We thank Jonatan Lucas for his technical assistance with feeder cell culture, Servei Estabulari de la UAB for animal care and Dom&#232;nec Mart&#237;n for recording the video. This work has been supported by Ministerio de Economia y Competitividad AGL2014-52408-R and Generalitat de Catalunya 2014 SGR-524. MVC is beneficiary of a PIF-UAB fellowship.

The use of the animals described in the sections below has been approved by the Ethics Committee on Animal and Human Research of the Universitat Aut&#242;noma de Barcelona and by the Departament d&#39;Agricultura, Ramaderia, Pesca i Alimentaci&#243; of the Generalitat de Catalunya (protocol #8741).
1. Feeder Cell Inactivation and Storage
NOTE: Human foreskin fibroblasts (HFF-1) were previously frozen in 1 mL of freezing solution consisting of 90% Fetal Bovine Serum (FBS) and 10% dimethyl sulfoxide (DMSO) and stored in liquid nitrogen until use.
<ol>
	<li>Thaw a cryogenic vial of HFF-1 (1 mL) by immersing the vial in a 37 &#176;C water bath.</li>
	<li>Add the thawed contents of the cryogenic vial to pre-warmed Dulbecco&#39;s Modified Eagle&#39;s Medium (DMEM) supplemented with 10% FBS to make a 1:10 dilution.</li>
	<li>Seed the diluted cells (10 mL) in a T75 flask and culture them at 37 &#176;C and 5% CO2.</li>
	<li>The next day, change the medium to eliminate the DMSO remnants. Remove the medium and add 10 mL of pre-warmed DMEM supplemented with 10% FBS.</li>
	<li>Culture the HFFs and change the medium every 48 h until the culture reaches the confluent stage. This may take approximately 7 to 10 days.</li>
	<li>To prepare the inactivation solution, dilute mitomycin C in DMEM supplemented with 10% FBS at a final concentration of 10 &#181;g/mL. Incubate the cells with the inactivation solution for 3 h at 37 &#176;C and 5% CO2.</li>
	<li>Remove the inactivation solution and rinse the cells thrice with 2 mL of Hanks Balanced Salt Solution (HBSS) to eliminate mitomycin C remnants.</li>
	<li>To detach the inactivated cells, add 1 mL of pre-warmed Trypsin-EDTA solution and incubate for 5 min at 37 &#176;C and 5% CO2.</li>
	<li>Observe the cells under an inverted microscope to ensure they are detached (10x objective with 0.3 numerical aperture or NA). If they are not, incubate them for a couple more minutes at 37 &#176;C and 5% CO2. Check the cells again under the inverted microscope.</li>
	<li>Pipette the solution with a Pasteur pipette in order to dissociate the cell clumps.</li>
	<li>Neutralize the enzymatic solution by adding 4 mL of DMEM supplemented with 10% FBS and resuspend.</li>
	<li>Take an aliquot of the cell suspension and make a 1:100 dilution in HBSS. To determine the number of cells, load 10 &#181;L of the dilution into a Neubauer&#39;s chamber. Count the cells located in one of the big squares of the chamber under an inverted microscope (20x objective with a 0.45 NA).
	<ol>
		<li>Repeat the counting in a total of four big squares. Calculate the total number of cells (N) as N = average number of cells counted x total volume x dilution x 104.</li>
	</ol>
	</li>
	<li>Centrifuge the rest of the sample for 5 min at 200 x g. Discard the supernatant and resuspend the pellet with freezing solution at a concentration of 106 cells per mL.</li>
	<li>Aliquot the suspension in cryogenic vials with 106 cells (1 mL) each. Place the cryogenic vials in a freezing container and freeze at -80 &#176;C.</li>
	<li>The next day, store the cryogenic vials in liquid nitrogen.</li>
</ol>
2. Feeder Cell Culture
<ol>
	<li>One to four days before starting the derivation process, thaw a cryogenic vial containing 1 x 106 inactivated HFF-1 cells in a water bath at 37 &#176;C.</li>
	<li>Make a 1:6 dilution of the thawed HFF-1 in pre-warmed DMEM supplemented with 10% FBS and keep the temperature at 37 &#176;C.</li>
	<li>Fill every well of a 4-well plate with 500 &#181;L of pre-warmed 0.2% gelatin from porcine skin and keep the plate at 37 &#176;C for 10 min.</li>
	<li>Remove the 500 &#181;L of gelatin from the wells and add 500 &#181;L of the HFFs dilution. Gently rock the plate to ensure a uniform distribution of the HFFs on the bottom of the wells. Avoid circular movements, otherwise the cells will concentrate at the center of the well.</li>
	<li>Incubate the plate at least 24 h at 37 &#176;C and 5% CO2 to obtain a monolayer of inactivated HFFs in each well.</li>
	<li>The next day, observe the cells under an inverted microscope (10X objective with 0.3 NA) and check that they are attached and homogeneously distributed. Change the medium to eliminate the DMSO remnants. Remove the medium and add 500 &#181;L of pre-warmed DMEM supplemented with 10% FBS.</li>
</ol>
3. Embryo Collection and Culture
<ol>
	<li>Four days before embryo collection, administer 5 IU of pregnant mare&#39;s serum gonadotropin by intraperitoneal injection to 6-12 week old female mice. 
	NOTE: We have used females from the 129S2 or B6CFAF1 strains, though females from other mouse strains can be used. Nevertheless, when working with females from non-permissive strains (e.g. CBA), medium should be supplemented with 2i as mentioned in step 4.2.</li>
	<li>After 48 h, administer 5 IU of human chorionic gonadotropin by intraperitoneal injection, and mate the females with males, at least 8 weeks old, at a 1:1 ratio. Separate the females from the males the next day.</li>
	<li>The day before embryo collection, prepare a 35-mm cell culture Petri dish with several 40 &#181;L drops of KSOMaag medium supplemented with 4 mg/mL Bovine Serum Albumin (BSA) and fill the plate with mineral oil to fully cover the drops. Incubate the dish at 37 &#176;C and 5% CO2 to equilibrate the medium.</li>
