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

JoVE Journal

Medicine

Coronary Artery Ligation and Intramyocardial Injection in a Murine Model of Infarction

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo. With the advent of genetic modifications to the whole organism or the myocardium and an array of biological and/or synthetic materials, there is great potential for any combination of these to assuage the extent of acute ischemic injury and impede the onset of heart failure pursuant to myocardial remodeling. 
Here we present the methods and materials used to reliably perform this microsurgery and the modifications involved for temporary (with reperfusion) or permanent coronary artery occlusion studies as well as intramyocardial injections. The effects on the heart that can be seen during the procedure and at the termination of the experiment in addition to histological evaluation will verify efficacy. 
Briefly, surgical preparation involves anesthetizing the mice, removing the fur on the chest, and then disinfecting the surgical area. Intratracheal intubation is achieved by transesophageal illumination using a fiber optic light. The tubing is then connected to a ventilator. An incision made on the chest exposes the pectoral muscles which will be cut to view the ribs. For ischemia/reperfusion studies, a 1 cm piece of PE tubing placed over the heart is used to tie the ligature to so that occlusion/reperfusion can be customized. For intramyocardial injections, a Hamilton syringe with sterile 30gauge beveled needle is used. When the myocardial manipulations are complete, the rib cage, the pectoral muscles, and the skin are closed sequentially. Line block analgesia is effected by 0.25% marcaine in sterile saline which is applied to muscle layer prior to closure of the skin. The mice are given a subcutaneous injection of saline and placed in a warming chamber until they are sternally recumbent. They are then returned to the vivarium and housed under standard conditions until the time of tissue collection. At the time of sacrifice, the mice are anesthetized, the heart is arrested in diastole with KCl or BDM, rinsed with saline, and immersed in fixative. Subsequently, routine procedures for processing, embedding, sectioning, and histological staining are performed. 
Nonsurgical intubation of a mouse and the microsurgical manipulations described make this a technically challenging model to learn and achieve reproducibility. These procedures, combined with the difficulty in performing consistent manipulations of the ligature for timed occlusion(s) and reperfusion or intramyocardial injections, can also affect the survival rate so optimization and consistency are critical.

Numerous genetic manipulations and/or intramyocardial injections of genes, proteins, cells, and/or biomaterials are superimposed upon the dimension of time in studies of acute ischemia/ reperfusion injury and chronic remodeling in mice. This video illustrates the microsurgical procedures for ischemia/reperfusion, permanent coronary artery ligation, and intramyocardial injection studies.

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo.  With the advent of genetic modifications to ...

A Mouse Model of the Cornea Pocket Assay for Angiogenesis Study

A normal cornea is clear of vascular tissues. However, blood vessels can be induced to grow and survive in the cornea when potent angiogenic factors are administered 1. This uniqueness has made the cornea pocket assay one of the most used models for angiogenesis studies. The cornea composes multiple layers of cells. It is therefore possible to embed a pellet containing the angiogenic factor of interest in the cornea to investigate its angiogenic effect 2,3. Here, we provide a step by step demonstration of how to (I) produce the angiogenic factor-containing pellet (II) embed the pellet into the cornea (III) analyze the angiogenesis induced by the angiogenic factor of interest. Since the basic fibroblast growth factor (bFGF) is known as one of the most potent angiogenic factors 4, it is used here to induce angiogenesis in the cornea.

The cornea is unique in that it lacks vascular tissues. However, robust blood vessel growth and survival can be induced in the cornea by potent angiogenic factors. Therefore, the cornea can provide with us a valuable tool for angiogenic studies. This protocol demonstrates how to perform the mouse model of cornea pocket assay and how to assess the angiogenesis induced by angiogenic factors using this model.

A normal cornea is clear of vascular tissues. However, blood vessels can be induced to grow and survive in the cornea when potent angiogenic factors are ...

