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Query: UMLS:C0265264 (HOS)
 1,119 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There is general agreement that calcitonin (CT) inhibits bone resorption by its effects on osteoclast function. CT was also found to have direct effects on osteoblast-like cells. In this study, we investigated the expression of CT and calcitonin gene-related peptide (CGRP), the two peptides encoded by the CT/CGRP gene, in human osteosarcoma cell lines and in normal human trabecular osteoblastic cells (HOB), and we studied the modulation of CT/CGRP gene expression by dibutyryl cyclic adenosine monophosphate ((Bu)2, cAMP), a cAMP analog. We first detected by Northern blot hybridization the presence of CT and CGRP mRNAs in different osteosarcoma cell lines (OHS-4, MG-63, Saos-2, HOS-TE85) and HOB cells. In the steady state, OHS-4 cells express slightly more CT and CGRP mRNAs than other cell lines or normal human osteoblasts, in parallel with messengers of differentiated osteoblasts, such as osteocalcin (OC) and alkaline phosphatase (ALP). OHS-4 cells also express CT and CGRP proteins, as demonstrated by immunocytochemistry. Stimulation of OHS-4 cells with 1 mM (Bu)2 cAMP induced a significant increase in mRNA levels for CT (x 2.5) and CGRP (x 3), as determined by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) procedure. The involvement of a transcriptional mechanism in this effect was evidenced by nuclear run-off transcription assay. In addition, (Bu)2 cAMP increased OC (x 4) and ALP (x 3) mRNA levels in OHS-4 cells. These effects were observed at 24 h and were maximal at 48 h, indicating that (Bu)2, cAMP induced cell differentiation and increased the transcription of the CT/CGRP gene in OHS-4 osteoblast-like cells. The results indicate that human osteosarcoma cells and primary human osteoblastic cells express CT and CGRP mRNA and proteins, and that (Bu)2 cAMP, an activator of protein kinase A, induces up-regulation of osteoblastic phenotypic genes and enhances CT and CGRP gene transcription, indicating that induction of osteoblastic differentiation by (Bu)2 cAMP is associated with enhanced expression of CT and CGRP in human osteoblastic cells.
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PMID:Expression of the CT/CGRP gene and its regulation by dibutyryl cyclic adenosine monophosphate in human osteoblastic cells. 938 85

We describe the development of flowcytometrical methods to analyse human primary osteoblast-like cultures obtained from trabecular bone explants in comparison to the human osteosarcoma cell line HOS 58. Two antigens typical of osteoblasts were studied: bone alkaline phosphatase and collagen/procollagen I; the non-specific attachment protein fibronectin served as control. The morphology of all different antigens is shown by immunocytochemistry before flowcytometrical analysis. The establishment of flowcytometry is described in detail. While all antigens tested were nearly 100% positive in the HOS 58 cells in immunocytochemistry and flowcytometry, in primary osteoblast-like cells results varied widely between both methods. Cell permeabilisation before flowcytometry improved the homogeneity of results, probably by increasing the accessibility of the specific antibody to intracellular compartments. Though up to 80% of cells were lost during preparation the ratio of positive versus negative cells in specific experiment was not dependent on the cell recovery. Therefore, the cells finally analysed seemed to be representative of the total population.
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PMID:Analysis of human primary bone cells by fluorescence activated cell scanning: methodological problems and preliminary results. 964 53

