This work was supported by the Deutsche Forschungsgemeinschaft SFB688 (to A.G.).

Mouse breeding was approved by the Regierung Unterfranken, and all analyses were carried out in strict accordance with all German and European Union applicable laws and regulations concerning care and use of laboratory animals.
1. Coating of Microtiter Plates with &#945;4&#946;1 Integrin for Ex Utero Allantois Explant Culture
<ol>
	<li>Reconstitute the lyophilized murine &#945;4&#946;1 integrin at 200 &#181;g/mL in sterile phosphate-buffered saline (PBS). Dilute to a final concentration of 10 &#181;g/mL in pre-warmed (37 &#176;C) PBS. Pipette 20 &#181;L/well of the diluted &#945;4&#946;1 integrin solution into the required number of wells of a microtiter plate (1 allantois/well). 
	NOTE: Avoid the formation of air bubbles when coating the wells of the microtiter plate.</li>
	<li>Incubate the microtiter plates for 60 min at 37 &#176;C by placing them in a humidified tissue culture incubator.</li>
	<li>Carefully aspirate the supernatant with a pipette. Use gentle suction and incline the plate to avoid touching the well bottom with the pipette tip. Wash wells twice by adding 50 &#181;L of pre-warmed (37 &#176;C) culture medium such as Dulbecco&#39;s Modified Eagle Medium (DMEM), and remove the washing medium by gentle suction.</li>
	<li>Critical step: Block free binding sites by adding 50 &#181;L/well of 0.1% (w/v) bovine serum albumin (BSA)/DMEM and incubate for &#8805; 30 min at 37 &#176;C by placing the microtiter plates in a humidified tissue culture incubator. 
	NOTE: Allantois explants can attach to various surfaces in the presence of serum. It is therefore imperative to block non-specific binding sites, after coating the wells with integrin, and before adding the dissected allantois for explant culture in serum-containing medium (see step 4.4).</li>
	<li>Keep the coated wells in the blocking solution at 37 &#176;C until needed in step 4.4.</li>
</ol>
2. Uterus Dissection from a Pregnant Mouse at Dpc 8
NOTE: Reduce false-positive pregnancy rates by weight gain discrimination15.
<ol>
	<li>Sacrifice the mouse by cervical dislocation. Disinfect the coat in the abdominal area by spraying it with 70% (v/v) ethanol. 
	NOTE: Wear gloves when handling mice. Euthanasia by cervical dislocation without anesthetics prevents chemical contamination of the allantois, which may interfere with allantois attachment.</li>
	<li>Open the abdominal skin by making a small incision at the midline with scissors. Use gloved fingers to hold the skin above and below the incision, and pull the skin apart towards the chest and tail of the mouse.</li>
	<li>Grasp the peritoneum with forceps. With the other hand, make a V-shaped incision from anterior towards posterior using scissors, and move the tissue away to expose the abdominal cavity. Use the forceps to push the intestines to one side in order to gain access to the uterus.</li>
	<li>Locate the two uterine horns. Hold the cervix (the caudal segment) with forceps and cut the ligaments with fine scissors. Then detach both uterine horns by severing the oviducts with&#160;scissors.</li>
	<li>Use forceps to transfer the uterus into a sterile 10 cm dish containing sterile, room temperature (RT) PBS. Remove the adipose tissue, vessels, and nerves surrounding the uterine horns with fine forceps and/or scissors (Figure 1A).</li>
</ol>
3. Embryo Dissection
NOTE: Perform the following steps under a stereomicroscope equipped with an 8:1 zoom range.
<ol>
	<li>Separate the embryos by cutting in between the implantation sites with scissors. Grasp the muscular uterine lining of the uterus buds with forceps and pull it apart to expose the decidua (Figure 1B).</li>
	<li>Using forceps, transfer the uterus buds into a new 10 cm dish containing sterile, RT PBS.</li>
	<li>Fix the decidua around the embryo with the tips of forceps.</li>
	<li>Make an incision on the anti-mesometrial side of the decidua with fine forceps&#160;(Figure 1C), and peel the decidua away with forceps to expose the embryo (Figure 1D). 
	NOTE: The mesometrial pole of the decidua is highly vascularized and can be wider at its base than the anti-mesometrial part, which contains the embryo and appears paler.</li>
	<li>Dissect the embryo with forceps (Figure 1E, F).</li>
	<li>Using a micro-spoon, transfer the embryo into a drop of sterile PBS contained in a sterile 3.5 cm dish.</li>
	<li>Transfer the embryo into a fresh drop of PBS in the same 3.5 cm dish using a micro-spoon, and dissect the embryo from the yolk sac using forceps (Figure 1G, H).</li>
