We thank Brianna Alexander, Caolan O&#39;Donnell and Michael Warkala for careful reading and editing of this manuscript. This work was supported by the funding from the National Heart, Lung and Blood Institute of the NIH R01 HL103920, R01 HL134935, R21 OD025323-01 to SA; AJR is supported by NHLBI HL103920-08S1 and the National Institute of Arthritis and Musculoskeletal and Skin Diseases Training grant T32052283-11.

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The authors have nothing to disclose.

The ability to visualize the endothelium in mouse embryos in 3D has provided new insights into their development3. Here we present a protocol that allows for high-resolution 3D imaging of embryos, visualization of vascular connectivity, and quantitative analyses of PAA formation. This protocol can be employed to see how genetic alterations or environmental insults impact PAA development. The procedure reported here uses antibodies against VEGFR2 and ERG to visualize PAA formation and quantify EC n...

During mouse embryogenesis, pharyngeal arch arteries (PAAs) arise as symmetrical, bi-lateral pairs of arteries that connect the heart with the dorsal aortae1. As the embryo develops, the first and second pairs of PAAs regress, while the 3rd, 4th, and 6th PAAs undergo a series of asymmetrical remodeling events to form the aortic arch arteries2.
The PAAs 3, 4 and 6 develop via vasculogenesis, which is the de novo formation of blood vessels3. Defects in the formation or remodeling of these arch arteries give rise to various congenital heart defects, such as those seen in patients with DiGeorge Syndrome4,5. Therefore, understanding mechanisms that regulate the development of PAAs can lead to a better understanding of congenital heart disease (CHD) etiology.
Current approaches for visualizing and analyzing PAA development include immunofluorescence of tissue sections, vascular casts, India ink injection, high resolution episcopic microscopy, and/or whole-mount immunohistochemistry1,4,5,6,7. Herein, we describe a protocol combining whole-mount immunofluorescence, confocal microscopy and 3D image rendering in order to gather, analyze, and quantify volumetric data, vascular connectivity and cell identity. Further, we detail a method to compartmentalize and quantify the numbers of ECs in each pharyngeal arch as a means to study formation of the pharyngeal arch vascular plexus and its remodeling into the PAAs. While this protocol is designed for analyzing PAA development, it can be used to analyze other developing vascular networks.

<table><tbody><tr><td>10x PBS</td><td>MP Biomedicals</td><td>PBS10X02</td><td></td></tr><tr><td>20x water immersion objective</td><td>Nikon</td><td>MRD77200</td><td></td></tr><tr><td>Agarose</td><td>Bio-Rad Laboratories</td><td>1613101</td><td></td></tr><tr><td>Alexa Fluor 488 anti-goat</td><td>Invitrogen</td><td>A-11055</td><td></td></tr><tr><td>Alexa Fluor 555 anti-mouse</td><td>Invitrogen</td><td>A-31570</td><td></td></tr><tr><td>Analysis Software</td><td>Imaris 9.2.0</td><td></td><td></td></tr><tr><td>Benzyl Alcohol</td><td>Sigma-Aldrich</td><td>305197</td><td></td></tr><tr><td>Benzyl Benzoate</td><td>Sigma-Aldrich</td><td>8.18701.0100</td><td></td></tr><tr><td>Cover Slips</td><td>VWR</td><td>16004-312</td><td></td></tr><tr><td>DAPI (5 mg/mL stock)</td><td>Fisher Scientific</td><td>D3571</td><td></td></tr><tr><td>Eppendorf Tubes (2.0 mL)</td><td>Fisher Scientific</td><td>05-408-138</td><td></td></tr><tr><td>Ethanol</td><td>VWR</td><td>89370-084</td><td></td></tr><tr><td>Falcon tubes (50 mL)</td><td>Corning</td><td>352098</td><td></td></tr><tr><td>Fast wells</td><td>Grace Bio Labs</td><td>664113</td><td></td></tr><tr><td>Forceps</td><td>Roboz</td><td>RS-5015</td><td></td></tr><tr><td>Goat anti-VEGFR2</td><td>R&amp;amp;D Systems, Inc.</td><td>AF644</td><td></td></tr><tr><td>Methanol</td><td>VWR</td><td>BDH1135-4LP</td><td></td></tr><tr><td>Microscope</td><td>Nikon</td><td>A1HD25</td><td></td></tr><tr><td>Mouse anti-ERG</td><td>Abcam</td><td>ab214341</td><td></td></tr><tr><td>Normal Donkey Serum</td><td>Sigma-Aldrich</td><td>D9663</td><td></td></tr><tr><td>Paraformaldehyde</td><td>Electron Microscopy Sciences</td><td>15710</td><td></td></tr><tr><td>Pasteur pipets</td><td>Fisher Scientific</td><td>13-678-20D</td><td></td></tr><tr><td>Petri dishes (35 mm)</td><td>Genesee Scientific</td><td>32-103</td><td></td></tr><tr><td>Petri dishes (60 mm)</td><td>Genesee Scientific</td><td>32-105</td><td></td></tr><tr><td>Plastic Molds</td><td>VWR</td><td>18000-128</td><td></td></tr><tr><td>Scapels</td><td>Exelint International Co.</td><td>29552</td><td></td></tr><tr><td>Triton-X-100</td><td>Fisher Scientific</td><td>BP 151-500</td><td></td></tr></tbody></table>

