1
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Xu N, Qiao Q, Fang X, Wang G, An K, Jiang W, Li J, Xu Z. Solvatochromic Buffering Fluorescent Probe Resolves the Lipid Transport and Morphological Changes during Lipid Droplet Fusion by Super-Resolution Imaging. Anal Chem 2024; 96:4709-4715. [PMID: 38457637 DOI: 10.1021/acs.analchem.4c00292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2024]
Abstract
The varied functions of lipid droplets, which encompass the regulation of lipid and energy homeostasis, as well as their association with the occurrence of various metabolic diseases, are intricately linked to their dynamic properties. Super-resolution imaging techniques have emerged to decipher physiological processes and molecular mechanisms on the nanoscale. However, achieving long-term dynamic super-resolution imaging faces challenges due to the need for fluorescent probes with high photostability. This paper introduces LD-CF, a "buffering probe" for imaging lipid droplet dynamics using structured illumination microscopy (SIM). The polarity-sensitive LD-CF eliminates background fluorescence with a "cyan filter" strategy, enabling wash-free imaging of lipid droplets. In the fluorescent "off" state outside droplets, the probes act as a "buffering pool", replacing photobleached probes inside droplets and enabling photostable long-term SIM imaging. With this probe, three modes of lipid droplet fusion were observed, including the discovery of fusion from large to small lipid droplets. Fluorescence intensity tracking also revealed the direction of lipid transport during the lipid droplet fusion.
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Affiliation(s)
- Ning Xu
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- School of Chemistry, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
| | - Qinglong Qiao
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Xiangning Fang
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Guangying Wang
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Kai An
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Wenchao Jiang
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Jin Li
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Zhaochao Xu
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- School of Chemistry, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
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2
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Alemany M. The Metabolic Syndrome, a Human Disease. Int J Mol Sci 2024; 25:2251. [PMID: 38396928 PMCID: PMC10888680 DOI: 10.3390/ijms25042251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/29/2024] [Accepted: 01/31/2024] [Indexed: 02/25/2024] Open
Abstract
This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.
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Affiliation(s)
- Marià Alemany
- Faculty of Biology, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
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3
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Ganeva I, Lim K, Boulanger J, Hoffmann PC, Muriel O, Borgeaud AC, Hagen WJH, Savage DB, Kukulski W. The architecture of Cidec-mediated interfaces between lipid droplets. Cell Rep 2023; 42:112107. [PMID: 36800289 PMCID: PMC9989828 DOI: 10.1016/j.celrep.2023.112107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/14/2022] [Accepted: 01/30/2023] [Indexed: 02/18/2023] Open
Abstract
Lipid droplets (LDs) are intracellular organelles responsible for storing surplus energy as neutral lipids. Their size and number vary enormously. In white adipocytes, LDs can reach 100 μm in diameter, occupying >90% of the cell. Cidec, which is strictly required for the formation of large LDs, is concentrated at interfaces between adjacent LDs and facilitates directional flux of neutral lipids from the smaller to the larger LD. The mechanism of lipid transfer is unclear, in part because the architecture of interfaces between LDs remains elusive. Here we visualize interfaces between LDs by electron cryo-tomography and analyze the kinetics of lipid transfer by quantitative live fluorescence microscopy. We show that transfer occurs through closely apposed monolayers, is slowed down by increasing the distance between the monolayers, and follows exponential kinetics. Our data corroborate the notion that Cidec facilitates pressure-driven transfer of neutral lipids through two "leaky" monolayers between LDs.
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Affiliation(s)
- Iva Ganeva
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK; Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland
| | - Koini Lim
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Jerome Boulanger
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Patrick C Hoffmann
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Olivia Muriel
- Electron Microscopy Facility, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland; Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland
| | - Alicia C Borgeaud
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland
| | - Wim J H Hagen
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - David B Savage
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK.
| | - Wanda Kukulski
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK; Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland.
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4
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Pajić T, Todorović NV, Živić M, Nikolić SN, Rabasović MD, Clayton AHA, Krmpot AJ. Label-free third harmonic generation imaging and quantification of lipid droplets in live filamentous fungi. Sci Rep 2022; 12:18760. [PMID: 36335164 PMCID: PMC9637149 DOI: 10.1038/s41598-022-23502-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 11/01/2022] [Indexed: 11/07/2022] Open
Abstract
We report the utilization of Third-Harmonic Generation microscopy for label-free live cell imaging of lipid droplets in the hypha of filamentous fungus Phycomyces blakesleeanus. THG microscopy images showed bright spherical features dispersed throughout the hypha cytoplasm in control conditions and a transient increase in the number of bright features after complete nitrogen starvation. Colocalization analysis of THG and lipid-counterstained images disclosed that the cytoplasmic particles were lipid droplets. Particle Size Analysis and Image Correlation Spectroscopy were used to quantify the number density and size of lipid droplets. The two analysis methods both revealed an increase from 16 × 10-3 to 23 × 10-3 lipid droplets/µm2 after nitrogen starvation and a decrease in the average size of the droplets (range: 0.5-0.8 µm diameter). In conclusion, THG imaging, followed by PSA and ICS, can be reliably used for filamentous fungi for the in vivo quantification of lipid droplets without the need for labeling and/or fixation. In addition, it has been demonstrated that ICS is suitable for THG microscopy.
