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At least 19 recordsLinked to original sources
PubMed1991

Neutral lipid synthesis and accumulation during in vitro induction of the lipocyte phenotype in hepatic connective tissue cells.

Connective tissue cells of liver parenchyma are known as hepatic myofibroblasts and lipocytes (fat-storing cells, Ito-cells). They are considered to belong to a single cell lineage, that may switch between these two phenotypes. We have studied cellular and molecular parameters and controls of this switch in the murine GRX cell line, established from liver fibro-granulomatous lesions induced by schistosomal infection. Accumulation of neutral lipids (triacylglycerols, monoalkyl-diacylglycerol, cholesterol) was monitored. It was dependent upon induction with indomethacin. Insulin alone did not induce lipid accumulation in GRX cells, but in cells induced by indomethacin it increased the quantity of stored lipids. We propose that hepatic lipocytes are not cells directly involved in energy storage, but that they represent a particular cell population specialized in storage and in controls of the homoeostasis of lipid-soluble substances at the systemic level.

Animals↗
PubMed1975

[Studies on the number of fat cells and connective tissue cells in white adipose tissue in chronic starvation and after refeeding. I. Investigations on aurothioglucose-obese NMRI-albino-mice(author's transl)].

UNLABELLED: Former investigations (Rakow et al., 1970, 1971 b) on epididymal fat pads of lean NMRI-Albino-mice during starvation and refeeding have shown that the number of fat cells (adipocytes) remained unchanged while the number of cells o connective tissue decreased during starvation and increased during the refeeding period. In the present paper the problem has been investigated whether these variations could be demonstrated also in NMRI-albino-mice obesified by administration of aurothioglucose. MATERIAL AND METHODS: The investigations were performed with male NMRI-Albino-mice rendered obese by administration of aurothioglucose (800 mg per kg body weight). These animals were fed 2.5 g Altromin 1115 R daily for six weeks. After this they were fed Altromin 1115 R and additional oat flakes ad libitum for three (exp. groups HW3) and seven (exp. groups HW 7) days respectively. After this time the animals were sacrificed. The epididymal fat pads were removed and weighed. One of both pads of each animal was used for chemical investigations. After PCA-treatment (0.5 n, 90 degrees C. 15 min.) the DNA (Burton, 1956) and RNA (Ceriotti, 1955) was determined in the supernatant. After NaOH-treatment (0.5 n, 37 degrees C, 24 Hrs) the noncollagen protein content (Lowry et al., 1951) of the sediment was estimated. After HCl-treatment (25%, 110 degrees C, 20 hrs.) the collagen content (Stegemenn, 1958; modified by Rauskolb, 1967) was determined. The remaining fat pad was used for calculations of cell numbers in the fat cell and connective tissue cell compartment. For this reason fat cells were isolated according to Rodbell (1964). The fat cell diameters were determined microscopically and the average masses of the fat cells were estimated. From the wet weight of the fat pads and the average fat cell mass the number of fat cells was calculated. The remaining suspension of fat cells and cells of connective tissue was utilized for cell smears. These smears were stained with Schiff's reagent (Feulgen et al., 1924; Graumann, 1952). With an integrating microdensitometer (Deeley, 1955) the average relative DNA-content of single cell nuclei were measured and the ploidy patterns were estimated. From the whole DNA-content of the fat pads and the DNA-content of the fat cell population the number of cells of the connective tissue was calculated...

Adipose Tissue↗
PubMed1997

Tumor cell and connective tissue cell interactions in human colorectal adenocarcinoma. Transfer of platelet-derived growth factor-AB/BB to stromal cells.

