The authors would like to thank Drs. Yuan Hao and Kaifeng Liu for their technical support. This work was supported by an NIH 1R01 HL150106-01A1, the Parker B. Francis Fellowship, and the Pulmonary Hypertension Association Aldrighetti Research Award to Dr. Ke Yuan.

All animal care was in accordance with the guidelines of Boston Children&#39;s Hospital and the Institutional Animal Care and Use Committee approved protocols. The mice used in this study are wild type C57/B6 mice and Cdh5-CreERT2 x Ai14 tdTomato crossed mice.
1. Preparation of solutions
<ol>
	<li>Prepare phosphate buffer solution (1x PBS) and 2% agarose solution required during the experiment in advance.
	<ol>
		<li>Mix 2 g agarose powder into 100 mL of autoclaved water. Heat it in the micr...

<ol>
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P., 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=Precision+cut+lung+slices+as+an+efficient+tool+for+in+vitro+lung+physio-pharmacotoxicology+studies.">Precision cut lung slices as an efficient tool for in vitro lung physio-pharmacotoxicology studies.</a> Xenobiotica. 43 (1), 63-72 (2013).</li><li>Springer, J., Fischer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Substance+P-induced+pulmonary+vascular+remodelling+in+precision+cut+lung+slices.">Substance P-induced pulmonary vascular remodelling in precision cut lung slices.</a> The European Respiratory Journal. 22 (4), 596-601 (2003).</li><li>Suleiman, 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=Argon+reduces+the+pulmonary+vascular+tone+in+rats+and+humans+by+GABA-receptor+activation.">Argon reduces the pulmonary vascular tone in rats and humans by GABA-receptor activation.</a> Scientific Reports. 9 (1), 1902 (2019).</li><li>Rieg, A. 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=Cardiovascular+agents+affect+the+tone+of+pulmonary+arteries+and+veins+in+precision-cut+lung+slices.">Cardiovascular agents affect the tone of pulmonary arteries and veins in precision-cut lung slices.</a> PLoS One. 6 (12), 29698 (2011).</li><li>Perez, J. F., Sanderson, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+frequency+of+calcium+oscillations+induced+by+5-HT,+ACH,+and+KCl+determine+the+contraction+of+smooth+muscle+cells+of+intrapulmonary+bronchioles.">The frequency of calcium oscillations induced by 5-HT, ACH, and KCl determine the contraction of smooth muscle cells of intrapulmonary bronchioles.</a> The Journal of General Physiology. 125 (6), 535-553 (2005).</li><li>Deng, C. Y., 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=Upregulation+of+5-hydroxytryptamine+receptor+signaling+in+coronary+arteries+after+organ+culture.">Upregulation of 5-hydroxytryptamine receptor signaling in coronary arteries after organ culture.</a> PLoS One. 9 (9), 107128 (2014).</li><li>Sandker, S. 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=Adventitial+dissection:+A+simple+and+effective+way+to+reduce+radial+artery+spasm+in+coronary+bypass+surgery.">Adventitial dissection: A simple and effective way to reduce radial artery spasm in coronary bypass surgery.