Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/5258

Title

Mitochondrial dynamics in chondrocytes and their connection to the mechanical properties of the cytoplasm

Author(s)

Bomzon, Ze'ev;  Knight, Martin M.;  Bader, Daniel L.;  Kimmel, Eitan

Abstract

Background: The motion and redistribution of intracellular organelles is a fundamental process in cells. Organelle motion is a complex phenomenon that depends on a large number of variables including the shape of the organelle, the type of motors with which the organelles are associated, and the mechanical properties of the cytoplasm. This paper presents a study that characterizes the diffusive motion of mitochondria in chondrocytes seeded in agarose constructs and what this implies about the mechanical properties of the cytoplasm. Method of approach: Images showing mitochondrial motion in individual cells at 30 s intervals for 15 min were captured with a confocal microscope. Digital image correlation was used to quantify the motion of the mitochondria, and the mean square displacement (MSD) was calculated. Statistical tools for testing whether the characteristic motion of mitochondria varied throughout the cell were developed. Calculations based on statistical mechanics were used to establish connections between the measured MSDs and the mechanical nature of the cytoplasm. Results: The average MSD of the mitochondria varied with time according to a power law with the power term greater than 1, indicating that mitochondrial motion can be viewed as a combination of diffusion and directional motion. Statistical analysis revealed that the motion of the mitochondria was not uniform throughout the cell, and that the diffusion coefficient may vary by over 50%, indicating intracellular heterogeneity. High correlations were found between movements of mitochondria when they were less than 2 µm apart. The correlation is probably due to viscoelastic properties of the cytoplasm. Theoretical analysis based on statistical mechanics suggests that directed diffusion can only occur in a material that behaves like a fluid on large time scales. Conclusions: The study shows that mitochondria in different regions of the cell experience different characteristic motions. This suggests that the cytoplasm is a heterogeneous viscoelastic material. The study provides new insight into the motion of mitochondria in chondrocytes and its connection with the mechanical properties of the cytoplasm.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Engineering and Industrial Sciences. Centre for Micro-Photonics

Source

Journal of Biomechanical Engineering, Vol. 128, no. 5 (2006), p. 674-679

Publication year

2006

Keyword(s)

Cell mechanics;  Chondrocytes;  Diffusion;  Intracellular transport;  Microrheology;  Mitochondria

Publisher

ASME International

Format

674-679

ISSN

0148-0731

Publisher URL

http://dx.doi.org/10.1115/1.2246239

Copyright

Copyright © 2006 by ASME.

Peer reviewed