We would like to thank Andrea Portbury for critical reading of the manuscript and the NIH (grant # R01HL061656) for funding support.

1. Excising the Embryonic Hearts
<ol>
	<li>Euthanize a timed-pregnant mouse at the desired embryonic day using an approved euthanasia technique. All experiments were approved by the Institutional Animal Care and Use Committee at the University of North Carolina at Chapel Hill.</li>
	<li>Liberally spray the female with 70% ethanol prior to dissection. Open the female's abdominal cavity to retrieve and excise the uterine horn.</li>
	<li>Place the uterine horn in a Petri dish containing cold 1x phosphate-buffered saline (PBS) and rinse as needed. Cut open the uterine horn via the midline to expose the attached embryonic sacs.</li>
	<li>Cut open an embryonic sac and retrieve an embryo. Place the embryo in a second Petri dish with cold PBS. Return the Petri dish with the uterine horn to ice.</li>
	<li>Decapitate the embryo to improve access to the chest wall. If genotyping is necessary, remove and save the tail in an Eppendorf tube placed on ice.</li>
	<li>With the embryo on its back, cut open the chest wall to visualize the heart and lungs. Depending on the stage, the chest wall may be transparent.</li>
	<li>Carefully lift the heart using forceps and cut the vessels below. Then, cut above the great vessels to free the heart. If necessary, remove extraneous tissues.</li>
	<li>Place the heart in one well of a 24-well dish filled with cold PBS and place the dish on ice.</li>
	<li>Repeat the previous steps until hearts have been excised from all embryos.</li>
</ol>
2. Culture Set-up
<ol>
	<li>In a laminar hood, combine cold Matrigel and the desired culture medium (e.g. 10% fetal bovine serum (FBS) in Dulbecco's Modified Eagle Medium (DMEM)) at a 1:1 ratio. Do not pre-warm the culture medium.</li>
	<li>Keeping the dilute Matrigel on ice, pipette 500-1,000 &mu;l of the diluted solution into a well of a 24-well culture dish that is also maintained on ice.</li>
	<li>In the hood, carefully pick up and place the excised heart in a well of the Matrigel-containing culture dish while keeping the culture dish on ice.</li>
	<li>If orientation of the embedded heart is crucial: Liberally spray an inverted microscope and the surrounding space with 70% ethanol. In the hood, place the excised heart in a well of the Matrigel-containing culture plate while still on ice. Then, place the plate on a microscope and quickly orient the excised heart as the Matrigel begins to solidify.</li>
	<li>Place the culture dish in a humidified 37 &deg;C incubator (5% CO2) and allow the Matrigel to solidify for approximately 30 min.</li>
	<li>Add 1 ml pre-warmed culture medium to each well containing a heart.</li>
	<li>Hearts can remain in culture for at least four days. Changing the culture medium every two days is recommended.</li>
</ol>
3. Fixation and Visualization
<ol>
	<li>If desired, add a fluorescent live-cell dye (e.g. Syto-16) to visualize the live heart. Photography will be limited to the side of the heart that is visible based on the position in which it was embedded.</li>
	<li>If post-culturing analyses (e.g. whole mount imaging or sectioning) will be performed, remove the culture medium and replace with cold 4% formaldehyde. Place the dish on ice for 30 min.</li>
	<li>After the cold formaldehyde and ice promote dissolution of the Matrigel, replace the fixative (and Matrigel) with fresh formaldehyde and fix hearts overnight at 4 &deg;C.</li>
	<li>Wash the hearts with buffer (e.g. PBS or Tris) and store at 4 &deg;C until further analyses.</li>
</ol>

