mRNA, as the message levels in the cartilage remaining on late-stage osteoarthritic joints were lower than those in normal adult cartilage. Relative to prostromelysin mRNA, little procollagenase and TIMP mRNA were found in the adult cartilage. In situ hybridization revealed that metalloproteinase mRNAs were localized in chondrocytes of the superficial zone in adult cartilage. However, upon IL-1 beta treatment, chondrocytes in all cartilage zones were observed to express prostromelysin mRNA. Relative to the neonate, the normal adult cartilage appears to have a high degradative potential, if one accepts that steady-state mRNA levels reflect prostromelysin production. As the adult cartilage is not apparently undergoing rapid turnover, it would appear that control of prostromelysin activation may be the major regulatory step in stromelysin-induced cartilage degradation.

Aged↗
PubMed2003

Tubes of vascularized cartilage used for replacement of rabbit cervical trachea.

This study was performed to evaluate the healing process of vascularized cartilage tubes after reconstruction of circumferential tracheal defects in rabbits. Vascularized cartilage was obtained by applying ear cartilage to a vascularized fascia flap in the lateral thoracic area in 10 animals. Five animals (control group) were used to evaluate the viability of the vascularized cartilage after 2 weeks. Circumferential tracheal defects were reconstructed in 5 animals by means of tubes of vascularized cartilage with preservation of the established blood supply around the grafts. The experimental animals were followed until signs of dyspnea became apparent. After follow-up and euthanasia, cartilage viability and regeneration of respiratory epithelium were evaluated. A viable plate of cartilage that was intensely attached to the vascularized fascia flap was found in the control animals. The animals from the experimental group showed dyspnea after a mean follow-up period of 22.6 days because of cartilage necrosis with loss of airway support. Cartilage graft revascularization and remucosalization were limited to 18.1% of the initial surface area of the cartilage tube. Mucosal coverage was seen at the anastomoses, whereas the middle part of the cartilage tube underwent necrosis. We conclude that tubes of autologous cartilage show problematic healing when placed inside the airway. Migration of vascularized connective tissue, migration of respiratory epithelium, and preservation of the viability of the cartilaginous graft were limited to a short segment at the anastomotic sites.

Animals↗
PubMed2006

Decreased metalloproteinase production as a response to mechanical pressure in human cartilage: a mechanism for homeostatic regulation.

Articular cartilage is optimised for bearing mechanical loads. Chondrocytes are the only cells present in mature cartilage and are responsible for the synthesis and integrity of the extracellular matrix. Appropriate joint loads stimulate chondrocytes to maintain healthy cartilage with a concrete protein composition according to loading demands. In contrast, inappropriate loads alter the composition of cartilage, leading to osteoarthritis (OA). Matrix metalloproteinases (MMPs) are involved in degradation of cartilage matrix components and have been implicated in OA, but their role in loading response is unclear. With this study, we aimed to elucidate the role of MMP-1 and MMP-3 in cartilage composition in response to mechanical load and to analyse the differences in aggrecan and type II collagen content in articular cartilage from maximum- and minimum-weight-bearing regions of human healthy and OA hips. In parallel, we analyse the apoptosis of chondrocytes in maximal and minimal load areas. Because human femoral heads are subjected to different loads at defined sites, both areas were obtained from the same hip and subsequently evaluated for differences in aggrecan, type II collagen, MMP-1, and MMP-3 content (enzyme-linked immunosorbent assay) and gene expression (real-time polymerase chain reaction) and for chondrocyte apoptosis (flow cytometry, bcl-2 Western blot, and mitochondrial membrane potential analysis). The results showed that the load reduced the MMP-1 and MMP-3 synthesis (p < 0.05) in healthy but not in OA cartilage. No significant differences between pressure areas were found for aggrecan and type II collagen gene expression levels. However, a trend toward significance, in the aggrecan/collagen II ratio, was found for healthy hips (p = 0.057) upon comparison of pressure areas (loaded areas > non-loaded areas). Moreover, compared with normal cartilage, OA cartilage showed a 10- to 20-fold lower ratio of aggrecan to type II collagen, suggesting that the balance between the major structural proteins is crucial to the integrity and function of the tissue. Alternatively, no differences in apoptosis levels between loading areas were found--evidence that mechanical load regulates cartilage matrix composition but does not affect chondrocyte viability. The results suggest that MMPs play a key role in regulating the balance of structural proteins of the articular cartilage matrix according to local mechanical demands.

