Name: isolation of endothelial cells from the lumen of mouse carotid arteries for single-cell multi-omics experiments
Uploaded: 2021-10-04T15:00:00
Description: Watch this Scientific Journal Video about Isolation of Endothelial Cells from the Lumen of Mouse Carotid Arteries for Single-Cell Multi-Omics Experiments at JoVE.com

This work was supported by funding from National Institutes of Health grants HL119798, HL095070, and HL139757 to HJ. HJ is also supported by the Wallace H. Coulter Distinguished Faculty Chair Professorship. The services provided by the Emory Integrated Genomics Core (EIGC) were subsidized by the Emory University School of Medicine and were also partly supported by the Georgia Clinical and Translational Science Alliance of the National Institutes of Health under award no. UL1TR002378. The content provided above is solely the authors&#39; responsibility and does not reflect the official views of the National Institutes of Health.

All animal procedures described below were approved by the Institutional Animal Care and Use Committee at Emory University. Non-hypercholesterolemic, age- and sex-matched C57BL/6 mice were used to mitigate sex-dependent variation and offset any complication of hypercholesterolemic conditions.
1. Partial carotid ligation (PCL) surgery
NOTE: Partial carotid artery ligation of LCA was carried out as previously described and demonstrated3.
<ol>...

<ol>
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W., Rezvan, A., Jo, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accelerated+atherosclerosis+development+in+C57Bl6+mice+by+overexpressing+AAV-mediated+PCSK9+and+partial+carotid+ligation.">Accelerated atherosclerosis development in C57Bl6 mice by overexpressing AAV-mediated PCSK9 and partial carotid ligation.</a> Laboratory Investigation. 97 (8), 935-945 (2017).</li><li>Nam, D., 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=Partial+carotid+ligation+is+a+model+of+acutely+induced+disturbed+flow,+leading+to+rapid+endothelial+dysfunction+and+atherosclerosis.">Partial carotid ligation is a model of acutely induced disturbed flow, leading to rapid endothelial dysfunction and atherosclerosis.</a> American Journal of Physiology Heart and Circulation Physiology. 297 (4), 1535-1543 (2009).</li><li>Nam, D., 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+model+of+disturbed+flow-induced+atherosclerosis+in+mouse+carotid+artery+by+partial+ligation+and+a+simple+method+of+RNA+isolation+from+carotid+endothelium.">A model of disturbed flow-induced atherosclerosis in mouse carotid artery by partial ligation and a simple method of RNA isolation from carotid endothelium.</a> Journal of Visualized Experiments: JoVE. 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This paper provides a detailed protocol to isolate single-cell preparations from the mouse carotid arteries. The influence of d-flow on the endothelial cells can be accurately studied if the PCL surgery is performed correctly. It is crucial to correctly identify the branches of the common carotid, such as the external carotid, internal carotid, occipital artery, and superior thyroid artery. Validation of flow patterns by ultrasonography further validates the successful onset of d-flow conditions. Althou...

An erratum was issued for:&#160;<a href="https://www.jove.com/t/63128">Isolation of Endothelial Cells from the Lumen of Mouse Carotid Arteries for Single-cell Multi-omics Experiments</a>. The Authors section was&#160;updated.
The Authors section was updated from:
Sandeep Kumar*1 
Aitor Andueza*1 
Juyoung Kim1 
Dong-Won Kang1 
Hanjoong Jo1,2 
1Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 2Division of Cardiology, Georgia Institute of Technology and Emory University 
* These authors contributed equally
to:
Sandeep Kumar*1 
Aitor Andueza*1 
Nicolas Villa-Roel1 
Juyoung Kim1 
Dong-Won Kang1 
Hanjoong Jo1,2 
1Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 2Division of Cardiology, Georgia Institute of Technology and Emory University 
* These authors contributed equally

An erratum was issued for:&#160;<a href="https://www.jove.com/t/63128">Isolation of Endothelial Cells from the Lumen of Mouse Carotid Arteries for Single-cell Multi-omics Experiments</a>. The Authors section was&#160;updated.

