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At least 415 records · Page 23Linked to original sources
PubMed1988

Investigations of the relationship between cell proliferation and differentiation of HL-60 cells induced to differentiate by N-methylformamide.

The relationship between the N-methylformamide (NMF)-induced differentiation of HL-60 human promyelocytic leukemia cells, to myeloid cells, and their proliferative potential was determined in suspension culture. Continuous incubation with 170 mM NMF induced 70% of cells to differentiate after 2-2.5 cell divisions, whether or not cells were replenished with fresh medium and serum. 100 mM NMF induced significant levels of differentiation only when cells were allowed to reach a plateau of growth, and this was prevented by replenishment of the medium and serum. Under these conditions of "re-feeding", the cells could be made to undergo greater than 10 cell divisions, and differentiated only when they were allowed to reach a plateau in their growth. The data suggests that NMF may induce differentiation only when the proliferative potential of the cells is limited, either by the drug itself or by the conditions of growth.

Antineoplastic Agents↗
PubMed1994

Establishment of a retrodifferentiated cell line from a single differentiated rat myelomonocytic leukemia cell: possible roles of retrodifferentiation in relapses of leukemia after differentiation-inducing therapy.

In order to demonstrate possible roles of retrodifferentiation in relapses after differentiation therapies, we have established a retrodifferentiated cell line (RD-1) from a single rat myelomonocytic leukemia cell which differentiated into a macrophage-like cell by treatment with lipopolysaccharide (LPS). The established RD-1 cells showed microscopic features slightly maturer than their parent cells. The RD-1 cells had the ability to differentiate into macrophage-like cells by treatment with fewer doses of LPS than those for parent cells. All rats inoculated with the parent cells (more than 10(2)/rat) died within 50 days. Rats inoculated with 10(4) RD-1 cells survived for more than 120 days, whereas two out of four rats inoculated with 10(5) cells and all the rats inoculated with 5 x 10(5) cells died of leukemia. These results suggest that RD-1 cells are retrodifferentiated cells from a single rat myelomonocytic leukemia cell which differentiated into a macrophage-like cell; they have similar phenotypes and lower tumorigenicity than the parent cells and they also suggest that the appearance of retrodifferentiated leukemia cells may be responsible for relapse after differentiation therapy for leukemia in some cases.

Animals↗
PubMed1995

High potassium promotes differentiation of retinal neurons but does not favor rod differentiation.

Neural retinal cells of newborn rats were cultured under dissociated culture conditions. Differentiation of several types of retinal cells was confirmed by immunohistochemical detection of type-specific neural phenotypes. We used Thy-1.1 antigen as a ganglion cell marker, HPC-1 or GABA as an amacrine cell marker and rhodopsin as a rod cell marker. With a high concentration of potassium (38 mM), expression of the respective neural phenotypes were differentially affected. High K+ increased the number of Thy-1.1 positive cells 6 to 8 fold, and drastically promoted their neurite extension. The same culture conditions, however, reduced considerably the number of rhodopsin positive cells, possibly due to the unique membrane properties of photoreceptors. A high K+ concentration also promoted differentiation of HPC-1 positive and GABA positive cells, but to a lesser extent than the Thy-1.1 positive cells. Several possibilities were examined to understand the effect of a high K+ concentration on retinal neural cells. The total cell number in cultures with a high K+ concentration was approximately half of that in control cultures at day 3 and slightly smaller at day 11, suggesting that high K+ did not have a positive general effect on the proliferation or survival of retinal cells. Naturally occurring neuronal death (apoptosis) is a well-known phenomenon during retinal development. A histochemical method for detecting DNA fragmentation, a step preceding apoptosis, showed that high K+ had no preventive effect. BrdU (bromodeoxyuridine) immunohistochemistry showed that high K+ did not seem to enhance proliferation of neural precursor cells. These results indicate that a high K+ concentration promotes the expression of neuronal phenotypes but is not a favorable condition for rod differentiation. Since a high K+ concentration is considered to induce depolarization of nerve cells, the present results suggest an anterograde influence from surrounding neuronal cells, through chronic depolarization by elevated K+, is essential for the differentiation and maturation of retinal cells.

Animals↗
PubMed1996

Cis-elements involved in differential expression of Na(+)-K(+)-ATPase alpha 2 subunit gene in muscle differentiation.

