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Bone Matrix Proteins (bone + matrix_protein)
Selected AbstractsMammary Gland Secretory Concretions Contain Non-Collagenous Bone Matrix ProteinsANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2006M. Egerbacher Summary Secretory concretions in mammary gland alveoli are commonly of microscopical size. However, some concretions reach clinically palpable dimensions and may occlude teat canals and obstruct milk flow. We studied secretory concretions in sheep, goat and cow mammary glands, using routine histological staining methods, conventional histochemistry and electron microscopy. As concretions frequently mineralize, immunostaining for keratan sulphate and calcium-binding non-collagenous bone matrix proteins (bone sialoprotein, osteocalcin, osteonectin and osteopontin) was performed. Concretions consisted of organic matrix (condensed secretions) with calcium precipitates. Mineralized deposits mostly show concentric organization, bound haematoxylin, and were readily identified in H&E-stained sections. Mineral components of concretions reacted for calcium carbonate and phosphate, organic matrix was found to contain sialoglycan material. Immunohistochemistry revealed bone sialoprotein, osteonectin and keratan sulphate in cow and goat concretions. Osteocalcin was detected in sheep, cow and goat concretions, whilst osteopontin was not identified in any of the specimens studied. Our results indicate the presence of non-collagenous bone matrix proteins (except osteopontin) in mammary gland concretions. These glycoproteins are commonly thought to govern mineralization of organic matrix and are assumed also to promote mineral deposition in mammary gland secretory concretions. Besides caseins, these particular glycoproteins have to be considered as calcium-binding milk proteins. [source] Osteopontin: a key cytokine in cell-mediated and granulomatous inflammationINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 6 2000Anthony O'Regan Osteopontin (Opn) is a secreted adhesive, glycosylated phosphoprotein that contains the arginine-glycine-aspartic acid (RGD) cell-binding sequence that is found in many extracellular matrix (ECM) proteins (for a review of Opn see References Denhardt & Guo 1993; Patarca et al. 1993; Rittling & Denhardt 1999). Since its initial description in 1979 as a secreted protein associated with malignant transformation, Opn has been independently discovered by investigators from diverse scientific disciplines, and has been associated with a remarkable range of pathologic responses. Opn is an important bone matrix protein, where it is thought to mediate adhesion of osteoclasts to resorbing bone. However, studies from the past decade have identified an alternative role for Opn as a key cytokine regulating tissue repair and inflammation. Recent work by our laboratory and that of others has underlined the importance of Opn as a pivotal cytokine in the cellular immune response. Despite this Opn is not well known to the immunologist. In this review we will focus on studies that pertain to the role of Opn in cell-mediated and granulomatous inflammation. [source] The polymine spermine regulates osteogenic differentiation in adipose stem cells,JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 5a 2008G.S. Tjabringa Abstract For bone tissue engineering, it is important that mesenchymal stem cells (MSCs) differentiate into osteoblasts. To develop a method for differentiation of adipose tissue-derived mesenchymal stem cells (AT-MSCs) along the osteogenic lineage, we studied the effect of polyamines, which are organic cations implicated in bone growth and development, on differentiation of AT-MSCs. Treatment of goat-derived AT-MSCs with 1,25-dihydroxyvitamin-D3 (1,25(OH)2D3), which stimulates osteogenic differentiation, for 7 days induced gene expression of the polyamine-modulated transcription factor-1 (PMF-1) and spermidine/spermine N (1)-acetyltransferase (SSAT), which are both involved in polyamine metabolism, suggesting that polyamines are involved in osteogenic differentiation of AT-MSCs. Furthermore, treatment of AT-MSCs with the polyamine spermine-regulated gene expression of runx-2, a transcription factor involved in early stages of osteogenic differentiation, and that of osteopontin, a bone matrix protein expressed in later stages of osteogenic differentiation. Runx-2 gene expression was increased 4 and 14 days after a short 30 min. treatment with spermine, while osteopontin gene expression was only increased 4 days after spermine treatment. Finally, alkaline phosphatase activity, which is intimately involved in the formation of extracellular matrix of bone, was increased 4 weeks after the 30 min.