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PubMed1976

Biogenesis of mitochondrial membranes in Neurospora crassa during cellular differentiation: ultrastructural changes accompanying differentiation.

The ultrastructural characteristics of Neurospora cells during dedifferentiation and redifferentiation of conidiospores into vegetative cells have been determined. This germination process occurs between 2 and 5 h after inoculation; by 3-5 h, approximately 50% of the cells have germinated. The cells enter the exponential phase of dry-weight gain between 4 and 5 h after inoculation. Several unusual structures are observed in Neurospora cells during germination. Whorled structures are frequently seen in the cytoplasm during germination, and occasionally at other times. They appear to be derived from the cytoplasmic membrane. Whorled structures of different appearance were observed in the mitochondria between 2 and 4 h after inoculation. Their number was related to the level of metabolizable carbohydrate, and was higher in 15% glucose-than in 2% sucrose-supplemented medium, and very low in medium containing 15% mannitol, or 2% sucrose+13% 2-deoxyglucose, or no added carbohydrate. The mitochondrial inclusions were osmiophilic and could be removed by treatment with 90% aqueous acetone in the cold, indicating that they were composed at least in part of lipid. The strong dependence of the number of mitochondrial inclusions on time and on carbohydrate supplementation, suggests that there is a physiological basis for these structures and that they reflect changes occurring in the mitochondria at times significant to cellular differentiation.

Carbohydrate Metabolism↗

PubMed1991

Differential effects of insulin-like growth factors I and II on growth, differentiation and glucoregulation in differentiating chondrocyte cells in culture.

Insulin-like growth factors I and II have been shown differentially to affect the growth and carbohydrate metabolism of differentiating cartilage developed from mouse embryonic limb buds in organ culture. To gain insight into the relative importance of IGF-I and II actions in different stages of development of cartilage we have established a primary culture of differentiating chondrocytes from mouse embryonic limb buds. Trypsin digested limb bud cells from 9-11 day old mouse embryos differentiated into chondrocytes by 5-7 days in culture. At all stages of differentiation, distinct receptors of IGF-I and II were observed. IGF-I stimulated growth and sulphate incorporation of the non-differentiated and differentiated chondrocytes. IGF-II stimulated growth of the non-differentiated cells and had no effect on growth or sulphate incorporation by the differentiated cells. IGF-II, however, stimulated the glucose uptake by the cells at all stages of differentiation. These data confirm our previous suggestion that IGF-I in cartilage is the regulator of growth and differentiation, while IGF-II may be an important regulator of glucose metabolism in the tissue.

Animals↗

PubMed1991

Differential regulation of c-myc and transforming growth factor-alpha messenger RNA expression in poorly differentiated and well-differentiated colon carcinoma cells during the establishment of a quiescent state.

A previous report from this laboratory indicated that a transformed fibroblast cell line up-regulated c-myc by as much as 14-fold as cultures approached saturating densities, whereas the untransformed counterparts displayed little alteration in c-myc expression (Cancer Res., 49: 2320, 1989). The results suggested a mechanism for the growth advantage of the transformed cells at postconfluent densities. Similarly, the present results indicate that regulation of c-myc expression during establishment of a quiescent state markedly differed in poorly differentiated versus well-differentiated human colon carcinoma cells. While c-myc expression increased 2- to 3-fold during this period in the poorly differentiated cells, expression levels for this protooncogene showed little variation in the well-differentiated cells. There was, however, no correlation between degree of differentiation and c-myc mRNA levels in growing cultures (i.e., cells in late log phase). Another proliferation-associated mRNA, transforming growth factor alpha (TGF-alpha), was also differentially regulated in the two groups of colon carcinoma cells as cultures approached quiescence. Further, addition of exogenous growth-stimulatory factors (epidermal growth factor plus insulin plus transferrin) to quiescent, well-differentiated cells resulted in an up-regulation of TGF-alpha mRNA levels by 9-fold over a 24-h period. In contrast, poorly differentiated cells displayed little alteration in TGF-alpha mRNA levels under similar conditions. The results suggest that inappropriate kinetic regulation of c-myc and TGF-alpha mRNAs at quiescence may be related to the growth factor independence of the poorly differentiated colon carcinoma cells. Furthermore, altered temporal regulation of c-myc and TGF-alpha expression appears to be more relevant to differentiation status in human colon carcinoma cells than are absolute expression levels.

Carcinoma↗

PubMed1988

Lymphokine-induction of memory B-cell differentiation: differential stimulation of large virgin and memory B-cell differentiation.

