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PubMed1978

In vitro collagen biosynthesis in healing and normal rabbit articular cartilage.

To examine the repair collagens produced by cells in injured cartilage, the femoral articular surfaces of three groups of New Zealand white rabbits were injured by making both superficial and deep lacerations and drill holes. Eight weeks after surgery, the rabbits were killed and slices of injured articular cartilage were harvested. The types of collagen being synthesized at the site of these lesions were identified by labeling the recovered specimens in vitro with 3H-proline and by characterizing the collagen using sodium dodecyl sulphate electrophoresis, carboxymethyl cellulose chromatography, and cyanogen bromide peptide analysis. In all cases, tissue-specific type II ([alpha1 (II)]3) cartilage collagen was synthesized. Histological examination using toluidine blue showed that the chondrocytes bordering the cartilage defect produced by deep lacerations and drill holes responded by increased cellular activity, as shown by cell cloning and increased matrix staining. The drilled holes were completely filled by tissue with staining and morphological characteristics similar to those of hyaline cartilage.

Animals↗

PubMed1982

Experimental study on immunological reactions against the articular cartilage.

In rats immunized with articular cartilage antigens, delayed hypersensitivity was detected by the macrophage migration inhibition test and delayed footpad reaction. Additionally, a proliferative response was found in the regional lymph nodes of immunized rats. The mixed addition of sensitized lymphocytes and antibodies exerted a cytotoxic effect on cultured chondrocytes. Articular damage including accelerated chondrolysis may have some relation to delayed hypersensitivity to autologous articular cartilage antigens.

Animals↗

PubMed2006

Multinuclear NMR and MRI studies of the maturation of pig articular cartilage.

The maturation of pig articular cartilage was followed by (2)H in-phase double quantum filtered (IP-DQF) spectroscopic MRI, (1)H T(2) MRI, and (23)Na DQF and triple quantum filtered MRS. The results all lead to the conclusion that the order and density of the collagen fibers in articular cartilage increase from birth to maturity. At birth, both (2)H IP-DQF signal and (1)H T(2) were homogeneous throughout the cartilage and their values independent of the orientation of the plug relative to the magnetic field. At maturation, the (2)H IP-DQF spectrum near the bone is composed of two pairs of quadrupolar split satellites and the (1)H T(2) relaxation is biexponential, indicating the presence of two groups of collagen fibers. The (2)H satellites are orientation dependent, indicating that the two groups of fibers are well ordered at maturation. The fast component of (1)H T(2) is also orientation dependent and thus we have concluded that this component results from residual dipolar interaction, while the slow T(2) component in mature cartilage, as well as the T(2) relaxation in immature cartilage, is governed by other mechanisms.

Animals↗

PubMed2005

Aggrecan, aging and assembly in articular cartilage.

The primary function of articular cartilage to act as a self-renewing, low frictional material that can distribute load efficiently at joints is critically dependent upon the composition and organisation of the extracellular matrix. Aggrecan is a major component of the extracellular matrix, forming high molecular weight aggregates necessary for the hydration of cartilage and to meet its weight-bearing mechanical demands. Aggregate assembly is a highly ordered process requiring the formation of a ternary complex between aggrecan, link protein and hyaluronan. There is extensive age-associated heterogeneity in the structure and molecular stoichiometry of these components in adult human articular cartilage, resulting in diverse populations of complexes with a range of stabilities that have implications for cartilage mechanobiology and integrity. Recent findings have demonstrated that aggrecan can form ligands with other matrix proteins. These findings provide new insights into mechanisms for aggregate assembly and functional protein networks in different cartilage compartments with maturation and aging.

Aggrecans↗

PubMed1988

The classification and treatment of acute articular cartilage lesions.

Sixty-five articular cartilage knee lesions were diagnosed by arthroscopy over a 5-year period, and classified according to the age, the size, the depth, and the location of the lesion. The purpose of this study was to evaluate surgical outcome of a standardized treatment regimen consisting of complete vertical excision of diseased or injured articular cartilage followed by drilling of the subchondral bone plate. A standardized postoperative rehabilitation protocol was used, which included non-weight bearing for eight weeks. Overall clinical results at two years revealed 69% good, 3% fair, and 28% poor knees. Seventy-one percent of patients underwent follow-up arthroscopy at 1 year and 57% consented to biopsy. Retrospective analysis revealed that the group with the best prognosis consisted of small-to-medium acute partial thickness lesions on the weight bearing portion of the femoral condyles. Ninety-five percent of this group had good results.

Arthroscopy↗

PubMed1991

A quantitative analysis of the ultrastructural organization of extracellular components in human articular cartilage.