	<li>Optionally, if needed (e.g., for genotyping by polymerase chain reaction), transfer the yolk sac into a sterile tube by aspirating it with ~ 5 &#181;L PBS into a large orifice 200 &#181;L pipette tip. Store at -20 &#176;C. 
	NOTE: Maternal tissue (i.e., the parietal yolk sac including Reichert&#39;s membrane and the ectoplacental cone) that may contaminate the yolk sac preparation can lead to erroneous genotyping results. Removal of these tissues is easiest prior to the embryo dissection from the yolk sac.</li>
</ol>
4. Allantois Dissection and Ex Utero Culture on Immobilized &#945;4&#946;1 Integrin
<ol>
	<li>Cut the allantois from its basal insertion site at the posterior end of the embryo using fine forceps (Figure 1H).</li>
	<li>Optionally, if developmental staging is required, count the somite pairs of the embryo by visual inspection using a microscope equipped with phase contrast optics and a 5&#215; and 10&#215; objective. 
	NOTE: The embryo can be extended with forceps to facilitate somite counting. Chorioallantoic attachment and fusion occur between E 8.0 and E 9.0 in embryos with &#8805; 6 somite pairs. Turning begins in embryos with 6-8 somite pairs.</li>
	<li>Pipette 40 &#181;L/well of DMEM supplemented with 10% (v/v) fetal bovine serum, L-glutamine, and antibiotics in the required number of pre-coated microtiter plate wells (see Section 1).</li>
	<li>Collect the floating allantois by aspirating it with ~ 5 &#181;L PBS into a large orifice of a 200 &#181;L pipette tip. Transfer 1 allantois/well.</li>
	<li>Incubate the allantoides by placing the microtiter plates in a humidified tissue culture incubator (37 &#176;C, 5% CO2) for e.g., 6, 12, and 24 h. In order to prevent interference with allantois attachment, do not move the microtiter plates in between these time points.</li>
	<li>At each time point, score allantois attachment (e.g., no attachment/floating allantois; partially or fully attached allantois; fully spread allantois) using a microscope equipped with phase contrast or differential interference contrast optics and a 5&#215; or 10&#215; objective (Figure 2). 
	NOTE: Representative examples of freshly isolated and fully attached allantoides are shown in Figure 2. Ex utero, the distal tip of allantoides isolated from wildtype C57BL/6J mice attaches within 4-6 h (this is referred to as partial attachment of the allantois), and full attachment of the entire allantois is achieved within ~ 12 h of culture. By 18-24 h, the explant has flattened and assumed a circular shape (referred to as fully spread allantois) with a CD31-positive vascular plexus9,16.</li>
</ol>
5. Confirmatory Staining of the Explanted Allantois for the Endothelial Cell Marker CD31
<ol>
	<li>Aspirate the culture medium of fully spread explants and fix the cells by adding 40 &#181;L/well of 4% (w/v) paraformaldehyde/PBS. 
	NOTE: Paraformaldehyde is toxic. Wear gloves and safety goggles to avoid skin and eye contact.</li>
	<li>Incubate for 10 min at RT, then aspirate the supernatant. Wash three times by adding 40 &#181;L/well of PBS, and remove the washing medium by gentle suction.</li>
	<li>Permeabilize the cells and block non-specific binding sites by adding 40 &#181;L/well of 0.1% (v/v) Triton X-100/0.1% (w/v) BSA/10% (v/v) normal goat serum in PBS for 30 min at RT. Wash twice by adding 40 &#181;L/well of PBS, and remove the washing medium by gentle suction. 
	NOTE: The protocol can be paused overnight at this point.</li>
	<li>Stain cells by adding 20 &#181;L/well of primary anti-CD31 antibodies diluted 1:50 in 0.1% (w/v) BSA/PBS overnight at 4 &#176;C. Wash three times by adding 40 &#181;L/well of PBS, and remove the washing medium by gentle suction.</li>
	<li>Detect bound primary antibodies by adding 20 &#181;L/well of fluorescently-labeled secondary goat anti-rat antibodies diluted 1:200 in 0.1% (w/v) BSA/PBS for 1 h at RT. Protect microtiter plates from light by wrapping in aluminum foil or by placing in a dark chamber. Wash three times by adding 40 &#181;L/well of PBS, and remove the washing medium by gentle suction.</li>
	<li>Embed cells by adding 20 &#181;L/well of mounting medium. Incubate for ~ 1 h at RT until the mounting medium has solidified. Store microtiter plates at RT or at 4 &#176;C, protected from light.</li>
	<li>Image the vascular plexus of the allantois explants under a fluorescence microscope equipped with a 5&#215; or 10&#215; objective and suitable fluorescence filters. 
	NOTE: Representative images of the CD31-positive vascular plexus of a fully spread allantois are shown in Figure 3. Other markers for the vascular plexus, such as antibodies directed against Flk-1, Flt, Tie-1 or Tie-2 can be used as well16.</li>
</ol>

