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PubMed2000

[Control genes of chondrocyte apoptosis in osteoarthritic articular cartilage].

OBJECTIVE: To investigate the expression of bax and bcl-2 in normal human articular chondrocytes and in osteoarthritic articular cartilage. METHODS: The samples of articular cartilage were obtained from 9 patients and 6 normal subjects. Bax and bcl-2 mRNA were detected by reverse transcriptase/polymerase chain reaction (RT-PCR) and their expression proteins were analyzed immunohistochemically. TUNEL technique was used to study apoptosis in situ. RESULTS: Bax and bcl-2 mRNA was detectable in chondrocytes of both osteoarthritic and normal cartilage. Bax mRNA of chondrocytes from patients with osteoarthritis (OA) was overexpressed compared with the normal controls (P < 0.01), and OA cartilage chondrocyte also expressed more bcl-2 mRNA than the controls (P < 0.05). There was no statistically significant difference of bax/bcl-2 between the two groups. Immunohistochemical staining demonstrated the same level of bax and bcl-2 proteins as their mRNA. A greater proportion of apoptotic chondrocytes were found in the OA cartilage than that in normal controls (4% - 14% versus 0 - 2%). CONCLUSIONS: Our results suggested that chondrocyte apoptosis was co-regulated by both bax and bcl-2. The ratio of bax to bcl-2 may contribute not only to the lower percentage of apoptotic chondrocytes, but also to the chronic pathologic process in OA.

Adult↗
PubMed2005

Tonic activation of hypoxia-inducible factor 1alpha in avascular articular cartilage and implications for metabolic homeostasis.

OBJECTIVE: To determine whether oxygen-dependent activation patterns of hypoxia-inducible factor 1alpha (HIF-1alpha) observed in vascularized tissues are conserved within avascular and hypoxic articular cartilage and whether HIF-1alpha affects cartilage matrix synthesis. METHODS: Explants of bovine articular cartilage and primary chondrocytes were exposed to normoxia (21% O2), hypoxia (2% O2), and simulated hypoxia (21% O2 plus CoCl2). Western blot and immunofluorescence analyses of HIF-1alpha were performed to determine HIF-1alpha activation patterns. To simulate cartilage loss from disease or injury, the top layers of cartilage were removed from osteochondral explants, and the residual cartilage was assessed for HIF-1alpha immunolocalization and proteoglycan synthesis. RESULTS: We demonstrated continuous nuclear translocation of HIF-1alpha in deeper layers of intact articular cartilage. HIF-1alpha was not completely degraded in chondrocytes exposed to normoxia, but rather, colocalized to the Golgi complex, a finding not previously reported for any cell type. Following alteration of the oxygen gradient by removal of the top layers of cartilage, predominantly perinuclear HIF-1alpha was found in the deeper layers. Restoration of intranuclear HIF-1alpha to these areas was achieved by hypoxia and simulated hypoxia. Under conditions in which HIF-1alpha was inactivated, matrix synthetic activity was altered (P < 0.0001) compared with control cartilage. CONCLUSION: These findings demonstrate that hypoxia-dependent activation of HIF-1alpha is highly conserved and that changes in oxygen tensions following cartilage loss from injury or disease alter cartilage metabolism in part by changing HIF-1alpha activity. The discovery of tonic activation of HIF-1alpha within intact articular cartilage underscores its potential importance to cartilage homeostasis.

Animals↗
PubMedDate not supplied

A system for grading articular cartilage lesions at arthroscopy.

Although there are several different classification systems for the description of articular cartilage damage, each has certain limitations and deficiencies which can lead to confusion. We are proposing a new system which describes articular cartilage abnormalities in simple terms. It is based on four separate and distinct variables: the description of the articular surface, the extent (depth) of involvement, the diameter of the lesion, and the location of the lesion. Although somewhat qualitative and subjective, the system enables the surgeon to record observed articular cartilage changes. We have used this grading as part of our overall knee rating system and have found it helpful in comparing treatment results between our different studies. For research purposes, a point scaling system facilitates computerization and statistical analysis of the data.

Arthroscopy↗
PubMed1994

Articular cartilage thickness and glycosaminoglycan distribution in the young canine knee joint after remobilization of the immobilized limb.

