We thank George Galaris (LUMC, Leiden, the Netherlands) for his help with chicken embryo injection. We acknowledge the support of Saskia van der Wal-Maas (Department of Anatomy &#38; Embryology, LUMC, Leiden, the Netherlands), Conny van Munsteren (Department of Anatomy &#38; Embryology, LUMC, Leiden, the Netherlands), Manon Zuurmond (LUMC, Leiden, the Netherlands), and Annemarie de Graaf (LUMC, Leiden, the Netherlands). M. Koning is supported by &#39;Nephrosearch Stichting tot steun van het wetenschappelijk onderzoek van de afdeling Nierziekten van het LUMC&#39;. This work was in part supported by the Leiden University Fund &#34;Prof. Jaap de Graeff-Lingling Wiyadhanrma Fund&#34; GWF2019-02. This work is supported by the partners of Regenerative Medicine Crossing Borders (RegMedXB) and Health Holland, Top Sector Life Sciences &#38; Health. C.W. van den Berg and T.J. Rabelink are supported by The Novo Nordisk Foundation Center for Stem Cell Medicine (reNEW), The Novo Nordisk Foundation Center for Stem Cell Medicine is supported by Novo Nordisk Foundation grants (NNF21CC0073729).

In accordance with Dutch law, approval by the animal welfare committee was not required for this research.
1. Preparing hiPSC-derived kidney organoids for transplantation
<ol>
	<li>Differentiate hiPSCs to kidney organoids using the protocol developed by Takasato et al.4,18,31. Culture the organoids following this protocol on polyester cell culture inserts with 0.4 &#181;m pores (cell culture inserts) until day 7 + 12 of differentiation. Each cell culture insert will contain three organoids.</li>
	<li>Remove the organoids from the cell culture insert.
	<ol>
		<li>Make a hole in the middle of the membrane of the cell culture insert with a pair of dissecting forceps. Using dissecting scissors, make three cuts in the membrane from the hole in the middle to the edge of the cell culture insert, cutting between the organoids. This will result in three pieces of membrane, each with one organoid attached, which are still connected to the cell culture insert at their outer edge.</li>
		<li>Take hold of one of the pieces of membrane close to its outer edge with a pair of forceps and tear it loose from the cell culture insert. Place the piece of membrane with the attached organoid in a Petri dish. Add a few drops of Dulbecco&#39;s phosphate-buffered saline (DPBS) without calcium and magnesium (DPBS-/-) to the organoid to avoid dehydration. Repeat for the other two organoids.</li>
	</ol>
	</li>
	<li>Bisect the organoids by holding their membrane in place with forceps and cutting them in half with a double-edge stainless steel razor blade (a whole organoid is too large for the celom to accommodate at this stage of development). Gently push the two organoid halves off the membrane with a dura dissector. Discard the membrane and leave the organoids in DPBS-/- until transplantation. 
	NOTE: Prepare a maximum of three organoids at a time for transplantation to avoid stress to the organoids prior to transplantation. Ideally, one person prepares the organoids while another performs the transplantation.</li>
</ol>
2. Preparing chicken embryos for transplantation
<ol>
	<li>Incubate fertilized white leghorn eggs. Start the incubation of the eggs on kidney organoid differentiation day 7 + 8 to ensure the correct timing of the transplantation.
	<ol>
		<li>Place the fertilized white leghorn eggs (Gallus domesticus) horizontally on a holder (Figure 1A; day 0), marking the middle of the upward-facing side with a pencil. 
		NOTE: Either custom-made plastic holders or egg cartons can be used as holders to incubate the eggs.</li>
		<li>Place the holder with the eggs in a humidified incubator at 38 &#177; 1 &#186;C (Figure 1A; day 0).</li>
		<li>Incubate the eggs for 3 days, keeping the water basin in the incubator filled.</li>
	</ol>
	</li>
	<li>Create a window in the eggshell on day 3 of incubation.
	<ol>
		<li>On day 3 of incubation, place a small piece (~1 cm x 0.5 cm) of transparent tape on the pointed tip of the egg (small end). Make a small hole in the eggshell in the middle of the transparent tape by tapping it with the sharp end of a pair of dissecting scissors.</li>
		<li>Insert a 19 G needle on a 5 mL syringe into the hole at a 45&#176; angle, avoiding damage to the yolk sac, and aspirate 2-3 mL of albumen from the egg to lower the embryo inside the egg. Seal the hole with a second piece (~1 cm x 0.5 cm) of transparent tape.</li>
		<li>Place a large piece (~5 cm x 5 cm) of transparent tape on the pencil-marked, upward-facing side of the egg. Make a hole in the eggshell in the middle of the transparent tape by tapping it with the sharp end of a pair of dissecting scissors (Figure 1A; day 3).</li>
		<li>Starting from this hole, cut a small circular window in the eggshell using curved dissecting scissors. Look through this window to locate the embryo, then enlarge the window to optimize access to the embryo (Figure 1A; day 3).</li>
		<li>Remove any large pieces of eggshell that may have fallen on top of the embryo using forceps. Remove smaller pieces by placing a few drops of DPBS with calcium and magnesium (DPBS+/+) on the embryo with a plastic transfer pipette, then aspirating the DPBS+/+ with the eggshell into the pipette.</li>
		<li>Add three drops of DPBS+/+ supplemented with 0.5% penicillin/streptomycin to the egg using a plastic transfer pipette.</li>
		<li>Carefully seal the window with a large piece (~5 cm x 5 cm) of transparent tape before placing the egg back in the incubator until day 4 of incubation, when the embryo is in Hamburger-Hamilton stage 23-24 (HH 23-24)32. 
		NOTE: Sealing the window is very important to avoid dehydration and death of the embryo.</li>
		<li>Check the embryos daily for viability by looking at them through the tape (do not remove the tape to avoid dehydration). During these first days of incubation, the egg yolk color changes from bright to matte yellow upon embryo death. Discard deceased embryos.</li>
		<li>Keep the water basin in the incubator filled.</li>
	</ol>
	</li>
</ol>
3. Intracelomic transplantation on day 4 of incubation
<ol>
	<li>Gaining access to the celomic cavity
	<ol>
		<li>Cut the tape from the window with curved dissecting scissors.</li>
		<li>Place the egg under a dissecting microscope on a rubber holder or egg carton.</li>
		<li>The chicken embryo is now in HH 23-24 and lying on its left side, with its right side facing the viewer (Figure 1A; day 4). Locate the right wing and leg bud of the embryo, as the celom will be accessed between these two limb buds. In the area between the right wing and leg bud, create an opening consecutively in the vitelline membrane, the chorion, and the amnion, by holding them with two pairs of dissecting forceps and gently pulling them in opposite directions. 
		NOTE: The vitelline membrane is the first membrane that is encountered after opening the egg, and in some cases, is already damaged after making the window on day 3. If the embryo is rotated, lying on its right side with its left side facing the viewer (Figure 1A; day 4), it is necessary to turn it around to enable transplantation. To do this, make a large opening in the vitelline and chorion membrane, then carefully turn the embryo around using forceps.</li>
