This work was funded by Swiss National Foundation (SNF) project grant 31003A_135649, 31003A_153457 and 31003A_172994 (to JVS), and Leopoldina fellowship LPDS 2011-16 (to BS). This work benefitted from optical setups of the "Microscopy Imaging Center" (MIC) of the University of Bern.

All animal work has been approved by the Cantonal Committee for Animal Experimentation and conducted according to federal guidelines.
1. Anesthetize the Mouse
<ol>
	<li>Wear personal protective equipment, including lab coat and gloves.</li>
	<li>Mix ketamine, xylazine, and saline to a working concentration of 20 mg/mL and 1 mg/mL, respectively. Inject the working stock intraperitoneally (i.p.) at 8-10 &#181;L/g of mouse. Place the mouse back into the cage. 
	NOTE: This protocol has been tested for 6- to 40-week-old male and female mice with a C57BL/6 background.</li>
	<li>Prepare the acepromazine solution at 2.5 mg/mL and inject 30 &#181;L i.p., 15 min after the ketamine-xylazine injection (75 &#181;g/mouse).</li>
	<li>After 5-15 min, check for adequate anesthesia and analgesia by controlling for reflexes, e.g., withdrawal reflex of the paw or corneal reflex.</li>
	<li>Control for reflexes approximately every 30 min during the entire duration of the experiment. Subcutaneously inject ketamine/xylazine at 1.5 &#181;L/g of mouse, every 60 min or earlier if reflexes are positive. 
	NOTE: Inhalation anesthesia such as isoflurane cannot be used with this protocol, owing to the fixation of the mouse.</li>
</ol>
2. Remove the Fur from the Operating Area
<ol>
	<li>Use an electric razor to shave an area that expands roughly from 5 mm caudal of the mouth towards the front legs, stretching over the jaws towards both ears.</li>
	<li>Apply hair removal cream to the shaved area with a cotton swab. Carefully and thoroughly remove after 3 min, e.g., by wiping with wet tissues.</li>
</ol>
3. Fix the Mouse on the Stage
NOTE: This protocol uses a customized stage (Figure 1) equipped with two freely adjustable holders for cover slips (one attached to the stage with a screw, the other fixed permanently onto it); adjustable stereotactic ear bars; a string, which can be tightened with a screw; a freely adjustable metal heating ring; and a raised area designated to place the torso of the mouse. This stage is modified from a popliteal lymph node stage, with an added stereotactic holder and a support for the lower cover slip holding the exteriorized SMG. Detailed plans or quotes of the stage are available upon request.
<ol>
	<li>Prepare the stage by removing the holders for the heating ring and the removable cover slip holder. Loosen the screws of the ear bar holders and the fixed cover slip holder. Tape a piece of gauze to the center area of the stage, serving as bedding for the mouse.</li>
	<li>Use glue (see Table of Materials) to attach a 20 mm diameter cover glass to the top of a cylindrical metal holder (this will be the lower cover glass). Glue a 25 mm cover glass to the bottom of the flat metal holder (this will be the upper cover glass). Ensure that the cover glasses overlap approximately 2-3 mm with metal holders and that the rest of the glass remains free of grease and glue.</li>
	<li>Place the mouse on its back onto the gauze, perpendicular to the stretched string, with the head centered between the ear bars.</li>
	<li>Fix the upper extremities of the mouse onto the stage with surgical tape.</li>
	<li>Next, hook the string into the upper front incisors and tighten until the jaw reaches a horizontal position. Use an angled curved forceps to slightly pull out the tongue from the mouth, which facilitates breathing.</li>
	<li>Tightly, but not forcefully, pull the tail and tape it to the stage.</li>
	<li>Align the ear bars to achieve an angle of approximately 30&#176; between the bar and the edge of the stage. To ensure this angle, use a triangle ruler to draw a right and left 30&#176; angle on a sheet of paper, and place the transparent stage on the paper to align the holders accordingly.</li>
	<li>Fix the jaw between the ear bars by simultaneously moving the left and right bar inwards until the jaw is immotile, and tighten screws. Observe chest movement before, during, and after fixing the jaw. Reduced or absent breathing indicates that the bars are fixed at the neck, not the jaw bone; in this case, repeat the fixing procedure immediately.</li>
	<li>Provide heating to the mouse, e.g., by placing a heating lamp nearby and/or a heating pad underneath the stage.</li>
</ol>
4. Surgical Exposure of the Salivary Gland Using a Stereomicroscope
NOTE: The following steps require the use of a stereomicroscope, fine forceps, and surgical scissors. Since the procedure is terminal, it is not necessary to maintain sterile operating conditions. Ethanol-cleaned instruments suffice.
<ol>
	<li>Locate the approximate position of the right SMG lobe by looking for a slight bulge in the skin approximately 15 mm caudal of the mouth and 5 mm medial of the jaw line. Lift a small skin fold in the center of the bulge and cut it to create and opening of approximately 5 mm length.</li>
	<li>Immediately apply a 4 mm-high ring of vacuum grease on the skin surrounding the cut. (Use a vacuum grease-filled syringe with a blunted 25 G hypodermic needle).</li>
	<li>Fill the grease ring with saline to ensure the tissue remains moist during the operation.</li>
	<li>Under the stereomicroscope, disrupt the connective tissue using the following procedure: Use one fine forceps to firmly hold a piece of connective tissue directly attached to the SMG, and use a second forceps to pull the distal connective tissue until it ruptures. Ensure that some connective tissue remains attached to the SMG; this is desirable since it allows handling. Do not touch the gland itself with the forceps, since this will cause bleeding.</li>