<ol>
	<li>Tu, S., Chi, 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=Zebrafish+models+in+cardiac+development+and+congenital+heart+birth+defects.">Zebrafish models in cardiac development and congenital heart birth defects.</a> Differentiation. 84, 4-16 (2012).</li><li>Lavine, 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=Fibroblast+growth+factor+signals+regulate+a+wave+of+Hedgehog+activation+that+is+essential+for+coronary+vascular+development.">Fibroblast growth factor signals regulate a wave of Hedgehog activation that is essential for coronary vascular development.</a> Genes Dev. 20, 1651-1666 (2006).</li><li>Red-Horse, K., Ueno, H., Weissman, I. L., Krasnow, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coronary+arteries+form+by+developmental+reprogramming+of+venous+cells.">Coronary arteries form by developmental reprogramming of venous cells.</a> Nature. 464, 549-553 (2010).</li><li>Stuckmann, I., Evans, S., Lassar, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Erythropoietin+and+retinoic+acid,+secreted+from+the+epicardium,+are+required+for+cardiac+myocyte+proliferation.">Erythropoietin and retinoic acid, secreted from the epicardium, are required for cardiac myocyte proliferation.</a> Dev. Biol. 255, 334-349 (2003).</li><li>Zhang, 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=The+FGF-BMP+signaling+axis+regulates+outflow+tract+valve+primordium+formation+by+promoting+cushion+neural+crest+cell+differentiation.">The FGF-BMP signaling axis regulates outflow tract valve primordium formation by promoting cushion neural crest cell differentiation.</a> Circ. Res. 107, 1209-1219 (2010).</li><li>Pillekamp, F., 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=Establishment+and+characterization+of+a+mouse+embryonic+heart+slice+preparation.">Establishment and characterization of a mouse embryonic heart slice preparation.</a> Cellular Physiology and Biochemistry: international journal of experimental cellular physiology, biochemistry, and pharmacology. 16, 127-132 (2005).</li><li>Habeler, W., Peschanski, M., Monville, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organotypic+heart+slices+for+cell+transplantation+and+physiological+studies.">Organotypic heart slices for cell transplantation and physiological studies.</a> Organogenesis. 5, 62-66 (2009).</li><li>Janssen, P. M., Lehnart, S. E., Prestle, J., Hasenfuss, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preservation+of+contractile+characteristics+of+human+myocardium+in+multi-day+cell+culture.">Preservation of contractile characteristics of human myocardium in multi-day cell culture.</a> J. Mol. Cell Cardiol. 31, 1419-1427 (1999).</li><li>Brandenburger, M., 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=Organotypic+slice+culture+from+human+adult+ventricular+myocardium.">Organotypic slice culture from human adult ventricular myocardium.</a> Cardiovasc. Res. 93, 50-59 (2012).</li><li>Weaver, M., Dunn, N. R., Hogan, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bmp4+and+Fgf10+play+opposing+roles+during+lung+bud+morphogenesis.">Bmp4 and Fgf10 play opposing roles during lung bud morphogenesis.</a> Development. , 127-2695 (2000).</li><li>Viragh, S., Challice, 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=The+origin+of+the+epicardium+and+the+embryonic+myocardial+circulation+in+the+mouse.">The origin of the epicardium and the embryonic myocardial circulation in the mouse.</a> Anat. Rec. 201, 157-168 (1981).</li><li>Kirby, M. 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The authors declare that they have no competing financial interests.

The current culture system poses significant advantages for embryonic mouse heart studies. This culture system preserves myocardial contractility and the coronary plexus, with limited signs of necrosis, even after four days in culture. Further, the semi-solid matrix provides enough support to maintain the three-dimensional morphology of the developing heart while allowing flexibility to contract and also to hold coated beads in place during culture. Despite this support, this matrix is permeable to fluorescent dye...

