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Pubmed Article
Memo has a novel role in S1P signaling and crucial for vascular development.
PLoS ONE
PUBLISHED: 01-01-2014
Memo is a conserved protein that was identified as an essential mediator of tumor cell motility induced by receptor tyrosine kinase activation. Here we show that Memo null mouse embryonic fibroblasts (MEFs) are impaired in PDGF-induced migration and this is due to a defect in sphingosine-1-phosphate (S1P) signaling. S1P is a bioactive phospholipid produced in response to multiple stimuli, which regulates many cellular processes. S1P is secreted to the extracellular milieu where it exerts its function by binding a family of G-protein coupled receptors (S1PRs), causing their activation in an autocrine or paracrine manner. The process, termed cell-autonomous S1PR signaling, plays a role in survival and migration. Indeed, PDGF uses cell-autonomous S1PR signaling to promote cell migration; we show here that this S1P pathway requires Memo. Using vascular endothelial cells (HUVECs) with Memo knock-down we show that their survival in conditions of serum-starvation is impaired. Furthermore, Memo loss in HUVECs causes a reduction of junctional VE-cadherin and an increase in sprout formation. Each of these phenotypes is rescued by S1P or S1P agonist addition, showing that Memo also plays an important role in cell-autonomous S1PR signaling in endothelial cells. We also produced conventional and endothelial cell-specific conditional Memo knock-out mouse strains and show that Memo is essential for embryonic development. Starting at E13.5 embryos of both strains display bleeding and other vascular problems, some of the phenotypes that have been described in mouse strains lacking S1PRs. The essential role of Memo in embryonic vascular development may be due in part to alterations in S1P signaling. Taken together our results show that Memo has a novel role in the S1P pathway and that Memo is needed to promote cell-autonomous S1PR activation.
ABSTRACT
Metastasis is a process in which tumor cells shed from the primary tumor intravasate blood vascular and lymphatic system, thereby, gaining access to extravasate and form a secondary niche. The extravasation of tumor cells from the blood vascular system can be studied using endothelial cells (ECs) and tumor cells obtained from different cell lines. Initial studies were conducted using static conditions but it has been well documented that ECs behave differently under physiological flow conditions. Therefore, different flow chamber assemblies are currently being used to studying cancer cell interactions with ECs. Current flow chamber assemblies offer reproducible results using either different cell lines or fluid at different shear stress conditions. However, to observe and study interactions with rare cells such as circulating tumor cells (CTCs), certain changes are required to be made to the conventional flow chamber assembly. CTCs are a rare cell population among millions of blood cells. Consequently, it is difficult to obtain a pure population of CTCs. Contamination of CTCs with different types of cells normally found in the circulation is inevitable using present enrichment or depletion techniques. In the present report, we describe a unique method to fluorescently label circulating prostate cancer cells and study their interactions with ECs in a self-assembled flow chamber system. This technique can be further applied to observe interactions between prostate CTCs and any protein of interest.
24 Related JoVE Articles!
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Visualization of Vascular Ca2+ Signaling Triggered by Paracrine Derived ROS
Authors: Karthik Mallilankaraman, Rajesh Kumar Gandhirajan, Brian J. Hawkins, Muniswamy Madesh.
Institutions: Temple University , University of Washington.
Oxidative stress has been implicated in a number of pathologic conditions including ischemia/reperfusion damage and sepsis. The concept of oxidative stress refers to the aberrant formation of ROS (reactive oxygen species), which include O2•-, H2O2, and hydroxyl radicals. Reactive oxygen species influences a multitude of cellular processes including signal transduction, cell proliferation and cell death1-6. ROS have the potential to damage vascular and organ cells directly, and can initiate secondary chemical reactions and genetic alterations that ultimately result in an amplification of the initial ROS-mediated tissue damage. A key component of the amplification cascade that exacerbates irreversible tissue damage is the recruitment and activation of circulating inflammatory cells. During inflammation, inflammatory cells produce cytokines such as tumor necrosis factor-α (TNFα) and IL-1 that activate endothelial cells (EC) and epithelial cells and further augment the inflammatory response7. Vascular endothelial dysfunction is an established feature of acute inflammation. Macrophages contribute to endothelial dysfunction during inflammation by mechanisms that remain unclear. Activation of macrophages results in the extracellular release of O2•- and various pro-inflammatory cytokines, which triggers pathologic signaling in adjacent cells8. NADPH oxidases are the major and primary source of ROS in most of the cell types. Recently, it is shown by us and others9,10 that ROS produced by NADPH oxidases induce the mitochondrial ROS production during many pathophysiological conditions. Hence measuring the mitochondrial ROS production is equally important in addition to measuring cytosolic ROS. Macrophages produce ROS by the flavoprotein enzyme NADPH oxidase which plays a primary role in inflammation. Once activated, phagocytic NADPH oxidase produces copious amounts of O2•- that are important in the host defense mechanism11,12. Although paracrine-derived O2•- plays an important role in the pathogenesis of vascular diseases, visualization of paracrine ROS-induced intracellular signaling including Ca2+ mobilization is still hypothesis. We have developed a model in which activated macrophages are used as a source of O2•- to transduce a signal to adjacent endothelial cells. Using this model we demonstrate that macrophage-derived O2•- lead to calcium signaling in adjacent endothelial cells.
Molecular Biology, Issue 58, Reactive oxygen species, Calcium, paracrine superoxide, endothelial cells, confocal microscopy
3511
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Isolation and Culture of Pulmonary Endothelial Cells from Neonatal Mice
Authors: Magdalena Sobczak, Jillian Dargatz, Magdalena Chrzanowska-Wodnicka.
Institutions: BloodCenter of Wisconsin.