	<li>Repeat this motion of disrupting connective tissue first on top of the gland, then on the medial side (between the right and left lobe of the SMG). Do not separate the sublingual from the submandibular gland.</li>
	<li>Continue to remove the lateral connective tissue counterclockwise around the SMG (medial to caudal, to distal, to rostral).</li>
	<li>Ensure that the blood supply, efferent lymphatics, and salivary duct, which are all located in a bundle at the cranial site of the gland, are not ruptured.</li>
	<li>Once the lateral connective tissue is disrupted, use forceps to pull the connective tissue attached to the caudal end of the SMG upwards to lift the caudal end of the SMG. Disrupt the connective tissue below the SMG lobe, starting from the caudal and moving towards the rostral end.</li>
	<li>Continue until the connective tissue to all sites of the SMG is removed (excluding the rostral site with major feeding/draining blood vessels and the WD).</li>
</ol>
5. Fixing the Gland
<ol>
	<li>Confirm that the grease ring holding the saline is at least 4 mm high and not leaking (see step 4.2).</li>
	<li>Install the lower cover glass (see step 3.2) by attaching the metal bar to its height-adjustable holder. Ensure that the cover slip holder is adjusted to the upmost position and does not touch the grease ring when attached to the stage. Position the holder from the caudal direction at an angle of approximately 60&#176; to the mouse, with the cover slip covering roughly two thirds (caudal and distal parts) of the exposed lobe. Lower the cover glass until it makes contact with the gland.</li>
	<li>Complete the grease ring on top of the cover glass to form a new saline reservoir.</li>
	<li>Carefully pull the SMG lobe on top of the cover slip with forceps, only touching the connective tissue attached to it (the organ can be flipped with the bottom site facing upwards).</li>
	<li>Ensure that the grease ring has an even height of at least 4 mm and does not leak. If necessary, refill the saline reservoir using a 30 G syringe filled with saline.</li>
	<li>Ensure that the cover glass holder for the upper cover glass is in its upmost position. Use the screw to attach the metal holder with the 25 mm upper cover glass to the holder. Use the adjustable screws of the holder to position the cover glass so that the SMG is centered in the middle.</li>
	<li>Use the screws of adjustable holder to lower the top cover glass until it directly contacts the SMG. Observe the shape and coloring of the gland during this step. If the gland surface area appears larger, or the coloring changes (for instance from pink to white), immediately put the cover glass to a higher position to relieve pressure on the SMG.</li>
	<li>Check the saline reservoir for leaks by looking for air bubbles and or drops of saline outside the reservoir. If a leak or air bubble is detected, remove both cover slips and all grease and restart from step 2.</li>
	<li>Screw shut all fixation screws.</li>
</ol>
6. Fixing the Heating Ring and Temperature Probe
<ol>
	<li>Insert a temperature probe into the reservoir and position it close to the gland, then tape the probe wire to the stage.</li>
	<li>Apply a grease ring to the top cover slip, with the SMG in the center (the diameter of the grease ring should correspond to diameter of the heating ring). Position the heating ring on top of the cover slip and seal with grease. Tape the tubing of the heating ring to the stage.</li>
</ol>
7. Imaging
NOTE: We use an upright two-photon microscope system equipped with a tunable Ti:Sa Laser and a fluorescent microscope with water-immersion 20X or 25X objectives. Real time correction of tissue drift during acquisition can be implemented by using an automated stage and VivoFollow19. This improves the stability of image acquisition, but is not required.
<ol>
	<li>Turn on the upright microscopy system using an appropriate software provided by the microscope manufacturer. Tune the Ti:Sa Laser to a 780-900 nm excitation wavelength.</li>
	<li>Connect the heating tubing to the heating ring. A peristaltic water pump circulates hot water (heated by submerging part of the tubing in an 80&#176;C water bath) through the ring to warm the SMG.</li>
	<li>Connect the temperature probe to a digital thermometer. Adjust the speed of the peristaltic pump if the temperature is not between 35-39 &#176;C. The faster the pump works, the warmer the object gets, and vice versa.</li>
	<li>Before starting image acquisition, perform a visual control of the blood flow velocities. Carefully check leukocyte passage through the thin capillaries or by fluorescent dextran injection. 
	NOTE: Intravenously injected fluorescent dextran will immediately fill out the entire SMG vasculature when blood flow is physiological. This is virtually always the case in this procedure.</li>
	<li>To follow immune cells, imaging depth is typically between 20-150 &#181;m below the surface of the SMG identified by the 2nd harmonic generation signal. Record image stacks of 150-300 &#181;m field of view with pixel resolution of approximately 512 x 512 or higher, and z-depths of 20-60 &#181;m with spacing of 2-4 &#181;m between images. Repeat stack acquisition every 20-30 s for a total duration of 20-60 min.</li>
	<li>Use the digital thermometer to control the minimum and maximum temperature levels after acquisition of one image sequence. Discard the image sequence if the minimum or maximum are not in the range of 37 &#177; 2 &#176;C. Refill the water for immersion of objective between image sequences.</li>
	<li>At the end of the imaging session, euthanize the mice by CO2 asphyxiation under anesthesia. 
	NOTE: This is in accordance to Swiss federal guidelines of animal experimentation; other guidelines for euthanasia may apply elsewhere.</li>
</ol>

