Name: in vitro model of coronary angiogenesis
Uploaded: 2020-03-10T13:00:00
Description: Watch this Scientific Journal Video about In Vitro Model of Coronary Angiogenesis at JoVE.com

The authors thank the members of Sharma laboratory for providing a supportive research environment. We like to extend special thank you to Diane (Dee) R. Hoffman who maintains and cares for our mouse colony. We also would like to thank Drs. Philip J. Smaldino and Carolyn Vann for thoroughly proofreading the manuscript and providing helpful comments. This work was supported by funds from Ball State University Provost Office and Department of Biology to B.S, Indiana Academy of Sciences Senior Research Grant funds to B.S, and NIH (RO1-HL128503) and The New York Stem Cell Foundation funds to K.R.

Use of all the animals in this protocol followed Ball State University Institutional Animal Care and Use Committee (IACUC) guidelines.
1. Establishing Mouse Breeders and Detecting Vaginal Plugs for Timed Pregnancies
<ol>
	<li>Set up a mouse breeding cage with wild type male and female mice. Ensure that the age of the breeding mice is between 6-8 weeks. Set up either a pair (1 male and 1 female) or as a trio (1 male and 2 female) for breeding.</li>
	<li>Check for a vaginal plug the following ...

<ol>
	<li>Red-Horse, 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=Coronary+arteries+form+by+developmental+reprogramming+of+venous+cells.">Coronary arteries form by developmental reprogramming of venous cells.</a> Nature. 464 (7288), 549-553 (2010).</li><li>Chen, H. 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=The+sinus+venosus+contributes+to+coronary+vasculature+through+VEGFC-stimulated+angiogenesis.">The sinus venosus contributes to coronary vasculature through VEGFC-stimulated angiogenesis.</a> Development. 141 (23), 4500-4512 (2014).</li><li>Volz, K. 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=Pericytes+are+progenitors+for+coronary+artery+smooth+muscle.">Pericytes are progenitors for coronary artery smooth muscle.</a> Elife. 4, (2015).</li><li>Chen, H. 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=VEGF-C+and+aortic+cardiomyocytes+guide+coronary+artery+stem+development.">VEGF-C and aortic cardiomyocytes guide coronary artery stem development.</a> Journal of Clinical Investigation. 124 (11), 4899-4914 (2014).</li><li>Chang, A. H., 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=DACH1+stimulates+shear+stress-guided+endothelial+cell+migration+and+coronary+artery+growth+through+the+CXCL12-CXCR4+signaling+axis.">DACH1 stimulates shear stress-guided endothelial cell migration and coronary artery growth through the CXCL12-CXCR4 signaling axis.</a> Genes and Development. , (2017).</li><li>Tian, X., 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=Subepicardial+endothelial+cells+invade+the+embryonic+ventricle+wall+to+form+coronary+arteries.">Subepicardial endothelial cells invade the embryonic ventricle wall to form coronary arteries.</a> Cell Research. 23 (9), 1075-1090 (2013).</li><li>Wu, B., 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=Endocardial+Cells+Form+the+Coronary+Arteries+by+Angiogenesis+through+Myocardial-Endocardial+VEGF+Signaling.">Endocardial Cells Form the Coronary Arteries by Angiogenesis through Myocardial-Endocardial VEGF Signaling.</a> Cell. 151 (5), 1083-1096 (2012).</li><li>Katz, T. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distinct+compartments+of+the+proepicardial+organ+give+rise+to+coronary+vascular+endothelial+cells.">Distinct compartments of the proepicardial organ give rise to coronary vascular endothelial cells.</a> Developmental Cell. 22 (3), 639-650 (2012).</li><li>Das, S., Red-Horse, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+plasticity+in+cardiovascular+development+and+disease.">Cellular plasticity in cardiovascular development and disease.</a> Developmental Dynamics. 246 (4), 328-335 (2017).</li><li>Sharma, B., Chang, A., Red-Horse, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coronary+Artery+Development:+Progenitor+Cells+and+Differentiation+Pathways.">Coronary Artery Development: Progenitor Cells and Differentiation Pathways.</a> Annual Review of Physiology. 79, 1-19 (2017).</li><li>Tian, X., Pu, W. T., Zhou, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+origin+and+developmental+program+of+coronary+angiogenesis.">Cellular origin and developmental program of coronary angiogenesis.</a> Circulation Research. 116 (3), 515-530 (2015).</li><li>Wu, B., 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=Endocardial+cells+form+the+coronary+arteries+by+angiogenesis+through+myocardial-endocardial+VEGF+signaling.">Endocardial cells form the coronary arteries by angiogenesis through myocardial-endocardial VEGF signaling.</a> Cell. 151 (5), 1083-1096 (2012).</li><li>Gerhardt, H., 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=VEGF+guides+angiogenic+sprouting+utilizing+endothelial+tip+cell+filopodia.">VEGF guides angiogenic sprouting utilizing endothelial tip cell filopodia.</a> Journal of Cell Biology. 161 (6), 1163-1177 (2003).</li><li>Ruhrberg, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatially+restricted+patterning+cues+provided+by+heparin-binding+VEGF-A+control+blood+vessel+branching+morphogenesis.">Spatially restricted patterning cues provided by heparin-binding VEGF-A control blood vessel branching morphogenesis.</a> Genes and Development. 16 (20), 2684-2698 (2002).</li><li>Kikuchi, 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=An+antiangiogenic+isoform+of+VEGF-A+contributes+to+impaired+vascularization+in+peripheral+artery+disease.">An antiangiogenic isoform of VEGF-A contributes to impaired vascularization in peripheral artery disease.</a> Nature Medicine. 20 (12), 1464-1471 (2002).</li><li>Folkman, 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=Isolation+of+a+tumor+factor+responsible+for+angiogenesis.">Isolation of a tumor factor responsible for angiogenesis.</a> Journal of Experimental Medicine. 133 (2), 275-288 (1971).</li><li>Ferrara, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+VEGF+in+the+regulation+of+physiological+and+pathological+angiogenesis.">The role of VEGF in the regulation of physiological and pathological angiogenesis.</a> Experientia Supplementum. (94), 209-231 (2005).</li><li>Ferrara, N., Bunting, S. <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,+a+specific+regulator+of+angiogenesis.">Vascular endothelial growth factor, a specific regulator of angiogenesis.</a> Current Opinion in Nephrology and Hypertension. 5 (1), 35-44 (1996).</li><li>Sharma, B., 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=Alternative+Progenitor+Cells+Compensate+to+Rebuild+the+Coronary+Vasculature+in+Elabela-+and+Apj-Deficient+Hearts.">Alternative Progenitor Cells Compensate to Rebuild the Coronary Vasculature in Elabela- and Apj-Deficient Hearts.</a> Developmental Cell. 42 (6), 655-666 (2017).</li><li>Rhee, 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=Endothelial+deletion+of+Ino80+disrupts+coronary+angiogenesis+and+causes+congenital+heart+disease.">Endothelial deletion of Ino80 disrupts coronary angiogenesis and causes congenital heart disease.</a> Nature Communications. 9 (1), 368 (2018).</li></ol>