-spermine treatment of AT-MSCs. In conclusion, this study shows for the first time that the polyamine spermine regulates differentiation of AT-MSCs along the osteogenic lineage, which can be used as a new method for differentiation of AT-MSCs along the osteogenic lineage. Therefore, polyamines may constitute a promising tool for bone tissue engineering approaches using AT-MSCs, such as a one-step surgical procedure for spinal interbody fusion. [source] Full-length bovine spp24 [spp24 (24-203)] inhibits BMP-2 induced bone formation,JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2008Chananit Sintuu Abstract Secreted phosphoprotein 24 kDa (spp24) is a bone matrix protein. It contains a TGF-, receptor II homology 1 (TRH1) domain. A cyclic, synthetic 19 amino acid peptide (bone morphogenetic protein binding peptide or BBP) based on the sequence of the TRH1 domain enhances BMP-2 induced osteogenesis. Many observations suggest that different size forms of this protein have very different effects (inhibiting or enhancing) on BMP-2 induced osteogenesis. Using the stable recombinant Met(His)6 -tagged secretory form of full-length (fl) bovine spp24 [Met(His)6 -spp24 (residues 24,203)] and transgenic (TG) mice expressing fl bovine spp24 (residues 1,203), we have demonstrated that spp24 inhibits BMP-2 induced bone formation. The effects of Met(His)6 -spp24 (24,203) were determined in the ectopic bone-forming bioassay in male mice. Implantation of 5 µg of BMP-2 stimulated bone formation, assessed densitometrically as bone area and mineral content. When Met(His)6 -spp24 (24,203) was implanted with BMP-2, it elicited a dose-dependent decrease in BMP-2-medicated ectopic bone formation. When added at a 50-fold excess (w/w), Met(His)6 -spp24 (24,203) completely ablated the effects of BMP-2, while addition of a 10-fold excess had no effect. Constitutive expression of fl bovine spp24 (1,203) under the control of the osteocalcin promoter in TG female mice reduced femoral and vertebral bone mineral density at 3 months of age and reduced femoral BMD at 8 months of age, but had no effects in male mice, which can exhibit less osteocalcin-promoter driven gene transcription than females. Histomorphometric analysis demonstrated that bone volume and trabecular thickness were lower in TG female mice at 3 months of age than in sex- and age-matched wild type (WT) controls. Thus, fl spp24 and its secretory isoform (Met(His)6 -spp24 [24,203]), which contain a BMP-binding or TRH1 motif, inhibit ectopic bone formation in male mice and adversely affects BMD and histological parameters related to bone mass and formation in female mice expressing the human transgene. Under these conditions, fl spp24 acts as a BMP antagonist in vivo. © 2008 Orthopaedic Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:753,758, 2008 [source] Smad3 Promotes Alkaline Phosphatase Activity and Mineralization of Osteoblastic MC3T3-E1 Cells,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2002Hideaki Sowa Abstract Transforming growth factor (TGF) , is abundantly stored in bone matrix and appears to regulate bone metabolism. Although the Smad family proteins are critical components of the TGF-, signaling pathways, the roles of Smad3 in the expression of osteoblastic phenotypes remain poorly understood. Therefore, this study was performed to clarify the roles of Smad3 in the regulation of proliferation, expression of bone matrix proteins, and mineralization in osteoblasts by using mouse osteoblastic cell line MC3T3-E1 cells stably transfected with Smad3. Smad3 significantly inhibited [3H]thymidine incorporation and fluorescent intensity of the MTT-dye assay, compared with empty vector. Moreover, Smad3 increased the levels of type I procollagen, osteopontin (OPN), and matrix Gla protein (MGP) mRNA in Northern blotting. These effects of Smad3 mimicked the effects of TGF-, on the same cells. On the other hand, Smad3 greatly enhanced ALP activity and mineralization of MC3T3-E1 cells compared with empty vector, although TGF-, inhibited ALP activity and mineralization of wild-type MC3T3-E1 cells. A type I collagen synthesis inhibitor L -azetidine-2-carboxylic acid, as well as osteocalcin (OCN), significantly antagonized Smad3-stimulated ALP activity and mineralization of MC3T3-E1 cells. In conclusion, this study showed that in mouse osteoblastic cells, Smad3 inhibited proliferation, but it also enhanced ALP activity, mineralization, and the levels of bone matrix proteins such as type I collagen (COLI), OPN, and MGP. We propose that Smad3 plays an important role in osteoblastic bone formation and might help to elucidate the transcriptional mechanism of bone formation and possibly lead to the development of bone-forming drugs. [source] The Dose-Response Effects of Ethanol on the Human Fetal Osteoblastic Cell LineJOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2001A. Maran Abstract Alcohol is a risk factor for the development of osteoporosis, especially in men. Chronic alcohol abuse decreases bone mass, which contributes to the increased incidence of fractures. To better understand the mechanism of action of ethanol on bone metabolism, we have studied the dose-response effects of ethanol on conditionally immortalized human fetal osteoblasts (hFOB) in culture. Ethanol treatment had no significant effects on osteoblast number after 1 day or 7 days. Ethanol treatment did not reduce type I collagen protein levels at either time point at any dose but slightly reduced alkaline phosphatase activity after 7 days. The messenger RNA (mRNA) levels for alkaline phosphatase, type I collagen, and osteonectin were unaltered by 24 h of ethanol treatment but a high dose (200 mM) reduced mRNA levels for the two bone matrix proteins after 7 days. Ethanol treatment led to dose-dependent increases in transforming growth factor ,1 (TGF-,1) mRNA levels and decreases in TGF-,2 mRNA levels. The concentration of ethanol in the medium decreased with time because of evaporation but there was little degradation caused by metabolism. These