Modeling the Mechanics of Tethers Pulled From the Cochlear Outer Hair Cell Membrane

Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.
Journal of Biomechanical Engineering (Impact Factor: 1.78). 07/2008; 130(3):031007. DOI: 10.1115/1.2907758
Source: PubMed


Cell membrane tethers are formed naturally (e.g., in leukocyte rolling) and experimentally to probe membrane properties. In cochlear outer hair cells, the plasma membrane is part of the trilayer lateral wall, where the membrane is attached to the cytoskeleton by a system of radial pillars. The mechanics of these cells is important to the sound amplification and frequency selectivity of the ear. We present a modeling study to simulate the membrane deflection, bending, and interaction with the cytoskeleton in the outer hair cell tether pulling experiment. In our analysis, three regions of the membrane are considered: the body of a cylindrical tether, the area where the membrane is attached and interacts with the cytoskeleton, and the transition region between the two. By using a computational method, we found the shape of the membrane in all three regions over a range of tether lengths and forces observed in experiments. We also analyze the effects of biophysical properties of the membrane, including the bending modulus and the forces of the membrane adhesion to the cytoskeleton. The model's results provide a better understanding of the mechanics of tethers pulled from cell membranes.

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    • "Accurate characterization of the mechanical properties of individual cells within the organ of Corti should thus help in the construction of more accurate models of cochlear mechanics [1]. Whilst attention has been given to the mechanical properties of hair cells [8], [9], [10], [11], [12], [13], [14], [15], [16] and their mechanosensory bundles [17], [18], a systematic analysis of supporting cells has not been undertaken. "
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    PLoS ONE 11/2012; 7(11):e49338. DOI:10.1371/journal.pone.0049338 · 3.23 Impact Factor
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    ABSTRACT: Tethers are thin membrane tubes that can be formed when relatively small and localized forces are applied to cellular membranes and lipid bilayers. Tether pulling experiments have been used to better understand the fine membrane properties. These include the interaction between the plasma membrane and the underlying cytoskeleton, which is an important factor affecting membrane mechanics. We use a computational method aimed at the interpretation and design of tether pulling experiments in cells with a strong membrane-cytoskeleton attachment. In our model, we take into account the detailed information in the topology of bonds connecting the plasma membrane and the cytoskeleton. We compute the force-dependent piecewise membrane deflection and bending as well as modes of stored energy in three major regions of the system: body of the tether, membrane-cytoskeleton attachment zone, and the transition zone between the two. We apply our method to three cells: cochlear outer hair cells (OHCs), human embryonic kidney (HEK) cells, and Chinese hamster ovary (CHO) cells. OHCs have a special system of pillars connecting the membrane and the cytoskeleton, and HEK and CHO cells have the membrane-cytoskeleton adhesion arrangement via bonds (e.g., PIP2), which is common to many other cells. We also present a validation of our model by using experimental data on CHO and HEK cells. The proposed method can be an effective tool in the analyses of experiments to probe the properties of cellular membranes.
    Physical Review E 10/2009; 80(4 Pt 1):041905. DOI:10.1103/PhysRevE.80.041905 · 2.29 Impact Factor
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