Over recent years, the transgenic mouse has been the predominant model system for studying development heart defects. However, other model organisms, such as the zebrafish, have proven to have significant advantages over the mouse. Three major advantages of the zebrafish are the external laying of eggs, for ease of access to the embryos; the optical transparency of the embryos, which allows easy visualization of cardiac development; and the ease of applying small molecular treatments to modulate development of the embryo1. Thus, the development of a culture technique that allowed ex utero growth of an embryonic organ would bypass, at least in part, the limitations currently experienced by researchers studying developmental processes in transgenic mice.
	Ex vivo cardiac culture systems have been developed in both the chick and mouse embryo that allow treatment with small molecules and analysis of how different regions of the heart communicate2-6. For whole mouse heart culture, hearts taken from embryos up to embryonic (E) 12.5 of age can be placed in culture medium with or without rocking2,3,5. Using this technique, embryonic hearts have been successfully incubated to the equivalency of E13.5, and hearts cultured with rocking have been maintained as long as three days (starting at E10.5)3. However, no studies have reported the successful culture of hearts from older embryos. Likewise, rescue experiments have been limited to applying the therapeutic agent globally to the culture medium2.
	A slice culture system, in which hearts are excised, embedded, and sectioned using a vibratome, has also been utilized for both younger hearts, such as E12.5 mouse hearts and Hamburger-Hamilton stage 36 (approximately E16 in the mouse) chick hearts2,4,6, and older hearts, such as post-natal and adult mouse hearts and adult human hearts7,8. While the embryonic analyses have typically utilized 150-&mu;m thick sections2,4, section thickness can be a great as 500 &mu;m without evidence of oxygen deprivation8. These slice cultures have been maintained as long as two months in culture, with most slices maintaining contractility throughout this period9. Compared to studies in isolated cardiomyocytes, these slice cultures allow the co-culture of cardiomyocytes with their neighboring cell types and provide a useful method for ex vivo analysis. However, these cultures require more elaborate set-up than simply placing a heart in culture medium (e.g. embedding the live heart for sectioning on a vibratome), and any analysis is obviously limited to the portion of the heart within the section.
	Given the limitations described above for culturing embryonic mouse hearts and the wealth of transgenic mice available for study, we developed an ex vivo mouse heart culture system similar to an ex vivo lung culture system developed by Weaver, et al.10 Our culture system permits long-term culture and visualization of the remodeling coronary circulation within whole embryonic mouse hearts. In addition, the use of Matrigel allows beads to be held in place near the heart, thus providing a localized treatment with therapeutic agents. These experiments can be performed at different developmental time points to compare the effect of a given treatment on a process such as coronary artery formation. Because small molecules can diffuse through Matrigel, this culture system can also be used to culture dissected regions of the heart near each other to determine whether specific cell-cell contacts are necessary for certain developmental processes or whether paracrine signaling from one region to the other is necessary.
	This culture system is relatively simple and, unlike the slice culture system, makes use of basic culture reagents and set-ups that are readily available in most laboratories. In brief, excised embryonic hearts are cultured in dilute Matrigel, which provides a semi-solid support. This support is sufficient to maintain the three-dimensional morphology of the heart while also allowing the heart to contract. Using this system, whole hearts from older mouse embryos (E14.5-E16.5) can be maintained in culture for up to four days. The entire coronary plexus is maintained, unlike in the slice cultures, so any signaling cues that occur from different regions of the heart remain present. Furthermore, live-cell fluorescent dyes can permeate the Matrigel to allow visualization of the live heart, and protein-conjugated beads can be placed near the heart to provide a localized signaling source. Together, these benefits make this technique an ideal method for studying developmental processes in the embryonic mouse heart.

<table border="1">
<tbody>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>REAGENTS</td>
 </tr>
 <tr>
 <td>Timed-pregnant mice</td>
 <td></td>
 <td></td>
 <td>To be dissected at the embryonic stage of interest</td>
 </tr>
 <tr>
 <td>PBS (1x)</td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>DMEM</td>
 <td>Cellgro </td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>FBS</td>
 <td>Sigma-Aldrich </td>
 <td>F2442 </td>
 <td></td>
 </tr>
 <tr>
 <td>Growth factor-reduced Matrigel</td>
 <td>BD Bioscience </td>
 <td>356231 </td>
 <td></td>
 </tr>
 <tr>
 <td>Syto-16</td>
 <td>Invitrogen </td>
 <td>S7578 </td>
 <td>Used as directed in 13 </td>
 </tr>
 <tr>
 <td>24-well culture plate</td>
 <td>Fisher Scientific</td>
 <td>07-200-84</td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>EQUIPMENT</td>
 </tr>
 <tr>
 <td>Stereoscopic microscope</td>
 <td>Nikon </td>
 <td>SMZ645</td>
 <td></td>
 </tr>
 <tr>
 <td>Cell culture incubator</td>
 <td>Thermo </td>
 <td>3110 </td>
 <td></td>
 </tr>
</tbody>
 </table>

a novel ex vivo culture method for the embryonic mouse heart

Developmental studies in the mouse are hampered by the inaccessibility of the embryo during gestation. Thus, protocols to isolate and culture individual organs of interest are essential to provide a method of both visualizing changes in development and allowing novel treatment strategies. To promote the long-term culture of the embryonic heart at late stages of gestation, we developed a protocol in which the excised heart is cultured in a semi-solid, dilute Matrigel. This substrate provides enough support to maintain the three-dimensional structure but is flexible enough to allow continued contraction. In brief, hearts are excised from the embryo and placed in a mixture of cold Matrigel diluted 1:1 with growth medium. After the diluted Matrigel solidifies, growth medium is added to the culture dish. Hearts excised as late as embryonic day 16.5 were viable for four days post-dissection. Analysis of the coronary plexus shows that this method does not disrupt coronary vascular development. Thus, we present a novel method for long-term culture of embryonic hearts.