	<li>To prepare embryo manipulation pipettes, heat the thinner part of a long-tipped glass Pasteur pipette using a Bunsen burner. Once soft, withdraw it from the flame and pull the two ends apart. Break it to the desired length. The inner diameter at the tip should be 100-150 &#181;m.</li>
	<li>Euthanize the female mice by cervical dislocation 45-48 h post-coitum (p.c.).</li>
	<li>Dissect the mice to expose the abdominal cavity by cutting the skin with curved smooth sharp scissors and the peritoneum with straight sharp scissors. Grab one uterus with forceps, cut off the oviduct using straight sharp scissors, and place it in Hepes-buffered CZB medium (HCZB)13 at 37 &#176;C. Repeat the process to remove the other oviduct.</li>
	<li>Flush the oviducts with a 1 mL syringe loaded with HCZB held in place by watchmaker forceps to collect the 2-cell embryos. 
	NOTE: To prepare the flushing needle take a 30 G hypodermic needle, cut the end, and ground to a blunt tip on an abrasive stone.</li>
	<li>Using the mouth pipette apparatus, pick up the embryos, wash them in HCZB and culture them in the previously prepared embryo culture dish at 37 &#176;C and 5% CO2 until the blastocyst stage. Up to 50 embryos can be cultured in each 40 &#181;L drop. Monitor embryo development every 24 h under a stereomicroscope. 
	NOTE: Alternatively, embryos can be collected at the blastocyst stage to shorten in vitro embryo culture. In this case, euthanize the females at day 3.5 - 4.5 p.c., dissect the uterus. and flush it with HCZB.</li>
</ol>
4. Stem Cell Derivation
<ol>
	<li>Preparation of the derivation plates
	<ol>
		<li>On the day of embryo seeding, prepare the derivation medium by supplementing DMEM medium with 100 &#181;M 2-&#946; mercaptoethanol, 1x Non-Essential Amino Acids, 20% of serum replacement, and 103 U/mL LIF.</li>
		<li>If desired, also add 1 &#181;M of the MEK inhibitor PD0325901 and 3 &#181;M of the GSK3 inhibitor CHIR99021 to obtain a 2i medium.</li>
		<li>Take the 4-well plate with the monolayer of inactivated HFFs (step 2.6) from the incubator. Remove the medium and add 800 &#181;L of pre-warmed derivation medium to each well. Return the plate to the incubator.</li>
	</ol>
	</li>
	<li>Zona pellucida removal and embryo seeding
	<ol>
		<li>Prepare a 35 mm cell culture Petri dish with three 30 &#181;L drops of acidic Tyrode&#39;s solution14 and three 30 &#181;L drops of derivation medium. Cover the drops with mineral oil and keep the dish at 37 &#176;C.</li>
		<li>Take the embryo culture dish from the incubator. One by one, transfer the blastocysts from the culture drops to an acidic Tyrode&#39;s solution drop using an embryo manipulation pipette. If possible, select only the expanded blastocysts to start the derivation process.</li>
		<li>Monitor the zona pellucida digestion under the stereomicroscope. As soon as the zona pellucida disappears, transfer the blastocyst to a derivation medium drop in order to wash out the acidic Tyrode&#39;s solution.</li>
		<li>Take the 4-well derivation plate from the incubator and seed one zona-free blastocyst on the feeder cells in each well.</li>
		<li>Return the 4-well derivation plate to the incubator and culture at 37 &#176;C and 5% CO2.</li>
	</ol>
	</li>
	<li>Monitoring stem cell growth and medium change
	<ol>
		<li>Monitor the cultures every 24 h under an inverted microscope (20X objective with 0.45 NA). It is important to note whether there are signs of stem cell differentiation, such as swollen refractive cells surrounding the outgrowth or even pushing the feeder cells aside.</li>
		<li>Every other day, change the medium of the culture. Take the 4-well plate from the incubator, remove the medium from each well, and add 800 &#181;L of pre-warmed derivation medium supplemented with LIF and 2i, if used. Maintain the culture until outgrowths are observed (6-8 days).</li>
	</ol>
	</li>
</ol>
5. Stem Cell Culture and Maintenance
<ol>
	<li>Prepare Kolle-like handles and stem cell manipulation pipettes. Follow step 3.4 to prepare stem cell manipulation pipettes with an inner diameter at the tip of 250-300 &#181;m. Use the other part of the pulled Pasteur pipette to prepare the Kolle-like handle. Heat and shape it until obtaining a hook.</li>
	<li>Take the 4-well culture plate out of the incubator and locate the outgrowth under a stereomicroscope. Use the handle to push away the differentiated cells and the feeders that surround the outgrowth. 
	NOTE: To avoid eventual differentiation of the outgrowth, it is important to remove all the differentiated cells from the edge of the outgrowth.</li>
	<li>Aspirate the outgrowth with a stem cell manipulation pipette and place it in a new dish in a 50 &#181;L trypsin-EDTA drop.</li>
	<li>Use a scalpel to cut the outgrowth in several parts in order to disaggregate it both mechanically and enzymatically.</li>
	<li>Straight away, transfer the outgrowth fragments into a fresh drop of derivation medium to neutralize trypsin action.</li>
	<li>Transfer the outgrowth fragments to a new 4-well plate with a monolayer of feeders. Transfer up to 10 fragments per well and culture them with derivation medium at 37 &#176;C and 5% CO2.</li>
	<li>Maintain the stem cell-like cultures for at least six weeks before considering the mESC line established. Change the medium every other day and subculture them once a week.</li>
</ol>

