Name: gene expression analysis of endothelial cells exposed to shear stress using multiple parallel-plate flow chambers
Uploaded: 2018-10-21T14:00:00
Description: Watch this Scientific Journal Video about Gene Expression Analysis of Endothelial Cells Exposed to Shear Stress Using Multiple Parallel-plate Flow Chambers at JoVE.com

This work was supported by CIHR MOP 142307 to P.A.M. H.S.J.M. is a recipient of a Canadian Institutes of Health Research Training Program in Regenerative Medicine Fellowship. H.S.J.M., A.N.S., K.H.K., and M.K.D. are recipients of the Queen Elizabeth II Graduate Scholarships in the Science and Technology.

1. Preparation of Exogenous Reference RNA
NOTE: Choose an exogenous reference RNA that does not exist in the species or model of interest. For mammalian systems, firefly luciferase RNA may be used.
<ol>
	<li>Linearization of exogenous reference RNA plasmid
	<ol>
		<li>Prepare exogenous reference RNA at least 48 h prior to the anticipated RNA extraction. Obtain or manufacture a cDNA clone of the chosen exogenous reference RNA, such as a firefly luciferase cDNA clone in a plas...

<ol>
	<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 Harbor Perspectives in Medicine. 2 (1), (2012).</li><li>Baeyens, N., Bandyopadhyay, C., Coon, B. G., Yun, S., Schwartz, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+fluid+shear+stress+sensing+in+vascular+health+and+disease.">Endothelial fluid shear stress sensing in vascular health and disease.</a> Journal of Clinical Investigation. 126 (3), 821-828 (2016).</li><li>Garcia-Cardena, G., Comander, J., Anderson, K. R., Blackman, B. R., Gimbrone, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomechanical+activation+of+vascular+endothelium+as+a+determinant+of+its+functional+phenotype.">Biomechanical activation of vascular endothelium as a determinant of its functional phenotype.</a> Proceedings of the National Academy of Sciences of the United States of America. 98 (8), 4478-4485 (2001).</li><li>Cybulsky, M. I., Marsden, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+disturbed+blood+flow+on+endothelial+cell+gene+expression:+a+role+for+changes+in+RNA+processing.">Effect of disturbed blood flow on endothelial cell gene expression: a role for changes in RNA processing.</a> Arteriosclerosis, Thrombosis, and Vascular Biology. 34 (9), 1806-1808 (2014).</li><li>Man, H. S. 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=Angiogenic+patterning+by+STEEL,+an+endothelial-enriched+long+noncoding+RNA.">Angiogenic patterning by STEEL, an endothelial-enriched long noncoding RNA.</a> Proceedings of the National Academy of Sciences of the United States of America. 115 (10), 2401-2406 (2018).</li><li>Won, 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=Relative+reduction+of+endothelial+nitric-oxide+synthase+expression+and+transcription+in+atherosclerosis-prone+regions+of+the+mouse+aorta+and+in+an+in+vitro+model+of+disturbed+flow.">Relative reduction of endothelial nitric-oxide synthase expression and transcription in atherosclerosis-prone regions of the mouse aorta and in an in vitro model of disturbed flow.</a> The American Journal of Pathology. 171 (5), 1691-1704 (2007).</li><li>Baeyens, N., 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=Vascular+remodeling+is+governed+by+a+VEGFR3-dependent+fluid+shear+stress+set+point.">Vascular remodeling is governed by a VEGFR3-dependent fluid shear stress set point.</a> eLIFE. 4, 04645 (2015).</li><li>Davies, P. F., Civelek, M., Fang, Y., Fleming, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+atherosusceptible+endothelium:+endothelial+phenotypes+in+complex+haemodynamic+shear+stress+regions+in+vivo.">The atherosusceptible endothelium: endothelial phenotypes in complex haemodynamic shear stress regions in vivo.</a> Cardiovascular Research. 99 (2), 315-327 (2013).</li><li>Lane, W. O., 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=Parallel-plate+flow+chamber+and+continuous+flow+circuit+to+evaluate+endothelial+progenitor+cells+under+laminar+flow+shear+stress.">Parallel-plate flow chamber and continuous flow circuit to evaluate endothelial progenitor cells under laminar flow shear stress.</a> Journal of Visualized Experiments. (59), 3349 (2012).</li><li>Gray, K. M., Stroka, K. M. <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+cell+mechanosensing:+New+insights+gained+from+biomimetic+microfluidic+models.">Vascular endothelial cell mechanosensing: New insights gained from biomimetic microfluidic models.</a> Seminars in Cell and Developmental Biology. 71, 106-117 (2017).</li><li>Bussolari, S. R., Dewey, C. F., Gimbrone, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apparatus+for+subjecting+living+cells+to+fluid+shear+stress.">Apparatus for subjecting living cells to fluid shear stress.</a> Review of Scientific Instruments. 53 (12), 1851-1854 (1982).</li><li>Resnick, N., Gimbrone, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hemodynamic+forces+are+complex+regulators+of+endothelial+gene+expression.">Hemodynamic forces are complex regulators of endothelial gene expression.</a> The FASEB Journal. 9 (10), 874-882 (1995).</li><li>Malek, A. M., Alper, S. L., Izumo, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hemodynamic+shear+stress+and+its+role+in+atherosclerosis.">Hemodynamic shear stress and its role in atherosclerosis.</a> The Journal of the American Medical Association. 282 (21), 2035-2042 (1999).</li><li>DeStefano, J. G., Xu, Z. S., Williams, A. J., Yimam, N., Searson, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+shear+stress+on+iPSC-derived+human+brain+microvascular+endothelial+cells+(dhBMECs).">Effect of shear stress on iPSC-derived human brain microvascular endothelial cells (dhBMECs).</a> Fluids and Barriers of the CNS. 14 (1), 20 (2017).</li><li>Thormar, H. G., 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=Importance+of+the+efficiency+of+double-stranded+DNA+formation+in+cDNA+synthesis+for+the+imprecision+of+microarray+expression+analysis.">Importance of the efficiency of double-stranded DNA formation in cDNA synthesis for the imprecision of microarray expression analysis.</a> Clinical Chemistry. 59 (4), 667-674 (2013).</li><li>Johnston, S., Gallaher, Z., Czaja, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exogenous+reference+gene+normalization+for+real-time+reverse+transcription-polymerase+chain+reaction+analysis+under+dynamic+endogenous+transcription.">Exogenous reference gene normalization for real-time reverse transcription-polymerase chain reaction analysis under dynamic endogenous transcription.</a> Neural Regenation Research. 7 (14), 1064-1072 (2012).</li><li>Vaughan-Shaw, P. G., 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+simple+method+to+overcome+the+inhibitory+effect+of+heparin+on+DNA+amplification.">A simple method to overcome the inhibitory effect of heparin on DNA amplification.</a> Cellular Oncology (Dordrecht). 38 (6), 493-495 (2015).</li><li>Collins, 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=Haemodynamic+and+extracellular+matrix+cues+regulate+the+mechanical+phenotype+and+stiffness+of+aortic+endothelial+cells.">Haemodynamic and extracellular matrix cues regulate the mechanical phenotype and stiffness of aortic endothelial cells.</a> Nature Communications. 5, 3984 (2014).</li><li>Fichtlscherer, 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=Circulating+microRNAs+in+patients+with+coronary+artery+disease.">Circulating microRNAs in patients with coronary artery disease.</a> Circulation Research. 107 (5), 677-684 (2010).</li><li>Smith, R. D., Brown, B., Ikonomi, P., Schechter, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exogenous+reference+RNA+for+normalization+of+real-time+quantitative+PCR.">Exogenous reference RNA for normalization of real-time quantitative PCR.</a> Biotechniques. 34 (1), 88-91 (2003).</li><li>Kohn, J. 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=Cooperative+effects+of+matrix+stiffness+and+fluid+shear+stress+on+endothelial+cell+behavior.">Cooperative effects of matrix stiffness and fluid shear stress on endothelial cell behavior.</a> Biophysical Journal. 108 (3), 471-478 (2015).</li></ol>

