We thank Valentina Greco for the K14-mCherry-H2B mice. We are grateful to the Emory University Physics Department Machine Shop for generating the glass coverslip disks. This work was funded by Career Development Award #IK2 BX005370 from the US Department of Veterans Affairs BLRD Service to LS, NIH Awards RF1-AG079269 and R56-AG072473 to MJMR, and I3 Emory SOM/GT Computational and Data Analysis Award to MJMR.

This research was performed in compliance with Emory University and Atlanta Veterans Affairs Medical Center animal care and use guidelines and has been approved by the Institutional Animal Care and Use Committee (IACUC).
1. Installing the live imaging insert on the inverted microscope stage
<ol>
	<li>Construct the insert using .stl files (Supplementary File 1, Supplementary File 2, and Supplementary File 3)&#160;specifying the 3D dimensions ...

Intravital Imaging Using an Inverted Microscope to Track Skin Cell Dynamics

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N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intravital+microscopy+techniques+to+image+wound+healing+in+mouse+skin.">Intravital microscopy techniques to image wound healing in mouse skin.</a> Methods in Molecular Biology. , 165-180 (2022).</li><li>Pal Arndt, ., 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+quantitative+3D+intravital+look+at+the+juxtaglomerular+renin-cell-niche+reveals+an+individual+intra/extraglomerular+feedback+system.">A quantitative 3D intravital look at the juxtaglomerular renin-cell-niche reveals an individual intra/extraglomerular feedback system.</a> Frontiers in Physiology. 13, 980787 (2022).</li><li>Oal Yam, A., 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=Neutrophil+conversion+to+a+tumor-killing+phenotype+underpins+effective+microbial+therapy.">Neutrophil conversion to a tumor-killing phenotype underpins effective microbial therapy.</a> Cancer Research. 83 (8), 1315-1328 (2023).</li><li>Huang, S., Rompolas, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-photon+microscopy+for+intracutaneous+imaging+of+stem+cell+activity+in+mice.">Two-photon microscopy for intracutaneous imaging of stem cell activity in mice.</a> Experimental Dermatology. 26 (5), 379-383 (2017).</li><li>Durr, N. 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In this study, we present a new tool that facilitates stable, long-term&#160;intravital imaging of intact mouse skin epithelia on inverted confocal microscopes. This invention is made of PLA, which is the most common and inexpensive 3D-printable material; all in-house 3D-printing costs for this insert amount to &#60;$5. The two separate insert pieces (Figure 1, Supplementary File 1, and Supplementary File 2) can be easily assembled using set screws (see <str...

