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M Pruniéras

Publications and source records attributed to M Pruniéras.

At least 19 recordsLinked to original sources
PubMed1991

6'-substituted naphthalene-2-carboxylic acid analogs, a new class of retinoic acid receptor subtype-specific ligands.

The biological response to retinoic acid (RA) and synthetic derivatives (retinoids) is mediated by three nuclear retinoic acid receptors, RAR alpha, beta and gamma. To explore the potential of retinoids as receptor subtype selective activators, we employed a transcriptional activation assay. Hybrid receptors that recognize an estrogen response element were used to avoid measuring activities of endogenous retinoic acid receptors. In response to retinoic acid, the three hybrid receptors ER-RAR alpha, ER-RAR beta and ER-RAR gamma exhibited the same induction profile as the corresponding wild type receptors RAR alpha, RAR beta, and RAR gamma. Three different retinoids, analogs of 6'-substituted naphthalene-2-carboxylic acid, elicited strong transcriptional activation of gamma receptor while no activation of alpha receptor was observed. Conversely, two retinobenzoic acid analogs showed a limited alpha selectivity. We conclude that retinoids with unique profiles of retinoic acid receptor subtype selectivity can be defined and tested for their impact on cellular differentiation and for therapeutical applications.

Animals↗
PubMed1987

Wound healing of human skin transplanted onto the nude mouse. II. An immunohistological and ultrastructural study of the epidermal basement membrane zone reconstruction and connective tissue reorganization.

The reconstruction of human epidermis during healing of human skin wounded after grafting onto the nude mouse was described in a previous paper (M. Démarchez, P. Sengel, and M. Pruniéras, 1986, Dev. Biol. 113, 90-96). The regeneration of the epidermal basement membrane zone (BMZ) and the reorganization of the connective tissue are the subjects of the present study. They were investigated by two complementary methods: electron microscopy to analyze the BMZ reorganization, and indirect immunofluorescence with species-specific and cross-reacting antibodies directed against laminin, bullous pemphigoid antigen, mouse or human collagens of types I or IV, human elastic fibers, fibronectin, fibrin, actin, and human vimentin, to examine the species origin and distribution of BMZ and connective tissue components during the regeneration process. It is reported that grafted human skin preserves its own immunological markers not only in the epidermis but also in the BMZ and dermis as well, and that, after injury, its regeneration proceeds according to the following sequence of overlapping events: production of a mouse granulation tissue; reepidermization by human cells; reconstruction of a BMZ with human characteristics; formation of a human neodermis. It is concluded that human skin grafted onto the nude mouse is able to regenerate its three structural compartments, namely, the epidermis, BMZ, and dermis. Interestingly, it appeared, also, that the connective tissue regeneration would be a two-step mechanism including the sequential formation of two tissues of distinct sources, namely, a granulation tissue and a neodermis.

Animals↗
PubMed1986

Human epidermis reconstructed by culture: is it "normal"?

Human keratinocytes were grown on a dermal equivalent (or lattice) at the liquid-air interface in an attempt to reconstitute a functional epidermis in vitro. Although the multilayered epithelium thus obtained is well differentiated, as shown by the presence of keratohyaline granules and horny layer, several differences from its in vivo counterpart were also observed: In the reconstructed epidermis, basal keratinocytes do not have the cuboidal shape found in vivo; they synthesize bullous pemphigoid antigen and laminin, but the distribution of these antigens is not linear as in vivo; they contain the plasma-membrane antigens restricted to the basal layer in vivo (VM1, BC1), but these antigens are not polarized; lack of polarization is also evidenced by the distribution of actin. Differentiation markers appear but with a topography slightly different from that of epidermis in vivo; the 67-kD keratin does not appear in the first suprabasal layer as in vivo but above; involucrin, which appears in the granular layers in vivo appears as soon as the cells leave the basal layer. psi 3 antigen and fibronectin found in vivo only in hyperproliferative epidermis (wound healing, psoriasis) are detected. Hyperproliferation would also explain the unexpected straining of basal cells by KL1 monoclonal antibody. Because of the potential clinical or pharmacologic use of artificial epidermis, the question of whether the epidermis obtained in vitro can be considered as "normal" is discussed.

Antibodies, Monoclonal↗
PubMed1986

Onset of epidermal differentiation in rapidly proliferating basal keratinocytes.

Stratified epithelia such as epidermis are classically considered to comprise 2 cell compartments, one consisting of undifferentiated proliferative cells occupying the basal layer, and the other consisting of differentiated postmitotic cells occupying the suprabasal layers. It is also generally assumed that the 58K basic-50K acidic couple of keratins is expressed in basal cells, while the 67K basic-56K acidic couple appears in suprabasal cells. In the present work we demonstrate that the population of basal keratinocytes is heterogeneous, since 8% of them are found to express the 67-56K "suprabasal" set of keratins. The morphology of these transitional cells suggests that they are in the process of detaching from the basement membrane to move upward to the epidermis. Cytoflow-fluorometric studies showed that the fraction of cells in S plus G2/M phases is 4 times higher in transitional keratinocytes than in basal or suprabasal keratinocytes. Altogether, these results suggest that the onset of terminal differentiation occurs in human epidermis in a subpopulation of keratinocytes which are still located in the basal layer, and that a transient increase in proliferation occurs when the cells engage in terminal differentiation and are ready to move toward the suprabasal layers.