In order to compare and contrast the requirements of virgin and memory B cells for B-cell differentiation factors, a model system was developed in which low-density rat B cells isolated from 4-week primed antigen-draining lymph nodes were cultured in vitro. This large low-density cell population contained B cells which were 90% surface IgM positive and 60% IgD positive and showed moderately elevated Ia staining. When the cell population was stimulated with antigen plus lymphokines or lymphokines alone, antigen-specific IgG antibody was secreted; this was used as a measure of memory cell differentiation. When the cell population was stimulated with mitogen (lipopolysaccharide plus dextran sulfate) plus lymphokines, polyclonal IgG and IgM secretion was seen and was used as a measure of virgin B-cell differentiation. Using this system, we found that lymphokines contained in a Con A-induced rat spleen cell supernatant (CSN) were sufficient to drive both memory and virgin B-cell differentiation. In contrast, lymphokines contained in the supernatant from the murine T-cell hybridoma B151K12 (B151CFS) were able to induce large amounts of polyclonal IgM and IgG secretion but did not support memory B-cell differentiation. When recombinant human IL-2 was added to these cultures, it acted synergistically to augment virgin B-cell differentiation, but this combination of lymphokines was still not able to support memory B-cell differentiation. Furthermore, recombinant rat interferon-gamma and a commercial source of human BCGF, with or without IL-2, were unable to promote significant virgin or memory B-cell differentiation. These data support the hypothesis that memory B cells and virgin B cells differ in their lymphokine requirements for differentiation into antibody-secreting cells.

Animals↗

PubMed1992

Ultrastructural analysis of differentiation of rat endoderm in vitro. Adipose vascular-stromal cells induce endoderm differentiation, which in turn induces differentiation of the vascular-stromal cells into chondrocytes.

Isolated definitive endoderm from 9-day-old rat embryos was cultivated up to 24 days in plastic and glass petri dishes and on developing vascular-stromal cells (mesenchymal cells) from epididymal white and interscapular brown adipose tissue of 4-week-old male rats. Explants were analyzed histologically and ultrastructurally. Endoderm attached to the bottom of the glass or petri dishes degenerated under one week of cultivation. Endoderm free floating in the culture medium developed into unilaminar vesicles whose flat epithelium did not differentiate. However, endoderm inoculated on developing mesenchymal cells differentiated into glandular explants or into ciliated pseudostratified columnar respiratory epithelium. The glandular explants were made up of at least four different kinds of cells whose cytoplasm showed predominantly: a) polyribosomes, b) lysosomes, c) mitochondria or d) cytoskeletal filaments. Endodermal cells differentiated only if, during cultivation, they were in contact with or in close proximity to developing mesenchymal cells. Endoderm differentiating into the respiratory epithelium in turn directed differentiation of the underlying vascular-stromal cells into lamina propria cells and chondrocytes. Cultivated vascular-stromal cells in the upper layers became thicker, ellipsoid in shape and with enlarged intercellular space. They appeared to be lamina propria cells and, together with the respiratory epithelium, built folds of respiratory mucosa. The vascular-stromal cells in the layers close to the bottom developed into chondrocytes; i.e., the cells became oval and agglomerated in nest like structures with a defined extracellular matrix. Their cytoplasm contained abundant cisternae of rough endoplasmic reticulum and numerous vacuoles with PAS positive substance. These observations showed that even developing vascular-stromal cells from adipose tissue from postlactating rats can trigger the process of definitive endoderm differentiation. Once triggered, differentiating endoderm influenced differentiation of the vascular-stromal cells into the cells and tissues of a wall of the respiratory tract.

Adipose Tissue↗

PubMed1987

Enhanced c-fos expression in differentiated monomyelocytic cells is associated with differentiation and not with the position of the differentiated cells in the cell cycle.

Enhanced expression of the proto-oncogene c-fos is reported to be involved in the differentiation of monomyelocytic cells into mature macrophages. Such differentiated cells usually accumulate in the G1 phase of the cell cycle. M1 murine myeloid leukemia cells, which can be synchronized in early and late G1 and can also differentiate into mature macrophages when stimulated with granulocyte colony-stimulating factor (G-CSF), were used to investigate whether the enhanced expression of c-fos in differentiated monomyelocytic cells is associated with the position of the cells in the cell cycle or with their state of differentiation. Our data show that the enhanced expression of the c-fos gene occurs only in fully differentiated cells and not in proliferating or G1-arrested cells. These data imply that the enhanced expression of c-fos in M1 cells is restricted to functionally differentiated cells and not related to the position of the differentiated cells in the cell cycle.

