Support for this work was provided by National Institutes of Health grant #R01 HL 108229, American Heart Association Scientist Development Grant #0830352N, Howard Hughes Medical Institute Career Development Award, Broadview Ventures, European Community's Seventh Framework Programme (FP7/2007-2013 under grant agreement #235689), and the MGH William Schreyer Fellowship.

In vivo Animal Model: Generation of Experimental AortoIliac Atherosclerosis
1) Baseline Angiography and Balloon Denudation
<ol>
 <li>Prior to obtaining baseline angiography and balloon denudation, a New Zealand white rabbit is fed a high cholesterol (1%) diet for 1 week. This animal is utilized for translational relevance as 1) the aorto-iliacs vessels in rabbits are the same caliber as human coronary arteries (2.5-3.5mm) and 2) the hyperlipidemic, balloon-injury model generates inflamed atherosclerosis bearing similar inflammatory cells (macrophages) and molecules (cathepsins) as in human atherosclerosis.</li>
 <li>Following cholesterol feeding, the animal is anesthetized with propofol and ketamine. A one-inch ventral midline neck incision is made using using a size 15-scalpel blade. Using blunt dissection techniques, the muscles underneath the fascia on the right side of the trachea is exposed. The left sternocephalicus muscle is separated along its connective tissue junction, and the right common carotid artery is exposed. The artery is separated from the vagus nerve. Proximal and distal suture loops are placed on the artery to allow for retraction and occlusion. A 1 to 2mm beveled arteriotomy is made through which a 5 French (outer diameter 1.67mm) vascular sheath is inserted and heparin (1000&mu;/mL, ~150units/kg) is administered intra-arterially via the sheath.</li>
 <li>Contrast dye (Ultravist) is then injected (1 to 2mL) over a 2 second period to obtain a control angiogram of the distal aorta and both iliac arteries.</li>
 <li>The iliofemoral arteries and aorta are then injured by endothelial denudation. Using standard fluoroscopy methods, a 3Fr Fogarty embolectomy catheter is placed in the distal iliofemoral artery and inflated with 0.3 to 0.5 cc of contrast (50% contrast/50% saline) or air. The catheter is then withdrawn proximally in its inflated state a distance along the right iliac and distal aorta up to the take-off of the left renal artery. Following the balloon denudation, angiography is repeated to document vessel patency. Following angiography, all catheters and sheaths are removed and the proximal right common carotid artery is ligated, the muscle and fascia are sutured with a 4/0 absorbable suture, and the skin incision closed with a 4/0 non-absorbable suture.</li>
 <li>The animal is then allowed to recover with administration of one dose antibiotics (Cephazolin, 0.5 grams IM). Pain medications including 0.01 mg/kg buprenorphine IM (twice a day as needed). Animals are then continued on 1% cholesterol for 4 weeks post-balloon denudation. At week 5, animals are transitioned to 0.3% cholesterol diet.</li>
</ol>
Integrated Multi-modal Imaging of Rabbit Atheromata
2) Labeling of proteolytically active inflamed plaque using injectable nanosensor; Angiography, intravascular ultrasound (IVUS), and in vivo intravascular NIRF imaging of Rabbit Atheroma
<ol>
 <li>Eight weeks following balloon injury and 24 hours prior to imaging, the rabbit is injected with intravenous 500 nmol/kg Prosense/VM110 (PerkinElmer) via ear vein.</li>
 <li>Twenty-four hours after injection, animals are anesthetized and arterial access is obtained via left common carotid artery (see step 1.2). Intra-arterial heparin is administered (150 units/kg). Baseline angiography is obtained as above.</li>
 <li>An IVUS catheter is loaded onto a clinical coronary artery capable 0.014 inch wire and inserted into the sheath. Using fluoroscopic guidance, the radiopaque tip of the wire is positioned distally into the right iliac artery. The IVUS catheter is then advanced into the proximal iliac artery using a standard clinical monorail technique.</li>
 <li>A 100 mm pullback is initiated and images are recorded. Longitudinal reconstruction of the vessel is obtained and luminal plaque is identified.</li>
 <li>The NIRF catheter11,12 is loaded onto the 0.014 inch wire (monorail system), and the catheter is carefully inserted into the sheath and imaging head is positioned distally into right iliac artery.</li>
 <li>Multiple automated pullbacks (1 mm/sec longitudinal pullback, 30 rounds per minute) are performed and fluorescence signals within zones of atherosclerosis are noted. Images are recorded and further processing with appropriate scaling and windowing based on range of signal is achieved.</li>
</ol>
3) Euthanasia and isolation of ex vivo aorto-iliac tissue
<ol>
 <li>Euthanasia is accomplished with 1cc of euthanasia agent (solution of 390mg sodium pentobarbital and 50mg phenytoin sodium), intravenous, single injection.</li>
