Biomedical subjects

P Simon-Assmann

Publications and source records attributed to P Simon-Assmann.

53 records · Page 3Linked to original sources

PubMed1989

Glycosaminoglycan expression in intestinal epithelial skin-fibroblastic cell cocultures. Fibroblastic cell-mediated effects of glucocorticoids.

The nature and distribution of newly synthesized glycosaminoglycans (GAGs) were studied in foetal rat skin fibroblasts, in rat intestinal endodermal cells and in cocultures of both cell types. The data show that fibroblasts synthesize and secrete hyaluronic acid (HA), heparan sulphate (HS) and chondroitin sulphate molecules (CS). Our data focus on HA, which is found as two different molecular forms, the smallest hydrodynamic-sized species being mostly recovered within the cell or associated with the cell surface, and the largest one secreted into the medium, whatever the cell type. Endodermal cells synthesize only two types of GAGs: the low molecular weight form of HA and HS. Cocultures of rat intestinal endodermal and skin fibroblastic cells in the presence of dexamethasone (Dx), allow optimal epithelial cytodifferentiation (Kedinger et al. 1987a). The main changes in the GAGs synthesized under these conditions as compared to skin fibroblastic cell cultures concern: (1) the enhancement of the lowest molecular weight form of HA to the detriment of the highest form in the cellular, pericellular and extracellular compartments; (2) the increase in the proportion of HS molecules associated with the cell surface. Interestingly, similar modifications are obtained by addition of Dx to the skin fibroblastic cell cultures. The data are discussed with reference to the constitution of a basement membrane at the epithelial-fibroblast interface in the cocultures, to the fibroblastic-dependent induction of epithelial differentiation and to the glucocorticoid response.

Animals↗

PubMed1988

Epithelial-mesenchymal interactions in the production of basement membrane components in the gut.

The production and deposition of extracellular matrix proteins and the cellular origin of type-IV collagen have been analysed immunocytochemically in cocultured or transplanted intestinal epithelial-mesenchymal cell associations. In the first experimental model, rat intestinal endodermal cells were cultured on top of confluent mono-layers of rat intestinal or skin fibroblastic cells. Under these conditions, interstitial matrix and basement membrane proteins were deposited within the fibroblastic layer over the whole culture period; interactions between the epithelial cells and the fibroblastic cell population, whatever their organ of origin, were required for the production of the basement membrane. In addition, its formation was progressive as assessed by the shift of a spot-like labelling to a continuous linear pattern at the epithelial-mesenchymal interface, and paralleled epithelial cell differentiation. In the second experimental model, chick-rat epithelial-mesenchymal recombinants developed as intracoelomic grafts were used, and the immunocytochemical detection of a basement membrane protein, type-IV collagen, was performed with species-specific antibodies. The major role of the mesenchyme in the deposition of type-IV collagen is supported by the fact that anti-chick but not anti-mammalian antibodies stained this antigen in chick mesenchyme-rat endoderm recombinants. These observations emphasize the role of tissue interactions in the formation of a basement membrane and show that the mesenchymal compartment is the principal endogenous source of type-IV collagen.

Animals↗

PubMed1988

Epithelial-mesenchymal interactions in intestinal epithelial differentiation.

The complex morphogenetic events and the concomitant structural and functional differentiation of intestinal progenitor cells are dependent on tissue interactions. Several experimental models of hetero-species or -topic recombinants between epithelial and mesenchymal anlagen are described. They enabled us to elucidate the respective roles of these tissue components in morphogenesis, epithelial differentiation, and hormone-elicited responses. Among the mechanisms of tissue interactions, the possible mediation of permissive and instructive information via the extracellular matrix is postulated. Arguments in favor of this are provided by the observation of compositional changes in matrix molecules during intestinal development and differentiation. On the other hand, in vitro experimental data emphasize the role of actual contacts between epithelial and mesenchymal cell populations and the importance of the mesenchyme for basement membrane formation.

Animals↗

PubMed1987

Synthesis of glycosaminoglycans by undifferentiated and differentiated HT29 human colonic cancer cells.

