title: Analysis of mitochondrial mechanical dynamics using a confocal fluorescence microscope with a bent optical fibre.
abstract: The cells in the cardiovascular system are constantly subjected to mechanical forces created by blood flow and the beating heart. The effect of forces on cells has been extensively investigated, but their effect on cellular organelles such as mitochondria remains unclear. We examined the impact of nano-Newton forces on mitochondria using a bent optical fibre (BOF) with a flat-ended tip (diameter exceeding 2 μm) and a confocal fluorescence microscope. By indenting a single mitochondrion with the BOF tip, we found that the mitochondrial elastic modulus was proportional to the (-1/2) power of the mitochondrial radius in the 9.6-115 kPa range. We stained the mitochondria with a potential-metric dye (TMRE) and measured the changes in TMRE fluorescence intensity. We confirmed that more active mitochondria exhibit a higher frequency of repetitive transient depolarization. The same trend was observed at forces lower than 50 nN. We further showed that the depolarization frequency of mitochondria decreases under an extremely large force (nearly 100 nN). We conclude that mitochondrial function is affected by physical environmental factors, such as external forces at the nano-Newton level.
authors.affiliation: Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: Yongbo
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Honda
authors.affiliation: Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Iwami
authors.affiliation: Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ohta
authors.affiliation: Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Umeda
mesh_terms: D055119:Elastic Modulus; D008856:Microscopy, Fluorescence / Q000295:instrumentation* / Q000379:methods; D008928:Mitochondria / Q000502:physiology* / Q000648:ultrastructure*; D055100:Optical Fibers
keywords: Bent optical fibre; CLSM; confocal fluorescence microscope; elastic moduli; flat-ended tip; mitochondria; mitochondrial activity