Some of the most critical steps for successfully growing coronary vessels from the SV and Endo progenitor tissues are: 1) Correctly identifying and isolating the SV tissue for SV culture; 2) using ventricles from embryos between the ages of e11&#8722;11.5 for accurate Endo culture; 3) maintaining sterile conditions throughout the dissection period and keeping the tissues cold at all times; and 4) keeping the explants attached to the ECM coated membrane to avoid tissue floating in the medium.
F...

Blood vessels of the heart are commonly called coronary vessels. These vessels are comprised of arteries, veins, and capillaries. During development, highly branched capillaries are established first, which then remodel into coronary arteries and veins1,2,3,4,5. These initial capillaries are built from endothelial progenitor cells found in the proepicardium, sinus venosus (SV), and endocardium (Endo) tissues1,6,7,8. SV is the inflow organ of embryonic heart and Endo is the inner lining of the heart lumen. Endothelial progenitor cells found in the SV and Endo build the majority of coronary vasculature, whereas the proepicardium contributes to a relatively small portion of it2. The process by which the capillary network of coronary vessels grow in the heart from its preexisting precursor cells is called coronary angiogenesis. Coronary artery disease is one of the leading causes of death worldwide and yet an effective treatment for this disease is lacking. Understanding the detailed cellular and molecular mechanisms of coronary angiogenesis can be useful in designing novel and effective therapies to repair and regenerate damaged coronary arteries.
Recently, a surge in our understanding of how coronary vessels develop has been in part achieved through the development of new tools and technologies. In particular, in vivo lineage labelling and advanced imaging technologies have been very useful in uncovering the cellular origin and differentiation pathways of coronary vessels9,10,11,12. Despite the advantages of these in vivo tools, there are limitations in terms of speed, flexibility, and accessibility. Therefore, robust in vitro model systems can complement in vivo systems to elucidate the cellular and molecular mechanisms of coronary angiogenesis in a high-throughput manner.
Here, we describe an in vitro model of coronary angiogenesis. We have developed an in vitro explant culture system to grow coronary vessels from two progenitor tissues, SV and Endo. With this model, we show that the in vitro tissue explant cultures grow coronary vessel sprouts when stimulated by growth medium. Additionally, the explant cultures grow rapidly compared to control when stimulated by vascular endothelial growth factor A (VEGF-A), a highly potent angiogenic protein. Furthermore, we found that the angiogenic sprouts from the SV culture undergo venous dedifferentiation (loss of COUP-TFII expression), a mechanism similar to SV angiogenesis in vivo1. These data suggest that the in vitro explant culture system faithfully reinstates angiogenic events that occur in vivo. Collectively, in vitro models of angiogenesis that are described here are ideal for probing cellular and molecular mechanisms of coronary angiogenesis in a high-throughput and accessible manner.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>100 x 20 MM Tissue Culture Dish</td>
			<td>Fisher Scientific</td>
			<td>877222</td>
			<td>Referred in the protocol as Petri dish</td>
		</tr>
		<tr>
