Laser scanning cytometry: a novel method for the detection of platelet--endothelial cell adhesion

Advances in Platelet Subpopulation Research

Although lacking a nucleus, platelets are increasingly recognized not only for their complexity, but also for their diversity. Some 50 years ago platelet subpopulations were characterized by size and density, and these characteristics were thought to reflect platelet aging. Since, our knowledge of platelet heterogeneity has grown to recognize that differences in platelet biochemistry and function exist. This includes the identification of vanguard and follower platelets, platelets with differing procoagulant ability including "COAT-platelets" which enhance procoagulant protein retention on their surface, and most recently, the identification of platelet subpopulations with a differential ability to generate and respond to nitric oxide. Hence, in this mini-review, we summarize the current knowledge of platelet subpopulation diversity focusing on their physical, biochemical, and functional heterogeneity. In addition, we review how platelet subpopulations may change between health and disease and how differences among platelets may influence response to anti-platelet therapy. Finally, we look forward and discuss some of the future directions and challenges for this growing field of platelet research.

Laser scanning cytometry: principles and applications-an update

Laser scanning cytometer (LSC) is the microscope-based cytofluorometer that offers a plethora of unique analytical capabilities, not provided by flow cytometry (FCM). This review describes attributes of LSC and covers its numerous applications derived from plentitude of the parameters that can be measured. Among many LSC applications the following are emphasized: (a) assessment of chromatin condensation to identify mitotic, apoptotic cells, or senescent cells; (b) detection of nuclear or mitochondrial translocation of critical factors such as NF-κB, p53, or Bax; (c) semi-automatic scoring of micronuclei in mutagenicity assays; (d) analysis of fluorescence in situ hybridization (FISH) and use of the FISH analysis attribute to measure other punctuate fluorescence patterns such as γH2AX foci or receptor clustering; (e) enumeration and morphometry of nucleoli and other cell organelles; (f) analysis of progeny of individual cells in clonogenicity assay; (g) cell immunophenotyping; (h) imaging, visual examination, or sequential analysis using different probes of the same cells upon their relocation; (i) in situ enzyme kinetics, drug uptake, and other time-resolved processes; (j) analysis of tissue section architecture using fluorescent and chromogenic probes; (k) application for hypocellular samples (needle aspirate, spinal fluid, etc.); and (l) other clinical applications. Advantages and limitations of LSC are discussed and compared with FCM.

Laser scanning cytometry: principles and applications

The laser scanning cytometer (LSC) is the microscope-based cytofluorometer that offers a plethora of analytical capabilities. Multilaser-excited fluorescence emitted from individual cells is measured at several wavelength ranges, rapidly (up to 5000 cells/min), with high sensitivity and accuracy. The following applications of LSC are reviewed: (1) identification of cells that differ in degree of chromatin condensation (e.g., mitotic or apoptotic cells or lymphocytes vs granulocytes vs monocytes); (2) detection of translocation between cytoplasm vs nucleus or nucleoplasm vs nucleolus of regulatory molecules such as NF-kappaB, p53, or Bax; (3) semiautomatic scoring of micronuclei in mutagenicity assays; (4) analysis of fluorescence in situ hybridization; (5) enumeration and morphometry of nucleoli; (6) analysis of phenotype of progeny of individual cells in clonogenicity assay; (7) cell immunophenotyping; (8) visual examination, imaging, or sequential analysis of the cells measured earlier upon their relocation, using different probes; (9) in situ enzyme kinetics and other time-resolved processes; (10) analysis of tissue section architecture; (11) application for hypocellular samples (needle aspirate, spinal fluid, etc.); (12) other clinical applications. Advantages and limitations of LSC are discussed and compared with flow cytometry.

Laser scanning cytometry and tissue microarray analysis of salinity effects on killifish chloride cells

The effects of salinity on chloride cells (CC) and Na+/K+-ATPase content in gill epithelium of euryhaline killifish Fundulus heteroclitus were analyzed using laser scanning cytometry (LSC) and tissue microarrays (TMAs). Salinity acclimations consisted of acute transfer from freshwater (FW) to 1× seawater (SW) and gradual transfer from FW to 2.4× SW. Suspensions of dissociated gill epithelial cells were stained with DASPMI and evaluated using LSC. CC number and volume are proportional to external salinity, being lower in FW(0.5±0.2×105 and 405±32 μm3,respectively) and higher after 5 weeks in 2.4× SW(3.7±0.9×105 and 2697±146 μm3,respectively). TMAs were constructed from fixed gill tissues and developed using antibody for Na+/K+-ATPase to visualize CCs in situ and compare their characteristics with isolated CCs. Na+/K+-ATPase content per CC increases transiently (from 2.2±0.5×106 to 4.8±1.1×106relative fluorescence units, RFU) after 1 week of acute acclimation to 1× SW but returns to baseline values(2.4±0.5×106 RFU) within 5 weeks. In contrast, gradual acclimation to 2.4× SW permanently increases Na+/K+-ATPase content per CC (from 2.0±0.8×106 to 6.7±2.7×106 RFU after 5 weeks). CC size in situ did not correlate well to salinity because of basolateral membrane infoldings. Taken together, these data suggest that euryhaline fishes are capable of sensing environmental salinity to utilize transient short-term and permanent long-term adaptations for coping with salinity changes. These results also demonstrate the power of LSC and TMA for comparative biology.

Clinical applications of laser scanning cytometry

This study reviews existing and potential clinical applications of laser scanning cytometry (LSC) and outlines possible future developments. LSC provides a technology for solid phase cytometry. Fluorochrome-labeled specimens are immobilized on microscopic slides that are placed on a conventional epifluorescence microscope and analyzed by one or two lasers. Data comparable to flow cytometry are generated. In addition, the position of each event is recorded, a feature that allows relocalization and visualization of each measured event. The major advantage of LSC compared with other cytometric methods is the combination of two features: (a) the minimal clinical sample volume needed and (b) the connection of fluorescence data and morphological information for the measured event. Since the introduction of LSC, numerous methods have been established for the analysis of cells, cellular compartments, and tissues. Although most cytometric methods use only two or three colors, the characterization of specimens with up to five fluorochromes is possible. Most clinical applications have been designed to determine ploidy and immunophenotype; other applications include analyses of tissue biopsies and sections, fluorescence in situ hybridization, and the combination of vital and nonvital information on a single-cell basis. With the currently available assays, LSC has proven its wide spectrum of clinical applicability in slide-based cytometry and can be introduced as a standard technology in multiple clinical settings.