Intravital microscopy is a powerful tool that allows the monitoring of cell behaviors in their unperturbed in vivo environments. This unique method has provided key insights into the inner workings of complex mammalian organ systems, including the lung1, brain2, liver3, mammary gland4, intestine5, and skin6. Furthermore, this approach has revealed cell behavioral alterations during tumor development7, wound healing8,9, inflammation10, and other diverse pathologies in situ. In this study, we focus on enhancing the accessibility of intravital microscopy to image live epithelial and stromal dynamics in intact mouse skin. Understanding cell behaviors in mammalian skin is of high clinical importance due to the remarkable regenerative and tumorigenic capacity of this tissue.
Intravital imaging in mice has&#160;been primarily performed using upright multiphoton microscopes due to their ability to provide high-resolution imaging at tissue depths &#62;100 &#181;m11,12. Nevertheless, these instruments&#160;lack the workhorse versatility and more general accessibility of inverted confocal microscopes, which are more user-friendly and cost-effective, provide the ability to image cultured cells, do not require complete darkness during image acquisition, and are generally safer, among other notable advantages13,14. In this study, we present a new tool that significantly enhances intravital imaging accessibility by adapting this approach for inverted confocal microscopes.
Here, we present a 3D-printed custom stage insert design that incorporates several key features to facilitate stable, long-term intravital imaging of mouse ear skin on an inverted confocal microscope (Figure 1, Figure 2, Figure 3, Figure 4, and Figure 5). These specialized features include an offset objective hole that allows the full body of an adult mouse to lay entirely flat during imaging. This minimizes the vibrational interference of mouse body movements on imaging and eliminates the need to administer ketamine and xylazine to dampen breathing, a practice often coupled with intravital imaging6. In addition, corner brackets on the insert correctly position an isoflurane nose cone to align with the face of the mouse, a metal ear clip immobilizes the mouse ear to a custom-built coverslip disk, and an optional detachable closed-loop biofeedback heat plate lies flush within the insert to support the mouse body temperature during long imaging sessions. The custom coverslip disk, which provides a flat surface essential for the mouse head and ear to lay flat, was generated in a machine shop by removing the walls of a generic coverslip-containing cell culture dish. The use of a 40x silicone oil immersion lens (1.25 numerical aperture [N.A.], 0.3 mm working distance) in conjunction with the coverslip disk and custom stage insert provides high resolution images &#62;50 &#181;m deep into the ear dermis.
To test the functionality of this new inverted microscope stage insert, we captured z-stacks spanning all epidermal epithelial layers over a 3 h time course in the ear of a live transgenic K14-H2B-mCherry15 adult mouse (epithelial nuclei in this mouse line contain a red fluorescent label) (Figure 6A-A&#39;). We also captured z-stacks spanning several fibroblast layers within the skin dermis over a 3 h time course in the ear of a live transgenic Pdgfra-rtTA16; pTRE-H2B-GFP17 adult mouse (fibroblast nuclei in this mouse line contain a green fluorescent label following doxycycline induction) (Figure 6B-D&#39;). Our high-resolution data demonstrate consistent stability by lack of drift in the x-, y-, and z-planes, thus proving the effectiveness of this new intravital imaging tool for use on inverted microscopes. Importantly, the dimensions of this 3D-printed stage insert can be adjusted, as described in Supplementary File 1, Supplementary File 2, and Supplementary File&#160;3, to fit any inverted microscope, and the positioning of the objective opening can be moved to alternative locations within the insert to better suit imaging a particular tissue and/or animal model of interest. This invention can thus empower individual laboratories, or investigators with core facility confocal access, to adapt this tool for their unique intravital imaging needs, thereby streamlining evaluation of diverse in vivo cell biology.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3D Printer</td>
			<td>Qudi Tech</td>
			<td>i-Fast</td>
			<td>3D prints using PLA material</td>
		</tr>
		<tr>
			<td>40x 1.25NA silicone objective lens</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>AxR Laser Scanning Confocal Microscope</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cotton Tipped Swab</td>
			<td>VWR</td>
			<td>76337-046</td>
			<td>Cream/ointment application</td>
		</tr>
		<tr>
			<td>Doxycycline hyclate</td>
			<td>Sigma-Aldrich</td>
			<td>D9891</td>
			<td>Induces GFP labeling of fibroblast nuclei in Pdgfra-rtTA; pTRE-H2B-GFP mice</td>
		</tr>
		<tr>
			<td>Flathead Screwdriver (2.5 mm)</td>
			<td></td>
			<td></td>
			<td>Affiix insert to microscope stage</td>
		</tr>
		<tr>
			<td>Flathead Screws x 4 (#6-32)</td>
			<td>Nikon</td>
			<td></td>
			<td>Screw insert into microscope stage</td>
		</tr>
		<tr>
			<td>Glass Bottom Culture Dish</td>
			<td>chemglass Life Sciences</td>
			<td>CLS-1811-002</td>
			<td>Modified by removing walls of dish for use as coverslip disk compatible with live insert; 35 mm wide disk contains 20 mm wide glass coverslip; dish walls were removed by machine shop</td>
		</tr>
		<tr>
			<td>Heat Plate controller</td>
			<td>Physitemp</td>
			<td>TCAT-2LV</td>
			<td>Animal Temperature Controller - Low Voltage; anal prob attachment for mouse body temperature monitoring</td>
		</tr>
		<tr>
			<td>Hex Wrench (1.5 mm)</td>
			<td></td>
			<td></td>
			<td>For M3 setscrew adjustments</td>
		</tr>
		<tr>
			<td>Hex Wrench (2.5 mm)</td>
			<td></td>
			<td></td>
			<td>Adjust tension on metal ear clip</td>
		</tr>
		<tr>
			<td>Intravital Imaging Insert</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Med-Vet International</td>
			<td>HPA030782-100uL</td>
			<td>Mouse anesthesia</td>
		</tr>
		<tr>
			<td>Labeling Tape (or Scotch Tape)</td>
			<td>VWR</td>
			<td>10127-458</td>
			<td>Alternative to metal ear clip to immobilize ear to coverslip</td>
		</tr>
		<tr>
			<td>Metal fastener</td>
			<td></td>
			<td></td>
			<td>used as ear clip</td>
		</tr>
		<tr>
			<td>Mouse: C57BL/6-Pdgfraem1(rtTA)Xsun/J</td>
			<td>The Jackson Laboratory</td>
			<td>RRID: IMSR_JAX:034459</td>
			<td>Fibrroblast-specific promoter driving doxycycline-inducible rtTA expression</td>
		</tr>
		<tr>
			<td>Mouse: K14-H2BPAmCherry</td>
			<td>Courtesy of Dr. Valentina Greco at Yale University</td>
			<td></td>
			<td>Labels epidermal epithelial cell nuclei with mCherry; referred to in text as &#34;K14-H2B-mCherry&#34;</td>
		</tr>
		<tr>
			<td>Mouse: pTRE-H2B-GFP: STOCK 
			Tg(tetO-HIST1H2BJ/GFP)47Efu/J</td>
			<td>The Jackson Laboratory</td>
			<td>RRID: IMSR_JAX:005104</td>
			<td>&#160;Labels fibroblast nuclei with GFP when combined with Pdgfra-rtTA and induced with doxycycline</td>
		</tr>
		<tr>
			<td>Multipurpose Sealing Wrap</td>
			<td>Glad</td>
			<td></td>
			<td>Enhance mouse warmth</td>
		</tr>
		<tr>
			<td>Optixcare</td>
			<td>VWR</td>
			<td>MSPP-078932779</td>
			<td>Eye lubricant</td>
		</tr>
		<tr>
			<td>Set screws x 3 (M3; 6 mm)</td>
			<td>Thorlabs</td>
			<td>SS3M6</td>
			<td>Attachment for heatplate module</td>
		</tr>
		<tr>
			<td>Silicone Immersion Oil</td>
			<td></td>
			<td></td>
			<td>Applied to 40x silicone objective</td>
		</tr>
		<tr>
			<td>Small Animal Heating Plate</td>
			<td>Physitemp</td>
			<td>HP-4M</td>
			<td>Provides heat to animal</td>
		</tr>
		<tr>
			<td>Somnoflow Low-Flow Electronic Vaporizer</td>
			<td>Kent Scientific</td>
			<td>SF-01</td>
			<td>Mouse anesthesia</td>
		</tr>
		<tr>
			<td>Vacuum Grease</td>
			<td>Flinn Scientific</td>
			<td>AP1095</td>
			<td>Seals coverslip disk to insert</td>
		</tr>
		<tr>
			<td>Veet</td>
			<td></td>
			<td></td>
			<td>hair removal&#160;</td>
		</tr>
		<tr>
			<td>Water circulating heat pad</td>
			<td>Stryker Medical</td>
			<td>TP700</td>
			<td>for mouse revival post-imaging</td>
		</tr>
	</tbody>
</table>

