Personne :
Michel, Martine

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Département de médecine moléculaire, Faculté de médecine, Université Laval
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Voici les éléments 1 - 7 sur 7
  • Publication
    Accès libre
    Keratin 19 as a biochemical marker of skin stem cells in vivo and in vitro: keratin 19 expressing cells are differentially localized in function of anatomic sites, and their number varies with donor age and culture stage
    (Cambridge University Press, 1996-05-01) Török, Natalie; Michel, Martine; Germain, Lucie; Lussier, Marc; Godbout, Marie-Josée; Gaudreau, Pierrette; Royal, André
    This study was undertaken to evaluate keratin 19 (K19) as a biochemical marker for skin stem cells in order to address some long standing questions concerning these cells in the field of cutaneous biology. We first used the well-established mouse model enabling us to identify skin stem cells as [3H]thymidine-label-retaining cells. A site directed antibody was raised against a synthetic peptide of K19. It reacted specifically with a 40 kDa protein (K19) on immunoblotting. It labelled the bulge area of the outer root sheath on mouse skin by immunohistochemistry. Double-labelling revealed that K19-positive-cells were also [3H]thymidine-label-retaining cells, suggesting that K19 is a marker for skin stem cells of hair follicles. K19-expression was then used to investigate the variation in mouse and human skin stem cells as a function of body site, donor age and culture time. K19 was expressed in the hair follicle and absent from the interfollicular epidermis at hairy sites (except for some K18 coexpressing Merkel cells). In contrast, at glabrous sites, K19-positive-cells were in deep epidermal rete ridges. K19 expressing cells also contained high levels of alpha 3 beta 1 integrin. The proportion of K19-positive-cells was greater in newborn than older foreskins. This correlated with keratinocyte culture lifespan variation with donor age. Moreover, it could explain clinical observations that children heal faster than adults. In conclusion, K19 expression in skin provides an additional tool to allow further characterization of skin stem cells under normal and pathological conditions in situ and in vitro.
  • Publication
    Skin stem cell identification and culture : a potential tool for rapid epidermal sheet production and grafting
    (Landes Bioscience, 2018-01-29T18:34:34Z) Michel, Martine; Li, Hui; Germain, Lucie; Xu, Wen; Godbout, Marie-Josée; Fradette, Julie; Rouabhia, Mahmoud
    Stem cells are fascinating. They are a production factory and give rise to the differentiated tissues. During embryonic development, stem cells multiply and differentiate to generate the cellular diversity necessary for the formation of all tissues. The pluripotentiality of embryonic stem cells is very large. Stem cells in the embryo are probably different from those in adults in the sense that some embryonic stem cells are present only transiently and their pluripotentiality is greater than that of adult stem cells which are limited to one compartment, e.g., blood, cutaneous or intestinal epithelial cells. In this chapter, we will concentrate on skin stem cells of postnatal mammals. During the adult life, stem cells are responsible for tissue homeostasis; they proliferate to maintain the number of differentiated cells at a constant level and replace dead cells or cells lost through injury.
  • Publication
    Anchored skin equivalent cultured in vitro: a new tool for percutaneous absorption studies
    (Tissue Culture Association, 1993-11-01) Michel, Martine; Germain, Lucie; Auger, François A.
