The Spatial Pattern of Integrins during Development of Mouse Articular Cartilagea (original) (raw)
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β1-Integrins in the cartilage matrix
Cell and Tissue Research, 1999
Integrins are cell-surface receptors that mediate cell attachment to extracellular matrix components. The pericellular matrix in cartilage not only is a mechanical framework, but is also important for chondrocyte differentiation and stabilization of the phenotype. The interaction between chondrocytes and pericellular matrix is mediated, in part, by integrin receptors. We have previously demonstrated the presence of β1-integrins in the cartilage matrix of organoid culture of limb buds from 12-day-old mouse embryos by immunohistological methods. In order to corroborate these findings, we have further investigated the distribution of integrins in the cartilage matrix by immunoelectron microscopy and by immunoprecipitation methods. Cartilage tissue of limb buds of 17-day-old mouse embryos was treated with collagenase and the cell-free and cellular protein-free supernatant was removed and used for immunoprecipitation experiments. Immunoprecipitation with antibodies against β1-, α1-, α3-, and α5β1-integrins and collagen type II, followed by immunoblotting with the same antibodies, demonstrated the presence of these integrins and collagen type II in the supernatant. The integrins found in the cartilage matrix could have been either secreted or shed by the cells. The question as to whether they have a function in the cartilage matrix, such as interlinking, in the matrix organization or in the stabilization of matrix components remains to be elucidated.
Annals of the Rheumatic Diseases, 1998
Objective-The objective of this study was to detail the topographical and zonal distribution of and subunits of the integrin superfamily in normal and osteoarthritic cartilage. Methods-Immunohistochemistry utilising antibodies towards and subunits was performed on cryostat sections of human articular cartilage from macroscopically normal (n = 6) and osteoarthritic (n = 6) femoral heads. Samples of articular cartilage were obtained from 12 topographically distinct sites from each femoral head. Each section was divided into zones (superficial, middle, deep) and staining scores were recorded. Results-Normal cartilage stained for integrin subunits 1,
Molecular & Cellular Proteomics, 2012
Skeletal growth by endochondral ossification involves tightly coordinated chondrocyte differentiation that creates reserve, proliferating, prehypertrophic, and hypertrophic cartilage zones in the growth plate. Many human skeletal disorders result from mutations in cartilage extracellular matrix (ECM) components that compromise both ECM architecture and chondrocyte function. Understanding normal cartilage development, composition, and structure is therefore vital to unravel these disease mechanisms. To study this intricate process in vivo by proteomics, we analyzed mouse femoral head cartilage at developmental stages enriched in either immature chondrocytes or maturing/hypertrophic chondrocytes (postnatal days 3 and 21, respectively). Using LTQ-Orbitrap tandem mass spectrometry, we identified 703 cartilage proteins. Differentially abundant proteins (q < 0.01) included prototypic markers for both early and late chondrocyte differentiation (epiphycan and collagen X, respectively) and novel ECM and cell adhesion proteins with no previously described roles in cartilage development (tenascin X, vitrin, Urb, emilin-1, and the sushi repeat-containing proteins SRPX and SRPX2). Meta-analysis of cartilage development in vivo and an in vitro chondrocyte culture model (. (2010) Comprehensive profiling of cartilage extracellular matrix formation and maturation using sequential extraction and label-free quantitative proteomics. Mol. Cell. Proteomics 9, 1296 -1313) identified components involved in both systems, such as Urb, and components with specific roles in vivo, including vitrin and CILP-2 (cartilage intermediate layer protein-2). Immunolocalization of Urb, vitrin, and CILP-2 indicated specific roles at different maturation stages. In addition to ECMrelated changes, we provide the first biochemical evidence of changing endoplasmic reticulum function during cartilage development. Although the multifunctional chaperone BiP was not differentially expressed, enzymes and chaperones required specifically for collagen biosynthesis, such as the prolyl 3-hydroxylase 1, cartilage-associated protein, and peptidyl prolyl cis-trans isomerase B complex, were down-regulated during maturation. Conversely, the lumenal proteins calumenin, reticulocalbin-1, and reticulocalbin-2 were significantly increased, signifying a shift toward calcium binding functions. This first proteomic analysis of cartilage development in vivo reveals the breadth of protein expression changes during chondrocyte maturation and ECM remodeling in the mouse femoral head. Molecular & Cellular Proteomics 11: 10.1074/mcp.M111.014159, 1-18, 2012.
Changes in integrin expression during chondrogenesis in vitro: an immunomorphological study
Journal of Histochemistry & Cytochemistry, 1995
Integrins are receptors composed of ligand-specific alpha-chains and cell type-specific beta-chains which are involved in cell-cell and cell-matrix interactions. The distribution of alpha 1- and alpha 3-integrins as well as collagen Types I and II, was investigated by immunofluorescence and immunoelectron microscopy during chondrogenesis in organ culture after various culture periods. Mesenchymal cells from limb buds of Day 12 mouse embryos were grown at high density. Within the first 2 days of the culture period, only alpha 1-integrin could be detected. Formation of cartilage-specific matrix on Day 3 was accompanied by the occurrence of alpha 3-integrin. On Day 7, alpha 3 was present only in cartilage nodules, whereas alpha 1 was strongly expressed in the perichondrium and was more or less homogeneously distributed in the surrounding mesenchyme. On Day 14, alpha 1-integrin was again detectable in cartilage. We suggest that the change in collagen formation from Type I to Type II dur...
Response to the Removal of Extracellular Cartilage Matrix
Fibronectin, the major cell surface glycoprotein of fibroblasts, is absent from differentiated cartilage matrix and chondrocytes in situ. However, dissociation of embryonic chick sternal cartilage with collagenase and trypsin, followed by inoculation in vitro reinitiates fibronectin synthesis by chondrocytes. Immunoflu- orescence microscopy with antibodies prepared against plasma fibronectin (cold insoluble globulin (CIG)) reveals fibronectin associated with the chondrocyte surface. Synthesis and secretion of fibronectin into the medium are shown by anabolic labeling with (3~S)methionine or (3H)glycine, and identification of the secreted proteins by immunoprecipitation and sodium dodecyl sulfate (SDS)-disc gel electrophoresis. When chondrocytes are plated onto tissue culture dishes, the pattern of surface- associated fibronectin changes from a patchy into a strandlike appearance. Where epithelioid clones of polygonal chondrocytes develop, only short strands of fibronectin appear pre...
Osteoarthritis and Cartilage, 2003
The publisher regrets that in the above article Figs. 1, 2, 3, 5 and 8 were not published in their correct format. These figures and the figure legends are reprinted correctly below. Fig. 1. In situ hybridization demonstrates widespread COMP expression in the developing cartilage of Day 16.5 embryonic mouse. Sagittal sections of embryonic mice (day 16.5 post coitus dpc) were processed for in situ hybridization for COMP mRNA, as described in the Methods section. The sections were observed by darkfield optics to visualize the in situ hybridization signal (left column), or by bright field optics to view the histology by Mallory's Trichrome stain (right column). Three regions of the embryo are shown: (A,B) footpad, (C,D) tail vertebrae and (E,F) trunk. Positive hybridization signals (white grains indicated by the arrows) were localized to sites of active chondrogenesis in the developing skeletal elements of the digits of the paw (A), the tail (C) and the vertebral column and sternum (E). The data show that COMP expression is extensive in the regions undergoing chondrogenesis. The black arrows (B, D and F) indicate the corresponding regions in the control, stained sections. Controls using radiolabeled sense probe showed no detectable hybridization signal (data not shown).