streamlined intravital imaging approach for long-term monitoring of epithelial tissue dynamics on an inverted confocal microscope

Understanding normal and aberrant in vivo cell behaviors is necessary to develop clinical interventions to thwart disease initiation and progression. It is therefore critical to optimize imaging approaches that facilitate the observation of cell dynamics in situ, where tissue structure and composition remain unperturbed. The epidermis is the body&#39;s outermost barrier, as well as the source of the most prevalent human cancers, namely cutaneous skin carcinomas. The accessibility of skin tissue presents a unique opportunity to monitor epithelial and dermal cell behaviors in intact animals using noninvasive intravital microscopy. Nevertheless, this sophisticated imaging approach has primarily been achieved using upright multiphoton microscopes, which represent a significant barrier for entry for most investigators. This study presents a custom-designed, 3D-printed microscope stage insert suitable for use with inverted confocal microscopes, streamlining the long-term intravital imaging of ear skin in live transgenic mice. We believe this versatile invention, which may be customized to fit the inverted microscope brand and model of choice and adapted to image additional organ systems, will prove invaluable to the greater scientific research community by significantly enhancing the accessibility of intravital microscopy. This technological advancement is critical for bolstering our understanding of live cell dynamics in normal and disease contexts.

Author Spotlight: Developing a Tool for Using Inverted Confocal Microscopes for In Vivo Intravital Imaging 

Streamlined Intravital Imaging Approach for Long-Term Monitoring of Epithelial Tissue Dynamics on an Inverted Confocal Microscope

We developed a tool to perform intravital imaging on live mice using an inverted confocal microscope. This enables us to track skin cell dynamics throughout homeostasis and compare cell behaviors during disease onset and progression. Multiphoton microscopy is the primary approach applied to achieve intravital cell tracking.However, the disadvantages of these microscopes include limited day-to-day imaging versatility, high cost, and technical complexity. Our new tool enables the use of versatile inverted confocal microscopes for in vivo intravital imaging. By modifying the design file, the stage insert dimensions can be customized to fit any make of inverted microscope.The objective hole can be resized and repositioned to fit any animal model and tissue of choice.

Proper assembly of the live imaging insert on an inverted confocal microscope and appropriate orientation of a transgenic mouse atop the insert is validated by acquiring z-stacks of fluorescently-labeled, live ear tissue over a time course &#8805;1 h with minimal evidence of drift in the x-, y-, and z-axes. Images should be captured at consistent intervals (interval time will depend on the biological question, strength of fluorescence&#160;signal, etc.) so that cell dynamics and image drift can be tracked over time. Thro...

Watch this Scientific Journal Video about Developing a Tool for Using Inverted Confocal Microscopes for In Vivo Intravital Imaging at JoVE.com

The protocol presents a new tool to simplify intravital imaging using inverted confocal microscopy.

Understanding normal and aberrant in vivo cell behaviors is necessary to develop clinical interventions to thwart disease initiation and progression. It ...

streamlined-intravital-imaging-approach-for-long-term-monitoring