		<li>Check whether there is unobstructed access to the celomic cavity: gently take hold of the edge of the body wall between the wing and limb bud with a pair of dissecting forceps and pull it slightly toward the viewer. The celomic cavity must be clearly visible. Carefully insert a blunt but slim instrument (e.g., a blunt tungsten wire in a microscalpel holder) into the celomic cavity. 
		NOTE: If insertion of the blunt instrument into the celomic cavity is not possible, it means one or more of the membranes have not been properly opened.</li>
	</ol>
	</li>
	<li>Transplantation
	<ol>
		<li>Place half an organoid inside the egg on top of the allantois using a dura dissector.</li>
		<li>Using dissecting forceps, carefully take hold of the edge of the body wall and pull it slightly toward the viewer to make the opening to the celom visible. 
		NOTE: Avoid damaging the blood vessels in the body wall.</li>
		<li>Gently move the organoid toward and through the opening in the body wall into the celom with a blunt Tungsten wire in a microscalpel holder. Push the organoid slightly cranially to lodge it inside the celom. It is now visible just behind the wing bud (Figure 1A; day 4).</li>
		<li>Add three drops of DPBS+/+ to the egg using a plastic transfer pipette.</li>
		<li>Carefully seal the window with a large piece (~5 cm x 5 cm) of transparent tape before placing the egg back in the incubator until day 12 of incubation (8 days after transplantation).</li>
		<li>Keep checking the embryos daily for viability by looking at them through the tape (do not remove the tape to avoid dehydration). Discard deceased embryos. 
		NOTE: As the embryos and their chorioallantoic membranes grow, they become more clearly visible through the tape. A lack of movement by the embryo and collapsed or sparse blood vessels are a sign of embryo death.</li>
		<li>Check the water basin in the incubator daily and keep it filled.</li>
	</ol>
	</li>
</ol>
4. Injection of fluorescently labeled lectin
<ol>
	<li>Preparing for injection
	<ol>
		<li>Make glass microinjection needles by pulling glass microcapillaries in a micropipette puller with the following settings: Heat 533, Pull 60, Velocity 150, Time 200. While looking through the dissecting microscope, carefully break the tips off the microinjection needles using dissecting forceps to create an opening. 
		NOTE: The required settings for the micropipette puller may differ depending on the machine.</li>
		<li>Assemble the injection system. Take two pieces of 38 cm silicone tubing and connect them to each other by placing a 0.2 &#181;m filter between them. Insert a mouthpiece into the end of the tube that is connected with the filter outlet (silicone tube 1), and a connector to the end of the tube that is connected with the filter inlet (silicone tube 2). Finally, insert the microinjection needle into the connector (Figure 1B).</li>
		<li>Dilute fluorescently labeled lens culinaris agglutinin (LCA) with DPBS-/- to a concentration of 2.5 mg mL-1 in a 0.5 mL tube and spin down for ~30 s in a microcentrifuge to move the aggregates to the bottom of the tube.</li>
		<li>Pipette 20 &#181;L of LCA onto a piece of parafilm.</li>
		<li>Aspirate the 20 &#181;L of LCA from the parafilm into the microcapillary needle of the assembled injection system.</li>
	</ol>
	</li>
	<li>Injection
	<ol>
		<li>Cut the tape from the window with curved dissecting scissors. Place the egg under a dissecting microscope in a rubber holder.</li>
		<li>Evaluate the vasculature and locate the veins, which can be distinguished from the arteries by their slightly brighter red color (Figure 1A; day 12). To improve access to the vasculature, carefully enlarge the window by cutting with curved dissecting scissors. Select a vein for injection based on accessibility and size.</li>
		<li>Insert the tip of the microcapillary needle into the selected vein at a 0&#176;-20&#186; angle. Ensure the needle is in the vein by gently moving the tip from side to side. Gently and steadily blow into the injection system to inject the LCA (Figure 1A; day 12). 
		NOTE: If the needle in the vein is in the correct position, it should stay within the boundaries of the vein.</li>
		<li>Place the egg back in the incubator for 10 min to let the LCA circulate. 
		&#8203;NOTE: It is not necessary to seal the egg with tape during this time.</li>
	</ol>
	</li>
</ol>
5. Collecting transplanted organoids on day 12 of incubation
<ol>
	<li>Sacrificing the chicken embryo
	<ol>
		<li>Place the egg in a rubber holder on the bench. Cut the tape from the window with curved dissecting scissors. Then, cut through the membranes surrounding the embryo with curved dissecting scissors. 
		NOTE: A dissecting microscope is not required for this step.</li>
		<li>Scoop the embryo up from the egg with a perforated spoon and immediately decapitate the embryo using scissors. Place the body of the embryo in a Petri dish under the dissection microscope.</li>
	</ol>
	</li>
	<li>Locating and collecting organoids
	<ol>
		<li>Place the embryo on its back in the Petri dish and spread its limbs.</li>
		<li>Carefully open the abdominal wall of the embryo along the longitudinal axis using forceps.</li>
		<li>Locate the organoid inside the embryo. The organoid most frequently becomes attached to the right liver lobe, either at the caudal tip or cranially just below the rib cage (Figure 1A; day 12). It is therefore recommended to start by looking in these locations.</li>
		<li>Once the organoid is located, remove it from the embryo by cutting around it with micro scissors. Place the organoid and the chicken tissue that is inevitably attached to it in a Petri dish under the dissecting microscope. Remove as much chicken tissue as possible with a double-edge stainless steel razor blade.</li>
		<li>Process the organoid depending on the desired analysis.</li>
	</ol>
	</li>
</ol>
6. Whole-mount immunofluorescence staining
<ol>
	<li>Place a transplanted organoid in a 24-well plate and fix in 500 &#181;L of 4% paraformaldehyde (PFA) at 4 &#176;C for 24 h. Wash 3x with DPBS-/-.</li>
	<li>Permeabilize and block the organoid in 300 &#181;L of blocking solution (0.3% Triton-X in DPBS-/- containing 10% donkey serum) for 2 h at room temperature.</li>
	<li>Prepare the primary antibody mix: for one organoid, dilute primary antibodies NPHS1 (sheep-&#945;-human, dilution of 1:100), CD31 (mouse-&#945;-human, dilution of 1:100), and LTL (biotin-conjugated, dilution of 1:300) in 300 &#181;L of blocking solution. Add the antibody mix to the organoid and incubate for 72 h at 4 &#176;C.</li>
	<li>Wash 3x with 0.3% TritonX in DPBS-/-.</li>
	<li>Prepare the secondary antibody mix: for one organoid, dilute secondary antibodies donkey-&#945;-sheep Alexa Fluor 647 (dilution of 1:500), donkey-&#945;-mouse Alexa Fluor 488 (dilution of 1:500), and streptavidin Alexa Fluor 405 (dilution of 1:200) in 300 &#181;L of blocking solution. Add the secondary antibody mix to the organoid and incubate for 2-4 h at room temperature. Cover with aluminum foil to avoid exposure of the secondary antibodies to light.</li>
	<li>Wash 3x with DPBS-/-.</li>
	<li>Embed the organoid in ~30 &#181;L of mounting medium in a 35 mm glass bottom dish and allow to dry overnight at room temperature, covered with aluminum foil. Store at 4 &#176;C.</li>
	<li>Image using a confocal microscope.</li>
</ol>

