Quantitative histology by multicolor slide-based cytometry

Imaging flow cytometry: coping with heterogeneity in biological systems

Imaging flow cytometry (IFC) platforms combine features of flow cytometry and fluorescent microscopy with advances in data-processing algorithms. IFC allows multiparametric fluorescent and morphological analysis of thousands of cellular events and has the unique capability of identifying collected events by their real images. IFC allows the analysis of heterogeneous cell populations, where one of the cellular components has low expression (<0.03%) and can be described by Poisson distribution. With the help of IFC, one can address a critical question of statistical analysis of subcellular distribution of proteins in a cell. Here the authors review advantages of IFC in comparison with more traditional technologies, such as Western blotting and flow cytometry (FC), as well as new high-throughput fluorescent microscopy (HTFM), and discuss further developments of this novel analytical technique.

Noninvasive assessment of localized inflammatory responses

Inflammatory diseases are associated with the accumulation of activated inflammatory cells, particularly polymorphonuclear neutrophils (PMNs), which release reactive oxygen species (ROS) to eradicate foreign bodies and microorganisms. To assess the location and extent of localized inflammatory responses, L-012, a highly sensitive chemiluminescent probe, was employed to noninvasively monitor the production of ROS. We found that L-012-associated chemiluminescence imaging can be used to identify and to quantify the extent of inflammatory responses. Furthermore, regardless of differences among animal models, there is a good linear relationship between chemiluminescence intensity and PMN numbers surrounding inflamed tissue. Depletion of PMNs substantially diminished L-012-associated chemiluminescence in vivo. Finally, L-012-associated chemiluminescence imaging was found to be a powerful tool for assessing implant-mediated inflammatory responses by measuring chemiluminescence intensity at the implantation sites. These results support the use of L-012 for monitoring the kinetics of inflammatory responses in vivo via the detection and quantification of ROS production.

Quantitative in situ analysis of FoxP3+ T regulatory cells on transplant tissue using laser scanning cytometry

There is abundant evidence that immune cells infiltrating into a transplanted organ play a critical role for destructive inflammatory or regulatory immune reactions. Quantitative in situ analysis (i.e., in tissue sections) of immune cells remains challenging due to a lack of objective methodology. Laser scanning cytometry (LSC) is an imaging-based methodology that performs quantitative measurements on fluorescently and/ or chromatically stained tissue or cellular specimens at a single-cell level. In this study, we have developed a novel objective method for analysis of immune cells, including Foxp3(+) T regulatory cells (Tregs), on formalin-fixed /paraffin-embedded (FFPE) transplant biopsy sections using iCys® Research Imaging Cytometer. The development of multiple immunofluorescent staining was established using FFPE human tonsil sample. The CD4/CD8 ratio and the population of Tregs among CD4(+) cells were analyzed using iCys and compared with the results from conventional flow cytometry analysis (FCM). Our multiple immunofluorescent staining techniques allow obtaining clear staining on FFPE sections. The CD4/CD8 ratio analyzed by iCys was concordant with those obtained by FCM. This method was also applicable for liver, small intestine, kidney, pancreas, and heart transplant biopsy sections and provide an objective quantification of Tregs within the grafts.

Quantitative assessment of pancreatic islets using laser scanning cytometry

Insulin-dependent (type II) diabetes is characterized by an inability to metabolize glucose, resulting from insufficient insulin function for glucose transport from the blood to tissues. One cause of insufficiency is malfunction of the insulin-producing beta cells within the pancreatic islets. Various compounds to stimulate and restore normal islet function are under development. Zucker diabetic fatty (ZDF) rat animal models are used to measure efficacy of drug candidates, as they show clinical effects similar to those in diabetic patients. Drug effects are evaluated by removing the pancreas from ZDF rats, processing the tissue with paraffin and sectioning it, and then analyzing the sections utilizing antibodies against targeted proteins to quantify morphology and metabolic activity. This protocol describes quantitative analysis of insulin, glucagon, mitochondria (all on a per-islet basis), and insulin-positive proliferating cells in ZDF and lean rat pancreatic tissue sections using the iCyte Imaging Cytometer.