Cultured rodent osteoblastic cells reiterate the phenotypic maturation of osteoblasts seen in vivo. Under appropriate culture conditions this maturation is a stepwise sequence of phenotypic changes culminating in the production of a mineralised matrix. Although individual components of the osteoblast phenotype are apparent in transformed osteosarcoma cell lines, the co-ordination of the maturation sequence appears to be compromised. Because to date no comparable human cell differentiation system has been developed we investigated the recently introduced HOS 58 osteosarcoma cell line up to 3 months in culture. Proliferation, the secretion of osteoblast specific proteins, gene expression and mineralisation were analysed at different time points. Low-density HOS 58 cultures exhibit rapid proliferation and high levels of c-myc, collagen type I and osteopontin mRNAs. This phenotypic stage was maximum between the 4th and 5th days of culture. As cell density increased expression of these genes declined and by day 14 the predominant mRNAs was alkaline phosphatase. Osteocalcin secretion was detected after confluence at an increasing level. In the presence of ascorbate and beta-glycerophosphate the production of alkaline phosphatase and collagen type I increased coincident with the elaboration of a Von Kossa staining matrix. Nevertheless no proper mineralisation of the collagenous matrix was detectable by electron microscopy. Hence, the human osteosarcoma cell line HOS 58 expressed a rather differentiated phenotype with further maturation during a culture period of 21 days. We conclude that the developmental sequence exhibited by the HOS 58 human osteosarcoma cell line is comparable to that described for primary rat osteoblasts. However, in detailed analysis considerable differences to other species are evident. Further evaluation of the HOS 58 system and comparison to other human osteoblast cell lines will be necessary to establish the most appropriate differentiation model for human bone cell cultures.
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PMID:In vitro differentiation potential of a new human osteosarcoma cell line (HOS 58). 967 17

Periprosthetic osteolysis is a major cause of aseptic loosening in artificial joint replacement. It is assumed to occur in conjunction with the activation of macrophages. We have shown in vitro that human osteoblast-like cells, isolated from bone specimens obtained from patients undergoing hip replacement, phagocytose fine particles of titanium alloy (TiAlV). The human osteoblast-like cells were identified immunocytochemically by the presence of bone-specific alkaline phosphatase (BAP). With increasing duration of culture, a variable number of the osteoblastic cells became positive for the macrophage marker CD68, independent of the phagocytosis of particles, with a fine granular cytoplasmic staining which was coexpressed with BAP as revealed by immunodoublestaining. The metal particles were not toxic to the osteoblastic cells since even in culture for up to four weeks massively laden cells were vital and had a characteristic morphology. Cells of the human osteosarcoma cell line (HOS 58) were also able to phagocytose metal particles but had only a low expression of the CD68 antigen. Fluorescence-activated cell scanning confirmed our immunocytochemical results. Additionally, the cells were found to be negative for the major histocompatibility complex-II (MHC-II) which is a marker for macrophages and other antigen-presenting cells. Negative results of histochemical tests for tartrate-resistant acid phosphatase excluded the contamination by osteoclasts or macrophages in culture. Our observations suggest that the osteoblast can either change to a phagocytosing cell or that the phagocytosis is an underestimated property of the osteoblast. The detection of the CD68 antigen is insufficient to prove the monocytic lineage. In order to discriminate between macrophages and osteoblasts additional markers should be used. To our knowledge, this is the first demonstration of cells of an osteoblastic origin which have acquired a mixed phenotype of both osteoblasts and macrophages.
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PMID:Human osteoblast-like cells phagocytose metal particles and express the macrophage marker CD68 in vitro. 1075 42

In this report, we studied the relationship between telomerase activity and in vitro differentiation of osteosarcoma cells. Human osteosarcoma cells (HOS-8603) were treated with all-trans-retinoic acid (RA) and dexamethasone (DEX). Cell cycle phase, alkaline phosphatase (AP) activity, telomerase activity, and human telomerase RNA (hTR) in treated cells were detected. The results showed that the treated cells underwent morphologic differentiation. AP activity of the cells increased significantly. The proportion of the cells in S and G2/M phases was increased. A pronounced decline in telomerase activity was observed, but no significant difference in the amount of hTR expressed, when compared with the control. This study demonstrates that: (1) both RA and DEX can inhibit cell growth and induce morphologic and functional differentiation of HOS-8603 cells; (2) telomerase is an enzyme system regulated during induced differentiation of HOS-8603 cells; (3) significantly decreased telomerase activity may be an indicator of differentiation but does not parallel the expression level of hTR; and (4) the regulation of telomerase is directly linked to cell differentiation not cell cycle.
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PMID:Repression of telomerase activity during in vitro differentiation of osteosarcoma cells. 1185 1