Shear stress is a physiologic condition that modulates endothelial function, in part, by affecting steady-state gene expression2,5. Models of gene regulation in various shear stress conditions will contribute to a greater understanding of endothelial function. This pragmatic workflow includes a flow circuit using a parallel-plate flow chamber adapted from Lane et al.9 and represents laminar, non-pulsatile flow. The overall set-up ...

Vascular endothelial cells form the inner cellular lining of blood vessels in the closed cardiovascular system of higher species. They form the interface between the blood and tissues and are characterized by luminal and abluminal surfaces. The endothelium is a diverse, active, and adaptive system that regulates blood flow, nutrient trafficking, immunity, and the growth of new blood vessels1. In the body, endothelial cells normally exist in an environment where they are exposed to the frictional force of circulation, shear stress2. Shear stress is an important regulator of endothelial cell gene expression3, and endothelial cells attempt to maintain shear stress within a given range2,4. Endothelial cells demonstrate angiogenic patterning in the absence of shear stress5 that can improve tissue perfusion. Regional patterns of disturbed flow and altered shear stress are associated with the expression of inflammatory genes6 and the development of atherosclerosis7,8. Thus, models that include shear stress are a major component of understanding endothelial gene regulation.
We describe a method for studying the gene regulation in vascular endothelial cells under shear stress. This system uses non-pulsatile flow and mimics fluid shear stress levels and oxygen concentration that model conditions for arterial endothelial cells. This protocol includes details of methods for the gene knockdown using RNA interference (RNAi), the set-up for the application of shear stress using the parallel-plate flow apparatus, and methods for the spike-in of an exogenous reference RNA prior to analysis by reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR). This pipeline is used for studying gene regulation in endothelial cells in the presence and absence of laminar shear stress and includes an adaptation of the parallel-plate flow apparatus described by Lane et al.9. This particular set-up was designed to facilitate the simultaneous assessment of multiple experimental conditions that allows direct comparison of shear stress conditions, as well as the normalization of RNA analysis. A large heated unit with controlled humidity is utilized to allow multiple separate flow chambers and pumps to be running simultaneously with flow rates monitored for each flow chamber assembly in real-time. The application of this set-up is used for gene knockdown using RNAi in the setting of laminar flow/shear stress, but aspects of this protocol can be applied to any assessment of RNA expression.
Common approaches to the application of shear stress for endothelial cells include microfluidic systems10, a cone-and-plate viscometer11, and a parallel-plate flow chamber12. Microfluidic systems from various manufacturers have been useful in studying mechanobiology and mechanotransduction in multiple cell and tissue types and a variety of biophysical stimuli. For endothelial cells, they have been used to study endothelial cells in isolation, as well as the interaction of endothelial cells and the trafficking of immune or tumor cells10. However, these systems are less suitable for the recovery of large numbers of cells9. Both the cone-and-plate viscometer and parallel-plate flow chambers allow the recovery of large numbers of cells in confluent monolayers12. These systems can generate a range of shear forces and patterns12. The parallel-plate flow chamber assembly9 has the advantage that real-time imaging can be performed through the glass window to evaluate cellular morphology at any time point. Furthermore, the perfusate can be collected under sterile conditions. For the system presented here, the flow can also be monitored in real-time and in a multi-chamber set-up, which facilitates the maintenance of shear conditions between chambers.
For representative experiments, human umbilical vein endothelial cells (HUVEC), which represent a macrovascular endothelial cell type, are used, and the shear stress conditions we use (1 Pa) reflect arterial conditions (0.1 - 0.7 Pa). However, this protocol can be used with other endothelial cell types, and the shear stress conditions can be adjusted according to the experimental question. For example, the evaluation of human endothelial cells in conditions that model venous circulation would require lower levels of shear stress (1 - 6 Pa) and studies that model microvascular circulation have utilized shear stress levels of 0.4 - 1.2 Pa13,14. In addition, shear stress can vary even between endothelial cells within the same blood vessel6. In the current set-up, a single monitoring system is used that can simultaneously monitor four separate flow loops. For labs that need more flow loops, there is space in the dedicated environment for an additional monitoring system.
RT-qPCR is used for the absolute quantitation of gene expression in the setting of shear stress. The relative expression of target genes is often used to compare RNA expression across conditions. Some RNA species can exist at very low quantities or be absent, thus complicating relative measurements. For example, long noncoding RNAs in endothelial cells can exert potent effects at relatively low copy numbers per cell5. In addition, differences in primer efficiency can lead to an inaccurate interpretation from utilizing the delta-delta cycle threshold (Ct) method to analyze the data. To address this concern, we perform absolute quantitation by generating a standard curve using a known quantity of plasmid DNA. Furthermore, complementary DNA (cDNA) synthesis is an inefficient process, and differences in cDNA efficiency can account for differences in RNA expression between conditions and between samples15. The application of shear stress and/or transfection reagents can affect cell proliferation, apoptosis, and viability, or add components that may interfere with RNA isolation and/or cDNA synthesis. To account for the possibility of bias from RNA isolation and cDNA synthesis, we use a spike-in RNA control synthesized in the lab, added at the time of RNA extraction and measured with each cDNA synthesis via RT-qPCR. This allows not only the adjustment for technical differences in RNA extraction and cDNA synthesis but also allows the calculation of absolute quantities per cell, when the cell count is known.
This system uses additional steps to maintain similarity or account for technical differences between conditions. We particularly emphasize these steps because of the complex nature of these experiments, which involve multiple physical set-ups and experimental conditions that can lead to experimental variability.