<ol>
	<li>Biswas, A., Hutchins, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryonic+stem+cells.">Embryonic stem cells.</a> Stem Cell Dev. 16 (2), 213-221 (2007).</li><li>Weinberger, L., Ayyash, M., Novershtern, N., Hanna, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+stem+cell+states:+naive+to+primed+pluripotency+in+rodents+and+humans.">Dynamic stem cell states: naive to primed pluripotency in rodents and humans.</a> Nat Rev Mol Cell Biol. 17 (3), 155-169 (2016).</li><li>Evans, M. J., Kaufman, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+in+culture+of+pluripotential+cells+from+mouse+embryos.">Establishment in culture of pluripotential cells from mouse embryos.</a> Nature. 292, 154-156 (1981).</li><li>Martin, G. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+a+pluripotent+cell+line+from+early+mouse+embryos+cultured+in+medium+conditioned+by+teratocarcinoma+stem+cells.">Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells.</a> Proc Nat Acad Sci U S A. 78 (12), 7634-7638 (1981).</li><li>Martin, G. R., Evans, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+clonal+lines+of+teratocarcinoma+cells:+formation+of+embryoid+bodies+in+vitro.">Differentiation of clonal lines of teratocarcinoma cells: formation of embryoid bodies in vitro.</a> PNAS. 72 (4), 1441-1445 (1976).</li><li>Czechanski, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Derivation+and+characterization+of+mouse+embryonic+stem+cells+from+permissive+and+nonpermissive+strains.">Derivation and characterization of mouse embryonic stem cells from permissive and nonpermissive strains.</a> Nat Prot. 9 (3), 559-574 (2014).</li><li>Smith, A. 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=Inhibition+of+pluripotential+embryonic+stem+cell+differentiation+by+purified+polypeptides.">Inhibition of pluripotential embryonic stem cell differentiation by purified polypeptides.</a> Nature. 336 (6200), 688-690 (1988).</li><li>Williams, R. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myeloid+leukaemia+inhibitory+factor+maintains+the+developmental+potential+of+embryonic+stem+cells.">Myeloid leukaemia inhibitory factor maintains the developmental potential of embryonic stem cells.</a> Nature. 336 (6200), 684-687 (1988).</li><li>Brook, F. A., 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=The+origin+and+efficient+derivation+of+embryonic+stem+cells+in+the+mouse.">The origin and efficient derivation of embryonic stem cells in the mouse.</a> Proc Nat Acad Sci U S A. 94 (11), 5709-5712 (1997).</li><li>Ward, C. M., Stern, P., Willington, M. A., Flenniken, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+germline+transmission+of+mouse+embryonic+stem+cells+grown+in+synthetic+serum+in+the+absence+of+a+fibroblast+feeder+layer.">Efficient germline transmission of mouse embryonic stem cells grown in synthetic serum in the absence of a fibroblast feeder layer.</a> Lab Invest. 82 (12), 1765-1767 (2002).</li><li>Ying, Q. 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=The+ground+state+of+embryonic+stem+cell+self-renewal.">The ground state of embryonic stem cell self-renewal.</a> Nature. 453 (7194), 519-523 (2008).</li><li>Wakayama, S., 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=Efficient+establishment+of+mouse+embryonic+stem+cell+lines+from+single+blastomeres+and+polar+bodies.">Efficient establishment of mouse embryonic stem cell lines from single blastomeres and polar bodies.</a> Stem cells (Dayton, Ohio). 25 (4), 986-993 (2007).</li><li>Chatot, C. L., Ziomek, C. A., Bavister, B. D., Lewis, J. L., Torres, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+culture+medium+support+development+of+random-bred+1-cell+mouse+embryos+in+vitro.">An improved culture medium support development of random-bred 1-cell mouse embryos in vitro.</a> J Reprod Fertil. 86, 679-688 (1989).</li><li>Nagy, A., Vintersten, K., Behringer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Manipulating the Mouse Embryo: A Laboratory Manual. , (2003).</li><li>Lee, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conditions+and+techniques+for+mouse+embryonic+stem+cell+derivation+and+culture.">Conditions and techniques for mouse embryonic stem cell derivation and culture.</a> Pluripotent Stem Cells. , 85-115 (2013).</li><li>Ma, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+foreskin+fibroblast+produces+interleukin-6+to+support+derivation+and+self-renewal+of+mouse+embryonic+stem+cells.">Human foreskin fibroblast produces interleukin-6 to support derivation and self-renewal of mouse embryonic stem cells.</a> Stem Cell Res Ther. 3 (29), (2012).</li><li>Cheng, J., Dutra, A., Takesono, A., Garrett-Beal, L., Schwartzberg, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+generation+of+C57BL/6J+mouse+embryonic+stem+cells+in+a+defined+serum-free+media.">Improved generation of C57BL/6J mouse embryonic stem cells in a defined serum-free media.</a> Genesis. 39 (2), 100-104 (2004).</li><li>Chaudhry, M. A., Vitalis, T. Z., Bowen, B. D., Piret, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basal+medium+composition+and+serum+or+serum+replacement+concentration+influences+on+the+maintenance+of+murine+embryonic+stem+cells.">Basal medium composition and serum or serum replacement concentration influences on the maintenance of murine embryonic stem cells.</a> Cytotechnology. 58 (3), 173-179 (2008).</li><li>Kawase, E., Suemori, H., Takahashi, N., Okazaki, K., Hashimoto, K., Nakatsuji, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strain+difference+in+establishment+of+mouse+embryonic+stem+(ES)+cell+lines.">Strain difference in establishment of mouse embryonic stem (ES) cell lines.</a> Int. J. Dev. Biol. 38 (2), 385-390 (1994).</li><li>Gonzalez, J. 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=Embryonic+stem+cell+culture+conditions+support+distinct+states+associated+with+different+developmental+stages+and+potency.">Embryonic stem cell culture conditions support distinct states associated with different developmental stages and potency.</a> Stem Cell Rep. 7 (2), 177-191 (2016).</li></ol>