 <li>The arterial tree is perfused with 0.9% normal saline until the inferior vena cava is clear of blood. The atherosclerotic aorta and iliac arteries are identified and dissected free from the surrounding tissues. In addition, small 2 x 2 cm pieces of liver, kidney, spleen and heart are also obtained.</li>
 <li>Ex vivo NIRF imaging with the intravascular NIRF imaging catheter can be done at this stage. The vessel is elongated and the NIRF catheter is re-inserted into proximal aorta until the imaging head is positioned at the right iliac artery or bifurcation. Multiple automated pullbacks are performed as above (see 2.6).</li>
</ol>
4) Ex vivo Fluorescence Reflectance Imaging (FRI) of dissected aorta and iliac arteries
<ol>
 <li>Dissected tissue is placed in 10-20 cc of normal saline and transported for FRI analyses (Kodak Image Station 4000MM Pro, Carestream Health, Inc.).</li>
 <li>Aorta, iliac vessels are elongated to approximate real-time lengths and images are obtained at multiple wavelengths [white light, green fluorescent channel (ex 495 nm, em 515 nm), Cy5 (ex 565 nm, em 670 nm) and Cy7 (ex 650 nm, em 760 nm)] channels. A series of exposure times are utilized for each wavelength (0.1-30sec) and acquired images are exported as DICOM or 16-bit unscaled TIFF files for further analyses. As positive and negative controls, organs (liver, spleen, kidney and heart) are imaged at similar channels and exposure times.</li>
 <li>Areas of increased signal in the near-infrared channel (780nm+) are noted in atherosclerotic arteries.</li>
</ol>
5) Tissue Embedding for Sectioning and immunohistochemical analysis
<ol>
 <li>Areas of normal (non-injured tissue; i.e. left iliac artery) and areas of plaque are identified and small 5-10 mm rings of tissue are embedded in OCT (Optimal Cutting Temperature) media. Blocks are stored at -80 C until sectioning.</li>
 <li>Standard techniques for sectioning and immunohistochemical analyses are performed. Hematoxylin and eosin stain, Ram-11 and Cathepsin B staining are performed.</li>
</ol>
Analyses and Integration of multi-modal Images (Angiography, IVUS, NIRF and FRI)
6) Processing of NIRF and FRI images
<ol>
 <li>DICOM files containing imaging data from NIRF and FRI (taken at near infrared 780 nm channel) pullbacks are processed using MATLAB and Osirix software, respectively. Proper windowing to display full range of signal intensity is achieved. Final images are exported as TIFF files.</li>
 <li>Files are imported into standard image processing software (Keynote can be used). Images are aligned based on reference points (i.e. vertebrae on angiogram, iliac bifurcation, and renal artery). Areas of normal vessel and plaque are identified.</li>
 <li>Regions of interest (ROI) are manually traced (for normal tissue and areas of plaque) and mean signal intensities are acquired using Osirix and MATLAB, respectively for both FRI and NIRF images. To guide appropriate tracing, the longitudinal IVUS image of the vessel is used and identification of normal vessel and plaque are easily identified.</li>
 <li>Target-to background (TBR) ratios are calculated for plaque zones.</li>
</ol>
Representative Results:
Upon completion of above protocol, we can identify and characterize areas of augmented cathepsin protease activity in inflammatory plaque within the aorta and iliac vessels. Injection of an activatable nanosensor (Prosense/VM110) allows us to identify proteolytically active plaque. These appear as bright or signal intense zones when imaged using FRI in the near infrared channel (750 nm). The NIRF pullbacks correlate with increased signal intensity by FRI and alignments with IVUS which allow anatomical registration of NIRF signals. Calculated plaque TBR's obtained from FRI and NIRF were similar (see Figure 3: mean NIRF TBR 4.2, mean FRI TBR 2.9). Immunohistochemical analysis of bright plaque confirms intense presence of RAM-11 and Cathepsin B activity in areas of plaque (data not shown).
<img alt="Figure 1" src="/files/ftp_upload/2257/2257fig1.jpg" /> 
Figure 1. Schematic of 2D NIRF Catheter To extend the clinical potential of a 1D NIRF sensing approach6, we constructed a novel 2-D NIRF-catheter for intravascular imaging.11,12 The custom-built catheter consists of an optical fiber (125 micron diameter housed in polyethylene tubing: 2.9F) that illuminates using a 750 nm laser excitation source. Laser light is emitted at a 90 degree angle relative to fiber axis. The system utilizes two automated motors (rotational and translational) to enable concomitant 360 degree imaging and longitudinal pullback to obtain true 2D imaging. Images used with permission from reference 11.
<img alt="Figure 2" src="/files/ftp_upload/2257/2257fig2.jpg" /> 
Figure 2. Schematic demonstrating protease-mediated activation of the nanosensor, Prosense/VM110. Image used with permission from reference 10.
 
