Name: in vitro three-dimensional sprouting assay of angiogenesis using mouse embryonic stem cells for vascular disease modeling and drug testing
Uploaded: 2021-05-11T14:30:00
Description: Watch this Scientific Journal Video about In Vitro Three-Dimensional Sprouting Assay of Angiogenesis Using Mouse Embryonic Stem Cells for Vascular Disease Modeling and Drug Testing at JoVE.com

This work was supported by grants from the Nederlandse organisatie voor gezondheidsonderzoek en zorginnovatie (ZonMW 446002501), Health Holland (LSHM19057-H040), Leading Fellows Programme Marie Sk&#322;odowska-Curie COFUND, and by the Association Maladie de Rendu-Osler (AMRO).

1. Media preparation and culture of mESC
<ol>
	<li>Prepare conditioned medium +/- (CM+/-) using the supplement 1x Glasgow MEM (G-MEM BHK-21) medium with 10% (vol/vol) heat-inactivated Fetal Bovine Serum (FBS), 0.05 mM &#946;-mercaptoethanol, 1x non-essential amino acids (NEAA 1x), 2 mM L-glutamine, and 1 mM sodium pyruvate.</li>
	<li>Prepare conditioned medium +/+ (CM+/+) using the supplement CM+/- medium with Leukemia Inhibitory Factor (LIF) (1,500 U/mL) and 0.1 mM &#946;-mercaptoethanol.</li>
	<li>Prepare conditioned...

<ol>
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This protocol describes an unbiased, robust, and reproducible 3D EB-based vascular sprouting assay that is amenable to screening for drugs and genes modulating angiogenesis. This method offers advantages over many widely used two dimensional (2D) assays using endothelial cell cultures such as Human Umbilical Vein Endothelial Cells (HUVECs) to monitor migration (lateral scratch assay or the Boyden chamber assay)22,23&#160;or proliferation (counting cell number, de...