<ol>
	<li>Rossant, J., Cross, 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=Placental+development:+lessons+from+mouse+mutants.">Placental development: lessons from mouse mutants.</a> Nat Rev Genet. 2 (7), 538-548 (2001).</li><li>Segerer, G., 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=An+essential+developmental+function+for+murine+phosphoglycolate+phosphatase+in+safeguarding+cell+proliferation.">An essential developmental function for murine phosphoglycolate phosphatase in safeguarding cell proliferation.</a> Sci Rep. 6, 35160 (2016).</li><li>Kane, S. V., Acquah, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Placental+transport+of+immunoglobulins:+a+clinical+review+for+gastroenterologists+who+prescribe+therapeutic+monoclonal+antibodies+to+women+during+conception+and+pregnancy.">Placental transport of immunoglobulins: a clinical review for gastroenterologists who prescribe therapeutic monoclonal antibodies to women during conception and pregnancy.</a> Am J Gastroenterol. 104 (1), 228-233 (2009).</li><li>Xu, X., Vugmeyster, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+and+opportunities+in+absorption,+distribution,+metabolism,+and+excretion+studies+of+therapeutic+biologics.">Challenges and opportunities in absorption, distribution, metabolism, and excretion studies of therapeutic biologics.</a> AAPS J. 14 (4), 781-791 (2012).</li><li>Wesolowski, S. R., Kasmi, K. C., Jonscher, K. R., Friedman, 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=Developmental+origins+of+NAFLD:+a+womb+with+a+clue.">Developmental origins of NAFLD: a womb with a clue.</a> Nat Rev Gastroenterol Hepatol. 14 (2), 81-96 (2017).</li><li>Racicot, K., Mor, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Risks+associated+with+viral+infections+during+pregnancy.">Risks associated with viral infections during pregnancy.</a> J Clin Invest. 127 (5), 1591-1599 (2017).</li><li>Grandjean, P., 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=Life-Long+Implications+of+Developmental+Exposure+to+Environmental+Stressors:+New+Perspectives.">Life-Long Implications of Developmental Exposure to Environmental Stressors: New Perspectives.</a> Endocrinology. 156 (10), 3408-3415 (2015).</li><li>Inman, K. E., Downs, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+murine+allantois:+emerging+paradigms+in+development+of+the+mammalian+umbilical+cord+and+its+relation+to+the+fetus.">The murine allantois: emerging paradigms in development of the mammalian umbilical cord and its relation to the fetus.</a> Genesis. 45 (5), 237-258 (2007).</li><li>Arora, R., Papaioannou, V. 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+murine+allantois:+a+model+system+for+the+study+of+blood+vessel+formation.">The murine allantois: a model system for the study of blood vessel formation.</a> Blood. 120 (13), 2562-2572 (2012).</li><li>Watson, E. D., Cross, 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=Development+of+structures+and+transport+functions+in+the+mouse+placenta.">Development of structures and transport functions in the mouse placenta.</a> Physiology (Bethesda). 20, 180-193 (2005).</li><li>Yang, J. T., Rayburn, H., Hynes, R. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+adhesion+events+mediated+by+alpha+4+integrins+are+essential+in+placental+and+cardiac+development.">Cell adhesion events mediated by alpha 4 integrins are essential in placental and cardiac development.</a> Development. 121 (2), 549-560 (1995).</li><li>Gurtner, G. C., 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=Targeted+disruption+of+the+murine+VCAM1+gene:+essential+role+of+VCAM-1+in+chorioallantoic+fusion+and+placentation.">Targeted disruption of the murine VCAM1 gene: essential role of VCAM-1 in chorioallantoic fusion and placentation.</a> Genes &amp; development. 9 (1), 1-14 (1995).</li><li>Kwee, 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=Defective+development+of+the+embryonic+and+extraembryonic+circulatory+systems+in+vascular+cell+adhesion+molecule+(VCAM-1)+deficient+mice.">Defective development of the embryonic and extraembryonic circulatory systems in vascular cell adhesion molecule (VCAM-1) deficient mice.</a> Development. 121 (2), 489-503 (1995).</li><li>Downs, K. M., Gardner, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+investigation+into+early+placental+ontogeny:+allantoic+attachment+to+the+chorion+is+selective+and+developmentally+regulated.">An investigation into early placental ontogeny: allantoic attachment to the chorion is selective and developmentally regulated.</a> Development. 121 (2), 407-416 (1995).</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> J Am Assoc Lab Anim Sci. 54 (4), 368-371 (2015).</li><li>Downs, K. M., Temkin, R., Gifford, S., McHugh, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+the+murine+allantois+by+allantoic+explants.">Study of the murine allantois by allantoic explants.</a> Dev Biol. 233 (2), 347-364 (2001).</li><li>Hou, W., Sarikaya, D. P., Jerome-Majewska, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+culture+of+pre-placental+tissues+reveals+that+the+allantois+is+required+for+maintained+expression+of+Gcm1+and+Tpbpalpha.">Ex vivo culture of pre-placental tissues reveals that the allantois is required for maintained expression of Gcm1 and Tpbpalpha.</a> Placenta. 47, 12-23 (2016).</li><li>Zeigler, B. 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=The+allantois+and+chorion,+when+isolated+before+circulation+or+chorio-allantoic+fusion,+have+hematopoietic+potential.">The allantois and chorion, when isolated before circulation or chorio-allantoic fusion, have hematopoietic potential.</a> Development. 133 (21), 4183-4192 (2006).</li><li>Zaidel-Bar, R., Itzkovitz, S., Ma'ayan, A., Iyengar, R., Geiger, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+atlas+of+the+integrin+adhesome.">Functional atlas of the integrin adhesome.</a> Nature cell biology. 9 (8), 858-867 (2007).</li></ol>