Cellular analysis by open-source software for affordable cytometry

Image cytometry is an important technique in affordable healthcare and cellular research. Some efforts toward establishing a personal, low-cost cytometer have been described in the literature. However, a self-assembled fluorescence microscope requires software for cytometric analysis. There are some open-source image-based software analysis applications available. However, for a quantitative analysis of images, software that can generate data comparable to those of previously evaluated cytometric analyses programs is required. Hence, the aim of this study is to compare results of a commercially available image cytometry program to data obtained using the open-source software CellProfiler (CP). Leukocytes and fluorescent bead images obtained using a Laser Scanning Cytometer were analyzed by CP and the results compared with those of conventional cytometric analyses' programs. Algorithms were developed enabling the analysis of leukocytes and beads by CP. CP provided similar results to those obtained by the cytometer software. Hallmark parameters, including cell count and fluorescence intensity, revealed a high correlation in the analysis of both programs. Therefore, CP is appropriate for cellular analysis on a self-assembled microscope, thereby enabling affordable cytometry.

Laser scanning cytometry: capturing the immune system in situ

Until recently, it has not been possible to image and functionally correlate the key molecular and cellular events underpinning immunity and tolerance in the intact immune system. Certainly, the field has been revolutionized by the advent of tetramers to identify physiologically relevant specificities of T cells, and the introduction of models in which transgenic T-cell receptor and/or B-cell receptor-bearing lymphocytes are adoptively transferred into normal mice and can then be identified by clonotype-specific antibodies using flow cytometry in vitro, or immunohistochemistry ex vivo. However, these approaches do not allow for quantitative analysis of the precise anatomical, phenotypic, signaling, and functional parameters required for dissecting the development of immune responses in health and disease in vivo. Traditionally, assessment of signal transduction pathways has required biochemical or molecular biological analysis of isolated and highly purified subsets of immune system cells. Inevitably, this creates potential artifacts and does not allow identification of the key signaling events for individual cells present in their microenvironment in situ. These difficulties have now been overcome by new methodologies in cell signaling analysis that are sufficiently sensitive to detect signaling events occurring in individual cells in situ and the development of technologies such as laser scanning cytometry that provide the tools to analyze physiologically relevant interactions between molecules and cells of the innate and the adaptive immune system within their natural environmental niche in vivo.

Early detection in head and neck cancer - current state and future perspectives

Survival and quality of life in head and neck cancer are directly linked to the size of the primary tumor at first detection. In order to achieve substantial gain at these issues, both, primary prevention and secondary prevention, which is early detection of malignant lesions at a small size, have to be improved. So far, there is not only a lack in the necessary infrastructure not only in Germany, but rather worldwide, but additionally the techniques developed so far for early detection have a significance and specificity too low as to warrant safe implementation for screening programs. However, the advancements recently achieved in endoscopy and in quantitative analysis of hypocellular specimens open new perspectives for secondary prevention. Chromoendoscopy and narrow band imaging (NBI) pinpoint suspicious lesions more easily, confocal endomicroscopy and optical coherence tomography obtain optical sections through those lesions, and hyperspectral imaging classifies lesions according to characteristic spectral signatures. These techniques therefore obtain optical biopsies. Once a "bloody" biopsy has been taken, the plethora of parameters that can be quantified objectively has been increased and could be the basis for an objective and quantitative classification of epithelial lesions (multiparametric cytometry, quantitative histology). Finally, cytomics and proteomics approaches, and lab-on-the-chip technology might help to identify patients at high-risk. Sensitivity and specificity of these approaches have to be validated, yet, and some techniques have to be adapted for the specific conditions for early detection of head and neck cancer. On this background it has to be stated that it is still a long way to go until a population based screening for head and neck cancer is available. The recent results of screening for cancer of the prostate and breast highlight the difficulties implemented in such a task.

Rapid biocompatibility analysis of materials via in vivo fluorescence imaging of mouse models

BACKGROUND

Many materials are unsuitable for medical use because of poor biocompatibility. Recently, advances in the high throughput synthesis of biomaterials has significantly increased the number of potential biomaterials, however current biocompatibility analysis methods are slow and require histological analysis.