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Affiliation(s)
- Tanja Pajić
- grid.7149.b0000 0001 2166 9385Faculty of Biology, Institute of Physiology and Biochemistry, University of Belgrade, Studentski trg 16, Belgrade, 11158 Serbia
| | - Nataša V. Todorović
- grid.7149.b0000 0001 2166 9385Institute for Biological Research “Siniša Stanković”, University of Belgrade, National Institute of the Republic of Serbia, Bulevar Despota Stefana 142, Belgrade, 11000 Serbia
| | - Miroslav Živić
- grid.7149.b0000 0001 2166 9385Faculty of Biology, Institute of Physiology and Biochemistry, University of Belgrade, Studentski trg 16, Belgrade, 11158 Serbia
| | - Stanko N. Nikolić
- grid.7149.b0000 0001 2166 9385Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, Belgrade, 11080 Serbia
| | - Mihailo D. Rabasović
- grid.7149.b0000 0001 2166 9385Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, Belgrade, 11080 Serbia
| | - Andrew H. A. Clayton
- grid.1027.40000 0004 0409 2862Department of Physics and Astronomy, Optical Sciences Centre, School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Melbourne, VIC 3122 Australia
| | - Aleksandar J. Krmpot
- grid.7149.b0000 0001 2166 9385Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, Belgrade, 11080 Serbia
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5
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Schmitt S, Renzer G, Benrath J, Best A, Jiang S, Landfester K, Butt HJ, Simonutti R, Crespy D, Koynov K. Monitoring the Formation of Polymer Nanoparticles with Fluorescent Molecular Rotors. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c01132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sascha Schmitt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Galit Renzer
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Jennifer Benrath
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Andreas Best
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Shuai Jiang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Katharina Landfester
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Roberto Simonutti
- Department of Material Science, University Milano Bicocca, Via R Cozzi 55, I-20125 Milan, Italy
| | | | - Kaloian Koynov
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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6
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Jurgutis D, Jarockyte G, Poderys V, Dodonova-Vaitkuniene J, Tumkevicius S, Vysniauskas A, Rotomskis R, Karabanovas V. Exploring BODIPY-Based Sensor for Imaging of Intracellular Microviscosity in Human Breast Cancer Cells. Int J Mol Sci 2022; 23:ijms23105687. [PMID: 35628497 PMCID: PMC9143602 DOI: 10.3390/ijms23105687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 05/17/2022] [Accepted: 05/18/2022] [Indexed: 11/16/2022] Open
Abstract
BODIPY-based molecular rotors are highly attractive imaging tools for imaging intracellular microviscosity in living cells. In our study, we investigated the ability to detect the microviscosity of biological objects by using BDP-NO2 and BDP-H molecular rotors. We describe in detail the optical properties of BDP-NO2 and BDP-H molecular rotors in aqueous media with and without proteins, together with their accumulation dynamics and localization in live and fixed human breast cancer cells. Furthermore, we investigate the applicability of these molecules to monitor microviscosity in the organelles of human breast cancer cells by fluorescence lifetime imaging microscopy (FLIM). We demonstrate that the BDP-NO2 molecular rotor aggregates in aqueous media and is incompatible with live cell imaging. The opposite effect is observed with BDP-H which preserves its stability in aqueous media, diffuses through the plasma membrane and accumulates in lipid droplets (LDs) and the cytosol of both live and fixed MCF-7 and MDA-MB-231 cancer cells. Finally, by utilizing BDP-H we demonstrate that LD microviscosity is significantly elevated in more malignant MDA-MB-231 human breast cancer cells, as compared to MCF-7 breast cancer cells. Our findings demonstrate that BDP-H is a water-compatible probe that can be successfully applied to measure microviscosity in the LDs of living cells.
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Affiliation(s)
- Dziugas Jurgutis
- Biomedical Physics Laboratory, National Cancer Institute, P. Baublio St. 3b, 08406 Vilnius, Lithuania; (D.J.); (G.J.); (V.P.); (R.R.)
- State Research Institute Center for Physical Sciences and Technology, Sauletekio Ave. 3, 10257 Vilnius, Lithuania;
| | - Greta Jarockyte
- Biomedical Physics Laboratory, National Cancer Institute, P. Baublio St. 3b, 08406 Vilnius, Lithuania; (D.J.); (G.J.); (V.P.); (R.R.)
| | - Vilius Poderys
- Biomedical Physics Laboratory, National Cancer Institute, P. Baublio St. 3b, 08406 Vilnius, Lithuania; (D.J.); (G.J.); (V.P.); (R.R.)
| | - Jelena Dodonova-Vaitkuniene
- Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko St. 24, 03225 Vilnius, Lithuania; (J.D.-V.); (S.T.)
| | - Sigitas Tumkevicius
- Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko St. 24, 03225 Vilnius, Lithuania; (J.D.-V.); (S.T.)
| | - Aurimas Vysniauskas
- State Research Institute Center for Physical Sciences and Technology, Sauletekio Ave. 3, 10257 Vilnius, Lithuania;
| | - Ricardas Rotomskis
- Biomedical Physics Laboratory, National Cancer Institute, P. Baublio St. 3b, 08406 Vilnius, Lithuania; (D.J.); (G.J.); (V.P.); (R.R.)
| | - Vitalijus Karabanovas
- Biomedical Physics Laboratory, National Cancer Institute, P. Baublio St. 3b, 08406 Vilnius, Lithuania; (D.J.); (G.J.); (V.P.); (R.R.)
- Department of Chemistry and Bioengineering, Vilnius Gediminas Technical University, Sauletekio Ave. 11, 10223 Vilnius, Lithuania
- Correspondence:
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7
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Han C, Zhang ZH, Wang L, Chen XQ, Qu J, Liu K, Wang JY. Two reasonably designed polarity-viscosity sensitive fluorescent probes with large Stokes shift for lighting up lipid droplets in cells. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2021.113656] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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8
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Chen J, Wang C, Liu W, Qiao Q, Qi H, Zhou W, Xu N, Li J, Piao H, Tan D, Liu X, Xu Z. Stable Super‐Resolution Imaging of Lipid Droplet Dynamics through a Buffer Strategy with a Hydrogen‐Bond Sensitive Fluorogenic Probe. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202111052] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Jie Chen
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Chao Wang
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
- Fluorescence Research Group Singapore University of Technology and Design 8 Somapah Road Singapore 487372 Singapore
| | - Wenjuan Liu
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Qinglong Qiao
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Huan Qi
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Wei Zhou
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Ning Xu
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Jin Li
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Hailong Piao
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Davin Tan
- Fluorescence Research Group Singapore University of Technology and Design 8 Somapah Road Singapore 487372 Singapore
| | - Xiaogang Liu
- Fluorescence Research Group Singapore University of Technology and Design 8 Somapah Road Singapore 487372 Singapore
| | - Zhaochao Xu
- CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
- University of Chinese Academy of Sciences Beijing 100049 China
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9
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Chen J, Wang C, Liu W, Qiao Q, Qi H, Zhou W, Xu N, Li J, Piao H, Tan D, Liu X, Xu Z. Stable Super-Resolution Imaging of Lipid Droplet Dynamics through a Buffer Strategy with a Hydrogen-Bond Sensitive Fluorogenic Probe. Angew Chem Int Ed Engl 2021; 60:25104-25113. [PMID: 34519394 DOI: 10.1002/anie.202111052] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 09/02/2021] [Indexed: 11/10/2022]
Abstract
Although super-resolution imaging offers an opportunity to visualize cellular structures and organelles at the nanoscale level, cellular heterogeneity and unpredictability still pose a significant challenge in the dynamic imaging of live cells. It is thus vital to develop better-performing and more photostable probes for long-term super-resolution imaging. Herein, we report a probe, LD-FG, for imaging lipid droplet (LD) dynamics using structured illumination microscopy (SIM). LD-FG allows wash-free imaging of LDs, owing to a hydrogen-bond sensitive fluorogenic response. The replacement of photobleached LD-FG by intact probe molecules outside the LDs ensures the long-time stability of the fluorescence imaging. With this buffering fluorogenic probe, fast and unpredictable dynamic processes of LDs can be visualized. Using this probe, two LD coalescence modes were discovered. The dynamic imaging also allowed us to propose a new model of LD maturation during adipocyte differentiation, i.e., a fast LD coalescence followed by a slow ripening step. The excellent performance of LD-FG makes the buffer strategy an effective method for designing fluorescent probes for cell dynamic imaging.
