The authors thank Mira Hryniuk, BA, for reviewing the English language of the article.

The use of human tissue was approved by the Institutional Review Board of the Catholic University of Louvain. The patients gave their written informed consent for the use of their ovarian tissue for research purposes.
1. Ordering day 0 eggs that are highly likely to be embryonated
<ol>
	<li>Find a certified laboratory-grade Lohman-selected white Leghorn egg supplier that reports high rates of embryonated eggs, which is primarily dependent on the age of the chicks.</li>
</ol>
2. Preparing the eggs for incubation
<ol>
	<li>Prior to the arrival of the eggs, assemble and equilibrate the egg incubator to 37 &#176;C in 40%-60% relative air humidity. Monitor the temperature and air humidity by inserting a thermometer and hygrometer into the incubator. Ensure the lid of the incubator is equipped with a glass window to allow for checking the internal parameters of the incubator without having to open it (Figure 1).</li>
	<li>Having received the day 0 eggs from Lohman-selected white Leghorn chicks from a certified laboratory-grade egg supplier, clean the surface of the shells with humidified paper, and dry them immediately. 
	NOTE: Since the eggshell membrane is porous, autoclaved water may be used to clean egg surfaces and control humidity within the incubator in order to minimize contamination risks.</li>
	<li>Label the eggs using a marker (e.g., date and egg number).</li>
	<li>Incubate the eggs with the pointed end facing down, and rotate them to allow the CAM to develop. Manually rotate the eggs by 180&#176; two to three times per day or use&#160;an automatic rotator. 
	NOTE: In order to ensure the eggs are indeed being rotated, the eggshell may be marked with an &#34;X&#34; and &#34;O&#34; on the two opposing lateral sides using a pencil or marker. The glass window in the lid of the incubator allows one to check the rotation of the eggs without opening the device.</li>
</ol>
3. Opening the eggshell on day 3 of ED
NOTE: A rectangular window is made in the eggshell on day 3 of ED.
<ol>
	<li>Prepare the laminar flow hood in order to work in sterile conditions. Place the following instruments under the hood, and disinfect them in 70% ethanol (if not already sterilized): 
	-Egg rack 
	-Egg candler or focal cold light source 
	-Marker 
	-Sterile straight pin 
	-Sterile 19 G needle 
	-5&#160;mL sterile syringe 
	-Scroll saw blade 
	-Sterile forceps 
	-Adhesive tape</li>
	<li>Transfer one egg from the incubator to the egg rack placed under the hood, and turn off the egg rotator.</li>
	<li>In the dark, identify the air pocket of the egg by placing the egg candler (or focal cold light source) against the eggshell. The air pocket is localized at the blunt end of the egg. Use a marker to pinpoint the center of the air pocket on the eggshell.</li>
	<li>Turn on the lights. Make a small hole in the eggshell where it is marked by gently rotating a sterile straight pin. A tiny opening of around 1 mm in diameter is usually sufficient. 
	NOTE: Be careful not to push the pin all the way through the egg. If this happens, discard the egg.</li>
	<li>Connect a sterile 19 G needle to a sterile 5 mL syringe.</li>
	<li>In the dark, locate the yolk sac using the egg candler (or focal cold light source), and puncture the egg through the hole made in step 3.4 with the sterile 19 G needle angled at 45&#176; toward the bottom of the egg; take great care not to disrupt the yolk sac. Aspirate between 1.5-2 mL of albumen to detach the CAM from the shell, and then close the hole with a piece of adhesive tape. 
	NOTE: If the yolk sac is disrupted during aspiration, the aspirated liquid in the syringe will be yellow-colored rather than transparent (albumen). If this happens, replace the needle and syringe. If a relatively large amount of egg yolk is sucked up, it may jeopardize the viability of the embryo.</li>
	<li>Turn on the lights. Place the egg horizontally, and draw a rectangular window measuring 1 cm x 1.5 cm with a marker. Do not make the window larger than the usual width of standard adhesive tape.</li>
	<li>Hold the egg in one hand, and gently saw the previously drawn&#160;window into the eggshell using a scroll saw blade. Ensure that the shell does not crack and do not&#160;cut all the way down to the depressed CAM. Blow regularly to remove shell dust and debris.</li>
	<li>Slide sterile forceps under the rectangular piece of sawed shell, and grasp deftly to remove it cleanly without damaging the CAM. Additionally, discard the white outer shell membrane to be able to see the embryo and its CAM. 