Aged↗
PubMed1997

Stimulation of proteoglycan synthesis in explants of porcine articular cartilage by recombinant osteogenic protein-1 (bone morphogenetic protein-7).

UNLABELLED: Osteogenic protein-1 (also known as bone morphogenetic protein-7) is a member of the bone morphogenetic protein family. Bone morphogenetic proteins and related members of the TGF-beta (transforming growth factor-beta) superfamily are involved in the development and repair of bone. Recombinant bone morphogenetic proteins induce the formation of new cartilage and bone at heterotopic sites. We investigated the influence of recombinant osteogenic protein-1 (at doses of three, ten, thirty, or 100 nanograms per milliliter) on the synthesis and release of proteoglycans and the maintenance of a steady-state concentration of proteoglycans in explants of porcine articular cartilage that were maintained in chemically defined serum-free medium. We found a dose-dependent stimulation of proteoglycan synthesis and a concurrent decrease in the rate of release of proteoglycans from the explants. The size of the proteoglycan monomers and the composition of the glycosaminoglycan chains in the untreated articular cartilage were similar to those in the articular cartilage treated with osteogenic protein-1. The capacity of the newly synthesized proteoglycan monomers to form aggregates with exogenous hyaluronic acid was found to be similar to that of proteoglycans in bovine nasal cartilage. Our results demonstrated that osteogenic protein-1 stimulated the synthesis of proteoglycans and diminished the release of proteoglycans from explants of porcine articular cartilage. CLINICAL RELEVANCE: The maintenance and repair of articular cartilage is a formidable challenge in clinical orthopaedics. The stimulation of proteoglycan synthesis by osteogenic protein-1 (bone morphogenetic protein-7) in explants of cartilage maintained in chemically defined serum-free medium implies that recombinant osteogenic protein-1 may play a role in the maintenance of a steady-state concentration of proteoglycans in articular cartilage, a desirable prerequisite for optimum repair of cartilage. Osteogenic protein-1 can initiate the formation of cartilage from mesenchymal cells. Once new cartilage has formed at the site of repair, osteogenic protein-1 also may maintain the synthesis of proteoglycans.

Animals↗
PubMed2000

Repair of articular cartilage defects one year after treatment with recombinant human bone morphogenetic protein-2 (rhBMP-2).

BACKGROUND: Damaged articular cartilage has a limited ability to repair. Operative removal of damaged cartilage and penetration into the subchondral bone to allow population of the defect with progenitor cells can result in filling of the defect with repair tissue. However, this repair tissue often degenerates over time because of its inability to withstand the mechanical forces to which it is subjected. We previously reported that recombinant human bone morphogenetic protein-2 (rhBMP-2) improves the repair of full-thickness defects of cartilage as long as six months postoperatively. We have now extended that study to examine the quality of the repair tissue at one year. METHODS: Full-thickness defects of cartilage were created in the trochlear groove of twenty-five adult New Zealand White rabbits. Eight defects were left empty, eight were filled with a collagen sponge, and nine were filled with a collagen sponge impregnated with five micrograms of rhBMP-2. The animals were killed at fifty-two weeks postoperatively, and the gross appearance of the healed defect was assessed. The repair tissue was examined histologically and was evaluated, according to a grading scale, by four individuals who were blinded with respect to the treatment. The tissue sections were immunostained with antibodies against type-I collagen, type-II collagen, aggrecan, and link protein. The residence time of the rhBMP-2 in the cartilage defect was evaluated in vivo with use of scintigraphic imaging of radiolabeled protein. RESULTS: One year after a single implantation of a collagen sponge containing five micrograms of rhBMP-2, the defects had a significantly better histological appearance than the untreated defects (those left empty or filled with a collagen sponge). The histological features that showed improvement were integration at the margin, cellular morphology, architecture within the defect, and reformation of the tidemark. The total scores were also better for the defects treated with rhBMP-2 than for the untreated defects, but in no instance was the repair tissue identical to normal articular cartilage. The thickness of the cartilage in the defects treated with rhBMP-2 was 70 percent that of the normal cartilage, an observation that was identical to that at twenty-four weeks postoperatively. Immunostaining demonstrated significantly less type-I collagen in the defects treated with rhBMP-2 than in the untreated defects. Immunostaining for other matrix components showed no difference among the treatment groups. The mean residence time of rhBMP-2 in the cartilage defects was eight days with an elimination half-life of 5.6 days. Detectable amounts of rhBMP-2 were present as long as fourteen days after implantation. CONCLUSIONS: The problems associated with operative repair of cartilage include the formation of fibrocartilage rather than normal articular cartilage and the degeneration of that repair tissue over time. Our results demonstrate that the addition of rhBMP-2 to the operative site after creation of a full-thickness defect results in an improvement in the histological appearance and composition of the extracellular matrix at one year postoperatively. If these experimental results translate directly to the clinical situation, it is possible that the addition of rhBMP-2 to existing operative treatments for the repair of cartilage may improve the repair process and may help to maintain the integrity of the repair tissue.

