Showing papers on "Cartilage published in 1997"
TL;DR: To define the patient population that might benefit from cartilage grafting, 31,516 knee arthroscopies were reviewed and the majority were articular cartilage lesions; grade III lesions of the patella were the most common and Grade IV lesions were predominantly located on the medial femoral condyle.
Abstract: Although articular cartilage injuries of the knee are common, injured cartilage has a limited ability to heal. Recent data suggest that articular cartilage grafting may provide treatment for these injuries. To define the patient population that might benefit from cartilage grafting, 31,516 knee arthroscopies were reviewed. Between June 1991 and October 1995, 53,569 hyaline cartilage lesions were documented in 19,827 patients. The majority were articular cartilage lesions; grade III lesions of the patella were the most common. Grade IV lesions were predominantly located on the medial femoral condyle. Patients under 40 years of age with grade IV lesions accounted for 5% of all arthroscopies; 74% of these patients had a single chondral lesion (4% of the arthroscopies). No associated ligamentous or meniscal pathology was found in 36.6% of these patients.
1,270 citations
TL;DR: The data suggest that collagenase(s) produced by chondrocytes is (are) involved in the cleavage and denaturation of type II collagen in articular cartilage, that this is increased in OA, and that MMP-13 may play a significant role in this process.
Abstract: We demonstrate the direct involvement of increased collagenase activity in the cleavage of type II collagen in osteoarthritic human femoral condylar cartilage by developing and using antibodies reactive to carboxy-terminal (COL2-3/4C(short)) and amino-terminal (COL2-1/4N1) neoepitopes generated by cleavage of native human type II collagen by collagenase matrix metalloproteinase (MMP)-1 (collagenase-1), MMP-8 (collagenase-2), and MMP-13 (collagenase-3). A secondary cleavage followed the initial cleavage produced by these recombinant collagenases. This generated neoepitope COL2-1/4N2. There was significantly more COL2-3/4C(short) neoepitope in osteoarthritis (OA) compared to adult nonarthritic cartilages as determined by immunoassay of cartilage extracts. A synthetic preferential inhibitor of MMP-13 significantly reduced the unstimulated release in culture of neoepitope COL2-3/4C(short) from human osteoarthritic cartilage explants. These data suggest that collagenase(s) produced by chondrocytes is (are) involved in the cleavage and denaturation of type II collagen in articular cartilage, that this is increased in OA, and that MMP-13 may play a significant role in this process.
997 citations
TL;DR: The view that adult articular cartilage is an inert bearing surface, like high-density polyethylene or metal, and that degeneration of the articular surface with age is the result of mechanical wear with inevitable, irreversible loss of structure and mechanical performance resulting from joint use is supported.
Abstract: Joint pain and loss of mobility are among the most common causes of impairment in middle-aged and older people36,134. In many instances, the degeneration of articular cartilage and alterations in other joint tissues that result from the loss of structure and function of articular cartilage cause the pain and the loss of motion28,46,47,85,118,150. This occurs most frequently in the clinical syndrome of idiopathic or primary osteoarthrosis, but it may also result from joint injury or from developmental, metabolic, and inflammatory disorders that destroy the articular surface, causing secondary osteoarthrosis28,46,118. An understanding of the degeneration of articular cartilage, osteoarthrosis, and the potential for restoring an articular surface depends to a large extent on an appreciation of the biological behavior and the responsiveness of articular cartilage to injury and disease. Of considerable importance is the observation, first reported centuries ago and confirmed by multiple investigators over the last fifty years, that adult articular cartilage does not have the capacity to repair structural damage resulting from injury or disease29,32,71. This observation has contributed to the view that adult articular cartilage is an inert bearing surface, like high-density polyethylene or metal, and that degeneration of the articular surface with age is the result of mechanical wear with inevitable, irreversible loss of structure and mechanical performance resulting from joint use62. The implication of this view is that, other than limiting joint use or loading, little or nothing can be done to prevent the degeneration of articular cartilage, and the most appropriate treatment for advanced degeneration of cartilage leading to the clinical syndrome of osteoarthrosis is replacement of the articular surface. Alternatively, if articular cartilage is …
738 citations
TL;DR: In this article, a polyglycolic acid-polylactic acid template was seeded with chondrocytes isolated from bovine articular cartilage and then implanted into subcutaneous pockets on the dorsa of 10 athymic mice.
Abstract: This study evaluates the feasibility of growing tissue-engineered cartilage in the shape of a human ear using chondrocytes seeded onto a synthetic biodegradable polymer fashioned in the shape of a 3-year-old child's auricle. A polymer template was formed in the shape of a human auricle using a nonwoven mesh of polyglycolic acid molded after being immersed in a 1% solution of polylactic acid. Each polyglycolic acid-polylactic acid template was seeded with chondrocytes isolated from bovine articular cartilage and then implanted into subcutaneous pockets on the dorsa of 10 athymic mice. The three-dimensional structure was well maintained after removal of an external stent that had been applied for 4 weeks. Specimens harvested 12 weeks after implantation and subjected to gross morphologic and histologic analysis demonstrated new cartilage formation. The overall geometry of the experimental specimens closely resembled the complex structure of the child's auricle. These findings demonstrate that polyglycolic acid-polylactic acid constructs can be fabricated in a very intricate configuration and seeded with chondrocytes to generate new cartilage that would be useful in plastic and reconstructive surgery.
640 citations
TL;DR: The delineation of the depth‐dependent modulus provides a basis for detailed study of the relationship between the composition, structure, and function of cartilage in such processes as aging, repair, and degeneration.