METHODOLOGY/PRINCIPAL FINDINGS

Here we develop rapid, non-invasive methods for in vivo quantification of the inflammatory response to implanted biomaterials. Materials were placed subcutaneously in an array format and monitored for host responses as per ISO 10993-6: 2001. Host cell activity in response to these materials was imaged kinetically, in vivo using fluorescent whole animal imaging. Data captured using whole animal imaging displayed similar temporal trends in cellular recruitment of phagocytes to the biomaterials compared to histological analysis.

CONCLUSIONS/SIGNIFICANCE

Histological analysis similarity validates this technique as a novel, rapid approach for screening biocompatibility of implanted materials. Through this technique there exists the possibility to rapidly screen large libraries of polymers in vivo.

Clinical applications of slide-based cytometry--an update

Slide-based cytometric approaches open the possibility to obtain quantitative and objective data from specimens that so far have not been accessible to this kind of analysis. In this review, we will highlight the specific advantages of slide-based cytometry (SBC) and show the applications that have been established for clinical samples. Focuses are cytomic analyses of oncological and hematological samples where the slide-based concept turned out to open new dimensions in understanding underlying cellular networks. We review the recent literature and point out future applications.

Quantitative morphometric measurements using site selective image cytometry of intact tissue

Site selective two-photon tissue image cytometry has previously been successfully applied to measure the number of rare cells in three-dimensional tissue specimens up to cubic millimetres in size. However, the extension of this approach for high-throughput quantification of cellular morphological states has not been demonstrated. In this paper, we report the use of site-selective tissue image cytometry for the study of homologous recombination (HR) events during cell division in the pancreas of transgenic mice. Since HRs are rare events, recombinant cells distribute sparsely inside the organ. A detailed measurement throughout the whole tissue is thus not practical. Instead, the site selective two-photon tissue cytometer incorporates a low magnification, wide field, one-photon imaging subsystem that rapidly identifies regions of interest containing recombinant cell clusters. Subsequently, high-resolution three-dimensional assays based on two-photon microscopy can be performed only in these regions of interest. We further show that three-dimensional morphology extraction algorithms can be used to analyse the resultant high-resolution two-photon image stacks providing information not only on the frequency and the distribution of these recombinant cell clusters and their constituent cells, but also on their morphology.

Comparative overview of flow and image cytometry

This unit considers the issues of which tool to use--flow cytometry or imaging--and under what conditions. In particular, it compares the advantages and disadvantages of flow and image cytometry and provides examples illustrating the proper choice of each technology. The result is a better understanding of why the two technologies are complementary in many applications. It is clear that many scientists use the tools that are familiar to them, often in preference to the best tool. In cases where very advanced and rather expensive technologies are concerned, this is not surprising. However, there are clearly times when one form of cytometry is definitely superior to another. What then constitute the criteria for a decision when both flow cytometry and imaging are available? This unit addresses some of these concerns.

Three-dimensional tissue cytometer based on high-speed multiphoton microscopy

Image cytometry technology has been extended to 3D based on high-speed multiphoton microscopy. This technique allows in situ study of tissue specimens preserving important cell-cell and cell-extracellular matrix interactions. The imaging system was based on high-speed multiphoton microscopy (HSMPM) for 3D deep tissue imaging with minimal photodamage. Using appropriate fluorescent labels and a specimen translation stage, we could quantify cellular and biochemical states of tissues in a high throughput manner. This approach could assay tissue structures with subcellular resolution down to a few hundred micrometers deep. Its throughput could be quantified by the rate of volume imaging: 1.45 mm(3)/h with high resolution. For a tissue containing tightly packed, stratified cellular layers, this rate corresponded to sampling about 200 cells/s. We characterized the performance of 3D tissue cytometer by quantifying rare cell populations in 2D and 3D specimens in vitro. The measured population ratios, which were obtained by image analysis, agreed well with the expected ratios down to the ratio of 1/10(5). This technology was also applied to the detection of rare skin structures based on endogenous fluorophores. Sebaceous glands and a cell cluster at the base of a hair follicle were identified. Finally, the 3D tissue cytometer was applied to detect rare cells that had undergone homologous mitotic recombination in a novel transgenic mouse model, where recombination events could result in the expression of enhanced yellow fluorescent protein in the cells. 3D tissue cytometry based on HSMPM demonstrated its screening capability with high sensitivity and showed the possibility of studying cellular and biochemical states in tissues in situ. This technique will significantly expand the scope of cytometric studies to the biomedical problems where spatial and chemical relationships between cells and their tissue environments are important.