Extracellular components of human articular cartilage have been studied using quantitative and ultrastructural methods. A new combination of electron microscopic, physicochemical, and mathematical methods has been proposed to study the structural organization of the fibrillar stroma, interfibrillar spaces, and structural proteoglycans. The new methodology has made it possible to isolate in the cartilage three layers with various types of spatial orientation of the fibrillar stroma. The summary volume and differential distribution of the interstitial microcirculatory channel have been derived. Proteoglycans of the integrative buffer metabolic medium have been identified using transmission and scanning electron microscopy. The data suggest a more accurate concept of the structural organization of human articular cartilage.

Adult↗

PubMed2002

Ultrasonic characterization of articular cartilage.

Osteoarthrosis is the most important joint disease that threatens health of the musculoskeletal system of elderly people. Today, there is a need for sensitive, quantitative diagnostic methods for successful and early diagnosis of the disorder. In the present study, we aimed at evaluating the applicability of ultrasound for quantitative assessment of cartilage structure and properties. Bovine articular cartilage was investigated both in vitro and in situ using high frequency ultrasound. Cartilage samples were also tested mechanically in vitro to reveal relationships between acoustic and mechanical parameters of the tissue. The collagen organization and proteoglycan content of cartilage samples were mapped, using quantitative polarized light microscopy and digital densitometry, respectively, to reveal their effect on the acoustic properties of tissue. The high frequency pulse-echo ultrasound (20-30 MHz) technique proved to be sensitive in detecting the degeneration of the superficial collagen-rich cartilage zone. In addition, ultrasound was found to be a potential tool for measuring cartilage thickness. When the results from biomechanical indentation measurements and ultrasound measurements of normal and enzymatically degraded articular cartilage were combined, collagen or proteoglycan degradation in the tissue could be sensitively and specifically differentiated from each other. To conclude, high frequency ultrasound is a useful tool for evaluation of the quality of superficial articular cartilage as well as for the measurement of cartilage thickness. Therefore, ultrasound appears to be a valuable supplement to the mechanical measurements of articular cartilage stiffness.

Animals↗

PubMed1992

Biochemistry of articular cartilage in health and disease.

Articular cartilage covers the ends of long bones in synovial joints, providing smooth articulation and cushioning of the underlying bone during joint movement. The tissue can be viewed as a viscoelastic, composite material composed of collagen type II (and smaller amounts of other collagens) entrapping compressed (underhydrated) proteoglycan aggregates which generate a high osmotic/swelling pressure. This abundant extracellular matrix (ECM) is synthesized and turned over by relatively few cells, the chondrocytes. These cells produce a compartmentalized ECM, the components of which are heterogeneous and vary with anatomical location. They also undergo changes with age and altered functional requirements. Articular cartilage contains no separating basement membranes, nerves, lymphatics, or blood vessels. Access to nutrients and elimination of waste products occur via diffusion through the extracellular matrix. The turnover of collagen is much slower than that of proteoglycans. Products of the metabolic turnover of the matrix macromolecules are released continuously into the synovial cavity and ultimately reach the blood circulation where they can be measured as "markers" of metabolic changes.

Animals↗

PubMed2003

In vitro action of combinations of selected antimicrobial agents and adult bovine articular cartilage (sesamoid bone).

Anatomically intact articular cartilage in form of sesamoid bones from metacarpophalangeal joints of 2-year-old cows was tested for its influence on the microbicidal effect of the iodophore Betaisodona, the bispyridinamine Octenisept, and the biguanide Lavasept. Comparisons were carried out in Ham's F12 medium with and without 0.2% bovine serum albumin as organic matter loading. The expected abolition of the microbicidal effect of these antiseptics against the test organisms Escherichia coli or Staphylococcus aureus in the presence of sesamoid bone was not evident. Furthermore, sesamoid bone alone demonstrated antibacterial activity against Staphylococcus aureus, which may involve adherence of bacteria to surface constituents of articular cartilage. Final concentrations of 2.5-5% Betaisodona, 5% Octenisept as well as 0.025% Lavasept are effective in killing of 10(8)-10(9) cfu/ml Escherichia coli or Staphylococcus aureus in the presence of sesamoid bone without the reduction of antimicrobial activity expected from binding to CS, which has previously been demonstrated for CS in solution.

Animals↗

PubMed2001

Anionic sites in articular cartilage revealed by polyethyleneimine staining.

