This research was supported by NIH-CA100324, Einstein National Cancer Institute's cancer center support grant P30CA013330, R01CA172451 to JWP and the Integrated Imaging Program. This technology was developed in the Gruss-Lipper Biophotonics Center and the Integrated Imaging Program at the Albert Einstein College of Medicine. We acknowledge the support of these Centers in this work. The authors thank Mike Rottenkolber, Ricardo Ibagon and Anthony Leggiadro of the Einstein machine shop for their skilled and timely craftsmanship, the laboratory of Matthew Krummel for generously sharing their window design drawings, Kevin Elicieri and Jeremy Bredfeldt for their expertise in microscopy and their amplifier recommendations and Allison Harney and Bojana Gligorijevic for informative discussions.

The authors have nothing to disclose.

High resolution in vivo optical imaging combined with fluorescently labelled functional tags such as proteins and antibodies has dramatically increased our understanding of the metastatic cascade. It has enabled direct visualization and quantification of single-cell and sub-cellular parameters in tumor cells, host cells and their microenvironment. This imaging within the primary tumor has led, for example, to the discovery of discrete microenvironments that are supportive of either growth invasion or disseminati...

High resolution intravital optical imaging has proven to be crucial to understanding many biological processes, allowing single-cell and sub-cellular parameters to be measured and quantified. In cancer research, intravital imaging of tumor and stromal cells has led to the discovery of many microenvironmental interactions 6-11 that are only present in the intact animal.
Discoveries about microenvironments associated with intravasation and dissemination of tumor cells in breast cancer using single cell resolution optical imaging in vivo has even led to novel markers for prognosis and response to treatment in breast cancer patients 12-16. The best imaging technologies available for viewing deep within intact internal vital organs are the clinical modalities (MRI, PET, CT) which offer excellent views of the entire organ and can reveal pathologies even before they produce clinical symptoms. They are unable, however, to reveal the earliest stages of metastasis and the cellular mechanisms driving tumor progression due to their lack of single cell resolution. By the time lung metastases are visible in these modalities, they are well established and proliferating. Given the estimate that 90% of disseminated tumor cells that arrive to the lung either do not survive 17 or initially remain dormant 18, and the observation that they arrive much earlier than previously expected 19, imaging the earliest steps of arrival and survival becomes crucial to understanding the process of metastatic seeding and recurrence of tumor growth at distant sites.
Performing these observations in the lung has proven extremely difficult however; the vast majority of imaging studies have utilized ex vivo or explant preparations 20-23, which only give a view into the lung at single time points. While these preparations do provide useful information, they do not give a complete understanding of the interactions, cause and effect relationships, and dynamics that occur between the various components of the microenvironment. The lack of a proper circulatory system (and concomitant imbalance of homeostasis) and the disconnection from the rest of the body&#39;s immune system makes it desirous to validate the conclusions that these preparations generate in intact tissue in vivo.
Many groups have performed intravital imaging of the intact lung 2,4,5,24-33 with Wearn and German being the first to surgically expose the pleural layer 24 and Terry the first to utilize an implantable imaging window 25.
High resolution imaging in the lung is greatly hindered by the lung&#39;s constant motion and several techniques have been developed to overcome this limitation. Wagner and Filley 27 studied the natural motion of the canine lung and designed their surgical protocol to locate their implanted window over a relatively stationary region while Wagner utilized vacuum in his window surgical preparation to immobilize the tissue 28. Since that time, a variety of techniques have been utilized to image the lung including: bronchus clamping, sequential apnea and gated imaging, oversampled acquisition, gluing of the lung lobe and vacuum 34. Each of these has its advantages and disadvantages and no one technique has emerged as superior to another 34. For example, bronchus clamping and sequential apnea alter the normal exchange of gases in the lung and may cause atelectasis. Gated imaging and oversampled acquisition do not suffer from these disadvantages but require high-speed or specialized imaging equipment not widely accessible. Finally both gluing of the lung and the vacuum technique avoid both of the above mentioned drawbacks, but may exhibit shear force induced injury if care is not taken. In recent years, the vacuum window has been miniaturized and adapted for use in mice using confocal and multiphoton microscopy 4,5,33 and excellent high-resolution imaging has been attained 2. Table 1 summarizes this rich history and highlights those papers which describe novel advancements in the use of intravital lung imaging windows.
This protocol describes the use of extended time-lapse multiphoton intravital microscopy to image metastasis in the live, intact lung with the highest subcellular resolution possible. Images are acquired for up to 12 hr using a multiphoton microscope equipped with a high numerical aperture objective lens and multiple photomultiplier tube (PMT) detectors. Transgenic mouse models are utilized to fluorescently label native macrophages along with fluorescent high molecular weight dextran and fluorescent protein transfected tumor cells (to label the vasculature and tumor cells respectively). While this choice of fluorescently labeled cells enables visualization of tumor cell-endothelial cell-macrophage interactions and dynamics, this protocol will work for any strain of fluorescent or non-fluorescent mouse. After acquisition, residual drift motion (if any) is eliminated using a Fiji plugin 35,36 and custom macros time average the vascular channel to eliminate flashing caused by unlabeled circulating blood cells.
While this protocol focuses on imaging metastasis, the techniques are applicable to many other biological processes observable with high-resolution single-cell imaging in the lung.