			<td>24-well plates</td>
			<td>Fisher Scientific</td>
			<td>08-772-51</td>
			<td></td>
		</tr>
		<tr>
			<td>8.0 uM PET membrane culture inserts</td>
			<td>Millipore Sigma</td>
			<td>MCEP24H48</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor Donkey anti-rabbit 555</td>
			<td>Fisher Scientific</td>
			<td>A31572</td>
			<td>Secondary antibody</td>
		</tr>
		<tr>
			<td>Alexa Fluor Donkey anti-rat 488</td>
			<td>Fisher Scientific</td>
			<td>A21206</td>
			<td>Secondary antibody</td>
		</tr>
		<tr>
			<td>Angled Metal Probe</td>
			<td>Fine science tools</td>
			<td>10088-15</td>
			<td>Angled 45 degree, used for detecting deep plugs</td>
		</tr>
		<tr>
			<td>Anti- ERG 1/2/3 antibody</td>
			<td>Abcam</td>
			<td>Ab92513</td>
			<td>Primary antibody</td>
		</tr>
		<tr>
			<td>Anti- VE-Cadherin antibody</td>
			<td>Fisher Scientific</td>
			<td>BDB550548</td>
			<td>Primary antibody, manufacturer BD BioSciences</td>
		</tr>
		<tr>
			<td>CO2 gas tank</td>
			<td>Various suppliers</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 Incubator</td>
			<td>Fisher Scientific</td>
			<td>13998223</td>
			<td>For 37 &#176;C, 5% CO2 incubation</td>
		</tr>
		<tr>
			<td>Dissection stereomicrosope</td>
			<td>Leica</td>
			<td>S9i</td>
			<td>Leica S9i Stereomicroscope</td>
		</tr>
		<tr>
			<td>EBM-2 basal media</td>
			<td>Lonza</td>
			<td>CC-3156</td>
			<td>Endothelial cell growth basal media</td>
		</tr>
		<tr>
			<td>ECM solution</td>
			<td>Corning</td>
			<td>354230</td>
			<td>Commercially known as Matrigel</td>
		</tr>
		<tr>
			<td>EGM-2 MV Singlequots Kit</td>
			<td>Lonza</td>
			<td>CC-4147</td>
			<td>Microvascular endothelial cell supplement kit; This is mixed into the EBM-2 to make the EGM-2 complete media</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Fisher Scientific</td>
			<td>SH3007003IR</td>
			<td></td>
		</tr>
		<tr>
			<td>FiJi</td>
			<td>NIH</td>
			<td>NA</td>
			<td>Image processing software (<a href="https://imagej.net/Fiji/Downloads" target="_blank">https://imagej.net/Fiji/Downloads</a>)</td>
		</tr>
		<tr>
			<td>Fine Forceps</td>
			<td>Fine science tools</td>
			<td>11412-11</td>
			<td>Used for embryo dissection</td>
		</tr>
		<tr>
			<td>Fisherbrand Straight-Blade operating scissors</td>
			<td>Fisher Scientific</td>
			<td>13-808-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Hyclone Phosphate Buffered Saline (1X)</td>
			<td>Fisher Scientific</td>
			<td>SH-302-5601LR</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminar flow tissue culture hood</td>
			<td>Fisher Scientific</td>
			<td>various models available</td>
			<td></td>
		</tr>
		<tr>
			<td>Mounting Medium</td>
			<td>Vector Laboratories</td>
			<td>H-1200</td>
			<td>Vectashield with DAPI</td>
		</tr>
		<tr>
			<td>Paraformaldehyde (PFA)</td>
			<td>Electron Microscopy/Fisher</td>
			<td>50-980-494</td>
			<td>This is available at 32%; needs to be diluted to 4%</td>
		</tr>
		<tr>
			<td>Perforated spoon</td>
			<td>Fine science tools</td>
			<td>10370-18</td>
			<td>Useful in removing embryo/tissues from a solution</td>
		</tr>
		<tr>
			<td>Recombinant Murine VEGF-A 165</td>
			<td>PeproTech</td>
			<td>450-32</td>
			<td></td>
		</tr>
		<tr>
			<td>Standard forceps, Dumont #5</td>
			<td>Fine science tools</td>
			<td>11251-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Sure-Seal Mouse/Rat chamber</td>
			<td>Easysysteminc</td>
			<td>EZ-1785</td>
			<td>Euthanasia chamber</td>
		</tr>
	</tbody>
</table>