Using this technique, the heart maintains its three-dimensional morphology and remains viable, as indicated by continued contractions (Movie 1). These contractions are consistently more prominent in the atria than in the ventricles. Following culture, hearts can be fixed and processed for either immunohistochemistry or histology to examine specific marker expression or structures. Figure 1A shows the base of the ventricles and great arteries of an embryonic mouse heart that was cu...

Watch this Scientific Journal Video about A Novel Ex vivo Culture Method for the Embryonic Mouse Heart at JoVE.com

A Novel Ex vivo Culture Method for the Embryonic Mouse Heart

Developmental studies in the mouse are hampered by the inaccessibility of the embryo during gestation. To promote the long-term culture of the embryonic heart at late stages of gestation, we developed a protocol in which the excised heart is cultured in a semi-solid, dilute Matrigel.

A Novel Ex vivo Culture Method for the Embryonic Mouse Heart

Developmental studies in the mouse are hampered  by the inaccessibility of the embryo during gestation. Thus, protocols to  isolate and culture individual ...

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13.2K Views.  University of North Carolina at Chapel Hill. Developmental studies in the mouse are hampered by the inaccessibility of the embryo during gestation. To promote the long-term culture of the embryonic heart at late stages of gestation, we developed a protocol in which the excised heart is cultured in a semi-solid, dilute Matrigel.

Video: A Novel Ex vivo Culture Method for the Embryonic Mouse Heart

Method for Culture of Early Chick Embryos ex vivo (New Culture)

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying  the formation and patterning of brain, neural tube, somite and heart primordia. Applications of chick embryo culture include electroporation of DNA or RNA constructs in order to analyze gene function, grafts of growth factor coated beads such as FGFs and BMPs , as well as whole mount in situ hybridization and immunohistochemistry. This video demonstrates the different steps in chick embryo culture; First, the embryo is explanted in saline. Then, the embryo is centered on a glass ring. The membranes surrounding the embryo are lifted along the walls of the ring. The ring is then placed in a culture dish containing a pool of albumine. The culture dish is sealed and placed in a humid chamber, where the embryo is cultured for up to 24 hrs. Finally, the embryo is removed from the ring, fixed and processed for further applications. A troubleshooting guide is also presented.

Method for Culture of Early Chick Embryos ex vivo New Culture

This video demonstrates New culture, a method by which chick embryos are cultured outside the egg for up to 24 hr. This method enables one to study early development (primitive streak to 14 som.), a period corresponding to E7-9 in mouse. Applications of this technique include electroporation, in situ hybridization and immunohistochemistry.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Mouse Embryonic Lung Culture, A System to Evaluate the Molecular Mechanisms of Branching

Lung primordial specification as well as branching morphogenesis, and the formation of various pulmonary cell lineages requires a specific interaction of the lung endoderm with its surrounding mesenchyme and mesothelium. Lung mesenchyme has been shown to be the source of inductive signals for lung branching morphogenesis. Epithelial-mesenchymal-mesothelial interactions are also critical to embryonic lung morphogenesis. Early embryonic lung organ culture is a very useful system to study epithelial-mesenchymal interactions. Both epithelial and mesenchymal morphogenesis proceeds under specific conditions that can be readily manipulated in this system (in the absence of maternal influence and blood flow). More importantly this technique can be readily done in a serumless, chemically defined culture media. Gain and loss of function can be achieved using expressed proteins, recombinant viral vectors and/or analysis of transgenic mouse strains, antisense RNA, as well as RNA interference gene knockdown.

Early embryonic lung organ culture is a very useful system to study epithelial-mesenchymal interactions. Both epithelial and mesenchymal morphogenesis proceeds under specific conditions that can be readily manipulated in this system.

Lung primordial specification as well as branching morphogenesis, and the formation of various pulmonary cell lineages requires a specific interaction of ...

