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PubMed2001

Biomechanics and repair of articular cartilage.

The most important function of the joints relies on excellent lubrication and the uniform distribution of impact loads onto the underlying bones, together with damping effects. In most joint disorders, as the lesion is limited to the joint surface, it becomes necessary to repair the joint surface. In this article, repair with an artificial composite osteochondral device (COD) is reported, as is biological resurfacing with cultured chondrocytes. The COD consists of polyvinyl alcohol (PVA) hydrogel as artificial cartilage and titanium fiber mesh (TFM) as porous artificial bone. PVA solution was impregnated into the pores of TFM by injection molding, and these two materials were bound together by a gelling process to create the COD. The key problem, i.e., to attain quick and firm attachment to the underlying bone, was addressed by creating this COD, in which the TFM interface allows not only firm attachment of the PVA gel but also strong attachment to the joint surface through bony ingrowth. For the purpose of simulating partial hemiarthroplasty for the femoral head, 30 COD prostheses were implanted into canine femoral heads. Histological findings of the acetabular cartilage and synovial membrane, as well as findings of attachment of the prosthesis to bone, were examined for an 18-month period after the operation. No particular pathological changes in acetabular cartilage were found, and firm attachment of the devices to bone was confirmed. These results indicate that the COD could be a very promising joint repair material.

Animals↗
PubMed2006

Microstructural modeling of collagen network mechanics and interactions with the proteoglycan gel in articular cartilage.

Cartilage matrix mechanical function is largely determined by interactions between the collagen fibrillar network and the proteoglycan gel. Although the molecular physics of these matrix constituents have been characterized and modern imaging methods are capable of localized measurement of molecular densities and orientation distributions, theoretical tools for using this information for prediction of cartilage mechanical behavior are lacking. We introduce a means to model collagen network contributions to cartilage mechanics based upon accessible microstructural information (fibril density and orientation distributions) and which self-consistently follows changes in microstructural geometry with matrix deformations. The interplay between the molecular physics of the collagen network and the proteoglycan gel is scaled up to determine matrix material properties, with features such as collagen fibril pre-stress in free-swelling cartilage emerging naturally and without introduction of ad hoc parameters. Methods are developed for theoretical treatment of the collagen network as a continuum-like distribution of fibrils, such that mechanical analysis of the network may be simplified by consideration of the spherical harmonic components of functions of the fibril orientation, strain, and stress distributions. Expressions for the collagen network contributions to matrix stress and stiffness tensors are derived, illustrating that only spherical harmonic components of orders 0 and 2 contribute to the stress, while orders 0, 2, and 4 contribute to the stiffness. Depth- and compression-dependent equilibrium mechanical properties of cartilage matrix are modeled, and advantages of the approach are illustrated by exploration of orientation and strain distributions of collagen fibrils in compressed cartilage. Results highlight collagen-proteoglycan interactions, especially for very small physiological strains where experimental data are relatively sparse. These methods for determining matrix mechanical properties from measurable quantities at the microscale (composition, structure, and molecular physics) may be useful for investigating cartilage structure-function relationships relevant to load-bearing, injury, and repair.

Biomechanical Phenomena↗
PubMed2006

Storage of porcine articular cartilage at high subzero temperatures.

OBJECTIVE: Transplantation of osteochondral allograft tissue can treat large joint defects but is limited by tissue availability, surgical timing, and infectious disease transmission. Fresh allografts perform the best but requirements for infectious disease testing delay the procedure with subsequent decrease in cell viability and function. Hypothermic storage at lower temperatures can extend tissue banking time without loss of cell viability and, therefore, increase the supply of allograft tissue. This study investigated the effects of different cryoprotectant solutions on intact AC at various subzero temperatures. DESIGN: 10 mm porcine osteochondral dowels were immersed for 30 minutes in various combinations of solutions [(XVIVO, propylene glycol (51% w/w), sucrose (46% w/w)] cooled to various subzero temperatures (-10, -15, and -20 degrees C), and held for 30 min. After warming, 70 mum slices were stained with membrane integrity dyes, viewed under fluorescence microscopy and cell recovery calculated relative to fresh controls. RESULTS: Results demonstrated excellent cell recovery (>75%) at -10 degrees C provided ice did not form. Excellent cell recovery (>70%) occurred at -15 degrees C in solutions containing 51% propylene glycol but formation of extra-matrix ice in other solutions resulted in significant cell loss. All groups had <6% cell recovery at -20 degrees C and propylene glycol did not provide a protective effect even though extra-matrix ice did not form CONCLUSIONS: These results suggest that extra-matrix ice plays an important role in cell damage during cryopreservation. Excellent cell recovery can be obtained after storage at subzero temperatures if ice does not form. Hypothermic preservation at high subzero temperatures may extend AC storage time in tissue banks compared to current techniques.

Animals↗
PubMed2006

Dimethyl sulfoxide toxicity kinetics in intact articular cartilage.

Osteochondral defects can degenerate into osteoarthritis and currently there are no good treatment alternatives available to most Orthopaedic surgeons. Osteochondral allografting can restore damaged joint surfaces but its clinical use is limited by poor access to high quality tissue. Vitrification of osteochondral tissue would allow the banking of this tissue but requires high concentrations of cryoprotective agents. This study was designed to ascertain dimethyl sulfoxide (DMSO) toxicity kinetics to chondrocytes in situ after exposure to DMSO at different temperatures recorded as a function of time. Porcine osteochondral dowels were exposed to 1, 3, 5, and 6M DMSO at 4, 22, and 37 degrees C for 0.5 min to 120 min. Chondrocyte recovery was determined by membrane integrity (Syto 13 and ethidium bromide) and mitochondrial (WST-1) assays. Results demonstrated that cell recovery was concentration, temperature and time dependent. At higher concentrations and temperatures, significant cell loss occurred within minutes. A rate constant calculated for chondrocyte death was dependent on temperature. 1 M DMSO appeared relatively non-toxic. This experiment established a method to examine systematically toxicity parameters for chondrocytes in situ and this data can be used to tailor vitrification protocols by limiting exposure temperature and time or lowering DMSO concentrations below toxic levels recorded.

