Angiogenesis: An Improved In Vitro Biological System and Automated Image-Based Workflow to Aid Identification and Characterization of Angiogenesis and Angiogenic Modulators

Probing single molecule mechanical interactions of syntaxin 1A with native synaptobrevin 2 residing on a secretory vesicle

Interactive mechanical forces between pairs of individual SNARE proteins synaptobrevin 2 (Sb2) and syntaxin 1A (Sx1A) may be sufficient to mediate vesicle docking. This notion, based on force spectroscopy single molecule measurements probing recombinant Sx1A an Sb2 in silico, questioned a predominant view of docking via the ternary SNARE complex formation, which includes an assembly of the intermediate cis binary complex between Sx1A and SNAP25 on the plasma membrane to engage Sb2 on the vesicle. However, whether a trans binary Sx1A-Sb2 complex alone could mediate vesicle docking in a cellular environment remains unclear. To address this issue, we used atomic force microscopy (AFM) in the force spectroscopy mode combined with fluorescence imaging. Using AFM tips functionalized with the full Sx1A cytosolic domain, we probed native Sb2 studding the membrane of secretory vesicles docked at the plasma membrane patches, referred to as "inside-out lawns", identified based on fluorescence stains and prepared from primary culture of lactotrophs. We recorded single molecule Sx1A-Sb2 mechanical interactions and obtained measurements of force (∼183 pN) and extension (∼21.6 nm) necessary to take apart Sx1A-Sb2 binding interactions formed at tip-vesicle contact. Measured interactive force between a single pair of Sx1A-Sb2 molecules is sufficient to hold a single secretory vesicle docked at the plasma membrane within distances up to that of the measured extension. This finding further advances a notion that native vesicle docking can be mediated by a single trans binary Sx1A-Sb2 complex in the absence of SNAP25.

Automated Fluorescence Lifetime Imaging High-Content Analysis of Förster Resonance Energy Transfer between Endogenously Labeled Kinetochore Proteins in Live Budding Yeast Cells

We describe an open-source automated multiwell plate fluorescence lifetime imaging (FLIM) methodology to read out Förster resonance energy transfer (FRET) between fluorescent proteins (FPs) labeling endogenous kinetochore proteins (KPs) in live budding yeast cells. The low copy number of many KPs and their small spatial extent present significant challenges for the quantification of donor fluorescence lifetime in the presence of significant cellular autofluorescence and photobleaching. Automated FLIM data acquisition was controlled by µManager and incorporated wide-field time-gated imaging with optical sectioning to reduce background fluorescence. For data analysis, we used custom MATLAB-based software tools to perform kinetochore foci segmentation and local cellular background subtraction and fitted the fluorescence lifetime data using the open-source FLIMfit software. We validated the methodology using endogenous KPs labeled with mTurquoise2 FP and/or yellow FP and measured the donor fluorescence lifetimes for foci comprising 32 kinetochores with KP copy numbers as low as ~2 per kinetochore under an average labeling efficiency of 50%. We observed changes of median donor lifetime ≥250 ps for KPs known to form dimers. Thus, this FLIM high-content analysis platform enables the screening of relatively low-copy-number endogenous protein-protein interactions at spatially confined macromolecular complexes.

CellProfiler and KNIME: Open-Source Tools for High-Content Screening

High-content screening (HCS) has established itself in the world of the pharmaceutical industry as an essential tool for drug discovery and drug development. HCS is currently starting to enter the academic world and might become a widely used technology. Given the diversity of problems tackled in academic research, HCS could experience some profound changes in the future, mainly with more imaging modalities and smart microscopes being developed. One of the limitations in the establishment of HCS in academia is flexibility and cost. Flexibility is important to be able to adapt the HCS setup to accommodate the multiple different assays typical of academia. Many cost factors cannot be avoided, but the costs of the software packages necessary to analyze large datasets can be reduced by using open-source software. We present and discuss the open-source software CellProfiler for image analysis and KNIME for data analysis and data mining that provide software solutions, which increase flexibility and keep costs low.

Rg1 prevents myocardial hypoxia/reoxygenation injury by regulating mitochondrial dynamics imbalance via modulation of glutamate dehydrogenase and mitofusin 2

PURPOSE

Mitochondrial dysfunction is a prominent feature of ischemia heart disease but the underlying mechanism of dynamics (fusion/fission) is still unclear. Here we investigated a novel function and underlying mechanism of Rg1 on an in vitro cardiomyocyte model of hypoxia/reoxygenation (H/R).