A System for ex vivo Culturing of Embryonic Pancreas

The pancreas controls vital functions of our body, including the production of digestive enzymes and regulation of blood sugar levels1. Although in the past decade many studies have contributed to a solid foundation for understanding pancreatic organogenesis, important gaps persist in our knowledge of early pancreas formation2. A complete understanding of these early events will provide insight into the development of this organ, but also into incurable diseases that target the pancreas, such as diabetes or pancreatic cancer. Finally, this information will generate a blueprint for developing cell-replacement therapies in the context of diabetes.
 During embryogenesis, the pancreas originates from distinct embryonic outgrowths of the dorsal and ventral foregut endoderm at embryonic day (E) 9.5 in the mouse embryo3,4. Both outgrowths evaginate into the surrounding mesenchyme as solid epithelial buds, which undergo proliferation, branching and differentiation to generate a fully mature organ2,5,6. Recent evidences have suggested that growth and differentiation of pancreatic cell lineages, including the insulin-producing &beta;-cells, depends on proper tissue-architecture, epithelial remodeling and cell positioning within the branching pancreatic epithelium7,8. However, how branching morphogenesis occurs and is coordinated with proliferation and differentiation in the pancreas is largely unknown. This is in part due to the fact that current knowledge about these developmental processes has relied almost exclusively on analysis of fixed specimens, while morphogenetic events are highly dynamic.
 Here, we report a method for dissecting and culturing mouse embryonic pancreatic buds ex vivo on glass bottom dishes, which allow direct visualization of the developing pancreas (Figure 1). This culture system is ideally devised for confocal laser scanning microscopy and, in particular, live-cell imaging. Pancreatic explants can be prepared not only from wild-type mouse embryos, but also from genetically engineered mouse strains (e.g. transgenic or knockout), allowing real-time studies of mutant phenotypes. Moreover, this ex vivo culture system is valuable to study the effects of chemical compounds on pancreatic development, enabling to obtain quantitative data about proliferation and growth, elongation, branching, tubulogenesis and differentiation. In conclusion, the development of an ex vivo pancreatic explant culture method combined with high-resolution imaging provides a strong platform for observing morphogenetic and differentiation events as they occur within the developing mouse embryo.

A System for ex vivo Culturing of Embryonic Pancreas

Here, we describe a method for isolation, culture and manipulation of mouse embryonic pancreas. This represents an excellent ex vivo system for studying various aspects of pancreatic development, including morphogenesis, differentiation and growth. Pancreatic bud explants can be cultured for several days and used in a range of different applications, including whole-mount immunofluorescence and live imaging.

The pancreas controls vital functions of our body,  including the production of digestive enzymes and regulation of blood sugar  levels1. Although in the ...

A Novel Method for the Culture and Polarized Stimulation of Human Intestinal Mucosa Explants

Few models currently exist to realistically simulate the complex human intestine's micro-environment, where a variety of interactions take place. Proper homeostasis directly depends on these interactions, as they shape an entire immunological response inducing tolerance against food antigens while at the same time mounting effective immune responses against pathogenic microbes accidentally ingested with food.
Intestinal homeostasis is preserved also through various complex interactions between the microbiota (including food-associated beneficial bacterial strains) and the host, that regulate the attachment/degradation of mucus, the production of antimicrobial peptides by the epithelial barrier, and the "education" of epithelial cells' that controls the tolerogenic or immunogenic phenotype of unique, gut-resident lymphoid cells' populations. These interactions have been so far very difficult to reproduce with in vitro assays using either cultured cell lines or peripheral blood mononuclear cells. In addition, mouse models differ substantially in components of the intestinal mucosa (mucus layer organization, commensal bacteria community) with respect to the human gut. Thus, studies of a variety of treatments to be brought in the clinics for important stress-related or pathological conditions such as irritable bowel syndrome, inflammatory bowel disease or colorectal cancer have been difficult to carry out.
To address these issues, we developed a novel system that enables us to stimulate explants of human intestinal mucosa that retain their in situ conditioning by the host microbiota and immune response, in a polarized fashion. Polarized apical stimulation is of great importance for the outcome of the elicited immune response. It has been repeatedly shown that the same stimuli can produce completely different responses when they bypass the apical face of the intestinal epithelium, stimulating epithelial cells basolaterally or coming into direct contact with lamina propria components, switching the phenotype from tolerogenic to immunogenic and causing unnecessary and excessive inflammation in the area.
We achieved polarized stimulation by gluing a cave cylinder which delimited the area of stimulation on the apical face of the mucosa as will be described in the protocol. We used this model to examine, among others, differential effects of three different Lactobacilli strains. We show that this model system is very powerful to assess the immunomodulatory properties of probiotics in healthy and disease conditions.