	NOTE: If some eggshell dust or debris falls onto the CAM, it may be removed using sterile forceps, being very careful not to tear the CAM.</li>
	<li>Identify viable embryonated eggs. They are discernible by their clear albumen and the vascular ring around the embryo, where a beating heart may sometimes be detected even at this stage (day 3 of ED). Discard non-fertilized or dead embryos.</li>
	<li>Place adhesive tape over the newly created window to avoid dehydration. Be sure to fold one end over itself for ease of removal.</li>
	<li>Put the egg back in the incubator with the opened window facing up and the tape not touching the CAM. Use a folded piece of paper or part of the egg rack to stop the egg from rolling. Make sure the rotating tray is off.</li>
	<li>Repeat steps 3.2-3.12 to open the remaining eggs.</li>
</ol>
4. Grafting frozen-thawed human ovarian tissue to the CAM
NOTE: Transplantation to the CAM should ideally be initiated between days 7-10 of ED.
<ol>
	<li>Thaw cryopreserved ovarian cortical strips under the laminar flow hood following the protocol described elsewhere30.</li>
	<li>Cut the cortical strips into three fragments of 4 mm x 2 mm x 1 mm. Use one piece as a non-grafted control and the other two for xenografting for 1 day or 6 days. 
	NOTE: If enough tissue is available, work in duplicate.</li>
	<li>Transfer one egg from the incubator to the egg rack positioned under the hood, with the window facing up.</li>
	<li>Peel the tape off the window, and ensure that the embryo is viable. At this stage, viable embryos feature extensive vasculature, a clear albumen, a visible heartbeat, and some embryo movement.</li>
	<li>Prepare the grafting site by gently traumatizing&#160;a small area of the CAM by laying a 1 cm2 strip of sterile ether-extracted lens paper onto the epithelial surface and removing it immediately. 
	NOTE: The CAM is an impenetrable barrier unless the membrane has been traumatized by the removal of the upper peridermal part of the double epithelial layer, leaving the basal layer intact. This technique also enhances the revascularization process by activating wound healing. If the sterile ether-extracted lens paper stays on the CAM too long, the membrane may adhere to the lens paper and tear. If this happens, discard the egg.&#160;</li>
	<li>Grasp one frozen-thawed ovarian cortical strip (4 mm x 2 mm x 1 mm) with microsurgical forceps, and place it onto the traumatized CAM with the medullary side against the CAM. Graft one tissue piece per egg.</li>
	<li>Cover the window with adhesive tape, and carefully return the egg to the incubator. Ensure that the eggshell opening sits upright and the egg is secure.</li>
	<li>Repeat steps 4.1-4.7 for the grafting of all the remaining tissues. 
	NOTE: The implants should be checked on each grafting day to assess the embryo viability and monitor changes in the vasculature.</li>
</ol>
5. Harvesting the grafts
NOTE: Xenografts should be harvested at the latest by day 17 of ED, since the immune system of the embryo becomes mature and competent from day 18.
<ol>
	<li>Place the egg on a rack, and enlarge the window in the eggshell to allow for better graft visualization and easier manipulation.</li>
	<li>Evaluate the graft macroscopically, and pay particular attention to the vascular reaction of the CAM towards the graft. Take digital photographs or videos for the record.</li>
	<li>Grasp the tissue or the surrounding CAM with forceps, and use scissors or a scalpel to excise the graft from the CAM carefully. 
	NOTE: The grafts become covered with a second layer of CAM at around day 3 of grafting and eventually become encapsulated. They may also have moved inside the egg by day 6, making it difficult to retrieve them in some cases.</li>
	<li>Analyze the excised tissues by any method appropriate for the given experiment.&#160;In the present study, tissue pieces were fixed in paraformaldehyde, paraffin-embedded and stained with hematoxylin and eosin following the steps outlined below:
	<ol>
		<li>Fix the fragments in 4% paraformaldehyde for 24 h, and embed them in paraffin using an automatic embedding device with the steps mentioned in Table 1.</li>
		<li>Leave the paraffin-embedded blocks overnight at 4&#176;C before cutting them into 5 &#181;m thick sections with a microtome.</li>
		<li>Spread the tissue sections on a glass slide placed on a hot plate (30 &#176;C), and leave them to dry for 2 h, followed by 24 h in an oven at 37 &#176;C.</li>
		<li>Afterwards, stain the slides with hematoxylin and eosin following a protocol described elsewhere31. Subsequently, digitize the samples using a slide scanner, and analyze them using an image analysis software.</li>
	</ol>
	</li>
</ol>

