title: Imaging lipid bodies in cells and tissues using third-harmonic generation microscopy.
abstract: Lipid bodies have an important role in energy storage and lipid regulation. Here we show that lipid bodies are a major source of contrast in third-harmonic generation (THG) microscopy of cells and tissues. In hepatocytes, micrometer-sized lipid bodies produce a THG signal 1-2 orders of magnitude larger than other structures, which allows one to image them with high specificity. THG microscopy with approximately 1,200 nm excitation can be used to follow the distribution of lipid bodies in a variety of unstained samples including insect embryos, plant seeds and intact mammalian tissue (liver, lung). We found that epi-THG imaging is possible in weakly absorbing tissues because bulk scattering redirects a substantial fraction of the forward-generated harmonic light toward the objective. Finally, we show that the combination of THG microscopy with two-photon and second-harmonic imaging provides a new tool for exploring the interactions between lipid bodies, extracellular matrix and fluorescent compounds (vitamin A, NADH and others) in tissues.
authors.affiliation: Laboratory for optics and biosciences, Ecole Polytechnique, CNRS, INSERM, F-91128 Palaiseau, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Débarre
authors.forename: Willy
authors.initials: W
authors.lastname: Supatto
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Pena
authors.forename: Aurélie
authors.initials: A
authors.lastname: Fabre
authors.forename: Thierry
authors.initials: T
authors.lastname: Tordjmann
authors.forename: Laurent
authors.initials: L
authors.lastname: Combettes
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Schanne-Klein
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Beaurepaire
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000737:chemistry; D022781:Hepatocytes / Q000737:chemistry; D008055:Lipids / Q000032:analysis*; D008099:Liver / Q000166:cytology; D008168:Lung / Q000737:chemistry; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D015388:Organelles / Q000737:chemistry; D010944:Plants / Q000737:chemistry; D012639:Seeds / Q000737:chemistry
chemical_list: D008055:Lipids