Name: the aortic ring co-culture assay: a convenient tool to assess the angiogenic potential of mesenchymal stromal cells in vitro
Uploaded: 2017-09-18T15:00:00
Description: Watch this Scientific Journal Video about The Aortic Ring Co-culture Assay: A Convenient Tool to Assess the Angiogenic Potential of Mesenchymal Stromal Cells In Vitro at JoVE.com

The authors thank the following staff members and research personnel: Andr&#233;e Gauthier-Fisher, Matthew Librach, Tanya Barretto, Tharsan Velauthapillai, and Sarah Laronde.

All studies involving animals were conducted and reported according to ARRIVE guidelines29. All studies were performed with institutional research ethics board approval (REB number 4276). All animal procedures were approved by the Animal Care Committee of the University Health Network (Toronto, Canada), and all animals received humane care in compliance with the Guide for the Care and Use of Laboratory Animals, 8th edition (National institutes of Health 2011).
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<ol>
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D., Laschke, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Geraniol+Suppresses+Angiogenesis+by+Downregulating+Vascular+Endothelial+Growth+Factor+(VEGF)/VEGFR-2+Signaling.">Geraniol Suppresses Angiogenesis by Downregulating Vascular Endothelial Growth Factor (VEGF)/VEGFR-2 Signaling.</a> PLoS One. 10 (7), e0131946 (2015).</li><li>Masson, V. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+Aortic+Ring+Assay:+A+New+Approach+of+the+Molecular+Genetics+of+Angiogenesis.">Mouse Aortic Ring Assay: A New Approach of the Molecular Genetics of Angiogenesis.</a> Biol Proced Online. 4, 24-31 (2002).</li><li>Caplan, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adult+mesenchymal+stem+cells+for+tissue+engineering+versus+regenerative+medicine.">Adult mesenchymal stem cells for tissue engineering versus regenerative medicine.</a> J Cell Physiol. 213 (2), 341-347 (2007).</li><li>Caplan, A. I., Dennis, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesenchymal+stem+cells+as+trophic+mediators.">Mesenchymal stem cells as trophic mediators.</a> J Cell Biochem. 98 (5), 1076-1084 (2006).</li><li>Keating, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesenchymal+stromal+cells:+new+directions.">Mesenchymal stromal cells: new directions.</a> Cell Stem Cell. 10 (6), 709-716 (2012).</li><li>Kilroy, G. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytokine+profile+of+human+adipose-derived+stem+cells:+expression+of+angiogenic,+hematopoietic,+and+pro-inflammatory+factors.">Cytokine profile of human adipose-derived stem cells: expression of angiogenic, hematopoietic, and pro-inflammatory factors.</a> J Cell Physiol. 212 (3), 702-709 (2007).</li><li>Tang, Y. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paracrine+action+enhances+the+effects+of+autologous+mesenchymal+stem+cell+transplantation+on+vascular+regeneration+in+rat+model+of+myocardial+infarction.">Paracrine action enhances the effects of autologous mesenchymal stem cell transplantation on vascular regeneration in rat model of myocardial infarction.</a> Ann Thorac Surg. 80 (1), 229-236 (2005).</li><li>Caplan, A. 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There are several critical stages in setting up a successful aortic ring assay MSC co-culture experiment. First, the most important steps when isolating and sectioning aorta are: 1) obtaining exclusively the thoracic segment of aorta; 2) carefully removing branching blood vessels, connective and adipose tissue and; 3) cutting even sections of the aorta (~1 mm) to limit variability between each assay. Second, the successful embedding of aortic rings into BME is critical for this assay. If the BME is not completely polymer...

