Ethics statement: All experiments were approved by the Institutional Animal Care and Use Committee. Animal care was according to institutional guidelines. ICR female mice (7 - 8 weeks old;&#160;25 - 30 g) were housed in air conditioned, light controlled animal facilities of the Sackler Faculty of Medicine in Tel-Aviv University. At term, animals were euthanized with anesthesia overdose.
1. Fibred Confocal Fluorescence Microscopy (FCFM) Calibration
<ol>
	<li>Turn the device ON.</li>
	<li>Connect the microprobe (mini0/30).</li>
	<li>Calibrate the device according to manufacturer&#8217;s instructions.</li>
</ol>
2. Mice Preparation for Imaging&#160;
<ol>
	<li>Anesthetize&#160;by a subcutaneous injection of both Ketaset (100 mg/kg) and&#160;XYL-M2 (6 mg/kg). Confirm proper anesthetization by unresponsiveness to toe-pinch.</li>
	<li>Incise the skin&#160;below&#160;the&#160;groin&#160;in order to&#160;reveal&#160;the femoral arterial vessels. Keep the incision site moist with saline following incision.</li>
	<li>Heat the tail by using a bag (or a glove) filled with warm water (not too hot to touch) for approximately 30 sec. Prepare an intravenous (IV) shunt for administration of FITC dextran (a contrast agent) and of either saline or chemotherapeutic agent, by inserting a needle (30 G, 1/2 inch) into&#160;the&#160;tail vein and attaching a 1 ml syringe to it. Ensure the vein is open by injecting saline. 
	NOTE: An IV administration of FITC dextran (high molecular weight; 100&#160;&#181;l; 10 mg/ml; 2,000 kDa)&#160;facilitates visualizing the femoral microvasculature by FCFM.&#160;Doxorubicin (100 &#181;l; 8 mg/kg, Adriamycin) or saline&#160;will also be later&#160;administered IV into the pre-heated tail vein.</li>
	<li>Position the mouse supinely on a polystyrene stage. Secure the mouse to the pad and maintain position using surgical duct tape.</li>
</ol>
3. Imaging of Femoral Blood Vessels by FCFM During and After Administration of Doxorubicin&#160;or Saline
NOTE: The fibered confocal microscope used in this study is composed of two units: (1) microprobe (mini0/30). (2) Laser scanning unit (LSU-488; 488 nm wavelength).
<ol>
	<li>Perform all time-laps analyses using the LSU 488 nm wavelength laser.&#160; 
	NOTE: The main unit detector detects the filtered (500 - 650 nm) emitted fluorescence. The acquired images&#160;are&#160;reconstructed afterwards and displayed at&#160;a&#160;rate of 12 frames/sec.</li>
	<li>Disconnect carefully the syringe from the needle and attach a new syringe containing FITC dextran. Administer (IV) 100 &#181;l of FITC dextran.</li>
	<li>Shift&#160;the microprobe (mini0/30) to a suitable field of view and fixate it, following adjustment to the z-axis, in order to obtain the corresponding image. Wait for the initial signal to fade until a clear and focused signal is visible.</li>
	<li>Record a baseline blood flow for a short stabilization period (~30 sec). Then connect to the needle another syringe, containing either doxorubicin or saline. IV administer 100 &#181;l doxorubicin or saline.</li>
	<li>Monitor the flow of injected FITC-dextran continuously for 20 min. On the FCFM-associated software, use the diameter button on the upper ruler in order to measure the blood vessels&#160;and&#160;categorize them as small (&#60;15 &#181;m) or large (&#62;15 &#181;m).</li>
	<li>Euthanize the animal with anesthesia overdose.</li>
</ol>