The mRNA of the Na(+)-K(+)-ATPase alpha 2 subunit gene (Atpla2) increases during myogenesis in rat following birth. To investigate the mechanism of the transcriptional regulation underlying this process, we examined the promoter activity of Atpla2 by transient transfection assays in myocyte differentiation, using C2C12 murine skeletal myoblast cell line. The promoter activity was increased about 5-fold in the differentiated cells, comparing with that in the growing cells. By analyses of 5'-deletion mutations of the gene, the responsible elements were localized in the region between -108 and +60. We identified a binding factor that exists only in the nuclear extract from the growing cells but not in the extract from the differentiated cells with a probe DNA fragment from +20 to +50 by gel retardation assays. The element to which the factor binds can mediate the inhibition of alpha 2 gene expression in the growing C2C12 cells but not in the differentiated cells. Finally we revealed protein occupancy in this region in the growing cells by in vivo footprinting. We propose a model that the increased expression of Atpla2 during muscle differentiation is mediated by the disappearance of a negative factor.

Animals↗
PubMed1993

Differentiation of human monoblastic leukemia U937 cells induced by inhibitors of myosin light chain kinase and prevention of differentiation by granulocyte-macrophage colony-stimulating factor.

Inhibitors of protein kinase activities are useful for the study of intracellular signal transduction and some of these inhibitors are reported to induce differentiation of human leukemia cells. We examined effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) in combination with several kinase inhibitors on differentiation of human leukemia U937 cells. Nitroblue tetrazolium (NBT)-reducing activity, a typical marker of myelomonocytic differentiation, of U937 cells was induced by genistein and GM-CSF enhanced this activity. GM-CSF also induced the NBT-reducing activity of the cells in combination with 2,5-dihydroxycinnamic acid methyl ester, psi-tectorigenin and staurosporine, although each of them did not induce the activity. Inhibitors of myosin light chain kinase, 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9) and 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-7), induced in U937 cells NBT-reduction, and lysozyme and alpha-naphthyl acetate esterase activities. GM-CSF inhibited this differentiation and counteracted the anti-proliferation effect of the kinase inhibitors. These results suggest that some protein kinases are involved in differentiation of U937 cells and the kinases inhibited by ML-9 and ML-7 are associated with signal transduction of GM-CSF.

Azepines↗
PubMed1996

Induction of murine erythroleukemia cell differentiation is associated with methylation and differential stability of poly(A)+ RNA transcripts.

Murine erythroleukemia (MEL) cells exposed to DMSO were assessed for their ability to methylate poly(A)+ RNA and accumulate RNA transcripts of globin and nonglobin genes (c-myc, beta-actin and MER5). Cells were pulse-labeled with L-[methyl-3H]methionine, cytoplasmic RNA was isolated, selected for poly(A)+ RNA and analyzed by HPLC chromatography for methylated nucleosides. When MEL cells were exposed to inhibitors of RNA methylation (neplanocin A, 3-deazaneplanocin A and cycloleucine) and assessed for their ability to differentiate by DMSO, accumulate RNA transcripts, produce hemoglobin, methylate poly(A)+ and poly(A)- RNA and synthesize S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH), we observed the following: (a) MEL cells treated with DMSO underwent hypermethylation in poly(A)+ RNA that preferentially occurred at the 5'-cap structures (7-methylguanosine and 2'-O-methylcytidine and 2'-O-methyluridine); (b) inducer-treated MEL cells exhibited a decrease in the intracellular level of SAH that led to a lower ratio of SAH/SAM, an event that favors methylation; and (c) treatment of MEL cells with inhibitors of RNA methylation suppressed methylation of poly(A)- and poly(A)+ RNA, reversed the ratio SAH/SAM seen in differentiated MEL cells and prevented differentiation to occur. Moreover, we observed that treatment of MEL cells with selective inhibitors of RNA methylation caused fragmentation of beta major globin and c-myc mRNAs, two RNA transcripts coded by developmentally regulated genes, while had no detectable effect on the structural integrity of poly(A)+ RNA transcripts transcribed by two housekeeping genes (beta-actin and MER5). These data indicate that induction of erythroid cell differentiation of MEL cells is associated with changes in methylation of poly(A)+ RNA and selective differential stability of RNA transcripts, two events that might be related to each other.

Actins↗
PubMed1993

Microcystic adnexal carcinoma of the skin. A reappraisal of the differentiation and differential diagnosis of an underrecognized neoplasm.

