The Aguirre Lab is supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health under award number K01HL135464 and by the American Heart Association under award number 19IPLOI34660342.

<ol>
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E., Kaplan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+incidence+of+congenital+heart+disease.">The incidence of congenital heart disease.</a> Journal of the American College of Cardiology. 39 (12), 1890-1900 (2002).</li><li>Fahed, A. C., Gelb, B. D., Seidman, J. G., Seidman, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetics+of+congenital+heart+disease:+The+glass+half+empty.">Genetics of congenital heart disease: The glass half empty.</a> Circulation Research. 112 (4), 707-720 (2013).</li><li>Pelech, A. N., Broeckel, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+the+etiologies+of+congenital+heart+diseases.">Toward the etiologies of congenital heart diseases.</a> Clinics in Perinatology. 32 (4), 825-844 (2005).</li><li>Zaidi, S., Brueckner, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetics+and+Genomics+of+Congenital+Heart+Disease.">Genetics and Genomics of Congenital Heart Disease.</a> Circulation Research. 120 (6), 923-940 (2017).</li><li>Kenny, L. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transplantation+in+the+single+ventricle+population.">Transplantation in the single ventricle population.</a> Annals of Cardiothoracic Surgery. 7 (1), 152-159 (2018).</li><li>Navaratnam, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exercise-Induced+Systemic+Venous+Hypertension+in+the+Fontan+Circulation.">Exercise-Induced Systemic Venous Hypertension in the Fontan Circulation.</a> The American Journal of Cardiology. 117 (10), 1667-1671 (2016).</li><li>De Leval, M. R., Deanfield, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Four+decades+of+Fontan+palliation.">Four decades of Fontan palliation.</a> Nature Reviews Cardiology. 7 (9), 520-527 (2010).</li><li>Buckberg, G. D., Hoffman, J. I. E., Coghlan, H. C., Nanda, N. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventricular+structure-function+relations+in+health+and+disease:+part+II.+Clinical+considerations.">Ventricular structure-function relations in health and disease: part II. Clinical considerations.</a> European Journal of Cardio-Thoracic Surgery : Official Journal of the European Association for Cardio-thoracic Surgery. 47 (5), 778-787 (2015).</li><li>Jenkins, K. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninherited+risk+factors+and+congenital+cardiovascular+defects:+Current+knowledge+-+A+scientific+statement+from+the+American+Heart+Association+Council+on+Cardiovascular+Disease+in+the+Young.">Noninherited risk factors and congenital cardiovascular defects: Current knowledge - A scientific statement from the American Heart Association Council on Cardiovascular Disease in the Young.</a> Circulation. 115 (23), 2995-3014 (2007).</li><li>Botto, L. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lower+rate+of+selected+congenital+heart+defects+with+better+maternal+diet+quality+:+a+population-based+study.">Lower rate of selected congenital heart defects with better maternal diet quality : a population-based study.</a> Archives of Disease in Childhood - Fetal and Neonatal Edition. 101 (1), F43-F49 (2016).</li><li>Knowles, R. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ethnic+and+socioeconomic+variation+in+incidence+of+congenital+heart+defects.">Ethnic and socioeconomic variation in incidence of congenital heart defects.</a> Archives of Disease in Childhood. 102 (6), 496-502 (2017).</li><li>Feng, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maternal+Folic+Acid+Supplementation+and+the+Risk+of+Congenital+Heart+Defects+in+Offspring+:+A+Meta-Analysis+of+Epidemiological+Observational+Studies.">Maternal Folic Acid Supplementation and the Risk of Congenital Heart Defects in Offspring : A Meta-Analysis of Epidemiological Observational Studies.</a> Scientific Reports. 17 (5), 8506 (2015).</li><li>Rhinn, M., Dolle, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinoic+acid+signalling+during+development.">Retinoic acid signalling during development.</a> Development. 139 (5), 843-858 (2012).</li><li>Liu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Circulating+retinoic+acid+levels+and+the+development+of+metabolic+syndrome.">Circulating retinoic acid levels and the development of metabolic syndrome.</a> The Journal of Clinical Endocrinology &amp; Metabolism. 101 (February), 2015 (2016).</li><li>Kurian, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+novel+long+noncoding+RNAs+underlying+vertebrate+cardiovascular+development.">Identification of novel long noncoding RNAs underlying vertebrate cardiovascular development.</a> Circulation. 131 (14), 1278-1290 (2015).</li><li>Aguirre, A., Sancho-Martinez, I., Izpisua Belmonte, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reprogramming+toward+heart+regeneration:+Stem+cells+and+beyond.">Reprogramming toward heart regeneration: Stem cells and beyond.</a> Cell Stem Cell. 12 (3), 275-284 (2013).</li><li>Srivastava, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Making+or+breaking+the+heart:+from+lineage+determination+to+morphogenesis.">Making or breaking the heart: from lineage determination to morphogenesis.</a> Cell. 126 (6), 1037-1048 (2006).</li><li>Heyne, G. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+and+reliable+method+for+early+pregnancy+detection+in+inbred+mice.">A simple and reliable method for early pregnancy detection in inbred mice.</a> Journal of the American Association for Laboratory Animal Science. 54 (4), 368-371 (2015).</li><li>. Stage Definition Available from: <a target="_blank" href="https://www.emouseatlas.org/emap/ema/theiler_stages/StageDefinition/stagedefinition.html">https://www.emouseatlas.org/emap/ema/theiler_stages/StageDefinition/stagedefinition.html</a> (1998)</li><li>Part 4-Measure Areas using Thresholding. Science Education Resource Center Available from: <a target="_blank" href="https://serc.carleton.edu/eet/measure_sat2/part_4.html">https://serc.carleton.edu/eet/measure_sat2/part_4.html</a> (2017)</li><li>. Examples of Image Analysis Using ImageJ Available from: <a target="_blank" href="https://imagej.nih.gov/ij/docs/pdfs/examples.pdf">https://imagej.nih.gov/ij/docs/pdfs/examples.pdf</a> (2007)</li><li>MacIver, D. H., Adeniran, I., Zhang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Left+ventricular+ejection+fraction+is+determined+by+both+global+myocardial+strain+and+wall+thickness.">Left ventricular ejection fraction is determined by both global myocardial strain and wall thickness.</a> IJC Heart and Vasculature. 1 (7), 113-118 (2015).</li><li>Towbin, J. 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The authors have no disclosures to report.