The authors have nothing to disclose.

In the presence of serum, which is a rich source of pro-adhesive extracellular matrix molecules such as fibronectin, allantois explants will readily attach to various plastic, glass, or filter surfaces9,16. Thus, if the aim of the performed assay is to specifically investigate the effect of a genetic modification or any other treatment on allantois attachment to immobilized &#945;4&#946;1, it is critical to block non-specific binding sites (e.g., with bo...

The placenta is indispensable for embryonic growth and development in the uterine environment. It constitutes the interface for oxygen, metabolite, and nutrient exchange between the fetal and maternal circulation, and also functions as an endocrine and immunological organ. Any endogenous or exogenous insult that impairs placental development can lead to intrauterine growth retardation, fetal loss, or pregnancy complications, both in mice and in humans1.While the number of targeted mouse mutations that cause abnormal placental physiology continues to increase2, with 219 genotypes currently listed on the Mouse Genome Informatics (MGI) website (http://www.informatics.jax.org/vocab/ mp_ontology/MP:0010038), many of these phenotypes are not well understood from a mechanistic point of view. In addition to genetic alterations, small molecule drugs, monoclonal antibodies, toxins, pathogens, excess metabolites, or various environmental agents may affect placenta development and function3,4,5,6,7. Yet, simple in vitro assays that model critical steps in placenta development are scarce.
Murine placental development is initiated in early midgestation, when the allantois (the developmental precursor of the umbilical cord) emerges from the posterior end of the embryo as a bud that grows toward the chorion8. Chorioadhesive cells in the outer layer of the allantoic bud mediate the attachment and spreading of the allantois on the surface of the chorion (chorioallantoic &#34;fusion&#34;). The chorion subsequently folds into villi into which the vasculature of the allantois grows to form the labyrinth, the inner placental layer where nutrients and oxygen are exchanged between closely juxtaposed maternal blood sinusoids and embryonic vessels9,10.
The attachment of the allantois to the chorion is the initial and critical step in labyrinth formation, and defects in this process are among the most common causes of embryonic lethality in midgestation1. Although a number of mouse mutants have been described where chorioallantoic attachment fails to occur10, and the MGI database currently lists 108 mouse mutants that are characterized by abnormal chorioallantoic fusion (http://www.informatics.jax.org/vocab/mp_ontology/MP:0002824), the intercellular interaction between the vascular cell adhesion molecule-1 (VCAM-1, expressed on the allantoic mesoderm) and &#945;4&#946;1 integrin (expressed on the chorionic mesothelium, which is derived from extraembryonic mesoderm) appears to be indispensable for chorioallantoic attachment and fusion11,12,13. Immunohistochemical staining of whole-mount wild-type embryos has shown that VCAM-1 is expressed within the distal two-thirds of the allantoic stalk at approximately embryonic day (E) 7.513 (1-4 somite stage), and that its expression remains high during chorioallantoic attachment and -fusion11,12. Failure of allantoic attachment to the chorion is typically detected by histological analyses of uterus buds. However, allantois sizes are physiologically highly variable in between and even within litters of the same developmental stage14, and the allantois can only attach to the chorion when it has reached a sufficient size to make physical contact. Reflecting this natural variability, chorioallantoic attachment takes place sometime between ~ E 8.0 and E 9.0 in utero, and a statistically reliable evaluation of this process by histology is therefore dependent on the analysis of a large number of conceptuses to obtain enough specimens at the appropriate developmental stage.
Here, we describe a method to assess allantoic attachment ex utero that is less dependent on allantois size. We demonstrate the dissection of mouse embryos and their allantoides from the uteri of pregnant mice ~ 8 days post coitum (dpc; dpc 0.5 designates the detection of a vaginal plug), and the subsequent culture of allantois explants on immobilized &#945;4&#946;1 integrins. This method enables a rapid, functional evaluation of the attachment and spreading behavior of multiple allantois explants in parallel and at different successive time points. The protocol may be used to screen for the effects of targeted mutations, drugs, or various environmental factors on allantois attachment ex vivo.

