Name: precision cut lung slices as an efficient tool for ex vivo pulmonary vessel structure and contractility studies
Uploaded: 2021-05-24T13:00:00
Description: 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

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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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, ...

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