Mitochondrial Dynamics and Motility Inside Living Vascular Endothelial Cells: Role of Bioenergetics

Department of Biomedical Engineering, The Ohio State University, 1080 Carmack Road, Columbus, OH 43210, USA.
Annals of Biomedical Engineering (Impact Factor: 3.23). 04/2012; 40(9):1903-16. DOI: 10.1007/s10439-012-0568-6
Source: PubMed


The mitochondrial network is dynamic with conformations that vary between a tubular continuum and a fragmented state. The equilibrium between mitochondrial fusion/fission, as well as the organelle motility, determine network morphology and ultimately mitochondrial/cell function. Network morphology has been linked with the energy state in different cell types. In this study, we examined how bioenergetic factors affect mitochondrial dynamics/motility in cultured vascular endothelial cells (ECs). ECs were transduced with mitochondria-targeted green fluorescent protein (mito-GFP) and exposed to inhibitors of oxidative phosphorylation (OXPHOS) or ATP synthesis. Time-lapse fluorescence videos were acquired and a mathematical program that calculates size and speed of each mitochondrial object at each time frame was developed. Our data showed that inner mitochondrial membrane potential (ΔΨ(m)), ATP produced by glycolysis, and, to a lesser degree, ATP produced by mitochondria are critical for maintaining the mitochondrial network, and different metabolic stresses induce distinct morphological patterns (e.g., mitochondrial depolarization is necessary for "donut" formation). Mitochondrial movement, characterized by Brownian diffusion with occasional bursts in displacement magnitude, was inhibited under the same conditions that resulted in increased fission. Hence, imaging/mathematical analysis shed light on the relationship between bioenergetics and mitochondrial network morphology; the latter may determine EC survival under metabolic stress.

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    • "Interestingly, glycolysis-derived ATP is in part dedicated to maintaining the EC mitochondrial network [138], presumably because these organelles are essential for EC homeostasis by controlling other processes than metabolism as well. Indeed, mitochondria in ECs mediate Ca2+ storage for its use in signaling for a wide range of physiological cell processes [119]. "
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    • "A more advanced method is to generate a 3D representation of the mitochondria from the z-stack and performing a 3D analysis of the mitochondrial objects. Although technically more demanding than 2D procedures, attempts to analyze mitochondria in 3D appeared promising in studies of mitochondrial shape and network properties [6], [22], [25], [30]–[32]. However, to the best of our knowledge, none of the published 3D strategies involves combined and integrative assessment of mitochondrial shape and network properties. "
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