626 citations
TL;DR: In the future, physiologic repair also may become possible using mesenchymal stem cells or chondrocytes delivered surgically in an ex vivo-derived matrix to allow implantation of mature biosynthetic grafts which would allow treatment of larger defects with decreased rehabilitation and morbidity.
Abstract: Over time, articular cartilage loses the capacity to regenerate itself, making repair of articular surfaces difficult. Lavage and debridement may offer temporary relief of pain for up to 4.5 years, but offer no prospect of long-term cure. Likewise, marrow-stimulation techniques such as drilling, microfracture, or abrasion arthroplasty fail to yield long-term solutions because they typically promote the development of fibrocartilage. Fibrocartilage lacks the durability and many of the mechanical properties of the hyaline cartilage that normally covers articular surfaces. Repair tissue resembling hyaline cartilage can be induced to fill in articular defects by using perichondrial and periosteal grafts. However, these techniques are limited by the amount of tissue available for grafting and the tendency toward ossification of the repair tissue. Autogenous osteochondral arthroscopically implanted grafts (mosaicplasty), or open implantation of lateral patellar facet (Outerbridge technique), requires violation of subchondral bone. Osteochondral allografts risk viral transmission of disease and low chondrocyte viability, in addition to removal of host bone for implantation. Autologous chondrocyte implantation offers the opportunity to achieve biologic repair, enabling the surgeon to repair the joint surface with autologous articular cartilage. With this technique, care must be taken to ensure the safety, viability, and microbial integrity of the autologous cells while they are expanded in culture over a 4- to 5-week period prior to implantation. Surgical implantation requires equal attention to meticulous technique. In the future, physiologic repair also may become possible using mesenchymal stem cells or chondrocytes delivered surgically in an ex vivo-derived matrix. This would allow in vitro manipulation of cells with growth factors, mechanical stimuli, and matrix sizing to allow implantation of mature biosynthetic grafts which would allow treatment of larger defects with decreased rehabilitation and morbidity.
506 citations
TL;DR: The data suggest that TGF-β may be critical for multifaceted maintenance of synovial joints, and is thought to be involved in a feedback loop that signals through the periosteum/ perichondrium to inhibit cartilage differentiation.
Abstract: Members of the TGF-beta superfamily are important regulators of skeletal development. TGF-betas signal through heteromeric type I and type II receptor serine/threonine kinases. When over-expressed, a cytoplasmically truncated type II receptor can compete with the endogenous receptors for complex formation, thereby acting as a dominant-negative mutant (DNIIR). To determine the role of TGF-betas in the development and maintenance of the skeleton, we have generated transgenic mice (MT-DNIIR-4 and -27) that express the DNIIR in skeletal tissue. DNIIR mRNA expression was localized to the periosteum/perichondrium, syno-vium, and articular cartilage. Lower levels of DNIIR mRNA were detected in growth plate cartilage. Transgenic mice frequently showed bifurcation of the xiphoid process and sternum. They also developed progressive skeletal degeneration, resulting by 4 to 8 mo of age in kyphoscoliosis and stiff and torqued joints. The histology of affected joints strongly resembled human osteo-arthritis. The articular surface was replaced by bone or hypertrophic cartilage as judged by the expression of type X collagen, a marker of hypertrophic cartilage normally absent from articular cartilage. The synovium was hyperplastic, and cartilaginous metaplasia was observed in the joint space. We then tested the hypothesis that TGF-beta is required for normal differentiation of cartilage in vivo. By 4 and 8 wk of age, the level of type X collagen was increased in growth plate cartilage of transgenic mice relative to wild-type controls. Less proteoglycan staining was detected in the growth plate and articular cartilage matrix of transgenic mice. Mice that express DNIIR in skeletal tissue also demonstrated increased Indian hedgehog (IHH) expression. IHH is a secreted protein that is expressed in chondrocytes that are committed to becoming hypertrophic. It is thought to be involved in a feedback loop that signals through the periosteum/ perichondrium to inhibit cartilage differentiation. The data suggest that TGF-beta may be critical for multifaceted maintenance of synovial joints. Loss of responsiveness to TGF-beta promotes chondrocyte terminal differentiation and results in development of degenerative joint disease resembling osteoarthritis in humans.
498 citations
TL;DR: Both neoepitopes were also detected by immunohistochemistry in articular cartilage from patients undergoing joint replacement for osteoarthritis, rheumatoid arthritis, and in Cartilage from adults with no known joint disease.
Abstract: To examine the activity of matrix metalloproteinases (MMPs) and aggrecanase in control and diseased human articular cartilage, metabolic fragments of aggrecan were detected with monospecific antipeptide antibodies The distribution and quantity of MMP-generated aggrecan G1 fragments terminating in VDIPEN341 were compared with the distribution of aggrecanase-generated G1 fragments terminating in NITEGE373 Both types of G1 fragments were isolated from osteoarthritic cartilage The sizes were consistent with a single enzymatic cleavage in the interglobular domain region, with no further proteolytic processing of these fragments Both neoepitopes were also detected by immunohistochemistry in articular cartilage from patients undergoing joint replacement for osteoarthritis (OA), rheumatoid arthritis (RA), and in cartilage from adults with no known joint disease In control specimens, the staining intensity for both G1 fragments increased with age, with little staining in cartilage from 22-wk-old fetal samples There was also an increase with age in the extracted amount of MMP-generated neoepitope in relation to both aggrecan and collagen content, confirming the immunohistochemical results After the age of 20-30 yr this relationship remained at a steady state The staining for the MMP-generated epitope was most marked in control cartilage exhibiting histological signs of damage, whereas intense staining for the aggrecanase-generated fragment was often noted in adult cartilage lacking overt histological damage Intense staining for both neoepitopes appeared in the more severely fibrillated, superficial region of the tissue Intense immunostaining for both VDIPEN- and NITEGE- neoepitopes was also detected in joint cartilage from patients with OA or RA Cartilage in these specimens was significantly more degraded and high levels of staining for both epitopes was always seen in areas with extensive cartilage damage The levels of extracted VDIPEN neoepitope relative to collagen or aggrecan in both OA and RA samples were similar to those seen in age-matched control specimens Immunostaining for both types of aggrecan fragments was seen surrounding the cells but also further removed in the interterritorial matrix In some regions of the tissue, both neoepitopes were found while in others only one was detected Thus, generation and/or turnover of these specific catabolic aggrecan fragments is not necessarily coordinated Our results are consistent with the presence in both normal and arthritic joint cartilage of proteolytic activity against aggrecan based on both classical MMPs and "aggrecanase"
479 citations
TL;DR: The data suggest that Gd(DTPA)(2-)-enhanced MR imaging has potential for monitoring glycosaminoglycan content of cartilage in vivo.
