Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nature and tissue distribution of non-collagenous bone proteins synthesized by adult rat bone marrow cells, induced to differentiate in the presence of dexamethasone (DEX) and beta-glycerophosphate (beta-GP), was studied in vitro to determine the potential role of these proteins in bone formation. Northern hybridization analysis revealed a strong induction of bone sialoprotein (BSP) and osteocalcin in DEX-treated cultures, whereas the constitutive expression of secreted phosphoprotein I (SPP-1), type I collagen, SPARC, and alkaline phosphatase was stimulated 6-, 5-, 3-, and 2.5-told, respectively. Metabolic labeling of proteins showed that the sialoproteins (SPP-1 and BSP) were mostly secreted into the culture medium in the non-mineralizing (-beta-GP) cultures, but were the predominant non-collagenous proteins associated with the hydroxyapatite of the bone nodules in mineralizing cultures (+ beta-GP). Extraction of the tissue matrix with 4 M GuHCl and digestion of the demineralized tissue matrix with bacterial collagenase revealed that some BSP was also associated non-covalently and covalently with the collagenous matrix. SPP-1 was present in two distinct, 44 kDa and 55 kDa, forms in the conditioned medium of all cultures and was preferentially associated with the hydroxyapatite in the mineralizing cultures. In comparison, SPARC was abundant in culture media but could not be detected in de-mineralizing extracts of the mineralized tissue. Radiolabeling with [35SO4] demonstrated that both SPP-1 and BSP synthesized by bone cells are sulfated, and that a 35 kDa protein and some proteoglycan were covalently associated with the collagenous matrix in +DEX cultures. Labeling with [32PO4] was essentially confined to the sialoproteins; the 44 kDa SPP-1 incorporating significantly more [32PO4] than the 55 kDa SPP-1 and the BSP. These studies demonstrate that BSP and osteocalcin are only expressed in differentiated osteoblasts and that most of the major non-collagenous bone proteins associate with the bone mineral. However, some novel proteins together with some of the BSP are associated with the collagenous matrix where they can influence hydroxyapatite formation.
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PMID:Expression of bone matrix proteins associated with mineralized tissue formation by adult rat bone marrow cells in vitro: inductive effects of dexamethasone on the osteoblastic phenotype. 203 18

To determine the effects of transforming growth factor-beta (TGF-beta) on the different cell types that exist in bone, cell populations (I-IV), progressively enriched in osteoblastic cells relative to fibroblastic cells, were prepared from fetal rat calvaria using timed collagenase digestions. TGF-beta did not induce anchorage-independent growth of these cells, nor was anchorage-dependent growth stimulated in most populations studied, despite a two- to threefold increase in the synthesis of cellular proteins. In all populations the synthesis of secreted proteins increased 2-3.5-fold. In particular, collagen, fibronectin, and plasminogen activator inhibitor synthesis was stimulated. However, different degrees of stimulation of individual proteins were observed both within and between cell populations. A marked preferential stimulation of plasminogen activator inhibitor was observed in each population, together with a slight preferential stimulation of collagen; the effect on collagen expression being directed primarily at type I collagen. In contrast, the synthesis of SPARC (secreted protein acidic rich in cysteine/osteonectin was stimulated approximately two-fold by TGF-beta, but only in fibroblastic populations. Collectively, these results demonstrate that TGF-beta stimulates matrix production by bone cells and, through differential effects on individual matrix components, may also influence the nature of the matrix formed by different bone cell populations. In the presence of TGF-beta, osteoblastic cells lost their polygonal morphology and alkaline phosphatase activity was decreased, reflecting a suppression of osteoblastic features. The differential effects of TGF-beta on bone cell populations are likely to be important in bone remodeling and fracture repair.
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PMID:Differential effects of transforming growth factor-beta on the synthesis of extracellular matrix proteins by normal fetal rat calvarial bone cell populations. 316 38