<table><tbody><tr><td>Nickel-Plated Brass Vacuum Regulator 1/8 NPT Female, w/ Gauge, 0 - 20&quot; Hg Vacuum</td><td>McMaster Carr</td><td>4172K12&amp;nbsp;</td><td>Vacuum Regulator</td></tr><tr><td>Brass Barbed Hose Fitting Adapter for 1/4&quot; Hose ID X 1/8&quot; NPTF Male Pipe</td><td>McMaster Carr</td><td>5346K13</td><td>Vacuum Regulator Hose Adapter</td></tr><tr><td>Pyrex Brand Filtering Flasks with Tubulation; Neck tooled for rubber stopper No. 4; Capacity: 50 ml</td><td>Corning Life Sciences Glass</td><td>5360-50</td><td>Vacuum Flask</td></tr><tr><td>Round Glass Coverslips Thickness #1.5, 0.16 - 0.19 mm 10 mm dia.&amp;nbsp;</td><td>Ted Pella, Inc.</td><td>260368</td><td>Cover slips</td></tr><tr><td>Exel International Disposable Safelet I.V. Catheters; 22 g x 1 in.&amp;nbsp;</td><td>Exel International</td><td>26746</td><td>Tracheal Catheter</td></tr><tr><td>PERMA-HAND Black Braided Silk Sutures, ETHICON LIGAPAK Dispensing Reel Size 2-0</td><td>VWR</td><td>95056-992</td><td>String</td></tr><tr><td>Liquid Super Glue, Clear, 0.14 oz</td><td>Hendel Corp.</td><td>LOC1647358</td><td>Cyano-acrylate Glue</td></tr><tr><td>Tetramethylrhodamine isothiocyanate&amp;ndash;Dextran</td><td>Sigma-Aldrich</td><td>T1287-500MG</td><td>155 kD Dextran</td></tr><tr><td>Laboratory Clear Tygon PVC Tubing, 1/16&quot; ID, 1/8&quot; OD, 1/32&quot; Wall Thickness, 25 ft. Length</td><td>McMaster Carr</td><td>5155T12</td><td>Thin Tubing &amp;amp; Tubing for Luer</td></tr><tr><td>Crack-Resistant Polyethylene Tubing, 1/8&quot; ID, 1/4&quot; OD, 1/16&quot; Wall Thickness, White, 50 ft. Length&amp;nbsp;</td><td>McMaster Carr</td><td>5181K24&amp;nbsp;</td><td>Thick Tubing</td></tr><tr><td>Depillatory Lotion</td><td>Nair</td><td>-</td><td></td></tr><tr><td>Micro Medical Tubing 95 Durometer LDPE</td><td>Scientific Commodities Inc.</td><td>BB31695-PE/1</td><td>Tubing for tail vein catheter</td></tr><tr><td>30 G x 1 in. BD PrecisionGlide Needle</td><td>BD</td><td>305128</td><td>Needles for tail vein catheter</td></tr><tr><td>Puritan Nonsterile Cotton-Tipped Swabs&amp;nbsp;</td><td>Fisher Scientific</td><td>867WCNOGLUE</td><td></td></tr><tr><td>Clear Polycarbonate Barbed Tube Fitting, Reducing Straight for 3/32&quot; x 1/16&quot; Tube ID</td><td>McMaster Carr</td><td>5117k51</td><td>Connectors between tubes</td></tr><tr><td>One-Hole Rubber Stoppers</td><td>Fisher Scientific</td><td>14-135F</td><td>Stopper for Vacuum Flask</td></tr><tr><td>SHARP Precision Barrier Tips, For P-100, 100 &amp;micro;l</td><td>Denville Scientific Inc.</td><td>P1125</td><td>Pipette Tip</td></tr><tr><td>Laboratory tape</td><td>Fisher Scientific</td><td>159015R</td><td></td></tr><tr><td>Puralube</td><td>Henry Schein Animal Health</td><td>008897</td><td>Opthalmic Ointment</td></tr><tr><td>Gemini Cautery Kit</td><td>Harvard Apparatus</td><td>726067</td><td>Cautery Pen</td></tr><tr><td>Graefe Micro Dissecting Forceps; Serrated; Slight Curve; 0.8 mm Tip Width; 4&quot; Length</td><td>Roboz Surgical</td><td>RS-5135&amp;nbsp;</td><td>Forceps</td></tr><tr><td>Extra Fine Micro Dissecting Scissors 4&quot; Straight Sharp/Sharp 24 mm</td><td>Roboz Surgical</td><td>RS-5912</td><td>Sharp Scissors</td></tr><tr><td>Micro Dissecting Scissors 4&quot; Straight