Abstract: PURPOSE: To investigate the feasibility of applying magnetic resonance (MR) imaging with use of an anionic compound, Gd(DTPA)2- (gadolinium diethylenetriamine-pentaacetic acid), for measuring glycosaminoglycan concentration in human cartilage in clinical studies. MATERIALS AND METHODS: Penetration of Gd(DTPA)2- into cartilage was monitored through sequential T1-calculated images obtained after intraarticular (n = 2) or intravenous (n = 2) injection. T1-weighted and T1-calculated image series were then obtained in seven volunteers (nine knees) after penetration of Gd-(DTPA)2- into cartilage. If T1 was heterogeneous on Gd(DTPA)(2-)-enhanced images, images were also obtained after penetration of the cartilage with the nonionic contrast agent, gadoteridol. RESULTS: Gd(DTPA)2- penetrated cartilage from the articular surface after intraarticular injection and from both the articular surface and the subchondral bone after intravenous injection. The latter resulted in shorter overall penetration time. T1 values o...
461 citations
TL;DR: This study demonstrates the importance of carrier material for the purpose of cartilage tissue reconstruction in vitro by determining the effect of a variety of materials on chondrocyte growth and extracellular matrix synthesis.
Abstract: Injury to articular cartilage predisposes that joint to further degeneration and eventually osteoarthritis. Recent studies have demonstrated the feasibility of using chondrocytes together with different biomaterial carriers as grafts for the repair of cartilage defects. The following study was undertaken to determine the effect of a variety of these materials on chondrocyte growth and extracellular matrix synthesis. We cultured chondrocytes on several commonly used materials and compared their rates of synthesis of proteoglycan and collagen. Additionally, we evaluated them in a closed culture recirculating system on these materials and compared them with standard culture techniques. This was done to see whether such a bioreactor-type system can be used to enhance the quality of in vitro reconstructed tissues. Our results demonstrated marked variability with respect to how chondrocytes responded to culture on the various materials. Bioabsorbable polymers such as polyglycolic acid (PGA)-enhanced proteoglycan synthesis, whereas collagen matrices stimulated synthesis of collagen. The use of the closed culture system, in general, improved the rates of synthesis of collagen and proteoglycan on the different material scaffolds. Exceptions were collagen synthesis on collagen matrices: use of the closed culture system did not enhance the rate of synthesis. Rates of proteoglycan synthesis on PGA scaffold initially was higher in the closed culture system but did not sustain a difference over the entire course of the 3-week culture period. This study demonstrates the importance of carrier material for the purpose of cartilage tissue reconstruction in vitro. © 1997 John Wiley & Sons, Inc.
450 citations
TL;DR: Tissue engineering of cartilage was studied on the Mir Space Station and on Earth to study the feasibility of long-term cell culture flight experiments and to assess the effects of spaceflight on the growth and function of a model musculoskeletal tissue.
Abstract: Tissue engineering of cartilage, i.e., the in vitro cultivation of cartilage cells on synthetic polymer scaffolds, was studied on the Mir Space Station and on Earth. Specifically, three-dimensional cell-polymer constructs consisting of bovine articular chondrocytes and polyglycolic acid scaffolds were grown in rotating bioreactors, first for 3 months on Earth and then for an additional 4 months on either Mir (10(-4)-10(-6) g) or Earth (1 g). This mission provided a unique opportunity to study the feasibility of long-term cell culture flight experiments and to assess the effects of spaceflight on the growth and function of a model musculoskeletal tissue. Both environments yielded cartilaginous constructs, each weighing between 0.3 and 0.4 g and consisting of viable, differentiated cells that synthesized proteoglycan and type II collagen. Compared with the Earth group, Mir-grown constructs were more spherical, smaller, and mechanically inferior. The same bioreactor system can be used for a variety of controlled microgravity studies of cartilage and other tissues. These results may have implications for human spaceflight, e.g., a Mars mission, and clinical medicine, e.g., improved understanding of the effects of pseudo-weightlessness in prolonged immobilization, hydrotherapy, and intrauterine development.
TL;DR: The data indicate that human OA-affected cartilage in ex vivo conditions shows superinduction of PGE2 due to upregulation of COX-2, and spontaneous release of NO that acts as an autacoid to attenuate the production of the COx-2 products such as P GE2.