in vitro model of coronary angiogenesis

Here, we describe an in vitro culture assay to study coronary angiogenesis. Coronary vessels feed the heart muscle and are of clinical importance. Defects in these vessels represent severe health risks such as in atherosclerosis, which can lead to myocardial infarctions and heart failures in patients. Consequently, coronary artery disease is one of the leading causes of death worldwide. Despite its clinical importance, relatively little progress has been made on how to regenerate damaged coronary arteries. Nevertheless, recent progress has been made in understanding the cellular origin and differentiation pathways of coronary vessel development. The advent of tools and technologies that allow researchers to fluorescently label progenitor cells, follow their fate, and visualize progenies in vivo have been instrumental in understanding coronary vessel development. In vivo studies are valuable, but have limitations in terms of speed, accessibility, and flexibility in experimental design. Alternatively, accurate in vitro models of coronary angiogenesis can circumvent these limitations and allow researchers to interrogate important biological questions with speed and flexibility. The lack of appropriate in vitro model systems may have hindered the progress in understanding the cellular and molecular mechanisms of coronary vessel growth. Here, we describe an in vitro culture system to grow coronary vessels from the sinus venosus (SV) and endocardium (Endo), the two progenitor tissues from which many of the coronary vessels arise. We also confirmed that the cultures accurately recapitulate some of the known in vivo mechanisms. For instance, we show that the angiogenic sprouts in culture from SV downregulate COUP-TFII expression similar to what is observed in vivo. In addition, we show that VEGF-A, a well-known angiogenic factor in vivo, robustly stimulates angiogenesis from both the SV and Endo cultures. Collectively, we have devised an accurate in vitro culture model to study coronary angiogenesis.

One of the most striking features of SV angiogenesis in vivo is that it follows a specific pathway and involves cell dedifferentiation and redifferentiation events that occur at stereotypical times and positions1. As initial SV cells grow onto the heart ventricle, they stop producing venous markers such as COUP-TFII (Figure 7). Subsequently, coronary sprouts take two migration paths, either over the surface of the heart or deep within ...

Watch this Scientific Journal Video about In Vitro Model of Coronary Angiogenesis at JoVE.com

In Vitro Model of Coronary Angiogenesis

In vitro models of coronary angiogenesis can be utilized for the discovery of the cellular and molecular mechanisms of coronary angiogenesis. In vitro explant cultures of sinus venosus and endocardium tissues show robust growth in response to VEGF-A and display a similar pattern of COUP-TFII expression as in vivo.

Here, we describe an in vitro culture assay to study coronary angiogenesis. Coronary vessels feed the heart muscle and are of clinical importance. Defects ...