Animals↗
PubMed1992

Width of the articular cartilage of the hip: quantification by using fat-suppression spin-echo MR imaging in cadavers.

OBJECTIVE: Use of MR imaging to measure the width of the articular cartilage has not been thoroughly investigated. The value of a selective fat-suppression spin-echo sequence in the quantitative assessment of articular cartilage of the hip was studied in cadavers. MATERIALS AND METHODS: Sagittal and coronal images were acquired in 10 cadaveric hips (age range at time of death, 62-81 years). On the coronal and sagittal MR images that were closest to the center of the femoral head, marks were placed every 30 degrees, with the midpoint of the femoral head used as a reference. Cartilage thickness was measured in 123 resulting locations. Sixty-three positions included both femoral and acetabular cartilages, and 60 positions included femoral cartilage without an acetabular counterpart. The findings were compared with corresponding anatomic sections. RESULTS: For the 60 locations containing only femoral cartilage, significant correlation between MR and anatomic sections was found (Pearson correlation coefficient = .34, p = .0089). Of the 63 locations containing both femoral and acetabular cartilages, the two cartilage layers could be differentiated on the MR images in 50 locations. In these 50, the MR and anatomic measurements of the femoral cartilage correlated significant (r = .58, p less than or equal to .0001). Measurements of the acetabular cartilage in these 50 locations yielded no significant correlation (r = .25, p = .08). When the entire cartilage (femoral plus acetabular) was measured in all 63 locations, the correlation between MR and anatomic measurements was .29 (p = .02). The correlation coefficients obtained in this investigation indicate considerable scattering of the data. CONCLUSION: Our results show that measurements of articular cartilage thickness of the hip on fat-suppression spin-echo MR images are not sufficiently accurate to be of clinical value.

Aged↗
PubMed1976

Nutrition and somatomedin. II. Serum somatomedin activity and cartilage growth activity in streptozotocin-diabetic rats.

