Assemblages et études de la différenciation cellulaire des cellules souches sur des surfaces de géométrie et chimie contrôlées

Abstract : The cell responds to the physical constraints exerted by its environment by a set of mechanisms grouped under the term of mechanotransduction. These processes involve the molecules involved in cell adhesion, the cytoskeleton and the nucleus. These environmental constraints, whether related to the rigidity of the support, to its topography or to the nature of its surface chemistry, will modulate the cellular morphology and impact the behavior of the cell. In order to study this influence of the support, we have seeded bone marrow mesenchymal stem cells from a primary culture on virgin mica surfaces or functionalized homogeneously with natural molecules (fibronectin and the cyclic RGD peptide) or with polyelectrolyte multilayers (five cycles of Chitosan/PAA or Chitosan/PSS). We then studied the morphology, proliferation and differentiation of these cells after 12 days of culture. As a result, bone marrow mesenchymal stem cells adhere to all surfaces, whether treated or not, and although they are less spread on virgin surfaces, they adopt a fibroblastic type morphology similar to their physiological phenotype. Their percentage of confluence varies significantly depending on the surface treatment used. Indeed the maximum confluence was observed for the surfaces grafted with fibronectin (93.25 ± 2.75%) whereas the surfaces treated with the polyelectrolyte multilayers have much lower confluence percentages (61.00 ± 4.08% for the chitosan/PAA couple) and 54.75 ± 1.75% for the Chitosan/PSS couple), mainly due to cell latency at the beginning of culture. Finally, cells cultured on our surfaces do not respond to any of the three Oil Red O, Alcian Blue or Alizarin Red S stains, suggesting a lack of differentiation in the adipogenic, chondrogenic or osteogenic pathways induced by these surfaces. Thus, the control of the support chemistry alone does not allow control of cell differentiation. This study paves the way for the next step in which the influence of controlled chemistry and geometry media will be studied. Similarly, the E. coli strain (pathogenic bacterium) responds to the physical and chemical constraints imposed on it. These constraints, whether related to the topography or the nature of surface chemistry, involve natural molecules involved in the behavior of bacteria and their morphology, in particular their size. To study this impact, we contacted E.coli strain E2146 with virgin mica surfaces or treated homogeneously or patterned with natural molecules (fibronectin and cyclic RGD peptide). Then we studied the recovery rate and the size of the bacteria. As a result, the bacteria adhere to all surfaces although adhesion is less on virgin mica surfaces. Their recovery rate varies significantly for a given area. Indeed, the recovery rate and the maximum size are observed on patterned surfaces grafted with fibronectin which proves their effectiveness and the impact they have on the behavior of E. coli. We have therefore demonstrated in this thesis the influence of surface properties on the growth of living cells such as stem cells or bacteria.
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Batoul Hamie. Assemblages et études de la différenciation cellulaire des cellules souches sur des surfaces de géométrie et chimie contrôlées. Science des matériaux [cond-mat.mtrl-sci]. Université de Lorraine; Université libanaise, 2018. Français. ⟨NNT : 2018LORR0320⟩. ⟨tel-02130679⟩

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