<img alt="Table 1" src="/files/ftp_upload/2257/2257table1.jpg" /> 
Figure 3. In vivo and ex vivo Plaque TBRs (target-to background ratios)

<ol>
	<li>Andersson, J., Libby, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptive+immunity+and+atherosclerosis.">Adaptive immunity and atherosclerosis.</a> Clin Immunol. 134, 33-46 (2010).</li><li>Calfon, M. A., Vinegoni, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intravascular+near-infrared+fluorescence+molecular+imaging+of+atherosclerosis:+toward+coronary+arterial+visualization+of+biologically+high-risk+plaques.">Intravascular near-infrared fluorescence molecular imaging of atherosclerosis: toward coronary arterial visualization of biologically high-risk plaques.</a> Journal of Biomedical Optics. 15, 011107-011107 (2010).</li><li>Chen, J., Tung, C. -. H. <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+Proteolytic+Activity+in+Atherosclerosis.">In Vivo Imaging of Proteolytic Activity in Atherosclerosis.</a> Circulation. 105, 2766-2771 (2002).</li><li>Jaffer, F. A., Libby, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+Imaging+of+Cardiovascular+Disease.">Molecular Imaging of Cardiovascular Disease.</a> Circulation. 116, 1052-1061 (2007).</li><li>Jaffer, F. A., Libby, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+and+Multimodality+Molecular+Imaging:+Insights+Into+Atherosclerosis.">Optical and Multimodality Molecular Imaging: Insights Into Atherosclerosis.</a> Arterioscler Thromb Vasc Biol. 29, 1017-1024 (2009).</li><li>Jaffer, F. A., Vinegoni, C. <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+Catheter+Molecular+Sensing+of+Inflammation+in+Proteolytically+Active+Atherosclerosis.">Real-Time Catheter Molecular Sensing of Inflammation in Proteolytically Active Atherosclerosis.</a> Circulation. 118, 1802-1809 (2008).</li><li>Kim, D. -. E., Kim, J. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protease+Imaging+of+Human+Atheromata+Captures+Molecular+Information+of+Atherosclerosis,+Complementing+Anatomic+Imaging.">Protease Imaging of Human Atheromata Captures Molecular Information of Atherosclerosis, Complementing Anatomic Imaging.</a> Arterioscler Thromb Vasc Biol. 30, 449-456 (2010).</li><li>Libby, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+in+atherosclerosis.">Inflammation in atherosclerosis.</a> Nature. 420, 868-874 (2002).</li><li>Naghavi, M., Libby, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+Vulnerable+Plaque+to+Vulnerable+Patient:+A+Call+for+New+Definitions+and+Risk+Assessment+Strategies:+Part+I.">From Vulnerable Plaque to Vulnerable Patient: A Call for New Definitions and Risk Assessment Strategies: Part I.</a> Circulation. 108, 1664-1672 (2003).</li><li>Weissleder, R., Tung, C. -. H. <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+tumors+with+protease-activated+near-infrared+fluorescent+probes.">In vivo imaging of tumors with protease-activated near-infrared fluorescent probes.</a> Nat Biotech. 17, 375-375 (1999).</li><li>Razansky, R. N., Rosenthal, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Near-infrared+fluorescence+catheter+system+for+two-dimensional+intravascular+imaging+in+vivo.">Near-infrared fluorescence catheter system for two-dimensional intravascular imaging in vivo.</a> Optics Express. 18, 11372-11381 (2010).</li><li>Jaffer, F. A., Calfon, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-Dimensional+Intravascular+Near-Infrared+Fluorescence+Molecular+Imaging+of+Inflammation+in+Atherosclerosis+and+Stent-Induced+Vascular+Injury.">Two-Dimensional Intravascular Near-Infrared Fluorescence Molecular Imaging of Inflammation in Atherosclerosis and Stent-Induced Vascular Injury.</a> Journal of the American College of Cardiology. 57, 2516-2526 (2011).</li></ol>