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Affiliation(s)
- Jie Chen
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chao Wang
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China.,Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore, 487372, Singapore
| | - Wenjuan Liu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qinglong Qiao
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Huan Qi
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Wei Zhou
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Ning Xu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Jin Li
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hailong Piao
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Davin Tan
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore, 487372, Singapore
| | - Xiaogang Liu
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore, 487372, Singapore
| | - Zhaochao Xu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
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10
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Takei Y, Hirai R, Fukuda A, Miyazaki S, Shimada R, Okamatsu-Ogura Y, Saito M, Leproux P, Hisatake K, Kano H. Visualization of intracellular lipid metabolism in brown adipocytes by time-lapse ultra-multiplex CARS microspectroscopy with an onstage incubator. J Chem Phys 2021; 155:125102. [PMID: 34598561 DOI: 10.1063/5.0063250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We visualized a dynamic process of fatty acid uptake of brown adipocytes using a time-lapse ultra-broadband multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopic imaging system with an onstage incubator. Combined with the deuterium labeling technique, the intracellular uptake of saturated fatty acids was traced up to 9 h, a substantial advance over the initial multiplex CARS system, with an analysis time of 80 min. Characteristic metabolic activities of brown adipocytes, such as resistance to lipid saturation, were elucidated, supporting the utility of the newly developed system.
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Affiliation(s)
- Yuki Takei
- Department of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan
| | - Rie Hirai
- Laboratory of Gene Regulation, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Aya Fukuda
- Laboratory of Gene Regulation, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Shinichi Miyazaki
- Ph.D. Program in Humanics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
| | - Rintaro Shimada
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yuko Okamatsu-Ogura
- Laboratory of Biochemistry, Faculty of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, Hokkaido 060-0818, Japan
| | - Masayuki Saito
- Laboratory of Biochemistry, Faculty of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, Hokkaido 060-0818, Japan
| | - Philippe Leproux
- Institut de Recherche XLIM, UMR CNRS No. 7252, 123 Avenue Albert Thomas, 87060 Limoges Cedex, France
| | - Koji Hisatake
- Laboratory of Gene Regulation, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Hideaki Kano
- Department of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan
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11
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Lyu X, Wang J, Wang J, Yin YS, Zhu Y, Li LL, Huang S, Peng S, Xue B, Liao R, Wang SQ, Long M, Wohland T, Chua BT, Sun Y, Li P, Chen XW, Xu L, Chen FJ, Li P. A gel-like condensation of Cidec generates lipid-permeable plates for lipid droplet fusion. Dev Cell 2021; 56:2592-2606.e7. [PMID: 34508658 DOI: 10.1016/j.devcel.2021.08.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 05/02/2021] [Accepted: 08/17/2021] [Indexed: 10/20/2022]
Abstract
Membrane contact between intracellular organelles is important in mediating organelle communication. However, the assembly of molecular machinery at membrane contact site and its internal organization correlating with its functional activity remain unclear. Here, we demonstrate that a gel-like condensation of Cidec, a crucial protein for obesity development by facilitating lipid droplet (LD) fusion, occurs at the LD-LD contact site (LDCS) through phase separation. The homomeric interaction between the multivalent N terminus of Cidec is sufficient to promote its phase separation both in vivo and in vitro. Interestingly, Cidec condensation at LDCSs generates highly plastic and lipid-permeable fusion plates that are geometrically constrained by donor LDs. In addition, Cidec condensates are distributed unevenly in the fusion plate generating stochastic sub-compartments that may represent unique lipid passageways during LD fusion. We have thus uncovered the organization and functional significance of geometry-constrained Cidec phase separation in mediating LD fusion and lipid homeostasis.
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Affiliation(s)
- Xuchao Lyu
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jia Wang
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jianqin Wang
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ye-Sheng Yin
- Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Department of Endocrinology and Metabolism, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Yun Zhu
- Biodynamic Optical Imaging Center (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China
| | - Lin-Lin Li
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Shuangru Huang
- Departments of Biological Sciences and Chemistry and NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117557, Singapore
| | - Shuang Peng
- Institute of Mechanics, Chinese Academy of Sciences, No.15 Beisihuanxi Road, Beijing 100190, China
| | - Boxin Xue
- Biodynamic Optical Imaging Center (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China
| | - Rongyu Liao
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Shi-Qiang Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Mian Long
- Institute of Mechanics, Chinese Academy of Sciences, No.15 Beisihuanxi Road, Beijing 100190, China
| | - Thorsten Wohland
- Departments of Biological Sciences and Chemistry and NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117557, Singapore
| | - Boon Tin Chua
- Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Department of Endocrinology and Metabolism, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Yujie Sun
- Biodynamic Optical Imaging Center (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China
| | - Pilong Li
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiao-Wei Chen
- State Key Laboratory of Membrane Biology, Center for Life Sciences and Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing 100101, China
| | - Li Xu
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Shanghai Qi Zhi Institute, Shanghai 200030, China
| | - Feng-Jung Chen
- Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Department of Endocrinology and Metabolism, Zhongshan Hospital, Fudan University, Shanghai 200032, China; Shanghai Qi Zhi Institute, Shanghai 200030, China.
| | - Peng Li
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Shanghai Qi Zhi Institute, Shanghai 200030, China.
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12
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Chen W, Luo N, Zhang Y, Tang LJ, Wang F, Jiang JH. An activatable near-infrared fluorescent probe facilitated high-contrast lipophagic imaging in live cells. Chem Commun (Camb) 2021; 57:8664-8667. [PMID: 34373888 DOI: 10.1039/d1cc03259c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new fluorescent probe (Q-lipo) was developed by conjugating a xanthene scaffold with a quinoline moiety for activatable imaging of lipophagy. Q-lipo with acidic pH activated near infrared fluorescence and the lipid droplet targeting ability allowed activatable fluorescence imaging and flow cytometry detection of lipophagy in live cells with high contrast. It was further utilized to study the effect of tumor-microenvironment related conditions on lipophagy. Q-lipo would provide a useful tool for studying lipophagy in live cells.
