Intact Cartilage Surface Research Articles

Influence of synovia constituents on tribological behaviors of articular cartilage

Abstract The extremely low friction and minimal wear in natural synovial joints appear to be established by effective lubrication mechanisms based on appropriate combination of articular cartilage and synovial fluid. The complex structure of cartilage composed of collagen and proteoglycan with high water content contributes to high load-carrying capacity as biphasic materials and the various constituents of synovial fluid play important roles in various lubrication mechanisms. However, the detailed differences in functions of the intact and damaged cartilage tissues, and the interaction or synergistic action of synovia constituents with articular cartilage have not yet been clarified. In this study, to examine the roles of synovia constituents and the importance of cartilage surface conditions, the changes in friction were observed in the reciprocating tests of intact and damaged articular cartilage specimens against glass plate lubricated with lubricants containing phospholipid, protein and/or hyaluronic acid as main constituents in synovial fluid. The effectiveness of lubricant constituents and the influence of cartilage surface conditions on friction are discussed. In addition, the protectiveness by synovia constituents for intact articular cartilage surfaces is evaluated.

Src and fibroblast growth factor 2 independently regulate signaling and gene expression induced by experimental injury to intact articular cartilage

To investigate whether cartilage injury activates protein tyrosine kinases distinct from fibroblast growth factor (FGF)-related signaling, and whether they contribute to injury-induced gene responses. Phosphokinases and protein tyrosine phosphorylation were assayed by Western blotting of cartilage lysates. Immunoprecipitation and Western blotting with 4G10 antibody and immunoprecipitation kinase assay were carried out. Tyrosine-phosphorylated proteins on silver-stained gels of injured cartilage lysates were identified by mass spectrometry. Messenger RNA induction in cartilage explants was assessed by quantitative reverse transcriptase-polymerase chain reaction. Protein tyrosine phosphorylation occurred within seconds of injury to the surface of intact articular cartilage, as did activation of MAPKs and IKK. Activation did not reoccur upon reinjury of cultured explants. The prominent tyrosine-phosphorylated proteins focal adhesion kinase, paxillin, and cortactin were identified as substrates of Src family kinases. The Src family kinase inhibitor PP2 blocked injury-induced tyrosine phosphorylation. It did not prevent activation of the MAPKs and IKK but differentially inhibited 8 of 10 inflammatory response genes that were induced by injury. In contrast, FGF signaling blockade with PD173074 reduced all MAPK and IKK activation by ∼50% and inhibited a different subset of genes but had no effect on Src-like signaling. Injury to the surface of intact articular cartilage activates Src-like kinases as well as MAPKs and IKK (implying NF-κB activation). FGF-2 contributes to MAPK/IKK activation but not to Src-like signaling, suggesting that the latter is a parallel pathway that also regulates the injury-induced inflammatory gene response.

Bestimmung des Degenerationsgrads am hyalinen Gelenkknorpel durch Nah-Infrarot-Spektroskopie (NIRS): Methodenbeschreibung und Literaturübersicht

Damage to hyaline cartilage is the most important pathophysiological tool in the development of osteoarthritis. Cartilage lesions are the most frequent pathological findings during arthroscopic operations. Arthroscopies as well as magnetic resonance tomography are gold standards for detection of cartilage lesions. But the arthroscopic evaluation of cartilage lesions is descriptive and subjective only. The surgeon is able to differentiate between intact cartilage surface, softening, superficial or deep fissure or flake and finally a complete defect. In routine arthroscopy the grading mostly is made by use of different scores [e.g. ICRS (International Cartilage Repair Society), Outerbridge, Insall, Jäger-Wirth or others]. Because the arthroscopic evaluation is subjective the reliability of this method is poor. Spectroscopic methods are established for evaluation of different tissue diseases in different indications. NIRS (near infrared spectroscopy) has become an important method for medical diagnostics in the last years. NIR is very energy-rich and suitable for glass fibre transport without relevant reduction. Insofar this technology may be ideal for endoscopic procedures. Our systematic literature review reveals that NIRS is a sufficient method for an objective diagnosis of cartilage lesions. In the current work we demonstrate an NIRS-based device for intraoperative, real-time cartilage evaluation. Furthermore, we discuss the possible clinical consequences from such measurements.