This protocol explores the techniques involved in the analysis of cardiac development in embryonic hearts. Some limitations of this method are the required physical dexterity for the preparatory techniques, which may require practice, and skill with microscope imaging. If the slices obtained at the cryostat are messy, the hematoxylin and eosin staining will not be clear, or if the images taken at the microscope have poor lighting, then the method used with ImageJ will not work. A limitation of the threshold feature of Im...

CHDs are the most common type of birth defect in humans and are the leading cause of birth defect-related deaths1,2,3,4,5,6. Although about 90% of newborn children survive CHD, it is frequently associated with significant morbidity and medical interventions over the years, imposing a heavy burden on the patients&#39; lives and the healthcare system7,8,9,10. Outside of purely genetic factors, the causes of CHD are poorly understood4. Unidentified causes account for ~56-66% of all CHD cases according to the American Heart Association and other sources2,3,4,11. Well-known factors include genetic mutations, CNVs, de novo single nucleotide variants, and aneuploidy. It is suspected that environmental and dietary factors are also important sources contributing to CHD, as suggested by epidemiological studies linking maternal lifestyle2,12, economic deprivation, and race13, and by research into dietary factors such as folic acid11,14 and the bioactive lipid retinoic acid15,16. Investigating the mechanisms and causes of CHD and other cardiovascular defects is important to develop preventive strategies and novel therapeutic options1,4,17,18,19.
The developing mouse is a cornerstone model for studying CHD in mammals. However, some of the methods and analyses employed, such as dissections preserving heart morphology, analysis of developmental stages, and identification of CHD-associated defects, can be daunting for scientists that are new to the analysis of murine hearts. The goal of the methods described in this protocol is to offer qualitative and quantitative guidelines for these processes. Thus, in this protocol we explain how to perform timed matings to produce embryos of the desired gestational stage, dissect pregnant females for intact heart recovery (including associated tissues such as the outflow tract), heart fixation and preparation for cryostat sectioning, basic histology methods, quantitative analyses of common heart defects, and qualitative analysis of heart muscle compaction, a common precursor phenotype to some types of CHD.