BACKGROUND: Microcystic adnexal carcinoma (MAC) is a locally aggressive adnexal neoplasm whose histogenesis is disputed. Many cases referred to us had been misdiagnosed. OBJECTIVE: Our purpose was to clarify the differential diagnosis and differentiation of MAC. METHODS: We sought follow-up data and examined routinely stained sections from 17 cases. We performed immunoperoxidase stains for carcinoembryonic antigen, pilar keratin (AE13), proliferating cell nuclear antigen (PCNA), type IV collagen, p53, and CD34 on selected cases. RESULTS: Nine biopsy specimens had initially been misinterpreted. Cysts containing compact keratin or shadow cells were present in 11 cases, which we interpret as evidence of follicular differentiation. Sebaceous gland and duct as well as inner root sheath structures were seen in one case each. CD34 did not mark the clear cells as it does those of the outer root sheath. Staining for PCNA, type IV collagen, and p53 did not distinguish MAC from benign adnexal neoplasms. CONCLUSION: MAC can be distinguished from its simulants in adequate biopsy specimens. Incompletely excised lesions usually recur. Both follicular and sudoriforous differentiation is present. Type IV collagen, PCNA, and p53 antisera were not useful in differential diagnosis.

Adult↗
PubMed2006

MicroRNA-1 facilitates skeletal myogenic differentiation without affecting osteoblastic and adipogenic differentiation.

MicroRNAs (miRNAs) are small non-coding RNAs emerging as important post-transcriptional gene regulators. In this study, we examined the role of miR-1, an miRNA specifically expressed in cardiac and skeletal muscle tissue, on the myogenic, osteoblastic, and adipogenic differentiation of C2C12 cells. Upon induction of myogenic differentiation, miR-1 was robustly expressed. Retrovirus-mediated overexpression of miR-1 markedly enhanced expression of muscle creatine kinase, sarcomeric myosin, and alpha-actinin, while the effects on myogenin and MyoD expression were modest. Formation of myotubes was significantly augmented in miR-1-overexpressing cells, indicating miR-1 expression enhanced not only myogenic differentiation but also maturation into myotubes. In contrast, osteoblastic and adipogenic differentiation was not affected by forced expression of miR-1. Thus, the muscle-specific miRNA, miR-1, plays important roles in controlling myogenic differentiation and maturation in lineage-committed cells, rather than functioning in fate determination.

3T3-L1 Cells↗
PubMed2004

Differential modulation of PI3-kinase/Akt pathway during all-trans retinoic acid- and Am80-induced HL-60 cell differentiation revealed by DNA microarray analysis.

All-trans retinoic acid (ATRA) and Am80 are natural and synthetic derivatives of Vitamin A and have been used in the fields of oncology and dermatology for years. Their action was considered to be achieved mainly through binding to nuclear hormone receptors, retinoic acid receptors (RARs), although they have been observed to have different biological effects. For example, the two compounds have similar effects on differentiation but different effects on proliferation in human promyelocytic leukemia cell line HL-60 cells. To elucidate the genes responsible for this and other differences, we attempted for the first time to determine the genes whose expressions were differentially modulated during the time course of HL-60 cell differentiation by ATRA and Am80 treatment up to 72h utilizing DNA microarray and clustering analyses. As a result, the expressions of 204 genes were found to be modulated differentially by ATRA and Am80. Among them, we focused on two components of the PI3-kinase/Akt signal transduction pathway, phosphoinositide-3-kinase, beta-catalytic subunit and ribosomal protein S6 kinase polypeptide 1, which are related to the regulation of cell proliferation and apoptosis. Their expressions were specifically suppressed by ATRA, which coincided with the suppressive effects of ATRA on the HL-60 cell proliferation. Moreover, PI3-kinase inhibitors suppressed the proliferation of Am80-treated cells to the same extent as ATRA did. These results indicated that these gene products play a role in HL-60 cell growth suppression during the late stage of differentiation. The complete data and a list of the genes are available at .

Antineoplastic Agents↗
PubMed2004

Differential growth factor control of bone formation through osteoprogenitor differentiation.