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L., Shakhar, G., Dudziak, 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=Visualizing+dendritic+cell+networks+in+vivo.">Visualizing dendritic cell networks in vivo.</a> Nat Immunol. 5 (12), 1243-1250 (2004).</li><li>Riedl, J., Flynn, K. C., Raducanu, 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=Lifeact+mice+for+studying+F-actin+dynamics.">Lifeact mice for studying F-actin dynamics.</a> Nat Methods. 7 (3), 168-169 (2010).</li><li>Chtanova, T., Hampton, H. R., Waterhouse, L. 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=Real-time+interactive+two-photon+photoconversion+of+recirculating+lymphocytes+for+discontinuous+cell+tracking+in+live+adult+mice.">Real-time interactive two-photon photoconversion of recirculating lymphocytes for discontinuous cell tracking in live adult mice.</a> J Biophotonics. 7 (6), 425-433 (2014).</li><li>Kyratsous, N. I., Bauer, I. J., Zhang, 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=Visualizing+context-dependent+calcium+signaling+in+encephalitogenic+T+cells+in+vivo+by+two-photon+microscopy.">Visualizing context-dependent calcium signaling in encephalitogenic T cells in vivo by two-photon microscopy.</a> Proc Natl Acad Sci U S A. 114 (31), E6381-E6389 (2017).</li><li>Mank, M., Reiff, D. F., Heim, N., Friedrich, M. W., Borst, A., Griesbeck, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+FRET-based+calcium+biosensor+with+fast+signal+kinetics+and+high+fluorescence+change.">A FRET-based calcium biosensor with fast signal kinetics and high fluorescence change.</a> Biophys J. 90 (5), 1790-1796 (2006).</li><li>Tsyboulski, D., Orlova, N., Saggau, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amplitude+modulation+of+femtosecond+laser+pulses+in+the+megahertz+range+for+frequency-multiplexed+two-photon+imaging.">Amplitude modulation of femtosecond laser pulses in the megahertz range for frequency-multiplexed two-photon imaging.</a> Opt Express. 25 (8), 9435 (2017).</li><li>Potma, E. O., Xie, X. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+single+lipid+bilayers+with+coherent+anti-Stokes+Raman+scattering+(CARS)+microscopy.">Detection of single lipid bilayers with coherent anti-Stokes Raman scattering (CARS) microscopy.</a> J Raman Spectrosc. 34 (9), 642-650 (2003).</li></ol>

No conflicts of interest declared.

This protocol offers a straightforward approach for in vivo imaging of murine submandibular and sublingual salivary glands using upright non-linear microscopy often used in the field of immunology. The method can be adapted for the imaging of other exocrine glands in the head and neck region. For instance, our lab has performed imaging of the lacrimal gland in an analogous manner (not shown).
Removing the connective tissue around the SMG is the most critical step of this protocol, sin...