Since diabetes mellitus is a condition in which poor growth occurs despite elevation of plasma GH, we have attempted to determine if poor growth in diabetes, as in malnutrition, could be associated with a decrease in somatomedin activity. Young male rats were rendered diabetic with intravenous streptozotocin (STZ). The growth activity of their cartilage was estimated by 35SO4 incorporation in vitro, and somatomedin (SM) activity in their serum was determined by the stimulation of SO4 incorporation by cartilage from hypophysectomized rats or normal young pigs. Cartilage growth activity was significantly decreased 24 hours after STZ and fell to hypopituitary levels after 48 hours. The decreased growth activity could not be attributed to decreased cartilage responsiveness to SM, since incubation of diabetic cartilage with normal rat serum (normal SM) resulted in significant stimulation of cartilage SO4 incorporation. SM in diabetic serum decreased to hypopituitary levels 24 hours after STZ, and decreased further after 48 hours. The decrease in SM and cartilage growth activity was not prevented by the administration of high doses of bovine GH. The fall in bioassayable SM appeared to be due in part to the presence of an SM inhibitor in the diabetic serum, since addition of diabetic serum to normal serum decreased to measurable SM in the normal serum. Administration of insulin to diabetic rats 48 hours after STZ led to significant increases in SM and cartilage growth activity, and insulin therapy 24 hours after STZ prevented the decreases in SM and cartilage growth activity which occurred without insulin. Thus, acute STZ-induced diabetes in rats was associated with a significant decrease in both serum SM and cartilage growth activity; these changes were not ameliorated by administration of GH, and insulin therapy could both prevent and reverse the fall in SM and cartilage growth activity. From these observations, we conclude that (1) that fall in somatomedin activity and cartilage growth activity associated with STZ-induced diabetes appears to be due to insulin deficiency and (2) growth failure in diabetes, as in malnutrition, may be due to decreased somatomedin activity.

Animals↗
PubMed1989

Proteoglycan synthesis in vitamin D-deficient cartilage: recovery from vitamin D deficiency.

Vitamin D appears to be required for mineralization of skeletal elements. There is also evidence that cartilage proteoglycans may be involved in the regulation of mineralization. Previous studies have shown an alteration in the structure of the proteoglycans of the epiphyseal growth cartilage as a result of the decrease in serum calcium related to deficiency of dietary vitamin D. Vitamin D deficiency also induces a thickening of the epiphyseal growth plate presumably because of the inhibition of maturation of the growth plate chondrocytes. In order to compare the effect on proteoglycan structure with that on growth plate morphology, the proteoglycans of healing epiphyseal cartilage were characterized. The results indicate that, consistent with previous data, in vitamin D-deficient hatching chicks, the proteoglycans of the growth cartilage, but not of the articular cartilage, are smaller in monomer size with slightly smaller chondroitin sulfate chains whose sulfation pattern is unaltered. Sternal cartilage proteoglycans are unaffected. During recovery from vitamin D deficiency, the proteoglycans isolated from the growth cartilage are still not completely normal one day after supplementation with vitamin D, but are indistinguishable from normal by four days. In addition, the results conflict with those of a previous study in which only growth cartilage of hatchling chicks, not sternal or articular cartilage, was reported to synthesize large proteoglycans. Instead, all of these cartilages in the normal chicken have been found in this study to produce large proteoglycans of a size typical for mammalian cartilage and embryonic chick cartilage.

24,25-Dihydroxyvitamin D 3↗
PubMed1992

Isolation and characterization of an abundant elastase inhibitor from NaCl extracts of bovine nasal septa and articular cartilage.

Extracts of cartilage have been reported to inhibit many serine proteinases and metalloenzymes. Such inhibition may be important in protecting cartilage against degradation by chondrocytic proteinases such as collagenase, stromelysin and by leukocytic proteases, such as elastase. We report here isolation and partial characterization of a 17-kD elastase inhibitor from 0.5 M NaCl extracts of both nasal septum cartilage and articular cartilage, which inhibits elastase and represents 0.08% of the weight of nasal cartilage and 0.002% of the weight of articular cartilage. The protein was highly specific for elastase and did not inhibit cartilage metalloproteinases, suggesting that it may be mainly directed toward protecting cartilage against leukocytic proteases. The inhibitor had a blocked amino-terminus, was high in serine and glycine and lacked carbohydrate. The ease with which the inhibitor was extracted from cartilage suggests that it may function in vivo as a highly abundant elastase inhibitor which is secreted into synovial fluid from cartilage. The inhibitor was shown to be synthesized by bovine articular cartilage in explant culture and nearly all of the metabolically labeled material was secreted into the culture media. The inhibitor cross-reacted with polyclonal antibodies to bovine neck ligament alpha-elastin and antibodies to the inhibitor reacted with bovine neck ligament elastin. The properties of this inhibitor are different than those of any other reported cartilage derived inhibitor.

Amino Acids↗
PubMed1995

[An immunohistochemical study on fetal mouse condylar cartilage].