The complex process of angiogenesis improves and maintains tissue perfusion by promoting new blood vessel development from pre-existing vasculature1. It is a tightly regulated, balanced process by pro-angiogenic and anti-angiogenic factors. Any deficiency in this system may lead to insufficient vessel maintenance or growth, causing severe ischemic diseases including myocardial disease, stroke, and neurodegenerative disorders. However, exaggerated vascular development is characteristic for conditions including cancer and inflammatory disorders2.
Developing therapies that aim to control angiogenesis to achieve favorable tissue regeneration is of key importance. Despite extensive preclinical and clinical investigations, attempts to stimulate angiogenesis using pro-angiogenic factors and microRNAs have failed to achieve desired outcomes3,4,5. Possible reasons for the transient effects include: limited longevity of angiogenic proteins and nucleic acids, and the finite number of targeted growth factors6,7. Although soluble angiogenic factors are essential for initiating angiogenesis, the maintenance and functionality of vasculature depend on supporting cell types including pericytes and smooth muscle cells8. The field of pro-angiogenic therapies is now exploring potential stem cell and progenitor cell sources that may provide angiogenic factors locally, while physically supporting newly developed vasculature, self-renewing or even differentiating into endothelial-like cells9,10. Finding the optimal angiogenic cell types with the capability to fulfill these functional requirements holds a great promise for ischemic tissue regeneration.
In order to successfully translate potential cell-based therapies into clinical trials, pre-clinical studies need to demonstrate their efficacy and highlight the underlying angiogenic mechanisms. Despite the high number of established angiogenesis assays, the field lacks a &#34;gold-standard&#34; in vitro assay that could reliably evaluate the efficacy of potential candidate cell types11,12,13. Most in vitro angiogenesis assays (including the endothelial proliferation, migration and tube formation assays) typically assess the effects of cells or compounds on endothelial cells&#39; phenotypical changes or differentiation into tubular and network structures14,15. While these features are critical for angiogenesis, a &#34;translatable&#34; assay should also evaluate: 1) the augmentation or replacement of the supporting cell types including pericytes or smooth muscle cells, 2) the processing of ECM and/or basement membrane, and 3) the efficiency to promote the formation of functional microvasculature. In vivo angiogenesis models, including the corneal assay and Matrigel plug assay, recapitulate the unique in vivo microenvironment but are challenged by the difficulty of tracking administered cells to observe physical interactions. Furthermore, in in vivo models, xeno-immune rejection can occur while testing potential allogeneic cell therapy candidates16. Ex vivo angiogenesis models, particularly the aortic ring assay can provide: 1) easy observation and quantification of tubular structures, 2) accessory supportive cells, 3) ECM from host and artificial supplies, 4) exclusion of inflammatory components, and 5) quick and inexpensive setup17,18. Typically, the aortic ring assay can test the angiogenic potential of small secretory proteins, pharmacological agents, and transgenic rodent models19,20,21.
MSCs are promising candidates for vascular regeneration primarily through their paracrine-mediated effects22,23,24. MSCs have been shown to secrete key angiogenic factors including Vascular Endothelial Growth Factor (VEGF), Hepatocyte Growth Factor (HGF), Insulin-like Growth Factor-1 (IGF-1), basic Fibroblast Growth Factor (bFGF), and angiopoeitin-1 (Ang-1)25,26. MSCs can also detect and home to ischemic or inflamed tissues, however, the exact mechanisms are still under investigation. Increasingly, the literature supports the hypothesis that most MSCs arise from perivascular cells, co-express pericyte markers, and can behave like pericytes27. HUCPVCs are a young source of MSCs derived from the perivascular region of the human umbilical cord. They represent a population of MSCs with pericyte-like properties and have been characterized from both FTM and term umbilical cords. FTM HUCPVCs demonstrate a high expression of pericyte markers including CD146 and NG2, high proliferative and multilineage potential, immune-privileged properties, and display a robust paracrine profile28. FTM HUCPVCs are an ideal candidate cell type to promote regeneration of injured tissue through the promotion of new vasculature via their pericyte-like properties.
To test the angiogenic potential and pericyte-like properties of human MSCs, a very limited number of angiogenesis assays are available where positive angiotropic migration (hereafter referred to as &#34;homing&#34;), ECM processing, and development of physical interactions between cell types can be investigated, while obtaining quantitative data on microvasculature development.
Hereby we present a protocol that describes a novel application of the aortic ring assay. Human MSCs were co-cultured with developing rat-derived aortic endothelial networks to assess their contribution to tube formation, maturation, and homeostasis. This version of the aortic ring assay assesses the ability and potency of cell therapy candidates to home to sites of angiogenesis, perform and mediate ECM processing, and contribute to endothelial tubular development through establishing pericyte-like physical interactions. In addition to quantifying the net effect of MSCs on in vitro endothelial network formation and observing intercellular interactions, we also optimized a protocol to isolate MSCs from co-cultures. By performing flow cytometry and qPCR, it is possible to characterize changes in MSC phenotype and gene expression following co-culture. As model cell types, we compared ontogenetically early (prenatal) and late (adult) sources of human MSCs: FTM HUCPVCs and human bone marrow-derived MSCs (BMSC), respectively, in the aortic ring assay. We propose that the aortic ring assay can be used to study the angiogenic potential of any physically supporting cell type when under investigation for angiogenic regenerative applications.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >Alpha-MEM</td>