The authors have nothing to disclose.

Although mESC line derivation is a well-known procedure routinely used in many laboratories, its efficiency is not always as high as expected due to the multiple factors that can disturb pluripotency maintenance. In the present article we show, step by step, how to establish mESC lines with high efficiencies using a simple and reliable protocol. These efficiencies are similar to those reported in the literature. 
To ensure maximum efficiency, it is important to control the cells daily or every...

Embryonic stem cells (ESC) are pluripotent cells derived from preimplantation embryos, which retain the ability to either self-renew or differentiate under specific conditions1. Based on these properties, ESC have become a useful tool for regenerative medicine, disease modeling, and tissue engineering studies2.
ESC were derived for the first time from preimplantation mouse embryos, originating mouse ESC (mESC) lines with low success3,4. For years, the derivation efficiency remained low due to the difficulty of maintaining pluripotency in vitro. Besides the presence of feeder cells5, which improve derivation efficiency, promote colony attachment, and enhance karyotypic stability6, several modifications of the protocol lead to an improvement in pluripotency maintenance. The most important were the addition of Leukemia Inhibitory Factor (LIF) to mESC culture medium7,8, the use of embryos from the 129S2 permissive background9 and the culture of mESC with medium supplemented with defined serum, free of potential differentiation factors10. More recently, compelling evidence has shown that addition of a cocktail of two small-molecule modulators of signaling pathways to the mESC culture medium (known as 2i) is best to maintain pluripotency. The 2i cocktail consists of a combination of the MEK inhibitor PD0325901, which reduces the differentiation signals by inhibiting the mitogen-activated protein kinase (MAPK) pathway, and the GSK3&#946; inhibitor CHIR99021, which enhances cell survival at low density by activating the Wnt pathway11. 
In the present article, we describe a simple protocol to efficiently derive mESC lines from mouse blastocysts. We follow standard procedures, culturing embryos from permissive strains on feeder cells in derivation medium supplemented with LIF and a serum replacement12. Following this protocol, mESC lines can be derived with efficiencies equivalent to those obtained in 2i medium. In spite of this, 2i can be added to avoid possible problems with pluripotency maintenance or when working with non-permissive strains.