Erratum: Isolation of Endothelial Cells from the Lumen of Mouse Carotid Arteries for Single-cell Multi-omics Experiments

This laboratory previously demonstrated that induction of d-flow leads to quick and rugged atherosclerosis development in hyperlipidemic mice1,2. The novel mouse model of d-flow-induced atherosclerosis was possible using partial carotid ligation (PCL) surgery 3. PCL surgery induces low and oscillatory blood flow condition or d-flow in the ligated left carotid artery (LCA). In contrast, the contralateral right carotid artery (RCA) continues to face stable laminar flow (s-flow). Previously, to understand the effect of d-flow on endothelial cells, the carotid arteries were dissected out after partial ligation surgery and flushed with a phenol and guanidine isothiocyanate-based lysing agent (luminal RNA/DNA flushing method)2,4, which provided endothelial-enriched &#34;pooled bulk&#34; RNAs or DNAs. These pooled bulk RNAs or DNAs were then processed for transcriptomic studies or epigenomic DNA methylome studies, respectively4,5,6. These studies helped discover multiple flow-sensitive genes and microRNAs whose roles in endothelial biology and atherosclerosis were extensively investigated4,6,7.
However, despite endothelial enrichment, these bulk RNA/DNA studies could not distinguish the specific role of each cell type in the artery wall in d-flow-induced atherosclerosis. Endothelial-enriched single-cell (sc) isolation and&#160;scRNA and scATAC sequencing studies were performed to overcome this limitation8. For this, C57Bl6 mice were subjected to the PCL surgery to induce d-flow in the LCA while using the s-flow-exposed RCA as control. Two days or two weeks after the PCL surgery, the mice were sacrificed, and the carotids were dissected and cleaned up. The lumen of both LCAs and RCAs were infused with collagenase, and the luminal collagenase digests containing ECs as a significant fraction and other arterial cells were collected. The single-cell suspension (scRNAseq) or single-nuclei suspension (scATACseq) were prepared and barcoded with unique identifiers for each cell or nucleus using a 10x Genomics setup. The RNAs were subjected to cDNA library preparation and sequenced.
The scRNAseq and scATACseq datasets were processed using the Cell Ranger Single-Cell Software and further analyzed by Seurat and Signac R packages9,10. Each cell and nucleus was assigned a cell type from these analyses and clustered into the cell type based on the marker genes and unique gene expression patterns. The results of the scRNAseq and scATACseq demonstrated that these single-cell preparations are enriched with ECs and also contain smooth muscle cells (SMCs), fibroblasts, and immune cells.
Further analysis revealed that the EC population in the luminal digestion is highly divergent and plastic (8 different EC clusters) and responsive to blood flow. Most importantly, these results demonstrated that d-flow reprograms ECs from an athero-protected anti-inflammatory phenotype to pro-atherogenic phenotypes, including pro-inflammatory, endothelial-to-mesenchymal transition, endothelial stem/progenitor cell transition, and most surprisingly, endothelial-to-immune cell-like transition. In addition, scATACseq data reveal novel flow-dependent chromatin accessibility changes and transcription factor binding sites in a genome-wide manner, which form the basis of several new hypotheses. The methodology and protocol for preparing single endothelial cells for single-cell multi-omics studies from the mouse carotid arteries are detailed below.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Chemicals, Peptides, and Recombinant Proteins</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1x PBS (Cell Culture Grade)</td>
			<td>Corning</td>
			<td>21040CMX12</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mL Protein LoBind Microcentrifuge Tubes</td>
			<td>Eppendorf</td>
			<td>022-43-108-1</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL Centrifuge Tube - Foam Rack, Sterile</td>
			<td>Fablab</td>
			<td>FL4022</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL SuperClear Centrifuge Tubes</td>
			<td>Labcon</td>
			<td>3191-335-028</td>
			<td></td>
		</tr>
		<tr>
			<td>6-0 Silk Suture Sterile</td>
			<td>Covidien</td>
			<td>s-1172 c2</td>
			<td></td>
		</tr>
		<tr>
			<td>70 &#181;m Cell Strainer, White, Sterile, Individually Packaged</td>
			<td>Thermo Fisher Scientic</td>
			<td>08-771-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Accutase solution,sterile-filtered</td>
			<td>Sigma-Aldrich</td>
			<td>A6964-100ML</td>
			<td>or equivalent</td>
		</tr>
		<tr>
			<td>ATAC Buffer (Component I of Transposition Mix)</td>
			<td>10x Genomics</td>
			<td>2000122</td>
			<td></td>
		</tr>
		<tr>