Endothelial cells provide a useful research model in many areas of vascular biology. Since its first isolation 1, human umbilical vein endothelial cells (HUVECs) have shown to be convenient, easy to obtain and culture, and thus are the most widely studied endothelial cells. However, for research focused on processes like angiogenesis, permeability or many others, microvascular endothelial cells (ECs) are a much more physiologically relevant model to study 2. Furthermore, ECs isolated from knockout mice provide a useful tool for analysis of protein function ex vivo. Several approaches to isolate and culture microvascular ECs of different origin have been reported to date 3-7, but consistent isolation and culture of pure ECs is still a major technical problem in many laboratories. Here, we provide a step-by-step protocol on a reliable and relatively simple method of isolating and culturing mouse lung endothelial cells (MLECs). In this approach, lung tissue obtained from 6- to 8-day old pups is first cut into pieces, digested with collagenase/dispase (C/D) solution and dispersed mechanically into single-cell suspension. MLECS are purified from cell suspension using positive selection with anti-PECAM-1 antibody conjugated to Dynabeads using a Magnetic Particle Concentrator (MPC). Such purified cells are cultured on gelatin-coated tissue culture (TC) dishes until they become confluent. At that point, cells are further purified using Dynabeads coupled to anti-ICAM-2 antibody. MLECs obtained with this protocol exhibit a cobblestone phenotype, as visualized by phase-contrast light microscopy, and their endothelial phenotype has been confirmed using FACS analysis with anti-VE-cadherin 8 and anti-VEGFR2 9 antibodies and immunofluorescent staining of VE-cadherin. In our hands, this two-step isolation procedure consistently and reliably yields a pure population of MLECs, which can be further cultured. This method will enable researchers to take advantage of the growing number of knockout and transgenic mice to directly correlate in vivo studies with results of in vitro experiments performed on isolated MLECs and thus help to reveal molecular mechanisms of vascular phenotypes observed in vivo.
Cellular Biology, Issue 46, Endothelium, lung, microvascular cells, mouse, isolation, angiogenesis, vascular permeability, adherens junctions
2316
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Induction and Analysis of Epithelial to Mesenchymal Transition
Authors: Yixin Tang, Greg Herr, Wade Johnson, Ernesto Resnik, Joy Aho.
Institutions: R&D Systems, Inc., R&D Systems, Inc..
Epithelial to mesenchymal transition (EMT) is essential for proper morphogenesis during development. Misregulation of this process has been implicated as a key event in fibrosis and the progression of carcinomas to a metastatic state. Understanding the processes that underlie EMT is imperative for the early diagnosis and clinical control of these disease states. Reliable induction of EMT in vitro is a useful tool for drug discovery as well as to identify common gene expression signatures for diagnostic purposes. Here we demonstrate a straightforward method for the induction of EMT in a variety of cell types. Methods for the analysis of cells pre- and post-EMT induction by immunocytochemistry are also included. Additionally, we demonstrate the effectiveness of this method through antibody-based array analysis and migration/invasion assays.
Molecular Biology, Issue 78, Cellular Biology, Biochemistry, Biomedical Engineering, Stem Cell Biology, Cancer Biology, Medicine, Bioengineering, Anatomy, Physiology, biology (general), Pathological Conditions, Signs and Symptoms, Wounds and Injuries, Neoplasms, Diagnosis, Therapeutics, Epithelial to mesenchymal transition, EMT, cancer, metastasis, cancer stem cell, cell, assay, immunohistochemistry
50478
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Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum
Authors: Xuehua Xu, Tian Jin.
Institutions: National Institute of Allergy and Infectious Diseases, National Institutes of Health.
Many eukaryotic cells can detect gradients of chemical signals in their environments and migrate accordingly 1. This guided cell migration is referred as chemotaxis, which is essential for various cells to carry out their functions such as trafficking of immune cells and patterning of neuronal cells 2, 3. A large family of G-protein coupled receptors (GPCRs) detects variable small peptides, known as chemokines, to direct cell migration in vivo 4. The final goal of chemotaxis research is to understand how a GPCR machinery senses chemokine gradients and controls signaling events leading to chemotaxis. To this end, we use imaging techniques to monitor, in real time, spatiotemporal concentrations of chemoattractants, cell movement in a gradient of chemoattractant, GPCR mediated activation of heterotrimeric G-protein, and intracellular signaling events involved in chemotaxis of eukaryotic cells 5-8. The simple eukaryotic organism, Dictyostelium discoideum, displays chemotaxic behaviors that are similar to those of leukocytes, and D. discoideum is a key model system for studying eukaryotic chemotaxis. As free-living amoebae, D. discoideum cells divide in rich medium. Upon starvation, cells enter a developmental program in which they aggregate through cAMP-mediated chemotaxis to form multicullular structures. Many components involved in chemotaxis to cAMP have been identified in D. discoideum. The binding of cAMP to a GPCR (cAR1) induces dissociation of heterotrimeric G-proteins into Gγ and Gβγ subunits 7, 9, 10. Gβγ subunits activate Ras, which in turn activates PI3K, converting PIP2 into PIP3 on the cell membrane 11-13. PIP3 serve as binding sites for proteins with pleckstrin Homology (PH) domains, thus recruiting these proteins to the membrane 14, 15. Activation of cAR1 receptors also controls the membrane associations of PTEN, which dephosphorylates PIP3 to PIP2 16, 17. The molecular mechanisms are evolutionarily conserved in chemokine GPCR-mediated chemotaxis of human cells such as neutrophils 18. We present following methods for studying chemotaxis of D. discoideum cells. 1. Preparation of chemotactic component cells. 2. Imaging chemotaxis of cells in a cAMP gradient. 3. Monitoring a GPCR induced activation of heterotrimeric G-protein in single live cells. 4. Imaging chemoattractant-triggered dynamic PIP3 responses in single live cells in real time. Our developed imaging methods can be applied to study chemotaxis of human leukocytes.
Molecular Biology, Issue 55, Chemotaxis, directional sensing, GPCR, PCR, G-proteins, signal transduction, Dictyostelium discoideum
3128
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Isolation of Pulmonary Artery Smooth Muscle Cells from Neonatal Mice
Authors: Keng Jin Lee, Lyubov Czech, Gregory B. Waypa, Kathryn N. Farrow.
Institutions: Northwestern University Feinberg School of Medicine.
