Mitochondrial Dynamics and Motility Inside Living Vascular Endothelial Cells: Role of Bioenergetics
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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 (ΔΨm), 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.
KeywordsMitochondrial fusion/fission Mitochondrial motility Endothelial function Fluorescence microscopy Digital image processing Mathematical analysis Object tracking
The authors would like to thank Mr. C. J. Lloyd, undergraduate researcher, for his assistance with data analysis. This work was supported by National Institutes of Health (NIH) grant HL106392 to B. R. Alevriadou and an American Heart (AHA) predoctoral fellowship to R. J. Giedt. D. R. Pfeiffer was supported by the Ellie Kovalck Charitable Trust. A. Matzavinos was supported in part by the Mathematical Biosciences Institute at the Ohio State University and National Science Foundation (NSF) grant DMS-093164. C.-Y. Kao was supported in part by NSF grant DMS-0811003 and an Alfred P. Sloan Fellowship.
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