Adult↗
PubMed1983

Methods for cultivation of keratinocytes with an air-liquid interface.

In ordinary cultures, cells are grown on artificial substrates and immersed in culture medium. In vivo, interfollicular epidermal cells grow on the basement membrane and are exposed to air. In a first effort to render the culture of these cells more physiological it seems legitimate to raise the cultured cells to the air-medium interface. Epidermal cells can be raised by the use of collagen gels maintained on a rigid support. They can also be grown on nitrocellulose filters coated with collagen or coated with a basement-membrane equivalent (BME) previously deposited by bovine corneal endothelial cells. By raising the cultures to the air-medium interface there is some evidence of a more complete differentiation, as evaluated by morphologic criteria. However, biochemically, the raising of the cultures does not seem to induce the synthesis of those keratin polypeptides which are not expressed in immersed cultures. Epidermal cells can also be raised by culturing them on dermal substrates or dermal equivalents. When they were cultured on inverted dead pig skin, epidermal cells synthesized membrane-coating granules (MCG). MCG were not found in immersed controls. By culturing epidermal-cell suspensions on dead deepidermized dermis (DED), all morphologic markers of differentiation were seen except the keratin pattern. In addition, partial reexpression of high-molecular-weight keratin polypeptides occurred. However, the complete expression of keratins by cultured cells depends on the filtering action of the dermal substrate (the cultures are fed from underneath) more than on exposure to the air-liquid interface. In summary, several methods are available to culture epidermal cells at the air-liquid interface that are of interest in an investigation of the response of these cells to epigenetic influences.

Air↗
PubMed1983

Keratinocytes synthesize basal-lamina proteins in culture.

On histologic vertical sections of skin, the epidermis is separated from the dermis by an amorphous thin membrane, the basal lamina. Ultrastructurally, the basal lamina is composed of four areas, including the basal-cell plasma membrane and hemidesmosomes, the lamina lucida, the lamina densa, and the sub-lamina densa fibrillar region. In culture, epidermal keratinocytes are able to produce hemidesmosomes, lamina lucida, and lamina densa. There is no evidence that cultured keratinocytes can produce sub-lamina densa fibrils. Biochemically, the lamina lucida contains two major glycoproteins. One, the bullous pemphigoid antigen, is synthesized by epidermal keratinocytes in vitro. These cells also synthesize laminin, the other glycoprotein of lamina lucida. At the interface between lamina lucida and lamina densa there is probably a heparan sulfate proteoglycan. Whether this proteoglycan is produced by keratinocytes in culture is not known, but the possibility can be considered. Lamina densa contains collagen IV, and this collagen is synthesized by keratinocytes in culture. However, cultured keratinocytes may also synthesize collagen types I, III, and V. Type V is associated with the basal lamina, but its exact location is unknown. Types I and III (if they are produced in vivo) would be situated in the sub-basal lamina region. The problem of fibronectin remains unsolved. There is "some" fibronectin in the lamina lucida, but its origin is not clear.

Animals↗
PubMed1982

Pemphigoid, pemphigus and Pr antigens in adult human keratinocytes grown on nonviable substrates.

Isolated adult human keratinocytes were grown either on plastic coverslips or a nonviable basement membrane surface containing intact laminin, type IV and V collagens, and heparan sulfate proteoglycan and examined by indirect immunofluorescence for the expression of bullous pemphigoid, pemphigus and Prlh antigens. Initial cell suspensions had a mean of 23% and 30%, respectively, of bullous pemphigoid and Prlh positive staining cells, while those stained with pemphigus serum were usually negative (19 of 22 series). Pemphigus antigen was expressed as intercellular staining between keratinocytes within 24 hr in both cultures on plastic and basement membrane. Likewise, Prlh antigen was expressed within 24 hr as a homogeneous cytoplasmic fluorescence leaving the basement membrane zone unstained. In contrast, pemphigoid antigen was expressed as a linear fluorescent band at the basement membrane zone between days 3 and 4 of culture. Systematic cell counts of bullous pemphigoid antigen positive cells from trypsin disrupted primary cultures made on plastic over time showed a nadir (8%) of positive cells in early cultures after which the percentage rapidly rose to a peak of 58% between days 14 and 21 of culture. In subcultures repeatedly disrupted at short intervals, the percentage of bullous pemphigoid positive cells remained low when compared to those interrupted and passaged over longer intervals. The percentage of bullous pemphigoid antigen bearing cells in culture over time is similar, but not identical, to the percentage of basal cells and is related to the age and known growth kinetics of the cultures system. Bullous pemphigoid, pemphigus and Prlh antigens are synthesized by the epidermal cell whether cultured on basement membrane or plastic.

Antigens↗
PubMed1982

Effects of phorbol esters on basal epidermal cells derived from ear skin of adult guniea pigs.