Mechanisms underlying stimulation of platelet-derived growth factor (PDGF) beta-receptors expressed on connective tissue cells in human colorectal adenocarcinoma were investigated in this study. PDGF-AB/BB, but not PDGF receptors, was expressed by tumor cells in situ, as well as in tumor cell isolates of low passage from human colorectal adenocarcinoma. In an experimental co-culture system, conditioned medium from tumor cells only marginally activated PDGF beta-receptors expressed on fibroblasts. In contrast, co-culturing of the two cell types led to a marked PDGF beta-receptor activation. Functional PDGF-AB/BB was found to be associated with heparinase-I-sensitive components on the tumor cell surface. PDGF-AB/BB, isolated from heparinase-I-sensitive cell surface components, induced a marked activation of PDGF beta-receptors. Furthermore, co-culturing tumor cells together with fibroblasts led to a sustained activation of PDGF beta-receptors expressed on fibroblasts. Double immunofluorescence staining of tissue sections from human colorectal adenocarcinoma, combined with computer-aided image analysis, revealed that nonproliferating tumor cells were the predominant cellular source of PDGF-AB/BB in the tumor stroma. In addition, PDGF-AB/BB-expressing tumor cells were found juxtapositioned to microvascular cells expressing activated PDGF beta-receptors. Confocal microscopy revealed a cytoplasmic and cell-membrane-associated expression of PDGF-AB/BB in tumor cells situated in the stroma. In contrast, epithelial cells situated in normal or tumorous acinar structures revealed only a cell-membrane-associated PDGF-AB/BB expression. The is vitro and in situ results demonstrate that tumor cells not only facilitate but also have the ability to modulate connective tissue cell responsiveness to PDGF-AB/BB in a paracrine fashion, through direct cell-cell interactions in human colorectal adenocarcinoma.

Adenocarcinoma↗
PubMed1975

[Studies on the number of fat cells and connective tissue cells in white adipose tissue in chronic starvation and after refeeding. II. Investigations on obese and lean C 57 BL/6 J-mice (author's transl)].

UNLABELLED: Former investigations (Rakow et al., 1970, 1971a, b 1974) have demonstrated a constancy of the adipocyte number in white adipose tissue (parepididymal fat pads) of lean NMRI-albino-mice and aurothioglucose-obese NMRI-albino-mice during starvation and subsequent refeeding. In contrast the number of cells of connective tissue showed great variations under the experimental conditions mentioned above. The present paper describes which changes of the different cell populations within the adipose tissue could be demonstrated in lean and obese C57BL/6 J-mice. MATERIAL AND METHODS: The investigations were performed with obese and lean male C57BL/6 J-mice. The control animal groups were fed for six weeks 2.5 g (lean mice) and 2 g (obese mice), respectively, Altromin 1115R daily (starvation phase). After this time some of these animalwere killed (exp. groups H). The remaining animals now were fed Altromin 1115R and additional oat falkes ad libitum. Three (exp. groups HW3) and seven (exp. groups HW 7) days, respectively, after the beginning of the refeeding phase the animals were killed. After sacrifice the epididymal fat pads were weighed and treated with either (fat extraction). The dry mass was hydrolized with PCA (0.5 m, 90 degrees C, 40 min). In the supernatant the DNA (Burton, 1956), RNA (Ceriotti, 1955) and polysaccharide content (Seifter et al., 1950) were measured. The sediment was hydrolized with NaOH (0.5 n, 37 degrees C, 24 hrs). In this solution the protein content (Lowry et al., 1951) was determined. In addition fat cells were isolated according to Rodbell (1964). The fat cell diameters were determined microscopically and the average masses of the fat cells were estimated. From the wet weight of the fat pads and the average fat cell mass and number of fat cells were calculated. The remaining suspension of fat cells and cells of connective tissue were utilized for cell smears. These cell smears were stained with Schiff's reagent (Feulgen et al., 1924; Graumann, 1953). With an integrating microdensitometer (Deeley, 1955) the average relative DNA-content of single cell nuclei was measured and the ploidy patterns were estimated. The DNA-content was measured chemically according to Burton (1956). From the whole DNA-content of the fat pads and the DNA-content of the fat cell population the number of cells of the connective tissue was calculated...

Adipose Tissue↗
PubMed1995

Complement-dependent induction of DNA synthesis and cell proliferation in human liver connective tissue cells in vitro.