<table><tbody><tr><td>15 mL Conical Tube(s)</td><td>Fisher Scientific</td><td># 1495970C</td><td></td></tr><tr><td>C57BL/6J Mice</td><td>Jackson Labs</td><td>C57BL/6J - stock 000664</td><td></td></tr><tr><td>Coplin Staining Jars (x6)</td><td>VWR Scientific</td><td># 25457-006</td><td></td></tr><tr><td>Coverslips 24X50MM #1.5</td><td>VWR Scientific</td><td># 48393-241</td><td></td></tr><tr><td>Cryostat - Leica CM3050S</td><td>Leica</td><td>N/A</td><td></td></tr><tr><td>Dissecting Dish(s)</td><td>Fisher Scientific</td><td># 50930381</td><td></td></tr><tr><td>Dumont #5 - Fine Forceps (x2)</td><td>Fine Science Tools</td><td># 11254-20</td><td></td></tr><tr><td>Eosin Y Solution</td><td>Millipore Sigma</td><td># HT110116-500ML</td><td></td></tr><tr><td>Ethyl Alcohol (Pure, 200 proof)</td><td>Fisher Scientific</td><td># BP2818-500</td><td></td></tr><tr><td>Ethylenediaminetetraacetic acid (EDTA)</td><td>Millipore Sigma</td><td># E9884-100G</td><td></td></tr><tr><td>Eukitt</td><td>Millipore Sigma</td><td># 03989-100ML</td><td></td></tr><tr><td>Fine Scissors</td><td>Fine Science Tools</td><td># 14060-10</td><td></td></tr><tr><td>Fluorescent Stereo Microscope Leica M165 FC</td><td>Leica</td><td>N/A</td><td></td></tr><tr><td>Glycine</td><td>Millipore Sigma</td><td># 410225-250G</td><td></td></tr><tr><td>Graefe Forceps</td><td>Fine Science Tools</td><td># 11052-10</td><td></td></tr><tr><td>Graphpad Prism 8 Software</td><td>Graphpad</td><td></td><td></td></tr><tr><td>ImageJ Software</td><td>ImageJ</td><td></td><td></td></tr><tr><td>Kimwipes</td><td>Fisher Scientific</td><td># 06666A</td><td></td></tr><tr><td>Mayer&#039;s hematoxylin solution</td><td>Millipore Sigma</td><td># MHS16-500ML</td><td></td></tr><tr><td>Micropipette tip(s) - p200</td><td>Fisher Scientific</td><td># 02707448</td><td></td></tr><tr><td>Microsoft Excel Software</td><td>Microsoft</td><td></td><td></td></tr><tr><td>OCT Compound</td><td>VWR Scientific</td><td># 102094-106</td><td></td></tr><tr><td>Olympus CkX53 Microscope</td><td>Olympus</td><td></td><td></td></tr><tr><td>Paint Brushes (at least 2)</td><td></td><td></td><td></td></tr><tr><td>Paraformaldehyde</td><td>VWR Scientific</td><td># 0215014601</td><td>Make into 4% solution (dissolved in PBS)</td></tr><tr><td>Pasteur pipette(s)</td><td>Fisher Scientific</td><td># 13-711-7M</td><td></td></tr><tr><td>Penicillin-Streptomycin</td><td>ThermoFisher Scientific</td><td># 15140122</td><td></td></tr><tr><td>Phosphate Buffered Saline (PBS)</td><td>ThermoFisher Scientific</td><td># 70011044</td><td>Dilute from 10x to 1x before using</td></tr><tr><td>Scale</td><td>Mettler Toledo</td><td># MS1602TS</td><td></td></tr><tr><td>Scale</td><td>Mettler Toledo</td><td># MS105</td><td></td></tr><tr><td>Scalpel Handle #3</td><td>VWR Scientific</td><td># 10161-918</td><td></td></tr><tr><td>Scalpel Blades</td><td>VWR Scientific</td><td># 21909-612</td><td></td></tr><tr><td>Square Mold</td><td>VWR Scientific</td><td># 100500-224</td><td>For OCT molds</td></tr><tr><td>Sucrose</td><td>Millipore Sigma</td><td># S9378-500G</td><td></td></tr><tr><td>Superfrost Plus Slides</td><td>Fisher Scientific</td><td># 1255015</td><td></td></tr><tr><td>Surgical Scissors</td><td>Fine Science Tools</td><td># 14002-14</td><td></td></tr><tr><td>Tissue-Tek Accu-Edge Disposable Microtome Blades</td><td>VWR Scientific</td><td># 25608-964</td><td></td></tr><tr><td>Travel Scale</td><td>Acculab</td><td>VIC 5101</td><td></td></tr><tr><td>Xylene</td><td>Millipore Sigma</td><td>214736-1L</td><td></td></tr></tbody></table>

