Validity of histopathological grading of articular cartilage from osteoarthritic knee joints

OBJECTIVES: To determine the validity of the histological-histochemical grading system (HHGS) for osteoarthritic (OA) articular cartilage. METHODS: Human articular cartilage was obtained from macroscopically normal (n = 13) and OA (n = 21) knee joints. Sections of central and peripheral regions of normal samples were produced. Sections of regions containing severe, moderate, and mild OA changes were produced from each OA sample. A total of 89 sections were graded by means of the HHGS (0-14) twice by three observers. RESULTS: Average scores for regions designated severe (8.64) and moderate (5.83) OA were less than the expected (10-14 and 6-9, respectively) according to the HHGS, whereas average scores for the region designated mild (5.29) OA and central and peripheral regions (2.19) of normal cartilage were higher than expected (2-5 and 0-1, respectively). The HHGS was capable of differentiating between articular cartilage from macroscopically normal and OA joints and between the region designated severe OA and other regions. However, the HHGS did not adequately differentiate between regions designated mild and moderate OA. Values for sensitivity, specificity, and efficiency for all regions varied considerably. CONCLUSION: The HHGS is valid for normal and severe OA cartilage, but does not permit distinction between mild and moderate OA changes in articular cartilage.     

Characterisation of human articular cartilage link proteins from normal and osteoarthritic cartilage.

Proteoglycan link proteins were isolated from human articular cartilage obtained from normal and osteoarthritic femoral heads and purified to homogeneity employing a method previously described by this laboratory. The link proteins were analysed for amino acid composition, molecular weight on sodium dodecyl sulphate polyacrylamide gels, and ability to stabilise proteoglycan aggregates. The results of these studies were compared with those obtained with bovine link proteins. Two link proteins were identified in the purified fraction from normal and osteoarthritic human cartilage with apparent molecular weights of 54 000 (link 1) and 48 000 (link 2). Functionally the link proteins, isolated from osteoarthritic and normal cartilage, were indistinguishable as measured by their ability to stabilise aggregate. The amino acid compositions of normal and osteoarthritic link proteins were also found to be similar to each other but significantly different from the amino acid composition reported for the bovine link proteins. The quantities of these proteins in extracts from normal and diseased tissue were similar, as was the ratio of link protein 1 to link protein 2.     

Apoptosis and p53 expression in chondrocytes relate to degeneration in articular cartilage of immobilized knee joints

OBJECTIVE: We have reported that articular cartilage showed early stage degeneration at 7 and 14 days after immobilization, moderate degeneration at 28 days, and severe degeneration at 42 days in rabbits. To test whether apoptosis occurs in association with p53 expression in chondrocytes during the process of articular cartilage degeneration, we investigated the degree of cartilage degeneration, the frequency of apoptotic cells, and the levels of p53 mRNA in rabbits and mice after knee immobilization. METHODS: Right knees of male Japanese white rabbits were immobilized in full extension with fiberglass casts for up to 42 days. Similarly, right knees of male p53 wild-type [p53 (+/+)] and p53 null [p53 (-/-)] mice were immobilized in full extension with bandage tape for up to 84 days. Apoptotic cells were confirmed by TUNEL staining on the sections of knee joints. Total RNA of articular chondrocytes obtained from Day 0 or immobilized knees was analyzed semiquantitatively by RT-PCR using specific primers for p53. RESULTS: Articular cartilage degenerated after immobilization of p53 (+/+) mouse knees, but not after immobilization of p53 (-/-) knees. Apoptotic cells were observed in articular cartilage in the femur and tibia of rabbits and p53 (+/+) mice after immobilization. However, only a few apoptotic cells were observed at the same sites in p53 (-/-) mice. In RT-PCR analysis, the levels of p53 mRNA obtained from immobilized groups were significantly higher than those of Day 0 groups in rabbit and p53 (+/+) mouse knees. CONCLUSION: Apoptosis and p53 expression in chondrocytes relate to degeneration in articular cartilage of immobilized knee joints.     