The osteogenic factors bone morphogenetic protein (BMP-7), platelet-derived growth factor (PDGF)-BB, and fibroblast growth factor (FGF-2) regulate the recruitment of osteoprogenitor cells and their proliferation and differentiation into mature osteoblasts. However, their mechanisms of action on osteoprogenitor cell growth, differentiation, and bone mineralization remain unclear. Here, we tested the hypothesis that these osteogenic agents were capable of regulating osteoblast differentiation and bone formation in vitro. Normal human bone marrow stromal (HBMS) cells were treated with BMP-7 (40 ng ml(-1)), PDGF-BB (20 ng ml(-1)), FGF-2 (20 ng ml(-1)), or FGF-2 plus BMP-7 for 28 days in a serum-containing medium with 10 mM beta-glycerophosphate and 50 microg ml(-1) ascorbic acid. BMP-7 stimulated a morphological change to cuboidal-shaped cells, increased alkaline phosphatase (ALKP) activity, bone sialoprotein (BSP) gene expression, and alizarin red S positive nodule formation. Hydroxyapatite (HA) crystal deposition in the nodules was demonstrated by Fourier transform infrared (FTIR) spectroscopy only in BMP-7- and dexamethasone (DEX)-treated cells. DEX-treated cells appeared elongated and fibroblast-like compared to BMP-7-treated cells. FGF-2 did not stimulate ALKP, and cell morphology was dystrophic. PDGF-BB had little or no effect on ALKP activity and biomineralization. Alizarin Red S staining of cells and calcium assay indicated that BMP-7, DEX, and FGF-2 enhanced calcium mineral deposition, but FTIR spectroscopic analysis demonstrated no formation of HA similar to human bone in control, PDGF-BB-, and FGF-2-treated samples. Thus, FGF-2 stimulated amorphous octacalcium phosphate mineral deposition that failed to mature into HA. Interestingly, FGF-2 abrogated BMP-7-induced ALKP activity and HA formation. Results demonstrate that BMP-7 was competent as a sole factor in the differentiation of human bone marrow stromal cells to bone-forming osteoblasts confirmed by FTIR examination of mineralized matrix. Other growth factors, PDGF, and FGF-2 were incompetent as sole factors, and FGF-2 inhibited BMP-7-stimulated osteoblast differentiation.

Becaplermin↗
PubMed2006

Glucocorticoids induce the differentiation of a mesenchymal progenitor cell line, ROB-C26 into adipocytes and osteoblasts, but fail to induce terminal osteoblast differentiation.

To clarify the effects of glucocorticoids (GCs) on osteoblast and adipocyte differentiation, we investigated the effects of dexamethasone (Dex), a GC analogue on transcription factors for osteoblasts (Runx2, Dlx5 and Osterix) and adipocytes (C/EBPs such as C/EBPalpha, C/EBPbeta and C/EBPdelta, and PPARgamma2), late osteoblastic markers, bone sialoprotein (BSP) and osteocalcin (OC), and adipocyte differentiation-dependent protein, aP2 in a clonal mesenchymal progenitor cell line, ROB-C26 (C26). C26 cells were dose- and time-dependently responsive to Dex in terms of an increase in not only mRNA and protein expressions of the C/EBPs, PPARgamma2 and aP2, but also Runx2, Dlx5, BSP and OC with no induction of Osterix, which is considered to act mainly on terminal osteoblast differentiation. Cycloheximide pretreatment indicated that Dex signaling immediately increases expressions of the C/EBPs and Dlx5, while expressions of the rest of the genes require de novo protein synthesis. Continuous Dex treatment stimulated adipocyte formation, but failed to induce Osterix expression and mineralized matrix formation. However, BMP-2 treatment of Dex-treated cells induced Osterix expression and subsequent mineralized matrix formation. These results indicate that Dex up-regulates the C/EBPs followed by increasing PPARgamma2 and aP2 expressions in C26 cells to induce adipocyte differentiation, while Dex enhances Dlx5 followed by increasing Runx2, BSP and OC expressions at gene and protein levels, but cannot induce Osterix expression, suggesting that Dex does not promote their terminal osteoblast differentiation.

Adipocytes↗
PubMed2006

Analytic formulas for discrete stochastic models of cell populations with both differentiation and de-differentiation.

Cell differentiation often appears to be a stochastic process particularly in the hemopoietic system. One of the earliest stochastic models for the growth of stem cell populations was proposed by Till et al. in 1964. In this model there are just two cell types: stem cells and specialized cells. At each time step there is a fixed probability that a stem cell differentiates into a specialized cell and a fixed probability that it undergoes mitosis to produce two stem cells. Even though this model is conceptually simple the myriad of possible outcomes has made it difficult to analyse. We present original closed-form expressions for the probability functions and a fast algorithm for computing them. Renewed interest in stem cells has raised questions about the effect de-differentiation has on stem cell populations. We have extended the stochastic model to include de-differentiation and show that even a small amount of de-differentiation can have a large effect on stem cell population growth.

