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Cartilage Homeostasis (cartilage + homeostasi)
Selected AbstractsInvolvement of the cytoskeletal elements in articular cartilage homeostasis and pathologyINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 1 2009Emma J. Blain Summary The cytoskeleton of all cells is a three-dimensional network comprising actin microfilaments, tubulin microtubules and intermediate filaments. Studies in many cell types have indicated roles for these cytoskeletal proteins in many diverse cellular processes including alteration of cell shape, movement of organelles, migration, endocytosis, secretion, cell division and extracellular matrix assembly. The cytoskeletal networks are highly organized in structure enabling them to fulfil their biological functions. This review will primarily focus on the organization and function of the three major cytoskeletal networks in articular cartilage chondrocytes. Articular cartilage is a major load-bearing tissue of the synovial joint; it is well known that the cytoskeleton acts as a physical interface between the chondrocytes and the extracellular matrix in ,sensing' mechanical stimuli. The effect of mechanical load on cytoskeletal element expression and organization will also be reviewed. Abnormal mechanical load is widely believed to be a risk factor for the development of osteoarthritis. Several studies have intimated that the major cytoskeletal networks are disorganized or often absent in osteoarthritic cartilage chondrocytes. The implications and possible reasoning for this are more widely discussed and placed into context with their potential relevance to disease and therapeutic strategies. [source] Type II collagen modulates the composition of extracellular matrix synthesized by articular chondrocytesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2003Wen-Ning Qi Abstract The articular cartilage extracellular matrix (ECM) interfaces with chondrocytes and influences many biological processes important to cartilage homeostasis and repair. The alginate bead culture system can be viewed as a model of cartilage repair in which the chondrocyte attempts to recreate the pericellular matrix while maintaining a differentiated phenotype. The purpose of this study was to evaluate the alteration in epitopes of proteoglycan and tenascin synthesized by chondrocytes in the presence of exogenous extracellular type II collagen. We evaluated the effects on four biomarkers associated with the creation of the denovo matrix using ELISA and immunohistochemistry: keratan sulfate epitope (5D4), 3B3(,) neoepitope of chondroitin-6- sulfate, 3B3(+) chondroitinase-generatedepitope of chondroitin-6-sulfate, and tenascin-C expression. TGF-,1 stimulated the production of 3B3(+), 5D4, and tenascin-C in a dose-dependent manner and decreased 3B3(,) levels. Following the addition of exogenous type II collagen, 3B3(,) increased and tenascin-C decreased but did not change the direction of TGF-,1 effects. In contrast, 5D4 expression decreased in the presence of collagen II as TGF-,1 increased to 10 ng/ml. Interestingly, the amount of 3B3(+) epitope was not affected by the incorporation of type II collagen. Immunohistochemistry found there was no significant difference in distribution of these biomarkers in the presence and absence of extracellular type II collagen incorporation. These results elucidate the subtle biochemical differences in ECM synthesized by chondrocytes in the presence of type II collagen and further characterize the role played by ECM in the TGF-,1 regulation of the articular cartilage physiology. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Effect of oleocanthal and its derivatives on inflammatory response induced by lipopolysaccharide in a murine chondrocyte cell lineARTHRITIS & RHEUMATISM, Issue 6 2010Anna Iacono Objective In joint diseases, cartilage homeostasis is disrupted by mechanisms that are driven by combinations of biologic factors that vary according to the disease process. In osteoarthritis (OA), biomechanical stimuli predominate, with up-regulation of both catabolic and anabolic factors. Likewise, OA progression is characterized by increased nitric oxide (NO) production, which has been associated with cartilage degradation. Given the relevance of cartilage degenerative diseases in our society, the development of a novel pharmacologic intervention is a critically important public health goal. Recently, oleocanthal isolated from extra virgin olive oil was found to display nonsteroidal antiinflammatory drug activity similar to that of ibuprofen, a drug widely used in the therapeutic management of joint inflammatory diseases. We undertook this study to evaluate the effect of oleocanthal and its derivatives on the modulation of NO production in chondrocytes. Methods Cultured ATDC-5 chondrocytes were tested with different doses of oleocanthal and its derivatives. Cell viability was evaluated using the MTT assay. Nitrite accumulation was determined in culture supernatant using the Griess reaction. Inducible NO synthase (NOS2) protein expression was examined using Western blotting analysis. Results Oleocanthal and its derivatives decreased lipopolysaccharide-induced NOS2 synthesis in chondrocytes without significantly affecting cell viability at lower concentrations. Among the