Multi-modal Imaging of Angiogenesis in a Nude Rat Model of Breast Cancer Bone Metastasis Using Magnetic Resonance Imaging, Volumetric Computed Tomography and Ultrasound

Angiogenesis is an essential feature of cancer growth and metastasis formation. In bone metastasis, angiogenic factors are pivotal for tumor cell proliferation in the bone marrow cavity as well as for interaction of tumor and bone cells resulting in local bone destruction. Our aim was to develop a model of experimental bone metastasis that allows in vivo assessment of angiogenesis in skeletal lesions using non-invasive imaging techniques.
For this purpose, we injected 105 MDA-MB-231 human breast cancer cells into the superficial epigastric artery, which precludes the growth of metastases in body areas other than the respective hind leg1. Following 25-30 days after tumor cell inoculation, site-specific bone metastases develop, restricted to the distal femur, proximal tibia and proximal fibula1. Morphological and functional aspects of angiogenesis can be investigated longitudinally in bone metastases using magnetic resonance imaging (MRI), volumetric computed tomography (VCT) and ultrasound (US).
MRI displays morphologic information on the soft tissue part of bone metastases that is initially confined to the bone marrow cavity and subsequently exceeds cortical bone while progressing. Using dynamic contrast-enhanced MRI (DCE-MRI) functional data including regional blood volume, perfusion and vessel permeability can be obtained and quantified2-4. Bone destruction is captured in high resolution using morphological VCT imaging. Complementary to MRI findings, osteolytic lesions can be located adjacent to sites of intramedullary tumor growth. After contrast agent application, VCT angiography reveals the macrovessel architecture in bone metastases in high resolution, and DCE-VCT enables insight in the microcirculation of these lesions5,6. US is applicable to assess morphological and functional features from skeletal lesions due to local osteolysis of cortical bone. Using B-mode and Doppler techniques, structure and perfusion of the soft tissue metastases can be evaluated, respectively. DCE-US allows for real-time imaging of vascularization in bone metastases after injection of microbubbles7.
In conclusion, in a model of site-specific breast cancer bone metastases multi-modal imaging techniques including MRI, VCT and US offer complementary information on morphology and functional parameters of angiogenesis in these skeletal lesions.

In the pathogenesis of bone metastasis, angiogenesis is a crucial process and therefore represents a target for imaging and therapy. Here, we present a rat model of site-specific breast cancer bone metastasis and describe strategies to non-invasively image angiogenesis in vivo using magnetic resonance imaging, volumetric computed tomography and ultrasound.

Angiogenesis is an essential feature of cancer growth and metastasis formation. In bone metastasis, angiogenic factors are pivotal for tumor cell ...

Angiogenesis in the Ischemic Rat Lung

The adult lung is perfused by both the systemic bronchial artery and the entire venous return flowing through the pulmonary arteries. In most lung pathologies, it is the smaller systemic vasculature that responds to a need for enhanced lung perfusion and shows robust neovascularization. Pulmonary vascular ischemia induced by pulmonary artery obstruction has been shown to result in rapid systemic arterial angiogenesis in man as well as in several animal models. Although the histologic assessment of the time course of bronchial artery proliferation in rats was carefully described by Weibel 1, mechanisms responsible for this organized growth of new vessels are not clear. We provide surgical details of inducing left pulmonary artery ischemia in the rat that leads to bronchial neovascularization. Quantification of the extent of angiogenesis presents an additional challenge due to the presence of the two vascular beds within the lung. Methods to determine functional angiogenesis based on labeled microsphere injections are provided.

The lung is perfused by both the systemic bronchial artery and pulmonary arteries. In most lung pathologies, it is the smaller systemic vasculature that shows robust neovascularization. Cessation of pulmonary blood flow promotes brisk bronchial angiogenesis. We provide surgical details of inducing left pulmonary artery ischemia that promotes bronchial neovascularization.

The  adult lung is perfused by both the systemic bronchial artery and the entire  venous return flowing through the pulmonary arteries. In most lung ...

Retinal Detachment Model in Rodents by Subretinal Injection of Sodium Hyaluronate

Subretinal injection of sodium hyaluronate is a widely accepted method of inducing retinal detachment (RD). However, the height and duration of RD or the occurrence of subretinal hemorrhage can affect photoreceptor cell death in the detached retina. Hence, it is advantageous to create reproducible RDs without subretinal hemorrhage for evaluating photoreceptor cell death. We modified a previously reported method to create bullous and persistent RDs in a reproducible location with rare occurrence of subretinal hemorrhage. The critical step of this modified method is the creation of a self-sealing scleral incision, which can prevent leakage of sodium hyaluronate after injection into the subretinal space. To make the self-sealing scleral incision, a scleral tunnel is created, followed by scleral penetration into the choroid with a 30 G needle. Although choroidal hemorrhage may occur during this step, astriction with a surgical spear reduces the rate of choroidal hemorrhage. This method allows a more reproducible and reliable model of photoreceptor death in diseases that involve RD such as rhegmatogenous RD, retinopathy of prematurity, diabetic retinopathy, central serous chorioretinopathy, and age-related macular degeneration (AMD).