METHODS

Cellular cytotoxicity was evaluated by MTT, mitochondrial viable staining, and cardiac marker detection. Mitochondrial function was evaluated by ATP content measurement, MMP determination, ROS, OCR and ECAR assay. Mitochondrial dynamics was investigated by Live-cell imaging with time-lapse fluorescence microscopy and morphological features were evaluated by the high-content image analysis. Mitochondrial fusion and fission-related proteins, GDH were determined by Western blot, RT-PCR and immunofluorescence.

RESULTS

Rg1 moderated GDH dysregulation and then protected against H/R-induced cellular damage and mitochondrial dysfunction in a dose-dependent manner. Rg1 significantly increased mitochondrial length, reduced the number of cells with fragmented mitochondria and up-regulated the MFN2 expression finally leading to preventing the imbalance of mitochondrial dynamics following H/R. Knock-down of MFN2 by specific siRNA completely abolished the ability of Rg1 to cell survival by H/R.

CONCLUSION

Rg1 through modulation of GDH and MFN2 maintained mitochondrial dynamics that resulted in protection against H/R-induced cardiomyocyte injury. All these results put forward a new protective mechanism of Rg1 on the therapeutic potential in cardiac I/R disorders.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: focus on the cancer hallmark of tumor angiogenesis

One of the important 'hallmarks' of cancer is angiogenesis, which is the process of formation of new blood vessels that are necessary for tumor expansion, invasion and metastasis. Under normal physiological conditions, angiogenesis is well balanced and controlled by endogenous proangiogenic factors and antiangiogenic factors. However, factors produced by cancer cells, cancer stem cells and other cell types in the tumor stroma can disrupt the balance so that the tumor microenvironment favors tumor angiogenesis. These factors include vascular endothelial growth factor, endothelial tissue factor and other membrane bound receptors that mediate multiple intracellular signaling pathways that contribute to tumor angiogenesis. Though environmental exposures to certain chemicals have been found to initiate and promote tumor development, the role of these exposures (particularly to low doses of multiple substances), is largely unknown in relation to tumor angiogenesis. This review summarizes the evidence of the role of environmental chemical bioactivity and exposure in tumor angiogenesis and carcinogenesis. We identify a number of ubiquitous (prototypical) chemicals with disruptive potential that may warrant further investigation given their selectivity for high-throughput screening assay targets associated with proangiogenic pathways. We also consider the cross-hallmark relationships of a number of important angiogenic pathway targets with other cancer hallmarks and we make recommendations for future research. Understanding of the role of low-dose exposure of chemicals with disruptive potential could help us refine our approach to cancer risk assessment, and may ultimately aid in preventing cancer by reducing or eliminating exposures to synergistic mixtures of chemicals with carcinogenic potential.

Mesoscopic in vivo 3-D tracking of sparse cell populations using angular multiplexed optical projection tomography

We describe an angular multiplexed imaging technique for 3-D in vivo cell tracking of sparse cell distributions and optical projection tomography (OPT) with superior time-lapse resolution and a significantly reduced light dose compared to volumetric time-lapse techniques. We demonstrate that using dual axis OPT, where two images are acquired simultaneously at different projection angles, can enable localization and tracking of features in 3-D with a time resolution equal to the camera frame rate. This is achieved with a 200x reduction in light dose compared to an equivalent volumetric time-lapse single camera OPT acquisition with 200 projection angles. We demonstrate the application of this technique to mapping the 3-D neutrophil migration pattern observed over ~25.5 minutes in a live 2 day post-fertilisation transgenic LysC:GFP zebrafish embryo following a tail wound.