The recovery of articular cartilage from atrophy induced by joint immobilization was investigated in immature dogs. In a previous study, we showed that 11 weeks of immobilization of the knee (stifle) joint of young dogs reduced the concentration of articular cartilage glycosaminoglycans (GAGs) by 13-47%. In the present study, right hindlimbs from six female beagles were immobilized for 11 weeks, as in the previous study, and then were remobilized for 15 weeks. Cartilage from the knee joint was compared with cartilage from nonimmobilized knees of eight age-matched control beagles. Histological samples taken from 11 different locations of the knee joint were stained with safranin O, and microspectrophotometry was used to demonstrate distribution of GAGs in the tissue. After remobilization, GAG concentration was restored in the patellofemoral region and tibial condyles. On the summits of the femoral condyles, and especially at the periphery of the femoral condyles, GAG concentration remained 8-26% less than the control values. On the summits, the thickness of the uncalcified cartilage was as much as 15% less than in the age-matched controls. Consequently, the changes induced by unloading were reversible to a great extent, but a full restoration of articular cartilage was not obtained at all sites of the knee joint within the 15 weeks of remobilization. Immobilization of the skeletally immature joint therefore may affect the development of articular cartilage in such a way that very slow recovery or permanent alterations are induced.

Animals↗
PubMed2003

Osteoarthritis-like changes and decreased mechanical function of articular cartilage in the joints of mice with the chondrodysplasia gene (cho).

OBJECTIVE: To investigate whether heterozygosity for a loss-of-function mutation in the gene encoding the alpha1 chain of type XI collagen (Col11a1) in mice (chondrodysplasia, cho) causes osteoarthritis (OA), and to understand the biochemical and biomechanical effects of this mutation on articular cartilage in knee and temporomandibular (TM) joints. METHODS: Articular cartilage from the knee and TM joints of mice heterozygous for cho (cho/+) and their wild-type littermates (+/+) was examined. The morphologic properties of cartilage were evaluated, and collagen fibrils were examined by transmission electron microscopy. Immunohistochemical staining was performed to examine the protein expression levels of matrix metalloproteinase 3 (MMP-3) and MMP-13 in knee joints. In 6-month-old animals, fixed-charge density was determined using a semiquantitative histochemical method, and tensile stiffness was determined using an osmotic loading technique. RESULTS: The diameter of collagen fibrils in articular cartilage of knee joints from heterozygous cho/+ mice was increased relative to that in control cartilage, and histologic analysis showed OA-like degenerative changes in knee and TM joints, starting at age 3 months. The changes became more severe with aging. At 3 months, protein expression for MMP-3 was increased in knee joints from cho/+ mice. At 6 months, protein expression for MMP-13 was higher in knee joints from cho/+ mice than in joints from their wild-type littermates, and negative fixed-charge density was significantly decreased. Moreover, tensile stiffness in articular cartilage of knee joints from cho/+ mice was moderately reduced and was inversely correlated with the increase in articular cartilage degeneration. CONCLUSION: Heterozygosity for a loss-of-function mutation in Col11a1 results in the development of OA in the knee and TM joints of cho/+ mice. Morphologic and biochemical evidence of OA appears to precede significant mechanical changes, suggesting that the cho mutation leads to OA through a mechanism that does not initially involve mechanical factors.

Animals↗
PubMed1991

[MRI evaluation of the patellar articular cartilage in patients with subluxation of the patella].

In patients with subluxation of the patella, injury of the patellar articular cartilage is frequently observed and correct evaluation is important to manage these patients. We examined 11 patients with subluxation of the patella and five normal volunteers. In 12 patellofemoral joints of seven patients with subluxation of the patella, the abnormalities observed on MRI were compared with those on arthroscopy and/or at operation. MRI was performed with a Magnetom 1.5 T (Siemens) using the round surface coil. Pulse sequences were SE (TR 400 ms/TE 19 ms), FLASH (TR 320 ms/TE 15 ms FA 90 degrees and 40 degrees), and SE (TR 2000 ms/TE 26, 70 ms). We analysed MR findings of the 12 abnormal joints and 10 normal joints according to the following classification of abnormalities observed on arthroscopy. (1) normal appearance (n = 3 joints), (2) softening and fibrillation (n = 6), (3) fragmentation (n = 3), and (4) erosion to bone (n = 0). In only one of the six cases with softening and fibrillation observed on arthroscopy, MRI could visualize the thickening of patellar articular cartilage, but in all three cases with fragmentation observed on arthroscopy, MRI could visualize the thin inhomogenous cartilage with irregular surface. The combination of SE (TR 400 ms/TE 19 ms) and FLASH (TR 320 ms/TE 15 ms FA 90 degrees) are extremely effective pulse sequence to detect the abnormalities of patellar articular cartilage. We conclude that MRI is a useful noninvasive method of detecting advanced changes in patellar articular cartilage.