Abstract: Cartilage specimens from osteoarthritis (OA)-affected patients spontaneously released PGE2 at 48 h in ex vivo culture at levels at least 50-fold higher than in normal cartilage and 18-fold higher than in normal cartilage + cytokines + endotoxin. The superinduction of PGE2 production coincides with the upregulation of cyclooxygenase-2 (COX-2) in OA-affected cartilage. Production of both nitric oxide (NO) and PGE2 by OA cartilage explants is regulated at the level of transcription and translation. Dexamethasone inhibited only the spontaneously released PGE2 production, and not NO, in OA-affected cartilage. The NO synthase inhibitor HN(G)-monomethyl-L-arginine monoacetate inhibited OA cartilage NO production by > 90%, but augmented significantly (twofold) the spontaneous production of PGE2 in the same explants. Similarly, addition of exogenous NO donors to OA cartilage significantly inhibited PGE2 production. Cytokine + endotoxin stimulation of OA explants increased PGE2 production above the spontaneous release. Addition of L-NMMA further augmented cytokine-induced PGE2 production by at least fourfold. Inhibition of PGE2 by COX-2 inhibitors (dexamethasone or indomethacin) or addition of exogenous PGE2 did not significantly affect the spontaneous NO production. These data indicate that human OA-affected cartilage in ex vivo conditions shows (a) superinduction of PGE2 due to upregulation of COX-2, and (b) spontaneous release of NO that acts as an autacoid to attenuate the production of the COX-2 products such as PGE2. These studies, together with others, also suggest that PGE2 may be differentially regulated in normal and OA-affected chondrocytes.
TL;DR: The capacity of rhBMP-2 to accelerate the healing of full-thickness defects of articular cartilage and to improve the histological appearance and biochemical characteristics of the repair cartilage is described.
Abstract: Articular cartilage has a limited capacity for repair. We investigated the effect of rhBMP-2 (recombinant human bone morphogenetic protein-2) on the healing of full-thickness osteochondral defects in adult New Zealand White rabbits. A single defect, three millimeters wide by three millimeters deep, was created in the trochlear groove of the right femur in eighty-nine rabbits. The defect was either left empty, filled with a plain collagen sponge, or filled with a collagen sponge impregnated with five micrograms of rhBMP-2. The animals were killed at four, eight, or twenty-four weeks, and the repair tissue was examined histologically and evaluated with use of a grading scale. The defects also were examined immunohistochemically for the presence of type-II collagen at four and eight weeks. The rate of bone repair was evaluated with fluorescent labeling of bone at two and four weeks and with use of fluorescence microscopy at eight weeks. Treatment with rhBMP-2 greatly accelerated the formation of new subchondral bone and improved the histological appearance of the overlying articular surface. At twenty-four weeks, the thickness of the repair cartilage was 70 per cent that of the normal adjacent cartilage and a new tidemark usually had formed between the repair cartilage and the underlying subchondral bone. The average total scores on the histological grading scale were significantly better (p < 0.01) for the defects treated with rhBMP-2 than for the untreated defects (those left empty or filled with a plain collagen sponge) at all time-points. Immunostaining with an antibody against type-II collagen showed the diffuse presence of this cartilage-specific collagen throughout the repair cartilage in the treated defects. The untreated defects demonstrated minimum staining with this antibody. CLINICAL RELEVANCE: The operative removal of cartilage damaged as a result of trauma or focal osteoarthrosis is of little value because of the limited capability of articular cartilage to repair. If the damaged cartilage were to be removed and the tissue were induced to heal, the self-perpetuating process of osteoarthrosis might be prevented. We describe the capacity of rhBMP-2 to accelerate the healing of full-thickness defects of articular cartilage and to improve the histological appearance and biochemical characteristics of the repair cartilage. These improvements were evident as long as twenty-four weeks postoperatively in adult rabbits. Because of the technical simplicity of delivering a recombinant protein growth factor compared with transplanting cells, and because of the improvement in healing afforded by rhBMP-2, the use of this growth factor and related proteins to influence the healing of defects of articular cartilage should be investigated further.
Journal Article•
TL;DR: The optimal number of the appropriate cells delivered in a supportive vehicle to a defect pretreated with a dilute trypsin solution to optimize the integration of repair with normal host cartilage provides a methodology in which regeneration of articular cartilage can be observed.
Abstract: An experimental approach and logic are presented for the regeneration of skeletal tissues that focus on the recapitulation of embryonic events starting with an uncommitted progenitor cell population that the authors refer to as mesenchymal stem cells. The repair and regeneration of articular cartilage, which itself has no repair potential, is the subject of this presentation. Full thickness cartilage defects were created in the medial condyle of the distal femur. Self repair (empty defects), articular chondrocytes (allografts), and autologous mesenchymal stem cells were used and the results are reported in selected examples from more than 800 rabbit knees. The optimal number of the appropriate cells delivered in a supportive vehicle to a defect pretreated with a dilute trypsin solution to optimize the integration of repair with normal host cartilage provides a methodology in which regeneration of articular cartilage can be observed. The principles have relevance to the clinical repair and regeneration of cartilage and other skeletal defects.
TL;DR: When a sufficient dose of MIA is used, this model can easily and quickly reproduce OA-like lesions and functional impairment in rats, similar to that observed in human disease.
Abstract: Objective. To characterize the doseresponsiveness of morphologic and biochemical chondral changes relative to mobility in mono-iodoacetate (MIA)-induced osteoarthritis (OA) in rats.
Methods. Rat mobility was assessed by biotelemetry. Articular lesions were characterized by macroscopic and histologic examinations. Cartilage proteoglycan metabolism was evaluated by the 1,9-dimethylmethylene blue dye binding assay and by radiosulfate incorporation in patellar cartilage.
