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It is already several years ago, when several cytometrists (including myself) announced the end of the innovative age of flow cytometry, stating that flow cytometry is now a fully mature technology. Technological advances that may be expected in the future will be only minute and only relevant for specialized technology aficionados. Innovations will come from other fields of quantitative single cell analysis such as image cytometry, proteomics or genomics. However, after the end of this year's CYTO conference, excellently organized and compiled by John P. Nolan, Larry A. Sklar and their team, I feel the need to correct my earlier notion admitting that my prediction was incorrect. Several innovations are now appearing on the horizon and numerous innovations, for which it was unclear initially if they would survive or would only be relevant in niche areas, have now matured and are starting to attract a global audience.

As a good example, mass cytometry (MCM), which was initially presented about four years ago [1] and the first applications were developed at Garry Nolan's lab in Stanford [2], is becoming a common technology with groups all over the globe using it for their basic, applied or clinical work. This becomes clearly visible by the increasing numbers of papers presented at CYTO 2013 from a very diverse authorship using MCM relative to previous years.

Not surprisingly, as a consequence of the great interest raised by MCM the Best Paper Award for Cytometry Part A, presented at CYTO 2013, was awarded to an excellent manuscript that opens MCM application up for the exploration of the cell cycle [3]. Cell cycle analysis was one of the first clinical applications of flow cytometry way back in the late 1960's [4]. The nomination of the Best Paper Award to manuscripts that were published in Cytometry Part A in the last 18 months prior to a CYTO conference is now a tradition since 2007, when the first paper was awarded. The award is officially presented to the winner(s) at the award ceremony following the business meeting of the ISAC CYTO conference. Best manuscripts are selected based on their innovative potential, quality of writing and presentation as well as on the overall interest of the scientific community measurable by usage and citation rates. The finalists are then evaluated and scored by the reviewing committee consisting of the Associate Editors of the journal. This year it was the unequivocal opinion of the committee that the 2012 publication by Gregory K. Behbehani, Sean C. Bendall, Matthew R. Clutter, Wendy J. Fantl, and Garry P. Nolan [3] was the clear winner of this competition. I wish to express my congratulations and thanks to the authors for publishing their outstanding work in Cytometry Part A.

However, I also wish to emphasize that numerous other excellent scientific works with innovative biomedical applications and findings as well as novel or improved technologies for quantitative single cell analysis have been published in recent and earlier time periods in this journal. The mentioning of all innovative new scientific approaches that were presented at this year's CYTO conference would by far exceed the bearable length of an editorial. In addition, the selection would possibly be biased by my personal preferences. Potential views into the future of what will come next are the work of young investigators that were recognized by Outstanding Poster Awards, the President's Award of excellence and the new ISAC scholars.

These works display the entire plethora that Cytometry represents. They include large scale medical studies and handling of mass data for translational medicine, innovative flow cytometry applications using microfluidics and acoustic focusing for cell sorting and improved analysis (see also 5), just to name a few. We will see these presentations hopefully soon as excellent manuscripts submitted to Cytometry Part A.

The present issue of this Journal is related to applications or translations of cytometry technologies into practical (clinical) use and has a focus on experimental work with live cells. Two works involve investigation of cellular and mitochondrial transmembrane potential (MP) which are highly relevant in the investigation and quantitation of cell activation and death [6]. Anionic and cationic MP dyes are applied to detect variations in MP. Whereas cationic dyes such as cyanine dyes enter the cells at physiological MP values, anionic dyes mostly enter the cells when they are depolarized, for example when cells are dying [7].

Massanella and colleagues from Badalona and Barcelona, Spain (in this issue, page 648) used carbocyanine dyes in a qualitative assay for determining mitochondrial MP to investigate cell death of T lymphocytes from HIV infected patients. Their data provide evidence that different cell types (in their case Th or Tc) may require different types of dyes for reliable cell death assessment.

Klapperstück and colleagues from Halle and Ilmenau, Germany (in this issue, page 612) applied an oxonol dye to quantify transmembrane potential in living human cell lines. As oxonol dyes normally do not enter live cells they have the advantage to be less cytotoxic. Hitherto, the Nernst equation is used to calculate absolute MP values [7] based on flow cytometry generated data. However, the authors observed that the presumption that the extracellular unbound concentration of the dye remains relatively constant and intracellular uptake is negligible, is incorrect and if these factors are not taken into account, calculated MP values are inaccurate. The authors provide in their study an improved experimental and mathematical approach for a precise MP determination in flow cytometry experiments.

In two other manuscripts cell lines are used to investigate how liposome uptake into astrocytes is regulated by lipid components (Suesca et al., in this issue, page 627) or how adherence regulation by aggressive metastasizing tumor cells occurs (Smith et al., in this issue, page 659). Both studies reveal new unknown mechanisms regarding how the (micro) environment is regulating cell properties and function and vice versa and are good examples that Cytometry A embraces the translation of cytometry technology into biomedical research.

Literature Cited

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  2. Literature Cited
  • 1
    Bandura DR, Baranov VI, Ornatsky OI, Antonov A, Kinach R, Lou X, Pavlov S, Vorobiev S, Dick JE, Tanner SD. Mass cytometry: technique for real time single cell multitarget immunoassay based on inductively coupled plasma time-of-flight mass spectrometry. Anal Chem 2009;81(16):68136822.
  • 2
    Bendall SC, Simonds EF, Qiu P, Amir el-AD, Krutzik PO, Finck R, Bruggner RV, Melamed R, Trejo A, Ornatsky OI, Balderas RS, Plevritis SK, Sachs K, Pe'er D, Tanner SD, Nolan GP. Single-cell mass cytometry of differential immune and drug responses across a human hematopoietic continuum. Science 2011;332(6030):687696.
  • 3
    Behbehani GK, Bendall SC, Clutter MR, Fantl WJ, Nolan GP. Single-cell mass cytometry adapted to measurements of the cell cycle. Cytometry A 2012;81A(7):552566.
  • 4
    Dittrich W, Göhde W. [Impulse fluorometry of single cells in suspension]. Z Naturforsch B 1969;24(3):360361.
  • 5
    Grenvall C, Folkenberg JR, Augustsson P, Laurell T. Label-free somatic cell cytometry in raw milk using acoustophoresis. Cytometry A 2012;81A(12):10761083.
  • 6
    Warnes G, Martins S. Real-time flow cytometry for the kinetic analysis of oncosis. Cytometry A 2011;79A(3):181191.
  • 7
    Tárnok A, Rothe G. Determination of Cell Physiological Parameters: pH, Ca2+, Glutathione, Transmembrane Potential. In: Sack U, Tárnok A, Rothe G, editors. Cellular Diagnostics. Basics, Methods and Clinical Applications of Flow Cytometry. Basel: Karger, 2009; pp 325342.