    Dear Editor: The recent awareness that skin plays many important roles, such as a physical and immunological semi-permeable membrane which protects the whole body surface from water loss and selectively controls the rate of molecule penetration in the circulatory system, has fostered a keen interest in percutaneous absorption studies. The development of transdermal therapeutic system has concretely shown that skin bioabsorption properties are of major interest in the pharmaceutical industry (7). Moreover, in the field of toxicology, potentially harmful compounds that come in contact with the body surface must be tested. Different models have been designed to evaluate this important biological skin function using fresh or frozen skin (7,10,12,18). A major drawback of these models is the constant need of a human or animal skin supply which may lead to technical and ethical problems. Human cadaver skin is not easily available for most investigators. Moreover, an important and unavoidable variability in the skin absorption properties has been observed between samples from different individuals (21). Therefore, the present study was undertaken to set up an in vitro cultured skin equivalent for percutaneous absorption studies which could remedy these drawbacks. Recent progress in cell and tissue culture lead to the production of skin equivalents composed of a keratinocyte layer growing on a dermal equivalent. Various dermal equivalents have been proposed upon which keratinocytes can be seeded (1,15,19,20). These epidermal cells will remain in an undifferentiated state when the three-dimensional culture is kept immersed in the culture medium. However, an improved epidermal cell differentiation, characterized by the formation of the stratum corneum, is obtained when these skin equivalents were cultured at the air-liquid interface (13). In order to produce a skin equivalent suitable for the measurement of in vitro percutaneous absorption, we have adapted our previous design described for dermal equivalent anchorage (8) to the culture of skin equivalent. This technique allows these skin equivalents to be easily mounted on Franz diffusion cells. In the present study, human keratinocytes and dermal fibroblasts were isolated from normal adult skin specimens removed during plastic surgery and cultured as previously described (2,6,16). Dermal equivalents were prepared according to the method of Bell (1), with some modifications as described by Rompr~ et at. (17). The collagen/fibroblasts mixture was poured into a petri dish (35 mm in diameter) containing a ring of filter paper, accordingly to the method developed by L5pez Valle et at. (8), to prevent the collagen lattice contraction. In the present study, this anchorage was not glued to the bottom of the dish, to facilitate the subsequent technical manipulations of the skin equivalent. After keratinocyte addition, such a system led to the production of a skin equivalent presenting a constant surface area (Fig. 1). These skin equivalents, when raised at the air-liquid interface using conventional systems i.e. deposition
  • Publication
    From newborn to adult : phenotypic and functional properties of skin equivalent and human skin as a function of donor age
    (Liss, 1997-05-01) Michel, Martine; Germain, Lucie; L'Heureux, Nicolas; Auger, François A.
    The skin's most important function is to act as a barrier against fluid loss, microorganism infections, and percutaneous absorption. To fulfill this role, keratinocytes proliferate and differentiate to produce a protective layer: the stratum corneum. Because stem cells are responsible for the production of differentiated progeny and stem cells (K19-expressing cells) are less abundant in skin from older donors, the purpose of this study was to establish whether histological and functional properties of differentiating skin is influenced by donor age. The in vitro model developed for the evaluation of skin properties (Michel et al., 1995) was used to produce skin equivalents from newborn, child, and adult keratinocytes. Throughout maturation, skin equivalents were compared with corresponding skin biopsies for keratin, filaggrin, and transglutaminase expression. Percutaneous absorptions of hydrocortisone also were measured and correlated with lipid content. After 1 wk of immersed culture, the epidermal layer of newborn skin equivalents was thicker than child and adult epidermis. As expected, a greater proportion of cutaneous stem cells was present in newborn compared with children and adult skin equivalents. No age-related difference was observed for differentiation markers. When skin equivalents were cultured at the air-liquid interface, cell differentiation and stratum corneum formation were induced, and the age-related variation in the thickness of the epidermal layer disappeared. Percutaneous absorption through these matured skin equivalents did not vary with age. Their lipid density and profile were similar. Accordingly, skin biopsies exhibited comparable percutaneous absorption profiles independently of donor age. In conclusion, although newborn skin equivalents, or skin biopsies, contained more stem cells than child and adult counterparts, no age-related histological difference was observed in the differentiated tissues. Moreover, the functional barrier property of skins and matured skin equivalents did not vary with age. Therefore, both newborn and adult keratinocytes produce useful in vitro models to study epidermal differentiation processes involved in both normal and pathological states.