Die Osteochondrosis dissecans und osteochondrale Läsionen des Talus: klinische und biomechanische Aspekte

The natural course of osteochondral lesions of the talus are varied and the disease pattern is not clearly defined. There is an ongoing discussion among clinicians concerning the aethiopathology and the correct treatment. In this article all relevant studies are analysed with regard to aetiology, long-term outcome and the different established treatment options. Against the background of the current biomechanical understanding, an approach is made to this controversially discussed disease pattern utilising our own biomechanical laboratory results. The available literature deals with longitudinal analyses regarding the natural history of the disease, conservative treatment, surgical options like debridement and anterograde drilling, retrograde drilling, osteochondral transplantation and autologous chondrocyte transplantation (ACT). Biomechanical trials describe high loads in the anterolateral parts of the joint. In most of the published studies the average age of the patients is around 28 years, younger patients have more favourable outcomes compared to older ones. In children the highest rate of spontaneous and advantageous course of the disease can be expected. Around 75% of the published outcomes relating to surgical therapy are satisfactory while 10% of the patients will suffer from osteoarthritis in the long term. While the aetiopathology of the disease remains unclear, histopathological studies reveal subcortical bone necrosis. In 90% of the cases there is an ankle sprain in the past medical history although a direct correlation with trauma as exclusive trigger is not obvious. A possible approach is an osteochondral fracture in combination with an already existing osteonecrosis. A staged treatment regime is advised. In asymptomatic cases conservative treatment is advocated independent of the stage. Symptomatic patients with Hepple stages I, II and V and intact cartilage surface should undergo retrograde drilling in combination with a subchondral filling with cancelleous bone. If a cartilage defect is present (Hepple stages III, IV, V), an osteochondral transplantation is reasonable. Only if the defect zone is >2.5 cm2 should a debridement combined with a transplantation of cancellous bone and an ACT be considered. The sole anterograde drilling in our opinion should only be performed as an exception.

Prevalence of naturally occurring cartilage defects in the ovine stifle (knee)

Purpose - To determine the prevalence, anatomical location and severity of cartilage defects in the stifle (knee) within a population of adult ewes enrolled for research. Methods - Animals: hind limbs (n= 60) from 30 adult ewes collected within 6 hours of euthanasia. Gross anatomical observation: the articular surfaces of the distal femur, proximal tibia and patella were examined by gross observation by two pairs of investigators. They scored the abnormalities of the hyaline cartilage using OARSI recommendations for ovine cartilage: score 0 for intact cartilage surface; score 1 for surface roughening; score 2 for deeper defects (fibrillation, fissures) not involving the subchondral bone; score 3 for small erosions down to subchondral bone (less than 5 mm diameter); score 4 for large erosions down to subchondral bone (more than 5 mm diameter). Scoring of articular surfaces was performed in 26 anatomic areas in each knee. Discrepancies were discussed between investigators and pairs till a consensus was reached. Histopathology: for each anatomical location where lesions had been identified, osteochondral slabs were obtained for histopathology. Samples were obtained in several regions with negative findings (score 0) for control. Conventional light microscopy [staining with Toluidine Blue and Safranin O) was performed to characterize structure of cartilage and bone, and confirm the classification of lesions performed by gross observation. Scoring and grading: the most severe lesion observed in each of the 26 anatomic regions was used to score the articular surface of that region. Grading of cartilage defects within each knee was obtained by the addition of the scores of all regions. Results - There were 23 Texel and 7 Iles de France ewes, aged 3 to 11 years, weighting between 38 and 72 kg, euthanized between May and October 2011. There were anatomical locations where cartilage defects were significantly (p < 0.05) more frequently identified than in others: central third of the medial femoral condyle (MFC2), axial aspect of the central third of the medial tibial condyle (AxMTC2), axial aspect of the central third of the lateral tibial condyle (AxLTC2). Score 2 defects were present respectively in 25, 31 and 15 % of all stifles on MFC2, AxMTC2 and AxLTC2 while score 1 surface abnormalities were present in 36, 25 and 5 % respectively. There was no effect of side (left or right), weight or breed on the grade of cartilage defect in the knee. Though not reaching statistical significance, grade increased moderately with age in this population (p = 0.08 and b= 0.02). Conclusions - This study demonstrated that score 2 cartilage defects can be significantly prevalent in stifles in a population of sheep enrolled for research. It indicates that, in Texel and Iles de France used for research, it is useful to assess cartilage status at baseline before including the animal in the experimentation, and to enroll, for each group of the trial, animals presenting either no cartilage defect or a same grade of defect. This should be assessed by non-invasive imaging modalities at baseline. Further research is required to evaluate the development of those lesions over time and compare imaging modalities in their ability to assess naturally occurring cartilage defects in the ovine stifle.

