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. 2021 Nov 11:9:753805.
doi: 10.3389/fbioe.2021.753805. eCollection 2021.

Mechanical Properties of Isolated Primary Cilia Measured by Micro-tensile Test and Atomic Force Microscopy

Tien-Dung Do  1 , Jimuro Katsuyoshi  1 , Haonai Cai  1 , Toshiro Ohashi  2
Affiliations

Mechanical Properties of Isolated Primary Cilia Measured by Micro-tensile Test and Atomic Force Microscopy

Tien-Dung Do et al. Front Bioeng Biotechnol. .

Abstract

Mechanotransduction is a well-known mechanism by which cells sense their surrounding mechanical environment, convert mechanical stimuli into biochemical signals, and eventually change their morphology and functions. Primary cilia are believed to be mechanosensors existing on the surface of the cell membrane and support cells to sense surrounding mechanical signals. Knowing the mechanical properties of primary cilia is essential to understand their responses, such as sensitivity to mechanical stimuli. Previous studies have so far conducted flow experiments or optical trap techniques to measure the flexural rigidity EI (E: Young's modulus, I: second moment of inertia) of primary cilia; however, the flexural rigidity is not a material property of materials and depends on mathematical models used in the determination, leading to a discrepancy between studies. For better characterization of primary cilia mechanics, Young's modulus should be directly and precisely measured. In this study, the tensile Young's modulus of isolated primary cilia is, for the first time, measured by using an in-house micro-tensile tester. The different strain rates of 0.01-0.3 s-1 were applied to isolated primary cilia, which showed a strain rate-dependent Young's modulus in the range of 69.5-240.0 kPa on average. Atomic force microscopy was also performed to measure the local Young's modulus of primary cilia, showing the Young's modulus within the order of tens to hundreds of kPa. This study could directly provide the global and local Young's moduli, which will benefit better understanding of primary cilia mechanics.

Keywords: AFM test; isolated primary cilia; micro-tensile test; viscoelasticity; young’s modulus.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
(A) Experimental setup of the micro-tensile test. K: the spring constant, d: the displacement of the force-sensing cantilever, L 0 and L p : the length of a primary cilium before and after stretching, respectively (B) Experimental setup of the AFM test (C) The global Young’s modulus E stretching and the local Young’s modulus E AFM of a primary cilium.
FIGURE 2
FIGURE 2
(A) Cell images with primary cilia (green), actin filaments (red), and nuclei (blue) (B) Isolated primary cilia after ultracentrifugation (white arrows). Scale bar: 10 µm.
FIGURE 3
FIGURE 3
TEM images (A) Longitudinal section (B) Cross-section of primary cilia.
FIGURE 4
FIGURE 4
Tensile stretching of primary cilia (A) Before stretching (B) During stretching, d: the displacement of the force-sensing cantilever, L 0 and L p : the length of a primary cilium before and after stretching. Scale bar: 10 µm.
FIGURE 5
FIGURE 5
(A) Relationship between force and strain of primary cilia at different strain rates from 0.01 to 0.3 s−1 and the least squares fitting (B) The Young’s modulus determined at different strain rates from 0.01 to 0.3 s−1.
FIGURE 6
FIGURE 6
Global fitting of the SLS model and experimental data sets.
FIGURE 7
FIGURE 7
Comparison of global E stretching and local E AFM .
FIGURE 8
FIGURE 8
(A) Relationship of applied voltage and indentation depth (B) The Young’s modulus of primary cilia at different applied voltage.
See this image and copyright information in PMC

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