We introduce a novel method for the maintenance of human intestinal mucosa in culture and monitoring of the response to various types of stimuli over at least 24 hrs. With our method, the polarity of the tissue is maintained, allowing for a physiological stimulation via the apical route.

Few models currently exist to realistically simulate the complex human intestine's micro-environment, where a variety of interactions take place. Proper ...

Isolation of Embryonic Ventricular Endothelial Cells

Cell culture has greatly enhanced our ability to assess individual populations of cells under myriad culture conditions. While immortalized cell lines offer significant advantages for their ease of use, these cell lines are unavailable for all potential cell types. By isolating primary cells from a specific region of interest, particularly from a transgenic mouse, more nuanced studies can be performed. The basic technique involves dissecting the organ or partial organ of interest (e.g. the heart or a specific region of the heart) and dissociating the organ to single cells. These cells are then incubated with magnetic beads conjugated to an antibody that recognizes the cell type of interest. The cells of interest can then be isolated with the use of a magnet, with a short trypsin incubation dissociating the cells from the beads. These isolated cells can then be cultured and analyzed as desired. This technique was originally designed for adult mouse organs but can be easily scaled down for use with embryonic organs, as demonstrated herein. Because our interest is in the developing coronary vasculature, we wanted to study this population of cells during specific embryonic stages. Thus, the original protocol had to be modified to be compatible with the small size of the embryonic ventricles and the low potential yield of endothelial cells at these developmental stages. Utilizing this scaled-down approach, we have assessed coronary plexus remodeling in transgenic embryonic ventricular endothelial cells.

Primary cell culture is a useful technique for analyzing specific populations of cells, particularly from transgenic mouse embryos at specific developmental stages. Herein, embryonic ventricles are dissected and dissociated, and antibody-conjugated beads recognize and separate out the endothelial cells for further analysis.

Cell culture has greatly enhanced our ability to assess individual populations of cells under myriad culture conditions. While immortalized cell lines ...

Mouse Embryonic Development in a Serum-free Whole Embryo Culture System

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 &#176;&#8203;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.

Serum utilized in embryo cultures contains unknown components that can affect the outcome of experiments especially in studies involving signaling interactions. Here we utilized a serum-free oxygenated culture system and show that mid-gestation mouse embryos cultured for 16-40 hr&#160;exhibit morphological development comparable to embryos developing in utero.

Mid-gestation stage mouse embryos were cultured utilizing a serum-free culture medium prepared from commercially available stem cell media supplements in ...

Ex vivo Culture of Mouse Embryonic Skin and Live-imaging of Melanoblast Migration

Melanoblasts are the neural crest derived precursors of melanocytes; the cells responsible for producing the pigment in skin and hair. Melanoblasts migrate through the epidermis of the embryo where they subsequently colonize the developing hair follicles1,2. Neural crest cell migration is extensively studied in vitro but in vivo methods are still not well developed, especially in mammalian systems. One alternative is to use ex vivo organotypic culture3-6. Culture of mouse embryonic skin requires the maintenance of an air-liquid interface (ALI) across the surface of the tissue3,6. High resolution live-imaging of mouse embryonic skin has been hampered by the lack of a good method that not only maintains this ALI but also allows the culture to be inverted and therefore compatible with short working distance objective lenses and most confocal microscopes. This article describes recent improvements to a method that uses a gas permeable membrane to overcome these problems and allow high-resolution confocal imaging of embryonic skin in ex vivo culture6. By using a melanoblast specific Cre-recombinase expressing mouse line combined with the R26YFPR reporter line we are able to fluorescently label the melanoblast population within these skin cultures. The technique allows live-imaging of melanoblasts and observation of their behavior and interactions with the tissue in which they develop. Representative results are included to demonstrate the capability to live-image 6&#160;cultures in parallel.

Ex vivo Culture of Mouse Embryonic Skin and Live-imaging of Melanoblast Migration

We describe the dissection and ex vivo culture of mouse embryonic skin. The culture system maintains an air-liquid interface across the tissue surface and allows imaging on an inverted microscope. Melanoblasts, a component of the developing skin, are fluorescently labeled allowing their behavior to be observed using confocal microscopy.

Melanoblasts are the neural crest derived precursors of melanocytes; the cells responsible for producing the pigment in skin and hair. Melanoblasts ...