visualization and analysis of pharyngeal arch arteries using whole-mount immunohistochemistry and 3d reconstruction

Improper formation or remodeling of the pharyngeal arch arteries (PAAs) 3, 4, and 6 contribute to some of the most severe forms of congenital heart disease. To study the formation of PAAs, we developed a protocol using whole-mount immunofluorescence coupled with benzyl alcohol/benzyl benzoate (BABB) tissue clearing, and confocal microscopy. This allows for the visualization of the pharyngeal arch endothelium at a fine cellular resolution as well as the 3D connectivity of the vasculature. Using software, we have established a protocol to quantify the number of endothelial cells (ECs) in PAAs, as well as the number of ECs within the vascular plexus surrounding the PAAs within pharyngeal arches 3, 4, and 6. When applied to the whole embryo, this methodology provides a comprehensive visualization and quantitative analysis of embryonic vasculature.

The whole-mount immunofluorescence protocol presented here produces clear and clean results, allowing for the 3D reconstruction of pharyngeal arch endothelium, as seen in Figure 1A. It is important to incubate embryos for a sufficient amount of time in each antibody solution to ensure complete penetration through the sample, as well as, thoroughly washing embryos post antibody incubation. In Figure 1B</st...

Watch this Scientific Journal Video about Visualization and Analysis of Pharyngeal Arch Arteries using Whole-mount Immunohistochemistry and 3D Reconstruction at JoVE.com

Visualization and Analysis of Pharyngeal Arch Arteries using Whole-mount Immunohistochemistry and 3D Reconstruction

Here, we describe a protocol to visualize and analyze the pharyngeal arch arteries 3, 4, and 6 of mouse embryos using whole-mount immunofluorescence, tissue clearing, confocal microscopy, and 3D reconstruction.

Improper formation or remodeling of the pharyngeal arch arteries (PAAs) 3, 4, and 6 contribute to some of the most severe forms of congenital heart ...

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Research

JoVE Journal

Developmental Biology

9.5K Views.  Rutgers Biomedical and Health Sciences. Met deze methode kan elke faryngeale boog worden gecompartimenteerd. Endotheelcelnummers kunnen dan in elke boog worden gekwantificeerd als een middel om de ontwikkeling van de faryngeale boogslagader te bestuderen. De belangrijkste voordelen van deze aanpak zijn het vermogen om de relatie tussen verschillende vasculaire structuren te visualiseren en het vermogen om kwantitatief te bepalen hoe de structuren de mutanten beïnvloedden.Aorta boog slagaders worden vaak gemuteerd in aangebo...