Results. Spontaneous locomotor activity was rapidly, transiently, and dose-dependently decreased after MIA injection into rat knees (primary response). Thereafter, only high doses (0.3 mg and 3.0 mg) led to a secondary progressive long-term loss of spontaneous mobility on day 15, when subchondral bone was exposed. These 2 doses resulted in significant changes in cartilage proteoglycan concentration at day 15 and a strong inhibition of anabolism in the peripheral patellae by day 2, contrasting with the effects of lower doses (0.01, 0.03, and 0.1 mg).
Conclusion. When a sufficient dose of MIA is used, this model can easily and quickly reproduce OA-like lesions and functional impairment in rats, similar to that observed in human disease. These parameters, as well as proteoglycan metabolism, could serve as indicators for studying chondroprotective drugs, or for evaluating the ability of imaging techniques to detect and evaluate chondral lesions.
TL;DR: The objective of the present study was to determine the effect of cultured autologous chondrocytes on healing in an adult canine model with use of histomorphometric methods to assess the degree of repair.
Abstract: Articular cartilage has a limited capacity for repair. In recent clinical and animal experiments, investigators have attempted to elicit the repair of defects of articular cartilage by injecting cultured autologous chondrocytes under a periosteal flap (a layer of periosteum). The objective of the present study was to determine the effect of cultured autologous chondrocytes on healing in an adult canine model with use of histomorphometric methods to assess the degree of repair. A total of forty-four four-millimeter-diameter circular defects were created down to the zone of calcified cartilage in the articular cartilage of the trochlear groove of the distal part of the femur in fourteen dogs. The morphology and characteristics of the original defects were defined in an additional six freshly created defects in three other dogs. Some residual non-calcified articular cartilage, occupying approximately 2 per cent of the total cross-sectional area of the defect, was sometimes left in the defect. The procedure sometimes damaged the calcified cartilage, resulting in occasional microfractures or larger fractures, thinning of the zone of calcified cartilage, or, rarely, small localized penetrations into subchondral bone. The forty-four defects were divided into three treatment groups. In one group, cultured autologous chondrocytes were implanted under a periosteal flap. In the second group, the defect was covered with a periosteal flap but no autologous chondrocytes were implanted. In the third group (the control group), the defects were left empty. The defects were analyzed after twelve or eighteen months of healing. Histomorphometric measurements were made of the percentage of the total area of the defect that became filled with repair tissue, the types of tissue that filled the defect, and the integration of the repair tissue with the adjacent cartilage at the sides of the defects and with the calcified cartilage at the base of the defect. In histological sections made through the center of the defects in the three groups, the area of the defect that filled with new repair tissue ranged from a mean total value of 36 to 76 per cent, with 10 to 23 per cent of the total area consisting of hyaline cartilage. Integration of the repair tissue with the adjacent cartilage at the edges of the defect ranged from 16 to 32 per cent in the three groups. Bonding between the repair tissue and the calcified cartilage at the base of the defect ranged from 41 to 89 per cent. With the numbers available, we could detect no significant difference among the three groups with regard to any of the parameters used to assess the quality of the repair. In the two groups in which a periosteal flap was sutured to the articular cartilage surrounding the defect, the articular cartilage showed degenerative changes that appeared to be related to that suturing. CLINICAL RELEVANCE: The technique of injecting cultured autologous chondrocytes under a periosteal flap recently was introduced to treat defects in the articular cartilage of humans. The long-term efficacy of this treatment is unknown. An animal model was developed to evaluate the procedure and its effectiveness.
TL;DR: The type II matrix may be of value as a vehicle for chondrocyte implantation on the basis of the higher percentage of chONDrocytes retaining spherical morphology and greater biosynthetic activity that was reflected in the greater increase of GAG content.
Abstract: Synthetic and natural absorbable polymers have been used as vehicles for implantation of cells into cartilage defects to promote regeneration of the articular joint surface. Implants should provide a pore structure that allows cell adhesion and growth, and not provoke inflammation or toxicity when implanted in vivo. The scaffold should be absorbable and the degradation should match the rate of tissue regeneration. To facilitate cartilage repair the chemical structure and pore architecture of the matrix should allow the seeded cells to maintain the chondrocytic phenotype, characterized by synthesis of cartilage-specific proteins. We investigated the behavior of canine chondrocytes in two spongelike matrices in vitro: a collagen-glycosaminoglycan (GAG) copolymer produced from bovine hide consisting of type I collagen and a porous scaffold made of type II collagen by extraction of porcine cartilage. Canine chondrocytes were seeded on both types of matrices and cultured for 3 h, 7 days, and 14 days. The histology of chondrocyte-seeded implants showed a significantly higher percentage of cells with spherical morphology, consistent with chondrocytic morphology, in the type II sponge at each time point. Pericellular matrix stained for proteoglycans and for type II collagen after 14 days. Biochemical analysis of the cell seeded sponges for GAG and DNA content showed increases with time. At day 14 there was a significantly higher amount of DNA and GAG in the type II matrix. This is the first study that directly compares the behavior of chondrocytes in type I and type II collagen matrices. The type II matrix may be of value as a vehicle for chondrocyte implantation on the basis of the higher percentage of chondrocytes retaining spherical morphology and greater biosynthetic activity that was reflected in the greater increase of GAG content.
TL;DR: These findings suggest a key role of M MP-13 and MMP-8, as well as MMP -1 in osteoarthritis, suggesting local modulation by mechanical and inflammatory factors.
Abstract: Objective. To assess the presence of fibroblast collagenase (MMP-1), neutrophil collagenase (MMP-8), and collagenase 3 (MMP-13) in osteoarthritic (OA) cartilage, with particular emphasis on areas of macroscopic cartilage erosion.