In the past three decades, target-based drug discovery (TDD) has been widely employed in drug discovery by the pharmaceutical industry. TDD incorporates a defined molecular target playing an important role in a disease and relies on the development of relatively simple cell culture systems and readouts for drug screening1. Most typical disease models used in TDD programs include traditional cell culture methods such as cancer cells or immortalized cell lines grown within artificial environments and non-physiological substrates. Although many of these models have provided viable tools for identifying successful drug candidates, the use of such systems can be questionable owing to their poor disease relevance2.
For most diseases, the underlying mechanisms are indeed complex and various cell types, independent signaling pathways, and multiple sets of genes are often found to contribute to a specific disease phenotype. This is also true for inherited diseases where the primary cause is a mutation in one single gene. With the recent advent of human induced pluripotent stem cell (iPSC) technologies and gene editing tools, it is now possible to generate 3D organoids and organ-on-chip disease models that could better recapitulate the in vivo human complexity3,4. The development of such technologies is associated with a resurgence in interest in phenotypic drug discovery (PDD) programs1. PDD can be compared to empirical screening, as they do not rely on knowledge of the identity of a specific drug target or a hypothesis about its role in disease. The PDD approach is now increasingly recognized to strongly contribute to the discovery of first-in-class drugs5. Because the development of human organoid and organ-on-chip technologies is still in its infancy, it is expected that iPSC models (complemented with innovative imaging and machine-learning tools6,7) will provide, in the near future, multiple novel complex cell-based disease models for drug screening and associated PDD programs to overcome the poor productivity of the TDD approach8,9.
While human organoid and organ-on-chip models can provide important insights into disease complexity and to the identification of novel drugs, bringing drugs into new clinical practice also strongly relies on data from animal models to assess their efficacy and safety. Among them, genetically modified mice are certainly the most preferred mammalian models. They have many advantages as they have a relatively short generation time for mammals, have many similar phenotypes to human diseases, and can be easily genetically manipulated. They are therefore extensively used in drug discovery programs10. However, bridging the gap between mice and humans remains an important challenge11. The development of in vitro mouse models equivalent to human organoid and organ-on-chip models could at least partially fill this gap as it will allow direct drug efficacy and safety comparisons between in vivo mouse and in vitro human data.
Here, a vascular sprouting assay in mouse embryoid bodies (EBs) is described. Blood vessels are composed of endothelial cells (inner lining of vessel walls), mural cells (vascular smooth muscle cells&#160;and pericytes)12. This protocol is based on the differentiation of mouse embryonic stem cells (mESCs) into vascularized EBs using hanging droplets that recapitulate de novo endothelial cell and mural cell differentiation13,14. Mouse ESCs can be easily established in culture from isolated day 3.5 mouse blastocysts having different genetic backgrounds15. They also provide possibilities for clonal analysis, lineage tracing, and can be easily genetically manipulated to generate disease models13,16.
As blood vessels nourish all organs, it is not surprising that many diseases if not all, are associated with changes in the microvasculature. In pathological conditions, endothelial cells can adopt an activated state or can become dysfunctional resulting in mural cell death or migration away from blood vessels. These can result in excessive angiogenesis or in vessel rarefaction, can induce abnormal blood flow and defective blood vessel barrier leading to immune cell extravasation, and inflammation12,17,18,19. Research for the development of drugs modulating blood vessels is, therefore&#160;high, and multiple molecular players and concepts have already been identified for therapeutic targeting. In this context, the protocol described is particularly suitable for building disease models and for drug testing as it recapitulates key features of in vivo sprouting angiogenesis, including endothelial tip and stalk cell selection, endothelial cell migration and proliferation, endothelial cell guidance, tube formation, and mural cell recruitment. It also shows similarities with recently described 3D vascular assays based on human iPSC technologies20.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2-mercaptoethanol</td>
			<td>Milipore, Merck</td>
			<td>805740</td>
			<td>Biohazard: adequate safety instructions should be taken when handling</td>
		</tr>
		<tr>
			<td>Agar Noble</td>
			<td>Difco, BD Pharmigen</td>
			<td>214220</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluo 555 goat anti rat IgG</td>
			<td>Life technologies</td>
			<td>A21434</td>
			<td></td>
		</tr>
		<tr>
			<td>APC conjugated rat anti-mouse PECAM-1 antibody (clone MEC13.3)</td>
			<td>BD Biosciences</td>
			<td>551262</td>
			<td></td>
		</tr>
		<tr>
			<td>APC Rat IgG2a &#954; Isotype Control (Clone&#160; R35-95)</td>
			<td>BD Biosciences</td>
			<td>553932</td>
			<td></td>
		</tr>
		<tr>
			<td>Axiovert 25 inverted phase contrast tissue culture microscope</td>
			<td>ZEISS</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Basic Fibroblast Growth Factor-2 (bFGF)</td>
			<td>Peprotech</td>
			<td>450-33</td>
			<td></td>
		</tr>
		<tr>
			<td>Benchtop Centrifuge, Allegra X-15R</td>
			<td>Beckman Coulter</td>
			<td>392932</td>
			<td></td>
		</tr>
		<tr>
			<td>Biosafety cabinet BioVanguard (Green Line)</td>
			<td>Telstar</td>
			<td>133H401001</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA)</td>
			<td>Sigma-Aldrich</td>
			<td>A9418</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell counting chamber, Buerker, 0.100mm</td>
			<td>Marienfeld</td>
			<td>640211</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture dishes 60 x 15mm</td>
			<td>Corning</td>
			<td>353802</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture dishes, 35 x 10 mm</td>
			<td>Corning</td>
			<td>353801</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture plates 12-well</td>
			<td>Corning</td>
			<td>3512</td>
			<td></td>
		</tr>
		<tr>
			<td>CFX96 Touch Real-Time PCR Detection System</td>
			<td>Biorad</td>
			<td>1855196</td>
			<td></td>
		</tr>
		<tr>
			<td>Chicken serum</td>
			<td>Sigma-Aldrich</td>
			<td>C5405</td>
			<td></td>
		</tr>
		<tr>
			<td>CHIR-99021 (CT99021) HCl</td>
			<td>Selleckchem</td>
			<td>S2924</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagen I, High Concentration, Rat Tail, 100mg</td>
			<td>Corning</td>
			<td>354249</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase A</td>
			<td>Roche</td>
			<td>10103586001</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal Laser Scanning Microscope, TCS SP5</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cover glasses, 24 &#215; 50 mm</td>
			<td>Vwr</td>
			<td>631-0146</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPT &#947;&#8209;secretase inhibitor</td>
			<td>Sigma Aldrich</td>
			<td>D5942</td>
			<td></td>
		</tr>
		<tr>
			<td>DC101 anti mouse VEGFR-2 Clone</td>
			<td>BioXcell</td>
			<td>BP0060</td>
			<td></td>
		</tr>
		<tr>
			<td>DC101 isotype rat IgG1</td>
			<td>BioXcell</td>
			<td>BP0290</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>D2438-5X</td>
			<td>Biohazard: adequate safety instructions should be taken when handling</td>
		</tr>
		<tr>
			<td>DPBS (10x), no calcium, no magnesium</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>14200067</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA 40 mM</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>15575-038</td>
			<td></td>
		</tr>
		<tr>
			<td>Embryonic stem-cell Fetal Bovine Serum</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>16141-079</td>
			<td>Should be lot-tested for maximum ES cell viability and growth. Heat inactivate at 60&#176;C and store at &#8722;20 &#176;C for up to 1 year</td>
		</tr>
		<tr>
			<td>Eppendorf Microcentrifuge 5415R</td>
			<td>Eppendorf AG</td>
			<td>&#160;Z605212</td>
			<td></td>
		</tr>
		<tr>
			<td>Erythropoietin, human (hEPO), 250 U (2.5 &#181;g) (1 mL)</td>
			<td>Roche</td>
			<td>11120166001</td>
			<td></td>
		</tr>
		<tr>
			<td>ESGRO Recombinant Mouse LIF Protein (10&#8311; units&#160;&#160;1 mL)</td>