Effects of exercise on synovium and cartilage from normal and inflamed knees

The effect of running activity on normal and inflamed knees was determined by light microscopic (LM) and scanning electron microscopic (SEM) observations on hamster articular cartilage. Animals were split into two groups; one housed in standard cages and one given free access to running wheels. Twenty-one days prior to analysis, half of each group was given an intraarticular injection of lipopolysaccharide (LPS) to cause an inflammation, the other half were uninjected. No remarkable changes were observed by LM in either the control running or nonrunning groups. In contrast, cartilage proteoglycan depletion, and pannus and synovial hyperplasia were equally observed in both groups of LPS-injected animals. SEM observations on the patellae from control animals found them to be free from damage to the articular cartilage. The joints of both the LPS nonrunning and running animals contained synovial hypertrophy with villus projection from the synovial lining. However, only the LPS-injected running hamsters had cartilage fraying over large areas of the articular surface, as well as areas in which the villus projections had been flattened. These results demonstrated that mechanical stress applied to a proteoglycan-depleted cartilage enhances the breakdown of the collagen matrix as judged by fibrillation, and may aggravate the inflammation by crushing the swollen synovial lining where it encroaches on the joint space.     

Characterization of gangliosides from normal and osteoarthritic human articular cartilage

Objective. Glycosphingolipids (GSLs) are biologically active molecules in the physiology and pathology of cells. Since changes in GSLs might be associated with the impaired metabolism of articular cartilage in osteoarthritis (OA), we investigated gangliosides from normal and OA human cartilage. Methods. OA and control cartilage was obtained from patients with hip OA and femoral neck fracture, respectively. Gangliosides were extracted and quantified by determining their lipid-bound sialic acid concentration. Major gangliosides were identified by immunodetection on thin-layer plates, purified by high performance liquid chromatography, and analyzed for their carbohydrate, fatty acid, and long-chain base composition. Results. The total ganglioside content of OA cartilage was decreased by 40% (per mg of DNA). Major gangliosides, GM₃ and GD₃, separated into 3 on thin-layer chromatography bands. All were decreased except for the lowest migrating band of GM₃, which was increased 5-fold. This ganglioside had the same carbohydrate moiety and fatty acids as the other two, but differed by a long-chain base composed mainly of C20-sphingosine. Conclusion. OA cartilage is characterized by a decrease in all gangliosides except GM₃, which demonstrates a large increase in the lowest band. These results indicate that there are changes in the biochemical composition of chondrocyte membranes in OA. The causes and roles of these changes remain to be determined.     

Regeneration of articular cartilage of the knee

Cartilage therapy for focal articular lesions of the knee has been implemented for more than a decade, and it is becoming increasingly available. What do we know on the healing response of cartilage lesions? What do we know on the treatment of focal cartilage lesions of the knee and the prognostic factors involved? PubMed articles related to articular cartilage regeneration of the knee in clinical studies were searched from January 2006 to November 2012, using the following key words: articular cartilage, regeneration, clinical studies, and knee. A total of 44 reports were found. They showed the following possibilities for the treatment of focal lesions of the articular cartilage of the knee: cartilage regeneration and repair including cartilage reparation with gene-activated matrices, autologous chondrocyte implantation (ACI) and matrix-induced ACI (MACI), microfracture, osteochondral autograft transfer (mosaicplasty), biological approaches (scaffolds, mesenchymal stem cells—MSCs, platelet-rich plasma, growing factors—GF, bone morphogenetic proteins—BMPs, magnetically labeled synovium-derived cells—M-SDCs, and elastic-like polypeptide gels), osteotomies, stem-cell-coated titanium implants, and chondroprotection with pulsed electromagnetic fields. Untreated cartilage lesions on the femoral condyles had a superior healing response compared to those on the tibial plateaus, and in the patellofemoral joint. Clinical outcome regarding the treatment of medial defects is better than that of the lateral defects. Improvement from baseline was better for patients < or = 30 years compared with patients > or = 30 years. ACI, MACI, and mosaicplasty have shown similar results. The results of comparative clinical studies using ACI have shown some superiority over conventional microfracturing in medium or large defects and in long-term durability. Some biological methods such as scaffolds, MSCs, GF, M-SDCs, BMPs, and elastic-like polypeptide gels still need more research.     