<table>
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			<td>0.05% Trypsin-EDTA</td>
			<td>gibco</td>
			<td>25300-062</td>
			<td></td>
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		<tr>
			<td>10 mL Syringe</td>
			<td>BD</td>
			<td>302995</td>
			<td></td>
		</tr>
		<tr>
			<td>10 mm2 Culture Dish</td>
			<td>Sarstedt</td>
			<td>83.3902</td>
			<td></td>
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		<tr>
			<td>30 mL Syringe</td>
			<td>BD</td>
			<td>302832</td>
			<td></td>
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		<tr>
			<td>4-Way Stopcocks</td>
			<td>Discofix</td>
			<td>D500</td>
			<td></td>
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			<td>Aluminum foil</td>
			<td></td>
			<td></td>
			<td></td>
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		<tr>
			<td>BEACH</td>
			<td>Darwin Chambers Company</td>
			<td>MN: HO85, SN: 4947549</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Scrapers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 Meter</td>
			<td>BioSphenix, Ltd.</td>
			<td>MN: P120, SN: 0342</td>
			<td></td>
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		<tr>
			<td>CO2 Sensor</td>
			<td>BioSphenix, Ltd.</td>
			<td>MN: C700, SN: 52852</td>
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			<td>Distilled water</td>
			<td>gibco</td>
			<td>15230-170</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate-buffered saline (DPBS) -/-</td>
			<td>gibco</td>
			<td>14190-144</td>
			<td></td>
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		<tr>
			<td>Endothelial Cell Growth Medium 2</td>
			<td>Promo Cell</td>
			<td>C-22011</td>
			<td></td>
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		<tr>
			<td>Endothelial Cell Growth Medium 2 Supplement Mix</td>
			<td>Promo Cell</td>
			<td>C-39216</td>
			<td></td>
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			<td>Fibronectin (pure)</td>
			<td>Sigma-Aldrich</td>
			<td>11051407001</td>
			<td></td>
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			<td>Filter (0.20 um)</td>
			<td>Sarstedt</td>
			<td>83.1826.001</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Dampener and Cap</td>
			<td>U of T glass blowing shop</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Meter: 400 Series Console</td>
			<td>Transonic Scisense Inc.</td>
			<td>T402</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Meter: 400 Series Tubing</td>
			<td>Transonic Scisense Inc.</td>
			<td>TS410</td>
			<td></td>
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		<tr>
			<td>Flow Reservoir and Cap</td>
			<td>U of T glass blowing shop</td>
			<td></td>
			<td></td>
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		<tr>
			<td>Flow Sensor</td>
			<td>Transonic Scisense Inc.</td>
			<td>ME4PXL</td>
			<td></td>
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		<tr>
			<td>Isotemp 737F Oven</td>
			<td>Fisher Scientific</td>
			<td>FI-737F</td>
			<td></td>
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			<td>J cloth</td>
			<td>J cloth</td>
			<td></td>
			<td></td>
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		<tr>
			<td>Microscope Slide (25 x 75 x 1 mm)</td>
			<td>Fisherfinest</td>
			<td>12-544-4</td>
			<td></td>
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		<tr>
			<td>Paper sterilization pouch</td>
			<td>Cardinal Health</td>
			<td>92713</td>
			<td></td>
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		<tr>
			<td>Pump (Masterflex L/S Economy Drive)</td>
			<td>Cole-Parmer</td>
			<td>7554-90</td>
			<td></td>
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		<tr>
			<td>Pump Head (Masterflex L/S Easy Load)</td>
			<td>Cole-Parmer</td>
			<td>7518-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Rectangular 4 Well Dish</td>
			<td>Thermo Scientific</td>
			<td>267061</td>
			<td></td>
		</tr>
		<tr>
			<td>Tweezers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Tubing</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Masterflex C-Flex L/S 25 Soft Tubing</td>
			<td>Cole-Parmer</td>
			<td>06424-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Masterflex C-Flex L/S 14 Soft Tubing</td>
			<td>Cole-Parmer</td>
			<td>06424-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Masterflex C-Flex L/S 16 Soft Tubing</td>
			<td>Cole-Parmer</td>
			<td>06424-16</td>
			<td></td>
		</tr>
		<tr>
			<td>Masterflex PharMed BPT L/S 13 Hard Tubing</td>
			<td>Cole-Parmer</td>
			<td>06508-13</td>
			<td></td>
		</tr>
		<tr>
			<td>Masterflex PharMed BPT L/S 14 Hard Tubing</td>
			<td>Cole-Parmer</td>
			<td>06508-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Luer </td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3/16&#34; Male Luer</td>
			<td>Cole-Parmer</td>
			<td>45518-08</td>
			<td>For #25 tubing</td>
		</tr>
		<tr>
			<td>1/8&#34; Male Luer</td>
			<td>Cole-Parmer</td>
			<td>30800-24</td>
			<td>For #16 tubing</td>
		</tr>
		<tr>
			<td>1/8&#34; Female Luer</td>
			<td>Cole-Parmer</td>
			<td>30800-08</td>
			<td>For #16 tubing</td>
		</tr>
		<tr>
			<td>1/16&#34; Male Luer</td>
			<td>Cole-Parmer</td>
			<td>45518-00</td>
			<td>For #14 tubing</td>
		</tr>
		<tr>
			<td>1/16&#34; Female Luer</td>
			<td>Cole-Parmer</td>
			<td>45508-00</td>
			<td>For #14 tubing</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Knockdown reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Oligofectamine Reagent</td>
			<td>Invitrogen</td>
			<td>12252-011</td>
			<td></td>
		</tr>
		<tr>
			<td>Opti-MEM I Reduced Serum Medium</td>
			<td>gibco</td>
			<td>31985-070</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>In vitro transcription </td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Generuler 1kb+ DNA ladder</td>
			<td>Thermo Scientific</td>
			<td>SM1331</td>
			<td></td>
		</tr>
		<tr>
			<td>MEGAclear Kit</td>
			<td>Ambion</td>
			<td>AM1908</td>
			<td></td>
		</tr>
		<tr>
			<td>mMESSSEGE mMACHINE SP6 Transcription Kit</td>
			<td>Ambion</td>
			<td>AM1340</td>
			<td></td>
		</tr>
		<tr>
			<td>pSP-luc+</td>
			<td>Promega</td>
			<td>E4471</td>
			<td></td>
		</tr>
		<tr>
			<td>Supercoiled DNA Ladder</td>
			<td>New England BioLabs Inc.</td>
			<td>N0472S</td>
			<td></td>
		</tr>
		<tr>
			<td>UltraPure Agarose</td>
			<td>Invitrogen</td>
			<td>16500-500</td>
			<td></td>
		</tr>
		<tr>
			<td>UltraPure Ethidium Bromide</td>
			<td>Invitrogen</td>
			<td>15585011</td>
			<td></td>
		</tr>
		<tr>
			<td>XhoI Restriction Enzyme</td>
			<td>New England BioLabs Inc.</td>
			<td>R0146S</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>RNA extraction </td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Beta-mercaptoethanol</td>
			<td>Sigma</td>
			<td>M3148-100mL</td>
			<td></td>
		</tr>
		<tr>
			<td>RNeasy Mini Kit</td>
			<td>Qiagen</td>
			<td>74104</td>
			<td></td>
		</tr>
	</tbody>
</table>

