Finite Element Analysis of Osteocytes Mechanosensitivity Under Simulated Microgravity

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Abstract

It was found that the mechanosensitivity of osteocytes could be altered under simulated microgravity. However, how the mechanical stimuli as the biomechanical origins cause the bioresponse in osteocytes under microgravity is unclear yet. Computational studies may help us to explore the mechanical deformation changes of osteocytes under microgravity. Here in this paper, we intend to use the computational simulation to investigate the mechanical behavior of osteocytes under simulated microgravity. In order to obtain the shape information of osteocytes, the biological experiment was conducted under simulated microgravity prior to the numerical simulation The cells were rotated by a clinostat for 6 hours or 5 days and fixed, the cytoskeleton and the nucleus were immunofluorescence stained and scanned, and the cell shape and the fluorescent intensity were measured from fluorescent images to get the dimension information of osteocytes The 3D finite element (FE) cell models were then established based on the scanned image stacks. Several components such as the actin cortex, the cytoplasm, the nucleus, the cytoskeleton of F-actin and microtubules were considered in the model. The cell models in both 6 hours and 5 days groups were then imposed by three magnitudes (0.5, 10 and 15 Pa) of simulating fluid shear stress, with cell total displacement and the internal discrete components deformation calculated. The results showed that under the simulated microgravity: (1) the nuclear area and height statistically significantly increased, which made the ratio of membrane-cortex height to nucleus height statistically significantly decreased; (2) the fluid shear stress-induced maximum displacements and average displacements in the whole cell decreased, with the deformation decreasing amplitude was largest when exposed to 1.5Pa of fluid shear stress; (3) the fluid shear stress-induced deformation of cell membrane-cortex and cytoskeleton decreased, while the fluid shear stress-induced deformation of nucleus increased. The results suggested the mechanical behavior of whole osteocyte cell body was suppressed by simulated microgravity, and this decrement was enlarged with either the increasing amplitude of fluid shear stress or the duration of simulated microgravity. What’s more, the mechanical behavior of membrane-cortex and cytoskeleton was suppressed by the simulated microgravity, which indicated the mechanotransduction process in the cell body may be further inhibited. On the contrary, the cell nucleus deformation increased under simulated microgravity, which may be related to either the decreased amount of cytoskeleton or the increased volume occupied proportion of nucleus in whole cell under the simulated microgravity. The numerical results supported our previous biological experiments, and showed particularly affected cellular components under the simulated microgravity. The computational study here may help us to better understand the mechanism of mechanosensitivity changes in osteocytes under simulated microgravity, and further to explore the mechanism of the bone loss in space flight.

Keywords

Finite element Osteocytes Mechanical deformation Simulated microgravity 

Notes

Acknowledgements

This work was funded by grants from the National Natural Science Foundation of China (No. 11472033 and No.11421202), the 111 Project (No. B13003), the National Key Research and Development Plan (2016YFC1101101), and the Third Young Elite Scientist Sponsorship Program by China Association for Science and Technology.

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Copyright information

© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Biological Science and Medical EngineeringBeihang UniversityBeijingChina
  2. 2.Key Laboratory for Biomechanics and Mechanobiology of Ministry of EducationBeihang UniversityBeijingChina
  3. 3.Beijing Advanced Innovation Center for Biomedical EngineeringBeihang UniversityBeijingChina
  4. 4.Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent ControlTianjin University of TechnologyTianjinChina
  5. 5.Beijing Key Laboratory of Rehabilitation Technical Aids for Old-Age DisabilityNational Research Center for Rehabilitation Technical AidsBeijingChina

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