The distribution of S-100 protein in articular cartilage from osteoarthritic joints

The distribution and localization of S-100 protein was compared with safranin-O staining and H and E morphology in relatively unaffected, degenerative, and osteophytic regions of human articular cartilage from 26 joints obtained at the time of total joint replacement for osteoarthritis. S-100 protein immunoreactivity in osteophyte cartilage was more intense than in unaffected regions and comparable to the staining intensity found in metaplastic cartilage tufts in degenerating cartilage. Immunoreactivity for S-100 protein appeared more prominent in the deep layers of osteophyte cartilage adjacent to areas of matrix calcification.     

Relationship between the tensile properties of articular cartilage from the human knee and age.

The relationship between the tensile properties of articular cartilage and age has been investigated in vitro in the human knee joint. Specimens orientated parallel to the articular surface were excised from the superficial and deep zones of the femoral condyles of knee joints of persons in the age range from 8 to 91 years. The results showed that the tensile strength of the superficial zone increased with age to reach a maximum value in the third decade. Thereafter the strength decreased markedly with increasing age. The tensile strength of cartilage from the deep zone did not show an increase in the early years but decreased continuously with age. The tensile stiffness of the superficial layer at stresses of 5 MN/m2 and 10 MN/m2 increased to maximum values in the third decade and thereafter decreased with increasing age. The stiffness of the deep zone decreased continuously with age. It is suggested that these results reflect changes in the organisation of the collagen fibre mesh with age and possibly also changes in the collagen cross-links.     

Apoptosis in normal and osteoarthritic human articular cartilage

OBJECTIVES: To investigate whether apoptosis occurs in osteoarthritis (OA), and if this phenomenon is modulated by human recombinant interleukin 1beta (hrIL1beta). METHODS: Human articular cartilage samples were obtained at the time of hip arthroplasty because of femoral neck fracture (normal cartilage) (n=4) or advanced coxarthrosis (OA cartilage) (n=14). Apoptotic chondrocytes, isolated by collagenase digestion and cultivated for 24 hours, or present in situ in frozen cartilage sections, were quantified by fluorescent microscopy using two apoptosis markers: the TUNEL reaction, which detects nuclear DNA fragmentation, and Annexin-V-fluos, which labels at the membrane level the externalisation of phosphatidylserine. RESULTS: In OA cartilage 18-21% of chondrocytes showed apoptotic features, compared with 2-5% in normal cartilage. The results were similar for the two comparative studies (in situ and in vitro) and for both apoptosis markers. Moreover, hrIL1beta increased the apoptosis rate in vitro in a dose dependent manner in OA and normal chondrocytes. CONCLUSION: These results suggest that apoptosis may be an important factor in the evolution of OA and may be a new target for treatment of OA.     

Metabolism of a cartilage matrix glycoprotein in normal and osteoarthritic canine articular cartilage

We have recently described a 550,000-dalton noncollagenous cartilage matrix glycoprotein (CMGP), with subunits of 130,000, which is present in hyaline cartilage and fibrocartilage. Biosynthetic studies indicated that CMGP was synthesized by short-term organ cultures of normal canine articular cartilage, representing approximately 9% of the total 3H-leucine incorporated into protein in 24-hour cultures. There was no incorporation of 35S-sulfate or 3H-mannose into CMGP under these conditions, but the protein did incorporate 32P-phosphate. The majority of the 3H-leucine-labeled CMGP was removed after 24 hours of chase with unlabeled leucine, and only a small amount remained at 72 hours, which suggests that there was rapid metabolism of the protein. CMGP was not detected in cartilage after addition of cycloheximide to the culture medium; this confirms its short half-life. Cultures of osteoarthritic cartilage obtained from dogs 8-10 weeks after anterior cruciate ligament transection revealed no difference in the metabolism of CMGP in this tissue compared with that found in cultures of normal articular cartilage.     