<ol>
	<li>Chow, A. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anthracyclines+cause+endothelial+injury+in+pediatric+cancer+patients:+a+pilot+study.">Anthracyclines cause endothelial injury in pediatric cancer patients: a pilot study.</a> J Clin Oncol. 24 (6), 925-928 (2006).</li><li>Nuver, J., 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=Acute+chemotherapy-induced+cardiovascular+changes+in+patients+with+testicular+cancer.">Acute chemotherapy-induced cardiovascular changes in patients with testicular cancer.</a> J Clin Oncol. 23 (36), 9130-9137 (2005).</li><li>Vos, F. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+cell+effects+of+cytotoxics:+balance+between+desired+and+unwanted+effects.">Endothelial cell effects of cytotoxics: balance between desired and unwanted effects.</a> Cancer Treat Rev. 30 (6), 495-513 (2004).</li><li>Kerbel, R. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term='Accidental'+anti-angiogenic+drugs.+anti-oncogene+directed+signal+transduction+inhibitors+and+conventional+chemotherapeutic+agents+as+examples.Eur.">'Accidental' anti-angiogenic drugs. anti-oncogene directed signal transduction inhibitors and conventional chemotherapeutic agents as examples.Eur.</a> J Cancer. 36 (10), 1248-1257 (2000).</li><li>Soultati, 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=Endothelial+vascular+toxicity+from+chemotherapeutic+agents:+preclinical+evidence+and+clinical+implications.">Endothelial vascular toxicity from chemotherapeutic agents: preclinical evidence and clinical implications.</a> Cancer Treat Rev. 38 (5), 473-483 (2012).</li><li>Tempelhoff, G. F., 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=Blood+coagulation+during+adjuvant+epirubicin/cyclophosphamide+chemotherapy+in+patients+with+primary+operable+breast+cancer.">Blood coagulation during adjuvant epirubicin/cyclophosphamide chemotherapy in patients with primary operable breast cancer.</a> J Clin Oncol. 14 (9), 2560-2568 (1996).</li><li>Ben Aharon, I., 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=Doxorubicin-induced+vascular+toxicity--targeting+potential+pathways+may+reduce+procoagulant+activity.">Doxorubicin-induced vascular toxicity--targeting potential pathways may reduce procoagulant activity.</a> PLoS One. 8 (9), e7515 (2013).</li><li>Laemmel, E., 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=Fibered+confocal+fluorescence+microscopy+(Cell-viZio)+facilitates+extended+imaging+in+the+field+of+microcirculation.+A+comparison+with+intravital+microscopy.">Fibered confocal fluorescence microscopy (Cell-viZio) facilitates extended imaging in the field of microcirculation. A comparison with intravital microscopy.</a> J Vasc Res. 41 (5), 400-411 (2004).</li><li>Al-Gubory, K. H., Houdebine, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+imaging+of+green+fluorescent+protein-expressing+cells+in+transgenic+animals+using+fibred+confocal+fluorescence+microscopy.">In vivo imaging of green fluorescent protein-expressing cells in transgenic animals using fibred confocal fluorescence microscopy.</a> Eur J Cell Biol. 85 (8), 837-845 (2006).</li><li>Bar-Joseph, H., 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=In+vivo+bioimaging+as+a+novel+strategy+to+detect+doxorubicin-induced+damage+to+gonadal+blood+vessels.">In vivo bioimaging as a novel strategy to detect doxorubicin-induced damage to gonadal blood vessels.</a> PLoS One. 6 (9), e23492 (2011).</li><li>Kaushal, V., Kaushal, G. P., Mehta, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+toxicity+of+anthracyclines+on+cultured+endothelial+cells.">Differential toxicity of anthracyclines on cultured endothelial cells.</a> Endothelium. 11 (5-6), 253-258 (2004).</li><li>Kim, E. J., 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=Doxorubicin-induced+platelet+cytotoxicity:+a+new+contributory+factor+for+doxorubicin-mediated+thrombocytopenia.">Doxorubicin-induced platelet cytotoxicity: a new contributory factor for doxorubicin-mediated thrombocytopenia.</a> J Thromb Haemost. 7 (7), 1172-1183 (2009).</li><li>Walsh, J., Wheeler, H. R., Geczy, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+tissue+factor+on+human+monocytes+by+cisplatin+and+adriamycin.">Modulation of tissue factor on human monocytes by cisplatin and adriamycin.</a> Br J Haematol. 81 (4), 480-488 (1992).</li><li>Kotamraju, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Doxorubicin-induced+apoptosis+in+endothelial+cells+and+cardiomyocytes+is+ameliorated+by+nitrone+spin+traps+and+ebselen.+Role+of+reactive+oxygen+and+nitrogen+species.">Doxorubicin-induced apoptosis in endothelial cells and cardiomyocytes is ameliorated by nitrone spin traps and ebselen. Role of reactive oxygen and nitrogen species.</a> J Biol Chem. 275 (43), 33585-33592 (2000).</li><li>Vasquez-Vivar, J., 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=Endothelial+nitric+oxide+synthase-dependent+superoxide+generation+from+adriamycin.">Endothelial nitric oxide synthase-dependent superoxide generation from adriamycin.</a> Biochemistry. 36 (38), 11293-11297 (1997).</li></ol>