Liver connective tissue cells (LCTC) isolated from patients with fibrotic livers have morphological and biochemical characteristics of myofibroblasts. We have examined the proliferation of LCTC derived from normal livers and from livers with fibrosis of different etiologies, as well as proliferation of skin fibroblasts. We have compared proliferation rates in the presence of fresh human serum and heat-inactivated serum. While skin fibroblast and LCTC from normal liver showed no difference, proliferation of LCTC from fibrotic livers was markedly decreased in the presence of heat-inactivated serum. We demonstrate that the native complement component C1 is a factor involved in the induction of DNA synthesis and proliferation of LCTC isolated from fibrotic livers. We propose that native C1, acting probably in cooperation with other growth factors, is involved in the expansion of connective tissue cells during the development of liver fibrosis.

Blood↗
PubMed1993

Experimental schistosomiasis mansoni: characterization of connective tissue cells in hepatic periovular granulomas.

Connective tissue cells present in periovular granulomas, induced in mice livers by schistosomal infection, were studied in situ and in an in vitro culture after cell migration from explanted granulomas. They were compared to cells of the adjacent hepatic tissue. Connective tissue cells in granulomas and granuloma-derived primary cell lines were characterized as myofibroblasts. The presence of lipid droplets in cells of early granulomas, and comparison with adjacent perisinusoidal cells, indicated their origin through activation and mobilization of lipocytes from the adjacent hepatic tissue. This origin was confirmed in long-standing cultures of granuloma-derived cells, in the stationary phase of growth, in which myofibroblasts could return spontaneously into the fat-storing phenotype.

Animals↗
PubMed1985

Liver connective tissue cells isolated from human schistosomal fibrosis or alcoholic cirrhosis represent a modified phenotype of smooth muscle cells.

Hepatic connective tissue cells associated with schistosomal fibrosis and alcoholic cirrhosis were studied in vitro. Primary cell lines were isolated from all biopsies: they were identified as specific homogeneous cell populations, named liver connective tissue cells (LCTC). They were recognized as analogous to smooth muscle cells, different from true fibroblasts by morphological and physiological criteria. The proliferative capacity of LCTC is directly proportional to the degree of fibrosis in hepatic tissues. LCTC are able to secrete type I, III and IV collagen, fibronectin, laminin and amyloid P component. Their relationship with specific pathology of intrahepatic vascular tree in schistosomiasis is hypothesized.

Amyloid↗
PubMed1994

Myelopoietic competence of stroma composed of hepatic granuloma-derived connective tissue cells or skin fibroblasts.

1. Connective tissue cells isolated from hepatic granulomas (GR cells), induced in mouse liver tissue by schistosomal infection, are able to sustain myelopoiesis, while other connective tissue cells such as skin fibroblasts (SF) are not. 2. We compared the ability of SF and GR cells to sustain in vitro proliferation of the FDC-P1 myeloid cell line, dependent upon IL-3 or GM-CSF. 3. Only the GR stroma sustained the proliferation of co-cultured FDC-P1 cells. RT-PCR analysis showed that both cell lines expressed the message for GM-CSF, but not for IL-3. We showed that GM-CSF was produced by, and remained bound to the cell layer through heparan sulfate; this growth factor could be released by high-salt treatment in a biologically active form from both cell types. The same activity could be restored to NaCl-treated GR cells, but not to SF, by incubation with recombinant murine GM-CSF. 4. These results indicate that the ability of connective tissue cells to sustain myelopoiesis depends directly upon the capacity of their heparan sulfate-bearing molecules to bind and present the GM-CSF to the target cells in a biologically active form. Alternatively, a yet unidentified set of cell layer-associated molecules may be required for the positive or negative control of the membrane-bound GM-CSF.

Animals↗
PubMed2000

Peripheral occluding effects of non-absorbable membranes on ingrowth of cultured gingival connective tissue cells.