<table border="0" cellpadding="0" cellspacing="0" width="1607">
	<tbody>
		<tr height="23">
			<td height="23" style="height:23px;width:319px;">C57BL/6J wildtype mice</td>
			<td style="width:256px;">The Jackson Laboratory</td>
			<td style="width:119px;">Stock No:&#160;000664</td>
			<td style="width:915px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">70 % (v/v) Ethanol</td>
			<td style="width:256px;">VWR International</td>
			<td>930031006</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Standard pattern forceps</td>
			<td style="width:256px;">Fine Science Tools</td>
			<td>11000-12</td>
			<td style="width:915px;">Forceps used to open the abdominal cavity.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Micro dissecting forceps</td>
			<td style="width:256px;">Fine Science Tools</td>
			<td style="width:119px;">11254-20</td>
			<td>Dumont # 5 medical biology forcepts with fine, sharp tip.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Fine scissors&#160;</td>
			<td style="width:256px;">Fine Science Tools</td>
			<td>14094-11</td>
			<td>Straight blades.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Spring scissors&#160;</td>
			<td style="width:256px;">Fine Science Tools</td>
			<td>15012-12</td>
			<td>Noyes spring scissors with 14 mm blades for the dissection of uterus buds.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Microspoon</td>
			<td style="width:256px;">Carl Roth</td>
			<td>AT18.1</td>
			<td>5 mm Spoon diameter.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Microtiter plates</td>
			<td style="width:256px;">ibidi</td>
			<td style="width:119px;">81501</td>
			<td>We use uncoated, sterile angiogenesis slides (internal volume 50 &#181;L) with a hydrophobic surface that is not tissue-culture treated to reduce non-a4b1-mediated binding to plastic.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">10 cm dish</td>
			<td style="width:256px;">Nunc</td>
			<td style="width:119px;">150350</td>
			<td>Sterile tissue culture dishes.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">3.5 cm dish</td>
			<td style="width:256px;">Nunc</td>
			<td style="width:119px;">150288</td>
			<td>Sterile tissue culture dishes.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Large orifice pipette tips&#160;</td>
			<td style="width:256px;">Biozym</td>
			<td style="width:119px;">VT0140X</td>
			<td>Low binding pipette tips, 200 &#181;L.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">a4b1 integrin</td>
			<td style="width:256px;">R&#38;D Systems</td>
			<td style="width:119px;">6054-A4</td>
			<td>Murine a4b1 integrin recombinantly expressed and purified from a Chinese hamster ovary cell line.</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:319px;">Dulbecco&#39;s Phosphate Buffered Saline (PBS)</td>
			<td style="width:256px;">Sigma Aldrich</td>
			<td style="width:119px;">D8537</td>
			<td>Without Ca2+ and Mg2+.</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:319px;">Dulbecco&#8217;s Modified Eagle Medium (DMEM)</td>
			<td style="width:256px;">PAN Biotech</td>
			<td style="width:119px;">P04-03600</td>
			<td style="width:915px;">The formulation contains 4.5 g/L glucose, 110 mg/L sodium pyruvate and 3.7 g/L NaHCO3 but no L-glutamine, which is added separately.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:319px;">Penicillin/Streptomycin</td>
			<td style="width:256px;">Gibco (ThermoFisher Scientific)</td>
			<td style="width:119px;">15140-122</td>
			<td>100 x (10,000 U/mL Penicillin and 10,000 &#181;g/mL streptomycin) stock solution.&#160;Prepare and store aliquots at -20 &#176;C to avoid freeze/thaw.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">L-Glutamine</td>
			<td style="width:256px;">PAN Biotech</td>
			<td style="width:119px;">P04-80100</td>
			<td>100 x (200 mM) Stock solution. Prepare and store aliquots at -20 &#176;C to avoid freeze/thaw.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Fetal bovine serum&#160;</td>
			<td style="width:256px;">Biochrom</td>
			<td style="width:119px;">S 0115</td>
			<td>We use heat-inactivated FBS (heated to 56 &#176;C for 30 min with mixing to inactivate complement).</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Bovine serum albumin (BSA)</td>
			<td style="width:256px;">Sigma Aldrich</td>
			<td style="width:119px;">A7030</td>
			<td>We use protease- and fatty acid-free albumin. Prepare a 0.1 % (w/v) solution in DMEM. Sterile filter the solution through a disposable cell culture filter with a 0.22 &#181;m pore size and low protein-binding membrane, and store aliquots at -20 &#176;C.</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;">para-Formaldehyde</td>
			<td style="width:256px;">Carl Roth</td>
			<td>0335.2</td>
			<td style="width:915px;">To make a formaldehyde solution in PBS, weigh para-formaldehyde powder in a ventilated hood, and add it to PBS preheated to ca. 60 &#176;C in a beaker on a stir plate. Add 1 N NaOH dropwise until solution clears. Let solution cool to room temperature, and filter through 0.22 mm filter syringe. Adjust pH with diluted HCl to ca. 6.9, and adjust to final volume with PBS. We aliquot and freeze the solution, but it can also be stored at 4 &#176;C for approximately four weeks.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Triton X-100</td>
			<td style="width:256px;">Sigma Aldrich</td>
			<td style="width:119px;">X100</td>
			<td>Use wide-orifice pipette tips to handle undiluted Triton X-100.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Normal goat serum</td>
			<td style="width:256px;">Sigma Aldrich</td>
			<td>G9023</td>
			<td>To block non-specific binding of antibodies in immunofluorescence analyses.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">a-CD31 Antibodies</td>
			<td style="width:256px;">BD Biosciences</td>
			<td>550274</td>
			<td>Purified rat anti-mouse monoclonal antibodies, clone MEC 13.3.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Secondary goat anti-rat antibodies</td>
			<td style="width:256px;">Thermo Fisher</td>
			<td>A-11006</td>
			<td>Goat anti-rat IgG (heavy and light chains), cross-adsorbed, fluorescently labeled with Alexa Fluor 488. Other fluorescent labels are also possible.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Mowiol 4-88</td>
			<td style="width:256px;">Sigma Aldrich</td>
			<td>81381</td>
			<td>Mounting medium for cytochemistry. MW ~31,000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Labovert&#160;</td>
			<td style="width:256px;">Leitz</td>
			<td style="width:119px;">Labovert&#160;</td>
			<td>Inverted phase contrast microscope equipped with a 4 x and 10 x objective for somite pair counting. Other phase contrast microscopes (such as those that are routinely used in tissue culture) are also suitable.&#160;&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">M80</td>
			<td style="width:256px;">Leica Microsystems</td>
			<td style="width:119px;">M80</td>
			<td>Stereomicroscope with 8 : 1 zoom range (yielding a magnification between 7.5 x and 60 x) for embryo and allantois dissection.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">DM4000B</td>
			<td style="width:256px;">Leica Microsystems</td>
			<td style="width:119px;">DM4000B</td>
			<td>Microscope system for histology with LED illumination. We use HCX PL FLUOTAR 5 x/0.15 and HC PL FLUOTAR 10 x/0.30 objectives. Other microscopes equipped phase contrast and fluorescence optics can be used to score allantois attachment.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Digital camera</td>
			<td style="width:256px;">JVC</td>
			<td style="width:119px;">KY-F75U</td>
			<td>3-CCD digital capture camera attached to the DM4000B LED microscope. We use Diskus software (Hilgers) to operate both the microscope and the camera.</td>
		</tr>
		<tr height="18">
			<td height="18" style="height:18px;width:319px;">Confocal microscope</td>
			<td style="width:256px;">Leica Microsystems</td>
			<td style="width:119px;">SP5</td>
			<td style="width:915px;">Confocal microscope for higher-resolution imaging of endothelia in the vascular plexus of allantois explants. Immunofluorescence images were taken with a 40 x objective.</td>
		</tr>
	</tbody>
</table>

dissection and explant culture of murine allantois for the in vitro analysis of allantoic attachment

The placenta is essential for the growth and development of mammalian embryos. For this reason, numerous genetic alterations and likely also environmental insults that disturb placenta development or function can cause early pregnancy loss in mice and humans. Nevertheless, simple in vitro assays to screen for potential effects on placenta formation are lacking. Here, we focus on modeling the first and critical step in placenta formation, which consists of the attachment of the allantois to the chorion. We describe a method to rapidly assess the attachment of allantoic explants on immobilized &#945;4&#946;1 integrin, which serves as a chorio-mimetic substrate.This in vitro approach enables a qualitative evaluation of the attachment and spreading behavior of multiple allantois explants at different consecutive time points. The protocol may be used to investigate the effect of targeted mouse mutations, drugs, or various environmental factors that have been linked to pregnancy complications or fetal loss on allantois attachment ex vivo.