<ol>
	<li>Taguchi, 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=Redefining+the+in+vivo+origin+of+metanephric+nephron+progenitors+enables+generation+of+complex+kidney+structures+from+pluripotent+stem+cells.">Redefining the in vivo origin of metanephric nephron progenitors enables generation of complex kidney structures from pluripotent stem cells.</a> Cell Stem Cell. 14 (1), 53-67 (2014).</li><li>Morizane, R., 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=Nephron+organoids+derived+from+human+pluripotent+stem+cells+model+kidney+development+and+injury.">Nephron organoids derived from human pluripotent stem cells model kidney development and injury.</a> Nature Biotechnology. 33 (11), 1193-1200 (2015).</li><li>Kim, Y. K., 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=Gene-edited+human+kidney+organoids+reveal+mechanisms+of+disease+in+podocyte+development.">Gene-edited human kidney organoids reveal mechanisms of disease in podocyte development.</a> Stem Cells. 35 (12), 2366-2378 (2017).</li><li>Takasato, 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=Kidney+organoids+from+human+iPS+cells+contain+multiple+lineages+and+model+human+nephrogenesis.">Kidney organoids from human iPS cells contain multiple lineages and model human nephrogenesis.</a> Nature. 526 (7574), 564-568 (2015).</li><li>Hale, L. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+organoid-derived+human+glomeruli+for+personalised+podocyte+disease+modelling+and+drug+screening.">3D organoid-derived human glomeruli for personalised podocyte disease modelling and drug screening.</a> Nature Communications. 9 (1), 5167 (2018).</li><li>Vanslambrouck, 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=Enhanced+metanephric+specification+to+functional+proximal+tubule+enables+toxicity+screening+and+infectious+disease+modelling+in+kidney+organoids.">Enhanced metanephric specification to functional proximal tubule enables toxicity screening and infectious disease modelling in kidney organoids.</a> Nature Communications. 13 (1), 5943 (2022).</li><li>Tanigawa, 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=Organoids+from+nephrotic+disease-derived+iPSCs+identify+impaired+NEPHRIN+localization+and+slit+diaphragm+formation+in+kidney+podocytes.">Organoids from nephrotic disease-derived iPSCs identify impaired NEPHRIN localization and slit diaphragm formation in kidney podocytes.</a> Stem Cell Reports. 11 (3), 727-740 (2018).</li><li>Forbes, T. 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=Patient-iPSC-derived+kidney+organoids+show+functional+validation+of+a+ciliopathic+renal+phenotype+and+reveal+underlying+pathogenetic+mechanisms.">Patient-iPSC-derived kidney organoids show functional validation of a ciliopathic renal phenotype and reveal underlying pathogenetic mechanisms.</a> American Journal of Human Genetics. 102 (5), 816-831 (2018).</li><li>Freedman, B. 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=Modelling+kidney+disease+with+CRISPR-mutant+kidney+organoids+derived+from+human+pluripotent+epiblast+spheroids.">Modelling kidney disease with CRISPR-mutant kidney organoids derived from human pluripotent epiblast spheroids.</a> Nature Communications. 6, 8715 (2015).</li><li>Cruz, N. 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=Organoid+cystogenesis+reveals+a+critical+role+of+microenvironment+in+human+polycystic+kidney+disease.">Organoid cystogenesis reveals a critical role of microenvironment in human polycystic kidney disease.</a> Nature Materials. 16 (11), 1112-1119 (2017).</li><li>Gupta, N., 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=Modeling+injury+and+repair+in+kidney+organoids+reveals+that+homologous+recombination+governs+tubular+intrinsic+repair.">Modeling injury and repair in kidney organoids reveals that homologous recombination governs tubular intrinsic repair.</a> Science Translational Medicine. 14 (634), eabj4772 (2022).</li><li>Hiratsuka, K., 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=Organoid-on-a-chip+model+of+human+ARPKD+reveals+mechanosensing+pathomechanisms+for+drug+discovery.">Organoid-on-a-chip model of human ARPKD reveals mechanosensing pathomechanisms for drug discovery.</a> Scencei Advances. 8 (38), eabq0866 (2022).</li><li>Dorison, 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=Kidney+organoids+generated+using+an+allelic+series+of+NPHS2+point+variants+reveal+distinct+intracellular+podocin+mistrafficking.">Kidney organoids generated using an allelic series of NPHS2 point variants reveal distinct intracellular podocin mistrafficking.</a> Journal of the American Society of Nephrology. , (2022).</li><li>Eremina, V., 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=Glomerular-specific+alterations+of+VEGF-A+expression+lead+to+distinct+congenital+and+acquired+renal+diseases.">Glomerular-specific alterations of VEGF-A expression lead to distinct congenital and acquired renal diseases.</a> The Journal of Clinical Investigation. 111 (5), 707-716 (2003).</li><li>Kitamoto, Y., Tokunaga, H., Tomita, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+endothelial+growth+factor+is+an+essential+molecule+for+mouse+kidney+development:+glomerulogenesis+and+nephrogenesis.">Vascular endothelial growth factor is an essential molecule for mouse kidney development: glomerulogenesis and nephrogenesis.</a> The Journal of Clinical Investigation. 99 (10), 2351-2357 (1997).</li><li>Sison, K., 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=Glomerular+structure+and+function+require+paracrine,+not+autocrine,+VEGF-VEGFR-2+signaling.">Glomerular structure and function require paracrine, not autocrine, VEGF-VEGFR-2 signaling.