Cultured rodent osteoblastic cells reiterate the phenotypic differentiation and maturation of osteoblasts seen in vivo. As previously shown, the human osteosarcoma cell line HOS 58 represents a differentiated stage of osteoblast development. The potential of HOS 58 for still further in vitro differentiation suggests the line can serve as a model of osteoblast maturation. Using this cell line, we have investigated the influence of 1,25-(OH)2-D3 (D3), TGF-beta and Dexamethasone (Dex) on proliferation and on the protein and mRNA levels of alkaline phosphatase (AP), procollagen 1 (Col 1), and osteocalcin (Oc), as well as mineralization during 28 days in culture. AP mRNA and protein were highly expressed throughout the culture period with further increase of protein AP activity at constant gene expression levels. A differentiation inhibiting effect of either TGF-beta or Dex was seen. Col 1 was investigated without the use of ascorbic acid and showed only minor changes during culture time or stimulation. The gene expression for Oc increased continually whereas protein synthesis peaked at confluence and decreased thereafter. TGF-beta and Dex treatments decreased Oc mRNA and protein levels. Stimulation by D3 was maximal at day 7 with a decrease thereafter. HOS 58 cells showed no mineralization capacity when stimulated with different agents, as measured by energy-dispersive X-ray microanalysis. This was not due to absence of Cbfa1 expression. In conclusion, the HOS 58 osteosarcoma cell line represents a differentiated cell line with highly expressed and physiologically regulated AP expression during further differentiation in culture. We observed a dissociation between osteocalcin gene expression and protein secretion which may contribute to the lack of mineralization in this cell line.
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PMID:Prolonged culture of HOS 58 human osteosarcoma cells with 1,25-(OH)2-D3, TGF-beta, and dexamethasone reveals physiological regulation of alkaline phosphatase, dissociated osteocalcin gene expression, and protein synthesis and lack of mineralization. 1194 84

This investigation studied how the behaviour of isolated osteoblasts on standard tissue culture polystyrene compared with cells cultured on cut surfaces of dentin, a natural calcified material. Cellular attachment, viability and growth were monitored in parallel cultures of human osteosarcoma cell lines (MG63, HOS TE85, SaOS-2) and primary human osteoblast-like cells (HOBs). Culture plastic was either left untreated or roughened with abrasive paper of various grit sizes (4000-1200 grit) in order to obtain a level of roughness comparable to that of the dentin slices. Cell counting and intracellular BCECF staining showed that after an initial incubation of 2 h, the primary cells attached and spread out more quickly on the different substrates than the three cell lines. The primary cells also showed a stronger mitochondrial staining and viability on dentin. During subsequent culture morphological differences appeared with the cells on dentin displaying more cellular extensions. All three cell lines proliferated more slowly on dentin than on plastic. In contrast, the primary HOBs were not significantly affected in their growth by the different substrates. Total and specific alkaline phosphatase (AP) activity of the cell lines was not significantly affected by the different substrates after short-term adhesion, but it was increased for the primary cells on the dentin. However, after 2-3 days of culture, AP was decreased on the dentin slices for both the cell lines and primary HOBs. Plasma treatment of the roughened plastic did not alter cellular viability or AP activity, suggesting that grinding of the surface did not affect the property of the culture plastic to support cell attachment and growth. In conclusion, the results show that not only do osteoblastic cells behave differently on a natural calcified substrate surface than on standard culture plastic, but also that differences were evident between the various cell types, in particular the primary HOB versus the continuous cell lines.
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PMID:In vitro behaviour of human osteoblasts on dentin and bone. 1199 63