Video: Visualization and Analysis of Pharyngeal Arch Arteries using Whole-mount Immunohistochemistry and 3D Reconstruction

Ex Vivo Culture of Pharyngeal Arches to Study Heart and Muscle Progenitors and Their Niche

The pharyngeal mesoderm of developing embryos contributes to broad regions of head and heart musculature. We have developed a novel method to study head and heart progenitor cell development with pharyngeal arches (also known as branchial arches) ex vivo. Using this method, we have recently described that the second pharyngeal arch contains self-renewing heart progenitors and serves as a microenvironment for expansion of the progenitors during mouse heart development. The progenitor cells remain undifferentiated and expansive inside the arch, but quickly become functional cardiomyocytes as they migrate out of the arch. We also reported that first pharyngeal arch contains muscle progenitors giving rise to myotubes after leaving the arch. Here, we demonstrate the procedure for the dissection and ex vivo culture of first and second pharyngeal arches from developing mouse embryos. The method enables one to study head and heart progenitor/muscle development, including cardiomyocyte and myotube formation in detail ex vivo.

Ex Vivo Culture of Pharyngeal Arches to Study Heart and Muscle Progenitors and Their Niche

Here, we present a protocol to culture pharyngeal arches to study the biology of heart and muscle progenitor cells and their microenvironment.

The pharyngeal mesoderm of developing embryos contributes to broad regions of head and heart musculature. We have developed a novel method to study head ...

Analysis of Coronary Vessels in Cleared Embryonic Hearts

Whole mount visualization of the embryonic coronary plexus from which the capillary and arterial networks will form is rendered problematic using standard microscopy techniques, due to the scattering of imaging light by the thick heart tissue, as these vessels are localized deep within the walls of the developing heart. As optical clearing of tissues using organic solvents such as BABB (1 part benzyl alcohol to 2 parts benzyl benzoate) has been shown to greatly improve the optical penetration depth that can be achieved, we combined clearance of whole, PECAM1-immunostained hearts, with laser-scanning confocal microscopy, in order to obtain high-resolution images of vessels throughout the entire heart. BABB clearance of embryonic hearts takes place rapidly and also acts to preserve the fluorescent signal for several weeks; in addition, samples can be imaged multiple times without loss of signal. This straightforward method is also applicable to imaging other types of blood vessels in whole embryos.

We present a protocol for the analysis of coronary vessels in whole embryonic murine hearts up to E15.5, using standard immunological staining methods followed by optical clearance and confocal microscopy. This technique enables visualization of blood vessels throughout the entire heart without the need for time-consuming analysis of serial sections.

Whole mount visualization of the embryonic coronary plexus from which the capillary and arterial networks will form is rendered problematic using standard ...

Generation and 3-Dimensional Quantitation of Arterial Lesions in Mice Using Optical Projection Tomography

The generation and analysis of vascular lesions in appropriate animal models is a cornerstone of research into cardiovascular disease, generating important information on the pathogenesis of lesion formation and the action of novel therapies. Use of atherosclerosis-prone mice, surgical methods of lesion induction, and dietary modification has dramatically improved understanding of the mechanisms that contribute to disease development and the potential of new treatments.
Classically, analysis of lesions is performed ex vivo using 2-dimensional histological techniques. This article describes application of optical projection tomography (OPT) to 3-dimensional quantitation of arterial lesions. As this technique is non-destructive, it can be used as an adjunct to standard histological and immunohistochemical analyses.
Neointimal lesions were induced by wire-insertion or ligation of the mouse femoral artery whilst atherosclerotic lesions were generated by administration of an atherogenic diet to apoE-deficient mice.
Lesions were examined using OPT imaging of autofluorescent emission followed by complementary histological and immunohistochemical analysis. OPT clearly distinguished lesions from the underlying vascular wall. Lesion size was calculated in 2-dimensional sections using planimetry, enabling calculation of lesion volume and maximal cross-sectional area. Data generated using OPT were consistent with measurements obtained using histology, confirming the accuracy of the technique and its potential as a complement (rather than alternative) to traditional methods of analysis.
This work demonstrates the potential of OPT for imaging atherosclerotic and neointimal lesions. It provides a rapid, much needed ex vivo technique for the routine 3-dimensional quantification of vascular remodelling.