In cultures of basal epidermal cells obtained from ear skin of adult guinea pigs, the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate induces cellular proliferation which is prostaglandin dependent and inhibited by indomethacin. Inhibition by indomethacin can be overcome by prostaglandins E2 and F2 alpha, with prostaglandin F2 alpha being more effective. The concomitant induction of ornithine decarboxylase activity is insensitive to indomethacin inhibition. The nonpromoting derivative 4-O-methyl-12-O-tetradecanoylphorbol-13-acetate evokes a prostaglandin-independent, i.e., indomethacin-insensitive, stimulation of cell proliferation without inducing ornithine decarboxylase activity.

Animals↗
PubMed1980

In vitro basal lamina formation may require non-epidermal cell living substrate.

In an adult human epidermal cell culture system in which three different types of dermo-epidermal junctions could be observed, the in vitro synthesis of basement membrane and type IV collagen was studied with electron microscopy and indirect immunofluorescence via an antiserum to type IV collagen. Essentially, keratinocytes juxtaposed to non-living substrate did not produce either type IV collagen or an ultrastructural basement membrane, whereas both products were found at dermo-epidermal junctions composed of living keratinocytes juxtaposed to living dermis. This suggests that the microenvironment of the keratinocyte may influence the synthesis of junctional components.

Adult↗
PubMed1979

Physiological regulation of epidermal cell growth.

According to the negative feedback theory, epidermal growth is regulated in vivo (at least in part) by the combined action of two inhibitors upon the basal cell proliferative pool. One blocks 85% of basal cells in G1 the other blocks 5--10% in G2. When isolating and culturing in vitro populations of basal cells from adult guinea pig skin, it has been possible to confirm that these cells are sensitive to both G1 and G2 inhibitions. However, only a small fraction (10% or less) of the G1 blocked cell population would be governed by G1 inhibitory messages released by suprabasal, maturing keratinocytes. As regards the G2 block in vitro experiments confirm that basal cells produce a G2 blocker to which about 9% or less are susceptible. The relatively good correspondence between in vitro and in vivo experimental data point to the interest of adult isolated epidermal basal cell cultures as a model for the study of epidermal growth regulatory mechanisms.

Animals↗
PubMed1978

Homeostatic regulation of epidermal cells in culture.

The growth potential (DNA synthesis) of purified epidermal basal cells in culture, according to time reveals two peaks, at days 1 and 6. The same potential estimated in total cultures of epidermal cells (including basal and high level cells) shows only one peak at day 9. This suggests that hig-level mature cells inhibit DNA synthesis in basal cells in culture. This interpretation has been confirmed in showing that increasing amounts of mature cells inhibited DNA synthesis in basal cells in a dose dependent manner. Basal cells in culture are therefore susceptible to homeostatic regulation. However, this regulation is not tissue specific since DNA synthesis was also inhibited by mature epidermal cells in cultures of dermal as well as bone marrow cells. Assuming that the culture of epidermal cells is representative of the in vivo situation, these experiments would suggest that the specificity of action of the G1 chalone in vivo might depend as much on the target tissue as the proper nature of the inhibitor.

Animals↗
PubMed1978

[Warts, viruses, cancer (author's transl)].

The malignant transformation of cutaneous lesions in epidermodysplasia verruciformis (E.V.), which lesions are caused by a human papilloma virus (HPV), can be compared to that experimentally induced by the polyoma virus. Thus, HPV would undergo a lytic, transformant and/or abortive cycle in epidermal cells. In this latter case, it would increase cell DNA synthesis and there would be production of cellular antigens coded by the virus. This production of cellular antigens would be the result of the incorporation of part of HPV-DNA into the genome of the cell. The presence of part of HPV-DNA in the cell genome would also increase the susceptibility of infected cells to malignant transformation with other Papova viruses. On practical grounds it is not advisable to use potentially mutagenic treatments such as X or U. V. irradiations in the management of HPV induced lesions in man, especially those of E.V.

Animals↗
PubMed1976

The culture of skin. A review of theories and experimental methods.

Two main criticisms can be leveled against the standard methods of skin culture: they are poorly quantifiable and the cultured cell populations are heterogeneous. A new technique based mainly on enzymatic dissociation allows specific cell types to be extracted from the skin before cultivation. In this way, separate cultures of epidermal keratinocytes and dermal fibroblasts can be obtained from the same piece of skin. These purified systems have been used to study the kinetics of epidermal cell growth and to quantify the effect of various chemically defined substances on the growth and differentiation of keratinocytes. With further refinements in technique, purified populations of melanocytes can be extracted. The co-culture of pigmented melanocytes with albino keratinocytes has been proposed as a model to study pigment donation in vitro. The usual organ culture technique, including the use of large explants of skin immersed in the culture fluid, has been modified to show that adult human skin partially regenerates in vitro and that mitotic activity goes on for months in the regenerated epidermis. The use of nucleic acid hybridization techniques, combined with skin cell cultures from human tumors, opens new avenues of research on human cancer.

Amino Acids↗