Evaluating chemotherapy-induced vascular toxicity is challenging due to the difficulty in visualizing the dynamics of vasculature in response to a stimuli in real-time. Numerous clinical studies have implicated that several chemotherapies cause direct vascular injury, yet the mechanism and characteristics of this toxicity remains to be elucidated. We have established a real-time, in vivo molecular imaging platform for evaluating the potential vascular toxicity of chemotherapy in mice comprising of fibered confoc...

Clinical evidence indicates that several classes of chemotherapies elicit a variety of vascular pathologies manifested by Raynaud phenomenon, hypertension, myocardialinfarction, cerebrovascular attack, and hepatic veno-occlusivedisease1,2. &#8220;&#8217;Accidental&#8217; anti-angiogenic drugs&#8221; is a fairly new term, which describes conventional chemotherapeutic agents that act as possible angiogenesis inhibitors, although they not originally developed for this purpose3-5 but designed to eliminate tumor cells by imposing as little &#8220;collateral damage&#8221; to normal cells as possible3. Several chemotherapies have been implied as vasculo-toxicants as observed in clinical studies using serum biomarkers. Among these are alkylating agents (such as cyclophosphamide), platinum compounds (such as cisplatin) and anthracyclines1,2,5-7.
Acute cardiovascular complications may occur as a result of vascular toxicity induced by chemotherapy. They may progress into chronic conditions like atherosclerosis and account for increased risk of late vascular morbidity. Yet, despite mounting clinical evidence, there is a paucity of designated studies emphasizing the mechanism of vascular toxicity and therefore, further elucidation of the exact pathogenesis they inflict is warranted.
A major challenge in revealing the mechanism of chemotherapy-induced vascular toxicity derives from the complexity of investigating vascular function in vivo. We describe herein a platform of high-resolution in vivo molecular imaging in mice that enables to capture blood flow and vessels&#8217; characteristics. This platform facilitates the detection of direct treatment-induced vascular effects: in real-time, as well as following them over a period of time within the same individuals.

<table border="0" cellpadding="0" cellspacing="0" width="1395">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Name of Material/ Equipment</td>
			<td style="width:423px;">Company</td>
			<td style="width:213px;">Catalog Number</td>
			<td style="width:183px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">general anesthesia (100mg/kg ketaset and 6mg/kg XYL-M2).&#160;</td>
			<td>Fort Dodge Animal Health, IA, USA and Biove Laboratories, France</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">a depilatory cream (Veet)</td>
			<td>&#160;ReckittBenckiser, Bristol, UK</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">A 30-gauge, 1/2-inch needle attached to 1 ml syringe&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FITC dextran at a volume of 100 &#181;l (10 mg/ml; FD2000S, MW 2000000 Dalton)&#160;</td>
			<td>Sigma</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Doxorubicin (8 mg/kg, Adriamycin)</td>
			<td>Teva, Israel</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">paclitaxel (1.2 mg/kg, Medexel)&#160;</td>
			<td>Taro, Israel</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Saline</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

chemotherapy-induced vascular toxicity - real-time in vivo imaging of vessel impairment