This protocol describes a method to isolate and explant murine allantoides ex vivo, and details the qualitative assessment of allantois attachment to &#945;4&#946;1 integrin, a critical process during in vivo chorioallantoic fusion. The representative results shown in Figure 1A-H demonstrate the successive steps of allantois isolation starting from the pregnant uterus. Maternal tissues that surround the uter...

Watch this Scientific Journal Video about Dissection and Explant Culture of Murine Allantois for the In Vitro Analysis of Allantoic Attachment at JoVE.com

Dissection and Explant Culture of Murine Allantois for the In Vitro Analysis of Allantoic Attachment

We describe an in vitro assay to model chorioallantoic attachment, the first step in placenta formation. The protocol demonstrates the dissection and explant culture of murine allantoides on immobilized &#945;4&#946;1 integrin. Allantois attachment is evaluated microscopically at pre-determined time points.

Dissection and Explant Culture of Murine Allantois for the In Vitro Analysis of Allantoic Attachment

The placenta is essential for the growth and development of mammalian embryos. For this reason, numerous genetic alterations and likely also environmental ...

dissection-explant-culture-murine-allantois-for-vitro-analysis

Research

JoVE Journal

Medicine

7.8K Views.  University of Würzburg. We describe an in vitro assay to model chorioallantoic attachment, the first step in placenta formation. The protocol demonstrates the dissection and explant culture of murine allantoides on immobilized α4β1 integrin. Allantois attachment is evaluated microscopically at pre-determined time points.

Video: Dissection and Explant Culture of Murine Allantois for the In Vitro Analysis of Allantoic Attachment

Dissection of Human Vitreous Body Elements for Proteomic Analysis

The vitreous is an optically clear, collagenous extracellular matrix that fills the inside of the eye and overlies the retina. 1,2 Abnormal interactions between vitreous substructures and the retina underlie several vitreoretinal diseases, including retinal tear and detachment, macular pucker, macular hole, age-related macular degeneration, vitreomacular traction, proliferative vitreoretinopathy, proliferative diabetic retinopathy, and inherited vitreoretinopathies. 1,2 The molecular composition of the vitreous substructures is not known. Since the vitreous body is transparent with limited surgical access, it has been difficult to study its substructures at the molecular level. We developed a method to separate and preserve these tissues for proteomic and biochemical analysis. The dissection technique in this experimental video shows how to isolate vitreous base, anterior hyaloid, vitreous core, and vitreous cortex from postmortem human eyes. One-dimensional SDS-PAGE analyses of each vitreous component showed that our dissection technique resulted in four unique protein profiles corresponding to each substructure of the human vitreous body. Identification of differentially compartmentalized proteins will reveal candidate molecules underlying various vitreoretinal diseases.

This video shows an effective technique for differentiating and dissecting the various semi-transparent structures of the human vitreous body in post mortem eyes.

The vitreous is an optically clear, collagenous extracellular matrix that fills the inside of the eye and overlies the retina. 1,2 Abnormal interactions ...

Skin Punch Biopsy Explant Culture for Derivation of Primary Human Fibroblasts

Tissues and cell lines derived from an individual with disease are ideal sources to study disease-related cellular phenotypes. Patient-derived fibroblasts in this protocol have been successfully used in the derivation of induced pluripotent stem cells to model disease1. Early passages of these fibroblasts can also be used for cell-based functional assays to study specific disease pathways, mechanisms2 and subsequent drug screening approaches. The advantage of the presented protocol over enzymatic procedures are 1) the reproducibility of the technique from small amounts of tissue derived from older patients, e.g. patients affected with Parkinson's disease, 2) the technically simple approach over more challenging methodologies using enzymatic treatments, and 3) the time consideration: this protocol takes 15-20 min and can be performed immediately after biopsy arrival. Enzymatic treatments can take up to 4 hr and have the problems of overdigestion, reduction of cell viability and subsequent attachment of cells when not handled properly. This protocol describes the dissection and preparation of a 4-mm human skin biopsy for derivation of a fibroblast culture and has a very high success rate which is important when dealing with patient-derived tissue samples. In this culture, keratinocytes migrate out of the biopsy tissue within the first week after preparation. Fibroblasts appear 7-10 days after the first outgrowth of keratinocytes. DMEM high glucose media supplemented with 20% FBS favors the growth of fibroblasts over keratinocytes and fibroblasts will overgrow the keratinocytes. After 2 passages keratinocytes have been diluted out resulting in relatively homogenous fibroblast cultures which expresses the fibroblast marker SERPINH1 (HSP-47). Using this approach, 15-20 million fibroblasts can be derived in 4-8 weeks for cell banking. The skin dissection takes about 15-20 min, cells are then monitored once a day under the microscope, and media is changed every 2-3 days after attachment and outgrowth of cells.

The fibroblast explant culture protocol from human skin punch biopsies is a technically robust and simple way to derive skin cells within 4-8 weeks for banking of about 15-20 million cells at a low passage number.