Blunt/Blunt</td><td>Roboz Surgical</td><td>RS-5980</td><td>Blunt Scissors</td></tr><tr><td>Wipes</td><td>Fisher Scientific</td><td>06-666-A&amp;nbsp;</td><td>Harness</td></tr><tr><td>PhysioSuite System</td><td>Kent Scientific</td><td>PhysioSuite</td><td>Vitals Monitor</td></tr><tr><td>1 ml Syringe, Tuberculin Slip Tip</td><td>BD</td><td>309659</td><td>Syringe</td></tr><tr><td>Cyano acrylate</td><td>Staples</td><td>LOC1647358</td><td>Cover Slip Adhesive</td></tr><tr><td>Petroleum Jelly</td><td>Fisher Scientific</td><td>19-086291</td><td>Water Barrier</td></tr><tr><td>Adapter Luer Cannulla 1.5 - 2.2 mm</td><td>Harvard Apparatus</td><td>734118</td><td>Catheter Connector</td></tr><tr><td>PhysioSuite MouseSTAT pulse oximeter</td><td>Kent Scientific</td><td></td><td>Pulse Oximeter</td></tr><tr><td>Isoethesia (isoflurane)</td><td>Henry Schein Animal Health</td><td>50033</td><td>250 ml</td></tr><tr><td>Oxygen</td><td>TechAir</td><td>OX TM</td><td></td></tr><tr><td>1x PBS</td><td>Life Technologies</td><td>10010-023</td><td></td></tr><tr><td>PVC Ball Valve, Push to Connect, 1/4 In</td><td>Grainger</td><td>3CGJ7</td><td>Vacuum Valve</td></tr><tr><td>Small Animal Ventilator</td><td>Harvard Apparatus</td><td>683</td><td>Alternative is available from Kent Scientific: MouseVent</td></tr><tr><td>OptiMEM Reduced Serum Medium</td><td>ThermoFisher Scientific</td><td>31985062&amp;nbsp;</td><td></td></tr><tr><td>Lipofectamine 2000 Transfection Reagent</td><td>ThermoFisher Scientific</td><td>11668019</td><td></td></tr><tr><td>MacBlue Tg(Csf1r*-GAL4/VP16,UAS-ECFP)1Hume/J Mice</td><td>Jackson Laboratory</td><td>026051&amp;nbsp;</td><td></td></tr><tr><td>Multiphoton Microscope</td><td>Olympus</td><td>Fluoview FV1000</td><td>Alternative to custom built scope</td></tr><tr><td>Environmental Enclosure</td><td>Precision Plastics</td><td>Chamber for FV1000</td><td>Alternative to custom built enclosure</td></tr><tr><td>Phosphate Buffered Saline</td><td>ThermoFisher Scientific</td><td>14190136</td><td></td></tr><tr><td>Laser Power Meter</td><td>Coherent</td><td>FieldMaxIITOP</td><td></td></tr><tr><td>Laser Power Meter Head</td><td>Coherent</td><td>PM10</td><td></td></tr><tr><td>pcDNA3-Clover Fluorescent Protein Vector</td><td>Addgene</td><td>40259</td><td></td></tr><tr><td>G418 Sulfate Selective Antibiotic</td><td>ThermoFisher Scientific</td><td>10131027</td><td></td></tr><tr><td>MoFlo Fluorescent-Activate Cell Sorter&amp;nbsp;</td><td>Beckman Coulter</td><td>XDP</td><td></td></tr><tr><td>Trypsin EDTA 1x</td><td>Corning</td><td>25-052-Cl</td><td></td></tr><tr><td>40 &amp;micro;m Mesh</td><td>Falcon</td><td>352235</td><td></td></tr><tr><td>96 Well Plate</td><td>Costar</td><td>3599</td><td></td></tr><tr><td>60 mm Culture Dish</td><td>Corning</td><td>430196</td><td></td></tr><tr><td>10 cm Culture Dish</td><td>Corning</td><td>353003</td><td></td></tr><tr><td>Bovine Serum Albumin</td><td>Sigma-Aldrich</td><td>A4503</td><td></td></tr><tr><td>Dulbecco&#039;s Phosphate Buffered Saline 1x</td><td>Corning</td><td>21-031-CV</td><td></td></tr><tr><td>C57BL/6J Mouse</td><td>Jackson Laboratory</td><td>000664&amp;nbsp;</td><td></td></tr><tr><td>Kim Wipes</td><td>Fisher Scientific</td><td>06-666-A&amp;nbsp;</td><td></td></tr></tbody></table>

