title: Human endothelial progenitor cells internalize high-density lipoprotein.
abstract: Endothelial progenitor cells (EPCs) originate either directly from hematopoietic stem cells or from a subpopulation of monocytes. Controversial views about intracellular lipid traffic prompted us to analyze the uptake of human high density lipoprotein (HDL), and HDL-cholesterol in human monocytic EPCs. Fluorescence and electron microscopy were used to investigate distribution and intracellular trafficking of HDL and its associated cholesterol using fluorescent surrogates (bodipy-cholesterol and bodipy-cholesteryl oleate), cytochemical labels and fluorochromes including horseradish peroxidase and Alexa Fluor® 568. Uptake and intracellular transport of HDL were demonstrated after internalization periods from 0.5 to 4 hours. In case of HDL-Alexa Fluor® 568, bodipy-cholesterol and bodipy-cholesteryl oleate, a photooxidation method was carried out. HDL-specific reaction products were present in invaginations of the plasma membrane at each time of treatment within endocytic vesicles, in multivesicular bodies and at longer periods of uptake, also in lysosomes. Some HDL-positive endosomes were arranged in form of "strings of pearl"- like structures. HDL-positive multivesicular bodies exhibited intensive staining of limiting and vesicular membranes. Multivesicular bodies of HDL-Alexa Fluor® 568-treated EPCs showed multilamellar intra-vacuolar membranes. At all periods of treatment, labeled endocytic vesicles and organelles were apparent close to the cell surface and in perinuclear areas around the Golgi apparatus. No HDL-related particles could be demonstrated close to its cisterns. Electron tomographic reconstructions showed an accumulation of HDL-containing endosomes close to the trans-Golgi-network. HDL-derived bodipy-cholesterol was localized in endosomal vesicles, multivesicular bodies, lysosomes and in many of the stacked Golgi cisternae and the trans-Golgi-network Internalized HDL-derived bodipy-cholesteryl oleate was channeled into the lysosomal intraellular pathway and accumulated prominently in all parts of the Golgi apparatus and in lipid droplets. Subsequently, also the RER and mitochondria were involved. These studies demonstrated the different intracellular pathway of HDL-derived bodipy-cholesterol and HDL-derived bodipy-cholesteryl oleate by EPCs, with concomitant.
authors.affiliation: Center for Anatomy and Cell Biology, Department of Cell Biology and Ultrastructure Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Kaemisa
authors.initials: K
authors.lastname: Srisen
authors.affiliation: Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics, Medical University of Vienna, Vienna, Austria.
authors.forename: Clemens
authors.initials: C
authors.lastname: Röhrl
authors.affiliation: Center for Anatomy and Cell Biology, Department of Cell Biology and Ultrastructure Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Claudia
authors.initials: C
authors.lastname: Meisslitzer-Ruppitsch
authors.affiliation: Center for Anatomy and Cell Biology, Department of Cell Biology and Ultrastructure Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Carmen
authors.initials: C
authors.lastname: Ranftler
authors.affiliation: Center for Anatomy and Cell Biology, Department of Cell Biology and Ultrastructure Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Adolf
authors.initials: A
authors.lastname: Ellinger
authors.affiliation: Center for Anatomy and Cell Biology, Department of Cell Biology and Ultrastructure Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Margit
authors.initials: M
authors.lastname: Pavelka
authors.affiliation: Center for Anatomy and Cell Biology, Department of Cell Biology and Ultrastructure Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Josef
authors.initials: J
authors.lastname: Neumüller
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D055032:Electron Microscope Tomography; D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D006412:Hematopoietic Stem Cells / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008075:Lipoproteins, HDL / Q000032:analysis / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D051122:Scavenger Receptors, Class B / Q000378:metabolism
chemical_list: D008075:Lipoproteins, HDL; C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B