The authors have nothing to disclose.

The most challenging part of the protocol described here is making the small hole required to aspirate the albumen in order to detach the CAM from the eggshell prior to creating a window. Applying too much pressure can result in overpenetration or may even crack and destroy the egg, causing irrevocable damage to the CAM and its vasculature. To keep mistakes to a minimum during initial attempts to separate the CAM, it is strongly advised to practice making small holes in the eggshell of non-fertilized, grocery-bought eggs...

The demand for fertility preservation for oncological and benign indications, as well as social reasons, has dramatically increased over recent decades. However, various treatments used to cure malignant and non-malignant diseases are highly toxic to the gonads and can result in iatrogenic premature ovarian insufficiency, ultimately leading to infertility1. Established techniques for fertility preservation include embryo cryopreservation, immature or mature oocyte vitrification, and ovarian tissue cryopreservation2,3,4. Ovarian tissue freezing is the only available option for preserving fertility in prepubertal girls or women who require immediate cancer therapy. The restoration of endocrine function following ovarian tissue transplantation occurs in over 95% of subjects, with live birth rates ranging from 18% to 42%5,6,7,8,9.
Although the transplantation of frozen-thawed ovarian tissue has proven successful, there is still room for improvement. Indeed, as ovarian cortical fragments are transplanted without vascular anastomosis, they experience a period of hypoxia during which graft revascularization takes place10,11,12. The vast majority of studies investigating human ovarian tissue transplantation have used a xenografting model, in which ovarian tissue is transplanted to immunodeficient mice. The complete revascularization of the xenografts takes around 10 days, with both the host and graft vessels contributing to the formation of functional vessels12,13,14. Around 50%-90% of the follicle reserve is lost during this hypoxic window before the completion of graft revascularization10,15,16. It has been strongly suggested that this massive follicle loss occurs through both direct follicle death, as demonstrated by a decrease in the absolute follicle numbers left after grafting, and the activation of primordial follicle growth, as indicated by changes in follicle proportions towards increased rates of growing follicles17,18.
Interestingly, previous research works using various animal ovarian tissues grafted to chick chorioallantoic membrane (CAM), which has a constitution mimicking the typical grafting site of the peritoneum, have reported the inhibition of spontaneous follicle activation, with the primordial follicle reserve staying intact for up to 10 days19,20,21,22. Our team&#160;previously demonstrated that the grafting of frozen-thawed human ovarian tissue to CAM constituted a reliable approach for investigating human ovarian tissue transplantation in its first ischemic stages23&#160;and recently showed that this grafting method was able to counteract follicle activation24.
The CAM model is especially appealing not only because eggs are much cheaper than mice but also because of the highly vascularized nature of CAM, allowing scrutiny of the association between follicle activation and ovarian graft revascularization. The avian system is, indeed, one of the most common and versatile ways of studying angiogenesis25. Chick embryo development (ED) takes 21 days until hatching, and the CAM is formed within the first 4-5 days through the fusion of the allantois and chorion26. Notably, the chick embryo is a naturally immunodeficient host until day 17 of ED, so xenografting experiments can be performed without any risk of graft rejection27,28. Moreover, the CAM model approach does not raise any ethical or legal concerns in terms of European law29, making it an attractive alternative to other animal models. With regard to breeding conditions, chick embryos only need an incubator set at 37 &#176;C with a relative air humidity of 40%-60%. These limited experimentation requirements significantly reduce the research costs compared to use of immunodeficient mice.