Animals↗

PubMed1979

[Factors that control the differentiation of stem cells. I. The change in direction of hematopoietic stem cell differentiation under the effect of differentiating T-lymphocytes].

A mixed transplantation of bone marrow cells, and lymph nodes or thymic cells of mice CBA strain into lethally irradiated hybrid recipients (CBAXC57B1)F1 is accompanied with changes in the differentiation pattern from a mainly erythroid to a mainly granuloid way. Thymectomy of either donor of bone marrow cells or recipients, or both, destroys the stem cell differentiation in the direction of granulopoieseis. Intact syngeneic lymphocytes normalize differentiation of the stem cells, but in the presence of tissue antigens these provide for the stem cell differentiation mainly in the direction of granulopoiesis. The differentiation of stem haemopoietic cells is accomplished under the thymic and lymphocyte control. T-differentiating lymphocytes (Td) are the lymphocytes controlling the stem cell differentiation.

Animals↗

PubMed1985

Quantification of thyroglobulin messenger RNA by in situ hybridization in differentiated thyroid cancers. Difference between well-differentiated and moderately differentiated histologic types.

Thyroglobulin messenger RNA (mRNA) was located and quantified in tissue sections of differentiated human thyroid cancers by in situ hybridization using cloned complementary DNA probes. The cells of the well-differentiated follicular and papillary forms contained similar levels of thyroglobulin mRNA, corresponding to about 2000 copies per cell. In contrast, cells of moderately differentiated thyroid cancers contained about two to three times less thyroglobulin mRNA. It was also found that thyroglobulin mRNA was present almost exclusively in polyribosomes under the form of heavy polyribosomes actively synthesizing thyroglobulin. It is suggested that in situ hybridization method allows localization of specific mRNA in differentiated thyroid cancers and correlation with the level of differentiation of the cells.

Autoradiography↗

PubMed1987

Relationship between differentiation and terminal mitosis: chick sensory and ciliary neurons differentiate after terminal mitosis of precursor cells, whereas sympathetic neurons continue to divide after differentiation.

A population of undifferentiated cells has been characterized during the early development of nodose and ciliary ganglia. This population is defined by the absence of surface markers specific for neurons (tetanus toxin receptor, Q211 antigen) and for glial cells (O4 antigen). These undifferentiated cell populations were isolated from the ganglia and were shown to contain neuronal precursor cells that were able to differentiate in vitro into neurons, as characterized by morphology and surface antigens. Undifferentiated cells were detected during the period of neuronal birth, indicating that dividing neuronal precursor cells do not express neuron-specific surface markers. This was directly shown by 3H-thymidine-labeling studies using nodose ganglia, ciliary ganglia, and dorsal root ganglia. In sympathetic ganglia, however, no undifferentiated neuronal precursor cells were detectable at developmental stages when sympathetic neurons are born. 3H-Thymidine injected during that stage at E7 was incorporated into cells expressing the neuronal markers tetanus toxin receptor and Q211 antigen. Quantitative fluorimetric determination of the DNA content of dissociated sympathetic ganglion cells demonstrated the presence of a population of Q211-positive sympathetic ganglion cells in the G2 phase of the cell cycle. E7 sympathetic ganglion cells expressing neuronal surface markers were also shown to be able to divide in vitro. We have concluded that the relationship between terminal mitosis and the onset of differentiation differs between ganglia of the chick peripheral nervous system: Sympathetic ganglion cells continue to divide after the acquisition of neuronal properties, whereas neuronal precursor cells from other autonomic and sensory ganglia start to differentiate after a terminal mitosis.

Animals↗

PubMed1985

Human lymphocyte differentiation antigens HB-10 and HB-11. II. Differential production of B cell growth and differentiation factors by distinct helper T cell subpopulations.

Two monoclonal antibodies (HB-10 and HB-11), which react with human T, B, and NK cells, identify approximately 50% of the Leu-3+ T helper (TH) cells in adult blood. In the present studies, the functional capabilities of the HB-11+ and HB-11-TH cell subpopulations were examined after purification by fluorescence-activated cell sorting. Both subpopulations proliferated in response to PHA, Con A, PWM, and OKT-3 antibodies. The HB-11+ TH cells gave a minimal proliferative response to soluble tetanus toxoid antigen, whereas HB-11-TH cells responded well. After mitogen activation, both HB-11+ and HB-11-TH cells and to produce soluble factors which induce large B cells to proliferate. However, PWM-stimulated HB-11+TH cells were incapable of inducing B cells to differentiate into antibody-secreting plasma cells, whereas HB-11-TH cells were efficient in this regard. The results suggest that the HB-11 antigen is expressed on a subpopulation of virgin TH cells that can produce B cell growth factors but are deficient in the ability to produce B cell differentiation factors.