</a> Journal of the American Society of Nephrology. 21 (10), 1691-1701 (2010).</li><li>Ryan, A. R., 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=Vascular+deficiencies+in+renal+organoids+and+ex+vivo+kidney+organogenesis.">Vascular deficiencies in renal organoids and ex vivo kidney organogenesis.</a> Developmental Biology. 477, 98-116 (2021).</li><li>vanden Berg, C. 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=Renal+subcapsular+transplantation+of+PSC-derived+kidney+organoids+induces+neo-vasculogenesis+and+significant+glomerular+and+tubular+maturation+in+vivo.">Renal subcapsular transplantation of PSC-derived kidney organoids induces neo-vasculogenesis and significant glomerular and tubular maturation in vivo.</a> Stem Cell Reports. 10 (3), 751-765 (2018).</li><li>Sharmin, 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=Human+induced+pluripotent+stem+cell-derived+podocytes+mature+into+vascularized+glomeruli+upon+experimental+transplantation.">Human induced pluripotent stem cell-derived podocytes mature into vascularized glomeruli upon experimental transplantation.</a> Journal of the American Society of Nephrology. 27 (6), 1778-1791 (2016).</li><li>Bantounas, I., 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=Generation+of+functioning+nephrons+by+implanting+human+pluripotent+stem+cell-derived+kidney+progenitors.">Generation of functioning nephrons by implanting human pluripotent stem cell-derived kidney progenitors.</a> Stem Cell Reports. 10 (3), 766-779 (2018).</li><li>vanden Berg, C. W., Koudijs, A., Ritsma, L., Rabelink, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+assessment+of+size-selective+glomerular+sieving+in+transplanted+human+induced+pluripotent+stem+cell-derived+kidney+organoids.">In vivo assessment of size-selective glomerular sieving in transplanted human induced pluripotent stem cell-derived kidney organoids.</a> Journal of the American Society of Nephrology. 31 (5), 921-929 (2020).</li><li>Asai, R., Bressan, M., Mikawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Avians+as+a+model+system+of+vascular+development.">Avians as a model system of vascular development.</a> Methods in Molecular Biology. 2206, 103-127 (2021).</li><li>Jankovic, B. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunological+capacity+of+the+chicken+embryo.+I.+Relationship+between+the+maturation+of+lymphoid+tissues+and+the+occurrence+of+cell-mediated+immunity+in+the+developing+chicken+embryo.">Immunological capacity of the chicken embryo. I. Relationship between the maturation of lymphoid tissues and the occurrence of cell-mediated immunity in the developing chicken embryo.</a> Immunology. 29 (3), 497-508 (1975).</li><li>Alkie, T. N., 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=Development+of+innate+immunity+in+chicken+embryos+and+newly+hatched+chicks:+a+disease+control+perspective.">Development of innate immunity in chicken embryos and newly hatched chicks: a disease control perspective.</a> Avian Pathology. 48 (4), 288-310 (2019).</li><li>Rawles, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transplantation+of+normal+embryonic+tissues.">Transplantation of normal embryonic tissues.</a> Annalls of the New York Academy of Sciences. 55 (2), 302-312 (1952).</li><li>Rawles, M. 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+development+of+melanophores+from+embryonic+mouse+tissues+grown+in+the+coelom+of+chick+embryos.">The development of melanophores from embryonic mouse tissues grown in the coelom of chick embryos.</a> Proceedings of the National Academy of Sciences. 26 (12), 673-680 (1940).</li><li>Garreta, E., 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=Fine+tuning+the+extracellular+environment+accelerates+the+derivation+of+kidney+organoids+from+human+pluripotent+stem+cells.">Fine tuning the extracellular environment accelerates the derivation of kidney organoids from human pluripotent stem cells.</a> Nature Materials. 18 (4), 397-405 (2019).</li><li>Koning, 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=Vasculogenesis+in+kidney+organoids+upon+transplantation.">Vasculogenesis in kidney organoids upon transplantation.</a> NPJ Regenerative Medicine. 7 (1), 40 (2022).</li><li>Hamburger, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphogenetic+and+axial+self-differentiation+of+transplanted+limb+primordia+of+2-day+chick+embryos.">Morphogenetic and axial self-differentiation of transplanted limb primordia of 2-day chick embryos.</a> Journal of Experimental Zoology. 77 (3), 379-399 (1938).</li><li>Dossel, W. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+method+of+intracelomic+grafting.">New method of intracelomic grafting.</a> Science. 120 (3111), 262-263 (1954).</li><li>Takasato, M., Er, P. X., Chiu, H. S., Little, 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=Generation+of+kidney+organoids+from+human+pluripotent+stem+cells.">Generation of kidney organoids from human pluripotent stem cells.</a> Nature Protocols. 11 (9), 1681-1692 (2016).</li><li>Hamburger, V., Hamilton, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+series+of+normal+stages+in+the+development+of+the+chick+embryo.">A series of normal stages in the development of the chick embryo.</a> Developmental Dynamics. 195 (4), 231-272 (1992).</li><li>Aleksandrowicz, E., Herr, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ethical+euthanasia+and+short-term+anesthesia+of+the+chick+embryo.">Ethical euthanasia and short-term anesthesia of the chick embryo.</a> ALTEX. 32 (2), 143-147 (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ACUC.">ACUC.</a> Guideline: The Use and Euthanasia Procedures of Chicken/Avian Embryos. , (2012).</li></ol>