The protocol presented herein aims to describe the development of a CAM xenografting model for human ovarian tissue and provide specific insights into the effectiveness of the technique, the time frame of graft revascularization, and the tissue viability over a 6 day grafting period. This protocol could be of great interest for investigating the mechanisms behind early post-grafting follicle loss and studying the impact of several agents (growth factors, hormones, etc.) on this phenomenon.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Agani hypodermic needle, 19 G</td>
			<td>Terumo Europe</td>
			<td>AN*1950R1</td>
			<td>19 G needle to aspirate albumen</td>
		</tr>
		<tr>
			<td>Terumo syringe, 5 mL concentric Luer lock</td>
			<td>Terumo Europe</td>
			<td>SS*05LE1</td>
			<td>5-mL sterile syringe</td>
		</tr>
		<tr>
			<td>Caseviewer v2.2</td>
			<td>3DHISTECH</td>
			<td></td>
			<td>Image analysis software</td>
		</tr>
		<tr>
			<td>Diethyl ether</td>
			<td>Merck Chemicals</td>
			<td>603-022-00-4</td>
			<td>Sterile ether to traumatize the CAM</td>
		</tr>
		<tr>
			<td>Eosin Y aqueous solution 0.5%</td>
			<td>Merck</td>
			<td>1098441000</td>
			<td>Staining solution</td>
		</tr>
		<tr>
			<td>Formaldehyde 4% aqueous solution buffered (Formalin 10%)</td>
			<td>VWR</td>
			<td>97139010</td>
			<td>Formaldehyde used for tissue fixation</td>
		</tr>
		<tr>
			<td>Fridge</td>
			<td>Liebherr</td>
			<td>7081260</td>
			<td>Fridge at 4 &#176;C used for paraffin-embedding</td>
		</tr>
		<tr>
			<td>Heating plate</td>
			<td>Schott</td>
			<td>SLK2</td>
			<td>Hot plate used to dry the slides</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Thermo Forma Scientific 3111</td>
			<td>10365156</td>
			<td>Oven used for slide incubation</td>
		</tr>
		<tr>
			<td>Leica CLS 150 XE microscope cold light source</td>
			<td>Leica</td>
			<td>CLS 150 XE</td>
			<td>Focal cold light source to candle the eggs</td>
		</tr>
		<tr>
			<td>Lens cleaning tissue, grade 541</td>
			<td>VWR</td>
			<td>111-5003</td>
			<td>Tissue to soak in sterile ether to traumatize the CAM</td>
		</tr>
		<tr>
			<td>Mayer&#39;s hematoxylin</td>
			<td>MERCK</td>
			<td>1092491000</td>
			<td>Staining solution</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>VWR</td>
			<td>20847307</td>
			<td>Methanol</td>
		</tr>
		<tr>
			<td>Microtome</td>
			<td>ThermoScientific-MICROM</td>
			<td>HM325-2</td>
			<td>Microtome</td>
		</tr>
		<tr>
			<td>Pannoramic P250 Flash III</td>
			<td>3DHISTECH</td>
			<td>/</td>
			<td>Slide scanner at 20x magnification</td>
		</tr>
		<tr>
			<td>Paraformaldehyde&#160;</td>
			<td>Merck</td>
			<td>1,04,00,51,000</td>
			<td>Paraffin-embedding solution</td>
		</tr>
		<tr>
			<td>Paraplast Plus R</td>
			<td>Sigma</td>
			<td>P3683-1KG</td>
			<td>Paraffin</td>
		</tr>
		<tr>
			<td>Petri dish, 60x15 mm, sterile</td>
			<td>Greiner</td>
			<td>628161</td>
			<td>Sterile petri dish</td>
		</tr>
		<tr>
			<td>Pin holder</td>
			<td>Fine Science Tools</td>
			<td>26016-12</td>
			<td>Pin holder</td>
		</tr>
		<tr>
			<td>Polyhatch</td>
			<td>Brinsea</td>
			<td>CP01F</td>
			<td>Egg incubator with automatic rotator</td>
		</tr>
		<tr>
			<td>Scroll saw blade, 132 mm</td>
			<td>Sencys</td>
			<td>/</td>
			<td>Saw blade to create a window in the eggshell</td>
		</tr>
		<tr>
			<td>Stainless steel insert pins</td>
			<td>Fine Science Tools</td>
			<td>26007-02</td>
			<td>Straight pin to make a hole in the eggshell</td>
		</tr>
		<tr>
			<td>Steril-Helios&#160;</td>
			<td>Angelantoni Industrie</td>
			<td>ST-00275400000</td>
			<td>Laminar flow hood</td>
		</tr>
		<tr>
			<td>Superfrost Plus bords rod&#233;s 90&#176;</td>
			<td>VWR</td>
			<td>631-9483</td>
			<td>Glass slides&#160;</td>
		</tr>
		<tr>
			<td>Tissue-Tek VIP 6Al</td>
			<td>Sakura</td>
			<td>60320417-0711 VID6E3-1</td>
			<td>Automatic embedding device</td>
		</tr>
		<tr>
			<td>Titanium forceps</td>
			<td>Fine Science Tools</td>
			<td>11602-16</td>
			<td>Forceps for eggshell removal and ovarian tissue manipulation</td>
		</tr>
		<tr>
			<td>Toluene, pa</td>
			<td>VWR</td>
			<td>28701364</td>
			<td>Paraffin-embedding solution</td>
		</tr>
	</tbody>
</table>