[Cytomics and predictive medicine for oncology]

One hundred and fifty years after Virchow introduced his fundamental concept of cellular pathology, we now have tools that allow us to unravel the mechanisms of single living cells on a previously unprecedented level of detail. By exploring the molecular cellular phenotype, multiparametric cytometry not only detects specific cellular functions in general but also offers insights into the interaction of single subunits of proteins (e.g., growth factor receptors). Several quantitative and objective techniques allow analysis of single-cell preparations as well as tissue sections to obtain data on different cellular parameters. This opens the way to quantitative and objective histology, which in the future may be possible even without blood or the need to make an incision. To use this huge amount of data for treatment decisions in an individual patient, novel bioinformatic concepts are needed in order to predict the individual course of a disease. The concept of cytomics centers on the cell as the integral unit of all life and explores diseases starting from the cell and going to subcellular units (top-down analysis).

Cytomics - importance of multimodal analysis of cell function and proliferation in oncology

Cancer is a highly complex and heterogeneous disease involving a succession of genetic changes (frequently caused or accompanied by exogenous trauma), and resulting in a molecular phenotype that in turn results in a malignant specification. The development of malignancy has been described as a multistep process involving self-sufficiency in growth signals, insensitivity to antigrowth signals, evasion of apoptosis, limitless replicative potential, sustained angiogenesis, and finally tissue invasion and metastasis. The quantitative analysis of networking molecules within the cells might be applied to understand native-state tissue signalling biology, complex drug actions and dysfunctional signalling in transformed cells, that is, in cancer cells. High-content and high-throughput single-cell analysis can lead to systems biology and cytomics. The application of cytomics in cancer research and diagnostics is very broad, ranging from the better understanding of the tumour cell biology to the identification of residual tumour cells after treatment, to drug discovery. The ultimate goal is to pinpoint in detail these processes on the molecular, cellular and tissue level. A comprehensive knowledge of these will require tissue analysis, which is multiplex and functional; thus, vast amounts of data are being collected from current genomic and proteomic platforms for integration and interpretation as well as for new varieties of updated cytomics technology. This overview will briefly highlight the most important aspects of this continuously developing field.

A three-symbol code for organized proteomes based on cyclical imaging of protein locations

BACKGROUND

A major challenge in the post genomic era is to map and decipher the functional molecular networks of proteins directly in a cell or a tissue. This task requires technologies for the colocalization of random numbers of different molecular components (e.g. proteins) in one sample in one experiment.

METHODS

Multi-epitope-ligand-"kartographie" (MELK) was developed as a microscopic imaging technology running cycles of iterative fluorescence tagging, imaging, and bleaching, to colocalize a large number of proteins in one sample (morphologically intact routinely fixed cells or tissue).

RESULTS

In the present study, 18 different cell surface proteins were colocalized by MELK in cells and tissue sections in different compartments of the human immune system. From the resulting sets of multidimensional binary vectors the most prominent groups of protein-epitope arrangements were extracted and imaged as protein "toponome" maps providing direct insight in the higher order topological organization of immune compartments uncovering new tissue domains. The data sets suggest that protein networks, topologically organized in proteomes in situ, obey a unique protein-colocation and -anticolocation code describable by three symbols.

CONCLUSION

The technology has the potential to colocalize hundreds of proteins and other molecular components in one sample and may offer many applications in biology and medicine.

A practical method to determine the amount of tissue to analyze using laser scanning cytometry

BACKGROUND

Laser scanning cytometry (LSC) is a new technology similar to flow cytometry but generates data from analysis of successive microscopic fields. Unlike its use in other applications, LSC-generated data are not random when used for tissue sections, but are dependent on the microanatomy of the tissue and the distribution and expression of the protein under investigation. For valid LSC analysis, the data generated requires the evaluation of a sufficient tissue area to ensure an accurate representation of expression within the tissue of interest.