<table><tbody><tr><td>1 mL sryringe</td><td>BD&amp;nbsp;</td><td>309628</td><td></td></tr><tr><td>2-&amp;beta;-mercaptoethanol</td><td>Life Technologies</td><td>31350-010</td><td></td></tr><tr><td>4-well plate</td><td>Thermo Scientific Nunc</td><td>176740</td><td></td></tr><tr><td>Acidic Tyrode&#039;s solution&amp;nbsp;</td><td>Home-made</td><td></td><td>See recipe in Nagy et al, 2003. For short-term storage (up to 1 month) keep it at 4&amp;ordm;C. Alternatively, for long-term storage keep it at -20&amp;ordm;C. If the efficiency of the solution diminishes, it should be acidified by the adition of a small drop of HCl 1M.&amp;nbsp;</td></tr><tr><td>BSA</td><td>Sigma</td><td>A3311</td><td></td></tr><tr><td>Chicken anti-Mouse IgG, Alexa Fluor 488</td><td>Molecular Probes - Invitrogen</td><td>A-21200</td><td>1:500 dilution. Secondary antibody for Oct4, Tuj1, &amp;alpha;SMA and AFP mouse antibodies.&amp;nbsp;</td></tr><tr><td>CHIR990212</td><td>Axon Medchem&amp;nbsp;</td><td>1386</td><td>Reconstitute with 2.15 ml DMSO for each mg of powder, to obtain a 1 mM stock solution. Aliquot at desired volume and store at -20&amp;ordm;C. Avoid freeze and thaw cycles.&amp;nbsp;</td></tr><tr><td>CryoTube</td><td>Thermo Scientific Nunc</td><td>3754518</td><td></td></tr><tr><td>DMSO</td><td>Sigma</td><td>41640</td><td></td></tr><tr><td>DMEM</td><td>BioWest</td><td>L0107</td><td></td></tr><tr><td>FBS</td><td>BioWest</td><td>S1810</td><td>Inactivate it prior to use by heating for 30 mins at 56&amp;ordm;C. Aliquot and store at -20&amp;ordm;C</td></tr><tr><td>Flushing needle</td><td>BD&amp;nbsp;</td><td>304000</td><td>Cut the end of the needle and ground to a blunt tip on an abrasive stone</td></tr><tr><td>Gelatin from porcine skin</td><td>Fluka</td><td>48724</td><td>Dilute at 0,2% in destilled water and autoclave it. Each dilution can be used for a month.</td></tr><tr><td>Goat anti-Rabbit IgG, Alexa Fluor 594</td><td>Molecular Probes - Invitrogen</td><td>A-11037</td><td>1:500 dilution. Secondary antibody for Sox2 rabbit antibody.&amp;nbsp;</td></tr><tr><td>HBSS</td><td>BioWest</td><td>L0611</td><td></td></tr><tr><td>Hepes-buffered CZB&amp;nbsp;</td><td>Home-made</td><td></td><td>See composition in Chatot et al, 1989</td></tr><tr><td>Human chorionic gonadotropin</td><td>Divasa-Farmavic</td><td>Veterin-Corion 3000 UI</td><td>Dilute in NaCl 0.9% at 50 IU/ml. Aliquot it in 1 ml and store at -20&amp;ordm;C for up to two months. Once thawed do not freeze again.&amp;nbsp;</td></tr><tr><td>Human foreskin fibroblasts</td><td>ATCC</td><td>ATCCSCRC-1041</td><td>For long term storage it is recommended to store them in liquid nitrogen.</td></tr><tr><td>KnockOut Serum Replacement</td><td>Life Technologies</td><td>&amp;nbsp;10828-028</td><td>Photosensitive. It is recommended to aliquot it in small volumes such as 10 ml and store it at -20&amp;ordm;C (check the expiration date). Avoid freeze and thaw cycles.&amp;nbsp;&amp;nbsp;&amp;nbsp;</td></tr><tr><td>KSOMaag Evolve</td><td>Zenith Biotech</td><td>ZEKS-050</td><td>Supplement with 4 mg/ml BSA. Equilibrate at 37&amp;ordm;C and 5% CO2 a day prior to use.</td></tr><tr><td>Leukemia Inhibitory Factor</td><td>Merk Millipore</td><td>ESG1106</td><td></td></tr><tr><td>Mice&amp;nbsp;</td><td>Charles River/Harlan</td><td></td><td>It is recommended to use mice from a permissive strain in terms of mESC derivation (such as 129S2 or C57BL). However, inbreed strains are less efficient producing embryos. Therefore, it is recomended to use a hybrid strain, such as 129S2 x C57BL or B6CBAF1 to take advantage of the hybrid vigor.&amp;nbsp;</td></tr><tr><td>Mineral oil</td><td>Sigma</td><td>M8410</td><td>Embryo tested. Photosensitive.&amp;nbsp;</td></tr><tr><td>Mitomycin C</td><td>Serva</td><td>2980501</td><td>Reconstitute the powder with MilliQ water at 0.5 mg/ml. Store at 4&amp;ordm;C protected from light. Attention, it is harmful and suspected of causing cancer.&amp;nbsp;</td></tr><tr><td>Mouse anti-tubulin &amp;beta; III (Tuj1)</td><td>Biolegend</td><td>MMS-435P</td><td>1:500 dilution</td></tr><tr><td>Mouse monoclonal anti-&amp;alpha;SMA</td><td>Sigma</td><td>A5228</td><td>1:200 dilution</td></tr><tr><td>Mouse monoclonal anti-AFP</td><td>R&amp;amp;D Systems</td><td>MAB1368</td><td>1:50 dilution</td></tr><tr><td>Mouse monoclonal anti Oct3/4&amp;nbsp;</td><td>Santa cruz</td><td>Sc-5279</td><td>1:50 dilution</td></tr><tr><td>Non-Essential Amino Acids</td><td>Life Technologies</td><td>11140-035</td><td></td></tr><tr><td>PD0325901</td><td>Axon Medchem&amp;nbsp;</td><td>1408</td><td>Reconstitute with 2.08 ml DMSO for each mg of powder, to obtain a 1 mM stock solution. Aliquot at desired volume and store at -20&amp;ordm;C. Avoid freeze and thaw cycles.</td></tr><tr><td>Petri dish (35mm)</td><td>Thermo Scientific Nunc</td><td>153066</td><td></td></tr><tr><td>Petri dish (60mm)</td><td>Thermo Scientific Nunc</td><td>150288</td><td></td></tr><tr><td>Pregnant mare&#039;s serum gonadotropin</td><td>Foligon</td><td>Foligon-1000 UI</td><td>Dilute in NaCl 0.9% at 50 IU/ml. Aliquot it in 1 ml and store at -20&amp;ordm;C for up to two months. Once thawed do not freeze again.&amp;nbsp;</td></tr><tr><td>Rabbit policlonal anti-Sox2</td><td>Merck Millipore</td><td>AB5603</td><td>1:200 dilution</td></tr><tr><td>T75 falcon</td><td>Thermo Scientific</td><td>130190</td><td></td></tr><tr><td>Trypsin-EDTA 10x</td><td>BioWest</td><td>X0930</td><td>Dilute 1:10 in HBSS to obtain a 1x solution</td></tr></tbody></table>

derivation of stem cell lines from mouse preimplantation embryos

Mouse embryonic stem cell (mESC) derivation is the process by which pluripotent cell lines are established from preimplantation embryos. These lines retain the ability to either self-renew or differentiate under specific conditions. Due to these properties, mESC are a useful tool in regenerative medicine, disease modeling, and tissue engineering studies. This article describes a simple protocol to obtain mESC lines with high derivation efficiencies (60-80%) by culturing blastocysts from permissive mouse strains on feeder cells in defined medium supplemented with leukemia inhibitory factor. The protocol can also be applied to efficiently derive mESC lines from non-permissive mouse strains, by the simple addition of a cocktail of two small-molecule inhibitors to the derivation medium (2i medium). Detailed procedures on the preparation and culture of feeder cells, collection and culture of mouse embryos, and derivation and culture of mESC lines are provided. This protocol does not require specialized equipment and can be carried out in any laboratory with basic mammalian cell culture expertise.