Pulmonary hypertension is a significant cause of morbidity and mortality in infants. Historically, there has been significant study of the signaling pathways involved in vascular smooth muscle contraction in PASMC from fetal sheep. While sheep make an excellent model of term pulmonary hypertension, they are very expensive and lack the advantage of genetic manipulation found in mice. Conversely, the inability to isolate PASMC from mice was a significant limitation of that system. Here we described the isolation of primary cultures of mouse PASMC from P7, P14, and P21 mice using a variation of the previously described technique of Marshall et al.26 that was previously used to isolate rat PASMC. These murine PASMC represent a novel tool for the study of signaling pathways in the neonatal period. Briefly, a slurry of 0.5% (w/v) agarose + 0.5% iron particles in M199 media is infused into the pulmonary vascular bed via the right ventricle (RV). The iron particles are 0.2 μM in diameter and cannot pass through the pulmonary capillary bed. Thus, the iron lodges in the small pulmonary arteries (PA). The lungs are inflated with agarose, removed and dissociated. The iron-containing vessels are pulled down with a magnet. After collagenase (80 U/ml) treatment and further dissociation, the vessels are put into a tissue culture dish in M199 media containing 20% fetal bovine serum (FBS), and antibiotics (M199 complete media) to allow cell migration onto the culture dish. This initial plate of cells is a 50-50 mixture of fibroblasts and PASMC. Thus, the pull down procedure is repeated multiple times to achieve a more pure PASMC population and remove any residual iron. Smooth muscle cell identity is confirmed by immunostaining for smooth muscle myosin and desmin.
Basic Protocol, Issue 80, Muscle, Smooth, Vascular, Cardiovascular Abnormalities, Hypertension, Pulmonary, vascular smooth muscle, pulmonary hypertension, development, phosphodiesterases, cGMP, immunostaining
50889
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Humanized Mouse Model to Study Bacterial Infections Targeting the Microvasculature
Authors: Keira Melican, Flore Aubey, Guillaume Duménil.
Institutions: Paris Cardiovascular Research Centre, Université Paris Descartes.
Neisseria meningitidis causes a severe, frequently fatal sepsis when it enters the human blood stream. Infection leads to extensive damage of the blood vessels resulting in vascular leak, the development of purpuric rashes and eventual tissue necrosis. Studying the pathogenesis of this infection was previously limited by the human specificity of the bacteria, which makes in vivo models difficult. In this protocol, we describe a humanized model for this infection in which human skin, containing dermal microvessels, is grafted onto immunocompromised mice. These vessels anastomose with the mouse circulation while maintaining their human characteristics. Once introduced into this model, N. meningitidis adhere exclusively to the human vessels, resulting in extensive vascular damage, inflammation and in some cases the development of purpuric rash. This protocol describes the grafting, infection and evaluation steps of this model in the context of N. meningitidis infection. The technique may be applied to numerous human specific pathogens that infect the blood stream.
Infection, Issue 86, Disease Models, Bacteria, Bacterial Infections and Mycoses, Neisseria meningitidis, purpura, vascular infection, humanized model
51134
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Mouse Models for Graft Arteriosclerosis
Authors: Lingfeng Qin, Luyang Yu, Wang Min.
Institutions: Yale University School of Medicine , Yale University School of Medicine .
Graft arteriosclerois (GA), also called allograft vasculopathy, is a pathologic lesion that develops over months to years in transplanted organs characterized by diffuse, circumferential stenosis of the entire graft vascular tree. The most critical component of GA pathogenesis is the proliferation of smooth muscle-like cells within the intima. When a human coronary artery segment is interposed into the infra-renal aortae of immunodeficient mice, the intimas could be expand in response to adoptively transferred human T cells allogeneic to the artery donor or exogenous human IFN-γ in the absence of human T cells. Interposition of a mouse aorta from one strain into another mouse strain recipient is limited as a model for chronic rejection in humans because the acute cell-mediated rejection response in this mouse model completely eliminates all donor-derived vascular cells from the graft within two-three weeks. We have recently developed two new mouse models to circumvent these problems. The first model involves interposition of a vessel segment from a male mouse into a female recipient of the same inbred strain (C57BL/6J). Graft rejection in this case is directed only against minor histocompatibility antigens encoded by the Y chromosome (present in the male but not the female) and the rejection response that ensues is sufficiently indolent to preserve donor-derived smooth muscle cells for several weeks. The second model involves interposing an artery segment from a wild type C57BL/6J mouse donor into a host mouse of the same strain and gender that lacks the receptor for IFN-γ followed by administration of mouse IFN-γ (delivered via infection of the mouse liver with an adenoviral vector. There is no rejection in this case as both donor and recipient mice are of the same strain and gender but donor smooth muscle cells proliferate in response to the cytokine while host-derived cells, lacking receptor for this cytokine, are unresponsive. By backcrossing additional genetic changes into the vessel donor, both models can be used to assess the effect of specific genes on GA progression. Here, we describe detailed protocols for our mouse GA models.
Medicine, Issue 75, Anatomy, Physiology, Biomedical Engineering, Bioengineering, Cardiology, Pathology, Surgery, Tissue Engineering, Cardiovascular Diseases, vascular biology, graft arteriosclerosis, GA, mouse models, transplantation, graft, vessels, arteries, mouse, animal model, surgical techniques
50290
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Mouse Embryonic Development in a Serum-free Whole Embryo Culture System
Authors: Vijay K. Kalaskar, James D. Lauderdale.
Institutions: University of Georgia, University of Georgia.
Mid-gestation stage mouse embryos were cultured utilizing a serum-free culture medium prepared from commercially available stem cell media supplements in an oxygenated rolling bottle culture system. Mouse embryos at E10.5 were carefully isolated from the uterus with intact yolk sac and in a process involving precise surgical maneuver the embryos were gently exteriorized from the yolk sac while maintaining the vascular continuity of the embryo with the yolk sac. Compared to embryos prepared with intact yolk sac or with the yolk sac removed, these embryos exhibited superior survival rate and developmental progression when cultured under similar conditions. We show that these mouse embryos, when cultured in a defined medium in an atmosphere of 95% O2 / 5% CO2 in a rolling bottle culture apparatus at 37 °​C for 16-40 hr, exhibit morphological growth and development comparable to the embryos developing in utero. We believe this method will be useful for investigators needing to utilize whole embryo culture to study signaling interactions important in embryonic organogenesis.