METHODS

In this report, we describe a simple and common sense method for determining the area of tissue required for sound LSC analysis by tracking the variation in the measure of target expression with increasing number of fields until it approaches zero.

RESULTS

This approach was used to evaluate the expression of immunohistochemical markers with differing tissue distributions in liver (PMP70, CYP1A2, and Ki67 positive macrophages) and a colorectal adenocarcinoma (activated caspase-3 positive cells), which exhibited diffuse, regional (centrilobular), random, and irregular distribution patterns respectively.

CONCLUSIONS

Analyses of these markers demonstrated that the amount of tissue area required to reach a steady measure of a parameter increased with increasing variability of the tissue distribution.

Laser scanning cytometry in the characterization of the proapoptotic effects of transiently transfected genes in cerebellar granule neurons

BACKGROUND

Low transient transfection efficiency limits the ability to characterize putative proapoptotic gene function in neurons. Laser scanning cytometry (LSC), with its high capacity, medium throughput means of collecting fluorescent emissions from cultured cells, offers an effective technology for scoring cell death in neuronal transfectants.

METHODS

Cerebellar granule neurons (CGNs) were transfected with EGFP-fusion constructs of Caspase-3 and Caspase-9 using a DNA-calcium phosphate coprecipitation method. CGNs were fixed, permeablized, and stained with propidium iodide (PI) nuclear dye. An LSC method, based on a combination of Long Red Max Pixel, Long Red Integral, and Green Integral fluorescence parameters was validated for the scoring of apoptotic cell death in CGNs.

RESULTS

In Caspase-3 and Caspase-9 transfected CGNs, cell death was scored both in transfectants and nontransfected culture-mates. The cell death phenotype was found to be independent of transfection efficiency. LSC scoring of Caspase-9 transfectants was compared with visual scoring following Hoechst 33342 staining, yielding results that were similar qualitatively, but not quantitatively, likely owing to the greater sensitivity to green fluorescence of laser scanning compared to human vision.

CONCLUSION

LSC scoring of transiently transfected CGNs offers a rapid and reliable means of characterizing proapoptotic gene effects.

Slide-based cytometry for cytomics--a minireview

In the postgenomic era, to gain the most detailed quantitative data from biological specimens has become increasingly important in the emerging new fields of high-content and high-throughput single-cell analysis for systems biology and cytomics. Areas of research and diagnosis with the demand to virtually measure "anything" in the cell include immunophenotyping, rare cell detection and characterization in the case of stem cells and residual tumor cells, tissue analysis, and drug discovery. Systemic analysis is also a prerequisite for predictive medicine by genomics, proteomics, and cytomics. This issue of Cytometry Part A is dedicated to innovative concepts of system wide single cells analysis and manipulation, new technologies, data analysis and display, and, finally, quality assessment. The manuscripts to these chapters are provided by cutting edge experts in the fields. This overview will briefly highlight the most important aspects of this continuously developing field.

Extracting quantitative information from tissue--an industrial perspective

The focus of this article is to provide an overview of the current technologies for the pharmaceutical and biotech industry. Disease processes express themselves in the functional and structural disturbance of cellular systems. Cells and their metabolites constitute the building blocks of tissues and entire organisms. Studying the spatial and temporal phenotype of disease processes in tissues at the cellular level reveals a multitude of information about the progress and status of a disease. Detailed exploration of tissues by slide-based cytometry is an important source of information about disease processes. Technological and analytical advances allow us to shed a new light on tissues and to come to a better understanding of the complexity of disease processes. Dealing with complex multidimensional datasets from tissue samples requires an advanced approach to image processing and data management. The increase in computing power and the continuing research into imaging algorithms allow us to improve the exploration of the data content of tissues.

An improved method for discrimination of cell populations in tissue sections using microscopy-based multicolor tissue cytometry

BACKGROUND

In tissue context, researchers and pathologists lack a generally applicable standard for quantitative determination of cytological parameters. Increasing knowledge of disease-specific markers calls for an appropriate in situ tissue cytometry.

METHODS

Microscopy-based multicolor tissue cytometry (MMTC) permits multicolor analysis of single cells within tissue context.