Antibodies, Monoclonal↗

PubMed1992

TGF-beta blocks early but not late differentiation-specific gene expression and morphologic differentiation of 3T3 T proadipocytes.

Transforming growth factor-beta (TGF-beta) inhibits morphologic differentiation of BALB/c 3T3 T cells as well as other proadipocyte models. Our prior studies suggested that TGF-beta may act only during the early stages of differentiation induction. However, we did not determine whether TGF-beta was differentially effecting expression of any of the various differentiation-specific genes or if it could cause down-regulation of these genes in differentiated cells. Therefore, in the current study we tested the effects of exogenous TGF-beta (0.01-5.0 ng/ml) on morphologic differentiation and on differentiation-dependent gene expression (Northern and slot blot analyses) at various times during differentiation. When induced to differentiate, 3T3 T cells first undergo predifferentiation growth arrest and from this state molecular, biochemical, and morphological differentiation proceeds. Here it was found that when added prior to the onset of differentiation, TGF-beta was a potent inhibitor or morphologic differentiation as well as of the expression of differentiation-specific genes such as lipoprotein lipase (LPL) and glycerol-3-phosphate dehydrogenase (GPD). However, once morphologic differentiation began, TGF-beta was ineffective in blocking differentiation. In addition, exposure of fully differentiated cells to TGF-beta for up to 72 hours caused no decrease of differentiation-specific genes and even a 7-day treatment caused no morphologic dedifferentiation. Tumor necrosis factor also had no detectable effect on fully differentiated cells.

3T3 Cells↗

PubMed1986

Hematopoietic growth and differentiation factors and the reversibility of malignancy: cell differentiation and by-passing of genetic defects in leukemia.

Our development of systems for the in vitro cloning and clonal differentiation of normal hematopoietic cells made it possible to identify: the factors that regulate growth and differentiation of these normal cells; the changes in the normal development program that result in leukemia, and how to reverse malignancy in leukemic cells. I have mainly used myeloid cells as a model system. Normal hematopoietic cells require different proteins to induce growth (growth factors) and differentiation (differentiation factors). There is a multigene family for these factors. Identification of these factors and their interaction has shown how growth and differentiation can be normally coupled. The development of leukemia involves the uncoupling of growth and differentiation. This can occur by changing the requirement for growth without blocking cell response to the normal inducers of differentiation. Addition of normal differentiation factors to these malignant cells still induces their normal differentiation, and the mature cells are then no longer malignant. Genetic changes which inhibit differentiation by normal differentiation factors can occur in the progression of leukemia, but even these leukemic cells may still be induced to differentiate by other compounds, including low doses of compounds now being used in cancer therapy, that can induce differentiation by alternative pathways. The differentiation of leukemic to mature cells results in the reversion of malignancy by by-passing genetic changes that produce the malignant phenotype. We have obtained this differentiation of leukemic cells in vitro and in vivo, and by-passing genetic defects by inducing differentiation can be a useful approach to therapy.

Cell Differentiation↗

PubMed1990

Effects of 1,25-dihydroxyvitamin D3 and its analogs on butyrate-induced differentiation of HT-29 human colonic carcinoma cells and on the reversal of the differentiated phenotype.