gene expression analysis of endothelial cells exposed to shear stress using multiple parallel-plate flow chambers

We describe a workflow for the analysis of gene expression from endothelial cells subject to a steady laminar flow using multiple monitored parallel-plate flow chambers. Endothelial cells form the inner cellular lining of blood vessels and are chronically exposed to the frictional force of blood flow called shear stress. Under physiological conditions, endothelial cells function in the presence of various shear stress conditions. Thus, the application of shear stress conditions in in vitro models can provide greater insight into endothelial responses in vivo. The parallel-plate flow chamber previously published by Lane et al.9 is adapted to study endothelial gene regulation in the presence and absence of steady (non-pulsatile) laminar flow. Key adaptations in the set-up for laminar flow as presented here include a large, dedicated environment to house concurrent flow circuits, the monitoring of flow rates in real-time, and the inclusion of an exogenous reference RNA for the normalization of quantitative real-time PCR data. To assess multiple treatments/conditions with the application of shear stress, multiple flow circuits and pumps are used simultaneously within the same heated and humidified incubator. The flow rate of each flow circuit is measured continuously in real-time to standardize shear stress conditions throughout the experiments. Because these experiments have multiple conditions, we also use an exogenous reference RNA that is spiked-in at the time of RNA extraction for the normalization of RNA extraction and first-strand cDNA synthesis efficiencies. These steps minimize the variability between samples. This strategy is employed in our pipeline for the gene expression analysis with shear stress experiments using the parallel-plate flow chamber, but parts of this strategy, such as the exogenous reference RNA spike-in, can easily and cost-effectively be used for other applications.

Successful linearization of luciferase plasmid using restriction enzymes was confirmed by running digested products on an agarose gel (Figure 1). The size of the linearized product was confirmed using DNA ladders and by comparison with uncut plasmid.
We have adapted the parallel-plate flow chamber set-up from Lane et al.9 for experiments that require multiple conditi...

Watch this Scientific Journal Video about Gene Expression Analysis of Endothelial Cells Exposed to Shear Stress Using Multiple Parallel-plate Flow Chambers at JoVE.com

Gene Expression Analysis of Endothelial Cells Exposed to Shear Stress Using Multiple Parallel-plate Flow Chambers

Here, a workflow for the culture and gene expression analysis of endothelial cells under fluid shear stress is presented. Included is a physical arrangement for simultaneously housing and monitoring multiple flow chambers in a controlled environment and the use of an exogenous reference RNA for quantitative PCR.

We describe a workflow for the analysis of gene expression from endothelial cells subject to a steady laminar flow using multiple monitored parallel-plate ...