RESULTS

Tissue specimens stained for CD45/CD3/CD4/CD8 were analyzed. Specificity as well as reproducibility of MMTC is demonstrated and a novel MMTC-based function to improve visual discrimination of subpopulations is introduced.

CONCLUSIONS

Our data demonstrate that MMTC constitutes an important step toward automated and quantitative fluorometry of solid tissues and cell monolayers.

Sequential photobleaching of fluorochromes for polychromatic slide-based cytometry

BACKGROUND

Slide-based cytometry is a key technology for polychromatic cytomic investigations. Here we exploit the relocalization and merge feature of Laser Scanning Cytometry for distinguishing fluorochromes of comparable emission spectra but different photostabilities.

METHODS

Blood specimens were stained with the fluorochrome pairs: FITC/ALEXA488, PE/ALEXA532, or APC/ALEXA633. Bleaching was performed by repeated laser excitation.

RESULTS

Since ALEXA dyes are photostable as compared to the conventional fluorochromes FITC, PE, and APC, a differentiation within one fluorochrome pair is possible.

CONCLUSION

The sequential photobleaching method results in an increased information density on a single cell level and represents an important component to perform polychromatic cytometry.

Hyperchromatic cytometry principles for cytomics using slide based cytometry

BACKGROUND

Polychromatic analysis of biological specimens has become increasingly important because of the emerging new fields of high-content and high-throughput single cell analysis for systems biology and cytomics. Combining different technologies and staining methods, multicolor analysis can be pushed forward to measure anything stainable in a cell. We term this approach hyperchromatic cytometry and present different components suitable for achieving this task. For cell analysis, slide based cytometry (SBC) technologies are ideal as, unlike flow cytometry, they are non-consumptive, i.e. the analyzed sample is fixed on the slide and can be reanalyzed following restaining of the object.

METHODS AND RESULTS

We demonstrate various approaches for hyperchromatic analysis on a SBC instrument, the Laser Scanning Cytometer. The different components demonstrated here include (1) polychromatic cytometry (staining of the specimen with eight or more different fluorochromes simultaneously), (2) iterative restaining (using the same fluorochrome for restaining and subsequent reanalysis), (3) differential photobleaching (differentiating fluorochromes by their different photostability), (4) photoactivation (activating fluorescent nanoparticles or photocaged dyes), and (5) photodestruction (destruction of FRET dyes). Based on the ability to relocate cells that are immobilized on a microscope slide with a precision of approximately 1 microm, identical cells can be reanalyzed on the single cell level after manipulation steps.

CONCLUSION

With the intelligent combination of several different techniques, the hyperchromatic cytometry approach allows to quantify and analyze all components of relevance on the single cell level. The information gained per specimen is only limited by the number of available antibodies and sterical hindrance.

Prediction of upper aerodigestive tract cancer by slide-based cytometry

AIM

To evaluate slide-based cytometry in screening for and following up of carcinoma of the upper aerodigestive tract using swabs for a minimal-invasive approach.

METHODS

Laser scanning cytometry (LSC) was used for multiparametric analysis of cells stained for cytokeratin and DNA to determine the DNA-index (DI) of the tumor cells. Histograms with 0.95 < DI < 1.05 and 1.9 < DI < 2.1 were defined as DNA euploid and any other DI as DNA aneuploid. After subsequent HE-staining, single cells were relocalized in order to document morphology. Conventional cytology was also performed on a subset of the slides. Routine histopathology of parallel biopsies served as gold standard in all cases.

RESULTS

115 swabs from 109 patients were obtained from the entire upper aerodigestive tract. 16 swabs were classified as insufficient for LSC. In the remaining 99 specimens, 1 benign lesion was misclassified as malignant, while 61 of the 75 malignant lesions were correctly identified. This corresponds to predictive values of 98.4% and 62.2% for the detection of malignant and benign samples by LSC.

CONCLUSION

This pilot study demonstrates the validity of LSC screening for the identification of tumor malignancy in the upper aerodigestive tract from swab collected cytological material.