Protein Isolation from the Developing Embryonic Mouse Heart Valve Region

Western blot analysis is a commonly employed technique for detecting and quantifying protein levels. However, for small tissue samples, this analysis method may not be sufficiently sensitive to detect a protein of interest. To overcome these difficulties, we examined protocols for obtaining protein from adult human cardiac valves and modified these protocols for the developing early embryonic mouse counterparts. In brief, the mouse embryonic aortic valve regions, including the aortic valve and surrounding aortic wall, are collected in the minimal possible volume of a Tris-based lysis buffer with protease inhibitors. If required based on the breeding strategy, embryos are genotyped prior to pooling four embryonic aortic valve regions for homogenization. After homogenization, an SDS-based sample buffer is used to denature the sample for running on an SDS-PAGE gel and subsequent western blot analysis. Although the protein concentration remains too low to quantify using spectrophotometric protein quantification assays and have sample remaining for subsequent analyses, this technique can be used to successfully detect and semi-quantify phosphorylated proteins via western blot from pooled samples of four embryonic day 13.5 mouse aortic valve regions, each of which yields approximately 1 &#956;g of protein. This technique will be of benefit for studying cell signaling pathway activation and protein expression levels during early embryonic mouse valve development.

The analysis of protein expression in young embryonic mouse valves has been hampered by the limited tissue available. This manuscript provides a protocol for preparing protein from developing embryonic mouse valve regions for western blot analysis.

Western blot analysis is a commonly employed technique for detecting and quantifying protein levels. However, for small tissue samples, this analysis ...

The c-FOS Protein Immunohistological Detection: A Useful Tool As a Marker of Central Pathways Involved in Specific Physiological Responses In Vivo and Ex Vivo

Many studies seek to identify and map the brain regions involved in specific physiological regulations. The proto-oncogene c-fos, an immediate early gene, is expressed in neurons in response to various stimuli. The protein product can be readily detected with immunohistochemical techniques leading to the use of c-FOS detection to map groups of neurons that display changes in their activity. In this article, we focused on the identification of brainstem neuronal populations involved in the ventilatory adaptation to hypoxia or hypercapnia. Two approaches were described to identify involved neuronal populations in vivo in animals and ex vivo in deafferented brainstem preparations. In vivo, animals were exposed to hypercapnic or hypoxic gas mixtures. Ex vivo, deafferented preparations were superfused with hypoxic or hypercapnic artificial cerebrospinal fluid. In both cases, either control in vivo animals or ex vivo preparations were maintained under normoxic and normocapnic conditions. The comparison of these two approaches allows the determination of the origin of the neuronal activation i.e., peripheral and/or central. In vivo and ex vivo, brainstems were collected, fixed, and sliced into sections. Once sections were prepared, immunohistochemical detection of the c-FOS protein was made in order to identify the brainstem groups of cells activated by hypoxic or hypercapnic stimulations. Labeled cells were counted in brainstem respiratory structures. In comparison to the control condition, hypoxia or hypercapnia increased the number of c-FOS labeled cells in several specific brainstem sites that are thus constitutive of the neuronal pathways involved in the adaptation of the central respiratory drive.

The c-FOS Protein Immunohistological Detection: A Useful Tool As a Marker of Central Pathways Involved in Specific Physiological Responses In Vivo and Ex Vivo

Here, we present a protocol based on c-FOS protein immunohistological detection, a classical technique used for the identification of neuronal populations involved in specific physiological responses in vivo and ex vivo.

Many studies seek to identify and map the brain regions involved in specific physiological regulations. The proto-oncogene c-fos, an immediate early gene, ...

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a versatile analytical tool for characterizing viscoelastic mechanical properties for a variety of materials ranging from hard (plastic, glass, metal, etc.) surfaces to cells on any substrate. It has been widely used to measure the stiffness of cells, but less frequently used to measure the stiffness of aortas. In this paper, we will describe the procedures for using AFM in contact mode to measure the ex vivo elastic modulus of unloaded mouse arteries. We describe our procedure for isolation of mouse aortas, and then provide detailed information for the AFM analysis. This includes step-by-step instructions for alignment of the laser beam, calibration of the spring constant and deflection sensitivity of the AFM probe, and acquisition of force curves. We also provide a detailed protocol for data analysis of the force curves.

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

We present detailed protocols for isolation of aortas from mouse and measurement of their elastic modulus using atomic force microscopy.

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a ...