Following this protocol, over 95% of outgrowth formation should be achieved after the first week of culture (Figure 1A). Establishment of mESC lines after six passages is variable among experimental replicates, with an average success of 60-80%. The addition of 2i does not significantly improve the results when working with permissive mouse strains, such as those with a 129S2 background, but it is necessary when working with non-permissive strains.
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Derivation of Stem Cell Lines from Mouse Preimplantation Embryos

This article describes a protocol to efficiently derive and culture pluripotent stem cell lines from mouse embryos at the blastocyst stage.

Mouse embryonic stem cell (mESC) derivation is the process by which pluripotent cell lines are established from preimplantation embryos. These lines ...

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JoVE Journal

Developmental Biology

8.3K Views.  Universitat Autònoma de Barcelona. Dit artikel beschrijft een protocol om efficiënt ontlenen en cultuur pluripotente stamcellijnen uit muis embryo's in het blastocyst stadium.

Video: Derivation of Stem Cell Lines from Mouse Preimplantation Embryos

Derivation of Hematopoietic Stem Cells from Murine Embryonic Stem Cells

A stem cell is defined as a cell with the capacity to both self-renew and generate multiple differentiated progeny.  Embryonic stem cells (ESC) are derived from the blastocyst of the early embryo and are pluripotent in differentiative ability.  Their vast differentiative potential has made them the focus of much research centered on deducing how to coax them to generate clinically useful cell types.  The successful derivation of hematopoietic stem cells (HSC) from mouse ESC has recently been accomplished and can be visualized in this video protocol.  HSC, arguably the most clinically exploited cell population, are used to treat a myriad of hematopoietic malignancies and disorders.  However, many patients that might benefit from HSC therapy lack access to suitable donors.  ESC could provide an alternative source of HSC for these patients.  The following protocol establishes a baseline from which ESC-HSC can be studied and inform efforts to isolate HSC from human ESC.  In this protocol, ESC are differentiated as embryoid bodies (EBs) for 6 days in commercially available serum pre-screened for optimal hematopoietic differentiation.  EBs are then dissociated and infected with retroviral HoxB4.  Infected EB-derived cells are plated on OP9 stroma, a bone marrow stromal cell line derived from the calvaria of  M-CSF-/- mice, and co-cultured in the presence of hematopoiesis promoting cytokines for ten days.  During this co-culture, the infected cells expand greatly, resulting in the generation a heterogeneous pool of 100s of millions of cells.  These cells can then be used to rescue and reconstitute lethally irradiated mice.

This protocol details the derivation of transplantable hematopoietic stem cells from mouse embryonic stem cells (ESC) and their subsequent injection into lethally irradiated recipient mice. Briefly, ESC are differentiated as embryoid bodies, which are then infected with retroviral HoxB4 and co-cultured with OP9 stromal cells and hematopoietic cytokines.

A stem cell is defined as a cell with the capacity to both self-renew and generate multiple differentiated progeny.  Embryonic stem cells (ESC) are ...

Biology

Quantitative Analysis of Protein Expression to Study Lineage Specification in Mouse Preimplantation Embryos

This protocol presents a method to perform quantitative, single-cell in situ analyses of protein expression to study lineage specification in mouse preimplantation embryos. The procedures necessary for embryo collection, immunofluorescence, imaging on a confocal microscope, and image segmentation and analysis are described. This method allows quantitation of the expression of multiple nuclear markers and the spatial (XYZ) coordinates of all cells in the embryo. It takes advantage of MINS, an image segmentation software tool specifically developed for the analysis of confocal images of preimplantation embryos and embryonic stem cell (ESC) colonies. MINS carries out unsupervised nuclear segmentation across the X, Y and Z dimensions, and produces information on cell position in three-dimensional space, as well as nuclear fluorescence levels for all channels with minimal user input. While this protocol has been optimized for the analysis of images of preimplantation stage mouse embryos, it can easily be adapted to the analysis of any other samples exhibiting a good signal-to-noise ratio and where high nuclear density poses a hurdle to image segmentation (e.g., expression analysis of embryonic stem cell (ESC) colonies, differentiating cells in culture, embryos of other species or stages, etc.).

This protocol presents a method to perform quantitative, single-cell in situ analysis of protein expression to study lineage specification in mouse preimplantation embryos. The procedures necessary for collection of blastocysts, whole-mount immunofluorescent detection of proteins, imaging of samples on a confocal microscope, and nuclear segmentation and image analysis are described.

This protocol presents a method to perform quantitative, single-cell in situ analyses of protein expression to study lineage specification in mouse ...

Loss- and Gain-of-function Approach to Investigate Early Cell Fate Determinants in Preimplantation Mouse Embryos

Gene silencing and overexpression techniques are instrumental for the identification of genes involved in embryonic development. Direct target gene modification in preimplantation embryos provides a means to study the underlying mechanisms of genes implicated in, for instance, cellular differentiation into the trophectoderm (TE) and the inner cell mass (ICM). Here, we describe a protocol that examines the role of neogenin as an authentic receptor for initial cell fate determination in preimplantation mouse embryos. First, we discuss the experimental manipulations that were used to produce gain and loss of neogenin function by microinjecting neogenin cDNA and shRNA; the effectiveness of this approach was confirmed by a strong correlation between the pair-wise expression levels of either red fluorescent protein (RFP) or green fluorescent protein (GFP) and the immunocytochemical quantification of neogenin expression. Secondly, overexpression of neogenin in preimplantation mouse embryos leads to normal ICM development while neogenin knockdown causes the ICM to develop abnormally, implying that neogenin could be a receptor that relays extracellular cues to drive blastomeres to early cell fates. Given the success of this detailed protocol in investigating the function of a novel embryonic developmental stage-specific receptor, we propose that it has the potential to aid in exploration and identification of other stage-specific genes during embryogenesis.