Chondrogenic Potential and Homogeneity of Cell Populations of Donor and Recipient Cells in a Fresh Osteochondral Allograft

Fresh osteochondral allografts have been widely used to treat cartilage lesions for more than 100 years1. Transplantation of cartilage and bone in the form of an allograft allows osseous healing while maintaining the articular cartilage architecture. This composite tissue transplant remains intact in vivo for extensive periods of time with a favorable mechanical and biological environment. The chondrocytes of the graft are thought to actively remodel the extracellular matrix environment, and thus contribute to the tissue integrity. We recently reported that allograft cells could survive up to twenty-nine years after transplantation without the need for systemic immunosuppression2. Although mosaic cell populations have been demonstrated in other forms of transplantation, these have always been under the umbrella of long-term systemic immunosuppression3,4. In a classic study, Langer and Gross5 showed that intact articular cartilage surfaces obtained by removing the subchondral bone of rat femoral heads and filling of the osseous segments with acrylic cement exhibited essentially no humoral immune response in contrast to that seen with minced cartilage or isolated chondrocyte transplants. This finding has been attributed to the so-called “immunoprivileged” status of articular cartilage, which protects the chondrocytes from the immune system of the host. The extent to which allograft chondrocytes retain their gene expression profiles and chondrogenic capacities remains unknown. Our goal was to compare gene expression, proliferation rate, and chondrogenic potential between host and allograft chondrocytes isolated three years after an unsuccessful fresh osteochondral allograft transplant in the knee. The patient was informed that data concerning her case would be submitted for publication, and she provided consent. The study was performed in full compliance with our institutional review board (IRB). Our IRB at University of California Davis Medical Center does not consider case reports to be research and does not …

Modeling chondrocyte patterns by elliptical cluster processes

Superficial zone chondrocytes (CHs) of human joints are spatially organized in distinct horizontal patterns. Among other factors, the type of spatial CH organization within a given articular surface depends on whether the cartilage has been derived from an intact joint or the joint is affected by osteoarthritis (OA). Furthermore, specific variations of the type of spatial organization are associated with particular states of OA. This association may prove relevant for early disease recognition based on a quantitative structural characterization of CH patterns. Therefore, we present a point process model describing the distinct morphology of CH patterns within the articular surface of intact human cartilage. This reference model for intact CH organization can be seen as a first step towards a model-based statistical diagnostic tool. Model parameters are fitted to fluorescence microscopy data by a novel statistical methodology utilizing tools from cluster and principal component analysis. This way, the complex morphology of surface CH patters is represented by a relatively small number of model parameters. We validate the point process model by comparing biologically relevant structural characteristics between the fitted model and data derived from photomicrographs of the human articular surface using techniques from spatial statistics.

Hypotonic challenge modulates cell volumes differently in the superficial zone of intact articular cartilage and cartilage explant

The objective of this study was to evaluate the effect of sample preparation on the biomechanical behaviour of chondrocytes. We compared the volumetric and dimensional changes of chondrocytes in the superficial zone (SZ) of intact articular cartilage and cartilage explant before and after a hypotonic challenge. Calcein-AM labelled SZ chondrocytes were imaged with confocal laser scanning microscopy through intact cartilage surfaces and through cut surfaces of cartilage explants. In order to clarify the effect of tissue composition on cell volume changes, Fourier Transform Infrared microspectroscopy was used for estimating the proteoglycan and collagen contents of the samples. In the isotonic medium (300 mOsm), there was a significant difference (p < 0.05) in the SZ cell volumes and aspect ratios between intact cartilage samples and cartilage explants. Changes in cell volumes at both short-term (2 min) and long-term (2 h) time points after the hypotonic challenge (180 mOsm) were significantly different (p < 0.05) between the groups. Further, proteoglycan content was found to correlate significantly (r(2) = 0.63, p < 0.05) with the cell volume changes in cartilage samples with intact surfaces. Collagen content did not correlate with cell volume changes. The results suggest that the biomechanical behaviour of chondrocytes following osmotic challenge is different in intact cartilage and in cartilage explant. This indicates that the mechanobiological responses of cartilage and cell signalling may be significantly dependent on the integrity of the mechanical environment of chondrocytes.