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Affiliation(s)
- Wen Chen
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.
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13
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Cottier S, Schneiter R. Lipid droplets form a network interconnected by the endoplasmic reticulum through which their proteins equilibrate. J Cell Sci 2021; 135:271208. [PMID: 34373922 DOI: 10.1242/jcs.258819] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 07/03/2021] [Indexed: 01/13/2023] Open
Abstract
Lipid droplets (LDs) are globular intracellular structures dedicated to the storage of neutral lipids. They are closely associated with the endoplasmic reticulum (ER) and are delineated by a monolayer of phospholipids that is continuous with the cytoplasmic leaflet of the ER membrane. LDs contain a specific set of proteins, but how these proteins are targeted to the LD surface is not fully understood. Here, we devised a yeast mating-based microscopic readout to monitor the transfer of LD proteins upon zygote formation. The results of this analysis indicate that ER fusion between mating partners is required for transfer of LD proteins and that this transfer is continuous, bidirectional and affects most LDs simultaneously. These observations suggest that LDs do not fuse upon mating of yeast cells, but that they form a network that is interconnected through the ER membrane. Consistent with this, ER-localized LD proteins rapidly move onto LDs of a mating partner and this protein transfer is affected by seipin, a protein important for proper LD biogenesis and the functional connection of LDs with the ER membrane.
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Affiliation(s)
- Stéphanie Cottier
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
| | - Roger Schneiter
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
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14
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Zhang C, Aldana-Mendoza JA. Coherent Raman scattering microscopy for chemical imaging of biological systems. JPHYS PHOTONICS 2021. [DOI: 10.1088/2515-7647/abfd09] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Abstract
Coherent Raman scattering (CRS) processes, including both the coherent anti-Stokes Raman scattering and stimulated Raman scattering, have been utilized in state-of-the-art microscopy platforms for chemical imaging of biological samples. The key advantage of CRS microscopy over fluorescence microscopy is label-free, which is an attractive characteristic for modern biological and medical sciences. Besides, CRS has other advantages such as higher selectivity to metabolites, no photobleaching, and narrow peak width. These features have brought fast-growing attention to CRS microscopy in biological research. In this review article, we will first briefly introduce the history of CRS microscopy, and then explain the theoretical background of the CRS processes in detail using the classical approach. Next, we will cover major instrumentation techniques of CRS microscopy. Finally, we will enumerate examples of recent applications of CRS imaging in biological and medical sciences.
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15
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Morén B, Fryklund C, Stenkula K. Surface-associated lipid droplets: an intermediate site for lipid transport in human adipocytes? Adipocyte 2020; 9:636-648. [PMID: 33108251 PMCID: PMC7595579 DOI: 10.1080/21623945.2020.1838684] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Adipose tissue plays a major role in regulating whole-body energy metabolism. While the biochemical processes regulating storage and release of excess energy are well known, the temporal organization of these events is much less defined. In this study, we have characterized the presence of small surface-associated lipid droplets, distinct from the central droplet, in primary human adipocytes. Based on microscopy analyses, we illustrate the distribution of mitochondria, endoplasmic reticulum and lysosomes in the vicinity of these specialized lipid droplets. Ultrastructure analysis confirmed the presence of small droplets in intact adipose tissue. Further, CIDEC, known to bind and regulate lipid droplet expansion, clearly localized at these lipid droplets. Neither acute or prolonged stimulation with insulin or isoprenaline, or pharmacologic intervention to suppress lipid flux, affected the presence of these lipid droplets. Still, phosphorylated perilipin and hormone-sensitive lipase accumulated at these droplets following adrenergic stimuli, which supports metabolic activity at these locations. Altogether, we propose these lipid droplet clusters represent an intermediate site involved in lipid transport in primary adipocytes.
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Affiliation(s)
- Björn Morén
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Claes Fryklund
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Karin Stenkula
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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16
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Salo VT, Hölttä-Vuori M, Ikonen E. Seipin-Mediated Contacts as Gatekeepers of Lipid Flux at the Endoplasmic Reticulum–Lipid Droplet Nexus. ACTA ACUST UNITED AC 2020. [DOI: 10.1177/2515256420945820] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Lipid droplets (LDs) are dynamic cellular hubs of lipid metabolism. While LDs contact a plethora of organelles, they have the most intimate relationship with the endoplasmic reticulum (ER). Indeed, LDs are initially assembled at specialized ER subdomains, and recent work has unraveled an increasing array of proteins regulating ER-LD contacts. Among these, seipin, a highly conserved lipodystrophy protein critical for LD growth and adipogenesis, deserves special attention. Here, we review recent insights into the role of seipin in LD biogenesis and as a regulator of ER-LD contacts. These studies have also highlighted the evolving concept of ER and LDs as a functional continuum for lipid partitioning and pinpointed a role for seipin at the ER-LD nexus in controlling lipid flux between these compartments.
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Affiliation(s)
- Veijo T. Salo
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Maarit Hölttä-Vuori
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Elina Ikonen
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
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17
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Steinmark IE, Chung PH, Ziolek RM, Cornell B, Smith P, Levitt JA, Tregidgo C, Molteni C, Yahioglu G, Lorenz CD, Suhling K. Time-Resolved Fluorescence Anisotropy of a Molecular Rotor Resolves Microscopic Viscosity Parameters in Complex Environments. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1907139. [PMID: 32363742 DOI: 10.1002/smll.201907139] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 02/14/2020] [Accepted: 03/06/2020] [Indexed: 06/11/2023]
Abstract
Understanding viscosity in complex environments remains a largely unanswered question despite its importance in determining reaction rates in vivo. Here, time-resolved fluorescence anisotropy imaging (TR-FAIM) is combined with fluorescent molecular rotors (FMRs) to simultaneously determine two non-equivalent viscosity-related parameters in complex heterogeneous environments. The parameters, FMR rotational correlation time and lifetime, are extracted from fluorescence anisotropy decays, which in heterogeneous environments show dip-and-rise behavior due to multiple dye populations. Decays of this kind are found both in artificially constructed adiposomes and in live cell lipid droplet organelles. Molecular dynamics simulations are used to assign each population to nano-environments within the lipid systems. The less viscous population corresponds to the state showing an average 25° tilt to the lipid membrane normal, and the more viscous population to the state showing an average 55° tilt. This combined experimental and simulation approach enables a comprehensive description of the FMR probe behavior within viscous nano-environments in complex, biological systems.