The goal of this protocol is to describe a loss- and gain-of function method that is applicable to identify neogenin as a stage-specific receptor that leads to trophectoderm and inner cell mass differentiation in preimplantation mouse embryos.

 Gene silencing and overexpression techniques are instrumental for the identification of genes involved in embryonic development. Direct target gene ...

Derivation of Human Embryonic Stem Cells by Immunosurgery

The ability of human embryonic stem cells to self-renew and differentiate into all cell types of 
the body suggests that they hold great promise for both medical applications and as a research 
tool for addressing fundamental questions in development and disease. Here, we provide a 
concise, step-by-step protocol for the derivation of human embryonic stem cells from embryos 
by immunosurgical isolation of the inner cell mass. 


The ability of human embryonic stem cells to self-renew and differentiate into all cell types of 
the body suggests that they hold great promise for both medical applications and as a research 
tool for addressing fundamental questions in development and disease. Here, we provide a 
concise, step-by-step protocol for the derivation of human embryonic stem cells from embryos 
by immunosurgical isolation of the inner cell mass.

The ability of human embryonic stem cells to self-renew and differentiate into all cell types of 
the body suggests that they hold great promise for both ...

Isolation and Derivation of Mouse Embryonic Germinal Cells

The ability of embryonic germinal cells (EG) to differentiate into primordial germinal cells (PGCs) and later into gametes during early developmental stages is a perfect model to address our hypothesis about cancer and infertility. This protocol shows how to isolate primordial germinal cells from developing gonads in 10.5-11.5 days post coitum (dpc) mouse embryos.  Developing gonadal ridges from mouse embryos (C57BL6J) were dissociated by mechanical disruption with collagenase, then plated in a mouse embryo fibroblast feeder layer (MEF-CF1) that was previously mitotically inactivated with mitomycin C in the presence of knockout media and supplemented with Leukemia Inhibitor Factor (LIF), basic Fibroblast Growth Factor (bFGF), and Stem Cell Factor (SCF).  Using these optimized methods for PCG identification, isolation, and establishment of culture conditions permits long term cultures of EG cells for more than 40 days.  The embryonic germinal cell lines showed embryonic phenotype and expression of common used markers of the pluripotent state.  Isolation and derivation of germinal cells in culture provide a tool to understand their development in vitro and offer the opportunity to monitor cumulative damage at genetic and epigenetic levels after exposure to oxidative stress.

The ability of embryonic germinal cells to differentiate into primordial germinal cells during early development stages is a perfect model to address our hypothesis about cancer and infertility. This protocol shows how to isolate primordial germinal cells from developing gonads in 10.5-11.5 days post coitum mouse embryos.

The ability of embryonic germinal cells (EG) to differentiate into primordial germinal cells (PGCs) and later into gametes during early developmental ...

Derivation of Mouse Trophoblast Stem Cells from Blastocysts

Specification of the trophectoderm is one of the earliest differentiation events of mammalian development. The trophoblast lineage derived from the trophectoderm mediates implantation and generates the fetal part of the placenta. As a result, the development of this lineage is essential for embryo survival. Derivation of trophoblast stem (TS) cells from mouse blastocysts was first described by Tanaka et al. 1998. The ability of TS cells to preserve the trophoblast specific property and their expression of stage- and cell type-specific markers after proper stimulation provides a valuable model system to investigate trophoblast lineage development whereby recapitulating early placentation events. Furthermore, trophoblast cells are one of the few somatic cell types undergoing natural genome amplification. Although the molecular pathways underlying trophoblast polyploidization have begun to unravel, the physiological role and advantage of trophoblast genome amplification remains largely elusive. The development of diploid stem cells into polyploid trophoblast cells in culture makes this ex vivo system an excellent tool for elucidating the regulatory mechanism of genome replication and instability in health and disease. Here we describe a protocol based on previous reports with modification published in Chiu et al. 2008.

In this video, we demonstrate the isolation of mouse blastocysts and the derivation of trophoblast stem cells from blastocysts. We also describe conditions for maintenance of the stem cell property as well as induction of differentiation in culture.

Specification of the trophectoderm is one of the earliest differentiation events of mammalian development. The trophoblast lineage derived from the ...

Application of Mouse Parthenogenetic Haploid Embryonic Stem Cells as a Substitute of Sperm

In organisms with sexual reproduction, germ cells are the source of totipotent cells that develop into new individuals. In mice, fertilization of an oocyte by a spermatozoon creates a totipotent zygote. Recently, several publications have reported that haploid embryonic stem cells (haESCs) can be a substitute for gametic genomes and contribute to embryos, which develop into mice. Here, we present a protocol to apply parthenogenetic haESCs as a substitute of sperm to construct embryos by intracytoplasmic injection into oocytes. This protocol consists of steps for preparing haESCs as sperm replacement, for injection of haESC chromosomes into oocytes, and for culture of semi-cloned embryos. The embryos can yield fertile semi-cloned mice after embryo transfer. Using haESCs as sperm replacement facilitates genome editing in the germline, studies of embryonic development, and investigation of genomic imprinting.

This article aims to demonstrate the use of parthenogenetic haploid embryonic stem cells as a substitute for sperm for the construction of semi-cloned embryos.