Articular cartilage is a unique tissue that contains neither blood vessels nor nerves, and that performs mechanical loading during joint movement. These properties are endowed by abundant glycosaminoglycans (GAGs), which are capable of retaining water-soluble substances. The GAGs attach to core proteins and form proteoglycans. Although many studies have focused on proteoglycans and collagen fibrils in cartilage, little is known about the nature of the negative charge of GAGs. Recently, we investigated this subject using a cationic dye, polyethyleneimine (PEI), with several different techniques such as pre-embedding, post-embedding, and quick-freezing and deep-etching methods. In addition, we investigated whether the anionic charge is altered at low pH, using PEI and cationic colloidal gold (CCG) labeling. The shapes of PEI-positive structures revealed by the pre-embedding method varied at different pHs. Three-dimensional analysis using the quick-freezing and deep-etching method demonstrated that meshwork structures composed of fine filaments were decorated with tiny PEI granules. Additionally, the meshwork structure was broken down after chondroitinase ABC digestion. These data indicate that the large PEI deposits observed in pre-embedding preparations are, at least in part, artificial images, and that the meshwork structure consists of chondroitin sulfate-retaining anionic sites. Low pH conditions changed PEI or CCG labeling patterns, showing that negative charges of GAGs in articular cartilage are altered under environmental pH conditions. These findings demonstrate that binding capacities of anionic sites to water-soluble or ionic substances are greatly affected by pH alterations without actually decreasing the number of anionic sites. Therefore, to understand cartilage dynamics and the pathogenesis of joint diseases in greater detail, alterations of anionic charge during mechanical loading or under pathological conditions should be examined in future studies.

Animals↗

PubMed1993

Evidence for the degradation of type XI collagen by bovine intervertebral disc- and articular cartilage extracts.

Bovine intervertebral disc- and articular cartilage extracts contain a metalloproteinase system capable of degrading type XI collagen. The collagen-degrading activity is rather low in unmodified extracts but increases considerably on metalloproteinase activation. The similarity between intervertebral disc and articular cartilage in their patterns of (casein-degrading) metalloproteinases and type XI and type II collagen degradation is believed to suggest a similarity in the events underlying the degradative disorders of articular cartilage and intervertebral disc.

Animals↗

PubMed1995

VDIPEN, a metalloproteinase-generated neoepitope, is induced and immunolocalized in articular cartilage during inflammatory arthritis.

The destruction of articular cartilage in immune inflammatory arthritic disease involves the proteolytic degradation of its extracellular matrix. The role of activated matrix metalloproteinases (MMPs) in the chondrodestructive process was studied by identifying a selective cleavage product of aggrecan in murine arthritis models initiated by immunization with either type II collagen or proteoglycan. We conducted semiquantitative immunocytochemical studies of VDIPEN341 using a monospecific polyclonal antibody requiring the free COOH group of the COOH-terminal Asn for epitope detection. This antibody recognizes the aggrecan G1 domain fragment generated by MMP [i.e., stromelysin (SLN) or gelatinase A] cleavage of aggrecan between Asn341-Phe342 but does not recognize intact aggrecan. VDIPEN was undetectable in normal mouse cartilage but was observed in the articular cartilage (AC) of mice with collagen-induced arthritis 10 d after immunization, without histological damage and clinical symptoms. This aggrecan neoepitope was colocalized with high levels of glycosaminoglycans (GAGs) in pericellular matrices of AC chondrocytes but was not seen at the articular surface at this early time. Digestion of normal (VDIPEN negative) mouse paw cryosections with SLN also produced heavy pericellular VDIPEN labeling. Computer-based image analysis showed that the amount of VDIPEN expression increased dramatically by 20 d (70% of the SLN maximum) and was correlated with GAG depletion. Both infiltration of inflammatory cells into the synovial cavity and early AC erosion were also very prominent at this time. Analysis of adjacent sections showed that both induction of VDIPEN and GAG depletion were strikingly codistributed within sites of articular cartilage damage. Similar results occurred in proteoglycan-induced arthritis, a more progressive and chronic model of inflammatory arthritis. These studies demonstrate for the first time the MMP-dependent catabolism of aggrecan at sites of chondrodestruction during inflammatory arthritis.

Amino Acid Sequence↗

PubMed1996

Fetal chondral homografts in the repair of articular cartilage defects.

Lesions of the articular cartilage were bilaterally induced in the patella and the femoral condyle of adult NZW rabbits. A fresh fetal chondral homograft was implanted in one side, the untreated side serving as control. Fetal chondral tissue appeared to survive when implanted at the site of articular injury in adult animals, with no histological evidence of cell-mediated immune response. Fetal chondroblasts showed some signs of maturation and induced endochondral ossification at the base of the graft, with sound anchoring of the graft to the host tissue. In most cases, the homograft fused directly with the adjacent articular cartilage restoring the continuing of the articular surface. However, at implantation the graft could not be easily kept in place, and therefore some grafts had poor mechanical stability. Condylar grafts were incorporated better than patellar grafts. The healing process seemed to be related to the mechanical stability of the graft and to the anatomical site of injury.