analysis of congenital heart defects in mouse embryos using qualitative and quantitative histological methods

Congenital heart defects (CHD) are the most common type of birth defect in humans, affecting up to 1% of all live births. However, the underlying causes for CHD are still poorly understood. The developing mouse constitutes a valuable model for the study of CHD, because cardiac developmental programs between mice and humans are highly conserved. The protocol describes in detail how to produce mouse embryos of the desired gestational stage, methods to isolate and preserve the heart for downstream processing, quantitative methods to identify common types of CHD by histology (e.g., ventricular septal defects, atrial septal defects, patent ductus arteriosus), and quantitative histomorphometry methods to measure common muscular compaction phenotypes. These methods articulate all the steps involved in sample preparation, collection, and analysis, allowing scientists to correctly and reproducibly measure CHD.

The muscle compaction index was compared between hearts developing under two different environments, a control and an experimental group. These protocols were used to analyze the compaction of muscle tissue quantitatively, which permitted statistical analysis. Muscle compaction was shown to be significantly reduced in the experimental hearts relative to the embryos that developed in nonexperimental conditions.
Embryos were disca...

Watch this Scientific Journal Video about Analysis of Congenital Heart Defects in Mouse Embryos Using Qualitative and Quantitative Histological Methods at JoVE.com

Analysis of Congenital Heart Defects in Mouse Embryos Using Qualitative and Quantitative Histological Methods

In this protocol, we describe procedures to qualitatively and quantitatively analyze developmental phenotypes in mice associated with congenital heart defects.

Congenital heart defects (CHD) are the most common type of birth defect in humans, affecting up to 1% of all live births. However, the underlying causes ...

analysis-congenital-heart-defects-mouse-embryos-using-qualitative

Research

JoVE Journal

Developmental Biology

6.8K Views.  Michigan State University. Dit protocol standaardiseert nieuwe weefselanalysetechnieken, zodat ze op grotere schaal kunnen worden gebruikt door andere groepen die ook aangeboren hartafwijkingen bestuderen. Aangezien zowel kwalitatieve als kwantitatieve analysetechnieken hun voor- en nadelen hebben, gebruikt deze methode beide om het breedste scala aan experimentele vragen aan te pakken. Deze technieken kunnen een positieve invloed hebben op diagnostische methoden voor cardiologie.Pathologen kunnen bijvoorbeeld o...