FAJ - Former Consultant, VisEn Medical; Honoraria, Boston Scientific

Inflamed high-risk or vulnerable plaques are likely responsible for the majority of myocardial infarctions. The identification of such plaques prior to onset of symptoms has important clinical implications both in predicting outcomes and guiding medical therapy. Conventional coronary arterial imaging modalities such as x-ray angiography typically focus on characterization of luminal narrowings rather than illuminating the underlying biological profiles of high-risk, usually non-stenotic lesions. Intravascular NIRF molecu...

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		<th>Catalogue Number</th>
		<th>Comment</th>
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<tr>
<td>Prosense 750</td>
<td>&nbsp;</td>
<td>Visen Medical</td>
<td>VM110</td>
<td>500 nmol/kg IV injection</td>
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<td>Heparin Sodium</td>
<td>&nbsp;</td>
<td>APP Pharmaceuticals</td>
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in vivo near infrared fluorescence (nirf) intravascular molecular imaging of inflammatory plaque, a multimodal approach to imaging of atherosclerosis

The vascular response to injury is a well-orchestrated inflammatory response triggered by the accumulation of macrophages within the vessel wall leading to an accumulation of lipid-laden intra-luminal plaque, smooth muscle cell proliferation and progressive narrowing of the vessel lumen. The formation of such vulnerable plaques prone to rupture underlies the majority of cases of acute myocardial infarction. The complex molecular and cellular inflammatory cascade is orchestrated by the recruitment of T lymphocytes and macrophages and their paracrine effects on endothelial and smooth muscle cells.1
Molecular imaging in atherosclerosis has evolved into an important clinical and research tool that allows in vivo visualization of inflammation and other biological processes. Several recent examples demonstrate the ability to detect high-risk plaques in patients, and assess the effects of pharmacotherapeutics in atherosclerosis.4 While a number of molecular imaging approaches (in particular MRI and PET) can image biological aspects of large vessels such as the carotid arteries, scant options exist for imaging of coronary arteries.2 The advent of high-resolution optical imaging strategies, in particular near-infrared fluorescence (NIRF), coupled with activatable fluorescent probes, have enhanced sensitivity and led to the development of new intravascular strategies to improve biological imaging of human coronary atherosclerosis.
Near infrared fluorescence (NIRF) molecular imaging utilizes excitation light with a defined band width (650-900 nm) as a source of photons that, when delivered to an optical contrast agent or fluorescent probe, emits fluorescence in the NIR window that can be detected using an appropriate emission filter and a high sensitivity charge-coupled camera. As opposed to visible light, NIR light penetrates deeply into tissue, is markedly less attenuated by endogenous photon absorbers such as hemoglobin, lipid and water, and enables high target-to-background ratios due to reduced autofluorescence in the NIR window. Imaging within the NIR 'window' can substantially improve the potential for in vivo imaging.2,5
Inflammatory cysteine proteases have been well studied using activatable NIRF probes10, and play important roles in atherogenesis. Via degradation of the extracellular matrix, cysteine proteases contribute importantly to the progression and complications of atherosclerosis8. In particular, the cysteine protease, cathepsin B, is highly expressed and colocalizes with macrophages in experimental murine, rabbit, and human atheromata.3,6,7 In addition, cathepsin B activity in plaques can be sensed in vivo utilizing a previously described 1-D intravascular near-infrared fluorescence technology6, in conjunction with an injectable nanosensor agent that consists of a poly-lysine polymer backbone derivatized with multiple NIR fluorochromes (VM110/Prosense750, ex/em 750/780nm, VisEn Medical, Woburn, MA) that results in strong intramolecular quenching at baseline.10 Following targeted enzymatic cleavage by cysteine proteases such as cathepsin B (known to colocalize with plaque macrophages), the fluorochromes separate, resulting in substantial amplification of the NIRF signal. Intravascular detection of NIR fluorescence signal by the utilized novel 2D intravascular NIRF catheter now enables high-resolution, geometrically accurate in vivo detection of cathepsin B activity in inflamed plaque.
In vivo molecular imaging of atherosclerosis using catheter-based 2D NIRF imaging, as opposed to a prior 1-D spectroscopic approach,6 is a novel and promising tool that utilizes augmented protease activity in macrophage-rich plaque to detect vascular inflammation.11,12 The following research protocol describes the use of an intravascular 2-dimensional NIRF catheter to image and characterize plaque structure utilizing key aspects of plaque biology. It is a translatable platform that when integrated with existing clinical imaging technologies including angiography and intravascular ultrasound (IVUS), offers a unique and novel integrated multimodal molecular imaging technique that distinguishes inflammatory atheromata, and allows detection of intravascular NIRF signals in human-sized coronary arteries.