The authors have no conflicts of interest to disclose.

In this manuscript, a protocol for intracelomic transplantation of hiPSC-derived kidney organoids in chicken embryos is demonstrated. Upon transplantation, organoids are vascularized by perfused blood vessels that consist of a combination of human organoid-derived and chicken-derived ECs. These are spread throughout the organoid and invade the glomerular structures, enabling interaction between the ECs and podocytes. It was previously shown that this leads to enhanced maturation of the organoid glomerular and tubular str...

Human induced pluripotent stem cell (hiPSC)-derived kidney organoids have been shown to have potential for developmental studies1,2,3,4, toxicity screening5,6, and disease modeling5,7,8,9,10,11,12,13. However, their applicability for these and eventual clinical transplantation purposes is limited by the lack of a vascular network. During embryonic kidney development, podocytes, mesangial cells, and vascular endothelial cells (ECs) interact to form the intricate structure of the glomerulus. Without this interaction, the glomerular filtration barrier, consisting of podocytes, the glomerular basement membrane (GBM), and ECs, cannot develop properly14,15,16. Although kidney organoids in vitro do contain some ECs, these fail to form a proper vascular network and diminish over time17. It is therefore not surprising that the organoids remain immature. Transplantation in mice induces vascularization and maturation of the kidney organoids18,19,20,21. Unfortunately, this is a labor-intensive process that is unsuitable for the analysis of large numbers of organoids.
Chicken embryos have been used to study vascularization and development for over a century22. They are easily accessible, require low maintenance, lack a fully functional immune system, and can develop normally after opening the eggshell23,24,25,26. The transplantation of organoids on their chorioallantoic membrane (CAM) has been shown to lead to vascularization27. However, the duration of transplantation on the CAM, as well as the level of maturation of the graft, are limited by CAM formation, which takes until embryonic day 7 to complete. Therefore, a method was recently developed to efficiently vascularize and mature kidney organoids through intracelomic transplantation in chicken embryos28. The celomic cavity of chicken embryos has been known since the 1930s to be a favorable environment for the differentiation of embryonic tissues29,30. It can be accessed early in embryonic development and allows for relatively unlimited expansion of the graft in all directions.
This paper outlines a protocol for the transplantation of hiPSC-derived kidney organoids in the celomic cavity of day 4 chicken embryos. This method induces vascularization and enhanced maturation of the organoids within 8 days. Injection of fluorescently labeled lens culinaris agglutinin (LCA) prior to sacrificing the embryos enables visualization of perfused blood vessels within the organoids through confocal microscopy.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.2 &#181;m filter: Whatman Puradisc 30 syringe filter 0.2 &#181;m</td>
			<td>Whatman</td>
			<td>10462200</td>
			<td></td>
		</tr>
		<tr>
			<td>35 mm glass bottom dishes&#160;</td>
			<td>MatTek Corporation</td>
			<td>P35G-1.5-14-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Aspirator tube assemblies for calibrated microcapillary pipettes</td>
			<td>Sigma-Aldrich</td>
			<td>A5177-5EA</td>
			<td>Contains silicone tubes, mouth piece and connector</td>
		</tr>
		<tr>
			<td>Confocal microscope: Leica White Light Laser Confocal Microscope&#160;</td>
			<td>Leica</td>
			<td>TCS SP8</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting forceps, simple type. Titanium, curved, with fine sharp tips</td>
			<td>Hammacher Karl</td>
			<td>HAMMHTC091-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting forceps, simple type. Titanium, straight, with fine sharp tips</td>
			<td>Hammacher Karl</td>
			<td>HAMMHTC090-11</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting microscope&#160;</td>
			<td>Wild Heerbrugg</td>
			<td>355110</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting scissors, curved, OP-special, extra sharp/sharp</td>
			<td>Hammacher Karl</td>
			<td>HAMMHSB391-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Donkey serum</td>
			<td>Sigma-Aldrich</td>
			<td>D9663</td>
			<td></td>
		</tr>
		<tr>
			<td>Donkey-&#945;-mouse Alexa Fluor 488</td>
			<td>ThermoFisher Scientific</td>
			<td>A-212-02</td>
			<td>dilution 1:500</td>
		</tr>
		<tr>
			<td>Donkey-&#945;-sheep Alexa Fluor 647</td>
			<td>ThermoFisher Scientific</td>
			<td>A-21448</td>
			<td>dilution 1:500</td>
		</tr>
		<tr>
			<td>Double edged stainless steel razor blades</td>
			<td>Electron Microsopy Sciences</td>
			<td>72000</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS, calcium, magnesium (DPBS-/-)</td>
			<td>ThermoFisher Scientific</td>
			<td>14040133</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS, no calcium, no magnesium (DPBS+/+)</td>
			<td>ThermoFisher Scientific</td>
			<td>14190094</td>
			<td></td>
		</tr>
		<tr>
			<td>Egg cartons or custom made egg holders&#160;</td>
			<td>NA</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Fertilized white leghorn eggs (Gallus Gallus Domesticus)&#160;</td>
			<td>Drost Loosdrecht B.V.</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Elbanton BV</td>
			<td>ET-3 combi</td>
			<td></td>
		</tr>
		<tr>
			<td>Lotus Tetragonolobus lectin (LTL) Biotinylated</td>
			<td>Vector Laboratories</td>
			<td>B-1325</td>
			<td>dilution 1:300</td>
		</tr>
		<tr>
			<td>Micro scissors, straight, sharp/sharp, cutting length 10 mm</td>
			<td>Hammacher Karl</td>
			<td>HAMMHSB500-09</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcapillaries: Thin wall glass capillaries 1.5 mm, filament</td>
			<td>World Precision Instruments</td>
			<td>TW150F-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette puller</td>
			<td>Sutter Instrument Company</td>
			<td>Model P-97</td>
			<td>We use the following settings: Heat 533, Pull 60, Velocity 150, Time 200</td>
		</tr>
		<tr>
			<td>Microscalpel holder: Castroviejo blade and pins holder, 12 cm, round handle, conical 10 mm jaws.</td>
			<td>Euronexia</td>
			<td>L-120</td>
			<td></td>
		</tr>
		<tr>
			<td>Mounting medium: Prolong Gold Antifade Mountant&#160;</td>
			<td>ThermoFisher Scientific</td>
			<td>P36930</td>
			<td></td>
		</tr>
		<tr>
			<td>Olivecrona dura dissector 18 cm&#160;</td>
			<td>Reda</td>
			<td>41146-18</td>
			<td></td>
		</tr>
		<tr>
			<td>Parafilm&#160;</td>
			<td>Heathrow Scientific</td>
			<td>HS234526B</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-streptomycin 5,000 U/mL</td>
			<td>ThermoFisher Scientific</td>
			<td>15070063</td>
			<td></td>
		</tr>
		<tr>
			<td>Perforated spoon&#160;</td>
			<td>Euronexia</td>
			<td>S-20-P</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish 60 x 15 mm&#160;</td>
			<td>CELLSTAR</td>
			<td>628160</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic transfer pipettes&#160;</td>
			<td>ThermoFisher Scientific</td>
			<td>PP89SB</td>
			<td></td>
		</tr>
		<tr>
			<td>Purified mouse anti-human CD31 antibody</td>
			<td>BD Biosciences</td>
			<td>555444</td>
			<td>dilution 1:100</td>
		</tr>
		<tr>
			<td>Rhodamine labeled Lens Culinaris Agglutinin (LCA)</td>
			<td>Vector Laboratories</td>
			<td>RL-1042</td>
			<td>This product has recently been discontinued. Vectorlabs does still produce Dylight 649 labeled LCA (DL-1048-1) and fluorescein labeled LCA (FL-1041-5)</td>
		</tr>
		<tr>
			<td>Sheep anti-human NPHS1 antibody</td>
			<td>R&#38;D systems</td>
			<td>AF4269</td>
			<td>dilution 1:100</td>
		</tr>
		<tr>
			<td>Sterile hypodermic needles, 19 G</td>
			<td>BD microlance</td>
			<td>301500</td>
			<td></td>
		</tr>
		<tr>
			<td>Streptavidin Alexa Fluor 405</td>
			<td>ThermoFisher Scientific</td>
			<td>S32351</td>
			<td>dilution 1:200</td>
		</tr>
		<tr>
			<td>Syringe 5 mL</td>
			<td>BD Emerald</td>
			<td>307731</td>
			<td></td>
		</tr>
		<tr>
			<td>Transparent tape&#160;</td>
			<td>Tesa</td>
			<td>4124</td>
			<td>Available at most hardware stores</td>
		</tr>
		<tr>
			<td>Triton X</td>
			<td>Sigma-Aldrich</td>
			<td>T9284</td>
			<td></td>
		</tr>
		<tr>
			<td>Tungsten wire, 0.25 mm dia&#160;</td>
			<td>ThermoFisher Scientific</td>
			<td>010404.H2</td>
			<td></td>
		</tr>
	</tbody>
</table>