Ex vivo analysis of arterial lesions from animal models of cardiovascular disease classically relies on histological and immunohistochemical techniques. These provide 2-dimensional measurements in 3-dimensional lesions. This manuscript describes the generation of arterial lesions for quantitative analysis in 3-dimensions using optical projection tomography.

The generation and analysis of vascular lesions in appropriate animal models is a cornerstone of research into cardiovascular disease, generating ...

Medicine

Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation

Somitogenesis is a hallmark of vertebrate embryonic development. For years, researchers have been studying this process in a variety of organisms using a wide range of techniques encompassing ex vivo and in vitro approaches. However, most studies still rely on the analysis of two-dimensional (2D) imaging data, which limits proper evaluation of a developmental process like axial extension and somitogenesis involving highly dynamic interactions in a complex 3D space. Here we describe techniques that allow mouse live imaging acquisition, dataset processing, visualization and analysis in 3D and 4D to study the cells (e.g., neuromesodermal progenitors) involved in these developmental processes. We also provide a step-by-step protocol for optical projection tomography and whole-mount immunofluorescence microscopy in mouse embryos (from sample preparation to image acquisition) and show a pipeline that we developed to process and visualize 3D image data. We extend the use of some of these techniques and highlight specific features of different available software (e.g., Fiji/ImageJ, Drishti, Amira and Imaris) that can be used to improve our current understanding of axial extension and somite formation (e.g., 3D reconstructions). Altogether, the techniques here described emphasize the importance of 3D data visualization and analysis in developmental biology, and might help other researchers to better address 3D and 4D image data in the context of vertebrate axial extension and segmentation. Finally, the work also employs novel tools to facilitate teaching vertebrate embryonic development.

Here, we describe computational tools and methods that allow visualization and analysis of three and four-dimensional image data of mouse embryos in the context of axial elongation and segmentation, obtained by in toto optical projection tomography, and by live imaging and whole-mount immunofluorescence staining using multiphoton microscopy.

Somitogenesis is a hallmark of vertebrate embryonic development. For years, researchers have been studying this process in a variety of organisms using a ...

Quantification of Atherosclerosis in Mice

Cardiovascular disease is the main cause of death in the world. The underlying cause in most cases is atherosclerosis, which is in part a chronic inflammatory disease. Experimental atherosclerosis studies have elucidated the role of cholesterol and inflammation in the disease process. This has led to successful clinical trials with pharmaceutical agents that reduce clinical manifestations of atherosclerosis. Careful and well-controlled experiments in mouse models of the disease could further elucidate the pathogenesis of the disease, which is not fully understood. Standardized lesion analysis is important to reduce experimental variability and increase reproducibility. Determining lesion size in aortic root, aortic arch, and brachiocephalic artery are common endpoints in experimental atherosclerosis. This protocol provides a technical description for evaluation of atherosclerosis at all these sites in a single mouse. The protocol is particularly useful when material is limited, as is frequently the case when genetically modified animals are being characterized.

Murine models of atherosclerosis are useful tools to investigate pathogenic pathways on a molecular level, but require standardized quantification of lesion development. This protocol describes an optimized method to determine lesion size in the major arterial vessels including the aortic root, aortic arch, and brachiocephalic artery.

Cardiovascular disease is the main cause of death in the world. The underlying cause in most cases is atherosclerosis, which is in part a chronic ...