Developmental Biology, Issue 85, mouse embryo, mid-gestation, serum-free, defined media, roller culture, organogenesis, development
50803
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Assessment of Vascular Regeneration in the CNS Using the Mouse Retina
Authors: Khalil Miloudi, Agnieszka Dejda, François Binet, Eric Lapalme, Agustin Cerani, Przemyslaw Sapieha.
Institutions: McGill University, University of Montréal, University of Montréal.
The rodent retina is perhaps the most accessible mammalian system in which to investigate neurovascular interplay within the central nervous system (CNS). It is increasingly being recognized that several neurodegenerative diseases such as Alzheimer’s, multiple sclerosis, and amyotrophic lateral sclerosis present elements of vascular compromise. In addition, the most prominent causes of blindness in pediatric and working age populations (retinopathy of prematurity and diabetic retinopathy, respectively) are characterized by vascular degeneration and failure of physiological vascular regrowth. The aim of this technical paper is to provide a detailed protocol to study CNS vascular regeneration in the retina. The method can be employed to elucidate molecular mechanisms that lead to failure of vascular growth after ischemic injury. In addition, potential therapeutic modalities to accelerate and restore healthy vascular plexuses can be explored. Findings obtained using the described approach may provide therapeutic avenues for ischemic retinopathies such as that of diabetes or prematurity and possibly benefit other vascular disorders of the CNS.
Neuroscience, Issue 88, vascular regeneration, angiogenesis, vessels, retina, neurons, oxygen-induced retinopathy, neovascularization, CNS
51351
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Videomorphometric Analysis of Hypoxic Pulmonary Vasoconstriction of Intra-pulmonary Arteries Using Murine Precision Cut Lung Slices
Authors: Renate Paddenberg, Petra Mermer, Anna Goldenberg, Wolfgang Kummer.
Institutions: Justus-Liebig-University.
Acute alveolar hypoxia causes pulmonary vasoconstriction (HPV) - also known as von Euler-Liljestrand mechanism - which serves to match lung perfusion to ventilation. Up to now, the underlying mechanisms are not fully understood. The major vascular segment contributing to HPV is the intra-acinar artery. This vessel section is responsible for the blood supply of an individual acinus, which is defined as the portion of lung distal to a terminal bronchiole. Intra-acinar arteries are mostly located in that part of the lung that cannot be selectively reached by a number of commonly used techniques such as measurement of the pulmonary artery pressure in isolated perfused lungs or force recordings from dissected proximal pulmonary artery segments1,2. The analysis of subpleural vessels by real-time confocal laser scanning luminescence microscopy is limited to vessels with up to 50 µm in diameter3. We provide a technique to study HPV of murine intra-pulmonary arteries in the range of 20-100 µm inner diameters. It is based on the videomorphometric analysis of cross-sectioned arteries in precision cut lung slices (PCLS). This method allows the quantitative measurement of vasoreactivity of small intra-acinar arteries with inner diameter between 20-40 µm which are located at gussets of alveolar septa next to alveolar ducts and of larger pre-acinar arteries with inner diameters between 40-100 µm which run adjacent to bronchi and bronchioles. In contrast to real-time imaging of subpleural vessels in anesthetized and ventilated mice, videomorphometric analysis of PCLS occurs under conditions free of shear stress. In our experimental model both arterial segments exhibit a monophasic HPV when exposed to medium gassed with 1% O2 and the response fades after 30-40 min at hypoxia.
Medicine, Issue 83, Hypoxic pulmonary vasoconstriction, murine lungs, precision cut lung slices, intra-pulmonary, pre- and intra-acinar arteries, videomorphometry
50970
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Dissecting Host-virus Interaction in Lytic Replication of a Model Herpesvirus
Authors: Xiaonan Dong, Pinghui Feng.
Institutions: UT Southwestern Medical Center, UT Southwestern Medical Center.
In response to viral infection, a host develops various defensive responses, such as activating innate immune signaling pathways that lead to antiviral cytokine production1,2. In order to colonize the host, viruses are obligate to evade host antiviral responses and manipulate signaling pathways. Unraveling the host-virus interaction will shed light on the development of novel therapeutic strategies against viral infection. Murine γHV68 is closely related to human oncogenic Kaposi's sarcoma-associated herpesvirus and Epsten-Barr virus3,4. γHV68 infection in laboratory mice provides a tractable small animal model to examine the entire course of host responses and viral infection in vivo, which are not available for human herpesviruses. In this protocol, we present a panel of methods for phenotypic characterization and molecular dissection of host signaling components in γHV68 lytic replication both in vivo and ex vivo. The availability of genetically modified mouse strains permits the interrogation of the roles of host signaling pathways during γHV68 acute infection in vivo. Additionally, mouse embryonic fibroblasts (MEFs) isolated from these deficient mouse strains can be used to further dissect roles of these molecules during γHV68 lytic replication ex vivo. Using virological and molecular biology assays, we can pinpoint the molecular mechanism of host-virus interactions and identify host and viral genes essential for viral lytic replication. Finally, a bacterial artificial chromosome (BAC) system facilitates the introduction of mutations into the viral factor(s) that specifically interrupt the host-virus interaction. Recombinant γHV68 carrying these mutations can be used to recapitulate the phenotypes of γHV68 lytic replication in MEFs deficient in key host signaling components. This protocol offers an excellent strategy to interrogate host-pathogen interaction at multiple levels of intervention in vivo and ex vivo. Recently, we have discovered that γHV68 usurps an innate immune signaling pathway to promote viral lytic replication5. Specifically, γHV68 de novo infection activates the immune kinase IKKβ and activated IKKβ phosphorylates the master viral transcription factor, replication and transactivator (RTA), to promote viral transcriptional activation. In doing so, γHV68 efficiently couples its transcriptional activation to host innate immune activation, thereby facilitating viral transcription and lytic replication. This study provides an excellent example that can be applied to other viruses to interrogate host-virus interaction.
Immunology, Issue 56, herpesvirus, gamma herpesvirus 68, γHV68, signaling pathways, host-virus interaction, viral lytic replication
3140
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An in vivo Assay to Test Blood Vessel Permeability
Authors: Maria Radu, Jonathan Chernoff.