Video: Analysis of Congenital Heart Defects in Mouse Embryos Using Qualitative and Quantitative Histological Methods

Dual Labeling of Neural Crest Cells and Blood Vessels Within Chicken Embryos Using ChickGFP Neural Tube Grafting and Carbocyanine Dye DiI Injection

All developing organs need to be connected to both the nervous system (for sensory and motor control) as well as the vascular system (for gas exchange, fluid and nutrient supply). Consequently both the nervous and vascular systems develop alongside each other and share striking similarities in their branching architecture. Here we report embryonic manipulations that allow us to study the simultaneous development of neural crest-derived nervous tissue (in this case the enteric nervous system), and the vascular system. This is achieved by generating chicken chimeras via transplantation of discrete segments of the neural tube, and associated neural crest, combined with vascular DiI injection in the same embryo. Our method uses transgenic chickGFP embryos for intraspecies grafting, making the transplant technique more powerful than the classical quail-chick interspecies grafting protocol used with great effect since the 1970s. ChickGFP-chick intraspecies grafting facilitates imaging of transplanted cells and their projections in intact tissues, and eliminates any potential bias in cell development linked to species differences. This method takes full advantage of the ease of access of the avian embryo (compared with other vertebrate embryos) to study the co-development of the enteric nervous system and the vascular system.

Dual Labeling of Neural Crest Cells and Blood Vessels Within Chicken Embryos Using ChickGFP Neural Tube Grafting and Carbocyanine Dye DiI Injection

Here we report dual labeling of neural crest cells and blood vessels using chickGFP neural tube intraspecies grafting combined with intra-vascular DiI injection. This experimental technique allows us to simultaneously visualize and study development of the NCC-derived (enteric) nervous system and the vascular system, during organogenesis.

All developing organs need to be connected to both the nervous system (for sensory and motor control) as well as the vascular system (for gas exchange, ...

Contrast Imaging in Mouse Embryos Using High-frequency Ultrasound

Ultrasound contrast-enhanced imaging can convey essential quantitative information regarding tissue vascularity and perfusion and, in targeted applications, facilitate the detection and measure of vascular biomarkers at the molecular level. Within the mouse embryo, this noninvasive technique may be used to uncover basic mechanisms underlying vascular development in the early mouse circulatory system and in genetic models of cardiovascular disease. The mouse embryo also presents as an excellent model for studying the adhesion of microbubbles to angiogenic targets (including vascular endothelial growth factor receptor 2 (VEGFR2) or &#945;v&#946;3) and for assessing the quantitative nature of molecular ultrasound. We therefore developed a method to introduce ultrasound contrast agents into the vasculature of living, isolated embryos. This allows freedom in terms of injection control and positioning, reproducibility of the imaging plane without obstruction and motion, and simplified image analysis and quantification. Late gestational stage (embryonic day (E)16.6 and E17.5) murine embryos were isolated from the uterus, gently exteriorized from the yolk sac and microbubble contrast agents were injected into veins accessible on the chorionic surface of the placental disc. Nonlinear contrast ultrasound imaging was then employed to collect a number of basic perfusion parameters (peak enhancement, wash-in rate and time to peak) and quantify targeted microbubble binding in an endoglin mouse model. We show the successful circulation of microbubbles within living embryos and the utility of this approach in characterizing embryonic vasculature and microbubble behavior.

Here, we present a protocol to inject ultrasound microbubble contrast agents into living, isolated late-gestation stage murine embryos. This method enables the study of perfusion parameters and of vascular molecular markers within the embryo using contrast-enhanced high-frequency ultrasound imaging.

Ultrasound contrast-enhanced imaging can convey essential quantitative information regarding tissue vascularity and perfusion and, in targeted ...

Analysis of Cardiomyocyte Development using Immunofluorescence in Embryonic Mouse Heart

During heart development, the generation of myocardial-specific structural and functional units including sarcomeres, contractile myofibrils, intercalated discs, and costameres requires the coordinated assembly of multiple components in time and space. Disruption in assembly of these components leads to developmental heart defects. Immunofluorescent staining techniques are used commonly in cultured cardiomyocytes to probe myofibril maturation, but this ex vivo approach is limited by the extent to which myocytes will fully differentiate in culture, lack of normal in vivo mechanical inputs, and absence of endocardial cues. Application of immunofluorescence techniques to the study of developing mouse heart is desirable but more technically challenging, and methods often lack sufficient sensitivity and resolution to visualize sarcomeres in the early stages of heart development. Here, we describe a robust and reproducible method to co-immunostain multiple proteins or to co-visualize a fluorescent protein with immunofluorescent staining in the embryonic mouse heart and use this method to analyze developing myofibrils, intercalated discs, and costameres. This method can be further applied to assess cardiomyocyte structural changes caused by mutations that lead to developmental heart defects.