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) greatly enhances sodium butyrate (NaB)-induced enterocyte differentiation of HT-29 human colonic carcinoma cells while 1,25-(OH)2D3 alone induces growth restriction without associated differentiation. In the present study, the efficacies of various analogs of 1,25-(OH)2D3 to enhance NaB-induced HT-29 differentiation and to prolong the reversal of the differentiated phenotype under NaB-free growth conditions were subsequently examined. Extent of HT-29 differentiation was assessed by measurement of alkaline phosphatase (AP) activity, appearance of mucin-producing cells, changes in morphological characteristics, and expression of differentiation-associated cytokeratin proteins. Among active analogs of 1,25-(OH)2D3, 26,26,26,27,27,27-hexafluoro-1,25-(OH)2D3 (F6-1,25-(OH)2D3), 24,24-difluoro-24-homo-1,25-(OH)2D3, and 26,27-dimethyl-1,25-(OH)2D3 were 100-, 10-, and 5-fold, respectively, more effective than 1,25-(OH)2D3 in enhancing NaB-induced mucin production. Combined use of NaB and F6-1,25-(OH)2D3 (10(-9) M) also induced HT-29 cells to form highly differentiated goblet-like enterocytes, and increased both cellular AP enzymatic activity and tissue-type cytokeratin content. This differentiated state was qualitatively more advanced than that achieved by a combination of NaB and 10(-7) M 1,25-(OH)2D3. NaB-mediated HT-29 differentiation (in short-term inductions) was found to be reversible following a return to NaB-free medium. HT-29 cells differentiated by combined use of NaB and 1,25-(OH)2D3 or its analogs exhibited a significant prolonged reversal time relative to cells differentiated with NaB alone. The most prominent effect was achieved using cells differentiated with NaB and 10(-9) M F6-1,25-(OH)2D3 which exhibited a 7-fold prolonged reversal time over colonocytes differentiated by NaB alone. Our data suggest that a combined use of NaB and 1,25-(OH)2D3 or its derivatives may provide a convenient in vitro model system to probe molecular events associated with steroid-target tissue interactions in a differentiating cell system as commonly occurs in vivo. Such an analysis might lend itself to design of a rational combination differentiation-based therapy for the clinical management of colon cancer.

Butyrates↗

PubMed1987

Poorly differentiated human gastric carcinoma is more sensitive to antitumor drugs than is well differentiated carcinoma.

The chemosensitivities of 41 poorly differentiated gastric cancer tissues were compared with that of 16 well differentiated tissues, using the in vitro succinate dehydrogenase inhibition test. These human tissues obtained at the time of surgery were exposed to six different antitumor drugs: carboquone (CQ), adriamycin (ADM), mitomycin C (MMC), aclacinomycin A (ACR), cisplatin (DDP) and 5-fluorouracil (5-FU). The chemosensitivity was determined as positive when the succinate dehydrogenase (SD) activity of the drug exposed cells was decreased to below 50% of that of control cells, on day 3 of exposure. Decrease in SD activity was remarkable in the poorly differentiated tissues, compared to the well differentiated tissues, exposed to ADM, MMC, DDP and 5-FU. The sensitive rates were higher in the poorly differentiated tissues than in the well differentiated tissues, against all six antitumor drugs. Sixty-three per cent of the poorly differentiated tissues were sensitive to more than three antitumor drugs, in an identical tissue, but the rate was only 19% in the well differentiated tissues. The resistant rates to all drugs tested were 20% in the poorly differentiated and 31% in the well differentiated tissues. This would indicate that patients with a poorly differentiated gastric cancer will probably show a better response to antitumor drugs, compared to those with a well differentiated type.

Aclarubicin↗

PubMed1989

Human B cell differentiation by Fc fragment. III. Effect of IL-1 and IL-2 on differentiation of human B lymphocytes induced by Fc fragments of human IgG.

The human Fc fragment of IgG, when added to blood mononuclear cells in vitro, induces B cell differentiation after 6 days of culture. This activity requires the presence of T cells and monocytes. This work explores the roles of interleukin 1 (IL-1) and interleukin 2 (IL-2) in B cell differentiation induced by Fc fragments. Peripheral blood mononuclear cells (PBMC) from normal donors were examined for plasma cell differentiation following stimulation with Fc fragment (15 and 30 micrograms/ml) with or without IL-1 (6 U/ml) or IL-2 (2 U/ml). Results indicate that both IL-1 and IL-2 accelerated B cell differentiation by the Fc fragment to 3 days of culture, compared to 6 days required with the Fc fragment alone. The time required for differentiation was not further shortened when both IL-1 and IL-2 were present in culture; both IL-1 and IL-2 were able to partially induce B differentiation alone at 6 days of culture. The importance of IL-2 in B cell differentiation was further supported by the finding that antibodies specific for the IL-2 receptor blocked B cell differentiation induced by Fc fragments, with or without additional IL-1 or IL-2. The depletion of monocytes also blocked B cell differentiation and the requirement for monocytes could not be replaced by exogenous IL-1; however, Fc fragments were shown to induce monocytes to secrete IL-1 beta after 24 hr in culture. These results suggest that accelerated differentiation of B cells into plasma cells requires a double signal provided by Fc fragments and IL-1 or IL-2. Monocytes are necessary for Fc fragment-induced differentiation and cannot be replaced by either IL-1 or IL-2.