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Affiliation(s)
| | | | | | | | - Paul Smith
- Department of Physics, King's College London, UK
| | - James A Levitt
- Randall Centre for Cell & Molecular Biophysics, King's College London, UK
| | - Carolyn Tregidgo
- Department of Physics, King's College London, UK
- Genomics England, London, EC1M 6BQ, UK
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18
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Sandoz PA, Tremblay C, van der Goot FG, Frechin M. Image-based analysis of living mammalian cells using label-free 3D refractive index maps reveals new organelle dynamics and dry mass flux. PLoS Biol 2019; 17:e3000553. [PMID: 31856161 PMCID: PMC6922317 DOI: 10.1371/journal.pbio.3000553] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 11/15/2019] [Indexed: 12/22/2022] Open
Abstract
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. By combining HTM with epifluorescence, we demonstrate that mammalian cellular organelles such as lipid droplets (LDs) and mitochondria show specific RI 3D patterns. 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. 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. 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. 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.
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Affiliation(s)
- Patrick A. Sandoz
- Global Health Institute, Life Sciences Faculty, EPFL, Lausanne, Switzerland
| | - Christopher Tremblay
- Global Health Institute, Life Sciences Faculty, EPFL, Lausanne, Switzerland
- Nanolive SA, EPFL Innovation Park, Ecublens, Switzerland
| | - F. Gisou van der Goot
- Global Health Institute, Life Sciences Faculty, EPFL, Lausanne, Switzerland
- * E-mail: (GvdG); (MF)
| | - Mathieu Frechin
- Nanolive SA, EPFL Innovation Park, Ecublens, Switzerland
- * E-mail: (GvdG); (MF)
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19
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Abstract
The combination of next generation sequencing (NGS) and automated liquid handling platforms has led to a revolution in single-cell genomic studies. However, many molecules that are critical to understanding the functional roles of cells in a complex tissue or organs, are not directly encoded in the genome, and therefore cannot be profiled with NGS. Lipids, for example, play a critical role in many metabolic processes but cannot be detected by sequencing. Recent developments in quantitative imaging, particularly coherent Raman scattering (CRS) techniques, have produced a suite of tools for studying lipid content in single cells. This article reviews CRS imaging and computational image processing techniques for non-destructive profiling of dynamic changes in lipid composition and spatial distribution at the single-cell level. As quantitative CRS imaging progresses synergistically with microfluidic and microscopic platforms for single-cell genomic analysis, we anticipate that these techniques will bring researchers closer towards combined lipidomic and genomic analysis.
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Affiliation(s)
- Anushka Gupta
- UC Berkeley-UC San Francisco Graduate Program in Bioengineering, University of California, Berkeley Graduate Division, Berkeley, California, USA.
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20
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Liu AP, Chaudhuri O, Parekh SH. New advances in probing cell-extracellular matrix interactions. Integr Biol (Camb) 2017; 9:383-405. [PMID: 28352896 PMCID: PMC5708530 DOI: 10.1039/c6ib00251j] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 03/20/2017] [Indexed: 12/17/2022]
Abstract
The extracellular matrix (ECM) provides structural and biochemical support to cells within tissues. An emerging body of evidence has established that the ECM plays a key role in cell mechanotransduction - the study of coupling between mechanical inputs and cellular phenotype - through either mediating transmission of forces to the cells, or presenting mechanical cues that guide cellular behaviors. Recent progress in cell mechanotransduction research has been facilitated by advances of experimental tools, particularly microtechnologies, engineered biomaterials, and imaging and analytical methods. Microtechnologies have enabled the design and fabrication of controlled physical microenvironments for the study and measurement of cell-ECM interactions. Advances in engineered biomaterials have allowed researchers to develop synthetic ECMs that mimic tissue microenvironments and investigate the impact of altered physicochemical properties on various cellular processes. Finally, advanced imaging and spectroscopy techniques have facilitated the visualization of the complex interaction between cells and ECM in vitro and in living tissues. This review will highlight the application of recent innovations in these areas to probing cell-ECM interactions. We believe cross-disciplinary approaches, combining aspects of the different technologies reviewed here, will inspire innovative ideas to further elucidate the secrets of ECM-mediated cell control.
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Affiliation(s)
- Allen P. Liu
- Department of Mechanical Engineering , University of Michigan , Ann Arbor , MI 48109 , USA .
- Department of Biomedical Engineering , University of Michigan , Ann Arbor , MI 48109 , USA
- Cellular and Molecular Biology Program , University of Michigan , Ann Arbor , MI 48109 , USA
- Biophysics Program , University of Michigan , Ann Arbor , MI 48109 , USA
| | - Ovijit Chaudhuri
- Department of Mechanical Engineering , Stanford University , Stanford , CA 94305 , USA .
| | - Sapun H. Parekh
- Department of Molecular Spectroscopy , Max Planck Institute for Polymer Research , Mainz 55128 , Germany .
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21
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Saarinen J, Sözeri E, Fraser-Miller SJ, Peltonen L, Santos HA, Isomäki A, Strachan CJ. Insights into Caco-2 cell culture structure using coherent anti-Stokes Raman scattering (CARS) microscopy. Int J Pharm 2017; 523:270-280. [DOI: 10.1016/j.ijpharm.2017.03.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/07/2017] [Accepted: 03/08/2017] [Indexed: 11/16/2022]
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22
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A reliable Raman-spectroscopy-based approach for diagnosis, classification and follow-up of B-cell acute lymphoblastic leukemia. Sci Rep 2016; 6:24821. [PMID: 27089853 PMCID: PMC4835730 DOI: 10.1038/srep24821] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 03/09/2016] [Indexed: 01/20/2023] Open
Abstract
Acute lymphoblastic leukemia type B (B-ALL) is a neoplastic disorder that shows high mortality rates due to immature lymphocyte B-cell proliferation. B-ALL diagnosis requires identification and classification of the leukemia cells. Here, we demonstrate the use of Raman spectroscopy to discriminate normal lymphocytic B-cells from three different B-leukemia transformed cell lines (i.e., RS4;11, REH, MN60 cells) based on their biochemical features. In combination with immunofluorescence and Western blotting, we show that these Raman markers reflect the relative changes in the potential biological markers from cell surface antigens, cytoplasmic proteins, and DNA content and correlate with the lymphoblastic B-cell maturation/differentiation stages. Our study demonstrates the potential of this technique for classification of B-leukemia cells into the different differentiation/maturation stages, as well as for the identification of key biochemical changes under chemotherapeutic treatments. Finally, preliminary results from clinical samples indicate high consistency of, and potential applications for, this Raman spectroscopy approach.