Mandibular condylar cartilage is considered as one of the growth cartilages, but it represents many distinct features. Collagens in cartilage matrix consist mainly of type II collagen but lack type I collagen. Recently it is reported that condylar cartilage contained both type I and type II collagens, while type I collagen was lacking in growth plate cartilages of adult rat tissue. In order to investigate whether such difference in matrix collagen exists in the embryonic period, an immunohistochemical study of type I and type II collagen was performed on fetal mouse condylar cartilage and compared to the limb bud cartilage (tibial anlage). When the first appearance of condylar cartilage was recognized at the 15th day of gestation, reaction to anti-type I collagen was detected in the cartilage matrix, while reaction to anti-type II collagen was very faint. After the 16th day, the pattern of immunohistochemical reaction was almost the same as that after birth. These observations of fetal condylar cartilage were completely different from those of limb bud cartilage. These results suggest that the abilities of the condylar cartilage and the limb bud to synthesize matrix collagen are different from the embryonic period.

Animals↗
PubMed2005

Relationship of chondrocyte apoptosis to matrix degradation and swelling potential of osteoarthritic cartilage.

BACKGROUND AND PURPOSE: Softening of cartilage is the initial degenerative step of osteoarthritic cartilage by matrix degradation and corruption of interconnection of the collagen fibrillar network. The purpose of this study was to investigate the correlation of chondrocyte apoptosis, matrix degradation, and the corruption of collagen architecture in the development of severe swelling of osteoarthritic cartilage. METHODS: Twenty osteoarthritic and 7 normal femoral neck fractured cartilage samples were obtained from patients with knee osteoarthritis and normal patients with femoral neck fracture at the time of total hip joint replacement surgery. Apoptosis was verified by TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick end-labeling) staining and structural changes were observed under phase-contrast microscopy. Matrix degradation was evaluated by histochemical analysis of proteoglycans. Swelling tests were performed by immersing the cartilage slices in hypotonic solution. The results of ultrastructural study of collagen architecture of osteoarthritic cartilage performed by scanning electron microscopy before and after swelling were compared. RESULTS: Matrix degradation was most prominent in the middle zone of osteoarthritic cartilage. The percentage of chondrocytes in osteoarthritic cartilage showing apoptosis ranged from 15 to 20% (average, 18%; standard deviation (SD) = 3.2%) and was correlated with the extent of structural changes and matrix degradation. The swelling strain of the osteoarthritic cartilage varied from 120 to 200% (average, 160%; SD = 40%) depending on the degree of matrix degradation and structural changes. The loss of interconnectivity of collagen fibrillar architecture was correlated with the increased swelling potential of osteoarthritic cartilage. CONCLUSION: This study demonstrated that chondrocyte apoptosis was correlated with matrix degradation and the corruption of fibrillar architecture and that the extent of these manifestations correlated with the swelling potential of osteoarthritic cartilage. These findings also emphasize the importance of the fibrillar architecture in maintaining the mechanical properties of cartilage.

Aged↗
PubMed1992

Local changes in proteoglycan synthesis during culture are different for normal and osteoarthritic cartilage.

Proteoglycan synthesis of mild-to-moderate osteoarthritic human knee cartilage was compared with that of normal cartilage of the same donor. Immediately after cartilage was obtained, the synthesis rate of proteoglycans was higher for osteoarthritic cartilage than for normal cartilage. Proteoglycan synthesis was then located, for both normal and osteoarthritic cartilage, in the middle and deep zone. However, after 4 days of culture, proteoglycan synthesis rate was higher for normal cartilage than for osteoarthritic cartilage. The reason for this transition from a lower to a higher proteoglycan synthesis rate was a strong increase in the proteoglycan synthesis in the superficial zone of normal cartilage. This was not observed for the osteoarthritic cartilage. The chondrocytes in the superficial zone of osteoarthritic cartilage, in contrast to normal cartilage, were mainly joined in cell clusters and proliferating. This may explain their inability to contribute to proteoglycan synthesis.

Aged↗
PubMed1988

Effects of polypeptide growth factors on mandibular condylar cartilage of the rat in vitro.