Among the extracellular matrix components which have been suggested to be involved in developmental and neoplastic changes are glycosaminoglycans (GAGs). To try to correlate their amount and nature with the process of enterocytic differentiation, we studied glycosaminoglycan synthesis of human colonic adenocarcinoma cells (HT29 cell line) by [3H]glucosamine and [35S]sulfate incorporation. Enterocytic differentiation of the cells obtained in a sugar-free medium (for review, see A. Zweibaum et al. In: Handbook of Physiology. Intestinal Transport of the Gastrointestinal System, in press, 1987) resulted in a marked increase in total incorporation of labeled precursors (20-fold for [3H]glucosamine, 4.5-fold for [35S]sulfate) as well as in uronic acid content (5-fold); most of the synthesized GAGs were found associated with the cell pellet. Chromatographic and electrophoretic analysis of the labeled GAGs revealed that undifferentiated cells synthesized and secreted hyaluronic acid, heparan sulfate, and one class of chondroitin sulfate. Differentiation of HT29 cells because associated with the synthesis of an additional class of chondroitin sulfate (CS4) concomitant to a decrease in heparan sulfate which is no longer found secreted in the medium. Furthermore, the charge density of this latter GAG component varied as assessed by a shift of its affinity on ion-exchange chromatography.

Adenocarcinoma↗

PubMed1987

Importance of a fibroblastic support for in vitro differentiation of intestinal endodermal cells and for their response to glucocorticoids.

Microexplants of 14- or 15-day-old fetal rat intestinal endoderm, separated from mesenchyme by collagenase, were placed on culture dishes coated with different extracellular matrix components or on confluent monolayers of intestinal mesenchymal cells or of fetal skin fibroblasts. Only small variations in the attachment or spreading of the endodermal cells could be observed when they were cultured on the different acellular substrata, and their survival never exceeded one week. When cocultured with intestinal or skin fibroblasts, endodermal cells proliferated and the survival time was prolonged to 2 or 3 weeks. Furthermore, differentiation, as assessed by the polarization of the cells, occurred and was characterized by the maturation of apical brush borders and by the synthesis of microvillar digestive enzymes visualized immunocytochemically with monoclonal antibodies. Glucocorticoids accelerated structural differentiation and stimulated or induced brush border enzymes only in the coculture conditions. These experiments emphasize the role of a fibroblastic support without tissue specificity on the cytodifferentiation of intestinal endodermal cells. They also suggest a mesenchymal dependence on the hormonal response.

Animals↗

PubMed1987

Intestinal tissue and cell cultures.

The culture of animal cells and tissues is a widely used technique in the field of cellular and molecular biology; one of the most interesting aspect being linked to the study of the mechanisms of cell differentiation. In the specific case of intestinal epithelial cells, various tissue culture technologies have proved to be important tools for the study of precise facets related to intestinal function, pathology and differentiation. Concerning this latter aspect, organ culture experiments have brought about interesting data on the hormonal or nutritional control of intestinal maturation. Nevertheless, the study of the precise mechanisms underlying epithelial proliferation and/or differentiation at the cellular level needs more adequate cell culture model systems. One of them has been described for two cell lines derived from human colonic adenocarcinomas, in which the cells can be induced to achieve enterocytic-like differentiation. Up to date, none of the continuous cell lines starting from normal undifferentiated cells have allowed generation of morphological or functional enterocytic polarity. In contrast, primary cell cultures which allow maintenance of a more physiological environment for the epithelial cells like contacts with their in vivo counterparts, mesenchymal cells or extracellular matrix molecules, have proved to be promising approaches.

Animals↗

PubMed1987

Growth and differentiation of intestinal endodermal cells in a coculture system.

To investigate the role of epithelial-mesenchymal interactions on intestinal maturation, we cultured embryonic epithelial cells in several experimental conditions. Microexplants of 14-15 days fetal rat intestinal endoderm, separated from the mesenchyme by collagenase, were seeded on dishes coated with different extracellular matrix components (collagens I, III, IV, fibronectin, laminin) or on confluent monolayers of intestinal mesenchymal cells or of fetal skin fibroblasts. Only small variations in the attachment or spreading of the endodermal cells could be observed when they were cultured on the different substrata and their survival never exceeded one week. When cocultured with intestinal or skin fibroblasts, however, endodermal cells grew, formed a monolayer, survival time was prolonged up to two to three weeks, and differentiation occurred. This differentiation was assessed by cell polarisation, morphological maturation of apical brush borders, synthesis of microvillar digestive enzymes and of extracellular matrix molecules seen immunocytochemically. Finally, glucocorticoids which are known to stimulate or induce brush border enzymes, accelerated the morphological and enzymatic maturation only in the cocultures.

Animals↗

PubMed1986

Maturation of brush border hydrolases in human fetal intestine maintained in organ culture.