Methods. Messenger RNA (mRNA) levels were assessed by reverse transcriptase-polymerase chain reaction (RT-PCR), in situ hybridization, and Northern blot analysis.
Results. MMP-1 and MMP-13 were expressed at higher levels by OA chondrocytes than by normal chondrocytes. In addition, mRNA for MMP-8 was present in OA cartilage but not normal cartilage by PCR and Northern blot analyses. Chondrocytes from areas surrounding the OA lesion expressed greater quantities of MMP-1 and MMP-13 compared with normal chondrocytes, suggesting local modulation by mechanical and inflammatory factors. Tumor necrosis factor α stimulated the expression of all 3 collagenases. Retinoic acid, an agent which induces autodigestion of cartilage in vitro, stimulated only the expression of MMP-13.
Conclusion. These findings suggest a key role of MMP-13 and MMP-8, as well as MMP-1 in osteoarthritis.
TL;DR: The results suggest that MMP‐13 plays an important role in the extracellular matrix remodeling during fetal bone development both via endochondral and intramembranous ossification.
Abstract: Collagenase-3 (MMP-13) is a novel matrix metalloproteinase, the expression of which has so far only been documented in human breast carcinomas and osteoarthritic cartilage. In this study we have examined the expression of MMP-13 during human fetal development. Northern blot hybridizations revealed abundant expression of MMP-13 mRNAs in total RNA from fetal cartilage and calvaria at gestational age of 15 weeks. By in situ hybridization MMP-13 transcripts were detected in chondrocytes of hypertrophic cartilage in vertebrae of the spinal column and in the dorsal end of ribs undergoing ossification, as well as in osteoblasts and periosteal cells below the inner periosteal region of ossified ribs. In contrast, no expression of MMP-13 could be detected in osteoclasts. Furthermore, expression of MMP-13 mRNA was detected in osteoblasts and fibroblasts primarily on the inner side of calvarial bone of the skull at 16 weeks of gestation. Expression of MMP-13 mRNA by primary human fetal chondrocytes in culture was enhanced by transforming growth factor-beta (TGF-beta) and inhibited by bone morphogenetic protein-2 (BMP-2). No expression of MMP-13 mRNA could be noted in other fetal tissues, including the skin, lungs, neural tissue, muscle, and liver. These results suggest that MMP-13 plays an important role in the extracellular matrix remodeling during fetal bone development both via endochondral and intramembranous ossification.
TL;DR: It is demonstrated that ATDC5 cells keep track of the multistep differentiation process encompassing the stages from mesenchymal condensation to calcification in vitro, as well as the molecular mechanism underlying regulation of cartilage differentiation during endochondral bone formation.
Abstract: During the process of endochondral bone formation, proliferating chondrocytes give rise to hypertrophic cells, which then deposit a mineralized matrix to form calcified cartilage prior to replacement by bone. Previously, we reported that a clonal cell line, ATDC5, undergoes efficient chondrogenic differentiation through a cellular condensation stage. Here we report that the differentiated ATDC5 cells became hypertrophic at the center of cartilage nodules, when the cells ceased to grow. Formation of hypertrophic chondrocytes took place in association with type X collagen gene expression and a dramatic elevation of alkaline phosphate (ALPase) activity. After 5 weeks of culture, mineralization of the culture could be discerned as Alizarin red-positive spots, which spread throughout the nodules even in the absence of beta-glycerophosphate. Electron microscopy and electron probe microanalysis revealed that calcification was first initiated at matrix vesicles in the territorial matrix and that it advanced progressively along the collagen fibers in a manner similar to that which occurs in vivo. The infrared spectrum of the mineralized nodules indicated two absorption doublets around 1030 cm-1 and 600 cm-1, which are characteristic of apatitic mineral. Calcifying cultures of ATDC5 cells retained responsiveness to parathyroid hormone (PTH): PTH markedly inhibited elevation of ALPase activity and calcification in the culture in a dose-dependent manner. Thus, we demonstrated that ATDC5 cells keep track of the multistep differentiation process encompassing the stages from mesenchymal condensation to calcification in vitro. ATDC5 cells provide an excellent model to study the molecular mechanism underlying regulation of cartilage differentiation during endochondral bone formation.
TL;DR: The results suggest that T1ρ measurements are selectively sensitive to proteoglycan content, and the potential of this method in distinguishing the early degenerative changes in cartilage associated with osteoarthritis is discussed.
Abstract: Spin-lattice relaxation in the rotating frame (T1rho) dispersion spectroscopy and imaging were used to study normal and enzymatically degraded bovine articular cartilage. Normal specimens demonstrate significant T1rho "dispersion" (approximately 60 to approximately 130 ms) in the 100 Hz to 9 kHz frequency range. Proteoglycan-degraded specimens have 33% greater T1rho values than collagen-degraded or normal samples. T1rho-weighted images reveal structure not found in conventional T1- or T2-weighted images. Our results suggest that T1rho measurements are selectively sensitive to proteoglycan content. The potential of this method in distinguishing the early degenerative changes in cartilage associated with osteoarthritis is discussed.
TL;DR: To test the ability of MSCs to heal a critical-sized segmental defect, syngeneic culture-expanded MSCS were loaded onto a porous cylinder of hydroxyapatite/tricalcium phosphate (HA/TCP) and implanted in an 8-mm segmentsal defect in the femora of adult rats.
Abstract: Bone marrow has been shown to contain a population of rare cells capable of differentiating into the cells that form bone, cartilage, and other connective tissues. These cells, referred to as mesen...