the chick chorioallantoic membrane (cam) model as a tool to study ovarian tissue transplantation

Ovarian tissue cryopreservation and transplantation is an effective strategy for preserving fertility but has one major drawback, namely massive follicle loss occurring shortly after reimplantation due to abnormal follicle activation and death. Rodents are benchmark models for investigating follicle activation, but the cost, time, and ethical considerations are becoming increasingly prohibitive, thus driving the development of alternatives. The chick chorioallantoic membrane (CAM) model is particularly attractive, being inexpensive and maintaining&#160;natural immunodeficiency up to day 17 postfertilization, making it ideal to study&#160;short-term xenografting of human ovarian tissue. The CAM is also highly vascularized and has been widely used as a model to explore angiogenesis. This gives it a remarkable advantage over in vitro models and allows the investigation of mechanisms affecting the early post-grafting follicle loss process. The protocol outlined herein aims to describe the development of a CAM xenografting model for human ovarian tissue, with specific insights into the effectiveness of the technique, the graft revascularization time frame, and the tissue viability across a 6 day grafting period.

Chick embryo survival rates 
The embryo survival rate from windowing (day 3 of&#160;ED) to ovarian tissue grafting (day 7 of ED) was 79% (33/42). Since the percentage of embryonated day 0 eggs is unknown, supernumerary day 0 eggs from Lohman-selected white Leghorn chickens were ordered to ensure sufficient embryonated eggs would be available for grafting. A total of 23 viable day 7 eggs were used for grafting, one of which perished during the first 24 h, resulting in an overall embryo survival rate ...

Watch this Scientific Journal Video about The Chick Chorioallantoic Membrane CAM Model as a Tool to Study Ovarian Tissue Transplantation at JoVE.com

The Chick Chorioallantoic Membrane CAM Model as a Tool to Study Ovarian Tissue Transplantation

Here, we describe a protocol for developing a chick chorioallantoic membrane (CAM) xenografting model for human ovarian tissue and demonstrate the effectiveness of the technique, the graft revascularization time frame, and the tissue viability across a 6 day grafting period.

The Chick Chorioallantoic Membrane (CAM) Model as a Tool to Study Ovarian Tissue Transplantation

Ovarian tissue cryopreservation and transplantation is an effective strategy for preserving fertility but has one major drawback, namely massive follicle ...