Watch this Scientific Journal Video about In vivo Near Infrared Fluorescence NIRF Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis at JoVE.co

In vivo Near Infrared Fluorescence NIRF Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis

We detail a new near-infrared fluorescence (NIRF) catheter for 2-dimensional intravascular molecular imaging of plaque biology in vivo. The NIRF catheter can visualize key biological processes such as inflammation by reporting on the presence of plaque-avid activatable and targeted NIR fluorochromes. The catheter utilizes clinical engineering and power requirements and is targeted for application in human coronary arteries. The following research study describes a multimodal imaging strategy that utilizes a novel in vivo intravascular NIRF catheter to image and quantify inflammatory plaque in proteolytically active inflamed rabbit atheromata.

In vivo Near Infrared Fluorescence (NIRF) Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis

The vascular response to injury is a well-orchestrated inflammatory response triggered by the accumulation of macrophages within the vessel wall leading ...

in-vivo-near-infrared-fluorescence-nirf-intravascular-molecular

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17.9K vistas.  Harvard Medical School. Se detalla una nueva en el infrarrojo cercano fluorescencia (NIRF) catéter de dos dimensiones de imagen intravascular molecular de la biología de la placa In vivo. El catéter NIRF pueden visualizar procesos biológicos clave, como la inflamación de la presentación de informes sobre la presencia de placa-ávido fluorocromos NIR activable y selectiva. El catéter se utiliza requisitos de ingeniería clínica y el poder y está destinada a la aplicación ...

Video: In vivo Near Infrared Fluorescence NIRF Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis

In vivo Dual Substrate Bioluminescent Imaging

Our understanding of how and when breast cancer cells transit from established primary tumors to metastatic sites has increased at an exceptional rate since the advent of in vivo bioluminescent imaging technologies 1-3. Indeed, the ability to locate and quantify tumor growth longitudinally in a single cohort of animals to completion of the study as opposed to sacrificing individual groups of animals at specific assay times has revolutionized how researchers investigate breast cancer metastasis. Unfortunately, current methodologies preclude the real-time assessment of critical changes that transpire in cell signaling systems as breast cancer cells (i) evolve within primary tumors, (ii) disseminate throughout the body, and (iii) reinitiate proliferative programs at sites of a metastatic lesion. However, recent advancements in bioluminescent imaging now make it possible to simultaneously quantify specific spatiotemporal changes in gene expression as a function of tumor development and metastatic progression via the use of dual substrate luminescence reactions. To do so, researchers take advantage for two light-producing luciferase enzymes isolated from the firefly (Photinus pyralis) and sea pansy (Renilla reniformis), both of which react to mutually exclusive substrates that previously facilitated their wide-spread use in in vitro cell-based reporter gene assays 4. Here we demonstrate the in vivo utility of these two enzymes such that one luminescence reaction specifically marks the size and location of a developing tumor, while the second luminescent reaction serves as a means to visualize the activation status of specific signaling systems during distinct stages of tumor and metastasis development. Thus, the objectives of this study are two-fold. First, we will describe the steps necessary to construct dual bioluminescent reporter cell lines, as well as those needed to facilitate their use in visualizing the spatiotemporal regulation of gene expression during specific steps of the metastatic cascade. Using the 4T1 model of breast cancer metastasis, we show that the in vivo activity of a synthetic Smad Binding Element (SBE) promoter was decreased dramatically in pulmonary metastasis as compared to that measured in the primary tumor 4-6. Recently, breast cancer metastasis was shown to be regulated by changes within the primary tumor microenvironment and reactive stroma, including those occurring in fibroblasts and infiltrating immune cells 7-9. Thus, our second objective will be to demonstrate the utility of dual bioluminescent techniques in monitoring the growth and localization of two unique cell populations harbored within a single animal during breast cancer growth and metastasis.