Animals↗

PubMed2004

Active proliferation of mesenchymal cells prior to the chondrogenic repair response in rabbit full-thickness defects of articular cartilage.

OBJECTIVES: In full-thickness articular defects, fibroblast growth factor-2 (FGF-2) participates in the chondrogenic repair response which occurs in a defect-size dependent manner. Here we demonstrate that FGF-2 plays a critical role in the proliferation of pre-chondrogenic mesenchymal cells during chondrogenic induction. METHODS: Three-millimeter- or 5-mm-diameter cylindrical defects were created in the femoral trochlea of the rabbit knee. The defects received sterile saline or FGF-2 (50 pg/h) via an osmotic pump for the initial 2 weeks. We assessed the proliferative capacity of undifferentiated mesenchymal cells in the reparative tissue with the anti-proliferating cell nuclear antigen (PCNA) monoclonal antibody. Using a total of 180 rabbits, we performed three sets of experiments. RESULTS: In the 3-mm-diameter defects, undifferentiated mesenchymal cells spontaneously initiated chondrogenic differentiation within 2 weeks, resulting in the regeneration of surfacing articular cartilage concomitantly with the repair of subchondral bone. No evidence of chondrogenesis was seen in the 5-mm-diameter defects, whereas application of FGF-2 promoted successful regeneration of articular cartilage. In the 3-mm-diameter defects and in the FGF-2-treated 5-mm defects, PCNA immunoreactivity was widely detected in undifferentiated cells in the reparative tissue at 1 and 2 weeks after creation of the defects. In contrast, in the 5-mm-diameter defects without FGF-2 treatment, the PCNA-positive cells were found at a significantly lower incidence. CONCLUSIONS: Active expansion of undifferentiated cell population mediated by FGF-2 is required to initiate and support a chondrogenic repair response in full-thickness defects of articular cartilage. Endogenous FGF-2 could not meet the requirements of growth signaling in the center of larger sized defects.

Alkaline Phosphatase↗

PubMed1998

Current treatment options for the restoration of articular cartilage.

Over the past several decades, much has been learned about articular cartilage and its physiological capacity to restore itself. While articular cartilage does appear to have some regenerative capabilities, it appears to lose this capacity over a period of time, making restoration of articular surfaces more and more difficult. To date, no technique has been completely successful in achieving exactly normal regenerative articular cartilage. Arthroscopic lavage and debridement provides temporary relief of symptoms. This probably works by removing degradative enzymes that contribute to synovitis and also to the further breakdown of articular cartilage. Bone marrow stimulation techniques such as abrasion arthroplasty, drilling, and microfracture produce only fibrocartilage and therefore do not offer a long-term cure. Perichondral and periosteal interposition grafts produce repair tissue that is similar to hyaline cartilage but also lack the mechanical durability. Like bone marrow stimulation techniques, interposition grafts introduce precursor cells, which have a tendency to differentiate along lines other than cartilage. This leads to an inferior quality of repair tissue. Currently, chondrogenic-stimulating factors and artificial matrices are currently being researched and developed. Much has been learned about the various growth factors that stimulate chondrocyte differentiation and extracellular matrix production, but to date, there has not been a clinical technique that has shown any long-term promise. Ultimately, the goal will be to take precursor cells from an easily accessible source such as the iliac crest, mix them with growth factors that have been derived genetically in the lab, and provide an artificial matrix that in combination can produce restoration of articular cartilage at minimal cost and patient morbidity. Autologous osteochondral transplant systems have shown encouraging results but there are still problems. Graft matching and contouring to the recipient articular surface is difficult. Donor sites can be a limiting factor. Furthermore, the fibrocartilaginous interface between the donor and recipient site may contribute to breakdown in the long run. Autologous chondrocyte implantation is a biological repair process that also has shown encouraging results. It must be remembered that this is not normal articular cartilage--it is only hyaline-like cartilage. The technique is expensive and is technically difficult to perform. There are no randomized prospective studies that compare the natural history of the repair tissue to that of other forms of repair tissue. Long-term functional outcome is still a significant question mark. In addition, it has not been shown that autologous chondrocyte implantation can prevent degenerative changes. In the future, we probably will see delivery systems using stimulating growth factors, chondrocytes, and synthetically derived matrices. When placed in combination and with the right mechanical stimuli, we may ultimately achieve true restoration of articular cartilage.