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648 Views.  Université Catholique de Louvain. Here, we describe a protocol for developing a chick chorioallantoic membrane (CAM) xenografting model for human ovarian tissue and demonstrate the effectiveness of the technique, the graft revascularization time frame, and the tissue viability across a 6 day grafting period. 

Video: The Chick Chorioallantoic Membrane CAM Model as a Tool to Study Ovarian Tissue Transplantation

Computer-Generated Animal Model Stimuli

Communication between animals is diverse and complex. Animals may communicate using auditory, seismic, chemosensory, electrical, or visual signals. In particular, understanding the constraints on visual signal design for communication has been of great interest. Traditional methods for investigating animal interactions have used basic observational techniques, staged encounters, or physical manipulation of morphology. Less intrusive methods have tried to simulate conspecifics using crude playback tools, such as mirrors, still images, or models. As technology has become more advanced, video playback has emerged as another tool in which to examine visual communication (Rosenthal, 2000). However, to move one step further, the application of computer-animation now allows researchers to specifically isolate critical components necessary to elicit social responses from conspecifics, and manipulate these features to control interactions. Here, I provide detail on how to create an animation using the Jacky dragon as a model, but this process may be adaptable for other species. In building the animation, I elected to use Lightwave  3D to alter object morphology, add texture, install bones, and provide comparable weight shading that prevents exaggerated movement. The animation is then matched to select motor patterns to replicate critical movement features. Finally, the sequence must rendered into an individual clip for presentation. Although there are other adaptable techniques, this particular method had been demonstrated to be effective in eliciting both conspicuous and social responses in staged interactions.

Computer-generated stimuli using the Jacky dragon as a model.

Communication between animals is diverse and complex. Animals may communicate using auditory, seismic, chemosensory, electrical, or visual signals. In ...

Heterotopic and Orthotopic Tracheal Transplantation in Mice used as Models to Study the Development of  Obliterative Airway Disease

Obliterative airway disease (OAD) is the major complication after lung transplantations that limits long term survival (1-7).
To study the pathophysiology, treatment and prevention of OAD, different animal models of tracheal transplantation in rodents have been developed (1-7). Here, we use two established models of trachea transplantation, the heterotopic and orthotopic model and demonstrate their advantages and limitations.
For the heterotopic model, the donor trachea is wrapped into the greater omentum of the recipient, whereas the donor trachea is anastomosed by end-to-end anastomosis in the orthotopic model.
In both models, the development of obliterative lesions histological similar to clinical OAD has been demonstrated (1-7).
This video shows how to perform both, the heterotopic as well as the orthotopic tracheal transplantation technique in mice, and compares the time course of OAD development in both models using histology.

This video shows and compares two experimental models to study the development of obliterative airway disease (OAD) in mice, the heterotopic and orthotopic tracheal transplantation model.

Obliterative airway disease (OAD) is the major complication after lung transplantations that limits long term survival (1-7).
To study the ...

