Functional Expression of AQP3 in Human Skin Epidermis and Reconstructed Epidermis

The purpose of this study was to examine the presence of aquaporin water channels in human skin and to assess their functional role. On western blots of human epidermis obtained from plastic surgery, a strong signal was obtained with polyclonal anti-aquaporin-3 antibodies. By indirect immunofluorescence on 5 µm cryosections, anti-aquaporin-3 antibodies strongly stained keratinocyte plasma membranes in human epidermis, whereas no staining was observed in the dermis or the stratum corneum or when anti-aquaporin-3 antibodies were preabsorbed with the peptide used for immunization. Similarly, a strong signal with anti-aquaporin-3 antibodies was observed in keratinocyte plasma membranes of reconstructed human epidermis in culture at the air–liquid interface for up to 3 wk. The keratinocyte plasma membrane localization of aquaporin-3 was confirmed at the electron microscope level in prickle cells. In addition an intracellular localization of aquaporin-3 was also detected in epidermis basal cells. Osmotically induced transepidermal water permeability was measured on stripped human skin and on reconstructed epidermis. Water transport across both stripped human skin and 2–3 wk reconstructed epidermis was comparable, inhibited by > 50% by 1 mM HgCl2 and fully inhibited by acid pH. By stopped-flow light scattering, keratinocyte plasma membranes, where aquaporin-3 is localized, exhibited a high, pH-sensitive, water permeability. Although human skin is highly impermeable to water, this is primarily accounted for by the stratum corneum, where a steep water content gradient was demonstrated. In contrast, the water content of viable strata of the epidermis is remarkably constant. Our results suggest that the human epidermis, below the stratum corneum, exhibits a high, aquaporin-3-mediated, water permeability. We propose that the role of aquaporin-3 is to water-clamp viable layers of the epidermis in order to improve the hydration of the epidermis below the stratum corneum

Les cadres théoriques et méthodologiques

La partie thématique de ce numéro 11 de RDST se donne pour but de faire le point et de discuter les choix des cadres théoriques et méthodologiques en didactique des sciences et des technologies. Même si ce dossier ne peut, a lui tout seul, donner une vue d’ensemble de la structuration du champ des recherches en didactique des sciences et des technologies, les quatre articles présentés rendent compte de la diversité des objets de recherche travaillés dans le champ (pratiques enseignantes, pratiques efficaces, description des situations d’enseignement-apprentissage, travail de l’obstacle), de la diversité des cadres théoriques construits par les chercheurs (travail de l’obstacle, théorie de l’action conjointe en didactique, problématisation) et des emprunts réalisés à d’autres disciplines (comme aux travaux réalisés en sciences du langage). Ainsi, ces articles permettront aux lecteurs de comprendre : - comment un même objet (description de débats scientifiques autour d’objets géologiques) peut être étudié à partir de deux cadres théoriques différents et en quoi cela permet d’engager un travail de comparaison entre ces cadres ; - comment des nouvelles questions de recherche (la variété des échelles de temps à prendre en compte pour décrire des situations d’enseignement-apprentissage et la question des liens entre ces échelles, les pratiques efficaces) conduisent à la construction de nouvelles élaborations théoriques et méthodologiques ou à une reprise de certains travaux avec un déplacement des points de vue rendu nécessaire par la mise en dialogue d’une tradition de recherche anglo-saxonne et francophone dans le champ de la didactique des sciences ; - comment l’analyse des travaux d’un scientifique peut contribuer à documenter la mise au travail des obstacles épistémologiques. The theme of this issue aims at discussing the choice of theoretical and methodological frameworks in science and technology education. Although this issue cannot give a complete overview of the structure of research in the field of science and technology education, the four papers presented here reflect the diversity of the research subjects in this field (teaching practices, efficient practices, description of teaching-learning situations, working the obstacle), the diversity of theoretical frameworks built by researchers (working the obstacle, the joint action theory in didactics, problematization) and loans made to other disciplines (such as the work done in Language Sciences). These articles thus will help readers to understand: - How the same object (description of scientific debates around geological objects) can be studied from two different theoretical frameworks and how this allows to initiate a working comparison between these frameworks; - How new research questions (the variety of time scales to consider to describe the teaching-learning situations and the issue of the links between these scales, efficient practices, etc.) lead to the construction of new theoretical and methodological elaborations or a reevaluation of some works with a shift in viewpoints made necessary by the setting of a dialogue between Anglo-Saxon and Francophone traditions in the field of science education; - How the analysis of a scientist’s work can contribute to document the work of epistemological obstacles