			<td>ATAC Enzyme (Component II of Transposition Mix)</td>
			<td>10x Genomics</td>
			<td>2000123/ 2000138</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A7906-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Buprenorphine</td>
			<td>Med-Vet International</td>
			<td>RXBUPRENOR5-V</td>
			<td></td>
		</tr>
		<tr>
			<td>Chromium Controller &#38; Next GEM Accessory Kit</td>
			<td>10X Genomics</td>
			<td>1000204</td>
			<td></td>
		</tr>
		<tr>
			<td>Chromium Next GEM Single Cell 3&#39; Reagent Kits v3.1</td>
			<td>10X Genomics</td>
			<td>1000121</td>
			<td></td>
		</tr>
		<tr>
			<td>Chromium Next GEM Single Cell ATAC Reagent Kits v1.1</td>
			<td>10X Genomics</td>
			<td>1000175</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase II</td>
			<td>MP Biomedicals</td>
			<td>2100502.5</td>
			<td></td>
		</tr>
		<tr>
			<td>Digitonin</td>
			<td>Sigma-Aldrich</td>
			<td>D141-100MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting Forceps</td>
			<td>Roboz Surgical Instruments Co</td>
			<td>RS-5005</td>
			<td></td>
		</tr>
		<tr>
			<td>Dnase1</td>
			<td>New England Biolabs Inc</td>
			<td>M0303S</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge (Benchtop-Model # 5425)</td>
			<td>Eppendorf</td>
			<td>22620444230VR</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum - Premium Select</td>
			<td>R&#38;D systems</td>
			<td>S11550</td>
			<td></td>
		</tr>
		<tr>
			<td>Fixed Angle Rotor</td>
			<td>Eppendorf</td>
			<td>FA-45-24-11-Kit Rotor</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES buffered saline</td>
			<td>Millipore Sigma</td>
			<td>51558</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin syringe (3/10 mL 29 G syringe)</td>
			<td>BD</td>
			<td>305932</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Patterson vet</td>
			<td>789 313 89</td>
			<td></td>
		</tr>
		<tr>
			<td>MACs Smart Strainers (30 &#181;m)</td>
			<td>Miltenyi Biotec</td>
			<td>130-098-458</td>
			<td></td>
		</tr>
		<tr>
			<td>MACS SmartStrainers (100 &#181;m)</td>
			<td>&#160;Miltenyi Biotec</td>
			<td>130-098-463</td>
			<td></td>
		</tr>
		<tr>
			<td>Normal Saline (0.9% sodium chloride)</td>
			<td>Baxter International Inc</td>
			<td>2B1323</td>
			<td></td>
		</tr>
		<tr>
			<td>Nuclei Buffer (20x)</td>
			<td>10x Genomics</td>
			<td>PN 2000153/2000207</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS (10x), pH 7.4</td>
			<td>Thermo Fisher Scientic</td>
			<td>70011-044</td>
			<td></td>
		</tr>
		<tr>
			<td>Small scissors</td>
			<td>Roboz Surgical Instruments Co</td>
			<td>RS-5675</td>
			<td></td>
		</tr>
		<tr>
			<td>Stainless Steel Micro Clip Applying Forceps With Lock</td>
			<td>Roboz Surgical Instruments Co.</td>
			<td>RS-5480</td>
			<td>or similar</td>
		</tr>
		<tr>
			<td>Tissue Mend II</td>
			<td>Webster Veteinanry</td>
			<td>07-856-7946</td>
			<td></td>
		</tr>
		<tr>
			<td>Type II Collagenase</td>
			<td>MP biomedicals</td>
			<td>2100502.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Deposited Data</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>scATACseq FastQ files</td>
			<td>NCBI</td>
			<td>www.ncbi.nlm.nih.gov/bioproject Accession # PRJNA646233</td>
			<td></td>
		</tr>
		<tr>
			<td>scRNAseq FastQ files</td>
			<td>NCBI</td>
			<td>www.ncbi.nlm.nih.gov/bioproject Accession # PRJNA646233</td>
			<td></td>
		</tr>
		<tr>
			<td>Software and Algorithms</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Ranger 3.1.0</td>
			<td>10X Genomics</td>
			<td>https://support.10xgenomics.com/ single-cell-gene-exp</td>
			<td></td>
		</tr>
		<tr>
			<td>Cicero</td>
			<td>Pliner et al., 2018</td>
			<td>https://cole-trapnell-lab.github.io/cicero-release/</td>
			<td></td>
		</tr>
		<tr>
			<td>Ggplot2 v3.2.1</td>
			<td>Hadley Wickham</td>
			<td>https://cran.r-project.org</td>
			<td></td>
		</tr>
		<tr>
			<td>Harmony</td>
			<td>Korsunsky et al., 2019</td>
			<td>https://github.com/immunogenomics/harmony</td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>Schneider et al., 2012</td>
			<td>https://imagej.nih.gov</td>
			<td></td>
		</tr>
		<tr>
			<td>Monocle 2.8.0</td>
			<td>Qiu et al., 2017</td>
			<td>https://github.com/cole-trapnell-lab/ monocle-release</td>
			<td></td>
		</tr>
		<tr>
			<td>R version 3.6.2</td>
			<td>R Foundation</td>
			<td>https://www.r-project.org</td>
			<td></td>
		</tr>
		<tr>
			<td>Seurat 3.1.3</td>
			<td>Stuart et al., 2019</td>
			<td>https://github.com/satijalab/seurat</td>
			<td></td>
		</tr>
		<tr>
			<td>Signac 0.2.5</td>
			<td>Stuart et al., 2019</td>
			<td>https://github.com/timoast/signac</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation of endothelial cells from the lumen of mouse carotid arteries for single-cell multi-omics experiments