Saliva is secreted by exocrine glands to lubricate food, protect the mucosal surfaces of the oral tract, and to deliver digestive enzymes as well as antimicrobial substances1,2. In addition to minor salivary glands interspersed in the oral submucosa, there are three bilateral sets of major glands identified as parotid, sublingual, and submandibular, according to their location1,2. Pyramid-shaped epithelial cells, organized into flask-shaped sacs (acini) or demilunes that are surrounded by myoepithelial cells and a basement membrane, secrete the serous and mucous components of saliva1. The narrow luminal space of the acini drains into intercalated ducts, which unite into striated ducts until they finally join into a single excretory duct1. The main excretory duct of the SMG is called Wharton&#39;s duct (WD) and opens into the sublingual caruncle3,4. The SMG epithelial compartment therefore represents a highly arborized structure with manifold terminal endpoints, resembling a bundle of grapes1,5,6. The SMG interstitium is composed of blood and lymphatic vessels embedded in connective tissue7 containing parasympathetic nerves8 and extracellular matrix5. Normal human and rodent salivary glands also contain T cells, macrophages, and dendritic cells9, as well as plasma cells that secrete Immunoglobulin A (IgA) into the saliva9,10. Due to its multifaceted functions in health and disease, the SMG is a subject of interest for many fields of biological research, including dentistry4, immunology11, oncology12, physiology8, and cell biology3.
Imaging of dynamic cellular processes and interactions is a powerful tool in biological research13,14. The development of deep tissue imaging and innovations inmicroscopes based on nonlinear optics (NLO), which rely on scattering or absorption of multiple photons by the sample, has allowed to directly examine cellular processes in complex tissues13,15. Absorption of multiple photons involves delivery of the total excitation energy by low energy photons, which confines fluorophore excitation to the focal plane and thus allows deeper tissue penetration with reduced photodamage and noise from out of focus excitation13,15. This principle is employed by two-photon microscopy (2PM) and allows for imaging of fluorescent specimens in depths of up to 1 mm15,16. While commercially available 2PM setups have become user-friendly and reliable, the major challenge for intravital imaging is to carefully expose and stabilize the target organ of anesthetized mice, especially for imaging of time lapse series. Several methods for digital drift correction after data acquisition have been published17,18 and we recently developed &#34;VivoFollow&#34;, an automated correction system, which counteracts slow tissue drift in real time using a computerized stage19. However, it is still critical for high quality imaging to minimize tissue motion, especially fast movements caused by breathing or heartbeat19. Preparation and stabilization procedures have been published for multiple organs, including spinal cord20, liver21, skin22, lung23, and lymph node24. Furthermore, models for rat salivary gland imaging have been developed3,25 and further refined for high resolution intravital imaging of the murine SMG tailored to an inverted microscope setup26,27,28.
Here, we present a practical and adaptable protocol for intravital imaging of the murine SMG using upright nonlinear microscopy, which is commonly used for intravital imaging in the field of immunology. To this end, we modified a widely employed immobilization stage used for popliteal lymph node preparations.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
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		<tr>
			<td>Narketan 10 %&#160; (Ketamine) 20ml (100 mg/ml)</td>
			<td>Vetoquinol</td>
			<td>3605877535982</td>
			<td></td>
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		<tr>
			<td>Rompun 2% (Xylazine) 25 ml (20 mg/ml)</td>
			<td>Bayer</td>
			<td>680538150144</td>
			<td></td>
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			<td>Saline NaCl 0.9%</td>
			<td>B. Braun</td>
			<td>3535789</td>
			<td></td>
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			<td>Prequillan 1% (Acepromazine) 10 ml (10 mg/ml)</td>
			<td>Fatro</td>
			<td>6805671900029</td>
			<td></td>
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		<tr>
			<td>Electric shaver</td>
			<td>Wahl</td>
			<td>9818L</td>
			<td>or similar</td>
		</tr>
		<tr>
			<td>Hair removal cream</td>
			<td>Veet</td>
			<td>4002448090656</td>
			<td></td>
		</tr>
		<tr>
			<td>Durapore Surgical tape (2.5 cm x 9.1 m and 1.25 cm x 9.1 m)</td>
			<td>Durapore (3M)</td>
			<td>1538-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Durapore Surgical tape (2.5 cm x 9.1 m and 1.25 cm x 9.1 m)</td>
			<td>Durapore (3M)</td>
			<td>1538-0</td>
			<td></td>
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		<tr>
			<td>Super glue Ultra gel, instantaneous glue</td>
			<td>Pattex, Henkel</td>
			<td>4015000415040</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope cover glass slides 20 mm and 22 mm</td>
			<td>Menzel-Gl&#228;ser</td>
			<td>631-1343/ 631-1344</td>
			<td></td>
		</tr>
		<tr>
			<td>Grease for laboratories 60 g glisseal N</td>
			<td>Borer (VWR supplier)</td>
			<td>DECO514215.00-CA15</td>
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			<td>Surgical scissors</td>
			<td>Fine Science Tools (F.S.T )</td>
			<td>14090-09</td>
			<td>or similar</td>
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		<tr>
			<td>Fine Forceps</td>
			<td>Fine Science Tools (F.S.T )</td>
			<td>11252-20</td>
			<td>or similar</td>
		</tr>
		<tr>
			<td>Cotton swab</td>
			<td>Migros</td>
			<td>617027988254</td>
			<td>or similar</td>
		</tr>
		<tr>
			<td>Gauze Gazin 5 x 5 cm</td>
			<td>Lohmann and Rauscher</td>
			<td>18500</td>
			<td>or similar</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Leica</td>
			<td>MZ16</td>
			<td>or similar</td>
		</tr>
		<tr>
			<td>Texas Red dextran 70kDa</td>
			<td>&#160;Molecular Probes</td>
			<td>D1864</td>
			<td></td>
		</tr>
		<tr>
			<td>Cascade Blue dextran 10kDa</td>
			<td>invitrogen</td>
			<td>D1976</td>
			<td></td>
		</tr>
		<tr>
			<td>Two-photon system</td>
			<td>LaVision Biotec</td>
			<td>TrimScope I and II</td>
			<td>or similar</td>
		</tr>
		<tr>
			<td>XLUMPLANFL 20x/0.95 W objective</td>
			<td>Olympus</td>
			<td>n/a</td>
			<td>or other water immersion objective&#160;</td>
		</tr>
		<tr>
			<td>Digital thermometer</td>
			<td>Fluke</td>
			<td>95969077651</td>
			<td></td>
		</tr>
	</tbody>
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preparation of murine submandibular salivary gland for upright intravital microscopy

The submandibular salivary gland (SMG) is one of the three major salivary glands, and is of interest for many different fields of biological research, including cell biology, oncology, dentistry, and immunology. The SMG is an exocrine gland comprised of secretory epithelial cells, myofibroblasts, endothelial cells, nerves, and extracellular matrix. Dynamic cellular processes in the rat and mouse SMG have previously been imaged, mostly using inverted multi-photon microscope systems. Here, we describe a straightforward protocol for the surgical preparation and stabilization of the murine SMG in anesthetized mice for in vivo imaging with upright multi-photon microscope systems. We present representative intravital image sets of endogenous and adoptively transferred fluorescent cells, including the labeling of blood vessels or salivary ducts and second harmonic generation to visualize fibrillar collagen. In sum, our protocol allows for surgical preparation of mouse salivary glands in upright microscopy systems, which are commonly used for intravital imaging in the field of immunology.