Rapid global fitting of large fluorescence lifetime imaging microscopy datasets

Fluorescence lifetime imaging (FLIM) is widely applied to obtain quantitative information from fluorescence signals, particularly using Förster Resonant Energy Transfer (FRET) measurements to map, for example, protein-protein interactions. Extracting FRET efficiencies or population fractions typically entails fitting data to complex fluorescence decay models but such experiments are frequently photon constrained, particularly for live cell or in vivo imaging, and this leads to unacceptable errors when analysing data on a pixel-wise basis. Lifetimes and population fractions may, however, be more robustly extracted using global analysis to simultaneously fit the fluorescence decay data of all pixels in an image or dataset to a multi-exponential model under the assumption that the lifetime components are invariant across the image (dataset). This approach is often considered to be prohibitively slow and/or computationally expensive but we present here a computationally efficient global analysis algorithm for the analysis of time-correlated single photon counting (TCSPC) or time-gated FLIM data based on variable projection. It makes efficient use of both computer processor and memory resources, requiring less than a minute to analyse time series and multiwell plate datasets with hundreds of FLIM images on standard personal computers. This lifetime analysis takes account of repetitive excitation, including fluorescence photons excited by earlier pulses contributing to the fit, and is able to accommodate time-varying backgrounds and instrument response functions. We demonstrate that this global approach allows us to readily fit time-resolved fluorescence data to complex models including a four-exponential model of a FRET system, for which the FRET efficiencies of the two species of a bi-exponential donor are linked, and polarisation-resolved lifetime data, where a fluorescence intensity and bi-exponential anisotropy decay model is applied to the analysis of live cell homo-FRET data. A software package implementing this algorithm, FLIMfit, is available under an open source licence through the Open Microscopy Environment.

Automated fluorescence lifetime imaging plate reader and its application to Förster resonant energy transfer readout of Gag protein aggregation

Fluorescence lifetime measurements can provide quantitative readouts of local fluorophore environment and can be applied to biomolecular interactions via Förster resonant energy transfer (FRET). Fluorescence lifetime imaging (FLIM) can therefore provide a high content analysis (HCA) modality to map protein-protein interactions (PPIs) with applications in drug discovery, systems biology and basic research. We present here an automated multiwell plate reader able to perform rapid unsupervised optically sectioned FLIM of fixed and live biological samples and illustrate its potential to assay PPIs through application to Gag protein aggregation during the HIV life cycle. We demonstrate both hetero-FRET and homo-FRET readouts of protein aggregation and report the first quantitative evaluation of a FLIM HCA assay by generating dose response curves through addition of an inhibitor of Gag myristoylation. Z' factors exceeding 0.6 are realised for this FLIM FRET assay.

CellProfiler and KNIME: open source tools for high content screening

High content screening (HCS) has established itself in the world of the pharmaceutical industry as an essential tool for drug discovery and drug development. HCS is currently starting to enter the academic world and might become a widely used technology. Given the diversity of problems tackled in academic research, HCS could experience some profound changes in the future, mainly with more imaging modalities and smart microscopes being developed. One of the limitations in the establishment of HCS in academia is flexibility and cost. Flexibility is important to be able to adapt the HCS setup to accommodate the multiple different assays typical of academia. Many cost factors cannot be avoided, but the costs of the software packages necessary to analyze large datasets can be reduced by using Open Source software. We present and discuss the Open Source software CellProfiler for image analysis and KNIME for data analysis and data mining that provide software solutions which increase flexibility and keep costs low.

Mesh-loosening quantification of inhibition of angiogenic tube formation through image analysis

Angiogenesis is a key step in tumor development, and anti-angiogenesis processes are important for drug discovery and development. The dose-response relationship for an inhibitor is studied using images of endothelial cells captured in vitro by Matrigel assay. In order to improve the quantification of anti-angiogenic processes for faithful synchronization with continuous variation of an inhibitor dose, we have developed an automated image analysis method-mesh-loosening analysis-to evaluate the disruption of tube formation from endothelial cells. The method is based on numerical and morphological changes of mesh regions surrounded by tubes and perceived by considering the spaces between the tubes rather than the tubes themselves. The anti-angiogenic effect of suramin is analyzed comprehensively using four attributes obtained from the mesh regions. The relation between the dose of suramin and response shows an exponential curve that can be approximated as a sigmoid function, even though human assessments yield strong inhibition at moderate doses. The calculated half-minimal inhibitory concentration was in agreement with prior published reports. The results show that mesh-loosening analysis is useful and appropriate for screening applications that need precise and comprehensive quantification of the anti-angiogenic process to compensate for the inadequacy of human assessment. Feasibility study with shikonin shows the robustness of the mesh-loosening analysis.