Basic fibroblast growth factor (bFGF) may be involved in the development and repair of dentine and pulp because bFGF, its related peptides, and FGF receptors are expressed in dental mesenchymal cells. In this study, we examined the effects of bFGF on DNA synthesis, osteonectin/SPARC levels, alkaline phosphatase (ALPase) activity, their mRNA levels, and calcium levels in cultures of human pulp cells. Pulp cells were isolated from three healthy upper wisdom teeth of three patients and maintained separately. These cells produced SPARC, ALPase, and calcified nodules and there was a close correlation between the SPARC-synthetic activity of the cell lines and their levels of ALPase and calcification. The levels of SPARC, ALPase and calcium deposits in the three pulp cell cultures were 10-250 times those of human foreskin fibroblasts. Western blots showed that the pulp cells produced 38-kDa SPARC. Northern blots showed that the pulp cells expressed flg (FGF receptor type 1) transcripts throughout all culture stages, irrespective of the presence or absence of bFGF. The addition of bFGF to the pulp cultures suppressed the increases in ALPase activity, SPARC synthesis, and their mRNA levels, although it increased the incorporation of [3H]thymidine into DNA > 10-fold. The effects of bFGF on ALPase activity and SPARC synthesis were reversible. Furthermore, bFGF abolished the calcification of the extracellular matrix; the calcium content of bFGF-free cultures. These findings suggest that bFGF is a potent mitogen for human pulp cells and that it inhibits the expression of the odontoblast phenotype by the cells at least partly at pretranslational levels.
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PMID:Effects of basic fibroblast growth factor on proliferation, the expression of osteonectin (SPARC) and alkaline phosphatase, and calcification in cultures of human pulp cells. 764 76

Rat bone marrow stromal cells comprise a heterogeneous mixture of cell lineages including osteoblastic cells. When grown in the presence of ascorbic acid, beta-glycerophosphate and 10(-8) M dexamethasone, osteoprogenitor cells within the population divide and differentiate to form bone nodules (Maniatopoulos et al., 1988, Cell Tissue Res., 254:317-330; Aubin et al., 1990, J. Bone Miner. Res., 5:S81) providing a useful model to investigate temporal and spatial changes in expression of osteoblastic markers. Immunocytochemistry was combined with Northern blotting, enzymatic assay, and radioimmunoassay to analyze the expression of bone-related proteins during the growth and differentiation sequence. By mRNA levels, protein production and/or enzymatic activity, expression of osteocalcin, bone sialoprotein, and alkaline phosphatase increased concomitantly with the development of bone nodules, while osteopontin mRNA levels decreased and those of SPARC/osteonectin did not change significantly. In older cultures with mineralizing nodules, mRNA levels for alkaline phosphatase and bone sialoprotein, but not osteocalcin, declined. Immunolabeling revealed that cells in early cultures stained poorly for SPARC/osteonectin and strongly for thrombospondin. Later, SPARC/osteonectin staining increased in most cells, while thrombospondin staining could be seen in both matrix and in cells, but with marked intercellular variability in intensity. At all time points studied, osteoblasts within bone nodules stained homogeneously for thrombospondin and alkaline phosphatase, and with marked heterogeneity of intensity amongst cells for SPARC/osteonectin and osteocalcin. Labelling with RCC455.4, a monoclonal antibody raised against rat calvaria cells which intensely labels osteoblasts and osteocytes (Turksen et al., 1992, J. Histochem. Cytochem., 40:1339-1352), co-localized with osteocalcin. Alkaline phosphatase activity and the amount of osteocalcin determined by both radioimmunoassay and immunolabelling decreased in very late cultures, a time corresponding to appearance of fully mineralized nodules. These studies indicate that the bone marrow stromal cell system is a useful model to study the temporal and spatial expression of bone-related proteins during osteogenesis and formation, mineralization, and maturation of bone nodules. Further, immunolabelling at the individual cell and single bone nodule level allowed discrimination of marked variability of expression of osteoblast markers during the differentiation sequence.
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PMID:Cellular expression of bone-related proteins during in vitro osteogenesis in rat bone marrow stromal cell cultures. 812 78