Arthroplasty↗

PubMed2005

The influence of mechanical compression on the induction of osteoarthritis-related biomarkers in articular cartilage explants.

OBJECTIVE: Macromolecules of the articular cartilage extracellular matrix released into synovial fluid, blood, or urine can serve as potentially useful biomarkers of the severity of osteoarthritis (OA). Biomechanical factors play an important role in OA pathogenesis, yet their influence on biomarker production is not well understood. The goal of this study was to examine the hypothesis that dynamic mechanical stress influences the release of these biomarkers from articular cartilage. METHODS: Explants of porcine cartilage were subjected to dynamic compression at 0.5 Hz for 24h at stresses ranging from 0.006 to 0.1 MPa. The concentrations of cartilage oligomeric matrix protein (COMP), keratan sulfate (KS measured as the 5 D 4 epitope), total sulfated glycosaminoglycan (S-GAG), and the KS (keratanase-digestible) and chondroitin sulfate (CS) (chondroitinase-digestible) fractions of S-GAG were measured. Radiolabel incorporation was used to determine the rates of proteoglycan and protein synthesis. RESULTS: The magnitudes of mechanical stress applied in this study induced nominal tissue strains of 4-23%, consistent with a range of physiological to hyperphysiologic strains measured in situ. COMP release increased in proportion to the magnitude of dynamic mechanical stress, while KS, CS and total S-GAG release increased in a bimodal pattern with increasing stress. Protein and proteoglycan synthesis were significantly decreased at the highest level of stress. CONCLUSION: Mechanical stress differentially regulates the turnover of distinct pools of cartilage macromolecules. These findings indicate that mechanical factors, independent of exogenous cytokines or other stimulatory factors, can influence the production and release of OA-related biomarkers from articular cartilage.

Animals↗

PubMed1994

Analysis of changes in proteoglycan content in murine articular cartilage using image analysis.

The extracellular matrix of articular cartilage consists mainly of type II collagen and large aggregating proteoglycan (aggrecan). During arthritis and other joint diseases, the proteoglycan (PG) level of cartilage matrix is diminished, leading to impairment of normal joint function. A new method is described for measuring the changes in PG content of murine articular cartilage. The method is based on the automated densitometric analysis of patellar cartilage of standard, safranin O-stained sections of whole murine knee joints. It appeared to be possible to measure optical density in parallel layers of articular cartilage with high reproducibility. Approximately 25 sections can be evaluated within 1 h. Measuring a single section 10 times resulted in a coefficient of variation (CV) of 0.1-1.4%. A mean CV of 5-14% was calculated when a group of 18 sections was analyzed in quintuplicate. To validate the procedure, changes in PG content induced by arthritis or by intra-articular injection of TGFbeta-1 were analyzed by the image analysis method, the dimethylmethylene blue (DMB) assay and by visual grading. Although not a quantitive method, the newly developed image analysis method appeared to be more sensitive in detecting significant change in PG content of murine articular cartilage than the DMB method or visual grading. The image analysis method makes it possible to measure changes in PG content of specific areas of articular cartilage with higher sensitivity than the DMB method and eliminating the bias inherent to visual grading by human observers.

Animals↗

PubMedDate not supplied

Significance of serine proteinase and matrix metalloproteinase systems in the destruction of human articular cartilage.

1. During the destruction of articular cartilage, fibrinolytic enzymes and matrix metalloproteinases (MMP) may contribute to the related pathology. The activities, antigens and messenger RNA (mRNA) levels of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) in articular cartilage were measured in patients with no history of joint diseases (control), those with osteoarthritis (OA) classified into osteophyte-formed site (OS) and weight-bearing site (WS), and in patients with rheumatoid arthritis (RA). 2. The uPA content was higher in WS and RA compared to normal. The PAI-1 content was higher in OS and RA compared to normal. Weight-bearing site patients expressed a high uPA mRNA level but a low PAI-1 mRNA level. Osteophyte-formed site patients expressed a low uPA mRNA level but a high PAI-1 mRNA level. 3. The levels of the MMP and mRNA of tissue inhibitors of metalloproteinases (TIMP) were measured in WS, OS, and RA. In WS, the levels of MMP were high and levels of TIMP mRNA expression low. In OS, the levels of TIMP were high and levels of MMP mRNA were low. In RA, the levels of MMP and TIMP mRNA were high. 4. These findings suggest that regulation of fibrinolysis may play an important role in the matrix of articular cartilage with arthropathy.

Aged↗