Multiphoton multispectral fluorescence lifetime tomography for the evaluation of basal cell carcinomas

We present the first detailed study using multispectral multiphoton fluorescence lifetime imaging to differentiate basal cell carcinoma cells (BCCs) from normal keratinocytes. Images were acquired from 19 freshly excised BCCs and 27 samples of normal skin (in & ex vivo). Features from fluorescence lifetime images were used to discriminate BCCs with a sensitivity/specificity of 79%/93% respectively. A mosaic of BCC fluorescence lifetime images covering >1 mm² is also presented, demonstrating the potential for tumour margin delineation.

Using 10,462 manually segmented cells from the image data, we quantify the cellular morphology and spectroscopic differences between BCCs and normal skin for the first time. Statistically significant increases were found in the fluorescence lifetimes of cells from BCCs in all spectral channels, ranging from 19.9% (425–515 nm spectral emission) to 39.8% (620–655 nm emission). A discriminant analysis based diagnostic algorithm allowed the fraction of cells classified as malignant to be calculated for each patient. This yielded a receiver operator characteristic area under the curve for the detection of BCC of 0.83.

We have used both morphological and spectroscopic parameters to discriminate BCC from normal skin, and provide a comprehensive base for how this technique could be used for BCC assessment in clinical practice.

Phenotype-based high-content chemical library screening identifies statins as inhibitors of in vivo lymphangiogenesis

Lymphangiogenesis plays an important role in promoting cancer metastasis to sentinel lymph nodes and beyond and also promotes organ transplant rejection. We used human lymphatic endothelial cells to establish a reliable three-dimensional lymphangiogenic sprouting assay with automated image acquisition and analysis for inhibitor screening. This high-content phenotype-based assay quantifies sprouts by automated fluorescence microscopy and newly developed analysis software. We identified signaling pathways involved in lymphangiogenic sprouting by screening the Library of Pharmacologically Active Compounds (LOPAC)(1280) collection of pharmacologically relevant compounds. Hit characterization revealed that mitogen-activated protein kinase kinase (MEK) 1/2 inhibitors substantially block lymphangiogenesis in vitro and in vivo. Importantly, the drug class of statins, for the first time, emerged as potent inhibitors of lymphangiogenic sprouting in vitro and of corneal and cutaneous lymphangiogenesis in vivo. This effect was mediated by inhibition of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and subsequently the isoprenylation of Rac1. Supplementation with the enzymatic products of HMG-CoA reductase functionally rescued lymphangiogenic sprouting and the recruitment of Rac1 to the plasma membrane.

Review Article: High-Content Screening: A Decade of Evolution

In the past decade, high-content screening has become a highly developed approach to obtaining richly descriptive quantitative phenotypic data using automated microscopy. From early use in drug screening, the technique has evolved to embrace a diverse range of applications in both academic and industrial sectors and is now widely recognized as providing an efficient and effective approach to large-scale programs investigating cell biology in situ and in context.

Computer-aided Image Processing of Angiogenic Histological

This article reviews the questions regarding the image evaluation of angiogeneic histological samples, particularly the ovarian epithelial cancer. Review is focused on the principles of image analysis in the field of histology and pathology. The definition, classification, pathogenesis and angiogenesis regulation in the ovaries are also briefly discussed. It is hoped that the complex image analysis together with the patient's clinical parameters will allow an acquiring of a clear pathogenic picture of the disease, extension of the differential diagnosis and become a useful tool for the evaluation of drug effects. The challenge of the assessment of angiogenesis activity is the heterogeneity of several objects: parameters derived from patient's anamnesis as well as of pathology samples. The other unresolved problems are the subjectivity of the region of interest selection and performance of the whole slide scanning.

KEYWORDS

Angiogenesis; Image processing; Microvessel density; Cancer; Pathology.

Microscopy-based HTS examines the mechanism of stress F-actin fiber disruption by cytochalasin D: orientation texture data collated with quantitative kinetic modeling

We report a drug dose-response, end-point study of intracellular filamentous actin (F-actin) by automated fluorescence microscopy, complemented with theoretical kinetic simulation of drug action. We highlight the use of an advanced orientation-sensitive image processing procedure (<cos(2)theta> transform), specially tailored for the detection of ordered filamentous "patches" in cell images. To examine the extent of stress F-actin disruption caused by the drug, we compare the measured response based on the above transformation with the theoretical data obtained from a quantitative model. We show that the assay data are consistent with the first-order mass action kinetics predicted by a basic reaction model. As a concluding remark, we briefly discuss advantages, perspectives, and challenges of conventional fluorescent microscopy within the context of the quantitative high-throughput screening paradigm.