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23
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Di Napoli C, Pope I, Masia F, Langbein W, Watson P, Borri P. Quantitative Spatiotemporal Chemical Profiling of Individual Lipid Droplets by Hyperspectral CARS Microscopy in Living Human Adipose-Derived Stem Cells. Anal Chem 2016; 88:3677-85. [DOI: 10.1021/acs.analchem.5b04468] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Claudia Di Napoli
- School
of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom
| | - Iestyn Pope
- School
of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom
| | - Francesco Masia
- School
of Physics and Astronomy, Cardiff University, Cardiff CF10 3AX, United Kingdom
| | - Wolfgang Langbein
- School
of Physics and Astronomy, Cardiff University, Cardiff CF10 3AX, United Kingdom
| | - Pete Watson
- School
of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom
| | - Paola Borri
- School
of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom
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24
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Daemen S, van Zandvoort MAMJ, Parekh SH, Hesselink MKC. Microscopy tools for the investigation of intracellular lipid storage and dynamics. Mol Metab 2015; 5:153-163. [PMID: 26977387 PMCID: PMC4770264 DOI: 10.1016/j.molmet.2015.12.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 12/19/2015] [Accepted: 12/27/2015] [Indexed: 12/01/2022] Open
Abstract
Background Excess storage of lipids in ectopic tissues, such as skeletal muscle, liver, and heart, seems to associate closely with metabolic abnormalities and cardiac disease. Intracellular lipid storage occurs in lipid droplets, which have gained attention as active organelles in cellular metabolism. Recent developments in high-resolution microscopy and microscopic spectroscopy have opened up new avenues to examine the physiology and biochemistry of intracellular lipids. Scope of review The aim of this review is to give an overview of recent technical advances in microscopy, and its application for the visualization, identification, and quantification of intracellular lipids, with special focus to lipid droplets. In addition, we attempt to summarize the probes currently available for the visualization of lipids. Major conclusions The continuous development of lipid probes in combination with the rapid development of microscopic techniques can provide new insights in the role and dynamics of intracellular lipids. Moreover, in situ identification of intracellular lipids is now possible and promises to add a new dimensionality to analysis of lipid biochemistry, and its relation to (patho)physiology.
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Key Words
- BODIPY, Boron-dipyrromethene
- CARS, coherent anti-stokes Raman scattering
- CLEM, correlative light electron microscopy
- CLSM, confocal laser scanning microscopy
- DIC, differential interference microscopy
- FA, fatty acid
- FIB-SEM, focused ion beam scanning electron microscopy
- FLIP, fluorescence loss in photobleaching
- FRAP, fluorescent recovery after photobleaching
- FRET, fluorescence resonance energy transfer
- Fluorescent lipid probes
- GFP, green fluorescent protein
- HCV, hepatitis C virus
- LD, lipid droplet
- Lipid droplets
- Live-cell imaging
- Metabolic disease
- NBD, nitro-benzoxadiazolyl
- PALM, photoactivation localization microscopy
- SBEM, serial block face scanning electron microscopy
- SIMS, Secondary Ion Mass Spectrometry
- SRS, Stimulated Raman Scattering
- STED, stimulated emission depletion
- STORM, stochastic optical reconstruction microscopy
- Super-resolution
- TAG, triacylglycerol
- TEM, transmission electron microscopy
- TOF-SIMS, time-of-flight SIMS
- TPLSM, two-photon laser scanning microscopy
- Vibrational microscopy
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Affiliation(s)
- Sabine Daemen
- Department of Human Movement Sciences and Human Biology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands.
| | - Marc A M J van Zandvoort
- Department of Genetics and Molecular Cell Biology, CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands; Institute for Molecular Cardiovascular Research (IMCAR), RWTH Aachen University, Aachen, Germany.
| | - Sapun H Parekh
- Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Mainz, Germany.
| | - Matthijs K C Hesselink
- Department of Human Movement Sciences and Human Biology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands.
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25
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Billecke N, Bosma M, Rock W, Fleissner F, Best G, Schrauwen P, Kersten S, Bonn M, Hesselink MKC, Parekh SH. Perilipin 5 mediated lipid droplet remodelling revealed by coherent Raman imaging. Integr Biol (Camb) 2015; 7:467-76. [PMID: 25804837 DOI: 10.1039/c4ib00271g] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Accumulation of fat in muscle tissue as intramyocellular lipids (IMCLs) is closely related to the development of insulin resistance and subsequent type 2 diabetes. Most IMCLs organize into lipid droplets (LDs), the fates of which are regulated by lipid droplet coat proteins. Perilipin 5 (PLIN5) is an LD coating protein, which is strongly linked to lipid storage in muscle tissue. Here we employ a tandem in vitro/ex vivo approach and use chemical imaging by label-free, hyperspectral coherent Raman microscopy to quantify compositional changes in individual LDs upon PLIN5 overexpression. Our results directly show that PLIN5 overexpression in muscle alters individual LD composition and physiology, resulting in larger LDs with higher esterified acyl chain concentration, increased methylene content, and more saturated lipid species. These results suggest that lipotoxic protection afforded by natural PLIN5 upregulation in muscle involves molecular changes in lipid composition within LDs.
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Affiliation(s)
- Nils Billecke
- Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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26
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Wolinski H, Kohlwein SD. Microscopic and spectroscopic techniques to investigate lipid droplet formation and turnover in yeast. Methods Mol Biol 2015; 1270:289-305. [PMID: 25702125 DOI: 10.1007/978-1-4939-2309-0_21] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In spite of some progress in understanding the molecular basis of lipid-associated disorders, major questions about the regulation of synthesis and degradation of lipids and the interaction of these processes with other aspects of cellular physiology are still unresolved. Studies in reference organisms such as various yeast species, the fruit fly Drosophila melanogaster, or the nematode Caenorhabditis elegans complement efforts in mouse models as well as clinical studies in humans to address these questions. Imaging techniques play a pivotal role in understanding lipid droplet biology, and the implementation of imaging-based high-content screens of mutant collections has led to the identification of novel molecular players. This study focuses on novel fluorescent probes as well as spectroscopic imaging techniques to investigate lipid droplet formation and turnover in yeast. The application and limitations of such techniques in understanding lipid storage and turnover are discussed.
