title: Quantification of surface tension and internal pressure generated by single mitotic cells.
abstract: During mitosis, adherent cells round up, by increasing the tension of the contractile actomyosin cortex while increasing the internal hydrostatic pressure. In the simple scenario of a liquid cell interior, the surface tension is related to the local curvature and the hydrostatic pressure difference by Laplace's law. However, verification of this scenario for cells requires accurate measurements of cell shape. Here, we use wedged micro-cantilevers to uniaxially confine single cells and determine confinement forces while concurrently determining cell shape using confocal microscopy. We fit experimentally measured confined cell shapes to shapes obeying Laplace's law with uniform surface tension and find quantitative agreement. Geometrical parameters derived from fitting the cell shape, and the measured force were used to calculate hydrostatic pressure excess and surface tension of cells. We find that HeLa cells increase their internal hydrostatic pressure excess and surface tension from ≈ 40 Pa and 0.2 mNm(-1) during interphase to ≈ 400 Pa and 1.6 mNm(-1) during metaphase. The method introduced provides a means to determine internal pressure excess and surface tension of rounded cells accurately and with minimal cellular perturbation, and should be applicable to characterize the mechanical properties of various cellular systems.
authors.affiliation: 1] Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany [2] Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Fischer-Friedrich
authors.affiliation: Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Hyman
authors.affiliation: Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Jülicher
authors.affiliation: Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule Zürich, Mattenstr. 26, 4058 Basel, Switzerland.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Müller
authors.affiliation: Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule Zürich, Mattenstr. 26, 4058 Basel, Switzerland.
authors.forename: Jonne
authors.initials: J
authors.lastname: Helenius
mesh_terms: D048430:Cell Shape; D006367:HeLa Cells; D006801:Humans; D006874:Hydrostatic Pressure; D008938:Mitosis; D059010:Single-Cell Analysis; D013500:Surface Tension