			<td >Gibco</td>
			<td >12571071</td>
			<td >For FTM HUCPVC and BMSC culture media.</td>
		</tr>
		<tr >
			<td >APC-conjugated anti human TRA-1-85</td>
			<td >R&#38;D Systems</td>
			<td >FAB3195A</td>
			<td >Human-specific cell marker for flow cytometry and cell sorting</td>
		</tr>
		<tr >
			<td >Basal membrane extract (BME) (Matrigel)</td>
			<td >Corning</td>
			<td >354234</td>
			<td >For aorta embedding</td>
		</tr>
		<tr >
			<td >Bullet-kit</td>
			<td >Lonza</td>
			<td >CC-3162</td>
			<td >Includes: Gentamicin/Amphotericin-B 
			(GA)human Epidermal 
			Growth Factor (hEGF); Vascular 
			Endothelial Growth Factor (VEGF); R3- 
			Insulin-like Growth Factor-1 (R3-IGF-1); 
			Ascorbic Acid; Hydrocortisone; 
			human Fibroblast Growth Factor-Beta (hFGF-&#946;); Heparin; Fetal Bovine Serum 
			(FBS). Required to prepare EGM</td>
		</tr>
		<tr >
			<td >CellTracker Green CMFDA Dye</td>
			<td >Thermo-fisher</td>
			<td >C2925</td>
			<td >For staining MSCs, green is picked up optimally by MSCs</td>
		</tr>
		<tr >
			<td >CKX53 Culture Microscope</td>
			<td >Olympus</td>
			<td ></td>
			<td >For bright-field imaging of endothelial network development</td>
		</tr>
		<tr >
			<td >Countess automated cell counter</td>
			<td >Invitrogen</td>
			<td >C10227</td>
			<td >Cell counting for MSC culture, flow cytometry and qPCR</td>
		</tr>
		<tr >
			<td >Dispase</td>
			<td >StemCell technologies</td>
			<td >7923</td>
			<td >For dissociating aortic ring-MSC co-cultures (pre-warm at 37 &#176;C)</td>
		</tr>
		<tr >
			<td >Disposable sterile scalpels</td>
			<td >VWR</td>
			<td >21909-654</td>
			<td >For sectioning aorta</td>
		</tr>
		<tr >
			<td >Dulbecco&#39;s phosphate buffered saline</td>
			<td >Sigma-Aldrich</td>
			<td >D8537</td>
			<td >PBS. 1X, Without calcium chloride and magnesium chloride</td>
		</tr>
		<tr >
			<td >Endothelial basal media (EBM)</td>
			<td >Lonza</td>
			<td >CC-3156</td>
			<td >Basal media required for culturing aortic ring assay-MSC co-cultures (warm at 37 &#176;C before use). Required for EGM and EBM-FBS</td>
		</tr>
		<tr >
			<td >Ethanol, 70%, Biotechnology Grade</td>
			<td >VWR</td>
			<td >97064-768</td>
			<td >To sterilize surfaces</td>
		</tr>
		<tr >
			<td >EVOS</td>
			<td >Life Technologies</td>
			<td ></td>
			<td >In-house fluorescent microscope to track MSC migration and integration</td>
		</tr>
		<tr >
			<td >Fetal bovine serum (FBS) (Hyclone)</td>
			<td >GE Healthcare</td>
			<td >SH3039603</td>
			<td >Serum component of cell culture medium</td>
		</tr>
		<tr >
			<td >FITC-conjugated anti-CD31 antibody</td>
			<td >BD</td>
			<td >558068</td>
			<td >Human endothelial marker for flow cytometry</td>
		</tr>
		<tr >
			<td >FITC-conjugated anti-CD146antibody</td>
			<td >BD</td>
			<td >560846</td>
			<td >Human pericyte marker for flow cytometry</td>
		</tr>
		<tr >
			<td >Forceps</td>
			<td >Almedic</td>
			<td >7727-A10-704</td>
			<td >For handing rat tissue. Can use any similar forceps</td>
		</tr>
		<tr >
			<td >Hank&#39;s Balanced Salt Solution (HBSS)</td>
			<td >Life Technologies</td>
			<td >14175-094</td>
			<td >1X Without calcium chloride and magnesium chloride</td>
		</tr>
		<tr >
			<td >HERAcell 150i CO2 Incubator</td>
			<td >Thermo Fisher Scientific</td>
			<td >51026410</td>
			<td >For incubating cells</td>
		</tr>
		<tr >
			<td >Human Angiogenesis RT2 profiler PCR array</td>
			<td >Qiagen</td>
			<td >PAHS-024Z</td>
			<td >Human specific and includes primers for 84 genes involved in angiogenesis. Each well is 1 primer reaction</td>
		</tr>
		<tr >
			<td >ImageJ</td>
			<td ></td>
			<td ></td>
			<td >Open source image processing software. Require Angiogenesis analyzer plugin</td>
		</tr>
		<tr >
			<td >LSR II</td>
			<td >BD</td>
			<td ></td>
			<td >UHN SickKids FC Facility. For flow cytometry.</td>
		</tr>
		<tr >
			<td >MoFlo Astrios</td>
			<td >Beckman Coulter</td>
			<td ></td>
			<td >UHN SickKids FC Facility. For cell sorting.</td>
		</tr>
		<tr >
			<td >Penicillin/streptomycin</td>
			<td >Gibco</td>
			<td >15140122</td>
			<td >Antibiotic component to buffers and cell culture medium</td>
		</tr>
		<tr >
			<td >RNeasy Mini Kit</td>
			<td >Qiagen</td>
			<td >74104</td>
			<td >For RNA purification. Includes cell lysis buffer</td>
		</tr>
		<tr >
			<td >RT2Easy First Strand Kit</td>
			<td >Qiagen</td>
			<td >330421</td>
			<td >For preparation of cDNA for qPCR</td>
		</tr>
		<tr >
			<td >RT2PreAMP cDNA Synthesis Kit</td>
			<td >Qiagen</td>
			<td >330451</td>
			<td >Pre-amplification of cDNA if low-yield RNA</td>
		</tr>
		<tr >
			<td >Surgical scissors</td>
			<td >Fine Science Tools</td>
			<td >14059-11</td>
			<td >For cutting skin, muscle and aorta</td>
		</tr>
		<tr >
			<td >Sterile gauze</td>
			<td >VWR</td>
			<td >3084</td>
			<td >To dampen and sterilize chest fur</td>
		</tr>
		<tr >
			<td >TrypleE</td>
			<td >Thermo Fisher Scientific</td>
			<td>12605036</td>
			<td >MSC dissociation enzyme pre-warm at 37 &#176;C</td>
		</tr>
		<tr >
			<td >0.2 &#956;m pore filtration unit</td>
			<td >Thermo Fisher Scientific</td>
			<td >566-0020</td>
			<td >To sterilize tissue culture media</td>
		</tr>
		<tr >
			<td >0.25% Trypsin/EDTA</td>
			<td >Gibco</td>
			<td >25200056</td>
			<td >For cell dissociation, pre-warm at 37 &#176;C</td>
		</tr>
		<tr >
			<td >10 cm tissue culture dishes</td>
			<td >Corning</td>
			<td >25382-428</td>
			<td >For cleaning and sectioning aorta and MSC cell culture</td>
		</tr>
		<tr >
			<td >12 well-cell culture plates</td>
			<td >Corning-Sigma Aldrich</td>
			<td >CLS3513</td>
			<td >For setting up aortic ring assay-MSC co-cultures</td>
		</tr>
		<tr >
			<td >15 mL tube</td>
			<td >BD Falcon</td>
			<td >352096</td>
			<td >For general tissue culture procedures</td>
		</tr>
		<tr >
			<td >70 &#956;m cell strainer</td>
			<td >Fisherbrand</td>
			<td >22363548</td>
			<td >To ensure a single cell suspension before flow cytometry or sorting</td>
		</tr>
	</tbody>
</table>