Adolescent↗
PubMed2005

Multirater agreement of arthroscopic grading of knee articular cartilage.

BACKGROUND: Acute and chronic cartilage injury of the knee has an important impact on prognosis. The validity of the classification of such injuries is critical for prospective multicenter studies. The agreement among multiple surgeons at different institutions for articular cartilage lesions has not been established. HYPOTHESIS: Arthroscopic classification of articular cartilage lesions is reliable and reproducible and can be used for multicenter studies involving multiple surgeons. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 1. METHODS: A total of 6 surgeons from 5 centers reviewed 31 videos of articular cartilage lesions. With grade 2 and grade 3 combined for the analysis, observed agreement ranged from 81% to 94%, and kappa ranged from 0.34 to 0.87. An additional 22 videos comprising grade 2 and grade 3 lesions were analyzed, and the observed agreement was 80%, with an overall kappa of 0.47. CONCLUSION: Arthroscopic grading of articular cartilage lesions is reproducible among surgeons at different centers. CLINICAL RELEVANCE: Articular cartilage lesions can be reliably classified among surgeons at different sites. Such reliability is important for multicenter clinical research studies involving arthroscopic knee surgery.

Arthroscopy↗
PubMed2005

Inorganic pyrophosphate (PPI) in pathologic calcification of articular cartilage.

Physiologic levels of extracellular PPi, which suppresses hydroxyapatite crystal growth, must be maintained by articular chondrocytes and resident cells in many othee tissues in order to prevent pathologic calcification. However, extracellular PPi rises in articular cartilage in direct association with aging. Matrix supersaturation with PPi stimulates chondrocalcinosis manifesting as calcium pyrophosphate dihydrate (CPPD) crystal deposition. Extracellular PPi levels are normally held in check by balances in PPi generation by nucleotide pyrophosphatase phosphodiesterase (NPP/NTPPPH) activity relative to PPi degradation by pyrophosphatases, by balance effects of cytokines and growth factors, and by transport of PPi from the cell interior involving the multiple-pass transmembrane protein ANK. But these mechanisms become dysrgulated in aging and osteoarthritic (OA) cartilage and extracellular PPi excess supervenes, mediated in large part by upregulated NPP1 and ANK expression in articular cartilage. Conversely, NPP1 and ANK deficiency states were recently linked to phenotypically similar forms of spontaneous soft tissue calcification with hydroxyapatite (HA). Here, we focus on recent advances in understanding of PPi metabolism and NPP1 and ANK function pertinent to the pathogenesis of pathologi matrix calcification in articular cartilage.

Animals↗
PubMed1995

Three-dimensional surface analysis of young adult human articular cartilage.

The objective of this investigation was to determine whether the surface of young adult human articular cartilage was smooth as defined by industrial standards for metal surfaces. Human articular cartilage with attached subchondral bone from the midregion of the trochlear surface of the talus was obtained postmortem from 7 donors (aged 29 +/- 9 y). The specimens were processed using multiple fixation techniques prior to scanning electron microscopy and 3-dimensional stereoscopic analysis. Three-dimensional stereoscopic data showed that 92.78 +/- 16.90% of the articular surface was devoid of surface irregularities and was considered to be smooth. The remaining regions comprising 7.22 +/- 17.20% of the area demonstrated bumps measuring 7.70 +/- 4.58 microns in height. When the results of this study were compared with the international standards for surface preparations used by machinists for metal surfaces, they clearly showed that even when the regions with bumps were considered, the articular cartilage surface could be characterised as smooth.

Adolescent↗
PubMed1979

In vitro hexosamine depletion of intact articular cartilage by E-prostaglandins: prevention by chloroquine.