Chick ex ovo Culture and ex ovo CAM Assay: How it Really Works

Chicken eggs in the early phase of breeding are between in vitro and in vivo systems and provide a vascular test environment not only to study angiogenesis but also to study tumorigenesis. After the chick chorioallantoic membrane (CAM) has developed, its blood vessel network can be easily accessed, manipulated and observed and therefore provides an optimal setting for angiogenesis assays. Since the lymphoid system is not fully developed until late stages of incubation, the chick embryo serves as a naturally immunodeficient host capable of sustaining grafted tissues and cells without species-specific restrictions. In addition to nurturing developing allo- and xenografts, the CAM blood vessel network provides a uniquely supportive environment for tumor cell intravasation, dissemination, and vascular arrest and a repository where arrested cells extravasate to form micro metastatic foci.
For experimental purposes, in most of the recent studies the CAM was exposed by cutting a window through the egg shell and experiments were carried out in ovo, resulting in significant limitations in the accessibility of the CAM and possibilities for observation and photo documentation of effects. When shell-less cultures of the chick embryo were used1-4, no experimental details were provided and, if published at all, the survival rates of these cultures were low. We refined the method of ex ovo culture of chick embryos significantly by introducing a rationally controlled extrusion of the egg content. These ex ovo cultures enhance the accessibility of the CAM and chick embryo, enabling easy in vivo documentation of effects and facilitating experimental manipulation of the embryo. This allows the successful application to a large number of scientific questions: (1) As an improved angiogenesis assay5,6, (2) an experimental set up for facilitated injections in the vitreous of the chick embryo eye7-9, (3) as a test environment for dissemination and intravasation of dispersed tumor cells from established cell lines inoculated on the CAM10-12, (4) as an improved sustaining system for successful transplantation and culture of limb buds of chicken and mice13 as well as (5) for grafting, propagation, and re-grafting of solid primary tumor tissue obtained from biopsies on the surface of the CAM14.
In this video article we describe the establishment of a refined chick ex ovo culture and CAM assay with survival rates over 50%. Besides we provide a step by step demonstration of the successful application of the ex ovo culture for a large number of scientific applications. 
Daniel S. Dohle, Susanne D. Pasa, and Sebastian Gustmann contributed equally to this study.

Chick ex ovo Culture and ex ovo CAM Assay: How it Really Works

The chick chorioallantoic membrane (CAM) is a unique, naturally immunodeficient supportive culture environment to study angiogenesis and tumorigenesis. This video article demonstrates the different steps in chick ex ovo culture, application of potentially angiogenic substances and successful inoculation of tumor cells and tissues on the surface of the CAM.

Chicken eggs in the early phase of breeding are between in vitro and in vivo systems and provide a vascular test environment not only to study ...

A System for Culturing Iris Pigment Epithelial Cells to Study Lens Regeneration in Newt

Salamanders like newt and axolotl possess the ability to regenerate many of its lost body parts such as limbs, the tail with spinal cord, eye, brain, heart, the jaw 1. Specifically, newts are unique for its lens regeneration capability. Upon lens removal, IPE cells of the dorsal iris transdifferentiate to lens cells and eventually form a new lens in about a month 2,3. This property of regeneration is never exhibited by the ventral iris cells. The regeneration potential of the iris cells can be studied by making transplants of the in vitro cultured IPE cells. For the culture, the dorsal and ventral iris cells are first isolated from the eye and cultured separately for a time period of 2 weeks (Figure 1). These cultured cells are reaggregated and implanted back to the newt eye. Past studies have shown that the dorsal reaggregate maintains its lens forming capacity whereas the ventral aggregate does not form a lens, recapitulating, thus the in vivo process (Figure 2) 4,5. This system of determining regeneration potential of dorsal and ventral iris cells is very useful in studying the role of genes and proteins involved in lens regeneration.

In newt, the lens regenerates always from the dorsal iris by transdifferentiation of the iris pigmented epithelial cells (IPEs). Here we describe a procedure to culture dorsal and ventral newt IPE cells and their implantation to the newt eye. The implanted cells are then studied by tissue sectioning and immunohistochemistry.

Salamanders like newt and axolotl possess the ability to regenerate many of its lost body parts such as limbs, the tail with spinal cord, eye, brain, ...

Tracking Morphogenetic Tissue Deformations in the Early Chick Embryo

Embryonic epithelia undergo complex deformations (e.g. bending, twisting, folding, and stretching) to form the primitive organs of the early embryo. Tracking fiducial markers on the surfaces of these cellular sheets is a well-established method for estimating morphogenetic quantities such as growth, contraction, and shear. However, not all surface labeling techniques are readily adaptable to conventional imaging modalities and possess different advantages and limitations. Here, we describe two labeling methods and illustrate the utility of each technique. In the first method, hundreds of fluorescent labels are applied simultaneously to the embryo using magnetic iron particles. These labels are then used to quantity 2-D tissue deformations during morphogenesis. In the second method, polystyrene microspheres are used as contrast agents in non-invasive optical coherence tomography (OCT) imaging to track 3-D tissue deformations. These techniques have been successfully implemented in our lab to studythe physical mechanisms of early head fold, heart, and brain development, and should be adaptable to a wide range morphogenetic processes.