long-term high-resolution intravital microscopy in the lung with a vacuum stabilized imaging window

Metastasis to secondary sites such as the lung, liver and bone is a traumatic event with a mortality rate of approximately 90% 1. Of these sites, the lung is the most difficult to assess using intravital optical imaging due to its enclosed position within the body, delicate nature and vital role in sustaining proper physiology. While clinical modalities (positron emission tomography (PET), magnetic resonance imaging (MRI) and computed tomography (CT)) are capable of providing noninvasive images of this tissue, they lack the resolution necessary to visualize the earliest seeding events, with a single pixel consisting of nearly a thousand cells. Current models of metastatic lung seeding postulate that events just after a tumor cell&#39;s arrival are deterministic for survival and subsequent growth. This means that real-time intravital imaging tools with single cell resolution 2 are required in order to define the phenotypes of the seeding cells and test these models. While high resolution optical imaging of the lung has been performed using various ex vivo preparations, these experiments are typically single time-point assays and are susceptible to artifacts and possible erroneous conclusions due to the dramatically altered environment (temperature, profusion, cytokines, etc.) resulting from removal from the chest cavity and circulatory system 3. Recent work has shown that time-lapse intravital optical imaging of the intact lung is possible using a vacuum stabilized imaging window 2,4,5 however, typical imaging times have been limited to approximately 6 hr. Here we describe a protocol for performing long-term intravital time-lapse imaging of the lung utilizing such a window over a period of 12 hr. The time-lapse image sequences obtained using this method enable visualization and quantitation of cell-cell interactions, membrane dynamics and vascular perfusion in the lung. We further describe an image processing technique that gives an unprecedentedly clear view of the lung microvasculature.