			<td>Milipore, Merck</td>
			<td>ESG1107</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon tubes 15 mL</td>
			<td>Greiner Bio-One</td>
			<td>188271</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon tubes 50 mL</td>
			<td>Greiner Bio-0ne</td>
			<td>227270</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter tip ,clear ,sterile F.Gilson, P-200</td>
			<td>Greiner Bio-One</td>
			<td>739288</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter tip ,clear ,sterile F.Gilson, P10</td>
			<td>Greiner Bio-One</td>
			<td>771288</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter tip ,clear ,sterile F.Gilson, P1000</td>
			<td>Greiner Bio-One</td>
			<td>740288</td>
			<td></td>
		</tr>
		<tr>
			<td>FITC conjugated anti-&#945; Smooth Muscle Actin (SMA) (clone 1A4)</td>
			<td>Sigma Aldrich</td>
			<td>F3777</td>
			<td></td>
		</tr>
		<tr>
			<td>FITC conjugated rat anti-mouse CD45 (clone 30-F11)</td>
			<td>Biolegend</td>
			<td>103107</td>
			<td></td>
		</tr>
		<tr>
			<td>FITC Rat IgG2b, &#954; Isotype Ctrl Antibody (clone RTK4530)</td>
			<td>Biolegend</td>
			<td>400605</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorscent mounting media</td>
			<td>DAKO</td>
			<td>S3023</td>
			<td></td>
		</tr>
		<tr>
			<td>Gascompress</td>
			<td>Cutisoft</td>
			<td>45846</td>
			<td></td>
		</tr>
		<tr>
			<td>Gauze Cutisoft 10 x 10 cm</td>
			<td>Bsn Medical</td>
			<td>45844_00</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel blotting paper, Grade GB003</td>
			<td>Whatman</td>
			<td>WHA10547922</td>
			<td></td>
		</tr>
		<tr>
			<td>Gelatin solution, type B</td>
			<td>Sigma-Aldrich</td>
			<td>G1393-100 ml</td>
			<td></td>
		</tr>
		<tr>
			<td>Glasgow&#39;s MEM (GMEM)</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>21710082</td>
			<td></td>
		</tr>
		<tr>
			<td>IHC Zinc Fixative</td>
			<td>BD Pharmigen</td>
			<td>550523</td>
			<td></td>
		</tr>
		<tr>
			<td>IncuSafe CO2 Incubator</td>
			<td>PHCBi</td>
			<td>MCO-170AICUV-PE</td>
			<td></td>
		</tr>
		<tr>
			<td>Interleukin-6, human (hIL-6)</td>
			<td>Roche</td>
			<td>11138600001</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Glutamine 200 mM</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>25030-024</td>
			<td></td>
		</tr>
		<tr>
			<td>MEM Non-Essential Amino Acids Solution (100x)</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>11140035</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slide box</td>
			<td>Kartell Labware</td>
			<td>278</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slide, Starfrost</td>
			<td>Knittel glass</td>
			<td>VS113711FKB.0</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Cdh5_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00110467</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Eng_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00148981</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Epha4_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00093576</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Ephb2_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00154014</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Flt1_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00096292</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Flt4_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00099064</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Gapdh_3_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT01658692</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Kdr_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00097020</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Notch1_1_SG QuantiTect Primer</td>
			<td>Qiagen</td>
			<td>QT00156982</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Nr2f2_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00153104</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Pecam1_1_SG QuantiTect Primer</td>
			<td>Qiagen</td>
			<td>QT01052044</td>
			<td></td>
		</tr>
		<tr>
			<td>Mm_Tek_1_SG QuantiTect Primer Assay</td>
			<td>Qiagen</td>
			<td>QT00114576</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse (ICR) Inactivated Embryonic Fibroblasts&#160; (2 M)</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>A24903</td>
			<td>Store vials in liquid nitrogen (195.79 &#176;C) indefinitely</td>
		</tr>
		<tr>
			<td>Mouse embryonic stem cell line 7AC5/EYFP (ATCC SCRC-1033)</td>
			<td>ATCC</td>
			<td>SCRC-1033</td>
			<td>Generated by Dr A Nagy, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Ave, Toronto, Ontario, M5G 1X5, Canada. [Hadjantonakis, A. K., et al. Mechanisms of Development. 76 (1&#8211;2), 79&#8211;90 (1998)].</td>
		</tr>
		<tr>
			<td>Mouse embryonic stem cell lines Acvrl1 +/- and Acvrl1 +/+</td>
			<td></td>
			<td></td>
			<td>Generated at Leiden University Medical Centre [Thalgott, J.H. et al. Circulation. 138 (23), 2698&#8211;2712 (2018)].</td>
		</tr>
		<tr>
			<td>Mouse embryonic stem cells line E14</td>
			<td></td>
			<td></td>
			<td>Provided by M Letarte laboratory and generated according to Cho, S. K., et al. Blood. 98 (13), 3635&#8211;3642 (2001).</td>
		</tr>
		<tr>
			<td>Mouse embryonic stem cells line R1 (ATCC SCRC-1011)</td>
			<td>ATCC</td>
			<td>SCRC-1011</td>
			<td>Generated by Dr A Nagy, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Ave, Toronto, Ontario, M5G 1X5, Canada. [Nagy, A., et al. Procedings of the National Academy of Sciences of the United States of America. 90 (18), 8424&#8211;8428 (1993)].</td>
		</tr>
		<tr>
			<td>Mouse embryonic stem cells line Z/Red (strain 129/Ola)</td>
			<td></td>
			<td></td>
			<td>Generated by Dr A Nagy, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Ave, Toronto, Ontario, M5G 1X5, Canada [Vintersten, K., et al. Genesis. 40 (4), 241&#8211;246 (2004)].</td>
		</tr>
		<tr>
			<td>NanoDrop 1000 UV/VIS Spectrophotometer</td>
			<td>Thermo Fischer Scientific</td>
			<td>ND-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>PD0325901</td>
			<td>Selleckchem</td>
			<td>S1036</td>
			<td></td>
		</tr>
		<tr>
			<td>PDGF-BB, Recombinant Human</td>
			<td>Peprotech</td>
			<td>100-14B</td>
			<td></td>
		</tr>
		<tr>
			<td>Pecam-1 antibody, Rat Anti-Mouse</td>
			<td>BD Biosciences</td>
			<td>550274</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-streptomycin (10,000 U/mL)</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish, PS, 94/16 mm, standard ,with vents, sterile</td>
			<td>Greiner Bio-One</td>
			<td>633181</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetboy acu 2</td>
			<td>Integra-Biosciences</td>
			<td>155 019</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman G Multichannel P8 x 200G</td>
			<td>Gilson</td>
			<td>F144072</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman G Starter Kit, 4 Pipette Kit, P2G, P20G, P200G, P1000G</td>
			<td>Gilson</td>
			<td>F167360</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Human BMP-4 Protein</td>
			<td>R&#38;D Systems</td>
			<td>314-BP</td>
			<td></td>
		</tr>
		<tr>
			<td>RNeasy Plus mini Kit</td>
			<td>QIAGEN</td>
			<td>74134</td>
			<td></td>
		</tr>
		<tr>
			<td>Serological pipettes, 10 mL</td>
			<td>Greiner Bio-One</td>
			<td>607 180</td>
			<td></td>
		</tr>
		<tr>
			<td>Serological pipettes, 25 mL</td>
			<td>Greiner Bio-One</td>
			<td>760 180</td>
			<td></td>
		</tr>
		<tr>
			<td>Serological pipettes, 5 mL</td>
			<td>Greiner Bio-One</td>
			<td>606 180</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide (NaOH)</td>
			<td>Merck</td>
			<td>106498</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium pyruvate 100 mM</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>11360039</td>
			<td></td>
		</tr>
		<tr>
			<td>Test tubes 5ml round-bottom with cell-strainer cap</td>
			<td>Corning</td>
			<td>352235</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermal cycler, T100</td>
			<td>Biorad</td>
			<td>1861096</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100 (BioXtra)</td>
			<td>Sigma Aldrich</td>
			<td>T9284</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan Blue Solution, 0.4%</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>15250061</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin (2.5%)</td>
			<td>Gibco, Thermofisher scientific</td>
			<td>15090046</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum Filter/Storage Bottle System, 500 mL</td>
			<td>Corning</td>
			<td>430758</td>
			<td></td>
		</tr>
		<tr>
			<td>VEGFA165 , recombinant murine</td>
			<td>Peprotech</td>
			<td>450-32</td>
			<td></td>
		</tr>
		<tr>
			<td>Water, Sterile</td>
			<td>Fresenius-Kabi</td>
			<td>B230531</td>
			<td></td>
		</tr>
		<tr>
			<td>Waterbath, Lab-Line Digital</td>
			<td>Thermo Fischer Scientific</td>
			<td>18052A</td>
			<td></td>
		</tr>
	</tbody>
</table>