the aortic ring co-culture assay: a convenient tool to assess the angiogenic potential of mesenchymal stromal cells in vitro

Angiogenesis is a complex, highly regulated process responsible for providing and maintaining adequate tissue perfusion. Insufficient vasculature maintenance and pathological malformations can result in severe ischemic diseases, while overly abundant vascular development is associated with cancer and inflammatory disorders. A promising form of pro-angiogenic therapy is the use of angiogenic cell sources, which can provide regulatory factors as well as physical support for newly developing vasculature.
Mesenchymal Stromal Cells (MSCs) are extensively investigated candidates for vascular regeneration due to their paracrine effects and their ability to detect and home to ischemic or inflamed tissues. In particular, first trimester human umbilical cord perivascular cells (FTM HUCPVCs) are a highly promising candidate due to their pericyte-like properties, high proliferative and multilineage potential, immune-privileged properties, and robust paracrine profile. To effectively evaluate potentially angiogenic regenerative cells, it is a requisite to test them in reliable and &#34;translatable&#34; pre-clinical assays. The aortic ring assay is an ex vivo angiogenesis model that allows for easy quantification of tubular endothelial structures, provides accessory supportive cells and extracellular matrix (ECM) from the host, excludes inflammatory components, and is fast and inexpensive to set up. This is advantageous when compared to in vivo models (e.g., corneal assay, Matrigel plug assay); the aortic ring assay can track the administered cells and observe intercellular interactions while avoiding xeno-immune rejection.
We present a protocol for a novel application of the aortic ring assay, which includes human MSCs in co-cultures with developing rat aortic endothelial networks. This assay allows for the analysis of the MSC contribution to tube formation and development through physical pericyte-like interactions and of their potency for actively migrating to sites of angiogenesis, and for evaluating their ability to perform and mediate ECM processing. This protocol provides further information on changes in MSC phenotype and gene expression following co-culture.

