210 research outputs found
Programmes de recherches en didactique des langues germaniques à l'ULg ces dix dernières années : présentation et évaluation
Cette communication fait le bilan de dix années de recherches collaboratives menées par le service de didactique spéciale des langues modernes de l'ULg en collaboration avec le service de didactique professionnelle et formation des enseignants (J. Beckers). Les caractéristiques de ces recherches sont isolées et situées par rapport au courant du "nouvel éclectisme" de l'ère post-communicative. Le modèle d'implantation des innovations pédagogiques de T.R. Guskey (1986) est présenté et commenté. Enfin, une brève évaluation de l'ensemble de ces recherches est proposée. Les annexes comportent, entre autres, une synthèse des quatre recherches ménées entre 1997 et 2006
Normal Human Merkel Cells are Present in Epidermal Cell Populations Isolated and Cultured from Glabrous and Hairy Skin Sites
The Merkel cell is a highly specialized cell that primarily acts as a slowly adapting mechanoreceptor. Merkel cells are scarce in normal skin but can be identified by the expression of distinct keratin filaments. Merkel cells constitute a very unique population and many questions still remain as to their origin, number, proliferative capacity, and functions in cutaneous biology. The dissociation of epidermal cells from skin is a widely used technique to extract and culture keratinocytes. We took advantage of a two-step extraction method to quantify keratin-20-expressing Merkel cells among total cutaneous cells obtained from either hairy or glabrous skin biopsies. Flow cytometry analysis revealed that keratin-20-labeled Merkel cells represent between 3.6% and 5.7% of freshly dissociated basal epidermal cells. No significant differences were seen between samples derived from glabrous palmar and hairy anatomic sites, from children and adult, respectively. We also report on the presence of Merkel cells in primary and first subcultures of epidermal cells indicating their capacity to remain viable after extraction from skin of various anatomic sites. To our knowledge, this is the first demonstration of nontumorigenic human Merkel cells in culture in vitro. The persistence of a small number of Merkel cells in culture suggests that, with the development of appropriate culture conditions, these cells could be amplified and further studied to unravel long-standing questions relative to their paracrine function or epithelial origin
Outils diagnostiques et stratégies de remédiation au service des langues étrangères
Quand l’Évolution se prête au jeu…Â
Créé par l’École de l’ADN et ses partenaires, « Trivial Évolution » est un jeu éducatif qui a pour objectifs de faire découvrir les concepts de base de l’Évolution des espèces et de combattre les idées reçues sur la théorie de l’Évolution : les concepteurs présentent ici une première évaluation de cet outil ludique de vulgarisation scientifique.Developed by the ADN school and its partners, « Trivial Evolution » is an educational board game which aims at helping players to grasp the basic concepts of species evolution, and to combat preconceived ideas concerning the Evolution theory: the designers present a first-time assessment of this educative and fun tool for the general public interested in Science
Production of a bilayered self-assembled skin substitute using a tissue-engineered acellular dermal matrix
Our bilayered self-assembled skin substitutes (SASS) are skin substitutes showing a structure and functionality very similar to native human skin. These constructs are used, in life-threatening burn wounds, as permanent autologous grafts for the treatment of such affected patients even though their production is exacting. We thus intended to shorten their current production time to improve their clinical applicability. A self-assembled decellularized dermal matrix (DM) was used. It allowed the production of an autologous skin substitute from patient's cells. The characterization of SASS reconstructed using a decellularized dermal matrix (SASS-DM) was performed by histology, immunofluorescence, transmission electron microscopy, and uniaxial tensile analysis. Using the SASS-DM, it was possible to reduce the standard production time from about 8 to 4 and a half weeks. The structure, cell differentiation, and mechanical properties of the new skin substitutes were shown to be similar to the SASS. The decellularization process had no influence on the final microstructure and mechanical properties of the DM. This model, by enabling the production of a skin substitute in a shorter time frame without compromising its intrinsic tissue properties, represents a promising addition to the currently available burn and wound treatments
In vivo remodeling of fibroblast-derived vascular scaffolds implanted for 6 months in rats
There is a clinical need for tissue-engineered small-diameter (<6 mm) vascular grafts since clinical applications are halted by the limited suitability of autologous or synthetic grafts. This study uses the self-assembly approach to produce a fibroblast-derived decellularized vascular scaffold (FDVS) that can be available off-the-shelf. Briefly, extracellular matrix scaffolds were produced using human dermal fibroblasts sheets rolled around a mandrel, maintained in culture to allow for the formation of cohesive and three-dimensional tubular constructs, and decellularized by immersion in deionized water. The FDVSs were implanted as an aortic interpositional graft in six Sprague-Dawley rats for 6 months. Five out of the six implants were still patent 6 months after the surgery. Histological analysis showed the infiltration of cells on both abluminal and luminal sides, and immunofluorescence analysis suggested the formation of neomedia comprised of smooth muscle cells and lined underneath with an endothelium. Furthermore, to verify the feasibility of producing tissue-engineered blood vessels of clinically relevant length and diameter, scaffolds with a 4.6 mm inner diameter and 17 cm in length were fabricated with success and stored for an extended period of time, while maintaining suitable properties following the storage period. This novel demonstration of the potential of the FDVS could accelerate the clinical availability of tissue-engineered blood vessels and warrants further preclinical studies
Electric potential across epidermis and its role during wound healing can be studied by using an in vitro reconstructed human skin
Background : After human epidermis wounding, transepithelial potential (TEP) present in nonlesional epidermis decreases and induces an endogenous direct current epithelial electric field (EEF) that could be implicated in the wound re-epithelialization. Some studies suggest that exogenous electric stimulation of wounds can stimulate healing, although the mechanisms remain to be determined.