  • Publication
    Localization of merkel cells at hairless and hairy human skin sites using keratin 18
    (National Research Council of Canada, 1995-09-01) Michel, Martine; Germain, Lucie; Godbout, Marie-Josée; Fradette, Julie
    Les cellules de Merkel sont des cellules cutanées particulières, possédant non seulement des granules de sécrétion contenant des neuropeptides, mais également des desmosomes et des tonofilaments formés des kératines 8, 18, 19 et 20. Les cellules de Merkel sont plutôt rares dans la peau d'adulte. Toutefois, elles ont été observées en plus grande quantité dans les régions sans poils, telles la paume des mains et la plante des pieds. Leur présence a aussi été rapportée dans les follicules pileux. Les cellules de Merkel sont souvent innervées par des fibres nerveuses sensorielles et on leur reconnaît un rôle de mécanorécepteurs dans la peau. Toutefois, leur origine et fonction précises ne sont pas encore clairement établies. Le but de cette étude était de localiser les cellules de Merkel dans des régions anatomiques pourvues ou non de follicules pileux, par immunohistochimie avec les anticorps Ks18.174 et Ks19.1 respectivement dirigés contre les kératines 18 et 19. Dans la paume des mains et la plante des pieds, les cellules de Merkel ont été identifiées dans la couche basale de l'épiderme, à la base des papilles. Pour étudier la localisation des cellules de Merkel dans une région possédant des poils, nous avons choisi la peau provenant de réduction mammaire car on y trouve de petits follicules pileux représentatifs des poils couvrant une grande partie de notre corps. Des cellules de Merkel ont été observées dans l'épiderme interfolliculaire et dans le follicule pileux, où elles ont été localisées dans la région de l'isthme.Mots clés : peau, humain, cellule de Merkel, kératines, follicule pileux.
  • Publication
    Functional evaluation of anchored skin equivalent cultured in vitro : percutaneous absorption studies and lipid analysis
    (Plenum Press, 1995-01-01) Michel, Martine; Germain, Lucie; Bélanger, Pierre Maxime; Auger, François A.
    In vitro cutaneous models, resulting from recent progress in human cell culture, provide new tools to investigate the development, physiology and pharmacology of the human skin. Indeed, several skin equivalents (SE) have been produced by seeding keratinocytes upon various dermal substrates. One consists of de-epidermized dermis without living fibroblasts but exhibiting an intact basement membrane (1,2). Living dermal models could be obtained in vitro by growing dermal fibroblasts on a nylon mesh or in a sponge such that they deposit extracellular matrix (3,4). The reorganization and contraction of collagen matrix by included fibroblasts also results in a tridimensional dermal layer (5). We adapted the latter method to produce an anchored skin equivalent (ASE) combining the following advantages: i) a large number of similar ASE could be generated with cells cultured from a single skin biopsy. Therefore, this obviates the need for a constant supply of human skin. ii) Replicates could be submitted to quality control during their production. iii) This anchorage design impeded collagen gel contraction thus leading to the production of a SE with a large and defined surface area. iv) The absence of any supporting or embedded material into our ASE facilitated its manipulation and prevented any eventual deleterious effect of foreign matter. Furthermore the absence of any extraneous material avoids an eventual adsorption effect (6).
  • Publication
    Characterization of a new tissue-engineered human skin equivalent with hair
    (springerLink, 1999-06-01) Michel, Martine; Germain, Lucie; Xu, Wen; L'Heureux, Nicolas; Auger, François A.; Pouliot, Roxane
    We designed a new tissue-engineered skin equivalent in which complete pilosebaceous units were integrated. This model was produced exclusively from human fibroblasts and keratinocytes and did not contain any synthetic material. Fibroblasts were cultured for 35 d with ascorbic acid and formed a thick fibrous sheet in the culture dish. The dermal equivalent was composed of stacked fibroblast sheets and exhibited some ultrastructural organization found in normal connective tissues. Keratinocytes seeded on this tissue formed a stratified and cornified epidermis and expressed typical markers of differentiation (keratin 10, filaggrin, and transglutaminase). After 4 wk of culture, a continuous and ultrastructurally organized basement membrane was observed and associated with the expression of laminin and collagen IV and VII. Complete pilosebaceous units were obtained by thermolysin digestion and inserted in this skin equivalent in order to assess the role of the transfollicular route in percutaneous absorption. The presence of hair follicles abolished the lag-time observed during hydrocortisone diffusion and increased significantly its rate of penetration in comparison to the control (skin equivalent with sham hair insertion). Therefore, this new hairy human skin equivalent model allowed an experimental design in which the only variable was the presence of pilosebaceous units and provided new data confirming the importance of hair follicles in percutaneous absorption.