efficient vascularization of kidney organoids through intracelomic transplantation in chicken embryos

Kidney organoids derived from human induced pluripotent stem cells contain nephron-like structures that resemble those in the adult kidney to a certain degree. Unfortunately, their clinical applicability is hampered by the lack of a functional vasculature and consequently limited maturation in vitro. The transplantation of kidney organoids in the celomic cavity of chicken embryos induces vascularization by perfused blood vessels, including the formation of glomerular capillaries, and enhances their maturation. This technique is very efficient, allowing for the transplantation and analysis of large numbers of organoids. This paper describes a detailed protocol for the intracelomic transplantation of kidney organoids in chicken embryos, followed by the injection of fluorescently labeled lectin to stain the perfused vasculature, and the collection of transplanted organoids for imaging analysis. This method can be used to induce and study organoid vascularization and maturation to find clues for enhancing these processes in vitro and improve disease modeling.

The method and timeline for the differentiation of hiPSCs to kidney organoids, incubation of fertilized chicken eggs, transplantation of kidney organoids, injection of LCA, and collection of the organoids are summarized in Figure 1A. It is important to coordinate the timing of organoid differentiation and chicken egg incubation, starting differentiation 15 days before incubation.&#160;The actions on day 0, 3, 4, and 12 of incubation are illustrated by photographs below the timeline. Organoid...

Watch this Scientific Journal Video about Efficient Vascularization of Kidney Organoids through Intracelomic Transplantation in Chicken Embryos at JoVE.com

Efficient Vascularization of Kidney Organoids through Intracelomic Transplantation in Chicken Embryos

Here, we present a detailed protocol for the transplantation of kidney organoids in the celomic cavity of chicken embryos. This method induces vascularization and enhanced maturation of the organoids within 8 days and can be used to study these processes in an efficient manner.

Kidney organoids derived from human induced pluripotent stem cells contain nephron-like structures that resemble those in the adult kidney to a certain ...

efficient-vascularization-kidney-organoids-through-intracelomic

Research

JoVE Journal

Developmental Biology

1.6K Views.  Leiden University Medical Center. Here, we present a detailed protocol for the transplantation of kidney organoids in the celomic cavity of chicken embryos. This method induces vascularization and enhanced maturation of the organoids within 8 days and can be used to study these processes in an efficient manner.

Video: Efficient Vascularization of Kidney Organoids through Intracelomic Transplantation in Chicken Embryos

Whole Retinal Explants from Chicken Embryos for Electroporation and Chemical Reagent Treatments

The retina is a good model for the developing central nervous system. The large size of the eye and most importantly the accessibility for experimental manipulations in ovo/in vivo makes the chicken embryonic retina a versatile and very efficient experimental model. Although the chicken retina is easy to target in ovo by intraocular injections or electroporation, the effective and exact concentration of the reagents within the retina may be difficult to fully control. This may be due to variations of the exact injection site, leakage from the eye or uneven diffusion of the substances. Furthermore, the frequency of malformations and mortality after invasive manipulations such as electroporation is rather high.
This protocol describes an ex ovo technique for culturing whole retinal explants from chicken embryos and provides a method for controlled exposure of the retina to reagents. The protocol describes how to dissect, experimentally manipulate, and culture whole retinal explants from chicken embryos. The explants can be cultured for approximately 24 hr and be subjected to different manipulations such as electroporation. The major advantages are that the experiment is not dependent on the survival of the embryo and that the concentration of the introduced reagent can be varied and controlled in order to determine and optimize the effective concentration. Furthermore, the technique is rapid, cheap and together with its high experimental success rate, it ensures reproducible results. It should be emphasized that it serves as an excellent complement to experiments performed in ovo.

This protocol describes a method to dissect, experimentally manipulate and culture whole retinal explants from chicken embryos. The explant cultures are useful when high success rate, efficacy and reproducibility are needed to test the effects of plasmids for electroporation and/or reagent substances, i.e., enzymatic inhibitors.

The retina is a good model for the developing central nervous system. The large size of the eye and most importantly the accessibility for experimental ...