This investigation was undertaken to study the effects of hormones, sugars and amniotic fluid on the maturation of brush border enzymes in the human fetal intestine, at early stages of gestation. Intestinal explants from 8-13-weeks fetuses were maintained in organ culture for 3 days in the presence of the agents to be tested. The data show that the explanation of human fetal gut in a serum free culture medium elicits a significant maturation (2-4-fold increase above preculture levels) of lactase and aminopeptidase whatever the gestational stage studied and of sucrase and alkaline phosphatase at specific stages of development. To be expressed, the overall maturation needs the presence of sugar (in particular glucose) in the culture medium. The addition of dexamethasone, insulin or amniotic fluid to the medium did not further enhance brush border enzyme activities except for lactase whose levels were doubled by the dexamethasone. The present data suggest that in addition to the differences which exist among mammalian species in the timing of enzyme development, there may be a species specificity in the factors involved in fetal enzymatic maturation.

Alkaline Phosphatase↗

PubMed1986

Immunocytochemical localization of extracellular-matrix proteins in relation to rat intestinal morphogenesis.

Various extracellular-matrix proteins were detected by indirect immunofluorescence in rat intestine at various stages of development ranging from 14 days of gestation to the adult stage. At the earliest stage studied, laminin, nidogen and type-IV collagen were present at the epithelial/mesenchymal interface, whereas fibronectin and type-III procollagen were found throughout the whole mesenchyme. We were able to relate some changes in the staining patterns of extracellular-matrix proteins to morphogenetic processes. As early as 15 days of gestation, i.e. before villus formation, modifications in the distribution or in the staining intensity of all of the antigens within the mesenchyme paralleled the orientation and segregation of mesenchymal cells in the region surrounding the basal membrane and in the presumptive peripheral muscular layers. During villus outgrowth, the transient disappearance of fibronectin and particularly type-III procollagen from the top of the protruding villus core was evident. During the perinatal period, i.e. when crypts develop, the linear staining for the basal-membrane proteins became restricted to the base of the villi, their labelling along the remaining portion of the villi being more irregular. In mature rat intestine, no major modifications in matrix proteins along the crypt-villus axis in relation to epithelial differentiation were found, except that the labelling for fibronectin and type-III procollagen, which are at this stage more closely related to the basement membrane, was less pronounced in the upper part of villi.

Animals↗

PubMed1986

[Development of the digestive function: regulation of the maturation of intestinal brush border enzymes].

During the suckling period in mammals, the immaturity of the digestive function as well as several functional pecularities lead the gastrointestinal physiology to adapt to milk digestion and absorption. The dietary transition which occurs at weaning is accompanied by wide modifications as neonatal properties are lost and mature digestive functions are acquired. The involvement of factors like tissue interaction, hormones and nutritional substrates in the onset and subsequent maturation of intestinal brush border hydrolases is discussed.

Alkaline Phosphatase↗

PubMed1985

Enzymatic response to glucocorticoids of the chick intestinal endoderm associated with various mesenchymal cell types.

The aim of the present study was to test the morphological and functional maturation of recombinants composed of chick intestinal endoderms associated to different mesenchymal supports and their enzymatic response to glucocorticoids. For this purpose 5.5-day chick embryonic intestinal endoderm has been associated to 14-day fetal rat gut mesenchyme, to rat intestinal fibroblasts (6-day neonatal rat intramucosal fibroblasts) or to rat control fibroblasts, originating from 20-day fetal rat skin and lung and from 6-day neonatal rat intestinal muscle. The recombinants were grown as intracoelomic grafts either for 12 days or for 10 days plus 2 days in organ culture in the presence of dexamethasone. The data show that heterospecific recombinants achieve subnormal morphogenesis and enzymatic maturation. The organ culture experiments further reveal that sucrase activity is insensitive to dexamethasone in all types of recombinants whereas, alkaline phosphatase is highly stimulated over the levels present in the intestine developed in situ whatever the stromal support, except when this support is provided by rat gut mesenchyme. These results support the view that in the intestine the hormonal response is mediated by epithelial-mesenchymal interactions.

Animals↗

PubMed1984

Ability of L-triiodothyronine to modulate glucocorticoid-evoked brush border enzyme activities in cultured fetal rat intestine.

In vitro organ culture of developing fetal rat intestine emphasizes the absence of direct effect of thyroid hormone on several brush border enzymes in contrast with its ability to inhibit or enhance dexamethasone (DX) -evoked enzyme activities. Indeed, the presence of triiodothyronine in the culture medium leads mainly to a significant decrease of DX-stimulated lactase and to a further stimulation of DX-induced sucrase activities.

