Laser Scanning Cytometry Analysis Research Articles

Detection of localized caspase activity in early apoptotic cells by laser scanning cytometry.

Caspase activation is a critical early step in the onset of apoptosis. Cell-permeable fluorogenic caspase substrates have proven valuable in detecting caspase activation by flow cytometry. Nevertheless, detection of early low-level caspase activation has been difficult using conventional area or peak fluorescence analysis by flow cytometry, despite the apparent presence of these cells as observed by microscopy. We describe a method utilizing maximum fluorescence pixel analysis by laser scanning cytometry (LSC) to detect early apoptotic cells. The PhiPhiLux-G(1)D(2) caspase 3/7 substrate was used in combination with DNA dye exclusion and annexin V binding to identify several stages of apoptosis in EL4 murine thymoma cells by both traditional flow and LSC. LSC analysis of maximum pixel brightness in individual cells demonstrated an intermediate caspase-low subpopulation not detectable by flow or LSC integral analysis. LSC analysis of caspase activity was then carried out using the larger UMR-106 rat osteosarcoma cell line to determine if this apparent early caspase activity could be correlated with localized, punctate caspase activity observed by microscopy. The caspase-low subpopulation found in apoptotic EL4 cells was also observable in UMR-106 cells. Relocation to cells with low fluorescence due to caspase activity and subsequent examination by microscopy demonstrated that these latter cells indeed show punctate, highly localized caspase activation foci that might represent an early stage in caspase activation. Cells with low-level, localized caspase expression can be detected using maximum pixel analysis by LSC. This methodology allows an early step of apoptotic activation to be resolved for further analysis.

Comparative methodologic study of NFκB activation in cultured endothelial cells

The transcriptional regulatory protein nuclear factor κB (NFκB) participates in the control of gene expression of many modulators of the inflammatory and immune responses. Various activators trigger NFκB release and nuclear translocation after phosphorylation and proteolytic degradation of IκB. This study evaluated the abilities of fluorescence and confocal microscopies, laser scanning cytometry (LSC), electrophoretic mobility-shift assay (EMSA), and Western blotting to detect NFκB activation in endothelial cells (ECs) and to investigate the role of homocysteine (Hcy) in NFκB activation. ECs were treated with interleukin-1β (10 ng/mL) or Hcy thiolactone (1 and 5 mmol/L) as NFκB activators. Hcy, a thiol-containing amino acid, has been shown to directly damage ECs in vitro. Experimental evidence suggests that the atherogenic propensity associated with hyperhomocysteinemia results from EC dysfunction. When ECs were pretreated with an inhibitor (pyrrolidine dithiocarbamate, 100 μmol/L) or with staurosporine (5 μL/mL), no NFκB activation was observed. NFκB activation in ECs could be detected with all five techniques, clearly showing NFκB translocation from the cytoplasm to the nuclei. Confocal microscopy was more sensitive and less subjective than immunofluorescence microscopy. LSC was even more sensitive, specific, and reproducible. EMSA, the reference method, has the disadvantages of being radioactive, expensive, and time consuming. Western blot analysis detected the NFκB p50 subunit implicated in NFκB activation. The techniques usually used to detect NFκB activation in ECs are immunofluorescence microscopy and confocal microscopy, LSC, EMSA, and Western blot analysis, but none of them is ready for routine use. (J Lab Clin Med 2000;136:402-11)

The Use of Laser Scanning Cytometry to Assess Depth of Penetration of Adenovirus p53 Gene Therapy in Human Xenograft Biopsies