Chondrocyte IGF-1 receptor expression and responsiveness to IGF-1 stimulation in mouse articular cartilage during various phases of experimentally induced arthritis.

OBJECTIVE--To examine the distribution of insulin like growth factor-1 (IGF-1) receptors and the biological response to IGF-1 stimulation in articular cartilage of normal mouse knee joints and arthritic joints taken at various stages of experimentally induced arthritis. METHODS--In situ IGF-1 receptor expression and responsiveness to IGF-1 stimulation were examined in murine articular cartilage at different phases in two models of experimentally induced arthritis. IGF-1 receptor expression was visualised in joint sections with the use of anti-IGF-1 receptor antibodies and quantified by confocal laser scanning microscopy. Chondrocyte proteoglycan (PG) synthesis was measured by incorporation of 35S-sulphate. RESULTS--In control cartilage, the majority of IGF-1 receptors were found on chondrocytes localised in the middle and deeper zones of the cartilage, whereas receptor expression in surface zone chondrocytes was very low. During culture of normal articular cartilage, IGF-1 was able to maintain chondrocyte PG synthesis at the in vivo level. Concurrently with the development of arthritis, cartilage lost its capacity to react to IGF-1, but IGF-1 stimulation recovered when the inflammatory response waned. Shortly after induction of arthritis, IGF-1 receptor expression initially declined, but it had returned to normal levels by day 1 and remained increased thereafter. CONCLUSION--The distribution of IGF-1 receptor expression in the different zones of normal articular cartilage reflects IGF-1 stimulation and metabolic activity of chondrocytes in these layers. This correlation is disturbed in arthritic cartilage, suggesting inadequate or overruled signalling.     

Thickness of human articular cartilage in joints of the lower limb

OBJECTIVES: (a) To determine the topographical variations in cartilage thickness over the entire surfaces of cadaveric lower limb joints, and (b) to examine the correlations between: cartilage thickness and its site specific modulus; cartilage thickness and donor age, weight, height, and body mass index. METHODS: The cartilage thickness of 11 sets of cadaveric human joints each comprising an ankle, knee, and hip was measured using a needle probe technique. Statistical analysis was used to compare the cartilage thickness of the different lower limb joints and the differences in cartilage thickness over the surface of individual joints. It was further examined whether cartilage had a correlation with its stiffness, and any of the details of the specimen donors such as age, weight, height, and body mass index. RESULTS: The mean cartilage thickness of the knee was significantly greater than that of the ankle and hip (p < 0.001) in all 11 sets of joints, while the cartilage thickness of the hip was significantly greater than that of the ankle in 10 sets of joints (p < 0.001). The mass of specimen donors was found to correlate with the mean cartilage thickness of all three lower limb joints. A correlation was also found between the height of donors and the mean cartilage thickness of the knee and hip joints, while only in the ankle joint was a correlation found between the mean cartilage thickness and the body mass index of the specimen donors. A further correlation was found between cartilage thickness and its modulus; the thinner the cartilage, the higher the modulus. CONCLUSIONS: The thickness of articular cartilage seems to be related to the congruance of a joint; thin cartilage is found in congruent joints such as the ankle, whereas thick cartilage is found in incongruent joints such as the knee. The correlations in this study imply that the larger and heavier was a donor the thicker was the cartilage in the lower limb joints. The data further suggest the presence of an inverse relation between the mean cartilage thickness and mean compressive modulus in each of the joints examined.