Immunology and Infection

Imaging and 3D Reconstruction of Cerebrovascular Structures in Embryonic Zebrafish

Zebrafish are a powerful tool to study developmental biology and pathology in vivo. The small size and relative transparency of zebrafish embryos make them particularly useful for the visual examination of processes such as heart and vascular development. In several recent studies transgenic zebrafish that express EGFP in vascular endothelial cells were used to image and analyze complex vascular networks in the brain and retina, using confocal microscopy. Descriptions are provided to prepare, treat and image zebrafish embryos that express enhanced green fluorescent protein (EGFP), and then generate comprehensive 3D renderings of the cerebrovascular system. Protocols include the treatment of embryos, confocal imaging, and fixation protocols that preserve EGFP fluorescence. Further, useful tips on obtaining high-quality images of cerebrovascular structures, such as removal the eye without damaging nearby neural tissue are provided. Potential pitfalls with confocal imaging are discussed, along with the steps necessary to generate 3D reconstructions from confocal image stacks using freely available open source software.

Imaging of cerebrovascular development in larval zebrafish is described. Techniques to facilitate 3D imaging and modify cerebrovascular development using chemical treatments are also provided.

Zebrafish are a powerful tool to study developmental biology and pathology in vivo.  The small size and relative transparency of zebrafish embryos make ...

Biology

Whole-Mount Immunofluorescence Staining, Confocal Imaging and 3D Reconstruction of the Sinoatrial and Atrioventricular Node in the Mouse

The electrical signal physiologically generated by pacemaker cells in the sinoatrial node (SAN) is conducted through the conduction system, which includes the atrioventricular node (AVN), to allow excitation and contraction of the whole heart. Any dysfunction of either SAN or AVN results in arrhythmias, indicating their fundamental role in electrophysiology and arrhythmogenesis. Mouse models are widely used in arrhythmia research, but the specific investigation of SAN and AVN remains challenging.
The SAN is located at the junction of the crista terminalis with the superior vena cava and AVN is located at the apex of the triangle of Koch, formed by the orifice of the coronary sinus, the tricuspid annulus, and the tendon of Todaro. However, due to the small size, visualization by conventional histology remains challenging and it does not allow the study of SAN and AVN within their 3D environment.
Here we describe a whole-mount immunofluorescence approach that allows the local visualization of labelled mouse SAN and AVN. Whole-mount immunofluorescence staining is intended for smaller sections of tissue without the need for manual sectioning. To this purpose, the mouse heart is dissected, with unwanted tissue removed, followed by fixation, permeabilization and blocking. Cells of the conduction system within SAN and AVN are then stained with an anti-HCN4 antibody. Confocal laser scanning microscopy and image processing allow differentiation between nodal cells and working cardiomyocytes, and to clearly localize SAN and AVN. Furthermore, additional antibodies can be combined to label other cell types as well, such as nerve fibers.
Compared to conventional immunohistology, whole-mount immunofluorescence staining preserves the anatomical integrity of the cardiac conduction system, thus allowing the investigation of AVN; especially so into their anatomy and interactions with the surrounding working myocardium and non-myocyte cells.

We provide a step-by-step protocol for whole-mount immunofluorescence staining of the sinoatrial node (SAN) and atrioventricular node (AVN) in murine hearts.

The electrical signal physiologically generated by pacemaker cells in the sinoatrial node (SAN) is conducted through the conduction system, which includes ...

En Face Preparation of Mouse Blood Vessels

Sections of paraffin embedded tissues are routinely used for studying tissue histology and histopathology. However, it is difficult to determine what the three-dimensional tissue morphology is from such sections. In addition, the sections of tissues examined may not contain the region within the tissue that is necessary for the purpose of the ongoing study. This latter limitation hinders histopathological studies of blood vessels since vascular lesions develop in a focalized manner. This requires a method that enables us to survey a wide area of the blood vessel wall, from its surface to deeper regions. A whole mount en face preparation of blood vessels fulfills this requirement. In this article, we will demonstrate how to make en face preparations of the mouse aorta and carotid artery and to immunofluorescently stain them for confocal microscopy and other types of fluorescence-based imaging.