Creating experimental retinal detachments with a reproducible and sustained height of detachment, and without subretinal hemorrhage, is important for studying the pathophysiology of photoreceptor cell loss in retinal disease and evaluating potential therapeutic interventions. Here, we report such a method in detail.

Subretinal injection of sodium hyaluronate is a widely accepted method of inducing retinal detachment (RD). However, the height and duration of RD or the ...

Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow reserve (CFR) in humans. Reduced CFR is accompanied by marked intramyocardial and pericoronary fibrosis and is used as an indication of the severity of dysfunction. This study explores, step-by-step, the real-time changes measured in the coronary flow velocity, CFR and systolic to diastolic peak velocity (S/D) ratio in the setting of an aortic banding model in mice. By using a Doppler transthoracic imaging technique that yields reproducible and reliable data, the method assesses changes in flow in the septal coronary artery (SCA), for a period of over two weeks in mice, that previously either underwent aortic banding or thoracotomy. 
During imaging, hyperemia in all mice was induced by isoflurane, an anesthetic that increased coronary flow velocity when compared with resting flow. All images were acquired by a single imager. Two ratios, (1) CFR, the ratio between hyperemic and baseline flow velocities, and (2) systolic (S) to diastolic (D) flow were determined, using a proprietary software and by two independent observers. Importantly, the observed changes in coronary flow preceded LV dysfunction as evidenced by normal LV mass and fractional shortening (FS). 
The method was benchmarked against the current gold standard of coronary assessment, histopathology. The latter technique showed clear pathologic changes in the coronary artery in the form of peri-coronary fibrosis that correlated to the flow changes as assessed by echocardiography. 
The study underscores the value of using a non-invasive technique to monitor coronary circulation in mouse hearts. The method minimizes redundant use of research animals and demonstrates that advanced ultrasound-based indices, such as CFR and S/D ratios, can serve as viable diagnostic tools in a variety of investigational protocols including drug studies and the study of genetically modified strains.

Coronary flow reserve (CFR) is useful for assessment of myocardial oxygen demand and evaluation of cardiovascular risk. This study establishes a step-by-step transthoracic Doppler echocardiographic (TTDE) method for longitudinal monitoring of the changes in CFR, as measured from coronary artery in mice, under the experimental pressure overload of aortic banding.

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Assessing Therapeutic Angiogenesis in a Murine Model of Hindlimb Ischemia

Critical limb ischemia (CLI) is a serious condition that entails a high risk of lower limb amputation. Despite revascularization being the gold-standard therapy, a considerable number of CLI patients are not suited for either surgical or endovascular revascularization. Angiogenic therapies are emerging as an option for these patients but are currently still under investigation. Before application in humans, those therapies must be tested in animal models and its mechanisms must be clearly understood. An animal model of hindlimb ischemia (HLI) has been developed by the ligation and excision of the distal external iliac and femoral arteries and veins in mice. A comprehensive panel of tests was assembled to assess the effects of ischemia and putative angiogenic therapies at functional, histologic and molecular levels. Laser Doppler was used for the flow measurement and functional assessment of perfusion. Tissue response was evaluated by the analysis of capillary density after staining with the anti-CD31 antibody on histological sections of gastrocnemius muscle and by measurement of collateral vessel density after diaphonization. Expression of angiogenic genes was quantified by RT-PCR targeting selected angiogenic factors exclusively in endothelial cells (ECs) after laser capture microdissection from mice gastrocnemius muscles. These methods were sensitive in identifying differences between ischemic and non-ischemic limbs and between treated and non-treated limbs. This protocol provides a reproducible model of CLI and a framework for testing angiogenic therapies.