Our protocol is significant because it allows researchers to investigate the molecular mechanism of coronary angiogenesis outside of an organism. The main advantage of this technique is that it accurately models the process of coronary angiogenesis inside an organism, facilitating the study of the mechanisms of coronary angiogenesis. Begin by spraying a pregnant mouse carrying embryonic day 11.5 embryos with 70%ethanol.Lifting the skin over the belly with forceps, use scissors to make an abdominal skin and peritoneal incision laterally and anteriorly up to the diaphragm to expose the uterine horn. Grasping the uterus, cut the tissue free and pull out the uterine horn. Place the string of embryos into ice cold sterile PBS under a stereo microscope, and peel off the uterine muscle, yolk sac, and amnion cover from each embryo.As each embryo is isolated, use a perforated spoon to transfer the tissues into a new Petri dish containing sterile PBS on ice. To harvest the embryonic heart tissue, transfer the first embryo to be dissected into a new Petri dish under the microscope, and place the embryo in ventral side up. Use fine forceps to make a small incision in the chest, slightly above the diaphragm, and insert the closed forceps into the incision to enlarge the incision.Using the forceps to hold the chest wall open to expose the heart and lungs, use a second pair of forceps to gently move the heart anteriorly 90 degrees to expose the dorsal aorta and vein. Then, grasping these vessels at the base of the heart, carefully pull out the heart and lungs anteriorly and rinse the tissues with cold PBS. When all of the cardiac tissue has been harvested, place the heart samples under the microscope and remove the lung lobes from each heart.Orient the first heart on its dorsal side, and holding the heart at its base, use fine forceps to scrape the left and right atria in the adjacent tissue surrounding the SV from the heart. To isolate the SV, orient the heart dorsal side up. Carefully remove the SV from the heart and use a sterile transfer pipette to place the isolated tissue into a new six centimeter Petri dish containing ice cold sterile PBS on ice.To isolate the whole ventricles, remove the outflow tract and use a new sterile transfer pipette to place the ventricles into a separate six centimeter Petri dish containing ice cold sterile PBS on ice. To set up SV and whole ventricle cultures, first coat the membranes of one eight micrometer pore PET culture insert per well of a 24 well culture plate, with 100 microliters of freshly diluted extracellular matrix per culture for at least 30 minutes at 37 degrees Celsius. When the matrix has solidified, use a transfer pipette to transfer one explant onto each insert, and move the plate under the microscope.Using clean forceps, position the explants at the center of each insert to ensure that they are not attached to the side walls, and carefully remove any extra PBS. Next, transfer the plate with the lid closed under a laminar flow tissue culture hood, and add 100 microliters of pre-warmed complete medium to each insert, and 200 microliters to the well below each insert. Then add 300 microliters of PBS to any unused wells, and place the plate into the cell culture incubator for five days.For VEGF-A treatment on day two of culture, remove the medium from both chambers of each culture and add 100 microliters of PBS to each insert, and 200 microliters of PBS to each well. After swirling the plate a few times, replace the PBS with 300 microliters of basal medium supplemented with 1%fetal bovine serum to start the cultures, and return the plate to the incubator. On day three after starvation, add 300 microliters of fresh basal medium plus serum to the control wells and basal medium plus 50 nanograms per milliliter of VEGF-A to the treatment wells, and return the plate to the cell culture incubator.On the sixth day of culture, wash the chambers with PBS as demonstrated, and fix the cultures with 200 microliters of 4%paraformaldehyde in each well, and 100 microliters of fixative in each insert. After 20 minutes at 4 degrees Celsius with rocking, wash the cultures with 300 microliters of PBS for 10 minutes per wash with rocking at room temperature. After the last wash, add 300 microliters of primary antibody solution to the wells and inserts for an overnight culture at four degrees Celsius with rocking.The next morning, wash the cultures 10 times in non-ionic surfactant in PBS with rocking, changing the wash solution every 10 minutes before labeling the cultures with 300 microliters of an appropriate fluorophore conjugated secondary antibody at four degrees Celsius overnight with rocking. The next day, wash the cultures 10 times in fresh PBS with non-ionic surfactant as demonstrated. After the last wash, use fine forceps to carefully peel the membrane from each insert and place the membranes onto individual glass microscope slides, explant side up.Cover the samples with DAPI supplemented mounting medium in a cover slip, and seal the edges of the cover slips with clear nail polish. When the nail polish has dried, image the slides by confocal microscopy. As initial SV cells grow onto the heart ventricle, they stop producing venous markers such as Coup-TF2.After five days of culture, SV endothelial cells sprout and migrate onto the membrane. As in the embryonic heart, Coup-TF2 expression is reduced as the vessels migrate away from the SV.Cultures stimulated with VEGF-A exhibit an increased growth of angiogenic sprouts both in density and length. Further SV cultures stimulated by VEGF-A demonstrate an almost three-fold increase in sprout length compared to controls, suggesting that endothelial sprouts from SV and endocardium respond to VEGF-A.It is important not to lose the SV tissue while pulling out the heart and lungs, removing the atria, and cleaning the adjacent tissue surrounding the SV.Live imaging experiments can be performed to visualize coronary angiogenesis and to capture the details of cellular and molecular dynamics during the process. This technique is extremely useful for assessing potential molecular mechanisms of coronary angiogenesis and as a model system for studying angiogenesis in general.

Research

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