An osteoblastic cell line (HOS cells) produces a prominent osteoid matrix with mineralization. Fibroblasts, on the other hand, do not exhibit this mineralization. To evaluate the degree of mineralization, we added calcein to the culture medium and then observed the culture wells by using an image analyzer. The calcein uptake into the cell/matrix layer was detected in the HOS cells but not in the fibroblasts. The calcein uptake was also quantified in situ by using an image analyzer, which revealed high levels in the HOS cells, which correlated well with the calcium content of the mineralized matrix. Rat marrow cells were also cultured in media containing calcein, fetal bovine serum, beta-glycerophosphate, L-ascorbic acid 2-phosphate, and with or without dexamethasone. With the dexamethasone, the cells exhibited osteogenic differentiation that resulted in mineralized matrix formation after about 10 days. The matrix formation coincided with the appearance of calcein uptake into the cell/matrix layer, with the amount of calcein uptake increasing with time. By contrast, the culture without the dexamethasone did not exhibit matrix formation and the calcein uptake was negligible. In the case of both HOS cell and rat marrow cell cultures in vitro, calcein did not affect expressions of their alkaline phosphatase activity or osteocalcin production. Furthermore, histologic observation revealed that rat marrow cells subcultured with calcein could show osteogenic ability after in vivo implantation. These results suggest that the current method of detecting calcein uptake in a culture allows the monitoring of the osteogenic capacity of cultured cells, as well as the measurement of the amount of mineralization produced by the osteogenic cells. Given that osteogenic cultured cells/mineralized matrices are used in bone reconstruction surgery, the in situ monitoring method is invaluable in that it allows us to evaluate the osteogenic capacity of in vitro constructs.
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PMID:In-situ visualization and quantification of mineralization of cultured osteogenetic cells. 1295 91

Bone morphogenetic protein-6 (BMP-6) is a potent inducer of osteogenic differentiation and its expression is stimulated by 17beta-estradiol. The existence of a regulatory loop between sex steroids and BMP-6 is therefore reasonable to hypothesize. Here we determined whether the sex steroids 17beta-estradiol and dihydrotestosterone, and the phytoestrogen resveratrol can modulate BMP-6-induced alkaline phosphatase activity and osteocalcin expression. Mesenchymal cells of murine (osteoblastic MC3T3-E1 cells, preadipogenic ST2 cells, prechondrogenic ATDC5 cell) and human origin (osteosarcoma SaOS and HOS cells, primary bone marrow stromal cells) were cultured in the presence of recombinant BMP-6 under serum-free conditions. BMP-6 dose-, and time-dependently increased alkaline phosphatase activity in murine cell lines, but not in human cells. Osteocalcin expression was also increased upon stimulation with BMP-6. The presence of 17beta-estradiol, dihydrotestosterone, and resveratrol had no effect on BMP-6-induced alkaline phosphatase activity and osteocalcin expression. These data suggest that osteogenic differentiation in response to BMP-6 occurs independent of steroid hormones and resveratrol in mesenchymal cells that express basal receptor levels.
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PMID:BMP-6-induced osteogenic differentiation of mesenchymal cell lines is not modulated by sex steroids and resveratrol. 1296 49

The cells in bone grow on a composite matrix made up of mineral and organic (mainly type-I collagen) components. In this study, anorganic bone mineral (ABM) particles were coated with a cell-binding domain of type-I collagen (P-15 peptide) to mimic the bone matrix components and suspended in injectable hyaluronate (Hy) hydrogels. The ABM/P-15/Hy was compared to ABM/Hy-the same matrix without P-15 peptide. Osteoblast-like HOS cells migrated through the hydrogels around ABM/P-15 or ABM particles; however, more cells adhered to ABM/P-15/Hy particles, and the cells formed better surface coverage and had more stress fibers on ABM/P-15/Hy. HOS cells cultured on ABM/P-15/Hy had increased osteogenic gene expression for alkaline phosphatase and bone morphogenetic proteins, and deposited more mineralized matrix. Studies with two different hydrogels (carboxymethylcellulose and sodium alginate) showed similar enhanced cell attachment and mineralization. The studies suggest that the ABM/P-15 in hydrogels can be used as an injectable biomimetic matrix to facilitate bone repair.
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PMID:Enhanced cell attachment and osteoblastic activity by P-15 peptide-coated matrix in hydrogels. 1457 11


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