results, which show that cultured osteoblasts are less sensitive than osteoblasts in vivo, suggest that the pronounced inhibitory effects of ethanol on bone formation are not caused by direct cell toxicity. [source] Bone Mineralization and Osteoblast Differentiation Are Negatively Modulated by Integrin ,v,3JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2001Su-Li Cheng Abstract Numerous bone matrix proteins can interact with ,v-containing integrins including ,v,3. To elucidate the net effects of the interaction between these proteins and ,v,3 on osteoblast function, we developed a murine osteoblastic cell line that overexpressed human ,v,3. Human ,v,3-integrin was expressed on cell membrane, in which its presence did not alter the surface level of endogenous mouse ,v,3. The expressed human ,v,3 was functional because cell adhesion to osteopontin was increased and this increment was abolished by antibody against human ,v,3. The proliferation rate of cells overexpressing ,v,3 (,v,3-cells) was increased whereas matrix mineralization was decreased. To elucidate the mechanisms leading to inhibition of matrix mineralization, the expression of proteins important for mineralization was analyzed. Alkaline phosphatase activity and the expression of osteocalcin, type I collagen, and bone sialoprotein (BSP) were decreased whereas osteopontin was stimulated in ,v,3-cells. The regulation of osteopontin, osteocalcin, and BSP expression was mediated via transcriptional mechanism because their promoter activities were altered. Examination of molecules involved in integrin signaling indicated that activator protein-1 (AP-1) and extracellular signal-regulated kinase (Erk) activities were enhanced whereas c-jun N -terminal kinase (JNK) activity was decreased in ,v,3-cells. The activity of p38 and the levels of focal adhesion kinase (FAK) and vinculin were not altered. Moreover, the adhesions of ,v,3-cells to type I collagen and fibronectin were inhibited, which was attributed to decreased ,1-integrin levels on cell surface. In conclusion, overexpressing ,v,3-integrin in osteoblasts stimulated cell proliferation but retarded differentiation, which were derived via altered integrin-matrix interactions, signal transduction, and matrix protein expression. [source] Expression of osteopontin messenger RNA by macrophages in ovarian serous papillary cystadenocarcinoma: A possible association with calcification of psammoma bodiesPATHOLOGY INTERNATIONAL, Issue 7 2000Masahiko Maki Calcified psammoma bodies often appear in human ovarian serous papillary cystadenocarcinoma. Osteocalcin (OC), osteonectin (ON) and osteopontin (OPN) are three members of non-collagenous bone-related proteins known to be related with mineralization of bone. To clarify possible involvement of these bone matrix proteins in the calcification of the psammoma bodies, the expression of OC, ON and OPN was analyzed by immunohistochemical and in situ hybridization studies using 15 surgical specimens. OPN protein was detected in the calcified area of the psammoma bodies which was positively stained by von Kóssa's staining, while OC and ON proteins were not. OPN protein was not detected in any cells in tissues, but OPN messenger ribonucleic acid (mRNA) was detected in CD68-positive macrophages, indicating that OPN was produced and promptly secreted by macrophages. These results suggest that OPN produced and promptly secreted by macrophages and subsequently translocated to psammoma bodies may be causally related with the calcium phosphate deposition in the psammoma bodies of the ovarian serous papillary cystadenocarcinomas. [source] Mammary Gland Secretory Concretions Contain Non-Collagenous Bone Matrix ProteinsANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2006M. Egerbacher Summary Secretory concretions in mammary gland alveoli are commonly of microscopical size. However, some concretions reach clinically palpable dimensions and may occlude teat canals and obstruct milk flow. We studied secretory concretions in sheep, goat and cow mammary glands, using routine histological staining methods, conventional histochemistry and electron microscopy. As concretions frequently mineralize, immunostaining for keratan sulphate and calcium-binding non-collagenous bone matrix proteins (bone sialoprotein, osteocalcin, osteonectin and osteopontin) was performed. Concretions consisted of organic matrix (condensed secretions) with calcium precipitates. Mineralized deposits mostly show concentric organization, bound haematoxylin, and were readily identified in H&E-stained sections. Mineral components of concretions reacted for calcium carbonate and phosphate, organic matrix was found to contain sialoglycan material. Immunohistochemistry revealed bone sialoprotein, osteonectin and keratan sulphate in cow and goat concretions. Osteocalcin was detected in sheep, cow and goat concretions, whilst osteopontin was not identified in any of the specimens studied. Our results indicate the presence of non-collagenous bone matrix proteins (except osteopontin) in mammary gland concretions. These glycoproteins are commonly thought to govern mineralization of organic matrix and are assumed also to promote mineral deposition in mammary gland secretory concretions. Besides caseins, these particular glycoproteins have to be considered as calcium-binding milk proteins. [source] | |||||||||||||