The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: I have read the journal's policy, and the authors of this manuscript have the following competing interests: Dr. PS, CT, and FGvdG were funded by LipidX and SNSF. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All relevant data are within the paper and its Supporting Information files.įunding: This work was supported by a grant from the Swiss National Science Foundation (SNSF) and the Swiss SystemsX.ch initiative evaluated by the Swiss National Science Foundation (LipidX). Received: SeptemAccepted: NovemPublished: December 19, 2019Ĭopyright: © 2019 Sandoz et al. Schmid, UT Southwestern Medical Center, UNITED STATES PLoS Biol 17(12):Īcademic Editor: Sandra L. This work demonstrates that HTM gives access to an uncharted field of biological dynamics and describes a unique set of simple computer-vision strategies that can be broadly used to quantify HTM images.Ĭitation: Sandoz PA, Tremblay C, van der Goot FG, Frechin M (2019) Image-based analysis of living mammalian cells using label-free 3D refractive index maps reveals new organelle dynamics and dry mass flux. We finally took advantage of the capacity of HTM to capture the motion of many organelles at the same time to report a multiorganelle spinning phenomenon and study its dynamic properties using pattern matching and homography analysis. We could observe the shape and dry mass dynamics of LDs, endocytic structures, and entire cells’ division that have so far, to the best of our knowledge, been out of reach. To go further, we developed a computer-vision strategy using FIJI, CellProfiler3 (CP3), and custom code that allows us to use the fine images obtained by HTM in quantitative approaches. By combining HTM with epifluorescence, we demonstrate that mammalian cellular organelles such as lipid droplets (LDs) and mitochondria show specific RI 3D patterns. Holo-tomographic microscopy (HTM) is a label-free microscopy method reporting the fine changes of a cell’s refractive indices (RIs) in three dimensions at high spatial and temporal resolution.

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