title: Nanoscale three-dimensional imaging of the human myocyte.
abstract: The ventricular human myocyte is spatially organized for optimal ATP and Ca(2+) delivery to sarcomeric myosin and ionic pumps during every excitation-contraction cycle. Comprehension of three-dimensional geometry of the tightly packed ultrastructure has been derived from discontinuous two-dimensional images, but has never been precisely reconstructed or analyzed in human myocardium. Using a focused ion beam scanning electron microscope, we created nanoscale resolution serial images to quantify the three-dimensional ultrastructure of a human left ventricular myocyte. Transverse tubules (t-tubule), lipid droplets, A-bands, and mitochondria occupy 1.8, 1.9, 10.8, and 27.9% of the myocyte volume, respectively. The complex t-tubule system has a small tortuosity (1.04±0.01), and is composed of long transverse segments with diameters of 317±24nm and short branches. Our data indicates that lipid droplets located well beneath the sarcolemma are proximal to t-tubules, where 59% (13 of 22) of lipid droplet centroids are within 0.50μm of a t-tubule. This spatial association could have an important implication in the development and treatment of heart failure because it connects two independently known pathophysiological alterations, a substrate switch from fatty acids to glucose and t-tubular derangement.
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, MO, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Sulkin
authors.affiliation: Department of Radiation Oncology, School of Medicine, Washington University in St. Louis, MO, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Yang
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, MO, USA.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Holzem
authors.affiliation: FEI Company, Hillsboro, OR, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Van Leer
authors.affiliation: FEI Company, Hillsboro, OR, USA.
authors.forename: Cliff
authors.initials: C
authors.lastname: Bugge
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, MO, USA.
authors.forename: Jacob I
authors.initials: JI
authors.lastname: Laughner
authors.affiliation: Department of Pathology and Immunology, School of Medicine, Washington University in St. Louis, MO, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Green
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, MO, USA. Electronic address: igor@wustl.edu.
authors.forename: Igor R
authors.initials: IR
authors.lastname: Efimov
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism / Q000648:ultrastructure*; D006801:Humans; D021621:Imaging, Three-Dimensional; D066292:Lipid Droplets / Q000378:metabolism / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D032342:Muscle Cells / Q000378:metabolism / Q000648:ultrastructure*; D009206:Myocardium / Q000648:ultrastructure*; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000648:ultrastructure*; D012508:Sarcolemma / Q000648:ultrastructure
chemical_list: D000255:Adenosine Triphosphate; D002118:Calcium
keywords: Focused ion beam tomography; Metabolism; Myocyte; Ultrastructure