in vitro three-dimensional sprouting assay of angiogenesis using mouse embryonic stem cells for vascular disease modeling and drug testing

Recent advances in induced pluripotent stem cells (iPSC) and gene editing technologies enable the development of novel human cell-based disease models for phenotypic drug discovery (PDD) programs. Although these novel devices could predict the safety and efficacy of investigational drugs in humans more accurately, their development to the clinic still strongly rely on mammalian data, notably the use of mouse disease models. In parallel to human organoid or organ-on-chip disease models, the development of relevant in vitro mouse models is therefore an unmet need for evaluating direct drug efficacy and safety comparisons between species and in vivo and in vitro conditions. Here, a vascular sprouting assay that utilizes mouse embryonic stem cells differentiated into embryoid bodies (EBs) is described. Vascularized EBs cultured onto 3D-collagen gel develop new blood vessels that expand, a process called sprouting angiogenesis. This model recapitulates key features of in vivo sprouting angiogenesis-formation of blood vessels from a pre-existing vascular network-including endothelial tip cell selection, endothelial cell migration and proliferation, cell guidance, tube formation, and mural cell recruitment. It is amenable to screening for drugs and genes modulating angiogenesis and shows similarities with recently described three-dimensional (3D) vascular assays based on human iPSC technologies.

The protocol overview of the blood vessel sprouting assay is shown in Figure 1. Nine-day-old EBs derived from three independent 129/Ola mESC lines (Z/Red, R1, and E14) were enzymatically dissociated into single cells using collagenase A. Cells were stained for PECAM-1 and analyzed by Fluorescence-activated cell sorting (FACS) as described. All the cell lines exhibited robust endothelial differentiation, and no differences in their ability to differentiate into endothelial cells were observed...