Atherosclerosis is an inflammatory disease of the arterial regions exposed to disturbed blood flow (d-flow). D-flow regulates the expression of genes in the endothelium at the transcriptomic and epigenomic levels, resulting in proatherogenic responses. Recently, single-cell RNA sequencing (scRNAseq) and single-cell Assay for Transposase Accessible Chromatin sequencing (scATACseq) studies were performed to determine the transcriptomic and chromatin accessibility changes at a single-cell resolution using the mouse partial carotid ligation (PCL) model. As endothelial cells (ECs) represent a minor fraction of the total cell populations in the artery wall, a luminal digestion method was used to obtain EC-enriched single-cell preparations. For this study, mice were subjected to PCL surgery to induce d-flow in the left carotid artery (LCA) while using the right carotid artery (RCA) as a control. The carotid arteries were dissected out two days or two weeks post PCL surgery. The lumen of each carotid was subjected to collagenase digestion, and endothelial-enriched single cells or single nuclei were obtained. These single-cell and single-nuclei preparations were subsequently barcoded using a 10x Genomics microfluidic setup. The barcoded single-cells and single-nuclei were then utilized for RNA preparation, library generation, and sequencing on a high-throughput DNA sequencer. Post bioinformatics processing, the scRNAseq and scATACseq datasets identified various cell types from the luminal digestion, primarily consisting of ECs. Smooth muscle cells, fibroblasts, and immune cells were also present. This EC-enrichment method aided in understanding the effect of blood flow on the endothelium, which could have been difficult with the total artery digestion method. The EC-enriched single-cell preparation method can be used to perform single-cell omics studies in EC-knockouts and transgenic mice where the effect of blood flow on these genes has not been studied. Importantly, this technique can be adapted to isolate EC-enriched single cells from human artery explants to perform similar mechanistic studies.

Partial carotid ligation surgeries were performed on 44 mice, and the onset of d-flow in the LCA was validated by performing ultrasonography one day post partial ligation surgery. Successful partial ligation surgery causes reduced blood flow velocity and reverses blood flow (disturbed flow) in the LCA3. The carotid arteries were dissected out either at two days or at two weeks post ligation. The lumen of each carotid was subjected to collagenase digestion, and endothelial-enriched single-...

Watch this Scientific Journal Video about Isolation of Endothelial Cells from the Lumen of Mouse Carotid Arteries for Single-Cell Multi-Omics Experiments at JoVE.com

Isolation of Endothelial Cells from the Lumen of Mouse Carotid Arteries for Single-Cell Multi-Omics Experiments

We present a method for isolating endothelial cells and nuclei from the lumen of mouse carotid arteries exposed to stable or disturbed flow conditions to perform single-cell omics experiments.

Atherosclerosis is an inflammatory disease of the arterial regions exposed to disturbed blood flow (d-flow). D-flow regulates the expression of genes in ...