The schematic work-flow for establishing the aortic ring/MSC co-culture assay is demonstrated in Figure 1. The main steps include: rat aorta isolation, sectioning and embedding of the aortic rings, monitoring the endothelial sprouting and network development, and finally labelling and administering the MSCs. The timeline of the endothelial network analysis outlines the window for the analyses feasible for each period of co-culturing: day 1, 5 &#38;&#160;7. Ad...

Watch this Scientific Journal Video about The Aortic Ring Co-culture Assay: A Convenient Tool to Assess the Angiogenic Potential of Mesenchymal Stromal Cells In Vitro at JoVE.com

The Aortic Ring Co-culture Assay: A Convenient Tool to Assess the Angiogenic Potential of Mesenchymal Stromal Cells In Vitro

Here, we present a novel application of the aortic ring assay where prelabelled mesenchymal cells are co-cultured with rat aorta-derived endothelial networks. This novel method allows visualization of Mesenchymal Stromal Cells (MSCs) homing and integration with endothelial networks, quantification of network properties, and evaluation of MSC immunophenotypes and gene expression.

The Aortic Ring Co-culture Assay: A Convenient Tool to Assess the Angiogenic Potential of Mesenchymal Stromal Cells In Vitro

Angiogenesis is a complex, highly regulated process responsible for providing and maintaining adequate tissue perfusion. Insufficient vasculature ...

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