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In Vitro Three-Dimensional Sprouting Assay of Angiogenesis Using Mouse Embryonic Stem Cells for Vascular Disease Modeling and Drug Testing

This assay utilizes mouse embryonic stem cells differentiated into embryoid bodies cultured in 3D-collagen gel to analyze the biological processes that control sprouting angiogenesis in vitro. The technique can be applied for testing drugs, modeling diseases, and for studying specific genes in the context of deletions that are embryonically lethal.

In Vitro Three-Dimensional Sprouting Assay of Angiogenesis Using Mouse Embryonic Stem Cells for Vascular Disease Modeling and Drug Testing

Recent advances in induced pluripotent stem cells (iPSC) and gene editing technologies enable the development of novel human cell-based disease models for ...

This protocol describes an in vitro sprouting angiogenesis assay that recapitulates many features of the formation of blood vessels and can be used for testing drugs. This method is easy to implement in a lab, robust, and scalable. It has many similarities with assays using human endothelial cells and microspheres.This model robustly mimics the phenotype showing defective endothelial tip cell selection and orientated endothelial cell migration that leads to pathological angiogenesis. The work can provide insights into the mechanisms regulating sprouting angiogenesis, the key genes, and the signaling pathways involved, notably by performing genetic screening The main challenge is maintaining the quality or pluripotency of mouse embryonic stem cells in culture. Regularly checking the pluripotency stages and morphology of the cell lines is important.It is also important to perform a karyotyping of the cell lines as they tend to culture to lose or gain chromosomes. Begin by coating one well of the six well cell culture plate with 500 microliters of 0.1%gelatin solution and place it in a carbon dioxide incubator for 30 minutes. Then wash the gelatin coated plates with PBS and add 500 microliters of freshly prepared CM plus minus medium.To obtain a pure population of mouse embryonic stem cells or mESCs, trypsinize the cell culture plate with 10x TVP buffer for 30 seconds at room temperature. Then resuspend the cells in one milliliter of mesoderm differentiation medium before transferring them to the gelatin coated six well plate for 30 minutes to allow the mouse embryonic fibroblasts to attach while the mESCs stay in suspension. Transfer the cell suspension to a 15 milliliter tube before counting live cells using a Neubauer hemocytometer in Trypan blue dye.Then centrifuge the cells at 200 times G for five minutes at room temperature. Remove the supernatant and resuspend the cell pellet in an appropriate volume of mesoderm differentiation medium. Prepare four 94 millimeter low attachment polystyrene dishes by adding 15 milliliters of sterile water to the bottom.After transferring the cell suspension into a sterile plastic reservoir, load four positions of a multi-channel pipette with 22 microliters of cell suspension per channel. Lift and place the inverted lid of the 94 millimeter dish on the clean surface of the flow cabinet with the inner side facing upwards. Deposit 40 drops of the cell suspension on the inner surface of each lid and carefully invert the lid without disturbance to place it back on the dish, so that the drops face the water.Incubate the dishes in a carbon dioxide incubator for four days, considering this as differentiation day zero. After four days of incubation, collect the hanging drops in a 15 milliliter conical tube using a P1000 pipette. Let EB sediment in the tube before removing the supernatant.Resuspend the EBs in three milliliters of 2x vascular differentiation medium before transferring and uniformly distributing EB suspension in a 60 millimeter agar-coated dish. Incubate the dishes in a carbon dioxide incubator until day nine with a medium refresh every two days. Prepare a 35 millimeter culture dish by adding one milliliter of the sprouting medium to its bottom.To induce gelation, incubate the dish at 37 degrees Celsius for five minutes. Collect nine day old EBs from one agar dish in a 15 milliliter conical tube and remove the supernatant. Resuspend the EBs in two milliliters of cold sprouting medium to transfer to the culture dish coated with the first layer of sprouting medium.Distribute the EBs all over the plate, ensuring they are at an equal distance from each other. The first sprout formation should be evident after incubation for around 24 to 48 hours. On day 12, use a spatula to carefully transfer the collagen gel containing EBs to a glass slide.Remove the excess liquid with a pipette and dehydrate the gel by placing a gauze sheet of nylon linen and absorbent filter cards on top of the gel. Apply pressure with a weight of 250 grams for two minutes. Then remove the nylon papers to allow the slides to air dry for 30 minutes at room temperature.After drying, fix the EBs using zinc solution overnight at four degrees Celsius. On the next day, remove the fixative before washing the slides five times with PBS. Permeabilize the EBs and PBS containing 0.1%Triton X-100.After 15 minutes, remove the permeabilization solution to wash the slides five times with PBS for five minutes. Incubate the EBs in the blocking buffer for one hour at room temperature and wash with PBS for five minutes. Then add the primary antibody diluted in the blocking buffer and incubate at four degrees Celsius overnight.Then incubate the slides with Goat anti-Rat Alexa 555 secondary antibody in a blocking buffer for two hours at room temperature. After incubation, wash the slides three times with PBS for five minutes and one time with water before mounting them for microscopy. The 3D sprouting angiogenesis assay was carried out on three EBs with two drugs, DC101 and DAPT.Both compounds progressively blocked the angiogenesis in the EB model with increasing concentrations. The various concentrations of drugs in EBs showed that high doses of DC101 inhibit the number and length of the vessel sprouts. DAPT had opposite effects at the dose of one micromole per liter.DAPT strongly increased the number of endothelial tip cells per vessel sprouts having a misguidance phenotype even at low doses, compared to DC101. Defective vessel sprouting was observed in hereditary hemorrhagic telangiectasia EBs from ACVRL1 control and ACVRL1 heterozygous genotypes with numerous misguidance phenotypes sprouting at random angles relative to the parent vessels. Mixtures of a wild-type mESC line at a one-to-one ratio with an unlabeled mESC wild-type line, led to an equal contribution to the leading endothelial tip cells.Microscopic analysis of this representative chimeric EB was conducted to identify the genotypic origin of the leading endothelial tip cells. To quantify mural cell coverage of the vessel sprout, EBs were fixed and stained for endothelial cell markers, PECAM, and mural cell marker, alpha smooth muscle actin. A high magnification image revealed that one individual vessel sprout was surrounded by mural cells.The binary transformation was performed after color channel separation and the ratio of PECAM positive vessels covered by alpha SMA positive mural cells was quantified. The genetic background of the embryonic stem cell line is also a key factor the researchers must consider as some lines sprout better than others. This method can be used to perform genetic screening using RNAi approaches or a bank of mouse embryonic stem cells harboring gene mutations.