In vivo Dual Substrate Bioluminescent Imaging

Herein we describe the methods to construct, visualize, and quantify the bioluminescent reactions of both firefly and renilla luciferase enzymes expressed in metastatic breast cancer cells during their growth and metastasis in vivo.

Our understanding of how and when breast cancer cells transit from established primary tumors to metastatic sites has increased at an exceptional rate ...

Implantation of a Carotid Cuff for Triggering Shear-stress Induced Atherosclerosis in Mice

It is widely accepted that alterations in vascular shear stress trigger the expression of inflammatory genes in endothelial cells and thereby induce atherosclerosis (reviewed in 1 and 2). The role of shear stress has been extensively studied in vitro investigating the influence of flow dynamics on cultured endothelial cells 1,3,4 and in vivo in larger animals and humans 1,5,6,7,8. However, highly reproducible small animal models allowing systematic investigation of the influence of shear stress on plaque development are rare. Recently, Nam et al. 9 introduced a mouse model in which the ligation of branches of the carotid artery creates a region of low and oscillatory flow. Although this model causes endothelial dysfunction and rapid formation of atherosclerotic lesions in hyperlipidemic mice, it cannot be excluded that the observed inflammatory response is, at least in part, a consequence of endothelial and/or vessel damage due to ligation.
In order to avoid such limitations, a shear stress modifying cuff has been developed based upon calculated fluid dynamics, whose cone shaped inner lumen was selected to create defined regions of low, high and oscillatory shear stress within the common carotid artery 10. By applying this model in Apolipoprotein E (ApoE) knockout mice fed a high cholesterol western type diet, vascular lesions develop upstream and downstream from the cuff. Their phenotype is correlated with the regional flow dynamics 11 as confirmed by in vivo Magnetic Resonance Imaging (MRI) 12: Low and laminar shear stress upstream of the cuff causes the formation of extensive plaques of a more vulnerable phenotype, whereas oscillatory shear stress downstream of the cuff induces stable atherosclerotic lesions 11. In those regions of high shear stress and high laminar flow within the cuff, typically no atherosclerotic plaques are observed.
 
In conclusion, the shear stress-modifying cuff procedure is a reliable surgical approach to produce phenotypically different atherosclerotic lesions in ApoE-deficient mice.

The constricting cuff presented in this article is designed to induce atherosclerosis in the murine common carotid artery. Due to the conical shape of its inner lumen the implanted cuff generates well-defined regions of low, high and oscillatory shear stress triggering the development of atherosclerotic lesions of different inflammatory phenotypes.

It is widely accepted that alterations in vascular shear stress trigger the expression of inflammatory genes in endothelial cells and thereby induce ...

Molecular Imaging to Target Transplanted Muscle Progenitor Cells

Duchenne muscular dystrophy (DMD) is a severe genetic neuromuscular disorder that affects 1 in 3,500 boys, and is characterized by progressive muscle degeneration1, 2. In patients, the ability of resident muscle satellite cells (SCs) to regenerate damaged myofibers becomes increasingly inefficient4. Therefore, transplantation of muscle progenitor cells (MPCs)/myoblasts from healthy subjects is a promising therapeutic approach to DMD. A major limitation to the use of stem cell therapy, however, is a lack of reliable imaging technologies for long-term monitoring of implanted cells, and for evaluating its effectiveness. Here, we describe a non-invasive, real-time approach to evaluate the success of myoblast transplantation. This method takes advantage of a unified fusion reporter gene composed of genes (firefly luciferase [fluc], monomeric red fluorescent protein [mrfp] and sr39 thymidine kinase [sr39tk]) whose expression can be imaged with different imaging modalities9, 10. A variety of imaging modalities, including positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), optical imaging, and high frequency 3D-ultrasound are now available, each with unique advantages and limitations11. Bioluminescence imaging (BLI) studies, for example, have the advantage of being relatively low cost and high-throughput. It is for this reason that, in this study, we make use of the firefly luciferase (fluc) reporter gene sequence contained within the fusion gene and bioluminescence imaging (BLI) for the short-term localization of viable C2C12 myoblasts following implantation into a mouse model of DMD (muscular dystrophy on the X chromosome [mdx] mouse)12-14. Importantly, BLI provides us with a means to examine the kinetics of labeled MPCs post-implantation, and will be useful to track cells repeatedly over time and following migration. Our reporter gene approach further allows us to merge multiple imaging modalities in a single living subject; given the tomographic nature, fine spatial resolution and ability to scale up to larger animals and humans10,11, PET will form the basis of future work that we suggest may facilitate rapid translation of methods developed in cells to preclinical models and to clinical applications.