Imaging and Anatomic Study of the Pisiform Bone/Ulnar Nerve Relationship—Evaluation of the Preferred Surgical Approach for the Excision of the Pisiform Bone

This study examines the role of the pisiform bone/ulnar nerve relationship in determining the preferred surgical approach for the excision of the pisiform bone. An anatomic dissection of Guyon's canal on 10 fresh frozen cadaver wrists evenly divided between males and females was combined with magnetic resonance imaging (MRI) scans of 10 volunteer wrists. The 3 reported data points include the axial images determined on the MRI, the anatomic dissection related to the proximity of the ulnar nerve relative to the pisiform in defined positions of the wrist and the soft tissue envelope that surrounds the pisiform, and the proximity of the ulnar nerve as recorded, measured, and analyzed. An analysis of variance of the recorded data points was performed and the statistical results were presented (P value of P 05). Dissection and the MRI scans determined that the soft tissue envelope between the pisiform and ulnar nerve at Guyon's canal with neutral dorsiflexion was 2.5 mm. Palmar flexion was 3.0 mm and neutral flexion was 4.5 mm. The thinnest area was adjacent to the ulnar nerve proper on the volar radial aspect of the pisiform, on the basis of clock-faced analysis, between the 3 : 00 and 6 : 00 positions (the pisiform as a circle). The proximity of the pisiform in relation to the ulna and the limit of the soft tissue envelope would suggest that the preferred surgical approach, or that least likely to cause injury to the ulnar nerve, is one that is volar and includes excising the pisiform after exposing Guyon's canal.

Effect of Impaction Sequence on Osteochondral Graft Damage: The Role of Repeated and Varying Loads

Background Osteochondral autografts and allografts require mechanical force for proper graft placement into the defect site; however, impaction compromises the tissue. This study aimed to determine the effect of impaction force and number of hits to seat the graft on cartilage integrity. Hypothesis Under constant impulse conditions, higher impaction load magnitudes are more detrimental to cell viability, matrix integrity, and collagen network organization and will result in proteoglycan loss and nitric oxide release. Study Design Controlled laboratory study. Methods Osteochondral explants, harvested from fresh bovine trochleae, were exposed to a series of consistent impact loads delivered by a pneumatically driven device. Each plug received the same overall impulse of 7 Ns, reflecting the mean of 23 clinically inserted plugs. Impaction loads of 37.5 N, 75 N, 150 N, and 300 N were matched with 74, 37, 21, and 11 hits, respectively. After impaction, the plugs were harvested, and cartilage was analyzed for cell viability, histology by safranin-O and picrosirius red staining, and release of sulfated glycosaminoglycans (GAGs) and nitric oxide. Data were compared with nonimpacted controls. Results Impacted plugs had significantly lower cell viability than nonimpacted plugs. A dose-response relationship in loss of cell viability with respect to load magnitude was seen immediately and after 4 days but lost after 8 days. Histological analysis revealed intact cartilage surface in all samples (loaded or control), with loaded samples showing alterations in birefringence. While the sulfated GAG release was similar across varying impaction loads, release of nitric oxide increased with increasing impaction magnitudes and time. Conclusion Impaction loading parameters have a direct effect on the time course of the viability of the cartilage in the graft tissue. Clinical Relevance Optimal loading parameters for surgical impaction of osteochondral grafts are those with lower load magnitudes and a greater number of hits to ensure proper fit.