BACKGROUND: The success of periodontal regenerative procedures, i.e., using regenerative cells to repopulate wounds, is enhanced by using barrier materials, such as expanded polytetrafluoroethylene (ePTFE) membranes, to provide a barrier to the proliferation of epithelial cells and gingival connective tissue cells at the healing site. However, several animal and clinical studies have demonstrated the difficulties of avoiding thin connective tissue ingrowth under the ePTFE membrane used for bone regeneration procedures. We investigated the peripheral occluding effects of ePTFE membranes on ingrowth of cultured gingival connective tissue cells in vitro. METHODS: The ePTFE membrane was divided into 4 pieces, fixed, and immobilized on a culture dish. Human connective tissue cells from clinically healthy gingiva were isolated and cultured. Low passages (2 through 3) of these cells, 5 x 105, were seeded and cultured in each dish. At weeks 1, 2, and 4, the ingrowth cells under the membranes were stained with Giemsa and photographed. The percentage of cell ingrowth as an area measurement and the cell ingrowth score as a linear measurement were determined using computer-assisted interactive image processing. RESULTS: There were no measurable spaces between the membranes and the dishes at x40 magnification using the stereomicroscope. However, the percentage of cell ingrowth under the membrane gradually increased from 1 to 4 weeks, reaching approximately 70% by week 4. There was a statistically significant difference between the 1 - and 4-week percentage of cell ingrowth (P <0.05). The cell ingrowth score also increased gradually, and cells invaded the center from all peripheral borders. There was a statistically significant difference for the lower right and left margins of the membrane between the 1-week and 4-week cell ingrowth scores. Furthermore, there was a statistically significant difference for the 4-week cell ingrowth score between the upper and lower margins (P <0.05). CONCLUSION: The use of ePTFE membranes placed over the culture dish plate cannot prevent ingrowth of cultured gingival connective tissue cells in vitro.

Adolescent↗
PubMed1990

In vitro induction of the fat-storing phenotype in a liver connective tissue cell line-GRX.

Liver connective tissue cells have been characterized as perisinusoidal myofibroblasts and hepatic lipocytes (Ito cells, fat-storing cells). A concept of a single mesenchymal cell population that may be modulated between these two phenotypes has been postulated. We have previously established a continuous murine cell line, GRX, obtained from fibrotic granulomatous lesions induced by schistosomal infection in mouse liver. This cell line is considered to represent liver myofibroblasts. In the present study we have induced the conversion of these cells into lipocyte (fat storing) phenotype by treatment with insulin and indomethacin. We have quantified the lipid synthesis and the increase of activity of involved enzymes during the induction of the fat-storing phenotype and described modifications of cell organization along this modulation of cell functions.

Animals↗
PubMed1975

A complex junctional system in endothelial and connective tissue cells of the choroid plexus.

Endothelial and connective tissue cells of the choroid plexus have been studied by the freeze-etching technique. The endothelial cells of pre- and postcapillary segments are coupled by a complex junctional system consisting of a combination of tight and gap junctions. Connective tissue cells revealed the same intercellular contacts. Furthermore two different types of gap junctions occurring in membranes of the connective tissue cells are described.

Animals↗
PubMed1993

Smooth muscle myosin regulation by serum and cell density in cultured rat lung connective tissue cells.

RNA and protein analyses were used to detect expression of SM1 and SM2 smooth muscle myosin heavy chain (MHC) in cultured adult rat lung connective tissue cells (RL-90). Smooth muscle MHC mRNA expression in confluent cells grown in 10% serum was approximately 50% of the level in adult stomach. Similar results were obtained in cells cultured at low density (25% confluency) in 1% serum. However, in low-density cultures transferred to 10% serum for 24 h, the level of MHC mRNA decreased to approximately 20% of that in adult stomach. Smooth muscle alpha-actin showed a pattern of expression similar to that for smooth muscle MHC. Expression of nonmuscle MHC-A mRNA was higher in all culture conditions compared to stomach. MHC-A mRNA expression was less in low-density cultures in low serum and increased when low-density cultures were transferred to 10% serum for 24 h. MHC-B mRNA expression was less in low- vs. high-density cultures. In contrast to MHC-A, however, MHC-B mRNA expression in low-density cultures was higher in low serum. Immunofluorescence and immunoblotting with SM1-specific antibody demonstrated the presence of the SM1 protein isoform as well as reactivity to a protein band migrating slightly faster than SM2. These results demonstrate that cultured rat lung connective tissue cells express smooth muscle MHC and that expression is modulated by culture conditions.

Amino Acid Sequence↗