The Problem : Little is known concerning the exact action of the EEF during healing. The mechanism responsible for TEP and EEF is unknown due to the lack of an in vitro model to study this phenomenon.
Basic Science Advances : We carried out studies by using a wound created in a human tissue-engineered skin and determined that TEP undergoes ascending and decreasing phases during the epithelium formation. The in vitro TEP measurements over time in the wound were corroborated with histological changes and with in vivo TEP variations during porcine skin wound healing. The expression of a crucial element implicated in Na+ transport, Na+/K+ ATPase pumps, was also evaluated at the same time points during the re-epithelialization process. The ascending and decreasing TEP values were correlated with changes in the expression of these pumps. The distribution of Na+/K+ ATPase pumps also varied according to epidermal differentiation. Further, inhibition of the pump activity induced a significant decrease of the TEP and of the re-epithelization rate.
Clinical Care Relevance : A better comprehension of the role of EEF could have important future medical applications regarding the treatment of chronic wound healing.
Conclusion : This study brings a new perspective to understand the formation and restoration of TEP during the cutaneous wound healing process
Improved methods to produce tissue-engineered skin substitutes suitable for the permanent closure of full-thickness skin injuries
There is a clinical need for skin substitutes to replace full-thickness skin loss. Our group has developed a bilayered
skin substitute produced from the patient’s own fibroblasts and keratinocytes referred to as Self-Assembled Skin
Substitute (SASS). After cell isolation and expansion, the current time required to produce SASS is 45 days. We
aimed to optimize the manufacturing process to standardize the production of SASS and to reduce production
time. The new approach consisted in seeding keratinocytes on a fibroblast-derived tissue sheet before its detachment
from the culture plate. Four days following keratinocyte seeding, the resulting tissue was stacked on two
fibroblast-derived tissue sheets and cultured at the air–liquid interface for 10 days. The resulting total production
time was 31 days. An alternative method adapted to more contractile fibroblasts was also developed. It consisted
in adding a peripheral frame before seeding fibroblasts in the culture plate. SASSs produced by both new methods
shared similar histology, contractile behavior in vitro and in vivo evolution after grafting onto mice when
compared with SASSs produced by the 45-day standard method. In conclusion, the new approach for the production
of high-quality human skin substitutes should allow an earlier autologous grafting for the treatment of
severely burned patients
REM1.3's phospho-status defines its plasma membrane nanodomain organization and activity in restricting PVX cell-to-cell movement
Plants respond to pathogens through dynamic regulation of plasma membrane-bound signaling pathways. To date, how the plant plasma membrane is involved in responses to viruses is mostly unknown. Here, we show that plant cells sense the Potato virus X (PVX) COAT PROTEIN and TRIPLE GENE BLOCK 1 proteins and subsequently trigger the activation of a membrane-bound calcium-dependent kinase. We show that the Arabidopsis thaliana CALCIUM-DEPENDENT PROTEIN KINASE 3-interacts with group 1 REMORINs in vivo, phosphorylates the intrinsically disordered N-terminal domain of the Group 1 REMORIN REM1.3, and restricts PVX cell-to-cell movement. REM1.3’s phospho-status defines its plasma membrane nanodomain organization and is crucial for REM1.3-dependent restriction of PVX cell-to-cell movement by regulation of callose deposition at plasmodesmata. This study unveils plasma membrane nanodomain-associated molecular events underlying the plant immune response to viruses
Long-Range Enhancer Associated with Chromatin Looping Allows AP-1 Regulation of the Peptidylarginine Deiminase 3 Gene in Differentiated Keratinocyte
Transcription control at a distance is a critical mechanism, particularly for contiguous genes. The peptidylarginine deiminases (PADs) catalyse the conversion of protein-bound arginine into citrulline (deimination), a critical reaction in the pathophysiology of multiple sclerosis, Alzheimer's disease and rheumatoid arthritis, and in the metabolism of the major epidermal barrier protein filaggrin, a strong predisposing factor for atopic dermatitis. PADs are encoded by 5 clustered PADI genes (1p35-6). Unclear are the mechanisms controlling the expression of the gene PADI3 encoding the PAD3 isoform, a strong candidate for the deimination of filaggrin in the terminally differentiating epidermal keratinocyte. We describe the first PAD Intergenic Enhancer (PIE), an evolutionary conserved non coding segment located 86-kb from the PADI3 promoter. PIE is a strong enhancer of the PADI3 promoter in Ca2+-differentiated epidermal keratinocytes, and requires bound AP-1 factors, namely c-Jun and c-Fos. As compared to proliferative keratinocytes, calcium stimulation specifically associates with increased local DNase I hypersensitivity around PIE, and increased physical proximity of PIE and PADI3 as assessed by Chromosome Conformation Capture. The specific AP-1 inhibitor nordihydroguaiaretic acid suppresses the calcium-induced increase of PADI3 mRNA levels in keratinocytes. Our findings pave the way to the exploration of deimination control during tumorigenesis and wound healing, two conditions for which AP-1 factors are critical, and disclose that long-range transcription control has a role in the regulation of the gene PADI3. Since invalidation of distant regulators causes a variety of human diseases, PIE results to be a plausible candidate in association studies on deimination-related disorders or atopic disease
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