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Human Osteoarthritis (human + osteoarthritis)
Selected AbstractsOverexpression of Smurf2 Stimulates Endochondral Ossification Through Upregulation of ,-Catenin,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2008Qiuqian Wu MD Abstract Ectopic expression of Smurf2 in chondrocytes and perichondrial cells accelerated endochondral ossification by stimulating chondrocyte maturation and osteoblast development through upregulation of ,-catenin in Col2a1-Smurf2 embryos. The mechanism underlying Smurf2-mediated morphological changes during embryonic development may provide new mechanistic insights and potential targets for prevention and treatment of human osteoarthritis. Introduction: Our recent finding that adult Col2a1-Smurf2 mice have an osteoarthritis-like phenotype in knee joints prompted us to examine the role of Smurf2 in the regulation of chondrocyte maturation and osteoblast differentiation during embryonic endochondral ossification. Materials and Methods: We analyzed gene expression and morphological changes in developing limbs by immunofluorescence, immunohistochemistry, Western blot, skeletal preparation, and histology. A series of markers for chondrocyte maturation and osteoblast differentiation in developing limbs were examined by in situ hybridization. Results: Ectopic overexpression of Smurf2 driven by the Col2a1 promoter was detected in chondrocytes and in the perichondrium/periosteum of 16.5 dpc transgenic limbs. Ectopic Smurf2 expression in cells of the chondrogenic lineage inhibited chondrocyte differentiation and stimulated maturation; ectopic Smurf2 in cells of the osteoblastic lineage stimulated osteoblast differentiation. Mechanistically, this could be caused by a dramatic increase in the expression of ,-catenin protein levels in the chondrocytes and perichondrial/periosteal cells of the Col2a1-Smurf2 limbs. Conclusions: Ectopic expression of Smurf2 driven by the Col2a1 promoter accelerated the process of endochondral ossification including chondrocyte maturation and osteoblast differentiation through upregulation of ,-catenin, suggesting a possible mechanism for development of osteoarthritis seen in these mice. [source] MicroRNA-27b regulates the expression of matrix metalloproteinase 13 in human osteoarthritis chondrocytesARTHRITIS & RHEUMATISM, Issue 5 2010Nahid Akhtar Objective Aberrant posttranscriptional regulation of matrix metalloproteinases (MMPs) by microRNA has emerged as an important factor in human diseases. The aim of this study was to determine whether the expression of MMP-13 in human osteoarthritis (OA) chondrocytes is regulated by microRNA. Methods Chondrocytes were stimulated with interleukin-1, (IL-1,) in vitro. Total RNA was prepared using TRIzol reagent. Polymerase chain reaction (PCR),based arrays were used to determine the expression profile of 352 human microRNA. Gene expression was quantified using TaqMan assays, and microRNA targets were identified using bioinformatics. Transfection with reporter construct and microRNA mimic was used to verify suppression of target messenger RNA (mRNA). Gene expression of argonaute and Dicer was determined by reverse transcription,PCR, and expression of protein was determined by immunoblotting. The role of activated MAP kinases (MAPKs) and NF-,B was evaluated using specific inhibitors. Results In IL-1,,stimulated OA chondrocytes, 42 microRNA were down-regulated, 2 microRNA were up-regulated, and the expression of 308 microRNA remained unchanged. In silico analysis identified a sequence in the 3,-untranslated region (3,-UTR) of MMP-13 mRNA complementary to the seed sequence of microRNA-27b (miR-27b). Increased expression of MMP-13 correlated with down-regulation of miR-27b. Overexpression of miR-27b suppressed the activity of a reporter construct containing the 3,-UTR of human MMP-13 mRNA and inhibited the IL-1,,induced expression of MMP-13 protein in chondrocytes. NF-,B and MAPK activation down-regulated the expression of miR-27b. Conclusion Our data demonstrated the expression of miR-27b in both normal and OA chondrocytes. Furthermore, IL-1,,induced activation of signal transduction pathways associated with the expression of MMP-13 down-regulated the expression of miR-27b. Thus, miR-27b may play a role in regulating the expression of MMP-13 in human chondrocytes. [source] Calcification of articular cartilage in human osteoarthritisARTHRITIS & RHEUMATISM, Issue 9 2009M. Fuerst Objective Hypertrophic chondrocyte differentiation is a key step in endochondral ossification that produces basic calcium phosphates (BCPs). Although chondrocyte hypertrophy has been associated with osteoarthritis (OA), chondrocalcinosis has been considered an irregular event and linked mainly to calcium pyrophosphate dihydrate (CPPD) deposition. The aim of this study was to determine the prevalence and composition of calcium crystals in human OA and analyze their relationship to disease severity and markers of chondrocyte hypertrophy. Methods One hundred twenty patients with end-stage OA undergoing total knee replacement were prospectively evaluated. Cartilage calcification was studied by conventional x-ray radiography, digital-contact radiography (DCR), field-emission scanning electron microscopy (FE-SEM), and synovial fluid analysis. Cartilage calcification findings were correlated with scores of knee function as well as histologic changes and chondrocyte hypertrophy as analyzed in vitro. Results DCR revealed mineralization in all cartilage specimens. Its extent correlated significantly with the Hospital for Special Surgery knee score but not with age. FE-SEM analysis showed that BCPs, rather than CPPD, were the prominent minerals. On histologic analysis, it was observed that mineralization correlated with the expression of type X collagen, a marker of chondrocyte hypertrophy. Moreover, there was a strong correlation between the extent of mineralization in vivo and the ability of chondrocytes to produce BCPs in vitro. The induction of hypertrophy in healthy human chondrocytes resulted in a prominent mineralization of the extracellular matrix. Conclusion These results indicate that mineralization of articular cartilage by BCP is an indissociable process of OA and does not characterize a specific subset of the disease, which has important consequences in the development of therapeutic strategies for patients with OA. [source] Involvement of the Wnt signaling pathway in experimental and human osteoarthritis: Prominent role of Wnt-induced signaling protein 1ARTHRITIS & RHEUMATISM, Issue 2 2009Arjen B. Blom Objective Wnt signaling pathway proteins are involved in embryonic development of cartilage and bone, and, interestingly, developmental processes appear to be recapitulated in osteoarthritic (OA) cartilage. The present study was undertaken to characterize the expression pattern of Wnt and Fz genes during experimental OA and to determine the function of selected genes in experimental and human OA. Methods Longitudinal expression analysis was performed in 2 models of OA. Levels of messenger RNA for genes from the Wnt/,-catenin pathway were determined in synovium and cartilage, and the results were validated using immunohistochemistry. Effects of selected genes were assessed in vitro using recombinant protein, and in vivo by adenoviral overexpression. Results Wnt-induced signaling protein 1 (WISP-1) expression was strongly increased in the synovium and cartilage of mice with experimental OA. Wnt-16 and Wnt-2B were also markedly up-regulated during the course of disease. Interestingly, increased WISP-1 expression was also found in human OA cartilage and synovium. Stimulation of macrophages and chondrocytes with recombinant WISP-1 resulted in interleukin-1,independent induction of several matrix metalloproteinases (MMPs) and aggrecanase. Adenoviral overexpression of WISP-1 in murine knee joints induced MMP and aggrecanase expression and resulted in cartilage damage. Conclusion This study included a comprehensive characterization of Wnt and Frizzled gene expression in experimental and human OA articular joint tissue. The data demonstrate, for the first time, that WISP-1 expression is a feature of experimental and human OA and that WISP-1 regulates chondrocyte and macrophage MMP and aggrecanase expression and is capable of inducing articular cartilage damage in models of OA. [source] | ||||||||||