Short-term incubations of intact canine articular cartilage slices with prostaglandins E1 and E2 caused significant losses of hexosamine from cartilage matrix compared to controls. Chloroquine, an inhibitor of DNA primer, prevented this prostaglandin-induced hexosamine depletion. These data suggest that E-prostaglandins may degrade articular cartilage directly through DNA-dependent RNA synthesis of cathepsin-like proteases. Catabolism of articular cartilage probably involves degradation of existing matrix in addition to inhibition of synthesis.

Animals↗
PubMed1985

A method for quantitative analysis of ratios of types I and II collagen in small samples of articular cartilage.

Currently available methods for quantitative analysis of type II collagen in studies of articular cartilage repair either require much larger samples than are available or are inaccurate and unreliable. A method of determining the percentage of type II collagen in small samples of articular cartilage (100 to 200 micrograms) by measuring the spectrophotometric densities of specific cyanogen bromide peptide bands from mixtures of types I and II collagen on sodium dodecyl sulfate-polyacrylamide gels has been developed and found to be accurate and very reliable. The ratio of the area under the alpha 1(II)CB10 peak to the area under the alpha 1(I)CB7,8 + alpha 1(II)CB11 peak was function of the proportion of type II collagen in the sample. Since the ratio was independent of the quantity of sample loaded onto the gel, it was not affected by moderate losses of sample. This method should therefore be useful in the fields of collagen research and particularly valuable to those investigating the repair and regeneration of articular cartilage.

Animals↗
PubMed1993

Secretory leucocyte proteinase inhibitor is produced by human articular cartilage chondrocytes and intervertebral disc fibrochondrocytes.

The objective of this study was to examine the expression of the secretory leucocyte proteinase inhibitor (SLPI) gene by human articular cartilage chondrocytes and intervertebral disc fibrochondrocytes. RNA was extracted from human articular cartilage chondrocytes, synovial fibroblasts and fibrochondrocytes of the annulus fibrosus. Expression was analysed by Northern blotting and hybridisation to a SLPI RNA probe. SLPI was isolated from chondrocyte culture supernatant by gel-permeation and cation-exchange chromatography and examined by a solid-phase enzyme-linked immunofiltration assay for SLPI and by SDS/PAGE using Western blotting with polyclonal IgG samples against bronchial mucus leucocyte proteinase inhibitor and SLPI. This identified biochemically and immunologically the major serine proteinase inhibitory protein synthesised by chondrocytes as SLPI. Secretory leucocyte proteinase inhibitor mRNA was detected in RNA preparations from articular cartilage chondrocytes and annulus fibrosus fibrochondrocytes. The results presented here allowed us to deduce that human articular cartilage chondrocytes and intervertebral disc fibrochondrocytes synthesized SLPI whereas human synovial fibroblasts did not.

Adult↗
PubMed1994

Mechanical and biochemical changes in the superficial zone of articular cartilage in canine experimental osteoarthritis.

The changes in the tensile mechanical properties and biochemical composition of the superficial zone of articular cartilage were examined in a canine model of early osteoarthritis generated by transection of the anterior cruciate ligament. Sixteen weeks following ligament transection, the tensile stiffness of the articular cartilage was decreased by 44% and the ion-induced stress relaxation of the tissue was increased by 57% compared with the contralateral control. Biochemical analyses indicated that the water content of the experimental tissue was increased by 13%, which was reflected as an apparent 37% decrease in the proteoglycan content and a 36% decrease in the collagen content (expressed per wet weight). The hydroxypyridinium crosslink density was decreased in the experimental tissue by 11%. A significant negative correlation was found between the ion-induced stress relaxation and the hydroxypyridinium crosslink density in both control tissue (R = -0.56) and experimental tissue (R = -0.70). No correlation was noted between the tensile stiffness and the biochemical composition of the tissue. These results suggest that, in the superficial zone of articular cartilage, the structure of the tissue may play a more important role than the composition in the determination of its mechanical properties. A major event observed in the model of early osteoarthritis appears to be the disruption and remodeling of the collagen network in the superficial zone of the articular cartilage.

Animals↗
PubMed1986

Idiopathic chondrolysis of the hip: an ultrastructural study of the articular cartilage of the femoral head.