</a> Interactive Cardiovascular and Thoracic Surgery. 17 (5), 784-789 (2013).</li><li>Naik, J. 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=Pressure-induced+smooth+muscle+cell+depolarization+in+pulmonary+arteries+from+control+and+chronically+hypoxic+rats+does+not+cause+myogenic+vasoconstriction.">Pressure-induced smooth muscle cell depolarization in pulmonary arteries from control and chronically hypoxic rats does not cause myogenic vasoconstriction.</a> Journal of Applied Physiology. 98 (3), 1119-1124 (2005).</li><li>Lopez-Lopez, J. 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=Diabetes+induces+pulmonary+artery+endothelial+dysfunction+by+NADPH+oxidase+induction.">Diabetes induces pulmonary artery endothelial dysfunction by NADPH oxidase induction.</a> American Journal of Physiology. Lung Cellular and Molecular Physiology. 295 (5), 727-732 (2008).</li><li>Gonzalez-Tajuelo, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spontaneous+pulmonary+hypertension+associated+with+systemic+sclerosis+in+P-selectin+glycoprotein+Ligand+1-deficient+mice.">Spontaneous pulmonary hypertension associated with systemic sclerosis in P-selectin glycoprotein Ligand 1-deficient mice.</a> Arthritis &amp; Rheumatology. 72 (3), 477-487 (2020).</li><li>Bai, Y., Sanderson, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+the+Ca2++sensitivity+of+airway+smooth+muscle+cells+in+murine+lung+slices.">Modulation of the Ca2+ sensitivity of airway smooth muscle cells in murine lung slices.</a> American Journal of Physiology. Lung Cellular and Molecular Physiology. 291 (2), 208-221 (2006).</li><li>Nishiyama, S. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+function+and+endothelin-1:+tipping+the+balance+between+vasodilation+and+vasoconstriction.">Vascular function and endothelin-1: tipping the balance between vasodilation and vasoconstriction.</a> Journal of Applied Physiology. 122 (2), 354-360 (2017).</li><li>Schneider, M. P., Inscho, E. W., Pollock, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Attenuated+vasoconstrictor+responses+to+endothelin+in+afferent+arterioles+during+a+high-salt+diet.">Attenuated vasoconstrictor responses to endothelin in afferent arterioles during a high-salt diet.</a> American Journal of Physiology. Renal Physiology. 292 (4), 1208-1214 (2007).</li><li>Inscho, E. W., Imig, J. D., Cook, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Afferent+and+efferent+arteriolar+vasoconstriction+to+angiotensin+II+and+norepinephrine+involves+release+of+Ca2++from+intracellular+stores.">Afferent and efferent arteriolar vasoconstriction to angiotensin II and norepinephrine involves release of Ca2+ from intracellular stores.</a> Hypertension. 29, 222-227 (1997).</li><li>Vecchione, 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=Protection+from+angiotensin+II-mediated+vasculotoxic+and+hypertensive+response+in+mice+lacking+PI3Kgamma.">Protection from angiotensin II-mediated vasculotoxic and hypertensive response in mice lacking PI3Kgamma.</a> The Journal of Experimental Medicine. 201 (8), 1217-1228 (2005).</li></ol>