Institutions: Fox Chase Cancer Center .
This method is based on the intravenous injection of Evans Blue in mice as the test animal model. Evans blue is a dye that binds albumin. Under physiologic conditions the endothelium is impermeable to albumin, so Evans blue bound albumin remains restricted within blood vessels. In pathologic conditions that promote increased vascular permeability endothelial cells partially lose their close contacts and the endothelium becomes permeable to small proteins such as albumin. This condition allows for extravasation of Evans Blue in tissues. A healthy endothelium prevents extravasation of the dye in the neighboring vascularized tissues. Organs with increased permeability will show significantly increased blue coloration compared to organs with intact endothelium. The level of vascular permeability can be assessed by simple visualization or by quantitative measurement of the dye incorporated per milligram of tissue of control versus experimental animal/tissue. Two powerful aspects of this assay are its simplicity and quantitative characteristics. Evans Blue dye can be extracted from tissues by incubating a specific amount of tissue in formamide. Evans Blue absorbance maximum is at 620 nm and absorbance minimum is at 740 nm. By using a standard curve for Evans Blue, optical density measurements can be converted into milligram dye captured per milligram of tissue. Statistical analysis should be used to assess significant differences in vascular permeability.
Medicine, Issue 73, Immunology, Physiology, Anatomy, Surgery, Hematology, Blood Vessels, Endothelium, Vascular, Vascular Cell Adhesion Molecule-1, permeability, in vivo, Evans Blue, Miles assay, assay, intravenous injection, mouse, animal model
50062
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Real-time Imaging of Endothelial Cell-cell Junctions During Neutrophil Transmigration Under Physiological Flow
Authors: Jeffrey Kroon, Anna E. Daniel, Mark Hoogenboezem, Jaap D. van Buul.
Institutions: Sanquin Research and Landsteiner Laboratory, AMC at University of Amsterdam.
During inflammation, leukocytes leave the circulation and cross the endothelium to fight invading pathogens in underlying tissues. This process is known as leukocyte transendothelial migration. Two routes for leukocytes to cross the endothelial monolayer have been described: the paracellular route, i.e., through the cell-cell junctions and the transcellular route, i.e., through the endothelial cell body. However, it has been technically difficult to discriminate between the para- and transcellular route. We developed a simple in vitro assay to study the distribution of endogenous VE-cadherin and PECAM-1 during neutrophil transendothelial migration under physiological flow conditions. Prior to neutrophil perfusion, endothelial cells were briefly treated with fluorescently-labeled antibodies against VE-cadherin and PECAM-1. These antibodies did not interfere with the function of both proteins, as was determined by electrical cell-substrate impedance sensing and FRAP measurements. Using this assay, we were able to follow the distribution of endogenous VE-cadherin and PECAM-1 during transendothelial migration under flow conditions and discriminate between the para- and transcellular migration routes of the leukocytes across the endothelium.
Immunology, Issue 90, Leukocytes, Human Umbilical Vein Endothelial Cells (HUVECs), transmigration, VE-cadherin, PECAM-1, endothelium, transcellular, paracellular
51766
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In Vivo Modeling of the Morbid Human Genome using Danio rerio
Authors: Adrienne R. Niederriter, Erica E. Davis, Christelle Golzio, Edwin C. Oh, I-Chun Tsai, Nicholas Katsanis.
Institutions: Duke University Medical Center, Duke University, Duke University Medical Center.
Here, we present methods for the development of assays to query potentially clinically significant nonsynonymous changes using in vivo complementation in zebrafish. Zebrafish (Danio rerio) are a useful animal system due to their experimental tractability; embryos are transparent to enable facile viewing, undergo rapid development ex vivo, and can be genetically manipulated.1 These aspects have allowed for significant advances in the analysis of embryogenesis, molecular processes, and morphogenetic signaling. Taken together, the advantages of this vertebrate model make zebrafish highly amenable to modeling the developmental defects in pediatric disease, and in some cases, adult-onset disorders. Because the zebrafish genome is highly conserved with that of humans (~70% orthologous), it is possible to recapitulate human disease states in zebrafish. This is accomplished either through the injection of mutant human mRNA to induce dominant negative or gain of function alleles, or utilization of morpholino (MO) antisense oligonucleotides to suppress genes to mimic loss of function variants. Through complementation of MO-induced phenotypes with capped human mRNA, our approach enables the interpretation of the deleterious effect of mutations on human protein sequence based on the ability of mutant mRNA to rescue a measurable, physiologically relevant phenotype. Modeling of the human disease alleles occurs through microinjection of zebrafish embryos with MO and/or human mRNA at the 1-4 cell stage, and phenotyping up to seven days post fertilization (dpf). This general strategy can be extended to a wide range of disease phenotypes, as demonstrated in the following protocol. We present our established models for morphogenetic signaling, craniofacial, cardiac, vascular integrity, renal function, and skeletal muscle disorder phenotypes, as well as others.
Molecular Biology, Issue 78, Genetics, Biomedical Engineering, Medicine, Developmental Biology, Biochemistry, Anatomy, Physiology, Bioengineering, Genomics, Medical, zebrafish, in vivo, morpholino, human disease modeling, transcription, PCR, mRNA, DNA, Danio rerio, animal model
50338
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Analysis of Oxidative Stress in Zebrafish Embryos
Authors: Vera Mugoni, Annalisa Camporeale, Massimo M. Santoro.
Institutions: University of Torino, Vesalius Research Center, VIB.
High levels of reactive oxygen species (ROS) may cause a change of cellular redox state towards oxidative stress condition. This situation causes oxidation of molecules (lipid, DNA, protein) and leads to cell death. Oxidative stress also impacts the progression of several pathological conditions such as diabetes, retinopathies, neurodegeneration, and cancer. Thus, it is important to define tools to investigate oxidative stress conditions not only at the level of single cells but also in the context of whole organisms. Here, we consider the zebrafish embryo as a useful in vivo system to perform such studies and present a protocol to measure in vivo oxidative stress. Taking advantage of fluorescent ROS probes and zebrafish transgenic fluorescent lines, we develop two different methods to measure oxidative stress in vivo: i) a “whole embryo ROS-detection method” for qualitative measurement of oxidative stress and ii) a “single-cell ROS detection method” for quantitative measurements of oxidative stress. Herein, we demonstrate the efficacy of these procedures by increasing oxidative stress in tissues by oxidant agents and physiological or genetic methods. This protocol is amenable for forward genetic screens and it will help address cause-effect relationships of ROS in animal models of oxidative stress-related pathologies such as neurological disorders and cancer.