derivatives we examined, derivative 231 was the most interesting, since its inhibitory effect on NOS2 was devoid of cytotoxicity even at higher concentrations. Conclusion This class of molecules shows potential as a therapeutic weapon for the treatment of inflammatory degenerative joint diseases. [source] Hypoxia-inducible factor 1, inhibits the fibroblast-like markers type I and type III collagen during hypoxia-induced chondrocyte redifferentiation: Hypoxia not only induces type II collagen and aggrecan, but it also inhibits type I and type III collagen in the hypoxia-inducible factor 1,,dependent redifferentiation of chondrocytesARTHRITIS & RHEUMATISM, Issue 10 2009Elise Duval Objective Autologous chondrocyte implantation requires expansion of cells ex vivo, leading to dedifferentiation of chondrocytes (loss of aggrecan and type II collagen to the profit of type I and type III collagens). Several approaches have been described for redifferentiation of these cells. Among them, low oxygen tension has been exploited to restore the differentiated chondrocyte phenotype, but molecular mechanisms of this process remain unclear. However, under conditions of hypoxia, one of the major factors involved is hypoxia-inducible factor 1, (HIF-1,). The purpose of this study was to investigate the role of HIF-1, during human chondrocyte redifferentiation. Methods We used complementary approaches to achieving HIF-1, loss (inhibition by cadmium ions and dominant-negative expression) or gain (ectopic expression and cobalt ion treatment) of function. Expression of chondrocyte, as well as fibroblast-like, phenotype markers was determined using real-time reverse transcription,polymerase chain reaction and Western blot analyses. Binding activities of HIF-1, and SOX9, a pivotal transcription factor of chondrogenesis, were evaluated by electrophoretic mobility shift assays and by chromatin immunoprecipitation assay. Results We found that hypoxia and HIF-1, not only induced the expression of SOX9, COL2A1, and aggrecan, but they simultaneously inhibited the expression of COL1A1, COL1A2, and COL3A1. In addition, we identified the binding of HIF-1, to the aggrecan promoter, the first such reported demonstration of this binding. Conclusion This study is the first to show a bimodal role of HIF-1, in cartilage homeostasis, since HIF-1, was shown to favor specific markers and to impair dedifferentiation. This suggests that manipulation of HIF-1, could represent a promising approach to the treatment of osteoarthritis. [source] Profiling microRNA expression in bovine articular cartilage and implications for mechanotransductionARTHRITIS & RHEUMATISM, Issue 8 2009Walter Dunn Objective Articular cartilage is an avascular tissue with precise polarity and organization comprising 3 distinct functional zones: the surface, middle, and deep zones. Each zone has a different gene expression pattern that plays a specific role in articular cartilage development and maintenance. MicroRNA (miRNA) are small noncoding gene products that play an important regulatory role in determining cell differentiation and function. The purpose of this study was to test our hypothesis that miRNA expression profiles in the different articular cartilage zones as well as between regions subjected to different levels of weight-bearing stresses are unique. Methods Using an miRNA microarray approach in conjunction with quantitative reverse transcription,polymerase chain reaction, we identified miRNA in bovine articular cartilage that were differentially expressed in the different functional zones and in the anterior weight-bearing and posterior non,weight-bearing regions of the medial femoral condyle (M1 and M4, respectively). Results We identified miRNA-221 and miR-222 as part of a subset of differentially expressed miRNA that were up-regulated in articular cartilage in the anterior, M1, greater weight-bearing location. Additionally, miR-126, miR-145, and miR-335 were down-regulated in monolayers of tissue-cultured chondrocytes as compared with levels determined directly from intact native cartilage. Conclusion In conclusion, miR-222 expression patterns in articular cartilage are higher in the weight-bearing anterior medial condyle as compared with the posterior non,weight-bearing medial condyle. Thus, miR-222 might be a potential regulator of an articular cartilage mechanotransduction pathway. These data implicate miRNA in the maintenance of articular cartilage homeostasis and are therefore targets for articular cartilage tissue engineering and regenerative medicine. [source] In vitro stage-specific chondrogenesis of mesenchymal stem cells committed to chondrocytesARTHRITIS & RHEUMATISM, Issue 2 2009Wei-Hong Chen Objective Osteoarthritis is characterized by an imbalance in cartilage homeostasis, which could potentially be corrected by mesenchymal stem cell (MSC),based therapies. However, in vivo implantation of undifferentiated MSCs has led to unexpected results. This study was undertaken to establish a model for preconditioning of MSCs toward chondrogenesis as a more effective clinical tool for cartilage regeneration. Methods A coculture preconditioning system was used to improve the chondrogenic potential of human MSCs and to study the detailed stages of chondrogenesis of MSCs, using a human MSC line, Kp-hMSC, in commitment