Mutations that lead to congenital heart defects benefit from in vivo investigation of cardiac structure during development, but high-resolution structural studies in the mouse embryonic heart are technically challenging. Here we present a robust immunofluorescence and image analysis method to assess cardiomyocyte-specific structures in the developing mouse heart.

During heart development, the generation of myocardial-specific structural and functional units including sarcomeres, contractile myofibrils, intercalated ...

Murine Fetal Echocardiography

Transgenic mice displaying abnormalities in cardiac development and function represent a powerful tool for the understanding the molecular mechanisms underlying both normal cardiovascular function and the pathophysiological basis of human cardiovascular disease. Fetal and perinatal death is a common feature when studying genetic alterations affecting cardiac development 1-3. In order to study the role of genetic or pharmacologic alterations in the early development of cardiac function, ultrasound imaging of the live fetus has become an important tool for early recognition of abnormalities and longitudinal follow-up. Noninvasive ultrasound imaging is an ideal method for detecting and studying congenital malformations and the impact on cardiac function prior to death 4. It allows early recognition of abnormalities in the living fetus and the progression of disease can be followed in utero with longitudinal studies 5,6. Until recently, imaging of fetal mouse hearts frequently involved invasive methods. The fetus had to be sacrificed to perform magnetic resonance microscopy and electron microscopy or surgically delivered for transillumination microscopy. An application of high-frequency probes with conventional 2-D and pulsed-wave Doppler imaging has been shown to provide measurements of cardiac contraction and heart rates during embryonic development with databases of normal developmental changes now available 6-10. M-mode imaging further provides important functional data, although, the proper imaging planes are often difficult to obtain. High-frequency ultrasound imaging of the fetus has improved 2-D resolution and can provide excellent information on the early development of cardiac structures 11.

Fetal and perinatal death is a common feature when studying genetic alterations affecting cardiac development. High-frequency ultrasound imaging has improved 2-D resolution and can provide excellent information on early cardiac development and is an ideal method to detect the impact on cardiac structure and function prior to death.

Transgenic mice displaying abnormalities in  cardiac development and function represent a powerful tool for the understanding  the molecular mechanisms ...

Medicine

Quantitative Whole-mount Immunofluorescence Analysis of Cardiac Progenitor Populations in Mouse Embryos

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development and organogenesis are two areas of research that have benefitted greatly from these advances, due to the high quality of data that can be obtained directly from imaging pre-implantation embryos or ex vivo organs. While pre-implantation embryos have yielded data with especially high spatial resolution, later stages have been less amenable to three-dimensional reconstruction. Obtaining high-quality 3D or volumetric data for known embryonic structures in combination with fate mapping or genetic lineage tracing will allow for a more comprehensive analysis of the morphogenetic events taking place during embryogenesis.
This protocol describes a whole-mount immunofluorescence approach that allows for the labeling, visualization, and quantification of progenitor cell populations within the developing cardiac crescent, a key structure formed during heart development. The approach is designed in such a way that both cell- and tissue-level information can be obtained. Using confocal microscopy and image processing, this protocol allows for three-dimensional spatial reconstruction of the cardiac crescent, thereby providing the ability to analyze the localization and organization of specific progenitor populations during this critical phase of heart development. Importantly, the use of reference antibodies allows for successive masking of the cardiac crescent and subsequent quantitative measurements of areas within the crescent. This protocol will not only enable a detailed examination of early heart development, but with adaptations should be applicable to most organ systems in the gastrula to early somite stage mouse embryo.

Here, we describe a protocol for whole mount immunofluorescence and image-based quantitative volumetric analysis of early stage mouse embryos. We present this technique as a powerful approach to qualitatively and quantitatively assess cardiac structures during development, and propose that it may be widely adaptable to other organ systems.

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development ...

Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound (30/45MHZ) System

Congenital heart defects (CHDs) are the most common cause of childhood morbidity and early mortality. Prenatal detection&#160;of the underlying molecular mechanisms of CHDs is&#160;crucial for inventing new preventive and therapeutic strategies. Mutant mouse models are powerful tools to discover new&#160;mechanisms&#160;and environmental stress modifiers that drive cardiac development and their potential&#160;alteration in CHDs. However, efforts to establish the causality of these putative contributors have been limited to histological&#160;and molecular studies&#160;in non-survival animal experiments, in which&#160;monitoring the key physiological and hemodynamic parameters is&#160;often absent. Live imaging technology has become an essential tool to establish the&#160;etiology of CHDs. In particular,&#160;ultrasound imaging can be used prenatally without surgically exposing the fetuses,&#160;allowing maintaining&#160;their baseline physiology while monitoring the impact of environmental stress&#160;on the hemodynamic and structural aspects of cardiac chamber development. Herein, we use the High-Frequency Ultrasound (30/45)&#160;system to examine the cardiovascular system in fetal mice at E18.5 in utero at the baseline and in response to prenatal hypoxia exposure. We demonstrate the feasibility of the system to measure cardiac chamber size, morphology, ventricular function, fetal heart rate, and umbilical artery flow indices, and their alterations in fetal mice exposed to systemic chronic hypoxia in utero in real time.

Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound 30/45MHZ System

High-frequency ultrasound imaging of the fetal mouse has improved imaging resolution and can provide precise non-invasive characterization of cardiac development and structural defects. The protocol outlined herein is designed to perform real-time fetal mice echocardiography in vivo.

Congenital heart defects (CHDs) are the most common cause of childhood morbidity and early mortality. Prenatal detection&#160;of the underlying molecular ...

In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

Congenital heart disease (CHD) is the most frequent noninfectious cause of death at birth. The incidence of CHD ranges from 4 to 50/1,000 births (Disease and injury regional estimates, World Health Organization, 2004). Surgeries that often compromise the quality of life are required to correct heart defects, reminding us of the importance of finding the causes of CHD. Mutant mouse models and live imaging technology have become essential tools to study the etiology of this disease. Although advanced methods allow live imaging of abnormal hearts in embryos, the physiological and hemodynamic states of the latter are often compromised due to surgical and/or lengthy procedures. Noninvasive ultrasound imaging, however, can be used without surgically exposing the embryos, thereby maintaining their physiology. Herein, we use simple M-mode ultrasound to assess heart rates of embryos at E18.5 in utero. The detection of abnormal heart rates is indeed a good indicator of dysfunction of the heart and thus constitutes a first step in the identification of developmental defects that may lead to heart failure.

In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

Ultra-high frequency ultrasound is a powerful live imaging tool to examine cardiac abnormalities in small animals. Its noninvasiveness allows maintaining the physiologic state of embryos. Herein, we show the use of M-mode ultrasound to measure the heart rates of embryos at E18.5 in utero.

Congenital heart disease (CHD) is the most frequent noninfectious cause of death at birth. The incidence of CHD ranges from 4 to 50/1,000 births (Disease ...

Analysis of Cardiac Chamber Development During Mouse Embryogenesis Using Whole Mount Epifluorescence

The goal of this protocol is to describe a method for the dissection of mouse embryos and visualization of embryonic mouse ventricular chambers during heart development using ventricular specific fluorescent reporter knock-in mice (MLC-2v-tdTomato mice). Heart development involves a linear heart tube formation, the heart tube looping, and four chamber septation. These complex processes are highly conserved in all vertebrates. The mouse embryonic heart has been widely used for heart developmental studies. However, due to their extremely small size, dissecting mouse embryonic hearts is technically challenging. In addition, visualization of cardiac chamber formation often needs in situ hybridization, beta-galactosidase staining using LacZ reporter mice, or immunostaining of sectioned embryonic hearts. Here, we describe how to dissect mouse embryonic hearts and directly visualize ventricular chamber formation of MLC-2v-tdTomato mice using whole mount epifluorescent microscopy. With this method, it is possible to directly examine heart tube formation and looping, and four chamber formation without further experimental manipulation of mouse embryos. Although the MLC-2v-tdTomato reporter knock-in mouse line is used in this protocol as an example, this protocol can be applied to other heart-specific fluorescent reporter transgenic mouse lines.