Developmental Biology, Issue 89, Danio rerio, zebrafish embryos, endothelial cells, redox state analysis, oxidative stress detection, in vivo ROS measurements, FACS (fluorescence activated cell sorter), molecular probes
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Setting-up an In Vitro Model of Rat Blood-brain Barrier (BBB): A Focus on BBB Impermeability and Receptor-mediated Transport
Authors: Yves Molino, Françoise Jabès, Emmanuelle Lacassagne, Nicolas Gaudin, Michel Khrestchatisky.
Institutions: VECT-HORUS SAS, CNRS, NICN UMR 7259.
The blood brain barrier (BBB) specifically regulates molecular and cellular flux between the blood and the nervous tissue. Our aim was to develop and characterize a highly reproducible rat syngeneic in vitro model of the BBB using co-cultures of primary rat brain endothelial cells (RBEC) and astrocytes to study receptors involved in transcytosis across the endothelial cell monolayer. Astrocytes were isolated by mechanical dissection following trypsin digestion and were frozen for later co-culture. RBEC were isolated from 5-week-old rat cortices. The brains were cleaned of meninges and white matter, and mechanically dissociated following enzymatic digestion. Thereafter, the tissue homogenate was centrifuged in bovine serum albumin to separate vessel fragments from nervous tissue. The vessel fragments underwent a second enzymatic digestion to free endothelial cells from their extracellular matrix. The remaining contaminating cells such as pericytes were further eliminated by plating the microvessel fragments in puromycin-containing medium. They were then passaged onto filters for co-culture with astrocytes grown on the bottom of the wells. RBEC expressed high levels of tight junction (TJ) proteins such as occludin, claudin-5 and ZO-1 with a typical localization at the cell borders. The transendothelial electrical resistance (TEER) of brain endothelial monolayers, indicating the tightness of TJs reached 300 ohm·cm2 on average. The endothelial permeability coefficients (Pe) for lucifer yellow (LY) was highly reproducible with an average of 0.26 ± 0.11 x 10-3 cm/min. Brain endothelial cells organized in monolayers expressed the efflux transporter P-glycoprotein (P-gp), showed a polarized transport of rhodamine 123, a ligand for P-gp, and showed specific transport of transferrin-Cy3 and DiILDL across the endothelial cell monolayer. In conclusion, we provide a protocol for setting up an in vitro BBB model that is highly reproducible due to the quality assurance methods, and that is suitable for research on BBB transporters and receptors.
Medicine, Issue 88, rat brain endothelial cells (RBEC), mouse, spinal cord, tight junction (TJ), receptor-mediated transport (RMT), low density lipoprotein (LDL), LDLR, transferrin, TfR, P-glycoprotein (P-gp), transendothelial electrical resistance (TEER),
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Mechanical Stimulation-induced Calcium Wave Propagation in Cell Monolayers: The Example of Bovine Corneal Endothelial Cells
Authors: Catheleyne D'hondt, Bernard Himpens, Geert Bultynck.
Institutions: KU Leuven.
Intercellular communication is essential for the coordination of physiological processes between cells in a variety of organs and tissues, including the brain, liver, retina, cochlea and vasculature. In experimental settings, intercellular Ca2+-waves can be elicited by applying a mechanical stimulus to a single cell. This leads to the release of the intracellular signaling molecules IP3 and Ca2+ that initiate the propagation of the Ca2+-wave concentrically from the mechanically stimulated cell to the neighboring cells. The main molecular pathways that control intercellular Ca2+-wave propagation are provided by gap junction channels through the direct transfer of IP3 and by hemichannels through the release of ATP. Identification and characterization of the properties and regulation of different connexin and pannexin isoforms as gap junction channels and hemichannels are allowed by the quantification of the spread of the intercellular Ca2+-wave, siRNA, and the use of inhibitors of gap junction channels and hemichannels. Here, we describe a method to measure intercellular Ca2+-wave in monolayers of primary corneal endothelial cells loaded with Fluo4-AM in response to a controlled and localized mechanical stimulus provoked by an acute, short-lasting deformation of the cell as a result of touching the cell membrane with a micromanipulator-controlled glass micropipette with a tip diameter of less than 1 μm. We also describe the isolation of primary bovine corneal endothelial cells and its use as model system to assess Cx43-hemichannel activity as the driven force for intercellular Ca2+-waves through the release of ATP. Finally, we discuss the use, advantages, limitations and alternatives of this method in the context of gap junction channel and hemichannel research.
Cellular Biology, Issue 77, Molecular Biology, Medicine, Biomedical Engineering, Biophysics, Immunology, Ophthalmology, Gap Junctions, Connexins, Connexin 43, Calcium Signaling, Ca2+, Cell Communication, Paracrine Communication, Intercellular communication, calcium wave propagation, gap junctions, hemichannels, endothelial cells, cell signaling, cell, isolation, cell culture
50443
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Modeling Astrocytoma Pathogenesis In Vitro and In Vivo Using Cortical Astrocytes or Neural Stem Cells from Conditional, Genetically Engineered Mice
Authors: Robert S. McNeill, Ralf S. Schmid, Ryan E. Bash, Mark Vitucci, Kristen K. White, Andrea M. Werneke, Brian H. Constance, Byron Huff, C. Ryan Miller.
Institutions: University of North Carolina School of Medicine, University of North Carolina School of Medicine, University of North Carolina School of Medicine, University of North Carolina School of Medicine, University of North Carolina School of Medicine, Emory University School of Medicine, University of North Carolina School of Medicine.