Certain classes of chemotherapies may exert acute vascular changes that may progress into long-term conditions that may predispose the patient to an increased risk of vascular morbidity.&#160;Yet, albeit&#160;the mounting clinical evidence, there is a paucity of clear studies of vascular toxicity and therefore the etiology of a heterogeneous group of vascular/cardiovascular disorders remains to be elucidated. Moreover, the mechanism that may underlie vascular toxicity can completely differ from the principles of chemotherapy-induced cardiotoxicity, which is related to direct myocyte injury. We have established a real-time, in vivo molecular imaging platform&#160;to evaluate&#160;the potential&#160;acute&#160;vascular toxicity of anti-cancer therapies.
We have set up a platform of in vivo, high-resolution molecular imaging&#160;in mice,&#160;suitable for visualizing vasculature within confined organs and reference blood vessels within the same individuals whereas each individual serve as its own control. Blood vessel walls were impaired after doxorubicin administration, representing a unique mechanism of vascular toxicity that may be the early event in end-organ injury. Herein, the method of fibered confocal fluorescent microscopy (FCFM) based imaging is described, which provides an innovative mode to understand physiological phenomena at the cellular and sub-cellular levels in animal subjects.

In vivo continuous imaging at real-time
The imaging apparatus used here is a high definition, fibered confocal microscope, equipped with a probe that enables visualization of vasculature and its response to various stimuli as chemotherapy. This method is minimally invasive since although it may facilitate imaging of deep vessels or organ, it requires a small incision for the probe. The probe bundles consist of tens of thousands of fibers, microscope optics and a proprietary precision con...

Watch this Scientific Journal Video about Chemotherapy-induced Vascular Toxicity - Real-time In vivo Imaging of Vessel Impairment at JoVE.com

Chemotherapy-induced Vascular Toxicity - Real-time In vivo Imaging of Vessel Impairment

We herein describe the method of fibered confocal fluorescent microscopy (FCFM) based imaging, which provides an innovative mode to understand physiological phenomena at the cellular and sub-cellular levels in animal subjects.

Chemotherapy-induced Vascular Toxicity - Real-time In vivo Imaging of Vessel Impairment

Certain classes of chemotherapies may exert acute vascular changes that may progress into long-term conditions that may predispose the patient to an ...

chemotherapy-induced-vascular-toxicity-real-time-vivo-imaging-vessel

Research

JoVE Journal

Medicine

7.3K Views.  Tel Aviv University. We herein describe the method of fibered confocal fluorescent microscopy (FCFM) based imaging, which provides an innovative mode to understand physiological phenomena at the cellular and sub-cellular levels in animal subjects.

Video: Chemotherapy-induced Vascular Toxicity - Real-time In vivo Imaging of Vessel Impairment

Multispectral Real-time Fluorescence Imaging for Intraoperative Detection of the Sentinel Lymph Node in Gynecologic Oncology

The prognosis in virtually all solid tumors depends on the presence or absence of lymph node metastases.1-3 Surgical treatment most often combines radical excision of the tumor with a full lymphadenectomy in the drainage area of the tumor. However, removal of lymph nodes is associated with increased morbidity due to infection, wound breakdown and lymphedema.4,5 As an alternative, the sentinel lymph node procedure (SLN) was developed several decades ago to detect the first draining lymph node from the tumor.6 In case of lymphogenic dissemination, the SLN is the first lymph node that is affected (Figure 1). Hence, if the SLN does not contain metastases, downstream lymph nodes will also be free from tumor metastases and need not to be removed. The SLN procedure is part of the treatment for many tumor types, like breast cancer and melanoma, but also for cancer of the vulva and cervix.7 The current standard methodology for SLN-detection is by peritumoral injection of radiocolloid one day prior to surgery, and a colored dye intraoperatively. Disadvantages of the procedure in cervical and vulvar cancer are multiple injections in the genital area, leading to increased psychological distress for the patient, and the use of radioactive colloid.
Multispectral fluorescence imaging is an emerging imaging modality that can be applied intraoperatively without the need for injection of radiocolloid. For intraoperative fluorescence imaging, two components are needed: a fluorescent agent and a quantitative optical system for intraoperative imaging. As a fluorophore we have used indocyanine green (ICG). ICG has been used for many decades to assess cardiac function, cerebral perfusion and liver perfusion.8 It is an inert drug with a safe pharmaco-biological profile. When excited at around 750 nm, it emits light in the near-infrared spectrum around 800 nm. A custom-made multispectral fluorescence imaging camera system was used.9.
The aim of this video article is to demonstrate the detection of the SLN using intraoperative fluorescence imaging in patients with cervical and vulvar cancer. Fluorescence imaging is used in conjunction with the standard procedure, consisting of radiocolloid and a blue dye. In the future, intraoperative fluorescence imaging might replace the current method and is also easily transferable to other indications like breast cancer and melanoma.