This protocol allows imaging of almost the entire dorsal or ventral side of the SMG. The field of view typically also includes the sublingual salivary gland, which differs slightly from the SMG in cellular composition4. Both glands are encapsulated by fibrillar collagen and subdivided into lobes. Most 2PM systems can produce a label-free image of fibrillar collagen by measuring the 2nd harmonic signal, but usually fluorescent molecules are needed for vis...

Watch this Scientific Journal Video about Preparation of Murine Submandibular Salivary Gland for Upright Intravital Microscopy at JoVE.com

Preparation of Murine Submandibular Salivary Gland for Upright Intravital Microscopy

We describe a protocol to surgically expose and stabilize the murine submandibular salivary gland for intravital imaging using upright intravital microscopy. This protocol is easily adaptable to other exocrine glands of the head and neck region of mice and other small rodents.

The submandibular salivary gland (SMG) is one of the three major salivary glands, and is of interest for many different fields of biological research, ...

preparation-murine-submandibular-salivary-gland-for-upright

Research

JoVE Journal

Immunology and Infection

8.0K Views.  University of Bern. We describe a protocol to surgically expose and stabilize the murine submandibular salivary gland for intravital imaging using upright intravital microscopy. This protocol is easily adaptable to other exocrine glands of the head and neck region of mice and other small rodents. 

Video: Preparation of Murine Submandibular Salivary Gland for Upright Intravital Microscopy

Intravital Microscopy of the Inguinal Lymph Node

Lymph nodes (LN's), located throughout the body, are an integral component of the immune system. They serve as a site for induction of adaptive immune response and therefore, the development of effector cells. As such, LNs are key to fighting invading pathogens and maintaining health. The choice of LN to study is dictated by accessibility and the desired model; the inguinal lymph node is well situated and easily supports studies of biologically relevant models of skin and genital mucosal infection.
The inguinal LN, like all LNs, has an extensive microvascular network supplying it with blood. In general, this microvascular network includes the main feed arteriole of the LN that subsequently branches and feeds high endothelial venules (HEVs). HEVs are specialized for facilitating the trafficking of immune cells into the LN during both homeostasis and infection. How HEVs regulate trafficking into the LN under both of these circumstances is an area of intense exploration. The LN feed arteriole, has direct upstream influence on the HEVs and is the main supply of nutrients and cell rich blood into the LN. Furthermore, changes in the feed arteriole are implicated in facilitating induction of adaptive immune response. The LN microvasculature has obvious importance in maintaining an optimal blood supply to the LN and regulating immune cell influx into the LN, which are crucial elements in proper LN function and subsequently immune response. 
The ability to study the LN microvasculature in vivo is key to elucidating how the immune system and the microvasculature interact and influence one another within the LN. Here, we present a method for in vivo imaging of the inguinal lymph node. We focus on imaging of the microvasculature of the LN, paying particular attention to methods that ensure the study of healthy vessels, the ability to maintain imaging of viable vessels over a number of hours, and quantification of vessel magnitude. Methods for perfusion of the microvasculature with vasoactive drugs as well as the potential to trace and quantify cellular traffic are also presented. 
Intravital microscopy of the inguinal LN allows direct evaluation of microvascular functionality and real-time interface of the direct interface between immune cells, the LN, and the microcirculation. This technique potential to be combined with many immunological techniques and fluorescent cell labelling as well as manipulated to study vasculature of other LNs.

A technique for performing intravital microscopy of the inguinal lymph node (LN) is outlined. Such technique allows for real-time, in vivo study of the lymph node microvasculature and structure both during homeostasis and infection. This technique can be adapted to cell trafficking studies and to other lymph node sites.

Lymph nodes (LN's), located throughout the body, are an integral component of the immune system. They serve as a site for induction of adaptive immune ...

Tracking Neutrophil Intraluminal Crawling, Transendothelial Migration and Chemotaxis in Tissue by Intravital Video Microscopy

The recruitment of circulating leukocytes from blood stream to the inflamed tissue is a crucial and complex process of inflammation1,2. In the postcapillary venules of inflamed tissue, leukocytes initially tether and roll on the luminal surface of venular wall. Rolling leukocytes arrest on endothelium and undergo firm adhesion in response to chemokine or other chemoattractants on the venular surface. Many adherent leukocytes relocate from the initial site of adhesion to the junctional extravasation site in endothelium, a process termed intraluminal crawling3. Following crawling, leukocytes move across endothelium (transmigration) and migrate in extravascular tissue toward the source of chemoattractant (chemotaxis)4. Intravital microscopy is a powerful tool for visualizing leukocyte-endothelial cell interactions in vivo and revealing cellular and molecular mechanisms of leukocyte recruitment2,5. In this report, we provide a comprehensive description of using brightfield intravital microscopy to visualize and determine the detailed processes of neutrophil recruitment in mouse cremaster muscle in response to the gradient of a neutrophil chemoattractant. To induce neutrophil recruitment, a small piece of agarose gel (~1-mm3 size) containing neutrophil chemoattractant MIP-2 (CXCL2, a CXC chemokine) or WKYMVm (Trp-Lys-Tyr-Val-D-Met, a synthetic analog of bacterial peptide) is placed on the muscle tissue adjacent to the observed postcapillary venule. With time-lapsed video photography and computer software ImageJ, neutrophil intraluminal crawling on endothelium, neutrophil transendothelial migration and the migration and chemotaxis in tissue are visualized and tracked. This protocol allows reliable and quantitative analysis of many neutrophil recruitment parameters such as intraluminal crawling velocity, transmigration time, detachment time, migration velocity, chemotaxis velocity and chemotaxis index in tissue. We demonstrate that using this protocol, these neutrophil recruitment parameters can be stably determined and the single cell locomotion conveniently tracked in vivo.

