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Mechanotransduction and strain amplification in osteocyte cell processes.
Yuefeng Han1, Stephen C Cowin, Mitchell B Schaffler
1Departments of Biomedical and Mechanical Engineering, City College and Graduate School of the City University of New York, New York, NY 10031, USA.
Summary
Bone cells (osteocytes) may be excited by mechanical loading through a strain-amplification mechanism. Our refined model shows amplified intracellular strains, offering a new hypothesis for osteocyte mechanotransduction.
Area of Science:
- Biomechanical Engineering
- Cellular Biology
- Orthopedics
Background:
- Bone tissue strains from locomotion are typically too small to directly trigger intracellular responses in osteocytes.
- A prior model suggested fluid flow in the lacunar-canalicular network amplifies strains on the cytoskeleton.
Purpose of the Study:
- To refine a computational model of osteocyte mechanotransduction using updated ultrastructural data.
- To investigate strain amplification within the osteocyte cell process and its tethering elements.
Main Methods:
- Developed a realistic 3D model of the osteocyte cell process and its tethers.
- Incorporated finite flexural rigidity (EI) of tethering elements.
- Applied large-deformation "elastica" theory to predict cytoskeletal strain.
Main Results:
- The refined model predicts a stiffer cell process compared to previous models.
- Predicted hoop strains exceeding 0.5% for tissue strains of 1,000 microstrain at 1 Hz.
- Predicted significant hoop strain (>0.5%) for tissue strains above 250 microstrain at frequencies >10 Hz.
Conclusions:
- The strain-amplification model, incorporating detailed ultrastructural and mechanical properties, offers a plausible mechanism for osteocyte excitation.
- This refined model provides a more likely hypothesis for osteocyte mechanotransduction than the fluid-shear hypothesis.