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JoVE Journal

Biology

In vitro Differentiation of Mouse Embryonic Stem (mES) Cells Using the Hanging Drop Method

Stem cells have the remarkable potential to develop into many different cell types. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, This promising of science is leading scientists to investigate the possibility of cell-based therapies to treat disease.

When culture in suspension without antidifferentiation factors, embryonic stem cells spontaneously differentiate and form three-dimensional multicellular aggregates. These cell aggregates are called embryoid bodies(EB). Hanging drop culture is a widely used EB formation induction method. The rounded bottom of hanging drop allows the aggregation of ES cells which can provide mES cells a good environment for forming EBs. The number of ES cells aggregatied in a hanging drop can be controlled by varying the number of cells in the initial cell suspension to be hung as a drop from the lid of Petri dish. Using this method we can reproducibly form homogeneous EBs from a predetermined number of ES cells. 

In vitro Differentiation of Mouse Embryonic Stem mES Cells Using the Hanging Drop Method

This video demonstrates how to conduct in vitro differentiation of mouse embryonic stem cells to embryoid bodies using the hanging drop method.

Stem cells have the remarkable potential to develop into many different cell types. When a stem cell divides, each new cell has the potential to either ...

In vitro Labeling of Human Embryonic Stem Cells for Magnetic Resonance Imaging

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of the predominant imaging modalities to assess the restoration of the injured myocardium. Furthermore, ex-vivo labeling agents, such as iron-oxide nanoparticles, have been employed to track and localize the transplanted stem cells. However, this method does not monitor a fundamental cellular biology property regarding the viability of transplanted cells. It has been known that manganese chloride (MnCl2) enters the cells via voltage-gated calcium (Ca2+) channels when the cells are biologically active, and accumulates intracellularly to generate T1 shortening effect. Therefore, we suggest that manganese-guided MRI can be useful to monitor cell viability after the transplantation of hESC into the myocardium.
In this video, we will show how to label hESC with MnCl2 and how those cells can be clearly seen by using MRI in vitro. At the same time, biological activity of Ca2+-channels will be modulated utilizing both Ca2+-channel agonist and antagonist to evaluate concomitant signal changes.

In this video, we are showing how to label human embryonic stem cells (hESC) with manganese chloride (MnCl2) which can enter cells via voltage-gated calcium channels when the cells are biologically active. Additionally, we show the use of MnCl2 as cellular MRI contrast agent to determine the in vitro viability of hESC.

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of ...

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 ...

Efficient Differentiation of Mouse Embryonic Stem Cells into Motor Neurons

Direct differentiation of embryonic stem (ES) cells into functional motor neurons represents a promising resource to study disease mechanisms, to screen new drug compounds, and to develop new therapies for motor neuron diseases such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). Many current protocols use a combination of retinoic acid (RA) and sonic hedgehog (Shh) to differentiate mouse embryonic stem (mES) cells into motor neurons1-4. However, the differentiation efficiency of mES cells into motor neurons has only met with moderate success. We have developed a two-step differentiation protocol5 that significantly improves the differentiation efficiency compared with currently established protocols. The first step is to enhance the neuralization process by adding Noggin and fibroblast growth factors (FGFs). Noggin is a bone morphogenetic protein (BMP) antagonist and is implicated in neural induction according to the default model of neurogenesis and results in the formation of anterior neural patterning6. FGF signaling acts synergistically with Noggin in inducing neural tissue formation by promoting a posterior neural identity7-9. In this step, mES cells were primed with Noggin, bFGF, and FGF-8 for two days to promote differentiation towards neural lineages. The second step is to induce motor neuron specification. Noggin/FGFs exposed mES cells were incubated with RA and a Shh agonist, Smoothened agonist (SAG), for another 5 days to facilitate motor neuron generation. To monitor the differentiation of mESs into motor neurons, we used an ES cell line derived from a transgenic mouse expressing eGFP under the control of the motor neuron specific promoter Hb91. Using this robust protocol, we achieved 51&plusmn;0.8% of differentiation efficiency (n = 3; p &lt; 0.01, Student's t-test)5. Results from immunofluorescent staining showed that GFP+ cells express the motor neuron specific markers, Islet-1 and choline acetyltransferase (ChAT). Our two-step differentiation protocol provides an efficient way to differentiate mES cells into spinal motor neurons.

