title: Measuring the micromechanical properties of embryonic tissues.
abstract: Local mechanical properties play an important role in directing embryogenesis, both at the cell (differentiation, migration) and tissue level (force transmission, organ formation, morphogenesis). Measuring them is a challenge as embryonic tissues are small (μm to mm) and soft (0.1-10 kPa). We describe here how glass fiber cantilevers can be fabricated, calibrated and used to apply small forces (0.1-10 μN), measure contractile activity and assess the bulk tensile elasticity of embryonic tissue. We outline how pressure (hydrostatic or osmotic) can be applied to embryonic tissue to quantify stiffness anisotropy. These techniques can be assembled at low cost and with a minimal amount of equipment. We then present a protocol to prepare tissue sections for local elasticity and adhesion measurements using the atomic force microscope (AFM). We compare AFM nanoindentation maps of native and formaldehyde fixed embryonic tissue sections and discuss how the local elastic modulus obtained by AFM compares to that obtained with other bulk measurement methods. We illustrate all of the techniques presented on the specific example of the chick embryonic digestive tract, emphasizing technical issues and common pitfalls. The main purpose of this report is to make these micromechanical measurement techniques accessible to a wide community of biologists and biophysicists.
authors.affiliation: Laboratoire Matière et Systèmes Complexes, Université Paris Diderot/CNRS UMR 7057, 10 rue Alice Domon et Léonie Duquet, 75013 Paris, France. Electronic address: nicolas.chevalier@univ-paris-diderot.fr.
authors.forename: Nicolas R
authors.initials: NR
authors.lastname: Chevalier
authors.affiliation: UMR144, CNRS-Institut Curie, Paris, France; Université Pierre et Marie Curie, UPMC, Paris, France; Université Paris-Est, UPEC, Faculté de Médecine, Créteil, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Gazquez
authors.affiliation: UMR144, CNRS-Institut Curie, Paris, France; Université Pierre et Marie Curie, UPMC, Paris, France; Université Paris-Est, UPEC, Faculté de Médecine, Créteil, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Dufour
authors.affiliation: Laboratoire Matière et Systèmes Complexes, Université Paris Diderot/CNRS UMR 7057, 10 rue Alice Domon et Léonie Duquet, 75013 Paris, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Fleury
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002642:Chick Embryo; D055119:Elastic Modulus; D041981:Gastrointestinal Tract / Q000502:physiology*; D018625:Microscopy, Atomic Force
keywords: Atomic force microscopy; Cantilever; Embryo; Mechanics; Stiffness; Young modulus