SCH58500 is an agent for gene therapy of cancer, consisting of a replication-deficient type 5 adenovirus (Ad5) expressing the human p53 tumor suppressor gene (Ad5/p53). An important question about the use of Ad5/p53 gene therapy is how to achieve the therapeutically effective delivery of an Ad5/p53 vector to the tumor. We wanted to determine the effective depth of penetration of an Ad5/p53 vector by dosing the vector in an experimental human xenograft/SCID model. To assess depth of penetration, we developed a novel methodology for scanning tissue sections by laser scanning cytometry (LSC). SCID mice were given intraperitoneal injections of either p53(null) SK-OV-3 human ovarian tumor cells or p53(mut) DU-145 human prostate tumor cells to establish xenograft solid tumors. Mice were then dosed once or twice at 24-hour intervals by intraperitoneal injection with SCH58500 (Ad5/p53), an adenovirus construct expressing beta-galactosidase (Ad5/beta-gal), or a buffer control. Additional groups of mice received a single intraperitoneal dose of 10 mg/kg paclitaxel either alone or coadministered with Ad5/p53. Twenty-four hours after each last dose, the human solid tumor xenograft and relevant mouse tissue were removed from each mouse for the analysis of Ad5/p53 penetration. Immunohistochemistry (IHC) for beta-galactosidase protein revealed a depth of penetration of between 1 and 10 cells from the tumor surface. In some mice, hepatocytes in the periportal regions of liver lobules were also positive, indicating systemic absorption of adenovirus from the peritoneal cavity. IHC staining for p53 and p21 proteins in SK-OV-3 solid tumor xenografts revealed similar Ad/p53 penetration. LSC was used to map and quantitate apoptosis in both tumor and liver tissue biopsies, with over 450,000 nuclei from liver tissue and 150,000 nuclei from tumor tissue being evaluated. LSC analysis demonstrated a high level of apoptosis in the tumors that had been removed from Ad5/p53-dosed mice (12.7-19.7%). This level of apoptosis was significantly higher (P < 0.05) than was observed for liver tissues taken from Ad5/p53-dosed mice (2.7-8.0%) or tumor tissues taken from either Ad5/beta-gal-dosed mice (3.0-6.4%) or buffer control-dosed mice (3.0-5.3%). Scan bit maps from the extensive LSC analyses confirmed that apoptosis was present to about the same depth (1-10 cells) as had been identified by IHC for beta-galactosidase, p53, and p21 proteins. Paclitaxel coadministered with Ad5/p53 had no effect on Ad5 penetration into solid tumors in vivo as measured by IHC for p53 or p21 protein. However, the combination therapy did cause an elevation in the number of tumor cells undergoing apoptosis.

Laser scanning cytometry allows detection of cell death with morphological features of apoptosis in cells stained with PI

Laser scanning cytometry (LSC), a newly developed technology, allowed simple detection of dead cells with morphological features of apoptosis for cells stained with only propidium iodide (PI). HeLa cells were treated with Adriamycin (ADM, 0.5 or 1.0 microgram/ml). A PI fluorescence value (representing DNA content) versus PI fluorescence peak (representing chromatin condensation) cytogram of LSC made it possible to segregate cells with high PI fluorescence peak from others in a cell population and concomitantly to analyze the relationship between the cells and the cell cycle. A fraction of the cells manifesting hypercondensation of chromatin was exclusively present in a cell population treated with ADM. Visual inspection of the cells defined in the cytogram revealed morphological features of apoptosis. LSC analysis facilitates monitoring effects of anticancer drugs on a cell population, because nuclear DNA staining with PI is simple and rapid.

Laser scanning cytometry allows detection of cell death with morphological features of apoptosis in cells stained with PI

Laser scanning cytometry (LSC), a newly developed technology, allowed simple detection of dead cells with morphological features of apoptosis for cells stained with only propidium iodide (PI). HeLa cells were treated with Adriamycin (ADM, 0.5 or 1.0 μg/ml). A PI fluorescence value (representing DNA content) versus PI fluorescence peak (representing chromatin condensation) cytogram of LSC made it possible to segregate cells with high PI fluorescence peak from others in a cell population and concomitantly to analyze the relationship between the cells and the cell cycle. A fraction of the cells manifesting hypercondensation of chromatin was exclusively present in a cell population treated with ADM. Visual inspection of the cells defined in the cytogram revealed morphological features of apoptosis. LSC analysis facilitates monitoring effects of anticancer drugs on a cell population, because nuclear DNA staining with PI is simple and rapid. Cytometry 29:173-177, 1997. © 1997 Wiley-Liss, Inc.

Laser scanning cytometry in pathology of solid tumors. A review.

To review application of laser scanning cytometry (LSC) to analyze several different parameters of human solid tumors in relation to the cell cycle. Tissue sections of cytology specimens were stained for specific parameters and analyzed by LSC. Examples of LSC analysis of the expression of ER, Ki-67, cyclin B1, BrdUrd and ploidy are given. LSC provides rapid, high-precision measurement of the chosen parameters or constituents of each cell in a population of cells and correlates those measurements with the visual image of the corresponding cell.