This method can help answer key questions in the field of endothelial biology, such as why do blood vessels have regional differences in the development of atherosclerosis? The main advantage of this technique is it allows the simultaneous study of multiple conditions under shear stress or multiple shear stress conditions. The implications of this technique extend toward understanding endothelial gene regulation in both the arterial and venous systems because various flow rates and patterns can be used.Well here, we demonstrate a system that uses steady laminar flow. The setup can be adapted for other flow patterns, including disturbed flow. Generally, individuals new to this method will struggle to maintain a continuous monolayer of cells throughout the duration of the experiment and to obtain consistent results between experiments.24 hours before the analysis, count the human endothelial cells at an early passage and seed approximately one times 10 to the sixth cells in one milliliter of medium onto one fibronectin coated glass slide per well of a four-well cell culture plate. Allow the cells to adhere to the slide for 15 minutes at 37 degrees Celsius. Then cover each slide with three milliliters of medium and place the plate in the cell culture incubator of 37 degrees Celsius and 5%CO2 for 24 hours.On the day of the experiment, fill the water tray of a large, heated, built-in environment with adjustable CO2 and heat, or beach incubator, with multiple shelves, internal electricity access, and glass doors, and confirm that adequate carbon dioxide is available for the experiment, and that the CO2 monitor is functional. To set up the flow chamber, insert a 1/8 inch female lure into one end of a number 16 soft tube, and attach a four-way stopcock to the lure. Attach the free end of the tube to the inflow side of the top plate and insert a 1/8th inch male lure into one end of a second number 16 soft tube.Attach a four-way stopcock to the male lure, and attach the free end of the tube to the outflow side of the top plate. Insert a 1/8th inch male lure and a 1/8th inch female lure into each end of a third number 16 soft tube, and attach the tubing to a bubble trap via the 1/8th inch male lure. Then attach a four-way stopcock to the other end of the tubing via the female lure.Using sterile tweezers, transfer one cell seeded glass slide to the recess on the bottom plate, cell seeded side up. Use a 10 milliliter syringe to add 10 milliliters of warm medium to the bottom plate within the red gasket line around the plate. Allowing medium to flow through the slide and cover the cells.Gently place the top plate onto the bottom plate taking care to align the sides and screw the plates together tightly. To remove air bubbles from the bubble trap, first open the inflow and bubble trap stopcocks and close the outflow stopcock. Then use a 30 milliliter syringe to gently flush 20 milliliters of warm medium through the plate.To remove bubbles from the chamber, close the bubble trap stopcock and open the outflow stopcock. Elevate the outflow side of the chamber to a 45 degree angle and use the 30 milliliter syringe to gently flush 20 milliliters of warm medium from the inflow side of the chamber. It is important to flush at an appropriate rate in the direction of the flow and to use microscope to confirm that a confluent monolayer of cells remains before exposing the cells to the laminar flow.Then close the stopcocks on both sides of the chamber and cap and confirm that the cells are still attached to the slide under a light microscope. Place the flow chamber and a previously assembled flow loop system into the beach and slowly decrease the pump speed of the flow loop assembly before pausing the pump altogether. Close the stopcocks on the flow loop system to prevent leakage and connect the chamber and loop system together via stopcocks.When all of the loops have been connected, reopen all of the stopcocks and slowly increase the pump speed while monitoring the setup for any leakage or blockage. Place the flow sensor on the chamber bridge tubing of the inflow side of the chamber with the sensor oriented in the direction of flow and adjust the pump speed to obtain the flow rate for the shear stress rate of interest. Then turn on the CO2 tank to achieve a 5%C02 concentration.Once the experimental flow period is complete, slowly decrease the peristaltic pump speed to zero and turn off the power. Quickly close all of the open stopcocks and transfer the chamber and the attached tubing with a stopcock on each side to a clean bench top. Carefully unscrew all of the screws to remove the top plate and use needle nose tweezers to transfer the glass slide from the bottom plate to a 100 millimeter diameter dish.Wash the slide in 10 milliliters of cold PBS and check the cells under a microscope to confirm cell adherence and alignment in the direction of flow. After aspirating the PBS, transfer the slide to a clean 100 millimeter diameter dish and add 350 microliters of lysis buffer supplemented with 1/100th of Beta-Mercaptoethanol from an RNA extraction kit to the slide. Use a polyethylene bladed cell scraper to scrape the cells off the slide and tilt the tissue culture dish to allow the buffer to pool at the bottom.Use forceps to remove the slide and pipette the cell lysate into a 1.5 milliliter tube on ice. Then add 10 microliters of diluted luciferase RNA to the cell lysate for downstream RNA isolation and analysis according to standard protocols. A successful linearization of the luciferase plasmid using restriction enzymes can be confirmed by running the digested products on an agarose gel and the size of the linearized product can be confirmed with DNA ladders and by comparison with an uncut plasmid.Manufacturing processes can lead to small variations in the chamber height, thus the flow rate must be calculated for each chamber to achieve the same shear stress. For experiments incorporating laminar shear stress in mammalian endothelial cells, firefly luciferase RNA can be used as an exogenous RNA spike-in. Normalization of the endogenous reference gene, the exogenous reference gene, and both endogenous and exogenous reference genes together yields similar results.Of note, in these representative experiments using two simultaneously running flow chambers with shear stress at one Pascal for each experiment, Kruppel like factor two knockdown via SI-RNA yielded a similar knockdown efficiency between the tested biological samples. While attempting this procedure it is important to remember to establish an even monolayer of cells on the slide and to profuse the flow loop system prior to attaching the flow chamber. Following this procedure, other methods, like RNA sequencing, can be used to assess genome wide RNA expression and other readouts, such as DNA and protein, can be used for further molecular analysis.After its development, this technique paved the way for researchers in the field of endothelial biology to explore the relationship between shear stress and angiogenic potential in human endothelial cells.

gene-expression-analysis-endothelial-cells-exposed-to-shear-stress

Research

JoVE Journal

Bioengineering

Parallel-plate Flow Chamber and Continuous Flow Circuit to Evaluate Endothelial Progenitor Cells under Laminar Flow Shear Stress