We present the protocols to examine mouse heart development using whole mount epifluorescent microscopy on mouse embryos dissected from ventricular specific MLC-2v-tdTomato reporter knock-in mice. This method allows us to directly visualize each stage of the ventricular formation during mouse heart development without labor-intensive histochemical methods.

The goal of this protocol is to describe a method for the dissection of mouse embryos and visualization of embryonic mouse ventricular chambers during ...

A Pipeline to Characterize Structural Heart Defects in the Fetal Mouse

Congenital heart diseases (CHDs) are major causes of infant death in the United States. In the 1980s and earlier, most patients with moderate or severe CHD died before adulthood, with the maximum mortality during the first week of life. Remarkable advances in surgical techniques, diagnostic approaches, and medical management have led to marked improvements in outcomes. To address the critical research needs of understanding congenital heart defects, murine models have provided an ideal research platform, as they have very similar heart anatomy to humans and short gestation rates. The combination of genetic engineering with high-throughput phenotyping tools has allowed for the replication and diagnosis of structural heart defects to further elucidate the molecular pathways behind CHDs. The use of noninvasive fetal echocardiography to screen the cardiac phenotypes in mouse models coupled with the high fidelity of Episcopic fluorescence image capture (EFIC) using Episcopic confocal microscopy (ECM) histopathology with three-dimensional (3D) reconstructions enables a detailed view into the anatomy of various congenital heart defects. This protocol outlines a complete workflow of these methods to obtain an accurate diagnosis of murine congenital heart defects. Applying this phenotyping protocol to model organisms will allow for accurate CHD diagnosis, yielding insights into the mechanisms of CHD. Identifying the underlying mechanisms of CHD provide opportunities for potential therapies and interventions.

This article details murine congenital heart disease (CHD) diagnostic methods using fetal echocardiography, necropsy, and Episcopic fluorescence image capture (EFIC) using Episcopic confocal microscopy (ECM) followed by three-dimensional (3D) reconstruction.

Congenital heart diseases (CHDs) are major causes of infant death in the United States. In the 1980s and earlier, most patients with moderate or severe ...

Echocardiographic and Histological Examination of Cardiac Morphology in the Mouse

An increasing number of genetically modified mouse models has become available in recent years. Moreover, the number of pharmacological studies performed in mice is high. Phenotypic characterization of these mouse models also requires the examination of cardiac function and morphology. Echocardiography and magnetic resonance imaging (MRI) are commonly used approaches to characterize cardiac function and morphology in mice. Echocardiographic and MRI equipment specialized for use in small rodents is&#160;expensive and requires a dedicated space. This protocol describes cardiac measurements in mice using a clinical echocardiographic system with a 15 MHz human vascular probe. Measurements are performed on anesthetized adult mice. At least three image sequences are recorded and analyzed for each animal in M-mode in the parasternal short-axis view. Afterwards, cardiac histological examination is performed, and cardiomyocyte diameters are determined on hematoxylin-eosin- or wheat germ agglutinin (WGA)-stained paraffin sections. Vessel density is determined morphometrically after Pecam-1 immunostaining. The protocol has been applied successfully to pharmacological studies and different genetic animal models under baseline conditions, as well as after experimental myocardial infarction by the permanent ligation of the left anterior descending coronary artery (LAD). In our experience, echocardiographic investigation is limited to anesthetized animals and is feasible in adult mice weighing at least 25 g.

Echocardiographic examination is frequently used in mice. Expensive high-resolution ultrasound devices have been developed for this purpose. This protocol describes an affordable echocardiographic procedure combined with histological morphometric analyses to determine cardiac morphology.

An increasing number of genetically modified mouse models has become available in recent years. Moreover, the number of pharmacological studies performed ...

Analysis of Congenital Heart Defects in Mouse Embryos Using Qualitative and Quantitative Histological Methods

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