In organisms with sexual reproduction, germ cells are the source of totipotent cells that develop into new individuals. In mice, fertilization of an ...

Generation of Mice Derived from Induced Pluripotent Stem Cells

The production of induced pluripotent stem cells (iPSCs) from somatic cells provides a means to create valuable tools for basic research and may also produce a source of patient-matched cells for regenerative therapies. iPSCs may be generated using multiple protocols and derived from multiple cell sources. Once generated, iPSCs are tested using a variety of assays including immunostaining for pluripotency markers, generation of three germ layers in embryoid bodies and teratomas, comparisons of gene expression with embryonic stem cells (ESCs) and production of chimeric mice with or without germline contribution2. Importantly, iPSC lines that pass these tests still vary in their capacity to produce different differentiated cell types2. This has made it difficult to establish which iPSC derivation protocols, donor cell sources or selection methods are most useful for different applications.
The most stringent test of whether a stem cell line has sufficient developmental potential to generate all tissues required for survival of an organism (termed full pluripotency) is tetraploid embryo complementation (TEC)3-5. Technically, TEC involves electrofusion of two-cell embryos to generate tetraploid (4n) one-cell embryos that can be cultured in vitro to the blastocyst stage6. Diploid (2n) pluripotent stem cells (e.g. ESCs or iPSCs) are then injected into the blastocoel cavity of the tetraploid blastocyst and transferred to a recipient female for gestation (see Figure 1). The tetraploid component of the complemented embryo contributes almost exclusively to the extraembryonic tissues (placenta, yolk sac), whereas the diploid cells constitute the embryo proper, resulting in a fetus derived entirely from the injected stem cell line.
Recently, we reported the derivation of iPSC lines that reproducibly generate adult mice via TEC1. These iPSC lines give rise to viable pups with efficiencies of 5-13%, which is comparable to ESCs3,4,7 and higher than that reported for most other iPSC lines8-12. These reports show that direct reprogramming can produce fully pluripotent iPSCs that match ESCs in their developmental potential and efficiency of generating pups in TEC tests. At present, it is not clear what distinguishes between fully pluripotent iPSCs and less potent lines13-15. Nor is it clear which reprogramming methods will produce these lines with the highest efficiency. Here we describe one method that produces fully pluripotent iPSCs and "all- iPSC" mice, which may be helpful for investigators wishing to compare the pluripotency of iPSC lines or establish the equivalence of different reprogramming methods.

Generating induced pluripotent stem cell (iPSC) lines produces lines of differing developmental potential even when they pass standard tests for pluripotency. Here we describe a protocol to produce mice derived entirely from iPSCs, which defines the iPSC lines as possessing full pluripotency1.

The production of induced pluripotent stem cells (iPSCs) from somatic cells provides a means to create valuable tools for basic research and may also ...

Differentiation of Newborn Mouse Skin Derived Stem Cells into Germ-like Cells In vitro

Studying germ cell formation and differentiation has traditionally been very difficult due to low cell numbers and their location deep within developing embryos. The availability of a "closed" in vitro based system could prove invaluable for our understanding of gametogenesis. The formation of oocyte-like cells (OLCs) from somatic stem cells, isolated from newborn mouse skin, has been demonstrated and can be visualized in this video protocol. The resulting OLCs express various markers consistent with oocytes such as Oct4 , Vasa , Bmp15, and Scp3. However, they remain unable to undergo maturation or fertilization due to a failure to complete meiosis. This protocol will provide a system that is useful for studying the early stage formation and differentiation of germ cells into more mature gametes. During early differentiation the number of cells expressing Oct4 (potential germ-like cells) reaches ~5%, however currently the formation of OLCs remains relatively inefficient. The protocol is relatively straight forward though special care should be taken to ensure the starting cell population is healthy and at an early passage.

Differentiation of Newborn Mouse Skin Derived Stem Cells into Germ-like Cells In vitro

In recent years the formation of germ cells using in vitro culture methods has been demonstrated using several different types of somatic stem cells. This article will visually present the differentiation of newborn mouse derived stem cells to early oocyte-like cells.

Studying  germ cell formation and differentiation has traditionally been very difficult  due to low cell numbers and their location deep within developing ...

Cell Labeling and Injection in Developing Embryonic Mouse Hearts

Testing the fate of embryonic or pluripotent stem cell-derivatives in in vitro protocols has led to controversial outcomes that do not necessarily reflect their in vivo potential. Preferably, these cells should be placed in a proper embryonic environment in order to acquire their definite phenotype. Furthermore, cell lineage tracing studies in the mouse after labeling cells with dyes or retroviral vectors has remained mostly limited to early stage mouse embryos with still poorly developed organs. To overcome these limitations, we designed standard and ultrasound-mediated microinjection protocols to inject various agents in targeted regions of the heart in mouse embryos at E9.5 and later stages of development. &#160;Embryonic explant or embryos are then cultured or left to further develop in utero. These agents include fluorescent dyes, virus, shRNAs, or stem cell-derived progenitor cells. Our approaches allow for preservation of the function of the organ while monitoring migration and fate of labeled and/or injected cells. These technologies can be extended to other organs and will be very helpful to address key biological questions in biology of development.

We describe a series of methods to inject dyes, DNA vectors, virus, and cells in order to monitor both cell fate and phenotype of endogenous and grafted cells derived from embryonic or pluripotent cells within mouse embryos at embryonic day (E)9.5 and later stages of development.

Testing the fate of embryonic or pluripotent stem cell-derivatives in in vitro protocols has led to controversial outcomes that do not necessarily reflect ...

Derivation of Stem Cell Lines from Mouse Preimplantation Embryos

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