Fluorescence imaging is a promising innovative modality for image-guided surgery in surgical oncology. In this video we describe the technical procedure for detection of the sentinel lymph node using fluorescence imaging as showcased in gynecologic oncologicy. A multispectral fluorescence camera system, together with the fluorescent agent indocyanine green, is applied.

The prognosis in virtually all solid tumors depends on the presence or absence of lymph node metastases.1-3 Surgical treatment most often combines radical ...

Contrast Enhanced Vessel Imaging using MicroCT

Microscopic computed tomography (microCT) offers high-resolution volumetric imaging of the anatomy of living small animals. However, the contrast between different soft tissues and body fluids is inherently poor in micro-CT images 1. Under these circumstances, visualization of blood vessels becomes a nearly impossible task. To overcome this and to improve the visualization of blood vessels exogenous contrast agents can be used. Herein, we present a methodology for visualizing the vascular network in a rodent model. By using a long-acting aqueous colloidal polydisperse iodinated blood-pool contrast agent, eXIA 160XL, we optimized image acquisition parameters and volume-rendering techniques for finding blood vessels in live animals. Our findings suggest that, to achieve a superior contrast between bone and soft tissue from vessel, multiple-frames (at least 5-8/ frames per view), and 360-720 views (for a full 360&deg; rotation) acquisitions were mandatory. We have also demonstrated the use of a two-dimensional transfer function (where voxel color and opacity was assigned in proportion to CT value and gradient magnitude), in visualizing the anatomy and highlighting the structure of interest, the blood vessel network. This promising work lays a foundation for the qualitative and quantitative assessment of anti-angiogenesis preclinical studies using transgenic or xenograft tumor-bearing mice.

Contrast enhanced small animal vessel imaging by microCT is a rapid, cost-effective and high-throughput technique for serial in situ examination for tumor development, for analyzing the network of blood vessels that nourish them, and for following the response of tumors to preclinical therapeutic intervention(s).

Microscopic computed tomography (microCT) offers high-resolution volumetric imaging of the anatomy of living small animals. However, the contrast between ...

Evaluation of Nanoparticle Uptake in Tumors in Real Time Using Intravital Imaging

Current technologies for tumor imaging, such as ultrasound, MRI, PET and CT, are unable to yield high-resolution images for the assessment of nanoparticle uptake in tumors at the microscopic level1,2,3, highlighting the utility of a suitable xenograft model in which to perform detailed uptake analyses. Here, we use high-resolution intravital imaging to evaluate nanoparticle uptake in human tumor xenografts in a modified, shell-less chicken embryo model. The chicken embryo model is particularly well-suited for these in vivo analyses because it supports the growth of human tumors, is relatively inexpensive and does not require anesthetization or surgery 4,5. Tumor cells form fully vascularized xenografts within 7 days when implanted into the chorioallantoic membrane (CAM) 6. The resulting tumors are visualized by non-invasive real-time, high-resolution imaging that can be maintained for up to 72 hours with little impact on either the host or tumor systems. Nanoparticles with a wide range of sizes and formulations administered distal to the tumor can be visualized and quantified as they flow through the bloodstream, extravasate from leaky tumor vasculature, and accumulate at the tumor site. We describe here the analysis of nanoparticles derived from Cowpea mosaic virus (CPMV) decorated with near-infrared fluorescent dyes and/or polyethylene glycol polymers (PEG) 7, 8, 9,10,11. Upon intravenous administration, these viral nanoparticles are rapidly internalized by endothelial cells, resulting in global labeling of the vasculature both outside and within the tumor7,12. PEGylation of the viral nanoparticles increases their plasma half-life, extends their time in the circulation, and ultimately enhances their accumulation in tumors via the enhanced permeability and retention (EPR) effect 7, 10,11. The rate and extent of accumulation of nanoparticles in a tumor is measured over time using image analysis software. This technique provides a method to both visualize and quantify nanoparticle dynamics in human tumors.