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Affiliation(s)
- Heimo Wolinski
- Institute of Molecular Biosciences, BioTechMed-Graz, University of Graz, Humboldtstrasse 50/II, 8010, Graz, Austria
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27
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Varinli H, Osmond-McLeod MJ, Molloy PL, Vallotton P. LipiD-QuanT: a novel method to quantify lipid accumulation in live cells. J Lipid Res 2015; 56:2206-16. [PMID: 26330056 DOI: 10.1194/jlr.d059758] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Indexed: 12/17/2022] Open
Abstract
Lipid droplets (LDs) are the main storage organelles for triglycerides. Elucidation of lipid accumulation mechanisms and metabolism are essential to understand obesity and associated diseases. Adipogenesis has been well studied in murine 3T3-L1 and human Simpson-Golabi-Behmel syndrome (SGBS) preadipocyte cell lines. However, most techniques for measuring LD accumulation are either not quantitative or can be destructive to samples. Here, we describe a novel, label-free LD quantification technique (LipiD-QuanT) to monitor lipid dynamics based on automated image analysis of phase contrast microscopy images acquired during in vitro human adipogenesis. We have applied LipiD-QuanT to measure LD accumulation during differentiation of SGBS cells. We demonstrate that LipiD-QuanT is a robust, nondestructive, time- and cost-effective method compared with other triglyceride accumulation assays based on enzymatic digest or lipophilic staining. Further, we applied LipiD-QuanT to measure the effect of four potential pro- or antiobesogenic substances: DHA, rosiglitazone, elevated levels of D-glucose, and zinc oxide nanoparticles. Our results revealed that 2 µmol/l rosiglitazone treatment during adipogenesis reduced lipid production and caused a negative shift in LD diameter size distribution, but the other treatments showed no effect under the conditions used here.
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Affiliation(s)
- Hilal Varinli
- CSIRO Food and Nutrition Flagship, North Ryde, New South Wales, Australia Department of Biological Sciences, Macquarie University, North Ryde, New South Wales, Australia Genomics and Epigenetics Division, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia
| | - Megan J Osmond-McLeod
- CSIRO Food and Nutrition Flagship, North Ryde, New South Wales, Australia CSIRO Advanced Materials TCP (Nanosafety), North Ryde, New South Wales, Australia
| | - Peter L Molloy
- CSIRO Food and Nutrition Flagship, North Ryde, New South Wales, Australia
| | - Pascal Vallotton
- CSIRO Digital Productivity Flagship, North Ryde, New South Wales, Australia
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28
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Haluszka D, Lőrincz K, Molnár G, Tamás G, Kolonics A, Szipőcs R, Kárpáti S, Wikonkál NM. In vivo second-harmonic generation and ex vivo coherent anti-stokes raman scattering microscopy to study the effect of obesity to fibroblast cell function using an Yb-fiber laser-based CARS extension unit. Microsc Res Tech 2015. [PMID: 26208320 DOI: 10.1002/jemt.22545] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Nonlinear microscopy techniques are being increasingly used to perform in vivo studies in dermatology. These methods enable us to investigate the morphology and monitor the physiological process in the skin by the use of femtosecond lasers operating in the red, near-infrared spectral range (680-1,300 nm). In this work we used two different techniques that require no labeling: second harmonic generation (SHG) for collagen detection and coherent anti-Stokes Raman scattering (CARS) to assess lipid distribution in genetically obese murine skin. Obesity is one of the most serious public health problems due to its high and increasing prevalence and the associated risk of type 2 diabetes and cardiovascular diseases. Other than these diseases, nearly half of patients with diabetes mellitus suffer from dermatological complications such as delayed wound healing, foot ulcers and several other skin changes. In our experiment we investigated and followed the effects of obesity on dermal collagen alterations and adipocyte enlargement using a technique not reported in the literature so far. Our results indicate that the in vivo SHG and ex vivo CARS imaging technique might be an important tool for diagnosis of diabetes-related skin disorders in the near future.
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Affiliation(s)
- Dóra Haluszka
- Department of Dermatology, Venereology and Dermatooncology, Semmelweis University Hungary, Budapest, Hungary.,Department of Applied and Nonlinear Optics, Institute for Solid State Physics and Optics, Budapest, Hungary
| | - Kende Lőrincz
- Department of Dermatology, Venereology and Dermatooncology, Semmelweis University Hungary, Budapest, Hungary
| | - Gábor Molnár
- MTA-SZTE Research Group for Cortical Microcircuits, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Hungary
| | - Gábor Tamás
- MTA-SZTE Research Group for Cortical Microcircuits, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Hungary
| | - Attila Kolonics
- Department of Applied and Nonlinear Optics, Institute for Solid State Physics and Optics, Budapest, Hungary.,R&D Ultrafast Lasers Ltd, Budapest, Hungary
| | - Róbert Szipőcs
- Department of Applied and Nonlinear Optics, Institute for Solid State Physics and Optics, Budapest, Hungary.,R&D Ultrafast Lasers Ltd, Budapest, Hungary
| | - Sarolta Kárpáti
- Department of Dermatology, Venereology and Dermatooncology, Semmelweis University Hungary, Budapest, Hungary
| | - Norbert M Wikonkál
- Department of Dermatology, Venereology and Dermatooncology, Semmelweis University Hungary, Budapest, Hungary
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29
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Winterhalder MJ, Zumbusch A. Beyond the borders--Biomedical applications of non-linear Raman microscopy. Adv Drug Deliv Rev 2015; 89:135-44. [PMID: 25959426 DOI: 10.1016/j.addr.2015.04.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 04/17/2015] [Accepted: 04/29/2015] [Indexed: 11/26/2022]
Abstract
Raman spectroscopy offers great promise for label free imaging in biomedical applications. Its use, however, is hampered by the long integration times required and the presence of autofluorescence in many samples which outshines the Raman signals. In order to overcome these limitations, a variety of different non-linear Raman imaging techniques have been developed over the last decade. This review describes biomedical applications of these novel but already mature imaging techniques.
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30
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Barbosa AD, Savage DB, Siniossoglou S. Lipid droplet-organelle interactions: emerging roles in lipid metabolism. Curr Opin Cell Biol 2015; 35:91-7. [PMID: 25988547 DOI: 10.1016/j.ceb.2015.04.017] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 04/27/2015] [Accepted: 04/28/2015] [Indexed: 01/02/2023]
Abstract
Cellular homeostasis depends on the precisely coordinated use of lipids as fuels for energy production, building blocks for membrane biogenesis or chemical signals for intra-cellular and inter-cellular communication. Lipid droplets (LDs) are universally conserved dynamic organelles that can store and mobilize fatty acids and other lipid species for their multiple cellular roles. Increasing evidence suggests that contact zones between LDs and other organelles play important roles in the trafficking of lipids and in the regulation of lipid metabolism. Here we review recent advances regarding the nature and functional relevance of interactions between LDs and other organelles-particularly the endoplasmic reticulum (ER), LDs, mitochondria and vacuoles-that highlight their importance for lipid metabolism.