To demonstrate the type of results that can be achieved with this method, we injected E0771-LG tumor cells labeled with the fluorescent protein Clover into the tail vein of MacBlue mice 44 at varying time points before surgery. After surgery, 155 kD rhodamine labeled dextran was injected IV to mark the vasculature and time-lapse imaging was performed.
When imaging mice 24 hr post injection, single cells are visible in...

Watch this Scientific Journal Video about Long-term High-Resolution Intravital Microscopy in the Lung with a Vacuum Stabilized Imaging Window at JoVE.com

Long-term High-Resolution Intravital Microscopy in the Lung with a Vacuum Stabilized Imaging Window

This protocol describes the use of multiphoton microscopy to perform long-term high-resolution, single cell imaging of the intact lung in real time using a vacuum stabilized imaging window.

Metastasis to secondary sites such as the lung, liver and bone is a traumatic event with a mortality rate of approximately 90% 1. Of these sites, the lung ...

long-term-high-resolution-intravital-microscopy-lung-with-vacuum

Research

JoVE Journal

Cancer Research

13.1K Views.  Albert Einstein College of Medicine. This protocol describes the use of multiphoton microscopy to perform long-term high-resolution, single cell imaging of the intact lung in real time using a vacuum stabilized imaging window. 

Video: Long-term High-Resolution Intravital Microscopy in the Lung with a Vacuum Stabilized Imaging Window

Ex Vivo Imaging of Resident CD8 T Lymphocytes in Human Lung Tumor Slices Using Confocal Microscopy

CD8 T cell are key players in the fight against cancer. In order for CD8 T cells to kill tumor cells they need to enter into the tumor, migrate within the tumor microenvironment and respond adequately to tumor antigens. The recent development of improved imaging approaches, such as 2-photon microscopy, and the use of powerful mouse tumor models have shed light on some of the mechanisms that regulate anti-tumor T cell activities. Whereas such systems have provided valuable insights, they do not always predict human responses. In human, our knowledge in the field mainly comes from a description of fixed tumor samples from human patients, as well as in vitro studies. However, in vitro models lack the complex three-dimensional tumor milieu and, therefore, are incomplete approximations of in vivo T cell activities. Fresh slices made from explanted tissue represent a complex multi-cellular tumor environment that can act as an important link between co-cultured studies and animal models. Originally set up in murine lymph nodes1 and previously described in a JoVE article2, this approach has now been transposed to human tumors to examine the dynamics of both plated3&#160;as well as resident&#160;T cells4.
Here, a protocol for the preparation of human lung tumor slices, immunostaining of resident CD8 T and tumor cells, and tracking of CD8 T lymphocytes within the tumor microenvironment using confocal microscopy is described. This system is uniquely placed to screen for novel immunotherapy agents favoring T cell migration in tumors.

Ex Vivo Imaging of Resident CD8 T Lymphocytes in Human Lung Tumor Slices Using Confocal Microscopy

This protocol describes a method to image resident tumor-infiltrating CD8 T cells labeled with fluorescently coupled antibodies within human lung tumor slices. This technique permits real-time analyses of CD8 T cell migration using confocal microscopy.

CD8 T cell are key players in the fight against cancer. In order for CD8 T cells to kill tumor cells they need to enter into the tumor, migrate within the ...

Direct Observation of Phagocytosis and NET-formation by Neutrophils in Infected Lungs using 2-photon Microscopy

After the gastrointestinal tract, the lung is the second largest surface for interaction between the vertebrate body and the 
environment. Here, an effective gas exchange must be maintained, while at the same time avoiding infection by the multiple pathogens that are inhaled 
during normal breathing. To achieve this, a superb set of defense strategies combining humoral and cellular immune mechanisms exists. One of the most 
effective measures for acute defense of the lung is the recruitment of neutrophils, which either phagocytose the inhaled pathogens or kill them by 
releasing cytotoxic chemicals. A recent addition to the arsenal of neutrophils is their explosive release of extracellular DNA-NETs by which bacteria 
or fungi can be caught or inactivated even after the NET releasing cells have died. We present here a method that allows one to directly observe neutrophils, 
migrating within a recently infected lung, phagocytosing fungal pathogens as well as visualize the extensive NETs that they have produced throughout the 
infected tissue. The method describes the preparation of thick viable lung slices 7 hours after intratracheal infection of mice with conidia of the mold 
Aspergillus fumigatus and their examination by multicolor time-lapse 2-photon microscopy. This approach allows one to directly investigate antifungal 
defense in native lung tissue and thus opens a new avenue for the detailed investigation of pulmonary immunity.