To characterize the bone-like tissue produced by rat bone marrow cells (RBMC) from young adult femurs, the synthesis of bone proteins and the expression of their mRNA were studied in vitro. RBMC plated at a density of 5 x 10(3) cells/cm2 and grown in the presence of 10(-8) M dexamethasone (Dex) and 10 mM beta-glycerophosphate (beta-GP) produced mineralized bone nodules, which were first evident at day 3 and increased markedly to day 13. However, in the absence of dexamethasone, few mineralized nodules were observed. The formation of mineralized nodules was reflected by the uptake of 45Ca, which also increased markedly to day 13. Analysis of bone protein expression by Northern and slot-blot hybridizations revealed an increase in mRNA levels of collagen type I (Col I), osteonectin/SPARC (ON), alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP), and osteocalcin (OC) during the formation of mineralized nodules. Whereas the Col I, ON, ALP, and OPN mRNAs were expressed before the formation of mineralized nodules was evident and were also expressed at various levels in the absence of Dex, the expression of BSP and OC mRNA was induced in the bone-forming cultures. The expression of BSP mRNA was correlated temporally with bone tissue formation, reaching maximal levels on day 16. In contrast, OC mRNA was expressed later and, following induction, increased over the 28 day culture period. Production of matrix proteins during the rapid formation of the bone tissue appeared to reflect the levels of the respective mRNAs. However, whereas some of the collagen and almost all of the SPARC were secreted into the culture medium, virtually all of the OPN and most of the BSP were extracted from the mineralized tissue matrix with EDTA. Some OPN and BSP were present in the medium, especially early in the culture, and a significant amount of BSP was also found associated with the collagenous tissue matrix. These studies point to the importance of Col I, ALP, OPN, and BSP, but not ON or OC, in the initial formation of bone tissue.
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PMID:Temporal changes in matrix protein synthesis and mRNA expression during mineralized tissue formation by adult rat bone marrow cells in culture. 814 Sep 36

Previous studies in our laboratory demonstrated messenger RNA for bone morphogenetic protein-2a in human calcified plaque, suggesting that arterial calcification is a regulated process, similar to osteogenesis. To further test this hypothesis, we have isolated and cloned a subpopulation of cells from bovine aortic media that show osteoblastic potential. These novel cells are primarily distinguished from smooth muscle cells by expression of a surface marker preliminarily identified as a modified form of the ganglioside sialyl-lactosylceramide (GM3). Osteoblastic potential was indicated by high levels of alkaline phosphatase and collagen I, expression of osteopontin and osteonectin (SPARC), and production of bone-specific osteocalcin and hydroxyapatite. Cultures of these cells were stimulated to form increased numbers of calcium-mineral-producing nodules by the oxysterol 25-hydroxycholesterol as well as by transforming growth factor-beta 1, both known to be present in atherosclerotic lesions. The stimulation of calcifying vascular cells in the artery wall by these two factors suggests a possible mechanism for the colocalization of calcification with atherosclerosis in vivo.
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PMID:TGF-beta 1 and 25-hydroxycholesterol stimulate osteoblast-like vascular cells to calcify. 818 41

The purpose of this study was to determine the response of bone cells to physical stress. Intermittent compressive force (ICF) was applied to 13 kPa to subconfluent ROS 17/2.8 cells at 18 cycles/min. After 48 h of this application, the cells were labelled with [35S]-methionine or [32PO4]. Application of ICF over this time did not alter the synthesis of type I collagen, fibronectin or bone SPARC (osteonectin) compared to that of control cells. However, the activity of alkaline phosphatase was increased 1.5-fold, and the synthesis of a 32PO4-labelled, 75-kDa phosphoprotein, recognized as osteopontin by immunoprecipitation with specific antibodies, was increased 1.4-fold. Also, an increase in osteopontin mRNA starting within 12h of ICF application was observed. The selective increase in osteopontin expression associated with ICF may be important in the remodelling of bone tissues during growth and development and in response to functional forces.
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PMID:Influence of an intermittent compressive force on matrix protein expression by ROS 17/2.8 cells, with selective stimulation of osteopontin. 838 21