We describe a protocol of brightfield intravital microscopy for measuring dynamic neutrophil-endothelial cell interactions during neutrophil recruitment in response to the source of a neutrophil chemoattractant in vivo. Neutrophil intraluminal crawling, transendothelial migration and chemotaxis in mouse cremaster muscle tissue are visualized with time-lapsed video photography and tracked with ImageJ.

The recruitment of circulating leukocytes from blood stream to the inflamed tissue is a crucial and complex process of inflammation1,2. In the ...

Intravital Imaging of the Mouse Thymus using 2-Photon Microscopy

Two-photon Microscopy (TPM) provides image acquisition in deep areas inside tissues and organs. In combination with the development of new stereotactic tools and surgical procedures, TPM becomes a powerful technique to identify "niches" inside organs and to document cellular "behaviors" in live animals. While intravital imaging provides information that best resembles the real cellular behavior inside the organ, it is both more laborious and technically demanding in terms of required equipment/procedures than alternative ex vivo imaging acquisition. Thus, we describe a surgical procedure and novel "stereotactic" organ holder that allows us to follow the movements of Foxp3+ cells within the thymus.
Foxp3 is the master regulator for the generation of regulatory T cells (Tregs). Moreover, these cells can be classified according to their origin: ie. thymus-differentiated Tregs are called "naturally-occurring Tregs" (nTregs), as opposed to peripherally-converted Tregs (pTregs). Although significant amount of research has been reported in the literature concerning the phenotype and physiology of these T cells, very little is known about their in vivo interactions with other cells. This deficiency may be due to the absence of techniques that would permit such observations. The protocol described in this paper provides a remedy for this situation.
Our protocol consists of using nude mice that lack an endogenous thymus since they have a punctual mutation in the DNA sequence that compromises the differentiation of some epithelial cells, including thymic epithelial cells. Nude mice were gamma-irradiated and reconstituted with bone marrows (BM) from Foxp3-KIgfp/gfp mice. After BM recovery (6 weeks), each animal received embryonic thymus transplantation inside the kidney capsule. After thymus acceptance (6 weeks), the animals were anesthetized; the kidney containing the transplanted thymus was exposed, fixed in our organ holder, and kept under physiological conditions for in vivo imaging by TPM. We have been using this approach to study the influence of drugs in the generation of regulatory T cells.

We have developed novel laboratory tools and protocols for intravital imaging acquisition of the thymus. Our technique should help in the identification of &#x201C;niches&#x201D; within the thymus where T cell development occurs.

Two-photon Microscopy (TPM) provides image acquisition in deep areas inside tissues and organs. In combination with the development of new stereotactic ...

Intravital Microscopy of the Spleen: Quantitative Analysis of Parasite Mobility and Blood Flow

The advent of intravital microscopy in experimental rodent malaria models has allowed major advances to the knowledge of parasite-host interactions 1,2. Thus, in vivo imaging of malaria parasites during pre-erythrocytic stages have revealed the active entrance of parasites into skin lymph nodes 3, the complete development of the parasite in the skin 4, and the formation of a hepatocyte-derived merosome to assure migration and release of merozoites into the blood stream 5. Moreover, the development of individual parasites in erythrocytes has been recently documented using 4D imaging and challenged our current view on protein export in malaria 6. Thus, intravital imaging has radically changed our view on key events in Plasmodium development. Unfortunately, studies of the dynamic passage of malaria parasites through the spleen, a major lymphoid organ exquisitely adapted to clear infected red blood cells are lacking due to technical constraints.
Using the murine model of malaria Plasmodium yoelii in Balb/c mice, we have implemented intravital imaging of the spleen and reported a differential remodeling of it and adherence of parasitized red blood cells (pRBCs) to barrier cells of fibroblastic origin in the red pulp during infection with the non-lethal parasite line P.yoelii 17X as opposed to infections with the P.yoelii 17XL lethal parasite line 7. To reach these conclusions, a specific methodology using ImageJ free software was developed to enable characterization of the fast three-dimensional movement of single-pRBCs. Results obtained with this protocol allow determining velocity, directionality and residence time of parasites in the spleen, all parameters addressing adherence in vivo. In addition, we report the methodology for blood flow quantification using intravital microscopy and the use of different colouring agents to gain insight into the complex microcirculatory structure of the spleen. 
Ethics statement
All the animal studies were performed at the animal facilities of University of Barcelona in accordance with guidelines and protocols approved by the Ethics Committee for Animal Experimentation of the University of Barcelona CEEA-UB (Protocol No DMAH: 5429). Female Balb/c mice of 6-8 weeks of age were obtained from Charles River Laboratories.

We show the method for performing intravital microscopy of the spleen using GFP transgenic malaria parasites and the quantification of parasite mobility and blood flow within this organ.