Animals↗

PubMed1984

Developmental pattern of brush border enzymes in the human fetal colon. Correlation with some morphogenetic events.

The present study is concerned with a multilevel approach to human colon organogenesis, involving scanning and transmission electron microscopy together with brush border enzymology. The results emphasize the particular developmental pattern of sucrase activity which appears towards 11 weeks, increases at 14 weeks, begins to decrease around 28 weeks and disappears totally at term. In contrast, other enzymes like aminopeptidase and alkaline phosphatase persist in the adult colon. The correlation, in the fetal large bowel, of enzyme activities and villus structures similar to those found in the small intestine is discussed.

Alkaline Phosphatase↗

PubMed1984

Early organogenesis of human small intestine: scanning electron microscopy and brush border enzymology.

Human small bowel early organogenesis was studied by scanning electron microscopy and found to be correlated to brush border enzymology. The appearance of the brush border enzymes sucrase, lactase, and aminopeptidase (measured in a purified apical membrane fraction) coincides with the first outgrowth of villi (eight weeks). Alkaline phosphatase was detected at seven weeks. The content of these enzymes furthermore increased up to the 14th week when both sucrase and aminopeptidase activities were comparable with adult values.

Alkaline Phosphatase↗

PubMed1984

Organ culture of fetal rat intestine. Effects on brush border enzyme activities of the combined administration of dexamethasone and cycloheximide or actinomycin D.

Jejunum of 19-day fetal rats was explanted in organ culture for 48 h in the presence of dexamethasone (DX) and cycloheximide (CX) or actinomycin D (Act D). The concentrations of both inhibitors which provided maximal responses without any detrimental alteration of the tissue were determined. During the culture period, CX (0.5 microgram/ml) totally abolished the production of both DX-stimulated enzymes (sucrase, maltase, lactase) and DX-insensitive enzymes (aminopeptidase, alkaline phosphatase). On the contrary, Act D at 2 micrograms/ml exhibited differential levels of inhibition related to the enzyme considered: 100% for sucrase and aminopeptidase, 70% for maltase and 50% for lactase. By contrast, alkaline phosphatase was stimulated 100% by Act D. These data suggest that the mechanism by which DX induces sucrase and stimulates maltase activity takes place at the transcriptional level. They also indicate that the basic maturation of at least maltase and lactase activities depends upon the traduction of a preexisting pool of mRNAs. The superinduced alkaline phosphatase activity obtained with Act D supports the notion that an Act D-sensitive repressor may play a role in the maturation process of this enzyme.

Animals↗

PubMed1981

[Permissive effects of human colonic cancer (HT-29 and Caco-2) on intestinal smooth muscle differentiation].

Human colonic carcinoma cells (lines HT-29 and Caco-2) were associated with 5 1/2 day-old chick embryonic intestinal mesenchyme and grafted for 11 days into 3 day-old Chick embryos. In these conditions, the cancer cells exert on the mesenchyme a supportative effect leading to its differentiation into muscular layers. The results provide additional evidence that HT-29 and Caco-2 cells exhibit common properties to fetal and normal intestinal cells.

Animals↗

PubMedDate not supplied

Mesenchyme-dependent differentiation of epithelial progenitor cells in the gut.

The digestive tract and the gut as a paradigm represents an attractive system for the study of mechanisms involved in the differentiation of two types of progenitor cells: the endodermal cells during embryonic life and the undifferentiated crypt cells during epithelial renewal of the adult intestine. The morphological and functional events that accompany the differentiation processes of progenitor cells into the polarized epithelial cell types characteristic of the intestine appear comparable in both situations (1,2). During organogenesis of the gut, histological observations underlined a close relationship between epithelial cells and their underlying mesenchymal cells (3,4). Developmental biologists have emphasized experimentally the importance of interactions between the endoderm and mesenchyme during organogenesis of the digestive tract. In the adult intestine, gastroenterologists have focused their attention on a specialized mesenchymal cell type (the pericryptal fibroblasts) that displays, like epithelial cells, proliferative activities and migrating properties. The aim of this review is to provide current knowledge on epithelial-mesenchymal interactions during ontogenesis of the digestive tract and also to relate some experiments supporting the view of the perpetuation of epithelial-mesenchymal interactions beyond embryonic life.

Animals↗