ACD is supported by a grant from the National Institute of Health (R01-CA177875). LX is a fellow in the HHMI-funded translational medicine program at UNC Chapel Hill. JVM is supported by a T32 pre-doctoral fellowship from the Integrative Vascular Biology Program at UNC Chapel Hill. We thank Clayton Davis for assistance with confocal microscopy.

The following protocol is carried out according to guidelines established by the Department of Laboratory Animal Medicine at the University of North Carolina at Chapel Hill.
1. Prepare the Following Material and Reagents Before Starting
<ol>
	<li>Prepare EC media by supplementing 400 ml&#160;low glucose (1 g/L D-glucose or LG) Dulbecco&#39;s Modified Eagle&#39;s medium (DMEM) with 50 ml heat-inactivated fetal bovine serum, 50 ml Nu-Serum IV, 5 ml antibiotic-antimycotic, and the hFGF, VEGF, h...

<ol>
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Med. 3 (66), 66ra5 (2011).</li><li>Calabrese, 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=A+perivascular+niche+for+brain+tumor+stem+cells.">A perivascular niche for brain tumor stem cells.</a> Cancer Cell. 11 (1), 69-82 (2007).</li><li>Beck, 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=A+vascular+niche+and+a+VEGF-Nrp1+loop+regulate+the+initiation+and+stemness+of+skin+tumours.">A vascular niche and a VEGF-Nrp1 loop regulate the initiation and stemness of skin tumours.</a> Nature. 478 (7369), 399-403 (2011).</li><li>Aird, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+cell+heterogeneity.">Endothelial cell heterogeneity.</a> Cold Spring Harb. Perspect. 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W. <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+endothelial+cells+from+fresh+tissues.">Isolation of endothelial cells from fresh tissues.</a> Nat. Protoc. 3 (6), 1085-1091 (2008).</li><li>Xiao, L., Harrell, J. C., Perou, C. M., Dudley, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+stable+molecular+signature+in+mammary+tumor+endothelial+cells+that+persists+in+vitro.">Identification of a stable molecular signature in mammary tumor endothelial cells that persists in vitro.</a> Angiogenesis. 17 (3), 511-518 (2014).</li><li>Beijnum, J. 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The authors have nothing to disclose.

Due to the difficulties in obtaining pure primary TEC cultures, many in vitro studies substitute TEC with commercially available EC lines or primary EC such as human umbilical vein EC (HUVEC) 13. However, these EC populations from normal tissues may only serve as a proxy for TEC which differ markedly from their normal counterparts. For example, TEC are phenotypically and functionally abnormal in vivo and some of these abnormalities may be transmittable in vitro 14-18. TEC ...