The advent of intravital microscopy in experimental rodent malaria models has allowed major advances to the knowledge of parasite-host interactions 1,2. ...

Saliva, Salivary Gland, and Hemolymph Collection from Ixodes scapularis Ticks

Ticks are found worldwide and afflict humans with many tick-borne illnesses. Ticks are vectors for pathogens that cause Lyme disease and tick-borne relapsing fever (Borrelia spp.), Rocky Mountain Spotted fever (Rickettsia rickettsii), ehrlichiosis (Ehrlichia chaffeensis and E. equi), anaplasmosis (Anaplasma phagocytophilum), encephalitis (tick-borne encephalitis virus), babesiosis (Babesia spp.), Colorado tick fever (Coltivirus), and tularemia (Francisella tularensis) 1-8. To be properly transmitted into the host these infectious agents differentially regulate gene expression, interact with tick proteins, and migrate through the tick 3,9-13. For example, the Lyme disease agent, Borrelia burgdorferi, adapts through differential gene expression to the feast and famine stages of the tick's enzootic cycle 14,15. Furthermore, as an Ixodes tick consumes a bloodmeal Borrelia replicate and migrate from the midgut into the hemocoel, where they travel to the salivary glands and are transmitted into the host with the expelled saliva 9,16-19.
As a tick feeds the host typically responds with a strong hemostatic and innate immune response 11,13,20-22. Despite these host responses, I. scapularis can feed for several days because tick saliva contains proteins that are immunomodulatory, lytic agents, anticoagulants, and fibrinolysins to aid the tick feeding 3,11,20,21,23. The immunomodulatory activities possessed by tick saliva or salivary gland extract (SGE) facilitate transmission, proliferation, and dissemination of numerous tick-borne pathogens 3,20,24-27. To further understand how tick-borne infectious agents cause disease it is essential to dissect actively feeding ticks and collect tick saliva. This video protocol demonstrates dissection techniques for the collection of hemolymph and the removal of salivary glands from actively feeding I. scapularis nymphs after 48 and 72 hours post mouse placement. We also demonstrate saliva collection from an adult female I. scapularis tick.

Saliva, Salivary Gland, and Hemolymph Collection from Ixodes scapularis Ticks

The collection of infected tick hemolymph, salivary glands, and saliva is important to study how tick-borne pathogens cause disease. In this protocol we demonstrate how to collect hemolymph and salivary glands from feeding Ixodes scapularis nymphs. We also demonstrate saliva collection from female I. scapularis adults.

Ticks are found worldwide and afflict humans with many tick-borne illnesses. Ticks are vectors for pathogens that cause Lyme disease and tick-borne ...

Highly Resolved Intravital Striped-illumination Microscopy of Germinal Centers

Monitoring cellular communication by intravital deep-tissue multi-photon microscopy is the key for understanding the fate of immune cells within thick tissue samples and organs in health and disease. By controlling the scanning pattern in multi-photon microscopy and applying appropriate numerical algorithms, we developed a striped-illumination approach, which enabled us to achieve 3-fold better axial resolution and improved signal-to-noise ratio, i.e. contrast, in more than 100 &#181;m tissue depth within highly scattering tissue of lymphoid organs as compared to standard multi-photon microscopy. The acquisition speed as well as photobleaching and photodamage effects were similar to standard photo-multiplier-based technique, whereas the imaging depth was slightly lower due to the use of field detectors. By using the striped-illumination approach, we are able to observe the dynamics of immune complex deposits on secondary follicular dendritic cells &#8211; on the level of a few protein molecules in germinal centers.

High-resolution intravital imaging with enhanced contrast up to 120 &#181;m depth in lymph nodes of adult mice is achieved by spatially modulating the excitation pattern of a multi-focal two-photon microscope. In 100 &#181;m depth we measured resolutions of 487 nm (lateral) and 551 nm (axial), thus circumventing scattering and diffraction limits.

Monitoring cellular communication by intravital deep-tissue multi-photon microscopy is the key for understanding the fate of immune cells within thick ...

Intravital Microscopy Imaging of the Liver following Leishmania Infection: An Assessment of Hepatic Hemodynamics

Intravital microscopy (IVM) is a powerful optical imaging technique that has made possible the visualization, monitoring and quantification of various biological events in real time and in live animals. This technology has greatly advanced our understanding of physiological processes and pathogen-mediated phenomena in specific organs.
In this study, IVM is applied to the mouse liver and protocols are designed to image in vivo the circulatory system of the liver and measure red blood cell (RBC) velocity in individual hepatic vessels. To visualize the different vessel subtypes that characterize the hepatic organ and perform blood flow speed measurements, C57Bl/6 mice are intravenously injected with a fluorescent plasma reagent that labels the liver-associated vasculature. IVM enables in vivo, real time, measurement of RBC velocity in a specific vessel of interest. Establishing this methodology will make it possible to investigate liver hemodynamics under physiological and pathological conditions. Ultimately, this imaging-based methodology will be important for studying the influence of L. donovani infection&#160;on hepatic hemodynamics.
This method can be applied to other infectious models and mouse organs and might be further extended to pre-clinical testing of a drug&#8217;s effect on inflammation by quantifying its effect on blood flow.

