Research article

High-resolution quantitative imaging of mammalian and bacterial cells using stable isotope mass spectrometry

Claude Lechene¹ , Francois Hillion² , Greg McMahon¹ , Douglas Benson³ , Alan M Kleinfeld⁴ , J Patrick Kampf⁴ , Daniel Distel⁵ , Yvette Luyten⁵ , Joseph Bonventre⁶ , Dirk Hentschel⁶ , Kwon Moo Park⁶ , Susumu Ito⁷ , Martin Schwartz⁸ , Gilles Benichou⁹ and Georges Slodzian¹⁰

¹  National Resource for Imaging Mass Spectrometry, Harvard Medical School and Department of Medicine, Brigham and Women's Hospital, Cambridge, MA 02139, USA

²  Cameca, 29 Quai des Gresillons, 92622 Gennevilliers Cedex, France

³  NSee Inc., 106 Greenhaven Lane, Cary, NC 27511, USA

⁴  Torrey Pines Institute for Molecular Studies, San Diego, CA 92121, USA

⁵  Ocean Genome Legacy Foundation, Ipswich, MA 01938, USA

⁶  Harvard Medical School and Renal Division, Brigham and Women's Hospital, Boston, MA 02115, USA

⁷  Harvard Medical School, Boston, MA 02115, USA

⁸  Department of Microbiology, University of Virginia, Charlottesville, VA 22908, USA

⁹  Harvard Medical School and Department of Surgery, Massachusetts General Hospital, Boston, MA 02114, USA

¹⁰  Universite Paris-Sud, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, 91406 Orsay, France

author email corresponding author email

Journal of Biology 2006, 5:20doi:10.1186/jbiol42

Published:	5 October 2006

Abstract

Background

Secondary-ion mass spectrometry (SIMS) is an important tool for investigating isotopic composition in the chemical and materials sciences, but its use in biology has been limited by technical considerations. Multi-isotope imaging mass spectrometry (MIMS), which combines a new generation of SIMS instrument with sophisticated ion optics, labeling with stable isotopes, and quantitative image-analysis software, was developed to study biological materials.

Results

The new instrument allows the production of mass images of high lateral resolution (down to 33 nm), as well as the counting or imaging of several isotopes simultaneously. As MIMS can distinguish between ions of very similar mass, such as ¹²C¹⁵N^- and ¹³C¹⁴N^-, it enables the precise and reproducible measurement of isotope ratios, and thus of the levels of enrichment in specific isotopic labels, within volumes of less than a cubic micrometer. The sensitivity of MIMS is at least 1,000 times that of ¹⁴C autoradiography. The depth resolution can be smaller than 1 nm because only a few atomic layers are needed to create an atomic mass image. We illustrate the use of MIMS to image unlabeled mammalian cultured cells and tissue sections; to analyze fatty-acid transport in adipocyte lipid droplets using ¹³C-oleic acid; to examine nitrogen fixation in bacteria using ¹⁵N gaseous nitrogen; to measure levels of protein renewal in the cochlea and in post-ischemic kidney cells using ¹⁵N-leucine; to study DNA and RNA co-distribution and uridine incorporation in the nucleolus using ¹⁵N-uridine and ⁸¹Br of bromodeoxyuridine or ¹⁴C-thymidine; to reveal domains in cultured endothelial cells using the native isotopes ¹²C, ¹⁶O, ¹⁴N and ³¹P; and to track a few ¹⁵N-labeled donor spleen cells in the lymph nodes of the host mouse.

Conclusion

MIMS makes it possible for the first time to both image and quantify molecules labeled with stable or radioactive isotopes within subcellular compartments.