We present a novel approach to quantify nanoparticle localization in the vasculature of human xenografted tumors using dynamic, real-time intravital imaging in an avian embryo model.

Current technologies for tumor imaging, such as ultrasound, MRI, PET and CT, are unable to yield high-resolution images for the assessment of nanoparticle ...

An in vivo Assay to Test Blood Vessel Permeability

This method is based on the intravenous injection of Evans Blue in mice as the test animal model. Evans blue is a dye that binds albumin. Under physiologic conditions the endothelium is impermeable to albumin, so Evans blue bound albumin remains restricted within blood vessels. In pathologic conditions that promote increased vascular permeability endothelial cells partially lose their close contacts and the endothelium becomes permeable to small proteins such as albumin. This condition allows for extravasation of Evans Blue in tissues. A healthy endothelium prevents extravasation of the dye in the neighboring vascularized tissues. Organs with increased permeability will show significantly increased blue coloration compared to organs with intact endothelium. The level of vascular permeability can be assessed by simple visualization or by quantitative measurement of the dye incorporated per milligram of tissue of control versus experimental animal/tissue. Two powerful aspects of this assay are its simplicity and quantitative characteristics. Evans Blue dye can be extracted from tissues by incubating a specific amount of tissue in formamide. Evans Blue absorbance maximum is at 620 nm and absorbance minimum is at 740 nm. By using a standard curve for Evans Blue, optical density measurements can be converted into milligram dye captured per milligram of tissue. Statistical analysis should be used to assess significant differences in vascular permeability.

An in vivo Assay to Test Blood Vessel Permeability

We are presenting an in vivo assay to test blood vessel permeability. This assay is based on intravenous injection of a dye and subsequent visualization of its diffusion into interstitial spaces.

This method is based on the intravenous injection of Evans Blue in mice as the test animal model. Evans blue is a dye that binds albumin. Under ...

Transplantation into the Anterior Chamber of the Eye for Longitudinal, Non-invasive In vivo Imaging with Single-cell Resolution in Real-time

Intravital imaging has emerged as an indispensable tool in biological research. In the process, many imaging techniques have been developed to study different biological processes in animals non-invasively. However, a major technical limitation in existing intravital imaging modalities is the inability to combine non-invasive, longitudinal imaging with single-cell resolution capabilities. We show here how transplantation into the anterior chamber of the eye circumvents such significant limitation offering a versatile experimental platform that enables non-invasive, longitudinal imaging with cellular resolution in vivo. We demonstrate the transplantation procedure in the mouse and provide representative results using a model with clinical relevance, namely pancreatic islet transplantation. In addition to enabling direct visualization in a variety of tissues transplanted into the anterior chamber of the eye, this approach provides a platform to screen drugs by performing long-term follow up and monitoring in target tissues. Because of its versatility, tissue/cell transplantation into the anterior chamber of the eye not only benefits transplantation therapies, it extends to other in vivo applications to study physiological and pathophysiological processes such as signal transduction and cancer or autoimmune disease development.

Transplantation into the Anterior Chamber of the Eye for Longitudinal, Non-invasive In vivo Imaging with Single-cell Resolution in Real-time

A new approach combining intraocular transplantation and confocal microscopy enables longitudinal, non-invasive real-time imaging with single-cell resolution within grafted tissues in vivo. We demonstrate how to transplant pancreatic islets into the anterior chamber of the mouse eye.