Endothelial cells (EC) are essential during the development of solid tumors. From initiation of the angiogenic switch in dormant tumors to dissemination and seeding of metastases at distant sites, EC form the conduits that provide blood, oxygen, and nutrients to sustain tumor growth 1. As recently suggested, EC also have perfusion-independent functions and form a niche that supports the growth of cancer stem cells and other tumor stromal cells 2-5. Thus, highly purified tumor-specific EC (TEC) for in vitro culture allows for routine functional studies that will shed light on novel molecular mechanisms mediating tumor angiogenesis and cross talk with tumor cells.
EC are highly specialized depending on the tissue of origin 6. Due to the heterogeneous nature of different tumor types and the tumor microenvironment, TEC may also display unique features that reflect a tumor-specific specialization of the vasculature. For example, there is striking variability in the gene expression signatures in TEC isolated from different types or grades of tumors 7,8. However, frequent co-purification of non-EC, especially tumor-associated fibroblasts and tumor cells, with TEC can confound genome-wide expression analyses. These unwanted cell types are especially problematic in studies that rely on long-term in vitro expansion of TEC cultures.
Described here is a high-fidelity method that consistently produces pure EC cultures from tumors and other tissues. Following immunomagnetic column enrichment of EC fractions and removal of co-purified non-EC, an additional cloning-ring step to capture pure EC colonies is used 9. Each colony can be expanded in culture for multiple passages without the emergence of contaminating non-EC. This method also yields multiple EC clones from a single isolation procedure, which is ideal for the study of endothelial heterogeneity. In addition, it is shown that Cdh5cre:ZsGreenl/s/l reporter mice are a valuable tool for generating &#8220;fate-mapped&#8221; and indelibly-marked EC which maintain ZsGreen fluorescence in culture 10. With minor adjustments to the protocol, this method should be adaptable to different tumor types or normal tissues.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Antibiotic-Antimycotic&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>A5955</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle&#39;s medium (1 g/L D-glucose) (LG-DMEM)</td>
			<td>Gibco</td>
			<td>11885-084</td>
			<td></td>
		</tr>
		<tr>
			<td>EGM-2 Bullet Kit&#160;</td>
			<td>Lonza</td>
			<td>CC4176</td>
			<td>Not all components used</td>
		</tr>
		<tr>
			<td>Fetal bovine serum (Hyclone)</td>
			<td>Thermo Scientific</td>
			<td>SH30071.03</td>
			<td>Heat inactivated at 56&#176;C for 30 min</td>
		</tr>
		<tr>
			<td>Nu-Serum IV</td>
			<td>Corning</td>
			<td>CB-51004</td>
			<td></td>
		</tr>
		<tr>
			<td>Hank&#39;s Balanced Salt Solution (HBBS)</td>
			<td>Gibco</td>
			<td>14175-095</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-buffered saline (PBS)</td>
			<td>Gibco</td>
			<td>14190-144</td>
			<td></td>
		</tr>
		<tr>
			<td>FACS buffer&#160;</td>
			<td>-</td>
			<td>-</td>
			<td>0.5 % BSA and 2 mM EDTA in PBS, filtered through a 0.22 &#956;m filter</td>
		</tr>
		<tr>
			<td>75% v/v ethanol for disinfection</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-PE microbeads&#160;</td>
			<td>Miltenyi Biotech</td>
			<td>130-048-801</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA) fraction V, 7.5%</td>
			<td>Gibco</td>
			<td>15260-37</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell freezing media (Bambanker)</td>
			<td>Wako Chemicals</td>
			<td>302-14681</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase type II&#160;&#160;</td>
			<td>Worthington Biochemical</td>
			<td>LS004176</td>
			<td>Make stock concentration 2 mg/ml in HBSS</td>
		</tr>
		<tr>
			<td>Deoxyribonuclease I (DNase)</td>
			<td>Worthington Biochemical</td>
			<td>LS002004</td>
			<td>Make stock concentration 1 mg/mL in PBS</td>
		</tr>
		<tr>
			<td>Dil-Ac-LDL</td>
			<td>Biomedical Technologies</td>
			<td>BT-902</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA, 0.5M, pH 8.0</td>
			<td>Cellgro</td>
			<td>46-034-CL</td>
			<td></td>
		</tr>
		<tr>
			<td>Enzymatic cell detachment solution (Accutase)</td>
			<td>Sigma-Aldrich</td>
			<td>A6964-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Gelatin, 2 % in water, tissue culture grade</td>
			<td>Sigma-Aldrich</td>
			<td>G1393-100ML</td>
			<td>Dilute in PBS to make 0.5 % gelatin solution</td>
		</tr>
		<tr>
			<td>Mouse FcR Blocking Reagent&#160;</td>
			<td>Miltenyi Biotech</td>
			<td>130-092-575</td>
			<td></td>
		</tr>
		<tr>
			<td>Neutral protease (Dispase)</td>
			<td>Worthington Biochemical</td>
			<td>LS02104</td>
			<td>Make stock concentration 2.5 U/mL in HBSS</td>
		</tr>
		<tr>
			<td>PE-rat anti-mouse CD31 antibody</td>
			<td>BD Pharmingen</td>
			<td>553373</td>
			<td></td>
		</tr>
		<tr>
			<td>RBC lysis buffer (BD Pharm Lyse)</td>
			<td>BD Pharmingen</td>
			<td>555899</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile water</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan blue, 0.4 %&#160;</td>
			<td>Life Technologies</td>
			<td>15250-061</td>
			<td></td>
		</tr>
		<tr>
			<td>10 mm tissue culture dishes</td>
			<td>Corning</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL conical tubes (sterile)</td>
			<td>Corning</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL conical tubes (sterile)&#160;</td>
			<td>Corning</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well tissue culture plates</td>
			<td>Corning</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue-dissociator tubes (gentleMACS) C tubes)&#160;</td>
			<td>Miltenyi Biotech</td>
			<td>130-093-237</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Separator&#160; (MidiMACS)</td>
			<td>Miltenyi Biotech</td>
			<td>130-042-302</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell strainer 100 &#956;m&#160;</td>
			<td>Corning</td>
			<td>352360</td>
			<td></td>
		</tr>
		<tr>
			<td>Cloning rings (assorted sizes)</td>
			<td>Bel-Art Products</td>
			<td>378470000</td>
			<td></td>
		</tr>
		<tr>
			<td>Cryotubes</td>
			<td>Thermo Scientific</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting board</td>
			<td>-</td>
			<td>-</td>
			<td>Sterilize or disinfect with 75% v/v ethanol before use&#160;</td>
		</tr>
		<tr>
			<td>Dissecting forceps and scissors</td>
			<td>-</td>
			<td>-</td>
			<td>Sterilize before use&#160;</td>
		</tr>
		<tr>
			<td>Dissecting pins 2&#34;</td>
			<td>-</td>
			<td>-</td>
			<td>Sterilize before use&#160;</td>
		</tr>
		<tr>
			<td>FACS tubes with 35 &#956;m filter cap</td>
			<td>Corning</td>
			<td>352235</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter cup (Stericup, 0.22 &#956;m)</td>
			<td>Millipore</td>
			<td>SCGPU05RE</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine-tip marker</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Hemocytometer</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>LS Columns</td>
			<td>Miltenyi Biotech</td>
			<td>130-042-401</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic Multistand</td>
			<td>Miltenyi Biotech</td>
			<td>130-042-303</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue adhesive (Vetbond)</td>
			<td>3M</td>
			<td>1469SB</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Eppendorf</td>
			<td>5810R</td>
			<td>Or a centrifuge with similar capacity for 15 mL and 50 mL conical tube centrifugation</td>
		</tr>
		<tr>
			<td>Tissue culture hood</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue dissociator (gentleMACS)</td>
			<td>Miltenyi Biotech</td>
			<td>130-093-235</td>
			<td>Preset program &#34;m_impTumor_01&#34; used for tissue dissociation&#160;</td>
		</tr>
		<tr>
			<td>Liquid nitrogen freezer</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate or rotary shaker</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Phase contrast light microscope</td>
			<td>-</td>
			<td>-</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation and culture expansion of tumor-specific endothelial cells