Adult↗

PubMed1985

Control of HL-60 myeloid differentiation. Evidence of uncoupled growth and differentiation control, S-phase specificity, and two-step regulation.

Myeloid differentiation of HL-60 human promyelocytic leukemia cells was studied during DMSO-induced differentiation. G 1/0-specific growth arrest could occur without the usual associated subsequent phenotypic differentiation into mature myeloid cells, suggesting that growth arrest and phenotypic differentiation are separately regulated. In the course of differentiating, the cells achieved a semi-stable intermediate state where they had a labile, pre-commitment memory of exposure to inducer, but were not yet committed to differentiation. This state was associated with a nuclear structural change previously found to be associated with the precommitment memory state. The process of differentiation could thus be resolved into two steps, early events up through development of pre-commitment memory and late events subsequents to pre-commitment memory. The kinetics of terminal cell differentiation indicated that the cellular regulatory event initiating a program of differentiation in response to inducer was S phase-specific. A comparison of the present results for DSMO to previous results for retinoic acid (RA)-induced HL-60 myeloid differentiation showed that the two inducers effect different cellular pathways for differentiation of HL-60 cells to mature myeloid cells, but with certain common features including the above S-phase specificity and pre-commitment memory.

Cell Cycle↗

PubMed1990

Adenovirus infection of differentiated F9 cells results in a global shut-off of differentiation-induced gene expression.

Previous experiments have demonstrated a link between transcriptional regulatory mechanisms acting during F9 cell differentiation and transcription control by the adenovirus E1A gene. We have isolated a number of differentiation-specific genes by cDNA cloning to determine if E1A exerts a coordinated control over differentiation specific gene expression. The mRNAs encoded by these cDNAs were undetectable or only barely detectable in undifferentiated cells but then rose in concentration upon differentiation. Analysis of transcription rates in isolated nuclei revealed that all but one of the genes was transcriptionally regulated during differentiation. Interestingly, alpha 2-type IV collagen expression was activated by a post-transcriptional mechanism since the gene was transcribed in both undifferentiated and differentiated cells whereas the cytoplasmic mRNA was undetectable in undifferentiated cells but rose in abundance in parallel with other regulated transcripts. Adenovirus infection of differentiated F9 cells reduced the cytoplasmic mRNA levels of each of the differentiation specific genes to near that found in the undifferentiated cell. Of those genes that were transcriptionally activated by differentiation, adenovirus infection specifically inhibited transcription. In contrast, although the alpha 2 collagen mRNA levels were reduced by adenovirus infection similar to the other mRNAs, the control was post-transcriptional since transcription of the gene was unaffected. Thus, the mechanism for loss of gene expression mediated by E1A reflects the mechanism by which the gene was activated during differentiation. Based on these results we suggest that E1A controls the expression of the F9 cell phenotype by targeting a regulatory activity acting early in the differentiation program.

Adenoviruses, Human↗

PubMed1992

Paracrine regulation of adipose differentiation by arachidonate metabolites: prostaglandin F2 alpha inhibits early and late markers of differentiation in the adipogenic cell line 1246.

The effect of arachidonate metabolites on the differentiation of the adipogenic cell line 1246 was investigated. Among the metabolites examined, only prostaglandin F2 alpha (PGF2 alpha) inhibited differentiation in a dose-dependent fashion with an ED50 of 3 x 10(-9) M. PGF2 alpha inhibited the mRNA expression of lipoprotein lipase, clone 154, and fatty acid-binding protein, which are early markers of differentiation, as well as glycerol-3-phosphate dehydrogenase specific activity and triglyceride accumulation, which are late markers of differentiation. Chronic exposure of 1246 cells to PGF2 alpha before and during differentiation indicated that the cells that have just initiated their differentiation program were the most susceptible to the inhibitory effect of PGF2 alpha. Since 1246 cells produce PGs, we determined whether the PG produced by the cells influenced adipose differentiation. Cyclooxygenase inhibitors added to the culture medium stimulated differentiation of 1246 cells up to 18-fold depending on the type and concentration of inhibitor used. In contrast, lipoxygenase inhibitors had no effect. Treatment of 1246 cells with arachidonic acid resulted in a dose-dependent inhibition of cell differentiation. Oleate or linoleate had no effect. These data indicate that PGF2 alpha inhibits early and late events of adipose differentiation and that the endogenous production of PGs (particularly PGF2 alpha) plays an important role as a negative paracrine or autocrine regulatory pathway of adipose differentiation.

Adipose Tissue↗