Intravital imaging has emerged as an indispensable tool in biological research.  In the process, many imaging techniques have been developed to study ...

Real-time X-ray Imaging of Lung Fluid Volumes in Neonatal Mouse Lung

At birth, the lung undergoes a profound phenotypic switch from secretion to absorption, which allows for adaptation to breathing independently. Promoting and sustaining this phenotype is critically important in normal alveolar growth and gas exchange throughout life. Several in vitro studies have characterized the role of key regulatory proteins, signaling molecules, and steroid hormones that can influence the rate of lung fluid clearance. However, in vivo examinations must be performed to evaluate whether these regulatory factors play important physiological roles in regulating perinatal lung liquid absorption. As such, the utilization of real time X-ray imaging to determine perinatal lung fluid clearance, or pulmonary edema, represents a technological advancement in the field. Herein, we explain and illustrate an approach to assess the rate of alveolar lung fluid clearance and alveolar flooding in C57BL/6 mice at post natal day 10 using X-ray imaging and analysis. Successful implementation of this protocol requires prior approval from institutional animal care and use committees (IACUC), an in vivo small animal X-ray imaging system, and compatible molecular imaging software.

We present a protocol to assess the rate of alveolar fluid clearance or pulmonary edema in neonatal mouse lung using X-ray imaging technology.

At birth, the lung undergoes a profound phenotypic switch from secretion to absorption, which allows for adaptation to breathing independently. Promoting ...

Rose Bengal Photothrombosis by Confocal Optical Imaging In Vivo: A Model of Single Vessel Stroke

In vivo imaging techniques have increased in utilization due to recent advances in imaging dyes and optical technologies, allowing for the ability to image cellular events in an intact animal. Additionally, the ability to induce physiological disease states such as stroke in vivo increases its utility. The technique described herein allows for physiological assessment of cellular responses within the CNS following a stroke and can be adapted for other pathological conditions being studied. The technique presented uses laser excitation of the photosensitive dye Rose Bengal in vivo to induce a focal ischemic event in a single blood vessel. 
The video protocol demonstrates the preparation of a thin-skulled cranial window over the somatosensory cortex in a mouse for the induction of a Rose Bengal photothrombotic event keeping injury to the underlying dura matter and brain at a minimum. Surgical preparation is initially performed under a dissecting microscope with a custom-made surgical/imaging platform, which is then transferred to a confocal microscope equipped with an inverted objective adaptor. Representative images acquired utilizing this protocol are presented as well as time-lapse sequences of stroke induction. This technique is powerful in that the same area can be imaged repeatedly on subsequent days facilitating longitudinal in vivo studies of pathological processes following stroke.

Rose Bengal Photothrombosis by Confocal Optical Imaging In Vivo:  A Model of Single Vessel Stroke

Here, we describe a semi-invasive optical microscopy approach for the induction of a Rose Bengal photothrombotic clot in the somatosensory cortex of a mouse in vivo. The technical aspects of the imaging procedure are described from induction of a photothrombotic event to application and data collection.

In vivo imaging techniques have increased in utilization due to recent advances in imaging dyes and optical technologies, allowing for the ability to ...

Ferric Chloride-induced Thrombosis Mouse Model on Carotid Artery and Mesentery Vessel

Severe thrombosis and its ischemic consequences such as myocardial infarction, pulmonary embolism and stroke are major worldwide health issues. The ferric chloride injury is now a well-established technique to rapidly and accurately induce the formation of thrombi in exposed veins or artery of small and large diameter. This model has played a key role in the study of the pathophysiology of thrombosis, in the discovery and validation of novel antithrombotic drugs and in the understanding of the mechanism of action of these new agents. Here, the implementation of this technique on a mesenteric vessel and carotid artery in mice is presented. The method describes how to label circulating leukocytes and platelets with a fluorescent dye and to observe, by intravital microscopy on the exposed mesentery, their accumulation at the injured vessel wall which leads to the formation of a thrombus. On the carotid artery, the occlusion caused by the clot formation is measured by monitoring the blood flow with a Doppler probe.