We show, how to use 2-photon microscopy for the observation of the dynamics of neutrophil granulocytes in infected lungs while they phagocytose pathogens or produce neutrophil extracellular traps (NETs).

After the gastrointestinal tract, the lung is the second largest surface for interaction between the vertebrate body and the 
environment. Here, an ...

Immunology and Infection

Longitudinal Intravital Imaging Through Clear Silicone Windows

Intravital microscopy (IVM) enables visualization of cell movement, division, and death at single-cell resolution. IVM through surgically inserted imaging windows is particularly powerful because it allows longitudinal observation of the same tissue over days to weeks. Typical imaging windows comprise a glass coverslip in a biocompatible metal frame sutured to the mouse&#8217;s skin. These windows can interfere with the free movement of the mice, elicit a strong inflammatory response, and fail due to broken glass or torn sutures, any of which may necessitate euthanasia. To address these issues, windows for long-term abdominal organ and mammary gland imaging&#160;were developed from a thin film of polydimethylsiloxane (PDMS), an optically clear silicone polymer previously used for cranial imaging windows. These windows can be glued directly to the tissues, reducing the time needed for insertion. PDMS is flexible, contributing to its durability in mice over time&#8212;up to 35 days have been tested. Longitudinal imaging is imaging of the same tissue region during separate sessions. A stainless-steel grid was embedded within the windows to localize the same region, allowing the visualization of dynamic processes (like mammary gland involution) at the same locations, days apart. This silicone window also allowed monitoring of single disseminated cancer cells developing into micro-metastases over time. The silicone windows used in this study are simpler to insert than metal-framed glass windows and cause limited inflammation of the imaged tissues. Moreover, embedded grids allow for straightforward tracking of the same tissue region in repeated imaging sessions.

An approach is here presented for long-term intravital imaging using optically clear, silicone windows that can be glued directly to the tissue/organ of interest and the skin.&#160;These windows are cheaper and more versatile than others currently used in the field, and the surgical insertion causes limited inflammation and distress to the animals.

Intravital microscopy (IVM) enables visualization of cell movement, division, and death at single-cell resolution. IVM through surgically inserted imaging ...

A Permanent Window for Investigating Cancer Metastasis to the Lung

Metastasis, accounting for ~90% of cancer-related mortality, involves the systemic spread of cancer cells from primary tumors to secondary sites such as the bone, brain, and lung. Although extensively studied, the mechanistic details of this process remain poorly understood. While common imaging modalities, including computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI), offer varying degrees of gross visualization, each lacks the temporal and spatial resolution necessary to detect the dynamics of individual tumor cells. To address this, numerous techniques have been described for intravital imaging of common metastatic sites. Of these sites, the lung has proven especially challenging to access for intravital imaging owing to its delicacy and critical role in sustaining life. Although several approaches have previously been described for single-cell intravital imaging of the intact lung, all involve highly invasive and terminal procedures, limiting the maximum possible imaging duration to 6-12 h. Described here is an improved technique for the permanent implantation of a minimally invasive thoracic optical Window for High-Resolution Imaging of the Lung (WHRIL). Combined with an adapted approach to microcartography, the innovative optical window facilitates serial intravital imaging of the intact lung at single-cell resolution across multiple imaging sessions and spanning multiple weeks. Given the unprecedented duration of time over which imaging data can be gathered, the WHRIL can facilitate the accelerated discovery of the dynamic mechanisms underlying metastatic progression and numerous additional biologic processes within the lung.