Current astrocytoma models are limited in their ability to define the roles of oncogenic mutations in specific brain cell types during disease pathogenesis and their utility for preclinical drug development. In order to design a better model system for these applications, phenotypically wild-type cortical astrocytes and neural stem cells (NSC) from conditional, genetically engineered mice (GEM) that harbor various combinations of floxed oncogenic alleles were harvested and grown in culture. Genetic recombination was induced in vitro using adenoviral Cre-mediated recombination, resulting in expression of mutated oncogenes and deletion of tumor suppressor genes. The phenotypic consequences of these mutations were defined by measuring proliferation, transformation, and drug response in vitro. Orthotopic allograft models, whereby transformed cells are stereotactically injected into the brains of immune-competent, syngeneic littermates, were developed to define the role of oncogenic mutations and cell type on tumorigenesis in vivo. Unlike most established human glioblastoma cell line xenografts, injection of transformed GEM-derived cortical astrocytes into the brains of immune-competent littermates produced astrocytomas, including the most aggressive subtype, glioblastoma, that recapitulated the histopathological hallmarks of human astrocytomas, including diffuse invasion of normal brain parenchyma. Bioluminescence imaging of orthotopic allografts from transformed astrocytes engineered to express luciferase was utilized to monitor in vivo tumor growth over time. Thus, astrocytoma models using astrocytes and NSC harvested from GEM with conditional oncogenic alleles provide an integrated system to study the genetics and cell biology of astrocytoma pathogenesis in vitro and in vivo and may be useful in preclinical drug development for these devastating diseases.
Neuroscience, Issue 90, astrocytoma, cortical astrocytes, genetically engineered mice, glioblastoma, neural stem cells, orthotopic allograft
51763
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Visualizing Neuroblast Cytokinesis During C. elegans Embryogenesis
Authors: Denise Wernike, Chloe van Oostende, Alisa Piekny.
Institutions: Concordia University.
This protocol describes the use of fluorescence microscopy to image dividing cells within developing Caenorhabditis elegans embryos. In particular, this protocol focuses on how to image dividing neuroblasts, which are found underneath the epidermal cells and may be important for epidermal morphogenesis. Tissue formation is crucial for metazoan development and relies on external cues from neighboring tissues. C. elegans is an excellent model organism to study tissue morphogenesis in vivo due to its transparency and simple organization, making its tissues easy to study via microscopy. Ventral enclosure is the process where the ventral surface of the embryo is covered by a single layer of epithelial cells. This event is thought to be facilitated by the underlying neuroblasts, which provide chemical guidance cues to mediate migration of the overlying epithelial cells. However, the neuroblasts are highly proliferative and also may act as a mechanical substrate for the ventral epidermal cells. Studies using this experimental protocol could uncover the importance of intercellular communication during tissue formation, and could be used to reveal the roles of genes involved in cell division within developing tissues.
Neuroscience, Issue 85, C. elegans, morphogenesis, cytokinesis, neuroblasts, anillin, microscopy, cell division
51188
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Analysis of Cell Migration within a Three-dimensional Collagen Matrix
Authors: Nadine Rommerswinkel, Bernd Niggemann, Silvia Keil, Kurt S. Zänker, Thomas Dittmar.
Institutions: Witten/Herdecke University.
The ability to migrate is a hallmark of various cell types and plays a crucial role in several physiological processes, including embryonic development, wound healing, and immune responses. However, cell migration is also a key mechanism in cancer enabling these cancer cells to detach from the primary tumor to start metastatic spreading. Within the past years various cell migration assays have been developed to analyze the migratory behavior of different cell types. Because the locomotory behavior of cells markedly differs between a two-dimensional (2D) and three-dimensional (3D) environment it can be assumed that the analysis of the migration of cells that are embedded within a 3D environment would yield in more significant cell migration data. The advantage of the described 3D collagen matrix migration assay is that cells are embedded within a physiological 3D network of collagen fibers representing the major component of the extracellular matrix. Due to time-lapse video microscopy real cell migration is measured allowing the determination of several migration parameters as well as their alterations in response to pro-migratory factors or inhibitors. Various cell types could be analyzed using this technique, including lymphocytes/leukocytes, stem cells, and tumor cells. Likewise, also cell clusters or spheroids could be embedded within the collagen matrix concomitant with analysis of the emigration of single cells from the cell cluster/ spheroid into the collagen lattice. We conclude that the 3D collagen matrix migration assay is a versatile method to analyze the migration of cells within a physiological-like 3D environment.
Bioengineering, Issue 92, cell migration, 3D collagen matrix, cell tracking
51963
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Analysis of Tubular Membrane Networks in Cardiac Myocytes from Atria and Ventricles
Authors: Eva Wagner, Sören Brandenburg, Tobias Kohl, Stephan E. Lehnart.
Institutions: Heart Research Center Goettingen, University Medical Center Goettingen, German Center for Cardiovascular Research (DZHK) partner site Goettingen, University of Maryland School of Medicine.
In cardiac myocytes a complex network of membrane tubules - the transverse-axial tubule system (TATS) - controls deep intracellular signaling functions. While the outer surface membrane and associated TATS membrane components appear to be continuous, there are substantial differences in lipid and protein content. In ventricular myocytes (VMs), certain TATS components are highly abundant contributing to rectilinear tubule networks and regular branching 3D architectures. It is thought that peripheral TATS components propagate action potentials from the cell surface to thousands of remote intracellular sarcoendoplasmic reticulum (SER) membrane contact domains, thereby activating intracellular Ca2+ release units (CRUs). In contrast to VMs, the organization and functional role of TATS membranes in atrial myocytes (AMs) is significantly different and much less understood. Taken together, quantitative structural characterization of TATS membrane networks in healthy and diseased myocytes is an essential prerequisite towards better understanding of functional plasticity and pathophysiological reorganization. Here, we present a strategic combination of protocols for direct quantitative analysis of TATS membrane networks in living VMs and AMs. For this, we accompany primary cell isolations of mouse VMs and/or AMs with critical quality control steps and direct membrane staining protocols for fluorescence imaging of TATS membranes. Using an optimized workflow for confocal or superresolution TATS image processing, binarized and skeletonized data are generated for quantitative analysis of the TATS network and its components. Unlike previously published indirect regional aggregate image analysis strategies, our protocols enable direct characterization of specific components and derive complex physiological properties of TATS membrane networks in living myocytes with high throughput and open access software tools. In summary, the combined protocol strategy can be readily applied for quantitative TATS network studies during physiological myocyte adaptation or disease changes, comparison of different cardiac or skeletal muscle cell types, phenotyping of transgenic models, and pharmacological or therapeutic interventions.