Algorithms↗
PubMed2002

Molecular analysis of expansion, differentiation, and growth factor treatment of human chondrocytes identifies differentiation markers and growth-related genes.

This study is intended to optimise expansion and differentiation of cultured human chondrocytes by growth factor application and to identify molecular markers to monitor their differentiation state. We dissected the molecular consequences of matrix release, monolayer, and 3D-alginate culture, growth factor optimised expansion, and re-differentiation protocols by gene expression analysis. Among 19 common cartilage molecules assessed by cDNA array, six proved best to monitor differentiation. Instant down-regulation at release of cells from the matrix was strongest for COL 2A1, fibromodulin, and PRELP while LUM, CHI3L1, and CHI3L2 were expansion-related. Both gene sets reflected the physiologic effects of the most potent growth-inducing (PDGF-BB) and proteoglycan-inducing (BMP-4) factors. Only CRTAC1 expression correlated with 2D/3D switches while the molecular phenotype of native chondrocytes was not restored. The markers and optimised protocols we suggest can help to improve cell therapy of cartilage defects and chondrocyte differentiation from stem cell sources.

Becaplermin↗
PubMed2002

Differential cytoskeletal association of ErbB1 and ErbB2 during keratinocyte differentiation.

ErbB1 and ErbB2 display differential subcellular localization in human skin and cultured keratinocytes. To determine whether ErbB1 and ErbB2 also differ in cytoskeletal binding properties, normal human keratinocytes grown under conditions favoring a basal or differentiated phenotype were repeatedly extracted in a non-ionic detergent buffer. In basaloid keratinocytes, cytoskeletal association of ErbB1 and ErbB2 was limited. ErbB1 ( approximately 5%) was tightly associated with the cytoskeleton, compared to <1% of ErbB2 (p=0.004). After EGF stimulation, activated ErbB1 and ERK associated with the cytoskeleton to a greater extent than did total ErbB1 and total ERK. Association of ErbB2 increased markedly in differentiated keratinocytes, whereas association of ErbB1 was similar in basaloid and differentiated cells. Cytoskeletal association of ErbB2 correlated with plasma membrane localization. These results suggest that ErbB1 and ErbB2 employ different mechanisms of plasma membrane targeting during keratinocyte differentiation, and that cytoskeletal association may facilitate the coupling of activated ErbB1 and ERK.

Calibration↗
PubMed2003

Simvastatin induces osteoblastic differentiation and inhibits adipocytic differentiation in mouse bone marrow stromal cells.

To clarify the mechanism of the stimulatory effect of statins on bone formation, we investigated the effect of simvastatin, a widely used statin, on osteoblastic and adipocytic differentiation in primary cultured mouse bone marrow stromal cells (BMSCs). Simvastatin treatment enhanced the expression level of mRNA for osteocalcin and protein for osteocalcin and osteopontin, and increased alkaline phosphatase activity significantly (p<0.05). After BMSCs were exposed to an adipocyte differentiation agonist, Oil Red O staining, fluorescence activated cell sorting, and decreased expression level of lipoprotein lipase mRNA showed that treatment with simvastatin significantly inhibits adipocytic differentiation compared to controls that did not receive simvastatin (p<0.05). Lastly, we found that simvastatin induces high expression of BMP(2) in BMSCs. These observations suggested that simvastatin acts on BMSCs to enhance osteoblastic differentiation and inhibits adipocytic differentiation; this effect is at least partially mediated by inducing BMP(2) expression in BMSCs.

Adipocytes↗
PubMed1988

Effect of fibroblast-derived differentiation inducing factor on the differentiation of human monocytoid and myeloid leukemia cell lines.

A fibroblast-derived differentiation inducing factor (F-DIF) purified from medium conditioned by a human fibroblast cell line (WI-26VA4) induced differentiation of human monocytic leukemia cell lines (U-937, THP-1) into cells with macrophage characteristics. F-DIF alone induced the differentiation of ML-1 cells only marginally, but it synergistically increased the differentiation when combined with TNF. Interferon-gamma, tumor necrosis factor, GM-CSF, interleukin-1 and interlukin-4 synergistically enhanced the differentiation of U-937 cells when combined with F-DIF.