Technique to Target Microinjection to the Developing Xenopus Kidney

The embryonic kidney of Xenopus&#160;laevis (frog), the pronephros, consists of a single nephron, and can be used as a model for kidney disease. Xenopus embryos are large, develop externally, and can be easily manipulated by microinjection or surgical procedures. In addition, fate maps have been established for early Xenopus embryos. Targeted microinjection into the individual blastomere that will eventually give rise to an organ or tissue of interest can be used to selectively overexpress or knock down gene expression within this restricted region, decreasing secondary effects in the rest of the developing embryo. In this protocol, we describe how to utilize established Xenopus fate maps to target the developing Xenopus kidney (the pronephros), through microinjection into specific blastomere of 4- and 8-cell embryos. Injection of lineage tracers allows verification of the specific targeting of the injection. After embryos have developed to stage 38 - 40, whole-mount immunostaining is used to visualize pronephric development, and the contribution by targeted cells to the pronephros can be assessed. The same technique can be adapted to target other tissue types in addition to the pronephros.

Technique to Target Microinjection to the Developing Xenopus Kidney

Here, we present a protocol to use fate maps and lineage tracers to target injections into individual blastomeres that give rise to the kidney of Xenopus laevis embryos.

The embryonic kidney of Xenopus&#160;laevis (frog), the pronephros, consists of a single nephron, and can be used as a model for kidney disease. Xenopus ...

An Efficient Method to Obtain Dedifferentiated Fat Cells

Tissue engineering and cell therapy hold great promise clinically. In this regard, multipotent cells, such as mesenchymal stem cells (MSCs), may be used therapeutically, in the near future, to restore function to damaged organs. Nevertheless, several technical issues, including the highly invasive procedure of isolating MSCs and the inefficiency surrounding their amplification, currently hamper the potential clinical use of these therapeutic modalities. Herein, we introduce a highly efficient method for the generation of dedifferentiated fat cells (DFAT), MSC-like cells. Interestingly, DFAT cells can be differentiated into several cell types including adipogenic, osteogenic, and chondrogenic cells. Although other groups have previously presented various methods for generating DFAT cells from mature adipose tissue, our method allows us to produce DFAT cells more efficiently. In this regard, we demonstrate that DFAT culture medium (DCM), supplemented with 20% FBS, is more effective in generating DFAT cells than DMEM, supplemented with 20% FBS. Additionally, the DFAT cells produced by our cell culture method can be redifferentiated into several tissue types. As such, a very interesting and useful model for the study of tissue dedifferentiation is presented.

We have modified the conditions for DFAT cell generation and provide herein information regarding the use of an improved growth medium for the production of these cells.

Tissue engineering and cell therapy hold great promise clinically. In this regard, multipotent cells, such as mesenchymal stem cells (MSCs), may be used ...

In Ovo Electroporation in the Chicken Auditory Brainstem

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that the chicken embryo is an effective research model for studying basic biological functions of auditory system development. More recently, the chicken embryo has become particularly valuable in studying gene expression, regulation and function associated with hearing. In ovo electroporation can be used to target auditory brainstem regions responsible for highly specialized auditory functions. These regions include the chicken nucleus magnocellularis (NM) and nucleus laminaris (NL). NM and NL neurons arise from distinct precursors of rhombomeres 5 and 6 (R5/R6). Here, we present in ovo electroporation of plasmid-encoded genes to study gene-related properties in these regions. We show a method for spatial and temporal control of gene expression that promote either gain or loss of functional phenotypes. By targeting auditory neural progenitor regions associated with R5/R6, we show plasmid transfection in NM and NL. Temporal regulation of gene expression can be achieved by adopting a tet-on vector system. This is a drug inducible procedure that expresses the genes of interest in the presence of doxycycline (Dox). The in ovo electroporation technique &#8211; together with either biochemical, pharmacological, and or in vivo functional assays &#8211; provides an innovative approach to study auditory neuron development and associated pathophysiological phenomena.

In Ovo Electroporation in the Chicken Auditory Brainstem

Auditory brainstem neurons of avians and mammals are specialized for fast neural encoding, a fundamental process for normal hearing functions. These neurons arise from distinct precursors of embryonic hindbrain. We present techniques utilizing electroporation to express genes in the hindbrain of chicken embryos to study gene function during auditory development.

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that ...

Tracing Gene Expression Through Detection of &#946;-galactosidase Activity in Whole Mouse Embryos

The Escherichia coli LacZ gene, encoding &#946;-galactosidase, is largely used as a reporter for gene expression and as a tracer in cell lineage studies. The classical histochemical reaction is based on the hydrolysis of the substrate X-gal in combination with ferric and ferrous ions, which produces an insoluble blue precipitate that is easy to visualize. Therefore, &#946;-galactosidase activity serves as a marker for the expression pattern of the gene of interest as the development proceeds. Here we describe the standard protocol for the detection of &#946;-galactosidase activity in early whole mouse embryos and the subsequent method for paraffin sectioning and counterstaining. Additionally, a procedure for clarifying whole embryos is provided to better visualize X-gal staining in deeper regions of the embryo. Consistent results are obtained by performing this procedure, although optimization of reaction conditions is needed to minimize background activity. Limitations in the assay should be also considered, particularly regarding the size of the embryo in whole mount staining. Our protocol provides a sensitive and a reliable method for &#946;-galactosidase detection during the mouse development that can be further applied to the cryostat sections as well as whole organs. Thus, the dynamic gene expression patterns throughout development can be easily analyzed by using this protocol in whole embryos, but also detailed expression at the cellular level can be assessed after paraffin sectioning.

Tracing Gene Expression Through Detection of &amp;#946;-galactosidase Activity in Whole Mouse Embryos

Here we describe the standard protocol for the detection of &#946;-galactosidase activity in early whole mouse embryos and the method for paraffin sectioning and counterstaining. This is an easy and quick procedure to monitor gene expression during development that can also be applied to tissue sections, organs or cultured cells.

The Escherichia coli LacZ gene, encoding &#946;-galactosidase, is largely used as a reporter for gene expression and as a tracer in cell lineage studies. ...

Fast and Efficient Expression of Multiple Proteins in Avian Embryos Using mRNA Electroporation

We report that mRNA electroporation permits fluorescent proteins to label cells in living quail embryos more quickly and broadly than DNA electroporation. The high transfection efficiency permits at least 4 distinct mRNAs to be co-transfected with ~87% efficiency. Most of the electroporated mRNAs are degraded during the first 2 h post-electroporation, permitting time-sensitive experiments to be carried out in the developing embryo. Finally, we describe how to dynamically image live embryos electroporated with mRNAs that encode various subcellular targeted fluorescent proteins.