Intravital Microscopy Imaging of the Liver following Leishmania Infection: An Assessment of Hepatic Hemodynamics

This article reports on a detailed method for the dynamic measurement and quantification of blood flow velocity within individual blood vessels of the mouse liver vasculature using intravital microscopy imaging in combination with a specific methodology for image acquisition and analysis.

Intravital microscopy (IVM) is a powerful optical imaging technique that has made possible the visualization, monitoring and quantification of various ...

Long Term Intravital Multiphoton Microscopy Imaging of Immune Cells in Healthy and Diseased Liver Using CXCR6.Gfp Reporter Mice

Liver inflammation as a response to injury is a highly dynamic process involving the infiltration of distinct subtypes of leukocytes including monocytes, neutrophils, T cell subsets, B cells, natural killer (NK) and NKT cells. Intravital microscopy of the liver for monitoring immune cell migration is particularly challenging due to the high requirements regarding sample preparation and fixation, optical resolution and long-term animal survival. Yet, the dynamics of inflammatory processes as well as cellular interaction studies could provide critical information to better understand the initiation, progression and regression of inflammatory liver disease. Therefore, a highly sensitive and reliable method was established to study migration and cell-cell-interactions of different immune cells in mouse liver over long periods (about 6 hr) by intravital two-photon laser scanning microscopy (TPLSM) in combination with intensive care monitoring.
The method provided includes a gentle preparation and stable fixation of the liver with minimal perturbation of the organ; long term intravital imaging using multicolor multiphoton microscopy with virtually no photobleaching or phototoxic effects over a time period of up to 6 hr, allowing tracking of specific leukocyte subsets; and stable imaging conditions due to extensive monitoring of mouse vital parameters and stabilization of circulation, temperature and gas exchange.
To investigate lymphocyte migration upon liver inflammation CXCR6.gfp knock-in mice were subjected to intravital liver imaging under baseline conditions and after acute and chronic liver damage induced by intraperitoneal injection(s) of carbon tetrachloride (CCl4).
CXCR6 is a chemokine receptor expressed on lymphocytes, mainly on Natural Killer T (NKT)-, Natural Killer (NK)- and subsets of T lymphocytes such as CD4 T cells but also mucosal associated invariant (MAIT) T cells1. Following the migratory pattern and positioning of CXCR6.gfp+ immune cells allowed a detailed insight into their altered behavior upon liver injury and therefore their potential involvement in disease progression.

Stable intravital high-resolution imaging of immune cells in the liver is challenging. Here we provide a highly sensitive and reliable method to study migration and cell-cell-interactions of immune cells in mouse liver over long periods (about 6 hours) by intravital multiphoton laser scanning microscopy in combination with intensive care monitoring.

Liver inflammation as a response to injury is a highly dynamic process involving the infiltration of distinct subtypes of leukocytes including monocytes, ...

Intravital Microscopy of Leukocyte-endothelial and Platelet-leukocyte Interactions in Mesenterial Veins in Mice

Intravital microscopy is a method that can be used to investigate different processes in different regions and vessels in living animals. In this protocol, we describe intravital microscopy of mesentery veins. This can be performed in a short period of time with reproducible results showing leukocyte-endothelial interactions in vivo. We describe an inflammatory setting after LPS challenge of the endothelium. But in this model one can apply many different types of inflammatory conditions, like bacterial, chemical or biological and investigate the administration of drugs and their direct effects on the living animal and its impact on leukocyte recruitment. This protocol has been applied successfully to a number of different treatments of mice and their effects on inflammatory response in vessels. Herein, we describe the visualization of leukocytes and platelets by fluorescently labeling these with rhodamine 6G. Additionally, any specific imaging can be performed using targeted fluorescently labeled molecules.

This simplified application of intravital microscopy of mesentery veins in mice can be used in different models of inflammation to observe leukocyte-endothelial and platelet-leukocyte interactions.

Intravital microscopy is a method that can be used to investigate different processes in different regions and vessels in living animals. In this ...

A Method for the Measurement of Salivary Gland Function in Mice

Patients with Sj&#246;gren&#39;s syndrome, an autoimmune disease affecting the exocrine glands, develop salivary gland inflammation and have reduced saliva production. Similarly, saliva production is severely compromised in patients receiving radiation treatment for head and neck cancers. Rodent models, developed to mimic these clinical conditions, facilitate an understanding of the disease pathogenesis and allow for the development of new therapeutic strategies. Therefore, the ability to accurately, reproducibly, and repeatedly measure salivary gland function in animal models is critical. Building on procedures previously described in the literature, a method was developed that meets these criteria and was used to evaluate salivary gland function in mice. An additional advantage of this new method is that it is easily mastered, and has little inter-operator variation. Salivary gland function is evaluated as the amount (weight or volume) or rate (mL/min) of saliva produced in response to pilocarpine stimulation. The collected saliva is a good source for the analyses of protein content, immunoglobulin concentrations, and other biomolecules.

Salivary gland hypofunction is a frequent consequence of autoimmune disease and radiation therapy. Reproducible evaluation of salivary gland function in mouse models of these diseases is a technical challenge. Here, a simple method for accurate and reproducible measurement of saliva production in mice is described.

Patients with Sj&#246;gren&#39;s syndrome, an autoimmune disease affecting the exocrine glands, develop salivary gland inflammation and have reduced ...