In this manuscript, an enhanced method to produce high-resolution images of murine lung tissue that preserves the vascular structure and optimizes experimental flexibility is described, specifically using the application of PCLS to obtain microslices of lung tissue that can be viewed in three dimensions with preserved contractility of the vasculature. Using the viability reagent, the protocol demonstrates that carefully prepared and preserved slices can retain viability for more than a week. Preserved viability of the mi...

Advances in the preparation and imaging of lung tissue that preserves cellular components without sacrificing anatomical structure provide a detailed understanding of pulmonary diseases. The ability to identify proteins, RNA, and other biological compounds while maintaining physiological structure offers vital information on the spatial arrangement of cells that can broaden the understanding of the pathophysiology in numerous pulmonary diseases. These detailed images can lead to a better understanding of pulmonary vascular diseases, such as pulmonary artery hypertension, when applied to animal models, potentially leading to improved therapeutic strategies.
Despite advances in technology, obtaining high-quality images of murine lung tissue remains a challenge. The respiratory cycle is driven by a negative intrathoracic pressure generated during inhalation1. When traditionally obtaining biopsies and preparing lung samples for imaging, the negative pressure gradient is lost resulting in the collapse of the airway and vasculature, which no longer represents itself in its present state. To achieve realistic images reflective of current conditions, the pulmonary airways must be reinflated, and the vasculature perfused, changing the dynamic lung into a static fixture. The application of these distinct techniques allows preservation of structural integrity, pulmonary vasculature, and cellular components, including immune cells such as macrophages, allowing lung tissue to be viewed as close to its physiological state as possible.
Precision cut lung slicing (PCLS) is an ideal tool for studying the anatomy and physiology of pulmonary vasculature2. PCLS provides detailed imaging of the lung tissue in three dimensions while preserving structural and cellular components. PCLS has been used in animal and human models to allow for live, high-resolution images of cellular functions in three dimensions, making it an ideal tool to study potential therapeutic targets, measure small airway contraction and study the pathophysiology of chronic lung diseases such as COPD, ILD, and lung cancer3. Using similar techniques, the exposure of PCLS samples to vasoconstrictors can preserve lung structure and vessel contractility, replicating in vitro conditions. Along with preserving contractility, prepared samples can undergo additional analysis such as RNA sequencing, Western blot, and flow cytometry when prepared correctly. Finally, reporter color labeled cells marked with tdTomato fluorescence after lung harvest can preserve labeling after preparing microslices, making it ideal for cell tracking studies. The integration of these techniques provides a sophisticated model preserving the spatial arrangement of cells and vessel contractility that can lead to a more detailed understanding of the signaling cascades and potential therapeutic options in pulmonary vasculature disease.
In this manuscript, PCLS murine lung tissue is exposed to vasoconstrictors, demonstrating preserved structural integrity and vessel contractility. The study demonstrates that the tissue prepared and handled appropriately can remain viable for 10 days. The study also demonstrates the preservation of cells with endogenous fluorescence (tdTomato), allowing samples to provide high-resolution images of the pulmonary vasculature and architecture. Finally, ways to handle and prepare tissue slices for RNA measurement and Western blot to investigate underlying mechanisms have been described.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.5cc of fractionated heparin in syringe</td>
			<td>BD</td>
			<td>100 USP units per mL</td>
			<td></td>
		</tr>
		<tr>
			<td>1X PBS</td>
			<td>Corning</td>
			<td>&#160;21-040-CM</td>
			<td></td>
		</tr>
		<tr>
			<td>20 1/2 inch gauge blunt end needle for trachea cannulation</td>
			<td>Cml Supply</td>
			<td>90120050D</td>
			<td></td>
		</tr>
		<tr>
			<td>30cc syringe</td>
			<td>BD</td>
			<td>309650</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti Anti solution</td>
			<td>Gibco</td>
			<td>15240096</td>
			<td></td>
		</tr>
		<tr>
			<td>Automated vibrating blade microtome</td>
			<td>Leica</td>
			<td>VT1200S</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Viability Reagent (alamarBlue)</td>
			<td>Thermofisher</td>
			<td>DAL1025</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal</td>
			<td>Zeiss</td>
			<td>880</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s Modified Eagle Medium and GLutaMAX, supplemented with 10% FBS, 1% Pen/Strep</td>
			<td>Gibco</td>
			<td>10569-010</td>
			<td></td>
		</tr>
		<tr>
			<td>Endothelin-1</td>
			<td>Sigma</td>
			<td>E7764</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>7447-40-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Mortar and Pestle</td>
			<td>Amazon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>RIPA lysis and extraction buffer</td>
			<td>Thermoscientific</td>
			<td>89900</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical suture 6/0</td>
			<td>FST</td>
			<td>18020-60</td>
			<td></td>
		</tr>
		<tr>
			<td>TRIzol Reagent</td>
			<td>Invitrogen, Thermofisher</td>
			<td>15596026</td>
			<td></td>
		</tr>
		<tr>
			<td>UltraPure Low Melting Point Agarose</td>
			<td>Invitrogen</td>
			<td>16520050</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibratome</td>
			<td>Leica Biosystems</td>
			<td>VT1200 S</td>
			<td></td>
		</tr>
		<tr>
			<td>Winged blood collection set (Butterfly needle) 25-30G</td>
			<td>BD</td>
			<td>25-30G</td>
			<td></td>
		</tr>
	</tbody>
</table>

precision cut lung slices as an efficient tool for ex vivo pulmonary vessel structure and contractility studies