We report messenger RNA (mRNA) electroporation as a method that permits fast and efficient expression of multiple proteins in the quail embryo model system. This method can be used to fluorescently label cells and record their in vivo movements by time-lapse microscopy shortly after electroporation.

We report that mRNA electroporation permits fluorescent proteins to label cells in living quail embryos more quickly and broadly than DNA electroporation. ...

A Simplified Method for Generating Kidney Organoids from Human Pluripotent Stem Cells

Kidney organoids generated from hPSCs have provided an unlimited source of renal tissue. Human kidney organoids are an invaluable tool for studying kidney disease and injury, developing cell-based therapies, and testing new therapeutics. For such applications, large numbers of uniform organoids and highly reproducible assays are needed. We have built upon our previously published kidney organoid protocol to improve the overall health of the organoids. This simple, robust 3D protocol involves the formation of uniform embryoid bodies in minimum component medium containing lipids, insulin-transferrin-selenium-ethanolamine supplement and polyvinyl alcohol with GSK3 inhibitor (CHIR99021) for 3 days, followed by culture in knock-out serum replacement (KOSR)-containing medium. In addition, agitating assays allows for reduction in clumping of the embryoid bodies and maintaining a uniform size, which is important for reducing variability between organoids. Overall, the protocol provides a fast, efficient, and cost-effective method for generating large quantities of kidney organoids.

Here we describe a protocol to generate kidney organoids from human pluripotent stem cells (hPSCs). This protocol generates kidney organoids within two weeks. The resulting kidney organoids can be cultured in large-scale spinner flasks or multi-well magnetic stir plates for parallel drug-testing approaches.

Kidney organoids generated from hPSCs have provided an unlimited source of renal tissue. Human kidney organoids are an invaluable tool for studying kidney ...

A Simple and Effective Transplantation Device for Zebrafish Embryos

Classical embryological manipulations, such as removing cells and transplanting cells within or between embryos, are powerful techniques to study complex developmental processes. Zebrafish embryos are ideally suited for these manipulations since they are easily accessible, relatively large in size, and transparent. However, previously developed devices for cell removal and transplantation are cumbersome to use or expensive to purchase. In contrast, the transplantation device presented here is economical, easy to assemble, and simple to use. In this protocol, we first introduce the handling of the transplantation device as well as its assembly from commercially and widely available parts. We then present three applications for its use: generation of ectopic clones to study signal dispersal from localized sources, extirpation of cells to produce size-reduced embryos, and germline transplantation to generate maternal-zygotic mutants. Finally, we show that the tool can also be used for embryological manipulations in other species such as the Japanese rice fish medaka.

Embryological manipulations such as extirpation and transplantation of cells are important tools to study early development. This protocol describes a simple and effective transplantation device to perform these manipulations in zebrafish embryos.

Classical embryological manipulations, such as removing cells and transplanting cells within or between embryos, are powerful techniques to study complex ...

In Ovo Intravascular Injection in Chicken Embryos

As a classical model system of embryo biology, the chicken embryo has been used to investigate embryonic development and differentiation. Delivering exogenous materials into chicken embryos has a great advantage for studying gene function, transgenic breeding, and chimera preparation during embryonic development. Here we show the method of in ovo intravascular injection whereby exogenous materials such as plasmid vectors or modified primordial germ cells (PGCs) can be transferred into donor chicken embryos at early developmental stages. The results show that the intravascular injection through the dorsal aorta and head allows injected materials to diffuse into the whole embryo through the blood circulatory system. In the presented protocol, the efficacy of exogenous plasmid and lentiviral vector introduction, and the colonization of injected exogenous PGCs in the recipient gonad, were determined by observing fluorescence in the embryos. This article describes detailed procedures of this method, thereby providing an excellent approach to studying gene function, embryo and developmental biology, and gonad-chimeric chicken production. In conclusion, this article will allow researchers to perform in ovo intravascular injection of exogenous materials into chicken embryos with great success and reproducibility.

In Ovo Intravascular Injection in Chicken Embryos

The overall goal of this paper is to describe how to perform in ovo intracellular injection of exogenous materials into chicken embryos. This approach is very useful to study the developmental biology of chicken embryos.

As a classical model system of embryo biology, the chicken embryo has been used to investigate embryonic development and differentiation. Delivering ...

Rapid and Efficient Spatiotemporal Monitoring of Normal and Aberrant Cytosine Methylation within Intact Zebrafish Embryos

Cytosine methylation is highly conserved across vertebrate species and, as a key driver of epigenetic programming and chromatin state, plays a critical role in early embryonic development. Enzymatic modifications drive active methylation and demethylation of cytosine into 5-methylcytosine (5-mC) and subsequent oxidation of 5-mC into 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine. Epigenetic reprogramming is a critical period during in utero development, and maternal exposure to chemicals has the potential to reprogram the epigenome within offspring. This can potentially cause adverse outcomes such as immediate phenotypic consequences, long-term effects on adult disease susceptibility, and transgenerational effects of inherited epigenetic marks. Although bisulfite-based sequencing enables investigators to interrogate cytosine methylation at base-pair resolution, sequencing-based approaches are cost-prohibitive and, as such, preclude the ability to monitor cytosine methylation across developmental stages, multiple concentrations per chemical, and replicate embryos per treatment. Due to the ease of automated in vivo imaging, genetic manipulations, rapid ex utero development time, and husbandry during embryogenesis, zebrafish embryos continue to be used as a physiologically intact model for uncovering xenobiotic-mediated pathways that contribute to adverse outcomes during early embryonic development. Therefore, using commercially available 5-mC-specific antibodies, we describe a cost-effective strategy for rapid and efficient spatiotemporal monitoring of cytosine methylation within individual, intact zebrafish embryos by leveraging whole-mount immunohistochemistry, automated high-content imaging, and efficient data processing using programming language prior to statistical analysis. To current knowledge, this method is the first to successfully detect and quantify 5-mC levels in situ within zebrafish embryos during early development. The method enables the detection of DNA methylation within the cell mass and also has the ability to detect cytosine methylation of yolk-localized maternal mRNAs during the maternal-to-zygotic transition. Overall, this method will be useful for the rapid identification of chemicals that have the potential to disrupt cytosine methylation in situ during epigenetic reprogramming.

This paper describes a protocol for the rapid and efficient spatiotemporal monitoring of normal and aberrant cytosine methylation within intact zebrafish embryos.

Cytosine methylation is highly conserved across vertebrate species and, as a key driver of epigenetic programming and chromatin state, plays a critical ...