The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well quantifiable fluid shear stresses1.
Our flow chamber design and flow circuit (Fig. 1) contains a transparent viewing region that enables testing of cell adhesion and imaging of cell morphology immediately before flow (Fig. 11A, B), at various time points during flow (Fig. 11C), and after flow (Fig. 11D). These experiments are illustrated with human umbilical cord blood-derived endothelial progenitor cells (EPCs) and porcine EPCs2,3.
This method is also applicable to other adherent cell types, e.g. smooth muscle cells (SMCs) or fibroblasts.
The chamber and all parts of the circuit are easily sterilized with steam autoclaving. In contrast to other chambers, e.g. microfluidic chambers, large numbers of cells (&gt; 1 million depending on cell size) can be recovered after the flow experiment under sterile conditions for cell culture or other experiments, e.g. DNA or RNA extraction, or immunohistochemistry (Fig. 11E), or scanning electron microscopy5. The shear stress can be adjusted by varying the flow rate of the perfusate, the fluid viscosity, or the channel height and width. The latter can reduce fluid volume or cell needs while ensuring that one-dimensional flow is maintained. It is not necessary to measure chamber height between experiments, since the chamber height does not depend on the use of gaskets, which greatly increases the ease of multiple experiments. Furthermore, the circuit design easily enables the collection of perfusate samples for analysis and/or quantification of metabolites secreted by cells under fluid shear stress exposure, e.g. nitric oxide (Fig. 12)6.

We are describing a method to subject adherent cells to laminar flow shear stress in a sterile continuous flow circuit. The cells' adhesion, morphology can be studied through the transparent chamber, samples obtained from the circuit for metabolite analysis and cells harvested after shear exposure for future experiments or culture.

The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well ...

Evaluation of Polymeric Gene Delivery Nanoparticles by Nanoparticle Tracking Analysis and High-throughput Flow Cytometry

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a technology for regenerative medicine2. Unlike viruses, which have significant safety issues, polymeric nanoparticles can be designed to be non-toxic, non-immunogenic, non-mutagenic, easier to synthesize, chemically versatile, capable of carrying larger nucleic acid cargo and biodegradable and/or environmentally responsive. Cationic polymers self-assemble with negatively charged DNA via electrostatic interaction to form complexes on the order of 100 nm that are commonly termed polymeric nanoparticles. Examples of biomaterials used to form nanoscale polycationic gene delivery nanoparticles include polylysine, polyphosphoesters, poly(amidoamines)s and polyethylenimine (PEI), which is a non-degradable off-the-shelf cationic polymer commonly used for nucleic acid delivery1,3 . Poly(beta-amino ester)s (PBAEs) are a newer class of cationic polymers4 that are hydrolytically degradable5,6 and have been shown to be effective at gene delivery to hard-to-transfect cell types such as human retinal endothelial cells (HRECs)7, mouse mammary epithelial cells8, human brain cancer cells9 and macrovascular (human umbilical vein, HUVECs) endothelial cells10.
A new protocol to characterize polymeric nanoparticles utilizing nanoparticle tracking analysis (NTA) is described. In this approach, both the particle size distribution and the distribution of the number of plasmids per particle are obtained11. In addition, a high-throughput 96-well plate transfection assay for rapid screening of the transfection efficacy of polymeric nanoparticles is presented. In this protocol, poly(beta-amino ester)s (PBAEs) are used as model polymers and human retinal endothelial cells (HRECs) are used as model human cells. This protocol can be easily adapted to evaluate any polymeric nanoparticle and any cell type of interest in a multi-well plate format.

A protocol for nanoparticle tracking analysis (NTA) and high-throughput flow cytometry to evaluate polymeric gene delivery nanoparticles is described. NTA is utilized to characterize the nanoparticle particle size distribution and the plasmid per particle distribution. High-throughput flow cytometry enables quantitative transfection efficacy evaluation for a library of gene delivery biomaterials.

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a ...

Transplantation of Induced Pluripotent Stem Cell-derived Mesoangioblast-like Myogenic Progenitors in Mouse Models of Muscle Regeneration

Patient-derived iPSCs could be an invaluable source of cells for future autologous cell therapy protocols. iPSC-derived myogenic stem/progenitor cells similar to pericyte-derived mesoangioblasts (iPSC-derived mesoangioblast-like stem/progenitor cells: IDEMs) can be established from iPSCs generated from patients affected by different forms of muscular dystrophy. Patient-specific IDEMs can be genetically corrected with different strategies (e.g. lentiviral vectors, human artificial chromosomes) and enhanced in their myogenic differentiation potential upon overexpression of the myogenesis regulator MyoD. This myogenic potential is then assessed in vitro with specific differentiation assays and analyzed by immunofluorescence. The regenerative potential of IDEMs is further evaluated in vivo, upon intramuscular and intra-arterial transplantation in two representative mouse models displaying acute and chronic muscle regeneration. The contribution of IDEMs to the host skeletal muscle is then confirmed by different functional tests in transplanted mice. In particular, the amelioration of the motor capacity of the animals is studied with treadmill tests. Cell engraftment and differentiation are then assessed by a number of histological and immunofluorescence assays on transplanted muscles. Overall, this paper describes the assays and tools currently utilized to evaluate the differentiation capacity of IDEMs, focusing on the transplantation methods and subsequent outcome measures to analyze the efficacy of cell transplantation.

Induced pluripotent stem cell (iPSC)-derived myogenic progenitors are promising candidates for cell therapy strategies to treat muscular dystrophies. This protocol describes transplantation and functional measurements required to evaluate the engraftment and differentiation of iPSC-derived mesoangioblasts (a type of muscle progenitors) in mouse models of acute and chronic muscle regeneration.

Patient-derived iPSCs could be an invaluable source of cells for future autologous cell therapy protocols. iPSC-derived myogenic stem/progenitor cells ...