The visualization of murine lung tissue provides valuable structural and cellular information regarding the underlying airway and vasculature. However, the preservation of pulmonary vessels that truly represents physiological conditions still presents challenges. In addition, the delicate configuration of murine lungs result in technical challenges preparing samples for high-quality images that preserve both cellular composition and architecture. Similarly, cellular contractility assays can be performed to study the potential of cells to respond to vasoconstrictors in vitro, but these assays do not reproduce the complex environment of the intact lung. In contrast to these technical issues, the precision-cut lung slice (PCLS) method can be applied as an efficient alternative to visualize lung tissue in three dimensions without regional bias and serve as a live surrogate contractility model for up to 10 days. Tissue prepared using PCLS has preserved structure and spatial orientation, making it ideal to study disease processes ex vivo. The location of endogenous tdTomato-labeled cells in PCLS harvested from an inducible tdTomato reporter murine model can be successfully visualized by confocal microscopy. After exposure to vasoconstrictors, PCLS demonstrates the preservation of both vessel contractility and lung structure, which can be captured by a time-lapse module. In combination with the other procedures, such as western blot and RNA analysis, PCLS can contribute to the comprehensive understanding of signaling cascades that underlie a wide variety of disorders and lead to a better understanding of the pathophysiology in pulmonary vascular diseases.

When added to cells or tissue, the viability reagent is modified by the reducing environment of viable tissue and turns pink/red, becoming highly fluorescent. The representative color changes detected from day 0-1 and day 9-10 are demonstrated in Figure 3. As noted, the solution started blue and turned pink overnight, demonstrating viability. Color change typically occurs within 1-4 h; however, a longer time may be necessary. To assay for viability, a plate reader was used to determine the a...

Watch this Scientific Journal Video about Precision Cut Lung Slices as an Efficient Tool for Ex vivo Pulmonary Vessel Structure and Contractility Studies at JoVE.com

Precision Cut Lung Slices as an Efficient Tool for Ex vivo Pulmonary Vessel Structure and Contractility Studies

Presented here is a protocol for preserving the vascular contractility of PCLS murine lung tissue, resulting in a sophisticated three-dimensional image of the pulmonary vasculature and airway, which can be preserved for up to 10 days that is susceptible to numerous procedures.

Precision Cut Lung Slices as an Efficient Tool for Ex vivo Pulmonary Vessel Structure and Contractility Studies

The visualization of murine lung tissue provides valuable structural and cellular information regarding the underlying airway and vasculature. However, ...

