Abstracts
Résumé
Les propriétés mécaniques des cellules jouent un rôle prépondérant dans de nombreux événements de la vie cellulaire comme le développement embryonnaire, la formation des tissus ou encore le développement des métastases. La migration cellulaire est en partie caractérisée par des interactions mécaniques. Ainsi, les forces de traction qu’exercent les cellules sur leur environnement impliquent, en parallèle, une réorganisation dynamique des processus d’adhérence et du cytosquelette interne de la cellule. Pour évaluer ces forces, un substrat a été développé, constitué d’un réseau forte densité de micro-piliers déformables sur lequel se déplacent les cellules. Cette surface est fabriquée par des méthodes de lithographie empruntées à la micro-électronique. Les piliers mesurent environ un micromètre et sont en caoutchouc, donc suffisamment déformables pour fléchir sous l’effet des forces exercées par les cellules. L’analyse au microscope des déflexions individuelles de chaque pilier a permis de quantifier en temps réel les forces locales que des cellules exercent sur leur substrat lors de leurs processus d’adhérence et de dissociation.
Summary
Mechanical forces play an important role in various cellular functions, such as tumor metastasis, embryonic development or tissue formation. Cell migration involves dynamics of adhesive processes and cytoskeleton remodelling, leading to traction forces between the cells and their surrounding extracellular medium. To study these mechanical forces, a number of methods have been developed to calculate tractions at the interface between the cell and the substrate by tracking the displacements of beads or microfabricated markers embedded in continuous deformable gels. These studies have provided the first reliable estimation of the traction forces under individual migrating cells. We have developed a new force sensor made of a dense array of soft micron-size pillars microfabricated using microelectronics techniques. This approach uses elastomeric substrates that are micropatterned by using a combination of hard and soft lithography. Traction forces are determined in real time by analyzing the deflections of each micropillar with an optical microscope. Indeed, the deflection is directly proportional to the force in the linear regime of small deformations. Epithelial cells are cultured on our substrates coated with extracellular matrix protein. First, we have characterized temporal and spatial distributions of traction forces of a cellular assembly. Forces are found to depend on their relative position in the monolayer : the strongest deformations are always localized at the edge of the islands of cells in the active areas of cell protrusions. Consequently, these forces are quantified and correlated with the adhesion/scattering processes of the cells.
Appendices
Références
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