Bioengineering, Issue 92, cardiac myocyte, atria, ventricle, heart, primary cell isolation, fluorescence microscopy, membrane tubule, transverse-axial tubule system, image analysis, image processing, T-tubule, collagenase
51823
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A Matrigel-Based Tube Formation Assay to Assess the Vasculogenic Activity of Tumor Cells
Authors: Ralph A. Francescone III, Michael Faibish, Rong Shao.
Institutions: University of Massachusetts, University of Massachusetts, University of Massachusetts.
Over the past several decades, a tube formation assay using growth factor-reduced Matrigel has been typically employed to demonstrate the angiogenic activity of vascular endothelial cells in vitro1-5. However, recently growing evidence has shown that this assay is not limited to test vascular behavior for endothelial cells. Instead, it also has been used to test the ability of a number of tumor cells to develop a vascular phenotype6-8. This capability was consistent with their vasculogenic behavior identified in xenotransplanted animals, a process known as vasculogenic mimicry (VM)9. There is a multitude of evidence demonstrating that tumor cell-mediated VM plays a vital role in the tumor development, independent of endothelial cell angiogenesis6, 10-13. For example, tumor cells were found to participate in the blood perfused, vascular channel formation in tissue samples from melanoma and glioblastoma patients8, 10, 11. Here, we described this tubular network assay as a useful tool in evaluation of vasculogenic activity of tumor cells. We found that some tumor cell lines such as melanoma B16F1 cells, glioblastoma U87 cells, and breast cancer MDA-MB-435 cells are able to form vascular tubules; but some do not such as colon cancer HCT116 cells. Furthermore, this vascular phenotype is dependent on cell numbers plated on the Matrigel. Therefore, this assay may serve as powerful utility to screen the vascular potential of a variety of cell types including vascular cells, tumor cells as well as other cells.
Cancer Biology, Issue 55, tumor, vascular, endothelial, tube formation, Matrigel, in vitro
3040
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Isolation of Microvascular Endothelial Tubes from Mouse Resistance Arteries
Authors: Matthew J. Socha, Steven S. Segal.
Institutions: University of Missouri, Dalton Cardiovascular Research Center.
The control of blood flow by the resistance vasculature regulates the supply of oxygen and nutrients concomitant with the removal of metabolic by-products, as exemplified by exercising skeletal muscle. Endothelial cells (ECs) line the intima of all resistance vessels and serve a key role in controlling diameter (e.g. endothelium-dependent vasodilation) and, thereby, the magnitude and distribution of tissue blood flow. The regulation of vascular resistance by ECs is effected by intracellular Ca2+ signaling, which leads to production of diffusible autacoids (e.g. nitric oxide and arachidonic acid metabolites)1-3 and hyperpolarization4,5 that elicit smooth muscle cell relaxation. Thus understanding the dynamics of endothelial Ca2+ signaling is a key step towards understanding mechanisms governing blood flow control. Isolating endothelial tubes eliminates confounding variables associated with blood in the vessel lumen and with surrounding smooth muscle cells and perivascular nerves, which otherwise influence EC structure and function. Here we present the isolation of endothelial tubes from the superior epigastric artery (SEA) using a protocol optimized for this vessel. To isolate endothelial tubes from an anesthetized mouse, the SEA is ligated in situ to maintain blood within the vessel lumen (to facilitate visualizing it during dissection), and the entire sheet of abdominal muscle is excised. The SEA is dissected free from surrounding skeletal muscle fibers and connective tissue, blood is flushed from the lumen, and mild enzymatic digestion is performed to enable removal of adventitia, nerves and smooth muscle cells using gentle trituration. These freshly-isolated preparations of intact endothelium retain their native morphology, with individual ECs remaining functionally coupled to one another, able to transfer chemical and electrical signals intercellularly through gap junctions6,7. In addition to providing new insight into calcium signaling and membrane biophysics, these preparations enable molecular studies of gene expression and protein localization within native microvascular endothelium.
Basic Protocol, Issue 81, endothelial tubes, microcirculation, calcium signaling, resistance vasculature, Confocal microscopy
50759
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Polarized Translocation of Fluorescent Proteins in Xenopus Ectoderm in Response to Wnt Signaling
Authors: Keiji Itoh, Sergei Y. Sokol.
Institutions: Mount Sinai School of Medicine .
Cell polarity is a fundamental property of eukaryotic cells that is dynamically regulated by both intrinsic and extrinsic factors during embryonic development 1, 2. One of the signaling pathways involved in this regulation is the Wnt pathway, which is used many times during embryogenesis and critical for human disease3, 4, 5. Multiple molecular components of this pathway coordinately regulate signaling in a spatially-restricted manner, but the underlying mechanisms are not fully understood. Xenopus embryonic epithelial cells is an excellent system to study subcellular localization of various signaling proteins. Fluorescent fusion proteins are expressed in Xenopus embryos by RNA microinjection, ectodermal explants are prepared and protein localization is evaluated by epifluorescence. In this experimental protocol we describe how subcellular localization of Diversin, a cytoplasmic protein that has been implicated in signaling and cell polarity determination6, 7 is visualized in Xenopus ectodermal cells to study Wnt signal transduction8. Coexpression of a Wnt ligand or a Frizzled receptor alters the distribution of Diversin fused with red fluorescent protein, RFP, and recruits it to the cell membrane in a polarized fashion 8, 9. This ex vivo protocol should be a useful addition to in vitro studies of cultured mammalian cells, in which spatial control of signaling differs from that of the intact tissue and is much more difficult to analyze.
Developmental Biology, Issue 51, Xenopus embryo, ectoderm, Diversin, Frizzled, membrane recruitment, polarity, Wnt
2700
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