182 THE EFFECTS OF FUNGAL MONILIFORMIN TOXIN AND SELENIUM SUPPLEMENTATION ON CARTILAGE METABOLISM IN VITRO

sis (OA) in hamster articular cartilage during growth and development and how voluntary running exercise affects cartilage properties. Methods: Syrian Golden Hamsters were divided into five groups: 1-, 3and 6-month-old control groups and 3and 6-month-old runner groups. The runners had access to running wheels. The collagen network of medial tibial condyle articular cartilage was studied with quantitative polarized light microscopy. The glycosaminoglycan content was assessed from safranin-O stained sections using digital densitometry. Prevalence of OA was recorded from medial tibial condyle. Results: Runner animals were heavier than the controls (21% at 3 months and 13% at 6 months, p<0.001). The running distance was initially ca. 17km/day. The distance gradually decreased to 10km/day at the age of 3 and 6 months. By 3 months of age, cartilage thickness decreased 25% compared to that of 1month-old animals. Running did not change cartilage thickness. The collagen fibril orientation in cartilage demonstrated mostly similar profiles in controls and runners. The fibril orientation angle increased from the surface towards deep zones of cartilage (0 degree = fibrils parallel, 90 degrees = at right angles, with articular surface). The average fibril orientation angles in cartilage zones were 15 degrees, 36 degrees, 51 degrees and 48 degrees in the superficial, intermediate, upper deep and lower deep zones, respectively. At 6 months, the collagen fibrils of the superficial zone ran more parallel with the cartilage surface than at 1 or 3 months (p<0.05). Running caused the fibrils run more perpendicularly to the surface in the intermediate zone (p<0.05). The glycosaminoglycans increased from surface to deep zones during maturation. The glycosaminoglycan content was lower in the runner groups and especially in the superficial zone than in the controls (p<0.001-0.05). The incidence of OA increased with age. More normal-looking cartilage was found in the runner groups compared to controls (intact cartilage surface or with only minor fibrillation in 95% of runners vs. 75% in the 3-month-old control group; 58% in runners and 47% in the control group at 6 months). Conclusions: Collagen fibril orientation shows significant but not major changes during maturation of hamsters. Maturation makes superficial collagen fibrils run more parallel with the cartilage surface. After running the fibrils of the intermediate zone are more perpendicularly oriented. Running causes reduction of glycosaminoglycans in cartilage surface. Voluntary joint loading of the young hamsters appears to decrease the incidence of OA.

Diagnosis of Articular Cartilage Abnormalities of the Knee: Prospective Clinical Evaluation of a 3D Water-Excitation True FISP Sequence

To prospectively evaluate the accuracy of three-dimensional (3D) water-excitation true fast imaging with steady-state precession (FISP) in the assessment of cartilage abnormalities of the knee, by using surgery as the reference standard. The study was approved by the hospital institutional review board. Written informed consent was obtained from all patients. Twenty-nine patients (30 knees) with a mean age of 56 years (range, 18-86 years) were prospectively evaluated with a sagittal 3D true FISP magnetic resonance (MR) sequence. The mean interval between MR imaging and surgery was 1 day (range, 0-9 days). During surgery, the articular surfaces of the knee were evaluated by using a modified Noyes score. The MR images were evaluated by two blinded readers on two separate occasions. Diagnostic performance was evaluated by setting the cutoff for abnormality between grade 1 (intact cartilage surface) and grade 2 (cartilage defects). Statistical methods used included calculation of sensitivity, specificity, and accuracy, with 95% confidence intervals (Wilson score method) and calculation of kappa values with standard errors. Overall sensitivity, specificity, and accuracy for the two readers and the two evaluations ranged from 56% to 66%, 78% to 93%, and 71% to 75%, respectively. Interobserver agreement was substantial for both the first (kappa = 0.73) and the second (kappa = 0.65) evaluation. Intraobserver agreement was almost perfect (kappa = 0.84) for reader 1 and moderate (kappa = 0.60) for reader 2. The 3D water-excitation true FISP MR sequence allows assessment of the articular cartilage of the knee with moderate-to-high specificity and low-to-moderate sensitivity.