TL;DR: Results indicate that cleavage at the metalloproteinase and Aggrecanase sites are quantitatively important events in aggrecan catabolism in both articular cartilage and intervertebral disc in vivo.
Abstract: Aggrecan degradation in human intervertebral disc and articular cartilage has been studied by using anti-neoepitope antibodies specific for the N-terminal degradation products generated by cleavage within the interglobular domain at the metalloproteinase and aggrecanase sites. Immunoblot analysis of extracts of annulus fibrosus, nucleus pulposus and articular cartilage demonstrated age-related patterns in the abundance of both degradation products. In all three tissues the metalloproteinase-generated fragment was present at very low levels in young individuals but increased in abundance with age. In the disc tissues, the abundance of this degradation product levelled off in the juvenile; for cartilage this occurred in early adulthood. Despite these temporal differences, the levels attained in adults were comparable for the three tissues. In contrast, the aggrecanase-generated degradation product exhibited tissue-specific differences in the variation of its abundance with age. Whereas this degradation product increased with age in annulus fibrosus and articular cartilage and had levelled off by adulthood, in nucleus pulposus it was present in greatest abundance in young individuals and decreased to very low levels with age. Examination of discs exhibiting various degrees of degeneration did not reveal any differences in the levels of the metalloproteinase and aggrecanase-generated cleavage products that could not be accounted for by differences in age. In adults the product of aggrecanase action was much more abundant in articular cartilage than in either of the disc tissues, despite the age-related increase also observed for annulus fibrosus. Analysis of tissue extracts with an antibody recognizing the G1 domain of aggrecan identified two major degradation products whose abundance and size were correlated with the fragments detected by the anti-neoepitope antibodies. Taken together, these results indicate that cleavage at the metalloproteinase and aggrecanase sites are quantitatively important events in aggrecan catabolism in both articular cartilage and intervertebral disc in vivo. Moreover the two enzyme systems act independently and exhibit differences in the degree to which they contribute to aggrecan degradation in these tissues.
TL;DR: A novel, two-layered, collagen matrix seeded with chondrocytes for repair of articular cartilage allowed sustained hyaline-like repair ofArticular defects during the entire six-month period of observation.
Abstract: We have developed a novel, two-layered, collagen matrix seeded with chondrocytes for repair of articular cartilage. It consists of a dense collagen layer which is in contact with bone and a porous matrix to support the seeded chondrocytes. The matrices were implanted in rabbit femoral trochleas for up to 24 weeks. The control groups received either a matrix without cells or no implant. The best histological repair was seen with cell-seeded implants. The permeability and glycosaminoglycan content of both implant groups were nearly normal, but were significantly less in tissue from empty defects. The type-II collagen content of the seeded implants was normal. For unseeded implants it was 74.3% of the normal and for empty defects only 20%. The current treatments for articular injury often result in a fibrous repair which deteriorates with time. This bilayer implant allowed sustained hyaline-like repair of articular defects during the entire six-month period of observation.
TL;DR: Based on these results, the absolute levels of COMP in SF and serum, and its fragmentation pattern in SF, seem to be promising as markers of joint tissue metabolism.
Abstract: We determined the tissue distribution of cartilage oligomeric matrix protein (COMP) in man and evaluated COMP in synovial fluid (SF) and serum. COMP was purified from human articular cartilage. Polyclonal antibodies were used to detect COMP in tissue cryosections and protein extracts. COMP was determined quantitatively and qualitatively in SF and serum by competitive enzyme-linked immunosorbent assay and immunoblotting. Knee joint SF was taken from nine cadaveric and six living controls, 52 patients with osteoarthritis (OA), 85 patients with rheumatoid arthritis (RA) and 60 patients with other forms of inflammatory arthritis. The degradative potential of SF on native COMP was tested in vitro. The highest concentrations of COMP were measured in articular cartilage and meniscus, the lowest in rib and trachea. Compared with controls, the concentrations of COMP in SF and serum were elevated in 36 and 50% of the patients. A total of 84% of patients with RA and 60% of patients with other forms of inflammatory arthritis showed significant amounts of low-molecular-weight COMP fragments (50-70 kDa) in SF. In contrast, SF fragments were present in only 21% of the OA patients. Furthermore, 13% of SF taken from patients with RA or other forms of inflammatory arthritis were able to degrade COMP in vitro. Using inhibitors, the involvement of serine proteinases could be demonstrated in only 8% of the cases. Based on these results, the absolute levels of COMP in SF and serum, and its fragmentation pattern in SF, seem to be promising as markers of joint tissue metabolism.
TL;DR: The zone of calcified cartilage (ZCC) forms an important interface between cartilage and bone for transmitting force, attaching cartilage to bone, and limiting diffusion from bone to the deeper layers of cartilage.
Abstract: The zone of calcified cartilage (ZCC) forms an important interface between cartilage and bone for transmitting force, attaching cartilage to bone, and limiting diffusion from bone to the deeper layers of cartilage. The height of the ZCC is a relatively constant percent of articular cartilage and the height is maintained by a balance between progression of the tidemark into the unmineralized cartilage and changing into bone by vascular invasion and bony remodeling. During its formation, the cells that form the ZCC have properties similar to the cells of the growth plate. In the adult, the ZCC becomes quiescent but not inactive. The ZCC may be reactivated in osteoarthritis and may progressively calcify the unmineralized cartilage. This might contribute to cartilage thinning which would increase the concentration of forces across the uncalcified cartilage leading to more damage. Although the subchondral bony plate remodels extensively in osteoarthritis, there is little evidence that a change in the biomechanics of the plate directly initiates the osteoarthritic process in cartilage. However, increased repair by endochondral ossification of vertical cracks in the ZCC that penetrate into the marrow space could contribute to progression via changes in the ZCC.