The FeCl3 induced thrombosis model in mice is described herein. A method to monitor thrombus growth by intravital microscopy observation on a mesenteric vessel and by blood flow measurement in the carotid artery is presented.

Severe thrombosis and its ischemic consequences such as myocardial infarction, pulmonary embolism and stroke are major worldwide health issues. The ferric ...

Extended Time-lapse Intravital Imaging of Real-time Multicellular Dynamics in the Tumor Microenvironment

In the tumor microenvironment, host stromal cells interact with tumor cells to promote tumor progression, angiogenesis, tumor cell dissemination and metastasis. Multicellular interactions in the tumor microenvironment can lead to transient events including directional tumor cell motility and vascular permeability. Quantification of tumor vascular permeability has frequently used end-point experiments to measure extravasation of vascular dyes. However, due to the transient nature of multicellular interactions and vascular permeability, the kinetics of these dynamic events cannot be discerned. By labeling cells and vasculature with injectable dyes or fluorescent proteins, high-resolution time-lapse intravital microscopy has allowed the direct, real-time visualization of transient events in the tumor microenvironment. Here we describe a method for using multiphoton microscopy to perform extended intravital imaging in live mice to directly visualize multicellular dynamics in the tumor microenvironment. This method details cellular labeling strategies, the surgical preparation of a mammary skin flap, the administration of injectable dyes or proteins by tail vein catheter and the acquisition of time-lapse images. The time-lapse sequences obtained from this method facilitate the visualization and quantitation of the kinetics of cellular events of motility and vascular permeability in the tumor microenvironment.

This protocol describes the use of multiphoton microscopy to perform extended time-lapse imaging of multicellular interactions in real time, in vivo at single cell resolution.

In the tumor microenvironment, host stromal cells interact with tumor cells to promote tumor progression, angiogenesis, tumor cell dissemination and ...

Real-time Pressure-volume Analysis of Acute Myocardial Infarction in Mice

Acute myocardial infarction can lead to acute heart failure and cardiogenic shock. The evaluation of hemodynamics is critical for the evaluation of any potential therapeutic approach directed against acute left ventricular (LV) dysfunction. Current imaging modalities (e.g., echocardiography and magnetic resonance imaging) have several limitations since data on LV pressure cannot directly be measured. LV catheterization in mice undergoing coronary artery occlusion could serve as a novel method for a real-time evaluation of LV function.
At the beginning of the procedure, mice were anesthetized followed by endotracheal intubation. For LV catheterization, the right carotid artery was exposed via middle-neck incision. The catheter was introduced and placed into the LV cavity. Left thoracotomy was conducted and the left main coronary artery (LCA) was ligated. To induce reperfusion, the suture was released after 45 min. Pressure-volume data was recorded at all times.
Ligation of the LCA caused a decrease in LV systolic function as evidenced by a 30% reduction in stroke volume, LV ejection fraction (EF), and cardiac output. Maximum dP/dt as a parameter for LV contractility was also significantly reduced and diastolic function was severely impaired (minimum dP/dt -40%). Reperfusion over a period of 20 min did not lead to a complete recovery of LV function.
Real-time pressure-volume analysis served as a valid procedure for monitoring cardiac function during acute myocardial infarction in mice. Maintaining stable anesthesia and a standardized surgical approach was crucial to ensure valid results. As the early phase of acute myocardial infarction is critical for morbidity and mortality, the delineated method could be beneficial for preclinical evaluation of new strategies for cardioprotection.

Acute myocardial infarction in mice induces acute but incompletely characterized changes in left ventricular (LV) function. LV catheterization in mice undergoing coronary artery occlusion serves as a novel method for a real-time evaluation of LV function.

Acute myocardial infarction can lead to acute heart failure and cardiogenic shock. The evaluation of hemodynamics is critical for the evaluation of any ...

Chemotherapy-induced Vascular Toxicity - Real-time In vivo Imaging of Vessel Impairment

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