This article describes surface labeling and ex ovo tissue culture in the early chick embryo. Techniques amenable to time-lapse bright field, fluorescence, and optical coherence tomography imaging are presented. Tracking surface labels with high spatiotemporal resolution enables kinematic quantities such as morphogenetic strains (deformations) to be calculated in both two and three dimensions.

Embryonic epithelia undergo complex deformations (e.g. bending, twisting, folding, and stretching) to form the primitive organs of the early embryo. ...

Using SecM Arrest Sequence as a Tool to Isolate Ribosome Bound Polypeptides

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway that polypeptide chain follows during co-translational folding to achieve its functional form is still an enigma. In order to understand this process and to determine the exact conformation of the co-translational folding intermediates, it is essential to develop techniques that allow the isolation of RNCs carrying nascent chains of predetermined sizes to allow their further structural analysis.
SecM (secretion monitor) is a 170 amino acid E. coli protein that regulates expression of the downstream SecA (secretion driving) ATPase in the secM-secA operon6. Nakatogawa and Ito originally found that a 17 amino acid long sequence (150-FSTPVWISQAQGIRAGP-166) in the C-terminal region of the SecM protein is sufficient and necessary to cause stalling of SecM elongation at Gly165, thereby producing peptidyl-glycyl-tRNA stably bound to the ribosomal P-site7-9. More importantly, it was found that this 17 amino acid long sequence can be fused to the C-terminus of virtually any full-length and/or truncated protein thus allowing the production of RNCs carrying nascent chains of predetermined sizes7. Thus, when fused or inserted into the target protein, SecM stalling sequence produces arrest of the polypeptide chain elongation and generates stable RNCs both in vivo in E. coli cells and in vitro in a cell-free system. Sucrose gradient centrifugation is further utilized to isolate RNCs.
The isolated RNCs can be used to analyze structural and functional features of the co-translational folding intermediates. Recently, this technique has been successfully used to gain insights into the structure of several ribosome bound nascent chains10,11. Here we describe the isolation of bovine Gamma-B Crystallin RNCs fused to SecM and generated in an in vitro translation system.

We describe here a technique that is now routinely used to isolate stably bound ribosome nascent chain complexes (RNCs). This technique takes advantage of the discovery that a 17 amino acid long SecM "arrest sequence" can halt translation elongation in a prokaryotic (E. coli) system, when inserted into (or fused to the C-terminus) of virtually any protein.

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway ...

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.

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.

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

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 ...

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the function and regulation of protein folding was studied in vitro, in isolated tissue culture cells and in unicellular organisms. Recent studies have uncovered links between protein homeostasis (proteostasis), metabolism, development, aging, and temperature-sensing. These findings have led to the development of new tools for monitoring protein folding in the model metazoan organism Caenorhabditis elegans. In our laboratory, we combine behavioral assays, imaging and biochemical approaches using temperature-sensitive or naturally occurring metastable proteins as sensors of the folding environment to monitor protein misfolding. Behavioral assays that are associated with the misfolding of a specific protein provide a simple and powerful readout for protein folding, allowing for the fast screening of genes and conditions that modulate folding. Likewise, such misfolding can be associated with protein mislocalization in the cell. Monitoring protein localization can, therefore, highlight changes in cellular folding capacity occurring in different tissues, at various stages of development and in the face of changing conditions. Finally, using biochemical tools ex vivo, we can directly monitor protein stability and conformation. Thus, by combining behavioral assays, imaging and biochemical techniques, we are able to monitor protein misfolding at the resolution of the organism, the cell, and the protein, respectively.

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

To study the relationship between protein homeostasis, stress and aging, we monitored changes in protein folding by following protein dysfunction, protein localization in the cell and protein stability at the organismal, cellular and protein levels, using the genetically tractable metazoan Caenorhabditis elegans as a model system.

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

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 ...