Generation of Shear Adhesion Map Using SynVivo Synthetic Microvascular Networks

Cell/particle adhesion assays are critical to understanding the biochemical interactions involved in disease pathophysiology and have important applications in the quest for the development of novel therapeutics. Assays using static conditions fail to capture the dependence of adhesion on shear, limiting their correlation with in vivo environment. Parallel plate flow chambers that quantify adhesion under physiological fluid flow need multiple experiments for the generation of a shear adhesion map. In addition, they do not represent the in vivo scale and morphology and require large volumes (~ml) of reagents for experiments. In this study, we demonstrate the generation of shear adhesion map from a single experiment using a microvascular network based microfluidic device, SynVivo-SMN. This device recreates the complex in vivo vasculature including geometric scale, morphological elements, flow features and cellular interactions in an in vitro format, thereby providing a biologically realistic environment for basic and applied research in cellular behavior, drug delivery, and drug discovery. The assay was demonstrated by studying the interaction of the 2 &#181;m biotin-coated particles with avidin-coated surfaces of the microchip. The entire range of shear observed in the microvasculature is obtained in a single assay enabling adhesion vs. shear map for the particles under physiological conditions.

Flow chambers used in adhesion experiments typically consist of linear flow paths and require multiple experiments at different flow rates to generate a shear adhesion map. SynVivo-SMN enables the generation of shear adhesion map using a single experiment utilizing microliter volumes resulting in significant savings in time and consumables.

Cell/particle adhesion assays are critical to understanding the biochemical interactions involved in disease pathophysiology and have important ...

Multi-step Preparation Technique to Recover Multiple Metabolite Compound Classes for In-depth and Informative Metabolomic Analysis

Metabolomics is an emerging field which enables profiling of samples from living organisms in order to obtain insight into biological processes. A vital aspect of metabolomics is sample preparation whereby inconsistent techniques generate unreliable results. This technique encompasses protein precipitation, liquid-liquid extraction, and solid-phase extraction as a means of fractionating metabolites into four distinct classes.&#160;Improved enrichment of low abundance molecules with a resulting increase in sensitivity is obtained, and ultimately results in more confident identification of molecules. This technique has been applied to plasma, bronchoalveolar lavage fluid, and cerebrospinal fluid samples with volumes as low as 50 &#181;l. &#160;Samples can be used for multiple downstream applications; for example, the pellet resulting from protein precipitation can be stored for later analysis. The supernatant from that step undergoes liquid-liquid extraction using water and strong organic solvent to separate the hydrophilic and hydrophobic compounds. Once fractionated, the hydrophilic layer can be processed for later analysis or discarded if not needed. The hydrophobic fraction is further treated with a series of solvents during three solid-phase extraction steps to separate it into fatty acids, neutral lipids, and phospholipids. This allows the technician the flexibility to choose which class of compounds is preferred for analysis. It also aids in more reliable metabolite identification since some knowledge of chemical class exists.

The reliability of results in metabolomics experiments depends on the effectiveness and reproducibility of the sample preparation. Described is a rigorous and in-depth method that enables extraction of metabolites from biological fluids with the option of subsequently analyzing up to thousands of compounds, or just the compound classes of interest.

Metabolomics is an emerging field which enables profiling of samples from living organisms in order to obtain insight into biological processes. A vital ...

Microfluidic Flow Chambers Using Reconstituted Blood to Model Hemostasis and Platelet Transfusion In Vitro

Blood platelets prepared for transfusion gradually lose hemostatic function during storage. Platelet function can be investigated using a variety of (indirect) in vitro experiments, but none of these is as comprehensive as microfluidic flow chambers. In this protocol, the reconstitution of thrombocytopenic fresh blood with stored blood bank platelets is used to simulate platelet transfusion. Next, the reconstituted sample is perfused in microfluidic flow chambers which mimic hemostasis on exposed subendothelial matrix proteins. Effects of blood donation, transport, component separation, storage and pathogen inactivation can be measured in paired experimental designs. This allows reliable comparison of the impact every manipulation in blood component preparation has on hemostasis. Our results demonstrate the impact of temperature cycling, shear rates, platelet concentration and storage duration on platelet function. In conclusion, this protocol analyzes the function of blood bank platelets and this ultimately aids in optimization of the processing chain including phlebotomy, transport, component preparation, storage and transfusion.

Microfluidic Flow Chambers Using Reconstituted Blood to Model Hemostasis and Platelet Transfusion In Vitro

Platelet transfusion and hemostasis was modeled using blood reconstitution and microfluidic flow chambers to investigate the function of blood banking platelets. The data demonstrate the consequences of platelet storage lesion on hemostasis, in vitro.

Blood platelets prepared for transfusion gradually lose hemostatic function during storage. Platelet function can be investigated using a variety of ...

Designing Microfluidic Devices for Studying Cellular Responses Under Single or Coexisting Chemical/Electrical/Shear Stress Stimuli

Microfluidic devices are capable of creating a precise and controllable cellular micro-environment of pH, temperature, salt concentration, and other physical or chemical stimuli. They have been commonly used for in vitro cell studies by providing in vivo like surroundings. Especially, how cells response to chemical gradients, electrical fields, and shear stresses has drawn many interests since these phenomena are important in understanding cellular properties and functions. These microfluidic chips can be made of glass substrates, silicon wafers, polydimethylsiloxane (PDMS) polymers, polymethylmethacrylate (PMMA) substrates, or polyethyleneterephthalate (PET) substrates. Out of these materials, PMMA substrates are cheap and can be easily processed using laser ablation and writing. Although a few microfluidic devices have been designed and fabricated for generating multiple, coexisting chemical and electrical stimuli, none of them was considered efficient enough in reducing experimental repeats, particular for screening purposes. In this report, we describe our design and fabrication of two PMMA-based microfluidic chips for investigating cellular responses, in the production of reactive oxygen species and the migration, under single or coexisting chemical/electrical/shear stress stimuli. The first chip generates five relative concentrations of 0, 1/8, 1/2, 7/8, and 1 in the culture regions, together with a shear stress gradient produced inside each of these areas. The second chip generates the same relative concentrations, but with five different electric field strengths created within each culture area. These devices not only provide cells with a precise, controllable micro-environment but also greatly increase the experimental throughput.