En Face Preparation of Mouse Blood Vessels

A procedure for making en face preparations of the mouse carotid artery and aorta is described. Such preparations, when immunofluorescently stained with specific antibodies, enable us to study localization of proteins and identification of cell types within the entire vascular wall by confocal microscopy.

Sections of paraffin embedded tissues are routinely used for studying tissue histology and histopathology. However, it is difficult to determine what the ...

Isolation and Analysis of Aortic Arch and Root Lesions in an Atherosclerotic Mouse Model

Atherosclerosis, a leading cause of cardiovascular diseases, necessitates a detailed examination of lesion development and progression. This study introduces a comprehensive protocol for the isolation and histological analysis of aortic arch and root lesions in a widely used atherosclerotic mouse model, low-density lipoprotein receptor knock-out (Ldlr-/-) mice. The aortic arch and root are key sites for atherosclerotic lesions, and their examination is critical for assessing the onset, progression, or regression of atherosclerosis, predicting cardiovascular event risks, and identifying potential therapeutic targets. This protocol outlines methods for quantifying atherosclerotic burden in the aortic arch and root, including tissue isolation, fixation, Oil Red O staining, aortic root sectioning, Hematoxylin and Eosin (HE) staining, Verhoeff-Van Gieson (VVG) staining, and image analysis. Oil Red O staining measures plaque area in the aortic arch, evaluating the severity of atherosclerosis, while HE staining of the aortic root reveals plaque components such as the lipid core and fibrous cap, facilitating the assessment of plaque stability and rupture risk. VVG staining can stain collagen fibers within tissues, providing further insights into plaque composition and related information. This thorough analysis offers valuable insights into the mechanisms of lesion development and may guide the creation of novel therapeutic strategies for preventing and treating atherosclerosis.

This protocol provides a comprehensive methodology for the quantitative analysis of atherosclerotic plaques to facilitate more in-depth research into the mechanisms and progression of atherosclerosis.

Atherosclerosis, a leading cause of cardiovascular diseases, necessitates a detailed examination of lesion development and progression. This study ...

Comprehensive 3D Analysis of Human Hearts from Micro to Macro Scales

Pipeline for Multi-Scale Three-Dimensional Anatomic Study of the Human Heart

Detailed study of non-failing human hearts rejected for transplantation provides a unique opportunity to perform structural analyses across microscopic and macroscopic scales. These techniques include tissue clearing (modified immunolabeling-enabled three-dimensional (3D) imaging of solvent-cleared organs) and immunohistochemical staining. Mesoscopic examination procedures include stereoscopic dissection and micro-computed tomographic (CT) scanning. Macroscopic examination procedures include gross dissection, photography (including anaglyphs and photogrammetry), CT, and 3D printing of the physically or virtually dissected or whole heart. Before macroscopic examination, pressure-perfusion fixation may be performed to maintain the 3D architecture and physiologically relevant morphology of the heart. The application of these techniques in combination to study the human heart is unique and crucial in understanding the relationship between distinct anatomic features such as coronary vasculature and myocardial innervation in the context of the 3D architecture of the heart. This protocol describes the methodologies in detail and includes representative results&#160;to illustrate progress in the research of human cardiac anatomy.

Author Spotlight: Advancing Human Cardiac Anatomy Through Multi-Scale Analysis of Hearts

This protocol presents a comprehensive pipeline to analyze samples obtained from human hearts that span the microscopic and macroscopic scales.

Detailed study of non-failing human hearts rejected for transplantation provides a unique opportunity to perform structural analyses across microscopic ...

Visualization and Analysis of Pharyngeal Arch Arteries using Whole-mount Immunohistochemistry and 3D Reconstruction

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