We developed a new protocol to improve efficiency of in vitro differentiation of mouse embryonic stem cells into motor neurons. The differentiated ES cells acquired motor neurons features as evidenced by expression of neuronal and motor neuron markers using immunohistochemical techniques.

Direct differentiation of embryonic stem (ES) cells into functional  motor neurons represents a promising resource to study disease mechanisms, to  screen ...

Preparation of Mouse Embryonic Fibroblast Cells Suitable for Culturing Human Embryonic and Induced Pluripotent Stem Cells

In general, human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs)1 can be cultured under variable conditions. However, it is not easy to establish an effective system for culturing these cells. Since the culture conditions can influence gene expression that confers pluripotency in hESCs and hiPSCs, the optimization and standardization of the culture method is crucial.
The establishment of hESC lines was first described by using MEFs as feeder cells and fetal bovine serum (FBS)-containing culture medium2. Next, FBS was replaced with knockout serum replacement (KSR) and FGF2, which enhances proliferation of hESCs3. Finally, feeder-free culture systems enable culturing cells on Matrigel-coated plates in KSR-containing conditioned medium (medium conditioned by MEFs)4. Subsequently, hESCs culture conditions have moved towards feeder-free culture in chemically defined conditions5-7. Moreover, to avoid the potential contamination by pathogens and animal proteins culture methods using xeno-free components have been established8.
To obtain improved conditions mouse feeder cells have been replaced with human cell lines (e.g. fetal muscle and skin cells9, adult skin cells10, foreskin fibroblasts11-12, amniotic mesenchymal cells13). However, the efficiency of maintaining undifferentiated hESCs using human foreskin fibroblast-derived feeder layers is not as high as that from mouse feeder cells due to the lower level of secretion of Activin A14. Obviously, there is an evident difference in growth factor production by mouse and human feeder cells.
Analyses of the transcriptomes of mouse and human feeder cells revealed significant differences between supportive and non-supportive cells. Exogenous FGF2 is crucial for maintaining self-renewal of hESCs and hiPSCs, and has been identified as a key factor regulating the expression of Tgf&beta;1, Activin A and Gremlin (a BMP antagonist) in feeder cells. Activin A has been shown to induce the expression of OCT4, SOX2, and NANOG in hESCs15-16.
For long-term culture, hESCs and hiPSCs can be grown on mitotically inactivated MEFs or under feeder-free conditions in MEF-CM (MEF-Conditioned Medium) on Matrigel-coated plates to maintain their undifferentiated state. Success of both culture conditions fully depends on the quality of the feeder cells, since they directly affect the growth of hESCs.
Here, we present an optimized method for the isolation and culture of mouse embryonic fibroblasts (MEFs), preparation of conditioned medium (CM) and enzyme-linked immunosorbent assay (ELISA) to assess the levels of Activin A within the media.

The quality of mouse embryonic fibroblasts (MEFs) is dictated by the right strain of mouse such as CF-1. Pluripotency-supportive MEFs and conditioned media (CM) obtained from these should contain optimal concentrations of Activin A, Gremlin and Tgf&beta;1 needed for the Activin/Nodal and FGF pathways to co-operatively maintain self-renewal and pluripotency.

In general, human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs)1 can be cultured under variable conditions. However, it ...

Endothelial Cell Tube Formation Assay for the In Vitro Study of Angiogenesis

Angiogenesis is a vital process for normal tissue development and wound healing, but is also associated with a variety of pathological conditions. Using this protocol, angiogenesis may be measured in vitro in a fast, quantifiable manner. Primary or immortalized endothelial cells are mixed with conditioned media and plated on basement membrane matrix. The endothelial cells form capillary like structures in response to angiogenic signals found in conditioned media. The tube formation occurs quickly with endothelial cells beginning to align themselves within 1&#160;hr and lumen-containing tubules beginning to appear within 2 hr. Tubes can be visualized using a phase contrast inverted microscope, or the cells can be treated with calcein AM prior to the assay and tubes visualized through fluorescence or confocal microscopy. The number of branch sites/nodes, loops/meshes, or number or length of tubes formed can be easily quantified as a measure of in vitro angiogenesis. In summary, this assay can be used to identify genes and pathways that are involved in the promotion or inhibition of angiogenesis in a rapid, reproducible, and quantitative manner.

Endothelial Cell Tube Formation Assay for the In Vitro Study of Angiogenesis

The tube formation assay is a fast, quantifiable method for measuring in vitro angiogenesis. Endothelial cells are combined with conditioned media and plated on basement membrane extract. Tube formation occurs within hours and newly formed tubules easily quantified.

Angiogenesis is a vital process for normal tissue development and wound healing, but is also associated with a variety of pathological conditions. Using ...