Micro-fabricated devices integrated with fluidic components provide an in vitro platform for cell studies mimicking the in vivo micro-environment. We developed polymethylmethacrylate-based microfluidic chips for studying cellular responses under single or coexisting chemical/electrical/shear stress stimuli.

Microfluidic devices are capable of creating a precise and controllable cellular micro-environment of pH, temperature, salt concentration, and other ...

A Protocol for Multiple Gene Knockout in Mouse Small Intestinal Organoids Using a CRISPR-concatemer

CRISPR/Cas9 technology has greatly improved the feasibility and speed of loss-of-function studies that are essential in understanding gene function. In higher eukaryotes, paralogous genes can mask a potential phenotype by compensating the loss of a gene, thus limiting the information that can be obtained from genetic studies relying on single gene knockouts. We have developed a novel, rapid cloning method for guide RNA (gRNA) concatemers in order to create multi-gene knockouts following a single round of transfection in mouse small intestinal organoids. Our strategy allows for the concatemerization of up to four individual gRNAs into a single vector by performing a single Golden Gate shuffling reaction with annealed gRNA oligos and a pre-designed retroviral vector. This allows either the simultaneous knockout of up to four different genes, or increased knockout efficiency following the targeting of one gene by multiple gRNAs. In this protocol, we show in detail how to efficiently clone multiple gRNAs into the retroviral CRISPR-concatemer vector and how to achieve highly efficient electroporation in intestinal organoids. As an example, we show that simultaneous knockout of two pairs of genes encoding negative regulators of the Wnt signaling pathway (Axin1/2 and Rnf43/Znrf3) renders intestinal organoids resistant to the withdrawal of key growth factors.

This protocol describes the steps for cloning multiple single guide RNAs into one guide RNA concatemer vector, which is of particular use in creating multi-gene knockouts using CRISPR/Cas9 technology. The generation of double knockouts in intestinal organoids is shown as a possible application of this method.

CRISPR/Cas9 technology has greatly improved the feasibility and speed of loss-of-function studies that are essential in understanding gene function. In ...

Light-sheet Fluorescence Microscopy to Capture 4-Dimensional Images of the Effects of Modulating Shear Stress on the Developing Zebrafish Heart

The hemodynamic forces experienced by the heart influence cardiac development, especially trabeculation, which forms a network of branching outgrowths from the myocardium. Genetic program defects in the Notch signaling cascade are involved in ventricular defects such as Left Ventricular Non-Compaction Cardiomyopathy or Hypoplastic Left Heart Syndrome. Using this protocol, it can be determined that shear stress driven trabeculation and Notch signaling are related to one another. Using Light-sheet Fluorescence Microscopy, visualization of the developing zebrafish heart was possible. In this manuscript, it was assessed whether hemodynamic forces modulate the initiation of trabeculation via Notch signaling and thus, influence contractile function occurs. For qualitative and quantitative shear stress analysis, 4-D (3-D+time) images were acquired during zebrafish cardiac morphogenesis, and integrated light-sheet fluorescence microscopy with 4-D synchronization captured the ventricular motion. Blood viscosity was reduced via gata1a-morpholino oligonucleotides (MO) micro-injection to decrease shear stress, thereby, down-regulating Notch signaling and attenuating trabeculation. Co-injection of Nrg1 mRNA with gata1a MO rescued Notch-related genes to restore trabeculation. To confirm shear stress driven Notch signaling influences trabeculation, cardiomyocyte contraction was further arrested via tnnt2a-MO to reduce hemodynamic forces, thereby, down-regulating Notch target genes to develop a non-trabeculated myocardium. Finally, corroboration of the expression patterns of shear stress-responsive Notch genes was conducted by subjecting endothelial cells to pulsatile flow. Thus, the 4-D light-sheet microscopy uncovered hemodynamic forces underlying Notch signaling and trabeculation with clinical relevance to non-compaction cardiomyopathy.

Here, we present a protocol to visualize developing hearts in zebrafish in 4-Dimensions (4-D). 4-D imaging, via light-sheet fluorescence microscopy (LSFM), takes 3-Dimensional (3-D) images over time, to reconstruct developing hearts. We show qualitatively and quantitatively that shear stress activates endocardial Notch signaling during chamber development, which promotes cardiac trabeculation.

The hemodynamic forces experienced by the heart influence cardiac development, especially trabeculation, which forms a network of branching outgrowths ...

Live Cell Analysis of Shear Stress on Pseudomonas aeruginosa Using an Automated Higher-Throughput Microfluidic System

A higher-throughput microfluidic in vitro bioreactor coupled with fluorescence microscopy has been used to study bacterial biofilm growth and morphology, including Pseudomonas aeruginosa (P. aeruginosa). Here, we will describe how the system can be used to study the growth kinetics and the morphological properties such as the surface roughness and textural entropy of P. aeruginosa strain PA01 that expresses an enhanced green fluorescent protein (PA01-EGFP). A detailed protocol will describe how to grow and seed PA01-EGFP cultures, how to set up the microscope and autorun, and conduct the image analysis to determine growth rate and morphological properties using a variety of shear forces that are controlled by the microfluidic device. This article will provide a detailed description of a technique to improve the study of PA01-EGFP biofilms which eventually can be applied towards other strains of bacteria, fungi, or algae biofilms using the microfluidic platform.

Live Cell Analysis of Shear Stress on Pseudomonas aeruginosa Using an Automated Higher-Throughput Microfluidic System

Here, we describe the use of a higher-throughput microfluidic bioreactor coupled with a fluorescent microscope for the analysis of shear stress effects on Pseudomonas aeruginosa biofilms expressing green fluorescent proteins, including instrument set up, the determination of biofilm coverage, growth rate, and morphological properties.

A higher-throughput microfluidic in vitro bioreactor coupled with fluorescence microscopy has been used to study bacterial biofilm growth and morphology, ...