Object-oriented image analysis for high content screening: Detailed quantification of cells and sub cellular structures with the Cellenger software

BACKGROUND

Detailed image analysis still is a considerable bottleneck for many cellular assays, and automated solutions to the problem are desirable. However, dealing with the complexity and variability of structures in cellular images makes detailed and reliable analysis a nontrivial task.

METHODS

Therefore, based on the object-oriented image analysis approach, a novel image analysis technology, a flexible and reliable system for image analysis in cellular assays was developed. It contains a library of predefined, adaptable modules, each of them developed for a specific analysis task. The system can be configured easily by combining appropriate modules and adapting them interactively to the specific image data, if necessary. By representing cells and sub cellular structures within a network of interlinked image objects, a large number of parameters can be derived that describe shape, intensity, and relevant structural and relational aspects of any chosen class of structures.

RESULTS

Thus, multi-parameter analysis and multiplexing are supported. A sample application based on this approach demonstrates that GFP signals can be distinguished based on their properties and the relative location within the cell.

“Virtual flow cytometry” of immunostained lymphocytes on microscopic tissue slides:iHCFlow™ tissue cytometry

BACKGROUND

A method and approach is developed for fully automated measurements of immunostained lymphocytes in tissue sections by means of digital color microscopy and patent pending advanced cell analysis. The validation data for population statistic measurements of immunostained lymphocytes in tissue sections using tissue cytometry (TC) is presented. The report is the first to describe the conversion of immunohistochemistry (IHC) data to a flow cytometry-like two parameter dot-plot display, hence the technique is also a virtual flow cytometry. We believe this approach is a paradigm shift, as well as novel, and called the system iHCFlow TC. Seven issues related to technical obstacles to virtual flow cytometry (FC) are identified.

DESIGN

Segmentation of a 512 x 474 RGB image and tabular display of statistical results table took 12-15 s using proprietary developed algorithms. We used a panel of seven antibodies for validation on 14 cases of mantle cell lymphoma giving percentage positive, total lymphocytes, and staining density. A total of 2,027 image frames with 810,800 cell objects (COBs) were evaluated. Antibodies to CD3, CD4, CD8, Bcl-1, Ki-67, CD20, CD5 were subjected to virtual FC on tissue. The results of TC were compared with manual counts of expert observers and with the results of flow cytometric immunophenotyping of the same specimen.

RESULTS

The correlation coefficient and 95% confidence interval by linear regression analysis yielded a high concordance between manual human results (M), FC results, and TC results per antibody, (r = 0.9365 M vs. TC, r= 0.9537 FC vs. TC). The technical issues were resolved and the solutions and results were evaluated and presented.

CONCLUSION

These results suggest the new technology of TC by iHCFlow could be a clinically valid surrogate for both M and FC analysis when only tissue IHC is available for diagnosis and prognosis. The application for cancer diagnosis, monitoring, and prognosis is for objective, rapid, automated counting of immunostained cells in tissues with percentage results. We report a new paradigm in TC that converts IHC staining of lymphocytes to automated results and a flow cytometry-like report. The dot plot histogram display is familiar, intuitive, informative, and provides the pathologists with an automated tool to rapidly characterize the staining and size distribution of the immunoreactive as well as the negative cell population in the tissue. This systems tool is a major improvement over existing ones and satisfies fully the criteria to perform Cytomics (Ecker and Tarnok, Cytometry A 2005;65:1; Ecker and Steiner, Cytometry A 2004;59:182-190; Ecker et al., Cytometry A 2004;59:172-181).

Cytomics, the human cytome project and systems biology: top-down resolution of the molecular biocomplexity of organisms by single cell analysis

A large amount of structural and functional information is obtained by molecular cell phenotype analysis of tissues, organs and organisms at the single cell level by image or flow cytometry in combination with bioinformatic knowledge extraction (cytomics) concerning nuclei acids, proteins and metabolites (cellular genomics, proteomics and metabolomics) as well as cell function parameters like intracellular pH, transmembrane potentials or ion gradients. In addition, differential molecular cell phenotypes between diseased and healthy cells provide molecular data patterns for (i) predictive medicine by cytomics or for (ii) drug discovery purposes using reverse engineering of the data patterns by biomedical cell systems biology. Molecular pathways can be explored in this way including the detection of suitable target molecules, without detailed a priori knowledge of specific disease mechanisms. This is useful during the analysis of complex diseases such as infections, allergies, rheumatoid diseases, diabetes or malignancies. The top-down approach reaching from single cell heterogeneity in cell systems and tissues down to the molecular level seems suitable for a human cytome project to systematically explore the molecular biocomplexity of human organisms. The analysis of already existing data from scientific studies or routine diagnostic procedures will be of immediate value in clinical medicine, for example as personalized therapy by cytomics.