Core biopsies obtained from the articular cartilage of the femoral head of a 16-year-old girl with idiopathic chondrolysis of the hip were subjected to an ultrastructural study. Zone I was missing and zone II was the most superficial layer present in the articular cartilage of our patient. Collagen fibrils were thinner than normal and more uniform in diameter, and proteoglycans were normally distributed among them. Degenerating chondrocytes were found, as well as debris of dead cells, but many chondrocytes were still vital and engaged in active synthesis. Most of the chronic degenerative changes observed in ultrastructural studies on osteoarthritis were not observed in this case of idiopathic chondrolysis which seems to be, on the basis of our findings, a pathological process which develops and runs its course very quickly.

Adolescent↗
PubMed1999

[Sources of nutrition and structural regeneration of articular cartilage].

Based on data obtained from comparative anatomic vessel material by methods of modern histology and cytology considerations were made on ways of structural and functional differentiation of chondrocytes and peculiarities of articular cartilage cytoarchitecture. Nutrition of articular cartilage cells is provided by subcartilaginous bone vessels. Synovial medium of the joint maintains the cartilaginous state of the surface of the connected skeletal units. Physiological self repair of articular cartilage occurs due to interstitial growth provided by the maintenance of chondrocyte proliferation in interstitial (intermediate) zone.

Animals↗
PubMedDate not supplied

Partial patellectomy induces a decrease in the proteoglycan content in the remaining patellar articular cartilage. An experimental study in rabbits.

We studied the alterations and distribution of the proteoglycan (PG) content of the remaining patellar articular cartilage after unilateral partial patellectomy in 13 rabbits. Sagittal sections of the patella were prepared and stained with Safranin O for quantification of changes in the PG content of the patellar articular cartilage using a commercially available imaging analysis system. Our findings suggest that partial patellectomy results in a decreased PG content in the remaining patellar articular cartilage. In addition, the postoperative development of metaplasia in the scar tissue next to the healing interface may represent a compensatory response, which could prevent a further reduction in the PG content and hence the development of osteoarthritis in the remaining patellar articular cartilage.

Animals↗
PubMed2001

[Preparation and analysis of pure type II collagen from porcine articular cartilage].

This investigation was aimed at the preparation of pure type II collagen from porcine articular cartilage and the feasible method for producing type II collagen in bulk. After dispersal of the porcine articular cartilage, the proteoglycans were extracted by guanidinium hydrochloride and dissolved by pepsin in acid solvent. The contaminants including denatured and degraded protein and other collagen was removed via the repeated procedure of purification. For obtaining the purer type II collagen, the chromatography with sepharose H. P. Column was also used. The purity of the sample was compared with the type II collagen produced by Sigma Company. Both type II collagens were characterized by SDS-PAGE electrophoresis, amino acid analysis and maximal violet chromatography, and all of the results accorded with the standard photograph in the references. The purity of the sample was higher than that of the product of Sigma Company. This prepared collagen of type II is a product of high purity. The raw materials are the common porcine articular cartilage, which is rich in resource and low in cost. Therefore, it is suitable to produce type II collagen in batches.

Amino Acids↗
PubMed2006

Competing regulation of matrix biosynthesis by mechanical and IGF-1 signalling in elderly human articular cartilage in vitro.

This study investigates the separate and combined effects of IGF-1 and mechanical loads on chondrocytes in elderly human femoral head articular cartilage. Full depth biopsies of articular cartilage were subjected to either no load, static or cyclic (2 s on/2 s off) loading in unconfined compression at a stress of 1 MPa for 48 h with or without IGF-1 (300 ng ml(-1)). Chondrocyte biosynthetic activity was measured using 35S-sulphate and 3H-leucine during the last 24 h of loading. IGF-1 alone increased the rates of isotope incorporation, by 80% for 35S-SO4 and 40% for 3H-leucine, whereas loading alone reduced matrix biosynthesis. Applying load (cyclic or static) in the presence of IGF-1 returned the incorporation rates to their unstimulated levels. This study suggests elderly human articular cartilage is responsive to stimulation by IGF-1 but mechanical factors seem to act sufficiently strongly in the opposite direction to cancel this response.

Aged↗