Here, we present a protocol for the surgical implantation of a permanently indwelling optical window for the murine thorax, which enables high-resolution, intravital imaging of the lung. The permanence of the window makes it well-suited to the study of dynamic cellular processes in the lung, especially those that are slowly evolving, such as metastatic progression of disseminated tumor cells.

Metastasis, accounting for ~90% of cancer-related mortality, involves the systemic spread of cancer cells from primary tumors to secondary sites such as ...

Intravital Microscopy of Tumor-associated Vasculature Using Advanced Dorsal Skinfold Window Chambers on Transgenic Fluorescent Mice

Tumor and tumor vessel development, as well as tumor response to therapeutics, are highly dynamic biological processes. Histology provides static information and is often not sufficient for a correct interpretation. Intravital evaluation, in which a process is followed in time, provides extra and often unexpected information. With the creation of transgenic animals expressing cell-specific markers and live cell tracers, improvements to imaging equipment, and the development of several imaging chambers, intravital microscopy has become an important tool to better understand biological processes. This paper describes an experimental design for the investigation of tumor vessel development and of therapeutic effects in a spatial and temporal manner. Using this setup, the stage of vessel development, tip cell and lumen formation, blood flow, extravasation, an established vascular bed, and vascular destruction can be visualized and followed. Furthermore, therapeutic effects, intratumoral fate, and the localization of chemotherapeutic compounds can also be followed.

This protocol describes the intravital imaging of transgenic mice expressing cell-specific fluorescent markers. Intravital imaging provides a non-invasive method for high-resolution observations in living animals using implantable windows through which the microscopic visualization of processes is possible. This method is especially useful to study longitudinal processes.

Tumor and tumor vessel development, as well as tumor response to therapeutics, are highly dynamic biological processes. Histology provides static ...

Medicine

Advanced Imaging of Lung Homing Human Lymphocytes in an Experimental In Vivo Model of Allergic Inflammation Based on Light-sheet Microscopy

Overwhelming tissue accumulation of highly activated immune cells represents a hallmark of various chronic inflammatory diseases and emerged as an attractive therapeutic target in the clinical management of affected patients. In order to further optimize strategies aiming at therapeutic regulation of pathologically imbalanced tissue infiltration of pro-inflammatory immune cells, it will be of particular importance to achieve improved insights into disease- and organ-specific homing properties of peripheral lymphocytes. The here described experimental protocol allows to monitor lung accumulation of fluorescently labeled and adoptively transferred human lymphocytes in the context of papain-induced pulmonary inflammation. In contrast to standard in vitro assays frequently used for the analysis of immune cell migration and chemotaxis, the now introduced in vivo setting takes into account lung-specific aspects of tissue organization and the influence of the complex inflammatory scenario taking place in the living murine organism. Moreover, three-dimensional cross-sectional light-sheet fluorescence microscopic imaging does not only provide quantitative data on infiltrating immune cells, but also depicts the pattern of immune cell localization within the inflamed lung. Overall, we are able to introduce an innovative technique of high value for immunological research in the field of chronic inflammatory lung diseases, which can be easily applied by following the provided step-by-step protocol.

The here introduced protocol allows characterization of the lung homing capacity of primary human lymphocytes under in vivo inflammatory conditions. Pulmonary infiltration of adoptively transferred human immune cells in a mouse model of allergic inflammation can be imaged and quantified by light-sheet fluorescence microscopy of chemically cleared lung tissue.

Overwhelming tissue accumulation of highly activated immune cells represents a hallmark of various chronic inflammatory diseases and emerged as an ...

Intravital Widefield Fluorescence Microscopy of Pulmonary Microcirculation in Experimental Acute Lung Injury Using a Vacuum-Stabilized Imaging System

Intravital imaging of leukocyte-endothelial interactions offers valuable insights into immune-mediated disease in live animals. The study of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) and other respiratory pathologies in vivo is difficult due to the limited accessibility and inherent motion artifacts of the lungs. Nonetheless, various approaches have been developed to overcome these challenges. This protocol describes a method for intravital fluorescence microscopy to study real-time leukocyte-endothelial interactions in the pulmonary microcirculation in an experimental model of ALI. An in vivo lung imaging system and 3-D printed intravital microscopy platform are used to secure the anesthetized mouse and stabilize the lung while minimizing confounding lung injury. Following preparation, widefield fluorescence microscopy is used to study leukocyte adhesion, leukocyte rolling, and capillary function. While the protocol presented here focuses on imaging in an acute model of inflammatory lung disease, it may also be adapted to study other pathological and physiological processes in the lung.