Development of a stereological method to measure levels of fluoropyrimidine metabolizing enzymes in tumor sections using laser scanning cytometry

BACKGROUND

The enzymes thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) influence the activities of fluoropyrimidine anticancer drugs. The sensitivity of cancer cells to capecitabine, which is an oral, tumor-selective pre-prodrug of 5-fluorouracil may correlate better to the TP/DPD ratio than to levels of either enzyme alone. Our goal was to develop a quantitative immunofluorescent method for estimating the levels of TP, DPD, and their ratio in archival tumor sections.

METHODS

Mouse anti-TP and rat anti-DPD monoclonal antibodies were used for parallel indirect immunofluorescent staining. The fluorescence was measured using a laser scanning cytometer (LSC; CompuCyte, Cambridge, MA) in single cells and in sections prepared from cell lines and a human tumor. The phantom contouring feature of the LSC provided a stereologic approach for collecting the fluorescence intensity data from sections.

RESULTS

The relative fluorescence intensities measured in single cells or in sections of the cell lines, using single or double labeling, were similar, supporting the suitability of phantom contouring and two-color staining. Sections of the T-24 and ZR-75-1 cell lines placed on the same slide as the tumor section were used as internal standards for fluorescence measurements. The TP/DPD ratios measured in three cell lines correlated well with the cytotoxicity of 5'-deoxy-5-fluorouridine measured in vitro, indicating that the measurements are related to the biological activity of the drug.

CONCLUSIONS

Plotting the data as contour maps of the topologic distribution of fluorescence intensities in tumor sections allows subsequent histopathologic examination, which may reveal features of the tumors leading to high or low ratios of these enzymes. In addition, this method can be used for any drug target/metabolic system where the key components are known and suitable antibodies are available.

Cytomics--new technologies: towards a human cytome project

BACKGROUND

Molecular cell systems research (cytomics) aims at the understanding of the molecular architecture and functionality of cell systems (cytomes) by single-cell analysis in combination with exhaustive bioinformatic knowledge extraction. In this way, loss of information as a consequence of molecular averaging by cell or tissue homogenisation is avoided.

PROGRESS

The cytomics concept has been significantly advanced by a multitude of current developments. Amongst them are confocal and laser scanning microscopy, multiphoton fluorescence excitation, spectral imaging, fluorescence resonance energy transfer (FRET), fast imaging in flow, optical stretching in flow, and miniaturised flow and image cytometry within laboratories on a chip or laser microdissection, as well as the use of bead arrays. In addition, biomolecular analysis techniques like tyramide signal amplification, single-cell polymerase chain reaction (PCR), and the labelling of biomolecules by quantum dots, magnetic nanobeads, or aptamers open new horizons of sensitivity and molecular specificity at the single-cell level. Data sieving or data mining of the vast amounts of collected multiparameter data for exhaustive multilevel bioinformatic knowledge extraction avoids the inadvertent loss of information from unknown molecular relations being inaccessible to an a priori hypothesis.

CHALLENGE

It seems important to address the challenge of a human cytome project using hypothesis-driven molecular information collection from disease associated cell systems, supplemented by systematic and exhaustive knowledge extraction. This will allow the description of the molecular setup of normal and abnormal cell systems within a relational knowledge system, permitting the standardised discrimination of abnormal cell states in disease. As one of the consequences, individualised predictions of further disease course in patients (predictive medicine by cytomics) by characteristic discriminatory data patterns will permit individualised therapies, identification of new pharmaceutical targets, and establishment of a standardised framework of relevant molecular alterations in disease. This special issue of Cytometry, on new technologies in cytomics, focuses on prominent examples of this presently fast-moving scientific field, and represents one of the preconditions for the formulation of a human cytome project.