Animals↗
PubMed2006

Lectin and other histochemical studies of the articular cartilage and the chondro-osseous junction of the normal human knee joint.

There are few studies on normal, adult diarthrodial joints which look in detail at the histochemical properties of the chondro-osseous junctional region. This study of the normal human knee joint was performed using lectin and other histochemical techniques. There were differences in the reactions of mineralised cartilage compared to those of hyaline cartilage with the former demonstrating more collagen and less glycosaminoglycans. Lectin histochemistry revealed more accessible terminal 2-deoxy,2-acetamido-alpha-D: -galactose and more N-acetyllactosamine but less fucosyl and alpha-2,6-linked-sialyl termini in the mineralised cartilage. The hyaline cartilage chondrocytes stained for N-glycans but those of mineralised cartilage did not. The staining patterns of prolongations and islands of uncalcified cartilage running through the calcified layer to abut bone and marrow spaces were distinct, resembling the patterns of the hyaline cartilage but with some unique features. A possible relationship was revealed between the presence of the Maclura pomifera ligand (Galbeta1,3GalNAcalpha1-) and mineralisation. Subchondral bone had a markedly restricted glycoprofile.

Adult↗
PubMed2002

Articular cartilage calcification and matrix vesicles.

There has been much research in calcium-containing crystal deposition diseases of hereditary and sporadic type. Synovial cell-induced inflammation and secondary cartilage damage are common in these diseases. In most cases of these diseases and in primary osteoarthritis, there are mineral deposits in the cartilage, mineral crystals in the synovial fluid, and aberrations of pyrophosphate metabolism.

Animals↗
PubMed1989

Molecular and immunologic differences in canine fibronectins from articular cartilage and plasma.

Two new monoclonal antibodies (Mabs) which reacted with canine fibronectin were produced and characterized. Data supported the conclusion that the epitope recognized by Mab 1H9A4 is within the first three Type III homology repeats of the Hep 2 domain and that the epitope for Mab 13G3B7 is within the last Type III homology repeat of fibronectin. These antibodies, along with three others, Mabs IST-2, IST-7, and IST-9, produced and characterized in the laboratories of L. Zardi of Genoa, Italy, were used to characterize canine cartilage and plasma fibronectin. In addition, cartilage explants were labeled with [35S]methionine in order to characterize newly synthesized cartilage fibronectin. The following observations were made. (i) Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (NaDodSO4-PAGE) of reduced canine plasma fibronectin revealed a characteristic doublet; reduced cartilage fibronectin revealed two major bands and one minor band. The lower molecular weight band was 10 kDa less than the beta subunit of plasma fibronectin. In Western blots, this band stained with Mab 1H9A4 but failed to react with Mab 13G3B7. (ii) Western blots of thermolysin and trypsin digests of cartilage fibronectin revealed cleavage patterns which differed from those obtained from digestions of plasma fibronectin. (iii) The ED-A sequence, detected by Mab IST-9, was present in less than 2% of the cartilage fibronectins. (iv) NaDodSO4-PAGE of purified and reduced 35S-labeled fibronectin revealed two major radioactive bands and one minor radioactive band which comigrated with the fibronectin from the cartilage but not with plasma fibronectin. We concluded that like "cellular" fibronectin, the ratio of alpha-type subunits to beta subunits was greater than 4 to 1 in cartilage fibronectin compared to 1.25 to 1 for plasma fibronectin; however, cartilage fibronectin was not a cellular fibronectin by the criterion of the presence of the ED-A sequence. Another difference between plasma and cartilage fibronectin was the presence in cartilage fibronectin of a subpopulation of subunits on which the last Type III homology repeat could not be detected. Biosynthetic data were consistent with the concept that cartilage fibronectin originates from local synthesis by the chondrocyte.

Animals↗
PubMed1991

Transforming growth factor-beta 1 stimulates synthesis of proteoglycan aggregates in calf articular cartilage organ cultures.

Previous work showed that transforming growth factor-beta 1 (TGF-beta 1), added alone to bovine cartilage organ cultures, stimulated [35S]sulfate incorporation into macromolecular material but did not investigate the fidelity of the stimulated system to maintain synthesis of cartilage-type proteoglycans. This paper provides evidence that chondrocytes synthesize the appropriate proteoglycan matrix under TGF-beta 1 stimulation: (i) there is a coordinated increase in hyaluronic acid and proteoglycan monomer synthesis, (ii) link-stable proteoglycan aggregates are assembled, (ii) the hybrid chondroitin sulfate/keratan sulfate monomeric species is synthesized, and (iv) there is an increase in protein core synthesis. Some variation in glycosylation patterns was observed when proteoglycans synthesized under TGF-beta 1 stimulation were compared to those synthesized under basal conditions. Thus comparing TGF-beta 1 to basal samples respectively, the monomers were larger (Kav on Sepharose CL-2B = 0.29 vs 0.41), the chondroitin sulfate chains were longer by approximately 3.5 kDa, the percentage of total glycosaminoglycan in keratan sulfate increased slightly from approximately 4% (basal) to approximately 6%, and the unsulfated disaccharide decreased from 28% (basal) to 12%. All of these variations are in the direction of a more anionic proteoglycan. Since the ability of proteoglycans to confer resiliency to the cartilage matrix is directly related to their anionic nature, these changes would presumably have a beneficial effect on tissue function.

Animals↗