In a blood vessel, the number of endothelial cells is very low, which makes it difficult to study them. Our protocol eliminates this limitation, and allows us to study novel molecular pathways and therapeutics. Our protocol allows us to obtain endothelial enriched samples, and study how acute and chronic disturbed flow affects this cell type.The ability to study endothelial cells in more detail makes it possible to define target genes, and therefore potential therapeutics for atherosclerosis targeting endothelial cells. Carotid artery isolation is tricky, and requires patience and experience. To begin, prepare the animal by injecting 0.05 milligrams per kilogram of buprenorphine subcutaneously.Sterilize the epilated area using Betadine and isopropanol solution three times. Make a ventral midline incision of approximately one centimeter in the neck region. Then expose the LCA branch point by blunt dissection.Ligate the left internal carotid, external carotid, and occipital arteries with 6-0 sutures, leaving the superior thyroid artery untouched. Close the incision with tissue glue or sutures. Transfer the mouse to a pre-warmed recovery cage kept at 37 degrees Celsius.Place the mouse on a clean towel for up to one hour to avoid post-surgery hypothermia. Insert a 21 gauge needle into the IV line connected through the apex of the heart into the left ventricle. Allow retrograde perfusion for two to three minutes using normal saline at room temperature.Maintain a constant flow rate by applying steady pressure while injecting or using an IV line, and keeping the saline bag at a height of eight to nine feet. Remove the skin from the neck region with all the fat, muscles, and connective tissues to expose the carotid arteries. Then remove the periadventitial tissues around the carotids leaving the carotid attached to the body.Make an incision below the ligation site in the LCA to allow perfusion. Perfuse the LCA through the left ventricle for another minute to remove any blood traces. Wash the exterior of the carotid arteries with normal saline solution to remove any traces of blood.Use an insulin syringe with a 29 gauge needle to inject 50 microliters of digestion buffer into the lumen of the distal end of the left carotid artery. Use a micro clip to clamp the proximal end of the carotid artery filled with digestion buffer. Add 15 to 20 microliters of digestion buffer into the lumen, and clip the distal end to avoid any release of digestion buffer.Transfer the carotid arteries from the mouse into 35 millimeter dishes containing warm 37 degree Celsius HEPES Buffered Saline Solution. And incubate them for 45 minutes at 37 degrees Celsius with intermittent rocking. Remove the carotid artery with the clamps from the 35 millimeter dish after the luminal enzymatic digestion is completed.Detach the clamps carefully, so that the digestion buffer does not leak. Hold one end of the carotid artery on top of a 1.5 milliliter micro centrifuge tube. Add 100 microliters of warm digestion buffer to the lumen by inserting a 29 gauge needle equipped with an insulin syringe.Quickly flush the lumen of the carotid artery in the micro centrifuge tube, then add 0.3 microliters of FBS into the tube to stop the reaction. Place the micro centrifuge tube on ice. Centrifuge the cells at 500 G for five minutes at four degrees Celsius, using a centrifuge equipped with a fixed angle rotor and discard the supernatant.Re-suspend the cells in digestion buffer, containing cell dissociation reagent, and incubate them for five minutes at 37 degrees Celsius to separate them into single cells. Block the enzymatic reaction by adding 0.15 milliliter of FBS to the 0.5 milliliter tube, and repeat the centrifugation. Discard the supernatant, and resuspend the cells in 100 microliters of ice cold 1%BSA solution in PBS in a 0.2 milliliter micro centrifuge tube.For single cell analysis, resuspend the pellet with 100 microliters of ice cold 1%BSA in PBS in a 0.2 milliliter tube. For single nucleus analysis, resuspend the cell pellet in 100 microliters of 0.04%BSA in ice cold PBS, and centrifuge the single cell suspension at 500G at four degrees Celsius for five minutes. Decompose the single cell suspension with ice cold lysis buffer, and incubate for five minutes on ice.Mix the lysate with a P20 pipette, and incubate for another 10 minutes. Afterward, transfer the lysate in a 0.5 milliliter tube. Wash the ly cells with 500 microliters of buffer, and mix them using a pipette.Then repeat the centrifugation. Discard the supernatant, and resuspend the nuclei pellet in 150 microliters of the diluted nuclei buffer. Count the single nuclei preparations using a hemocytometer.Following the single nuclei sequencing study, single cell and single nuclei were obtained and visualized by bright-field, and phase contrast microscopy. The efficiency of single nuclei preparation from the single cell suspension was also demonstrated. After the single cell RNA sequencing study, various parameters such as distribution of genes per cell, unique molecular identifier per cell, mitochondrial reads per cell, and sequencing saturation data were obtained.For the single cell ATAC sequence study, the insert size distribution, including the nucleosome banding pattern was observed. The normalized TSS enrichment score was also observed. In addition, the percent fragment reads in the peaks.Peak region fragments, TSS enrichment score, ratio of reads in the blacklist genomic sites, and nucleosome signal ratio were determined. The enzymatic digestion is a stress for the cells, therefore it is crucial to maintain the samples on ice, and perform the procedure as quickly as possible. We can use this method to obtain and plate endothelial cells from mice.We can also use this technique to perform bulk Omix based studies. This technique paved way for studying the effect of disturbed blood flow on endothelial cells in vivo in a single cell manner.

Research

JoVE Journal

Biology

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