Cell Differentiation↗
PubMed2002

CCK processing by pituitary GH3 cells, human teratocarcinoma cells NT2 and hNT differentiated human neuronal cells evidence for a differentiation-induced change in enzyme expression and pro CCK processing.

Human teratocarcinoma Ntera2/c 1.D1 (NT2) cells express very low levels of the prohormone convertase enzyme PC1, moderate levels of PC2 and significant levels of PC5. When infected with an adenovirus which expresses rat CCK mRNA, several glycine-extended forms were secreted that co-eluted with CCK 33, 22 and 12. Amidated CCK is not produced because these cells appear to lack the amidating enzyme. Pituitary GH3 cells express high levels of PC2 and PC5. CCK adenovirus-infected GH3 cells secrete amidated versions of the same peptides as NT2 cells. Differentiation of NT2 cells into hNT cells with retinoic acid and mitotic inhibitors increased expression of PC5 and decreased expression of PCI and PC2. CCK adenovirus-infected differentiated hNT cells also secrete glycine extended CCK products and the major molecular form produced co-eluted with CCK 8 Gly. These experiments demonstrate that the state of differentiation of this neuronal cell line influences its expression of PC 1,2, and 5 and its cleavage of pro CCK and suggests that these cells may make an interesting model to study how differentiation alters prohormone processing. These results also support the hypothesis that PC5 in differentiated neuronal cells is capable of processing pro CCK to glycine-extended CCK 8.

Aspartic Acid Endopeptidases↗
PubMed2002

Dexamethasone and retinoic acid differentially regulate growth and differentiation in an immortalised human clonal bone marrow stromal cell line with osteoblastic characteristics.

Clonogenic immortalised human pre-osteoblastic cell lines provide useful species-specific experimental tools for the study of the regulation of osteoblastic proliferation and differentiation. Steroid hormones are major regulators of bone formation. Although much is known about the effects of dexamethasone on osteoblastic growth and differentiation in vitro, there is less information on the effects of trans-retinoic acid (RA), particularly in human cultures. We have established a clonal adult human cell line (C1) derived from a bone marrow aspirate. The cell line appeared to be bi-potential. The cells were able to differentiate into an adipocytic phenotype under appropriate culture conditions. When grown in osteogenic medium, the cells expressed alkaline phosphatase (ALP) and osteocalcin mRNA. The C1 cells also expressed several other osteoblastic markers such as collagen type 1 (COL 1), PTH/PTH-rp receptor constitutively. Transcripts for the osteoblast transcription factor Cbfa1 was also detected under basal conditions. In addition treatment with 1,25(OH)(2)D(3) (10(-7)M) led to a marked increase in osteocalcin mRNA expression suggesting that this cell line represents a pre-osteoblastic population. We compared the effects of Dex and RA on osteoblastic function. For the assessment of PTH/PTH-rp receptor, osteocalcin and Cbfa1 mRNA expression and PTH-stimulated adenylate cyclase responsiveness, the cells were grown in the presence of Dex and RA and harvested on Days 1, 3, 7 and 14. RA (10(-7)M) had a mitogenic effect on the C1 cells. In contrast, Dex (10(-7)M) inhibited proliferation. A similar effect was observed with primary human bone marrow stromal cultures. Both Dex and RA inhibited COL 1 synthesis and decreased COL1 mRNA. Dex stimulated ALP activity and increased ALP mRNA expression whilst RA had an inhibitory effect. Dex treatment led to an increase in PTH/PTH-rp receptor mRNA and PTH-induced cAMP accumulation with a peak response at 24 h and this effect was sustained for up to 14 days. In contrast, long-term culture with RA resulted in a reduction in the cAMP response to PTH (Days 7 and 14) with no effect on PTH/PTH-rp receptor mRNA expression. Osteocalcin and Cbfa1 mRNA expression did not alter in the presence of Dex and RA at these time points. This study shows that Dex and RA have differential effects on the expression of the phenotypic markers and genes associated with osteoblast maturation. This homogeneous cell line can therefore be used further to elucidate the cellular and molecular mechanisms of action of Dex and RA at the different developmental stages of human osteoblastic differentiation. This cell line may thus provide a useful species-specific in vitro model for the evaluation of key genes and signalling molecules involved in osteogenesis. This would be of help in the design of 'in vivo' studies.

Adipocytes↗