The purpose of this study is to differentiate roles of several growth factors and cytokines in proliferation and differentiation of pulp cells during development and repair. In human pulp cell cultures, laminin and type I collagen levels per cell remained almost constant during the whole culture period (22 days). On the other hand, secreted protein, acidic and rich in cysteine (SPARC/osteonectin) and alkaline phosphatase (ALPase) levels markedly increased after the cultures reached confluence. Laminin and type I collagen, as well as fibronectin, stimulated the spreading of pulp cells within 1 h. Adding transforming growth factor-beta (TGF-beta) decreased laminin and ALPase levels, whereas it increased SPARC and fibronectin levels 3- to 10-fold. Western and Northern blots showed that TGF-beta enhanced SPARC synthesis at the protein and mRNA levels. Basic fibroblast growth factor (bFGF) decreased type I collagen, laminin, SPARC, and ALPase levels without changing the fibronectin level. Platelet-derived growth factor (PDGF) selectively decreased laminin, SPARC, and ALPase levels. Epidermal growth factor (EGF) also decreased SPARC and ALPase levels. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) decreased type I collagen and laminin levels, and abolished SPARC and ALPase syntheses. Of these peptides, bFGF and PDGF showed the greatest stimulation of [3H]thymidine incorporation into DNA. TGF-beta, EGF, and TNF-alpha had less effect on DNA synthesis, whereas IL-1beta inhibited DNA synthesis. These findings demonstrated that TGF-beta, bFGF, EGF, PDGF, TNF-alpha, and IL-1beta have characteristically different patterns of actions on DNA, laminin, type I collagen, fibronectin, ALPase, and SPARC syntheses by pulp cells.
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PMID:Differential effects of various growth factors and cytokines on the syntheses of DNA, type I collagen, laminin, fibronectin, osteonectin/secreted protein, acidic and rich in cysteine (SPARC), and alkaline phosphatase by human pulp cells in culture. 942 6

In the search for methods to improve the biocompatibility of prosthetic materials, attention has recently been directed toward the potential use of surface chemical modification and its influence on cellular behavior. This in vitro study investigates the effect of surface chemistry modification of bioceramics on human bone-derived cells (HBDCs) grown on biomaterial surfaces for 2 weeks. Cells were cultured on either alumina (Al2O3), alumina doped with magnesium ions ([Mg]-Al2O3), or hydroxyapatite (HAP), as well as tissue culture polystyrene (TCPS). Expression of alkaline phosphatase (ALP), thrombospondin (Tsp), osteopontin (OP), osteocalcin (OC), osteonectin (ON/SPARC), type I collagen (Col I), and bone sialoprotein (BSP) were determined in terms of mRNAs and proteins. Protein levels for ALP, OP, OC, and BSP were significantly (p < 0. 05) greater at day 5 in HBDCs cultured on [Mg]-Al2O3 compared to those cells grown on Al2O3. At day 14 the levels of ALP, Tsp, Col I, OP, ON/SPARC, and BSP rose significantly (p < 0.05) above those occurring in HBDCs grown on Al2O3, HAP, and TCPS. This suggests that HBDCs from the same patient respond to differences in the surface chemical groups. This study confirms that the chemistry of a substratum, which facilitates cellular adhesion, will enhance cellular differentiation.
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PMID:Effect of surface chemical modification of bioceramic on phenotype of human bone-derived cells. 1039 42

In spite of observed differences at the interface between boon and either commercially pure titanium [Ti(cpi)] or titanium alloy (Ti-6Al-4V), the mechanism of such a response is ill understood. This prompted further investigation of the influence of similar metals on human bone-derived cells (HBDCs). This study investigated the influence of Ti(cpi) and its alloy on osteoblastic proteins formed by HBDCs grown for 5, 7, 10, and 14 days on these metals and compared them to cells grown on tissue culture polystyrene plates. Messenger RNA and translated proteins that form an array of osteogenic parameters were determined: alkaline phosphatase (ALP), thrombospondin, osteopontin, osteocalcin (OC), osteonectin (ON/SPARC), type I collagen (Col I) and bone sialoprotein (BSP). At the four predetermined time points, cells grown on either Ti(cpi) or Ti-6Al-4V generally expressed similar mRNA levels, while levels of their respective proteins differed. Cells on Ti(cpi) had peak levels for most proteins at day 7, whereas those on Ti-6Al-4V peaked at either day 5 and/or day 7. At day 5 cells grown on Ti-6Al-4V had higher levels of ALP, Col I, ON/SPARC, OC, and BSP than those in Ti(cpi); this difference was not maintained at later time points in culture. The differential regulation of proteins occurring between cells from the same patient grown on titanium and its alloy implies that HBDCs respond to small differences in the surface chemistry and/or microcrystallinity.
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PMID:Titanium substrata composition influences osteoblastic phenotype: In vitro study. 1048 87


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