Personne :
Lapointe, Marc

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Lapointe
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Marc
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Faculté des sciences et de génie, Université Laval
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Voici les éléments 1 - 4 sur 4
  • Publication
    Accès libre
    Temporal changes in gene expression profile during mature adipocyte dedifferentiation
    (Hindawi Publishing Corporation, 2017-03-19) Guénard, Frédéric; Biron, Simon; Lapointe, Marc; Vohl, Marie-Claude; Côté, Julie Anne; Lessard, Julie.; Tchernof, André
    Objective. To characterize changes in gene expression profile during human mature adipocyte dedifferentiation in ceiling culture. Methods. Subcutaneous (SC) and omental (OM) adipose tissue samples were obtained from 4 participants paired for age and BMI. Isolated adipocytes were dedifferentiated in ceiling culture. Gene expression analysis at days 0, 4, 7, and 12 of the cultures was performed using Affymetrix Human Gene 2.0 STvi arrays. Hierarchical clustering according to similarity of expression changes was used to identify overrepresented functions. Results. Four clusters gathered genes with similar expression between day 4 to day 7 but decreasing expression from day 7 to day 12. Most of these genes coded for proteins involved in adipocyte functions (LIPE, PLIN1, DGAT2, PNPLA2, ADIPOQ, CEBPA, LPL, FABP4, SCD, INSR, and LEP). Expression of several genes coding for proteins implicated in cellular proliferation and growth or cell cycle increased significantly from day 7 to day 12 (WNT5A, KITLG, and FGF5). Genes coding for extracellular matrix proteins were differentially expressed between days 0, 4, 7, and 12 (COL1A1, COL1A2, and COL6A3, MMP1, and TGFB1). Conclusion. Dedifferentiation is associated with downregulation of transcripts encoding proteins involved in mature adipocyte functions and upregulation of genes involved in matrix remodeling, cellular development, and cell cycle.
  • Publication
    Accès libre
    Generation of human adipose stem cells through dedifferentiation of mature adipocytes in ceiling cultures
    (Verlag nicht ermittelbar, 2015-03-07) Lapointe, Marc; Biertho, Laurent; Nadeau, Mélanie; Côté, Julie Anne; Pelletier, Mélissa; Marceau, Simon; Lessard, Julie.; Tchernof, André
    Mature adipocytes have been recently shown to reverse their phenotype into fibroblast-like cells in vitro through a technique called ceiling culture. Mature adipocytes can also be isolated from fresh adipose tissue for depot-specific characterization of their function and metabolic properties. Here, we describe a well-established protocol to isolate mature adipocytes from adipose tissues using collagenase digestion, and subsequent steps to perform ceiling cultures. Briefly, adipose tissues are incubated in a Krebs-Ringer-Henseleit buffer containing collagenase to disrupt tissue matrix. Floating mature adipocytes are collected on the top surface of the buffer. Mature cells are plated in a T25-flask completely filled with media and incubated up-side down for a week. An alternative 6-well plate culture approach allows the characterization of adipocytes undergoing dedifferentiation. Adipocyte morphology drastically changes over time of culture. Immunofluorescence can be easily performed on slides cultivated in 6-well plate as demonstrated 65 by FABP4 immunofluorescence staining. FABP4 protein is present in mature adipocytes but down-regulated through dedifferentiation of fat cells. Mature adipocyte dedifferentiation may represent a new avenue for cell therapy and tissue engineering.
  • Publication
    Accès libre
    Temporal changes in gene expression profile during mature adipocyte dedifferentiation
    (Hindawi Publishing Corporation, 2017-03-19) Guénard, Frédéric; Biron, Simon; Lapointe, Marc; Vohl, Marie-Claude; Côté, Julie Anne; Lessard, Julie.; Tchernof, André
    Objective. To characterize changes in gene expression profile during human mature adipocyte dedifferentiation in ceiling culture. Methods. Subcutaneous (SC) and omental (OM) adipose tissue samples were obtained from 4 participants paired for age and BMI. Isolated adipocytes were dedifferentiated in ceiling culture. Gene expression analysis at days 0, 4, 7, and 12 of the cultures was performed using Affymetrix Human Gene 2.0 STvi arrays. Hierarchical clustering according to similarity of expression changes was used to identify overrepresented functions. Results. Four clusters gathered genes with similar expression between day 4 to day 7 but decreasing expression from day 7 to day 12. Most of these genes coded for proteins involved in adipocyte functions (LIPE, PLIN1, DGAT2, PNPLA2, ADIPOQ, CEBPA, LPL, FABP4, SCD, INSR, and LEP). Expression of several genes coding for proteins implicated in cellular proliferation and growth or cell cycle increased significantly from day 7 to day 12 (WNT5A, KITLG, and FGF5). Genes coding for extracellular matrix proteins were differentially expressed between days 0, 4, 7, and 12 (COL1A1, COL1A2, and COL6A3, MMP1, and TGFB1). Conclusion. Dedifferentiation is associated with downregulation of transcripts encoding proteins involved in mature adipocyte functions and upregulation of genes involved in matrix remodeling, cellular development, and cell cycle.
  • Publication
    Accès libre
    Lasers à fibre de puissance opérés en régime continu
    (2010) Lapointe, Marc; Piché, Michel
    Le présent projet de recherche porte sur les lasers à fibre de haute puissance opérés en régime continu. L’objectif premier est la conception et la réalisation d’un laser de 400 W de puissance de sortie utilisant une fibre dopée à l’ytterbium. La grande variété de lasers fabriqués au cours de ces travaux a permis l’étude des effets thermiques, des limitations en puissance et du comportement de la raie spectrale d’émission. L’étude comprend des simulations numériques caractérisant le comportement des lasers à fibre opérés en régime continu. Différentes configurations de lasers ont été expérimentées à une puissance de signal de 100 W. Les échanges de chaleur dans les fibres à double gaines ont été analysés pour contourner les difficultés engendrées par la grande puissance de ces lasers. Le concept de résistance de contact est amené pour expliquer l’élévation de température des fibres actives. Les travaux ont abouti à la réalisation de lasers monomodes de plus de 350 W de puissance de sortie, et cela, limités uniquement par la disponibilité des pompes. Parce que la photodégradation est la principale difficulté des lasers à fibre de puissance, plusieurs compromis, notamment sur le choix technologique des composants, ont été nécessaires pour atteindre les objectifs de puissance et de qualité de faisceau. Un outil pour prédire l’élargissement spectral des lasers à fibre de haute puissance a été développé. Il est montré que le mélange à quatre ondes élargit la raie d’émission de ces lasers. L’élargissement du spectre de sortie, selon une fonction de la puissance, a été vérifié expérimentalement dans diverses configurations d’oscillateur.