Tissues and cell lines derived from an individual with disease are ideal sources to study disease-related cellular phenotypes. Patient-derived fibroblasts ...

Quantitative Analysis and Characterization of Atherosclerotic Lesions in the Murine Aortic Sinus

Atherosclerosis is a disease of the large arteries and a major underlying cause of myocardial infarction and stroke. Several different mouse models have been developed to facilitate the study of the molecular and cellular pathophysiology of this disease. In this manuscript we describe specific techniques for the quantification and characterization of atherosclerotic lesions in the murine aortic sinus and ascending aorta. The advantage of this procedure is that it provides an accurate measurement of the cross-sectional area and total volume of the lesion, which can be used to compare atherosclerotic progression across different treatment groups. This is possible through the use of the valve leaflets as an anatomical landmark, together with careful adjustment of the sectioning angle. We also describe basic staining methods that can be used to begin to characterize atherosclerotic progression. These can be further modified to investigate antigens of specific interest to the researcher. The described techniques are generally applicable to a wide variety of existing and newly created dietary and genetically-induced models of atherogenesis.

We describe procedures to quantify and characterize atherosclerotic lesions in mouse models using precision sectioning of the aortic sinus and ascending aorta combined with histochemical and immunohistochemical analysis.

Atherosclerosis is a disease of the large arteries and a major underlying cause of myocardial infarction and stroke. Several different mouse models have ...

Carotid Artery Infusions for Pharmacokinetic and Pharmacodynamic Analysis of Taxanes in Mice

When proposing the use of a drug, drug combination, or drug delivery into a novel system, one must assess the pharmacokinetics of the drug in the study model. As the use of mouse models are often a vital step in preclinical drug discovery and drug development1-8, it is necessary to design a system to introduce drugs into mice in a uniform, reproducible manner. Ideally, the system should permit the collection of blood samples at regular intervals over a set time course. The ability to measure drug concentrations by mass-spectrometry, has allowed investigators to follow the changes in plasma drug levels over time in individual mice1, 9, 10. In this study, paclitaxel was introduced into transgenic mice as a continuous arterial infusion over three hours, while blood samples were simultaneously taken by retro-orbital bleeds at set time points. Carotid artery infusions are a potential alternative to jugular vein infusions, when factors such as mammary tumors or other obstructions make jugular infusions impractical. Using this technique, paclitaxel concentrations in plasma and tissue achieved similar levels as compared to jugular infusion. In this tutorial, we will demonstrate how to successfully catheterize the carotid artery by preparing an optimized catheter for the individual mouse model, then show how to insert and secure the catheter into the mouse carotid artery, thread the end of the catheter out through the back of the mouse&#8217;s neck, and hook the mouse to a pump to deliver a controlled rate of drug influx. Multiple low volume retro-orbital bleeds allow for analysis of plasma drug concentrations over time.

This method was developed with the goal of delivering a steady drug solution via the carotid artery, to assess the pharmacokinetics of novel drugs in mouse models.

When proposing the use of a drug, drug combination, or drug delivery into a novel system, one must assess the pharmacokinetics of the drug in the study ...

Whole Vitreous Humor Dissection for Vitreodynamic Analysis

The authors propose an effective technique to isolate whole, intact vitreous core and cortex from post mortem enucleated porcine eyes. While previous studies have shown the results of such dissections, the detailed steps have not been described, precluding researchers outside the field from replicating their methods. Other studies harvest vitreous either through aspiration, which does not maintain the vitreous structure anatomy, or through partial dissection, which only isolates the vitreous core. The proposed method isolates the whole vitreous body, with the vitreous core and cortex intact, while maintaining vitreous anatomy and structural integrity. In this method, a full thickness scleral flap in an enucleated porcine eye is first created and through this, the choroid tissue can be separated from the sclera. The scleral flap is then expanded and the choroid is completely separated from the sclera. Finally the choroid-retina tissue is peeled off the vitreous to leave an isolated intact vitreous body. The proposed vitreous dissection technique can be used to study physical properties of the vitreous humor. In particular, this method has significance for experimental studies involving drug delivery, vitreo-retinal oxygen transport, and intraocular convection.

The goal of this protocol is to show an effective technique to isolate whole, intact vitreous core and cortex from post mortem enucleated porcine eyes.

The authors propose an effective technique to isolate whole, intact vitreous core and cortex from post mortem enucleated porcine eyes. While previous ...

Murine Prostate Micro-dissection and Surgical Castration

Mouse models are used extensively to study prostate cancer and other diseases. The mouse is an excellent model with which to study the prostate and has been used as a surrogate for discoveries in human prostate development and disease. Prostate micro-dissection allows consistent study of lobe-specific prostate anatomy, histology, and cellular characteristics in the absence of contamination of other tissues. Testosterone affects prostate development and disease. Androgen deprivation therapy is a common treatment for prostate cancer patients, but many prostate tumors become castration-resistant. Surgical castration of mouse models allows for the study of castration resistance and other facets of hormonal biology on the prostate. This procedure can be coupled with testosterone reintroduction, or hormonal regeneration of the prostate, a powerful method to study stem cell lineages in the prostate. Together, prostate micro-dissection and surgical castration opens up a multitude of opportunities for robust and consistent research of prostate development and disease. This manuscript describes the protocols for prostate micro-dissection and surgical castration in the laboratory mouse.

This manuscript describes the protocols for prostate micro-dissection and surgical castration in the laboratory mouse. We also depict representative results produced by these protocols. Finally, we discuss the advantages and utilization of these protocols.

Mouse models are used extensively to study prostate cancer and other diseases. The mouse is an excellent model with which to study the prostate and has ...