Freshly isolated tumor-specific endothelial cells (TEC) can be used to explore molecular mechanisms of tumor angiogenesis and serve as an in vitro model for developing new angiogenesis inhibitors for cancer. However, long-term in vitro expansion of murine endothelial cells (EC) is challenging due to phenotypic drift in culture (endothelial-to-mesenchymal transition) and contamination with non-EC. This is especially true for TEC which are readily outcompeted by co-purified fibroblasts or tumor cells in culture. Here, a high fidelity isolation method that takes advantage of immunomagnetic enrichment coupled with colony selection and in vitro expansion is described. This approach generates pure EC fractions that are entirely free of contaminating stromal or tumor cells. It is also shown that lineage-traced Cdh5cre:ZsGreenl/s/l reporter mice, used with the protocol described herein, are a valuable tool to verify cell purity as the isolated EC colonies from these mice show durable and brilliant ZsGreen fluorescence in culture.

EC represent only minor a fraction of the total cell population in most adult tissues 11. It is therefore important to fully digest the harvested tissue into a single-cell suspension that ensures the maximal release of EC from extracellular matrix (ECM) and connective tissues. In our experience, CD31-mediated immunomagnetic selection only provides enriched but not pure EC fractions; therefore, another crucial step is the physical removal of co-purified non-EC and selection/expansion of EC colonies using clonin...

Watch this Scientific Journal Video about Isolation and Culture Expansion of Tumor-specific Endothelial Cells at JoVE.com

Isolation and Culture Expansion of Tumor-specific Endothelial Cells

We report a reliable method to isolate and culture primary tumor-specific endothelial cells from genetically engineered mouse models.

Freshly isolated tumor-specific endothelial cells (TEC) can be used to explore molecular mechanisms of tumor angiogenesis and serve as an in vitro model ...

isolation-and-culture-expansion-of-tumor-specific-endothelial-cells

Research

JoVE Journal

Medicine

11.1K Views.  University of North Carolina at Chapel Hill. We report a reliable method to isolate and culture primary tumor-specific endothelial cells from genetically engineered mouse models. 