Here, a critical hindlimb ischemia experimental model is presented followed by a battery of functional, histologic and molecular tests&#160;to assess the effectiveness of angiogenic therapies.&#8203;

Critical limb ischemia (CLI) is a serious condition that entails a high risk of lower limb amputation. Despite revascularization being the gold-standard ...

Left Coronary Artery Ligation: A Surgical Murine Model of Myocardial Infarction

Ischemic heart disease and subsequent myocardial infarction (MI) is one of the leading causes of mortality in the United States and around the world. In order to explore the pathophysiological changes after myocardial infarction and design future treatments, research models of MI are required. Permanent ligation of the left coronary artery (LCA) in mice is a popular model to investigate cardiac function and ventricular remodeling post MI. Here we describe a less invasive, reliable, and reproducible surgical murine MI model by permanent ligation of the LCA. Our surgical model comprises of an easily reversible general anesthesia, endotracheal intubation that does not require a tracheotomy, and a thoracotomy. Electrocardiography and troponin measurement should be performed to ensure MI. Echocardiography at day 28 after MI will discern heart function and heart failure parameters. The degree of cardiac fibrosis can be evaluated by Masson's trichrome staining and cardiac MRI. This MI model is useful for studying the pathophysiological and immunological alterations after MI.

Presented here is a surgical procedure for permanent ligation of the left coronary artery in mice. This model can be used to investigate the pathophysiology and associated inflammatory response after myocardial infarction.

Ischemic heart disease and subsequent myocardial infarction (MI) is one of the leading causes of mortality in the United States and around the world. In ...

Adjunctive Exosome Therapy: Enhancing Myocardial Recovery Post-CABG Surgery

Surgical Porcine Model of Chronic Myocardial Ischemia Treated by Exosome-laden Collagen Patch and Off-pump Coronary Artery Bypass Graft

Chronic myocardial ischemia resulting from progressive coronary artery stenosis leads to hibernating myocardium (HIB), defined as myocardium that adapts to reduced oxygen availability by reducing metabolic activity, thereby preventing irreversible cardiomyocyte injury and infarction. This is distinct from myocardial infarction, as HIB has the potential for recovery with revascularization. Patients with significant coronary artery disease (CAD) experience chronic ischemia, which puts them at risk for heart failure and sudden death. The standard surgical intervention for severe CAD is coronary artery bypass graft surgery (CABG), but it has been shown to be an imperfect therapy, yet no adjunctive therapies exist to recover myocytes adapted to chronic ischemia. To address this gap, a surgical model of HIB using porcine that is amenable to CABG and mimics the clinical scenario was used. The model involves two surgeries. The first operation involves implanting a 1.5 mm rigid constrictor on the left anterior descending (LAD) artery. As the animal grows, the constrictor gradually causes significant stenosis resulting in reduced regional systolic function. Once the stenosis reaches 80%, the myocardial flow and function are impaired, creating HIB. An off-pump CABG is then performed with the left internal mammary artery (LIMA) to revascularize the ischemic region. The animal recovers for one month to allow for optimal myocardial improvement prior to sacrifice. This allows for physiologic and tissue studies of different treatment groups. This animal model demonstrates that cardiac function remains impaired despite CABG, suggesting the need for novel adjunctive interventions. In this study, a collagen patch embedded with mesenchymal stem cell (MSC)-derived exosomes was developed, which can be surgically applied to the epicardial surface distal to LIMA anastomosis. The material conforms to the epicardium, is absorbable, and provides the scaffold for the sustained release of signaling factors. This regenerative therapy can stimulate myocardial recovery that does not respond to revascularization alone. This model translates to the clinical arena by providing means of physiological and mechanistic explorations regarding recovery in HIB.

Author Spotlight: Enhancing Coronary Artery Revascularization

This study presents a surgical porcine model of chronic myocardial ischemia due to progressive coronary artery stenosis, resulting in impaired cardiac function without infarction. Following ischemia, animals undergo off-pump coronary artery bypass graft with epicardial placement of stem cells-derived exosomes-laden collagen patch. This adjunctive therapy improves myocardial function and recovery.

Chronic myocardial ischemia resulting from progressive coronary artery stenosis leads to hibernating myocardium (HIB), defined as myocardium that adapts ...