Profiling Individual Human Embryonic Stem Cells by Quantitative RT-PCR

Heterogeneity of stem cell population hampers detailed understanding of stem cell biology, such as their differentiation propensity toward different lineages. A single cell transcriptome assay can be a new approach for dissecting individual variation. We have developed the single cell qRT-PCR method, and confirmed that this method works well in several gene expression profiles. In single cell level, each human embryonic stem cell, sorted by OCT4::EGFP positive cells, has high expression in OCT4, but a different level of NANOG expression. Our single cell gene expression assay should be useful to interrogate population heterogeneities.

Single cell gene expression assay is needed for understanding stem cell heterogeneities.

Heterogeneity of stem cell population hampers detailed understanding of stem cell biology, such as their differentiation propensity toward different ...

Zinc-finger Nuclease Enhanced Gene Targeting in Human Embryonic Stem Cells

One major limitation with current human embryonic stem cell (ESC) differentiation protocols is the generation of heterogeneous cell populations.&#160;These cultures contain the cells of interest, but are also contaminated with undifferentiated ESCs, non-neural derivatives and other neuronal subtypes.&#160; This limits their use in in vitro and in vivo applications, such as in vitro modeling for drug discovery or cell replacement therapy. To help overcome this, reporter cell lines, which offer a means to visualize, track and isolate cells of interest, can be engineered.&#160;However, to achieve this in human embryonic stem cells via conventional homologous recombination is extremely inefficient.&#160;This protocol describes targeting of the Pituitary homeobox 3 (PITX3) locus in human embryonic stem cells using custom designed zinc-finger nucleases, which introduce site-specific double-strand DNA breaks, together with a PITX3-EGFP-specific DNA donor vector. Following the generation of the PITX3 reporter cell line, it can then be differentiated using published protocols for use in studies such as in vitro Parkinson&#8217;s disease modeling or cell replacement therapy.

Reporter cell lines offer a means to visualize, track and isolate cells of interest from heterogeneous populations.&#160;However, gene-targeting using conventional homologous recombination in human embryonic stem cells is extremely inefficient. Herein, we describe targeting CNS midbrain specific transcription factor PITX3 locus with EGFP using zinc-finger nuclease enhanced homologous recombination.

One major limitation with current human embryonic stem cell (ESC) differentiation protocols is the generation of heterogeneous cell ...

Isolation and Primary Culture of Mouse Aortic Endothelial Cells

The vascular endothelium is essential to normal vascular homeostasis. Its dysfunction participates in various cardiovascular disorders. The mouse is an important model for cardiovascular disease research. This study demonstrates a simple method to isolate and culture endothelial cells from the mouse aorta without any special equipment. To isolate endothelial cells, the thoracic aorta is quickly removed from the mouse body, and the attached adipose tissue and connective tissue are removed from the aorta. The aorta is cut into 1 mm rings. Each aortic ring is opened and seeded onto a growth factor reduced matrix with the endothelium facing down. The segments are cultured in endothelial cell growth medium for about 4 days. The endothelial sprouting starts as early as day 2. The segments are then removed and the cells are cultured continually until they reach confluence. The endothelial cells are harvested using neutral proteinase and cultured in endothelial cell growth medium for another two passages before being used for experiments. Immunofluorescence staining indicated that after the second passage the majority of cells were double positive for Dil-ac-LDL uptake, Lectin binding, and CD31 staining, the typical characteristics of endothelial cells. It is suggested that cells at the second to third passages are suitable for in vitro and in vivo experiments to study the endothelial biology. Our protocol provides an effective means of identifying specific cellular and molecular mechanisms in endothelial cell physiopathology.

The vascular endothelial cells play a significant role in many important cardiovascular disorders. This article describes a simple method to isolate and expand endothelial cells from the mouse aorta without using any special equipment. Our protocol provides an effective means of identifying mechanisms in endothelial cell physiopathology.

The vascular endothelium is essential to normal vascular homeostasis. Its dysfunction participates in various cardiovascular disorders. The mouse is an ...

Three-dimensional Reconstruction of the Vascular Architecture of the Passive CLARITY-cleared Mouse Ovary

The ovary is the main organ of the female reproductive system and is essential for the production of female gametes and for controlling the endocrine system, but the complex structural relationships and three-dimensional (3D) vasculature architectures of the ovary are not well described. In order to visualize the 3D connections and architecture of blood vessels in the intact ovary, the first important step is to make the ovary optically clear. In order to avoid tissue shrinkage, we used the hydrogel fixation-based passive CLARITY (Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging/ Immunostaining/In situ-hybridization-compatible Tissue Hydrogel) protocol method to clear an intact ovary. Immunostaining, advanced multiphoton confocal microscopy, and 3D image-reconstructions were then used for the visualization of ovarian vessels and follicular capillaries. Using this approach, we showed a significant positive correlation (P &#60;0.01) between the length of the follicular capillaries and volume of the follicular wall.

Here we present an adaptation of the passive CLARITY and 3D reconstruction method for visualization of the ovarian vasculature and follicular capillaries in intact mouse ovaries.

The ovary is the main organ of the female reproductive system and is essential for the production of female gametes and for controlling the endocrine ...