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Affiliation(s)
- Antonio Daniel Barbosa
- Cambridge Institute for Medical Research, University of Cambridge, CB2 0XY Cambridge, United Kingdom
| | - David B Savage
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, Cambridge CB2 0QQ, United Kingdom
| | - Symeon Siniossoglou
- Cambridge Institute for Medical Research, University of Cambridge, CB2 0XY Cambridge, United Kingdom.
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31
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32
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Schie IW, Krafft C, Popp J. Applications of coherent Raman scattering microscopies to clinical and biological studies. Analyst 2015; 140:3897-909. [PMID: 25811305 DOI: 10.1039/c5an00178a] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Coherent anti-Stokes Raman scattering (CARS) microscopy and stimulated Raman scattering (SRS) microscopy are two nonlinear optical imaging modalities that are at the frontier of label-free and chemical specific biological and clinical diagnostics. The applications of coherent Raman scattering (CRS) microscopies are multifold, ranging from investigation of basic aspects of cell biology to the label-free detection of pathologies. This review summarizes recent progress of biological and clinical applications of CRS between 2008 and 2014, covering applications such as lipid droplet research, single cell analysis, tissue imaging and multiphoton histopathology of atherosclerosis, myelin sheaths, skin, hair, pharmaceutics, and cancer and surgical margin detection.
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Affiliation(s)
- Iwan W Schie
- Leibniz Institute of Photonic Technology, Albert-Einstein-Straße 9, 07745 Jena, Germany.
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33
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Imaging without Fluorescence: Nonlinear Optical Microscopy for Quantitative Cellular Imaging. Anal Chem 2014; 86:8506-13. [DOI: 10.1021/ac5013706] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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34
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WINTERHALDER MJ, ZUMBUSCH A. Nonlinear optical microscopy with vibrational contrast. J Microsc 2014; 255:1-6. [DOI: 10.1111/jmi.12131] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 03/24/2014] [Indexed: 02/01/2023]
Affiliation(s)
- M. J. WINTERHALDER
- Department of Chemistry; University of Konstanz; D-78457 Konstanz Germany
| | - A. ZUMBUSCH
- Department of Chemistry; University of Konstanz; D-78457 Konstanz Germany
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35
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Kiss RS, Nilsson T. Rab proteins implicated in lipid storage and mobilization. J Biomed Res 2014; 28:169-77. [PMID: 25013400 PMCID: PMC4085554 DOI: 10.7555/jbr.28.20140029] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 02/28/2014] [Indexed: 12/28/2022] Open
Abstract
Abnormal intracellular accumulation or transport of lipids contributes greatly to the pathogenesis of human diseases. In the liver, excess accumulation of triacylglycerol (TG) leads to fatty liver disease encompassing steatosis, steatohepatitis and fibrosis. This places individuals at risk of developing cirrhosis, hepatocellular carcinoma or hepatic decompensation and also contributes to the emergence of insulin resistance and dyslipidemias affecting many other organs. Excessive accumulation of TG in adipose tissue contributes to insulin resistance as well as to the release of cytokines attracting leucocytes leading to a pro-inflammatory state. Pathological accumulation of cholesteryl ester (CE) in macrophages in the arterial wall is the progenitor of atherosclerotic plaques and heart disease. Overconsumption of dietary fat, cholesterol and carbohydrates explains why these diseases are on the increase yet offers few clues for how to prevent or treat individuals. Dietary regimes have proven futile and barring surgery, no realistic alternatives are at hand as effective drugs are few and not without side effects. Overweight and obesity-related diseases are no longer restricted to the developed world and as such, constitute a global problem. Development of new drugs and treatment strategies are a priority yet requires as a first step, elucidation of the molecular pathophysiology underlying each associated disease state. The lipid droplet (LD), an up to now overlooked intracellular organelle, appears at the heart of each pathophysiology linking key regulatory and metabolic processes as well as constituting the site of storage of both TGs and CEs. As the molecular machinery and mechanisms of LDs of each cell type are being elucidated, regulatory proteins used to control various cellular processes are emerging. Of these and the subject of this review, small GTPases belonging to the Rab protein family appear as important molecular switches used in the regulation of the intracellular trafficking and storage of lipids.
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Affiliation(s)
- Robert Scott Kiss
- Department of Medicine, McGill University, Montreal, Canada; ; Research Institute of McGill University Health Centre, Montreal, Canada
| | - Tommy Nilsson
- Department of Medicine, McGill University, Montreal, Canada; ; Research Institute of McGill University Health Centre, Montreal, Canada
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36
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Nölle JM, Jüngst C, Zumbusch A, Wöll D. Monitoring of viscosity changes during free radical polymerization using fluorescence lifetime measurements. Polym Chem 2014. [DOI: 10.1039/c3py01684f] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A molecular rotor with a fluorescence lifetime depending on the local viscosity of its surroundings has been successfully used as a probe to monitor local viscosity changes during the bulk radical polymerization of methyl methacrylate.
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Affiliation(s)
- Jan Martin Nölle
- Department of Chemistry
- University of Konstanz
- Universitätsstr. 10
- 78464 Konstanz
- Germany
| | - Christian Jüngst
- Department of Chemistry
- University of Konstanz
- Universitätsstr. 10
- 78464 Konstanz
- Germany
| | - Andreas Zumbusch
- Department of Chemistry
- University of Konstanz
- Universitätsstr. 10
- 78464 Konstanz
- Germany
| | - Dominik Wöll
- Department of Chemistry
- University of Konstanz
- Universitätsstr. 10
- 78464 Konstanz
- Germany
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Abstract
Lipid droplets are intracellular organelles that are found in most cells, where they have fundamental roles in metabolism. They function prominently in storing oil-based reserves of metabolic energy and components of membrane lipids. Lipid droplets are the dispersed phase of an oil-in-water emulsion in the aqueous cytosol of cells, and the importance of basic biophysical principles of emulsions for lipid droplet biology is now being appreciated. Because of their unique architecture, with an interface between the dispersed oil phase and the aqueous cytosol, specific mechanisms underlie their formation, growth and shrinkage. Such mechanisms enable cells to use emulsified oil when the demands for metabolic energy or membrane synthesis change. The regulation of the composition of the phospholipid surfactants at the surface of lipid droplets is crucial for lipid droplet homeostasis and protein targeting to their surfaces.
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