Quantitative ultrasound imaging of spontaneous repair of porcine cartilage

Arthroscopy offers qualitative means to evaluate the surface of articular cartilage. However, possible degeneration of the deep cartilage and subchondral bone remains undetected. High frequency ultrasound imaging is an advanced cartilage evaluation method which is conceivable to arthroscopic use and brings diagnostic information also from deeper cartilage and subchondral bone. In this study, we characterized spontaneous repair of porcine cartilage in situ with quantitative 2D-ultrasound imaging. At the age of 7-8 months, a cartilage lesion (diameter 6mm, not penetrating into subchondral bone) was created on the lateral facet of the right femoral trochlea (n=8). The animals were sacrificed 3 months after the surgery. The lesion site, adjacent cartilage and the corresponding control area at the contralateral (left) knee were imaged in situ with 20 MHz ultrasound. Ultrasound reflection coefficients were determined from the cartilage surface (R) and from the cartilage-bone interface (R(bone)). Microtopography of the articular surface was quantified by calculating ultrasound roughness index (URI) parameter from the ultrasonically determined surface profile. Lesion site was spontaneously filled with visually cartilage-like soft tissue with smooth surface. However, ultrasonic images and histological analyses revealed erosion of subchondral bone under the lesion site. Ultrasound reflection (R) at the surface of the spontaneously repaired tissue was significantly lower (-73.5+/-7.6%, P<0.05) than at the surface of intact cartilage. R(bone) was lowest at the lesion site. The surface roughness of spontaneously repaired cartilage was significantly higher than that of the intact tissue (44.0+/-26.0 microm vs 7.5+/-2.3 microm, P<0.05). Quantitative ultrasound parameters offered diagnostic information revealing impaired structural integrity of the spontaneously repaired porcine cartilage and subchondral bone. These changes are not detectable by traditional arthroscopic means.

Site-specific ultrasound reflection properties and superficial collagen content of bovine knee articular cartilage

Previous quantitative 2D-ultrasound imaging studies have demonstrated that the ultrasound reflection measurement of articular cartilage surface sensitively detects degradation of the collagen network, whereas digestion of cartilage proteoglycans has no significant effect on the ultrasound reflection. In this study, the first aim was to characterize the ability of quantitative 2D-ultrasound imaging to detect site-specific differences in ultrasound reflection and backscattering properties of cartilage surface and cartilage–bone interface at visually healthy bovine knee (n = 30). As a second aim, we studied factors controlling ultrasound reflection properties of an intact cartilage surface. The ultrasound reflection coefficient was determined in time (R) and frequency domains (IRC) at medial femoral condyle, lateral patello-femoral groove, medial tibial plateau and patella using a 20 MHz ultrasound imaging instrument. Furthermore, cartilage surface roughness was quantified by calculating the ultrasound roughness index (URI). The superficial collagen content of the cartilage was determined using a FT-IRIS-technique. A significant site-dependent variation was shown in cartilage thickness, ultrasound reflection parameters, URI and superficial collagen content. As compared to R and IRC, URI was a more sensitive parameter in detecting differences between the measurement sites. Ultrasound reflection parameters were not significantly related to superficial collagen content, whereas the correlation between R and URI was high. Ultrasound reflection at the cartilage–bone interface showed insignificant site-dependent variation. The current results suggest that ultrasound reflection from the intact cartilage surface is mainly dependent on the cartilage surface roughness and the collagen content has a less significant role.

In vitro engineered cartilage constructs produced by press-coating biodegradable polymer with human mesenchymal stem cells.

Cartilage constructs were fabricated by press-coating D,D-L,L-polylactic acid polymer blocks of 1 x 0.5 x 0.5 cm onto high-density cell pellets of 1.5 x 10(6) human mesenchymal stem cells (mhMSCs) isolated from the femoral head of patients undergoing total hip arthroplasty. Following attachment of the cell pellets to the polymer surfaces, chondrogenesis was induced by culturing the constructs for 3 weeks in a serum-free, chemically defined, chondrogenic differentiation medium supplemented with transforming growth factor beta-1 (TGF-beta1). Histochemical analysis showed that the press-coated pellets formed cell layers composed of morphologically distinct, chondrocyte-like cells, surrounded by a fibrous, sulfated proteoglycan-rich extracellular matrix. Immunohistochemical analysis detected collagen type II and cartilage proteoglycan link protein within the extracellular matrix. Expression of the cartilage-specific marker genes collagen types II, IX, X, and XI, and aggrecan was detected by RT-PCR. Scanning electron microscopy revealed organized and spatially distinct zones of cells within the cell-polymer constructs, with the superficial layer resembling compact hyaline cartilage. The fabrication method of press-coating biodegradable polymers with mhMSCs allows the in vitro production of cartilage constructs without harvesting chondrocytes from intact articular cartilage surfaces. These constructs may be applicable as prototypes for the reconstruction of articular cartilage defects in humans.