Optimized Analysis of In Vivo and In Vitro Hepatic Steatosis

Establishing a system of procedures to qualitatively and quantitatively characterize in vivo and in vitro hepatic steatosis is important for metabolic study in the liver. Here, numerous assays are described to comprehensively measure the phenotype and parameters of hepatic steatosis in mouse and hepatocyte models. 
Combining the physiological, histological, and biochemical methods, this system can be used to assess the progress of hepatic steatosis. In vivo, the measurements of body weight and nuclear magnetic resonance (NMR) provide a general understanding of mice in a non-invasive manner. Hematoxylin and Eosin (H&amp;E) and Oil Red O staining determine the histological morphology and lipid deposition of liver tissue under nutrient overload conditions, such as high-fat diet feeding. Next, the total lipid contents are isolated by chloroform/methanol extraction, which are followed by a biochemical analysis for triglyceride and cholesterol. Moreover, mouse primary hepatocytes are treated with high glucose plus insulin to stimulate lipid accumulation, an efficient in vitro model to mimic diet-induced hyperglycemia and hyperinsulinemia in vivo. Then, the lipid deposition is measured by Oil Red O staining and chloroform/methanol extraction. Oil Red O staining determines intuitive hepatic steatotic phenotypes, while the lipid extraction analysis determines the parameters that can be analyzed statistically. The present protocols are of interest to scientists in the fields of fatty liver diseases, insulin resistance, and type 2 diabetes.

Optimized Analysis of In Vivo and In Vitro Hepatic Steatosis

Here, optimized methods to generate in vivo and in vitro models of hepatic steatosis and to analyze the steatotic phenotypes and related physiological parameters are described.

Establishing a system of procedures to qualitatively and quantitatively characterize in vivo and in vitro hepatic steatosis is important for metabolic ...

Dissection of the Mouse Pancreas for Histological Analysis and Metabolic Profiling

We have been investigating the pancreas specific transcription factor, 1a cre-recombinase; lox-stop-lox- Kristen rat sarcoma, glycine to aspartic acid at the 12 codon (Ptf1acre/+;LSL-KrasG12D/+) mouse strain as a model of human pancreatic cancer. The goal of our current studies is to identify novel metabolic biomarkers of pancreatic cancer progression. We have performed metabolic profiling of urine, feces, blood, and pancreas tissue extracts, as well as histological analyses of the pancreas to stage the cancer progression. The mouse pancreas is not a well-defined solid organ like in humans, but rather is a diffusely distributed soft tissue that is not easily identified by individuals unfamiliar with mouse internal anatomy or by individuals that have little or no experience performing mouse organ dissections. The purpose of this article is to provide a detailed step-wise visual demonstration to guide novices in the removal of the mouse pancreas by dissection. This article should be especially valuable to students and investigators new to research that requires harvesting of the mouse pancreas by dissection for metabolic profiling or histological analyses.

This video article provides a detailed demonstration of the procedures required to successfully remove the pancreas from a mouse by dissection for histological analysis and metabolic profiling.

We have been investigating the pancreas specific transcription factor, 1a cre-recombinase; lox-stop-lox- Kristen rat sarcoma, glycine to aspartic acid at ...

Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research

While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a condition that typically involves damage to or loss of the delicate mechanosensory structures of the inner ear. Sophisticated in vitro and ex vivo assays have emerged in recent years, enabling the screening of an increasing number of potentially therapeutic compounds while minimizing resources and accelerating efforts to develop cures for SNHL. Though homogenous cultures of certain cell types continue to play an important role in current research, many scientists now rely on more complex organotypic cultures of murine inner ears, also known as cochlear explants. The preservation of organized cellular structures within the inner ear facilitates the in situ evaluation of various components of the cochlear infrastructure, including inner and outer hair cells, spiral ganglion neurons, neurites, and supporting cells. Here we present the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The careful preparation of these explants facilitates the identification of mechanisms that contribute to SNHL and constitutes a valuable tool for the hearing research community.

Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research

The goal of this protocol is to demonstrate the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The technique can be utilized as an in vitro screening tool in hearing research.

While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a ...

Quantitative Micro-CT Analysis of Aortopathy in a Mouse Model of &#946;-aminopropionitrile-induced Aortic Aneurysm and Dissection

Aortic aneurysm and dissection is associated with significant morbidity and mortality in the population and can be highly lethal. While animal models of aortic disease exist, in vivo imaging of the vasculature has been limited. In recent years, micro-computerized tomography (micro-CT) has emerged as a preferred modality for imaging both large and small vessels both in vivo and ex vivo. In conjunction with a method of vascular casting, we have successfully used micro-CT to characterize the frequency and distribution of aortic pathology in &#946;-aminopropionitrile-treated C57/Bl6 mice. Technical limitations of this method include variations in the quality of the perfusion introduced by poor animal preparation, the application of proper methodologies for vessel size quantification, and the non-survivability of this procedure. This article details a methodology for the intravascular perfusion of a lead-based radiopaque silicone rubber for the quantitative characterization of aortopathy in a mouse model of aneurysm and dissection. In addition to visualizing aortic pathology, this method may be used for examining other vascular beds in vivo or vascular beds removed post-mortem.

This article describes a detailed methodology of using a radiopaque lead-based silicone rubber to perfuse the murine vasculature for aortic diameter quantification in a mouse model of aortic aneurysm and dissection.

Aortic aneurysm and dissection is associated with significant morbidity and mortality in the population and can be highly lethal. While animal models of ...