In a comparative study, the influence of several polypeptide growth factors on proliferation and matrix synthesis in secondary mandibular condylar and primary costal cartilage of the rat were determined using a serum-free culture system. Somatomedin-C, multiplication-stimulating activity (MSA), epidermal growth factor (EGF) and insulin had a significant dose-dependent stimulating effect on proliferation in mandibular condylar cartilage. In costal cartilage, the same factors as well as parathyroid hormone (fragment 1-34), platelet-derived growth factor (PDGF) and high doses of human growth hormone (1 microgram/ml) significantly stimulated proliferation. Matrix synthesis in both cartilages could only be stimulated by high doses of insulin (100 micrograms/ml) and in costal cartilage also by parathyroid hormone. In this culture system fibroblast growth factor reduced proliferation and matrix production, while cartilage-derived factor had no marked effect on the growth processes in both cartilage types. Prominent differences between condylar and costal cartilage were demonstrated by the effects of parathyroid hormone and fetal calf serum. Although the effects on matrix synthesis were very moderate in the tissue culture system used, this study demonstrates that most factors conducive to growth in primary cartilage also stimulate growth in condylar cartilage only exposure to growth substances that interfere with the differentiation of prechondroblasts into chondroblasts, a process that is specific for appositionally growing secondary cartilage, may result in different responses between primary and secondary cartilage.

Animals↗
PubMed1986

Degradation of cartilage in contact with soft tissue.

Observations have been made on histological changes in femoral-head articular cartilage transplanted into soft tissue in rats under a variety of conditions. Articular cartilage was implanted either whole or minced. Implants were made into deflated subcutaneous air pouches with or without an inflammatory irritant and into normal subcutaneous tissue. Cartilage-matrix loss occurred in four patterns: marginal zone encroachment, loss of metachromatic staining without loss of tissue mass, surface invasion and lacunar enlargement and coalescence. The presence of an inflammatory reaction had no discernible effect on loss of cartilage matrix. Changes at the marginal zone preceded changes at the centre. Loss of metachromatic staining without loss of tissue mass occurred in areas of chondrocyte death. Surface invasion was not affected by the viability of the underlying chondrocytes. Surface invasion occurred earliest in cartilage transplanted into subcutaneous tissue, and latest in cartilage implanted into air pouches inflamed with carrageenan. The onset of surface invasion appeared to be dependent on soft-tissue adhesion to the cartilage surface. Mincing of cartilage was associated with an increase in surface invasion in the deeper cartilage zone with large lacunae but not in the superficial zone with small lacunae. Occasional cut surfaces showed outgrowth of new cartilage matrix. These observations on artefactual modes of cartilage degradation may assist in analysing the critical steps in cartilage degradation in arthritic joints.

Air↗
PubMed1980

Cartilage-associated collagenolytic activity in rabbits with antigen-induced chronic synovitis.

Rabbit articular cartilage fragments from knees with normal and antigen-induced chronic synovitis were assayed for active and latent collagenolytic activity. Significant levels of latent collagenolytic activity, as measured by hydroxyproline release, were associated with cartilage from chronic synovitis knee cartilage but not from normal knee cartilage. Neither normal nor chornic synovitis knee cartilage contained demonstrable levels of spontaneously active cartilage-associated collagenolytic activity. Cartilage-associated latent collagenolytic activity was demonstrated only after activation with either trypsin or p-aminophenylmercuric acetate and was inhibited by EDTA (10(-2)M) and 1,10-phenanthroline (10(-3) M). Cartilage-associated latent collagenolytic activity was demonstrated after incubation of activated cartilage at 37 degrees C but not 4 degrees C. The activity could not be removed or diminished by extensive prewashing of these cartilage fragments. Treatment of rabbits undergoing development of antigen-induced chronic synovitis, with methylprednisolone (1 mg/kg/day), significantly suppressed the level of cartilage-associated collagenolytic activity in antigen-challenged knees. The measurement of cartilage-associated collagenolytic activity may be useful for the evaluation of potential antirheumatic drugs.

Animals↗