Precision cut lung slices method will preserve the structure and spatial orientations in three dimensions without regional bias and can serve as a live surrogate model for vessels and airway contractility measurements. In combination with time-lapse imaging, Western blot, and RNA analysis, precision cut lung slices contribute to the comprehensive understanding of signaling cascades that underlie a wide variety of disorders and lead to a better understanding of the pathophysiology in pulmonary vascular diseases. To begin, place the euthanized adult mouse in a supine position and secure it in place by taping the paws and nose to the table with adhesive tape.Spray the ventral surface of the mouse with 70%ethanol. Use forceps to lift the abdominal skin of the mouse at the location of the bladder and surgical scissors to cut at the midline, moving superiorly to the cervical region to expose the trachea. Then use tweezers to lift the underlying fascia layer and use surgical scissors to expose the visceral organs and mediastinal compartment, again cutting inferiorly to superior.Cut the sternum at the midline to expose the heart and lung. Dissect the diaphragm carefully from the liver and the abdominal compartment. Locate the inferior vena cava under the intestines and cut it.After locating the right ventricle, use a 25 to 30 gauge butterfly needle to inject 0.5 milliliters of 1%fractionated heparin into the right ventricle and flush it slowly but steadily with 10 to 15 millimeters of PBS. After locating the larynx, use blunt tip tweezers to dissect the surrounding fascia and tissue, then place the surgical suture under the trachea and loosely tie a surgical knot. Place a small hole in the trachea superior to the string and cannulate with a 20 gauge blunt-ended needle.Tighten the suture around the needle and trachea using a surgical knot. Then inject 2.5 to 4 milliliters of agarose into the trachea and monitor for inflation of the lung. After the agarose injection, pour cold PBS over the lung to solidify the agarose.Then cut the trachea superior to the surgical suture and dissect the lung and heart from the mediastinum by removing any adhesions and fascia. After solidification, place the tissue in DMEM in a Petri dish on ice, and immediately proceed to slicing one lobe using a vibratome machine. To prepare the lung slices, attach the sample to the platform with superglue, keeping the medial side facing up.Then fill the sample container with PBS. Fill the container with ice to keep the surrounding PBS and sample cold. Turn on the vibratome.Adjust the thickness to 300 micrometers, frequency to 100 Hertz, amplitude to 0.6 millimeters, and speed to five micrometers per second. Using an Allen wrench, turn the blade holder into the safe position and open the jaws to insert a blade. Then tighten the jaws with an Allen wrench.Place the sample onto the box, ensuring it is submerged in PBS. Slide the box up in the correct position and make sure it is secure. Turn the blade holder into the appropriate position for slicing.Bring the vibratome blade up to the edge of the block and manually lower the blade until it is even with the top of the sample. Confirm the settings and run the vibratome. After the fresh slices are cut, remove the samples from the PBS and place them into a sterile Petri dish with 10 milliliters of DMEM containing one-time antimycotic antibiotic.After placing all the slices in a Petri dish, retract the blade entirely and use the Allen wrench to raise the blade into a safe position. Store the samples in DMEM at 37 degrees Celsius. And place a vibratome slice on a microscope slide.Use a cleaning wipe to remove excess medium. Place the sample on the phase contrast microscopy and use 10 to 20X magnification to identify a vessel. Then add 500 microliters of vasoconstrictors, such as 60 millimolar potassium chloride or one micromolar endothelin-1 to completely submerge the slide.Observe and capture the video by recording for 30 to 60 seconds. Before beginning the experiment, fill a small polystyrene foam box with one liter of liquid nitrogen and place two 1.5 milliliter microcentrifuge tubes in the container with liquid nitrogen. Place four to five fresh vibratome slices in a mortar bowl.Pour 5 to 10 milliliters of liquid nitrogen on top of the slices and quickly use the pestle to grind the slices into powder before the liquid nitrogen evaporates. Use a pre-chilled steel laboratory scooper to scoop the powder into the two chilled microcentrifuge tubes and lyse the powder by adding 500 microliters of RNA extraction reagent for RNA isolation or 500 microliters of RIPA buffer for protein lysis. In the representative viability experiment, the color change of the PCLS slices was detected from day zero to one and day nine to 10.The solution was initially blue and turned pink overnight, demonstrating viability. Color change typically occurred within one to four hours, but a longer time may be necessary. The daily difference between absorbance at 562 and 613 nanometer wavelengths for the vibratome-prepared tissue is shown here.The constriction of the vasculature in a vibratome-prepared lung tissue using endothelin-1 and potassium chloride can be visualized here. The preservation of tdTomato labeling in cells one week after tamoxifen injection is demonstrated in these lung slices. It is most important to perform the lung clearing and inflation step well to remove all blood from circulation before additional experiments and imaging.In addition to vascular diseases, PCLS can be applied to study physiobiology of airway-related disease, and can be further tested on human lung tissues in clinically relevant scenarios.

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5.3K vistas.  Boston Children's Hospital. El método de corte pulmonar de precisión preservará la estructura y las orientaciones espaciales en tres dimensiones sin sesgo regional y puede servir como un modelo sustituto vivo para las mediciones de contractilidad de los vasos y las vías respiratorias. En combinación con imágenes de lapso de tiempo, Western blot y análisis de ARN, las rodajas pulmonares cortadas con precisión contribuyen a la comprensión integral de las cascadas de señalización que subyacen a una amplia varied...