Intravital fluorescence microscopy can be utilized to study leukocyte-endothelial interactions and capillary perfusion in real-time. This protocol describes methods to image and quantify these parameters in the pulmonary microcirculation using a vacuum-stabilized lung imaging system.

Intravital imaging of leukocyte-endothelial interactions offers valuable insights into immune-mediated disease in live animals. The study of acute lung ...

Real-Time Monitoring of Cellular Dynamics in Mouse Lung Transplantation

Intravital Two-Photon Microscopy of the Transplanted Mouse Lung

Complications after lung transplantation are largely related to the host immune system responding to the graft. Such immune responses are regulated by crosstalk between donor and recipient cells. A better understanding of these processes relies on the use of preclinical animal models and is aided by an ability to study intra-graft immune cell trafficking in real-time. Intravital two-photon microscopy can be used to image tissues and organs for depths up to several hundred microns with minimal photodamage, which affords a great advantage over single-photon confocal microscopy. Selective use of transgenic mice with promoter-specific fluorescent protein expression and/or adoptive transfer of fluorescent dye-labeled cells during intravital two-photon microscopy allows for the dynamic study of single cells within their physiologic environment. Our group has developed a technique to stabilize mouse lungs, which has enabled us to image cellular dynamics in na&#239;ve lungs and orthotopically transplanted pulmonary grafts. This technique allows for detailed assessment of cellular behavior within the vasculature and in the interstitium, as well as for examination of interactions between various cell populations. This procedure can be readily learned and adapted to study immune mechanisms that regulate inflammatory and tolerogenic responses after lung transplantation. It can also be expanded to the study of other pathogenic pulmonary conditions.

Author Spotlight: Advancing Lung Transplant Immunology Through Intravital Imaging

Here, we present a protocol to intravitally image the transplanted mouse left lung using two-photon microscopy. This represents a valuable tool for studying cellular dynamics and interactions in real-time following murine lung transplantation.

Complications after lung transplantation are largely related to the host immune system responding to the graft. Such immune responses are regulated by ...

Longitudinal Intravital Microscopy Using a Mammary Imaging Window with Replaceable Lid

The branched structure of the mammary gland is highly dynamic and undergoes several phases of growth and remodeling after birth. Intravital microscopy in combination with skin flap surgery or implantation of imaging windows has been used to study the dynamics of the healthy mammary gland at different developmental stages. Most mammary imaging technologies are limited to a time frame of hours to days, whereas the majority of mammary gland remodeling processes occur in time frames of days to weeks. To study mammary gland remodeling, methods that allow optical access to the tissue of interest for extended time frames are required. Here, an improved version of the titanium mammary imaging window with a replaceable lid (R.MIW) is described that allows high-resolution imaging of the mammary gland with a cellular resolution for up to several weeks. Importantly, the R.MIW provides tissue access over the entire duration of the intravital imaging experiment and could therefore be used for local tissue manipulation, labeling, drug administration, or image-guided microdissection. Taken together, the R.MIW enables high-resolution characterization of the cellular dynamics during mammary gland development, homeostasis, and disease.

This protocol describes a novel mammary imaging window with a replaceable lid (R.MIW). Intravital microscopy after implantation of the R.MIW allows for longitudinal and multi-day imaging of the healthy and diseased mammary gland with a cellular resolution during the different developmental stages.

The branched structure of the mammary gland is highly dynamic and undergoes several phases of growth and remodeling after birth. Intravital microscopy in ...

Biology

Intravital Imaging Using an Inverted Microscope to Track Skin Cell Dynamics

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 

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 ...

Long-term High-Resolution Intravital Microscopy in the Lung with a Vacuum Stabilized Imaging Window

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