Image cytometry has made possible the collection and analysis of multiparameter cellular information. The wider use of image cytometry in drug screening will depend on its throughput, efficiency, repeatability, and on the added benefits compared with less sophisticated but faster methods. Throughput (number of datapoints per unit of time) and efficiency (number of datapoints from the given amount of reagents or plate area) are addressed here by screening multiple cell lines simultaneously using encoded carriers (CellCards). CellCards are rectangular particles with an expandable color barcode and a transparent section for cellular readout. Before performing the assay, each cell line is grown on a different class of carriers. CellCards, with attached cells, are mixed and dispensed into a microtiter plate where the assay is performed. Next the plates are imaged, decoded and the cells associated with each CellCard class are analyzed. Using CellCards the efficiency is increased by the multiplexing factor (the number of cell lines analyzed in each well). We routinely run assays with a multiplex factor of ten. Throughput is additionally addressed by working at the lowest possible magnification for a given assay. Decoding of CellCards requires one image per well in 96-well microtiter plate format. The system provides the added benefit of internal consistency since the data can be normalized to controls within each well.
The desire to obtain more biologically relevant data is expanding the use of cell-based assays in drug discovery. These assays are performed and analyzed in ever more sophisticated ways (e.g. high content screening) that allow the collection of multiparametric information about cells affected by the screened compounds. The driver for these developments is the desire to increase data quality and density and reduce the use of valuable reagents and time. Here we describe an approach that adds a new dimension to the data quality/quantity mix by simultaneously analyzing several cell types in the same microplate well. The system is based on the use of encoded carriers (CellCards) that permit the reading and analysis of cellular responses, and at the same time allow decoding and the attribution of these responses to the appropriate cell line. CellCards are rectangular particles with an expandable color barcode and a transparent section upon which cells can be grown and imaged for cellular readout. Before performing the assay, each cell line is grown on a different class of CellCards. CellCards, with attached cells, are mixed and dispensed into a microtiter plate where the assay is performed. Next the plates are imaged, decoded and the cells associated with each CellCard class are analyzed. Multiplexing cell lines allows assay controls and data normalization within each well, reducing well-to-well variability. It also allows the simultaneous interrogation of multiple targets and thus concurrent potency and selectivity screening. This may significantly reduce the time required to take a compound from primary screening into the clinic.
Fluorescent In-Situ Hybridization (FISH) is becoming an accepted technique for identification of aneuploidies in interphase fetal cells obtained by either CVS (chorionic villus sampling) or amniocentesis. Currently the analysis is done manually by a skilled operator and is a lengthy and fatiguing process. Applied Imaging is developing an automated procedure for counting FISH spots in these samples. Spot counting involves slide preparation, probe hybridization, filter selection, FISH image acquisition, image analysis, operator verification, and analysis of count distributions. We concentrate on the tasks starting with image acquisition. The following topics are covered: selection of appropriate cells, acquisition and processing of Z-stacks of FISH images for presentation and spot counting, background removal, formation of segmentation tree and selection of spot markers, growing of spot markers by means of constrained watershed, detection of irregular spots and flagging them for the user, time and accuracy compared with manual method, and applicability to a clinical research setting.
The detection and genetic analysis of fetal cells in maternal blood will permit noninvasive prenatal screening for genetic defects. Applied Imaging has developed and is currently evaluating a system for semiautomatic detection of fetal nucleated red blood cells on slides and acquisition of their DNA probe FISH images. The specimens are blood smears from pregnant women (9 - 16 weeks gestation) enriched for nucleated red blood cells (NRBC). The cells are identified by using labeled monoclonal antibodies directed to different types of hemoglobin chains (gamma, epsilon); the nuclei are stained with DAPI. The Applied Imaging system has been implemented with both Olympus BX and Nikon Eclipse series microscopes which were equipped with transmission and fluorescence optics. The system includes the following motorized components: stage, focus, transmission, and fluorescence filter wheels. A video camera with light integration (COHU 4910) permits low light imaging. The software capabilities include scanning, relocation, autofocusing, feature extraction, facilities for operator review, and data analysis. Detection of fetal NRBCs is achieved by employing a combination of brightfield and fluorescence images of nuclear and cytoplasmic markers. The brightfield and fluorescence images are all obtained with a single multi-bandpass dichroic mirror. A Z-stack of DNA probe FISH images is acquired by moving focus and switching excitation filters. This stack is combined to produce an enhanced image for presentation and spot counting.