Polymorphonuclear leukocyte adhesion to articular cartilage is inhibited by cartilage surface macromolecules.

The present studies deal with polymorphonuclear neutrophil (PMN) adhesion inhibitory properties of cartilage surface proteoglycans. Normal human PMN were used in adhesion experiments with bovine cartilage surfaces exposed to neutrophil elastase and reconstituted with fibronectin (Fn) or on plastic-bound Fn. An extract of cartilage surface small proteoglycans (SE) and purified fibromodulin (FM), decorin (DCN), biglycan (BGN), and aggrecan (AGN) on the surface of normal cartilage were used to test for inhibition of Fn-dependent cell adhesion. The PMN did not adhere to intact articular cartilage surfaces, whereas significant adhesion was measured using cartilage explants digested with elastase and reconstituted with Fn. Incubation of elastase-treated, Fn-reconstituted cartilage with 45 microg/ml SE inhibited PMN adhesion by 50.7 +/- 5.8% (P < 0.0001). Addition of 50 microg/ml purified FM to the reconstituted articular surfaces inhibited cell adhesion by 71.2 +/- 13.9% (P < 0.0001). Inhibition of PMN adhesion to plastic-bound Fn was seen with 1.7 microg/ml SE (20.4 +/- 8.0%). Maximal inhibition of 67.4 +/- 14.8% (P < 0.01) was obtained with 17.0 microg/ml SE. With FM, concentrations of 4.3 microg/ml resulted in 34.7 25.2 inhibition (P < 0.001), and maximal inhibition of 66.3 16.2% (P < 0.01) was obtained with 43.0 microg/ml. Similar results were obtained with purified bovine DCN and BGN. The main component of cartilage matrix, AGN, failed to inhibit cell adhesion significantly. The results indicate that macromolecules normally present on articular cartilage surfaces act as a barrier to PMN adhesion. Since cartilage surface proteins are susceptible to breakdown by proteases from synovial fluid inflammatory cells, we postulate that the degradation of this barrier may be responsible for increasing PMN adhesion and subsequent cartilage damage in inflammatory arthritis.

Factors affecting the efficacy of bovine chondrocyte transplantation in vitro

Current therapies for osteoarthritis have been primarily directed at symptom relief rather than disease modification or cure. Improved understanding of cartilage biology and metabolism has permitted exploration of disease-modifying treatments for OA. Chondrocyte transplantation is one approach to disease modification that has received increasing attention. To date, most chondrocyte transplantation has focused on surgical implantation into isolated chondral defects.Our hypothesis is that cultured chondrocytes will preferentially transplant to hyaline cartilage after intraarticular injection. The purpose of this study was to quantify chondrocyte adherence to cartilage in an in-vitro bovine explant model under differing culture conditions. The effect on chondrocyte transplantation of time, of alginate vs. monolayer culture techniques, and of differing origin of tissue explants within the knee joint were assessed. The effect on transplantation of physically modifying the explant surface was also assessed. In addition to quantification of transplantation adherence, the morphology of transplanted chondrocytes was assessed with confocal and electron microscopy.Maximal adherence occurred by 24h post-transplantation. Baseline transplant densities exceeding 1×106cells/cm2were observed on unmodified cartilage surfaces. No significant differences in binding density were noted between cartilage explants obtained from the patella, femoral condyles, tibial plateaus or the trochlear groove. In addition, no differences in chondrocyte adherence were noted in cells cultured in monolayer or alginate beads. Transplanted chondrocytes were noted to be spherical irrespective of the culture methods employed. Notably, chondrocytes demonstrated significantly improved adherence to cartilage surfaces after the superficial layer was removed as compared to normal intact cartilage surfaces (increase of 26%, P< 0.01). This suggests that chondrocytes may preferentially adhere to cartilage surfaces where the superficial layer has been damaged, as is the case in isolated chondral lesions, or with diffuse cartilage degeneration.{copy}