TL;DR: It is concluded that changes in the subchondral mineralized tissues are not required for initiation of cartilage fibrillation, but may be necessary for progression, and that only changes in bone and calcified cartilage close to the joint are significant to the disease process.
Abstract: This paper reviews evidence for the role of subchondral bone and calcified cartilage in the initiation and progression of osteoarthrosis (OA). There is consensus that OA is characterized by subchondral sclerosis, but disagreement about whether bone changes are concurrent with, primary to, or secondary to cartilage deterioration. Clinical observation suggests that bone density and cartilage fibrillation are inversely related. Evidence from the rabbit impulsive loading model is consistent with early bone changes, but evidence from other models of subchondral stiffening, such as the sheep metallic implant model, do not strongly support this idea. However, evidence from tibial angulation models and from the Pond-Nuki (anterior cruciate ligament resection) model show evidence that bone changes precede cartilage fibrillation temporally, and are associated spatially within a single joint. Evidence is also presented for the importance of calcified cartilage changes in pre-disposing the joint towards progression to OA. Microdamage accumulation and repair by vascular invasion may be a component of the pathogenesis of OA in some cases, but more work is needed to demonstrate this conclusively. We conclude that changes in the subchondral mineralized tissues are not required for initiation of cartilage fibrillation, but may be necessary for progression, and that only changes in bone and calcified cartilage close to the joint are significant to the disease process.
TL;DR: Cartilage tympanoplasty offers the possibility of a rigorous TM reconstruction with excellent postoperative hearing results, and analysis of the PTA‐ABG as a function of percentage of TM reconstructed showed no statistically significant difference in hearing results due to percentage of cartilage used.
Abstract: Cartilage has shown promise as a graft material to close perforations in the tympanic membrane (TM), particularly in cases of advanced middle ear pathology. Although it is similar to fascia, its more rigid quality tends to resist resorption and retraction. However, it is this rigid quality that has led many to anticipate a significant conductive hearing loss when using cartilage to reconstruct the TM. Because little has been reported in the literature comparing hearing results using cartilage with results using other grafting materials, this retrospective study was conducted to compare the hearing results of patients with cartilage tympanoplasty with results in patients who underwent revision tympanoplasty using perichondrium. Both series of patients had undergone type I tympanoplasty, and the middle ear pathology was considered to be similar between the two groups. TM closure was achieved in all 22 patients undergoing cartilage reconstruction, but three of the 20 patients undergoing perichondrium reconstruction had a recurrent perforation during the follow-up period (approximately 1 year). The average pre- and postoperative pure-tone average air-bone gap (PTA-ABG) was 21.1 dB and 6.8 dB for the cartilage group and 17.9 dB and 7.7 dB for the perichondrium group, respectively. These gains in hearing were statistically significant (P < 0.001 in each case), but there was no statistically significant difference in hearing results between the two groups. Analysis of the PTA-ABG as a function of percentage of TM reconstructed showed no statistically significant difference in hearing results due to percentage of cartilage used. These results indicate that cartilage tympanoplasty offers the possibility of a rigorous TM reconstruction with excellent postoperative hearing results.
TL;DR: The findings reveal that hypertrophic chondrocytes can qualitatively modulate their production of matrix vesicles and only when induced to initiate mineralization, will release mineralization-competent matrixVesicles rich in annexin V and alkaline phosphatase.
Abstract: Matrix vesicles have a critical role in the initiation of mineral deposition in skeletal tissues, but the ways in which they exert this key function remain poorly understood. This issue is made even more intriguing by the fact that matrix vesicles are also present in nonmineralizing tissues. Thus, we tested the novel hypothesis that matrix vesicles produced and released by mineralizing cells are structurally and functionally different from those released by nonmineralizing cells. To test this hypothesis, we made use of cultures of chick embryonic hypertrophic chondrocytes in which mineralization was triggered by treatment with vitamin C and phosphate. Ultrastructural analysis revealed that both control nonmineralizing and vitamin C/phosphatetreated mineralizing chondrocytes produced and released matrix vesicles that exhibited similar round shape, smooth contour, and average size. However, unlike control vesicles, those produced by mineralizing chondrocytes had very strong alkaline phosphatase activity and contained annexin V, a membrane-associated protein known to mediate Ca2+ influx into matrix vesicles. Strikingly, these vesicles also formed numerous apatite-like crystals upon incubation with synthetic cartilage lymph, while control vesicles failed to do so. Northern blot and immunohistochemical analyses showed that the production and release of annexin V-rich matrix vesicles by mineralizing chondrocytes were accompanied by a marked increase in annexin V expression and, interestingly, were followed by increased expression of type I collagen. Studies on embryonic cartilages demonstrated a similar sequence of phenotypic changes during the mineralization process in vivo. Thus, chondrocytes located in the hypertrophic zone of chick embryo tibial growth plate were characterized by strong annexin V expression, and those located at the chondro–osseous mineralizing border exhibited expression of both annexin V and type I collagen. These findings reveal that hypertrophic chondrocytes can qualitatively modulate their production of matrix vesicles and only when induced to initiate mineralization, will release mineralization-competent matrix vesicles rich in annexin V and alkaline phosphatase. The occurrence of type I collagen in concert with cartilage matrix calcification suggests that the protein may facilitate crystal growth after rupture of the matrix vesicle membrane; it may also offer a smooth transition from mineralized type II/type X collagen-rich cartilage matrix to type I collagen-rich bone matrix.