cocultures with a human chondrocyte line, hPi (labeled with green fluorescent protein [GFP]). In addition, committed MSCs were seeded into a collagen scaffold and analyzed for their neocartilage-forming ability. Results Coculture of hPi-GFP chondrocytes with Kp-hMSCs induced chondrogenesis, as indicated by the increased expression of chondrogenic genes and accumulation of chondrogenic matrix, but with no effect on osteogenic markers. The chondrogenic process of committed MSCs was initiated with highly activated chondrogenic adhesion molecules and stimulated cartilage developmental growth factors, including members of the transforming growth factor , superfamily and their downstream regulators, the Smads, as well as endothelial growth factor, fibroblast growth factor, insulin-like growth factor, and vascular endothelial growth factor. Furthermore, committed Kp-hMSCs acquired neocartilage-forming potential within the collagen scaffold. Conclusion These findings help define the molecular markers of chondrogenesis and more accurately delineate the stages of chondrogenesis during chondrocytic differentiation of human MSCs. The results indicate that human MSCs committed to the chondroprogenitor stage of chondrocytic differentiation undergo detailed chondrogenic changes. This model of in vitro chondrogenesis of human MSCs represents an advance in cell-based transplantation for future clinical use. [source] Prostaglandin E2 and its cognate EP receptors control human adult articular cartilage homeostasis and are linked to the pathophysiology of osteoarthritisARTHRITIS & RHEUMATISM, Issue 2 2009Xin Li Objective To elucidate the pathophysiologic links between prostaglandin E2 (PGE2) and osteoarthritis (OA) by characterizing the catabolic effects of PGE2 and its unique receptors in human adult articular chondrocytes. Methods Human adult articular chondrocytes were cultured in monolayer or alginate beads with and without PGE2 and/or agonists of EP receptors, antagonists of EP receptors, and cytokines. Cell survival, proliferation, and total proteoglycan synthesis and accumulation were measured in alginate beads. Chondrocyte-related gene expression and phosphatidylinositol 3-kinase/Akt signaling were assessed by real-time reverse transcription,polymerase chain reaction and Western blotting, respectively, using a monolayer cell culture model. Results Stimulation of human articular chondrocytes with PGE2 through the EP2 receptor suppressed proteoglycan accumulation and synthesis, suppressed aggrecan gene expression, did not appreciably affect expression of matrix-degrading enzymes, and decreased the type II collagen:type I collagen ratio. EP2 and EP4 receptors were expressed at higher levels in knee cartilage than in ankle cartilage and in a grade-dependent manner. PGE2 titration combined with interleukin-1 (IL-1) synergistically accelerated expression of pain-associated molecules such as inducible nitric oxide synthase and IL-6. Finally, stimulation with exogenous PGE2 or an EP2 receptor,specific agonist inhibited activation of Akt that was induced by insulin-like growth factor 1. Conclusion PGE2 exerts an antianabolic effect on human adult articular cartilage in vitro, and EP2 and EP4 receptor antagonists may represent effective therapeutic agents for the treatment of OA. [source] Hsp90 mediates insulin-like growth factor 1 and interleukin-1, signaling in an age-dependent manner in equine articular chondrocytesARTHRITIS & RHEUMATISM, Issue 7 2007Amber K. Boehm Objective Many metabolic processes in chondrocytes thought to contribute to age-related changes in the extracellular matrix are influenced by known roles of Hsp90. Age-related decreases in the level of Hsp90 have been documented in numerous cell types and could contribute to cartilage degeneration. The aim of this study was to investigate the roles of age and Hsp90 in insulin-like growth factor 1 (IGF-1) and interleukin-1, (IL-1,) signaling in chondrocytes. Methods Levels of Hsp90 messenger RNA (mRNA) and protein, with respect to age, were determined by quantitative real-time polymerase chain reaction (PCR) and Western blot analysis, respectively. The Hsp90 inhibitor geldanamycin (50 nM, 100 nM, or 500 nM) was used to assess age-related responses to Hsp90 with concurrent IGF-1 or IL-1, stimulation of chondrocytes. Quantitative real-time PCR was used to measure COL2A1 and matrix metalloproteinase 13 (MMP13) gene expression; Western blot analysis was performed to determine the phosphorylation status of p42/44 and Akt/protein kinase B. Results The effects of Hsp90 inhibition with geldanamycin were concentration dependent. Inhibition of Hsp90 with 100 nM or 500 nM geldanamycin blocked IGF-1,induced cell proliferation, Akt and p42/44 activation, and COL2A1 expression. Basal and IL-1,,induced up-regulation of MMP13 mRNA was blocked by all concentrations of geldanamycin tested. Gain-of-function assays with Hsp90 resulted in increased expression of MMP13 mRNA. Conclusion These results suggest that Hsp90 is involved in opposing signaling pathways of cartilage homeostasis, and that catabolic responses are more sensitive to Hsp90 inhibition than are anabolic responses. Further studies are needed to determine the role of Hsp90 inhibition in osteoarthritis in order to assess its potential as a therapeutic target. [source] | ||||||||||