Osteoarthritic cartilage fibrillation is associated with a decrease in chrondrocyte adhesion to fibronectin

Objective: Cartilage destruction in osteoarthritis (OA) is generally accepted as a failed repair process. Cell adhesion is implicated in tissue repair. Therefore, adhesion of OA chondrocytes to extracellular matrix proteins was investigated.Design: Using chondrocytes from human OA femoral head cartilage, adhesion to fibronectin and type II collagen of cells from distinct areas showing an intact cartilage surface or a fibrillated cartilage surface was studied. Modulation of chondrocyte adhesion by both protein kinase C (PKC) inhibitors and glucosamine sulfate (GS) was also investigated.Results: A significant (P<0.05) decrease in adhesion to fibronectin of chondrocytes from fibrillated cartilage, relative to those from grossly normal OA cartilage, was demonstrated. Adhesion to type II collagen was not modified by the chondrocyte origins (either from normal or fibrillated OA cartilage) Adhesion to fibronectin of cells from grossly intact cartilage was decreased by the addition of PKC and calmodulin-dependent kinase inhibitors, W7 and sphingosine, to the cell culture. Adhesion to fibronectin of chondrocytes from fibrillated cartilage was significantly (P<0.05) increased after glucosamine sulfate treatment.Conclusion: Fibrillation of cartilage from OA femoral head is associated with a defective adhesion of chondrocytes to fibronectin. The process is suggested to be dependent of PKC and/or calmodulin-dependent kinases and potentially reversible. Conceivably, it could play a role in OA cartilage destruction.

Osteoarthritis at the Base of the Thumb

Osteoarthritis at the base of the thumb is a functionally disabling condition and, as such, the basal joint complex represents the most commonly operated focus in the osteoarthritic upper extremity. Degenerative disease is predicted on instability of the trapeziometacarpal joint secondary to deterioration of the capsular and ligamentous restraints. Ligament reconstruction in the setting of a symptomatic hypermobile joint with intact cartilage surfaces may retard progression of arthritic disease. Complications related to silicone implant arthroplasty have given way to ligament reconstruction tendon interposition arthroplasty as the preferred procedure for the osteoarthritic thumb basal joint complex.

Mechanisms of disruption of the articular cartilage surface in inflammation. Neutrophil elastase increases availability of collagen type II epitopes for binding with antibody on the surface of articular cartilage.

We recently observed that specific antibodies to type II collagen do not bind in appreciable amounts to the intact surface of articular cartilage, whereas antibodies to the minor collagen types V, VI, and IX do. These results suggest that the outermost cartilage surface layer prevented interaction of the antibodies with the major collagen type in articular cartilage. The present studies were designed to investigate the pathogenic mechanisms involved in the disruption of the cartilage surface layer in inflammatory arthritis. Articular cartilage obtained from rabbits undergoing acute antigen-induced arthritis of 72 h duration showed a significant increase in binding of anti-type II antibody to cartilage surfaces compared with normal control cartilage (P less than 0.01). Augmentation of anti-type II binding was also observed upon in vitro incubation of bovine articular slices or intact rabbit patellar cartilage for 1 h with human polymorphonuclear neutrophils (PMN), PMN lysates, or purified human PMN elastase. This increase was not inhibited by sodium azide, nor was it enhanced by incubation of cartilage with the strong oxidant hypochlorous acid. Chondrocyte-mediated matrix proteoglycan degradation in cartilage explants cultured in the presence of cytokines failed to increase antibody binding appreciably. The augmentation in antibody binding seen with PMN lysates was inhibited by the nonspecific serine-esterase inhibitor PMSF, but not by the divalent metal chelator EDTA. The elastase-specific inhibitor AAPVCMK also inhibited most of the PMN-induced increase in antibody binding, whereas the cathepsin G-specific inhibitor GLPCMK was much less effective. Incubation of intact cartilage with purified human PMN elastase indicated that this serine esterase could account for the increase in anti-type II collagen antibody binding to intact cartilage surfaces. These studies suggest that in an inflammatory response, PMN-derived elastase degrades the outer layer of articular cartilage, exposing epitopes on type II collagen. They also help clarify the pathogenic mechanisms involved in early articular cartilage damage in inflammatory joint diseases.