A non-invasive means to evaluate the success of myoblast transplantation is described. The method takes advantage of a unified fusion reporter gene composed of genes whose expression can be imaged with different imaging modalities. Here, we make use of a fluc reporter gene sequence to target cells via bioluminescence imaging.

Duchenne muscular dystrophy (DMD) is a severe genetic neuromuscular disorder that affects 1 in 3,500 boys, and is characterized by progressive muscle ...

In vivo Imaging of Tumor Angiogenesis using Fluorescence Confocal Videomicroscopy

Fibered confocal fluorescence in vivo imaging with a fiber optic bundle uses the same principle as fluorescent confocal microscopy. It can excite fluorescent in situ elements through the optical fibers, and then record some of the emitted photons, via the same optical fibers. The light source is a laser that sends the exciting light through an element within the fiber bundle and as it scans over the sample, recreates an image pixel by pixel. As this scan is very fast, by combining it with dedicated image processing software, images in real time with a frequency of 12 frames/sec can be obtained.
We developed a technique to quantitatively characterize capillary morphology and function, using a confocal fluorescence videomicroscopy device. The first step in our experiment was to record 5 sec movies in the four quadrants of the tumor to visualize the capillary network. All movies were processed using software (ImageCell, Mauna Kea Technology, Paris France) that performs an automated segmentation of vessels around a chosen diameter (10 &mu;m in our case). Thus, we could quantify the 'functional capillary density', which is the ratio between the total vessel area and the total area of the image. This parameter was a surrogate marker for microvascular density, usually measured using pathology tools.
The second step was to record movies of the tumor over 20 min to quantify leakage of the macromolecular contrast agent through the capillary wall into the interstitium. By measuring the ratio of signal intensity in the interstitium over that in the vessels, an 'index leakage' was obtained, acting as a surrogate marker for capillary permeability.

In vivo Imaging of Tumor Angiogenesis using Fluorescence Confocal Videomicroscopy

In this paper, we present a method to analyze tumor microvessels in vivo using dynamic contrast-enhanced fluorescence videomicroscopy. Two quantitative parameters were acquired: functional capillary density reflecting the vascularity of the tumor, and index leakage reflecting the leakiness of the endothelial wall.

Fibered confocal fluorescence in vivo imaging with a fiber optic bundle uses the same principle as fluorescent confocal microscopy. It can excite ...

A Human Ex Vivo Atherosclerotic Plaque Model to Study Lesion Biology

Atherosclerosis is a chronic inflammatory disease of the vasculature. There are various methods to study the inflammatory compound in atherosclerotic lesions. Mouse models are an important tool to investigate inflammatory processes in atherogenesis, but these models suffer from the phenotypic and functional differences between the murine and human immune system. In vitro cell experiments are used to specifically evaluate cell type-dependent changes caused by a substance of interest, but culture-dependent variations and the inability to analyze the influence of specific molecules in the context of the inflammatory compound in atherosclerotic lesions limit the impact of the results. In addition, measuring levels of a molecule of interest in human blood helps to further investigate its clinical relevance, but this represents systemic and not local inflammation. Therefore, we here describe a plaque culture model to study human atherosclerotic lesion biology ex vivo. In short, fresh plaques are obtained from patients undergoing endarterectomy or coronary artery bypass grafting and stored in RPMI medium on ice until usage. The specimens are cut into small pieces followed by random distribution into a 48-well plate, containing RPMI medium in addition to a substance of interest such as cytokines or chemokines alone or in combination for defined periods of time. After incubation, the plaque pieces can be shock frozen for mRNA isolation, embedded in Paraffin or OCT for immunohistochemistry staining or smashed and lysed for western blotting. Furthermore, cells may be isolated from the plaque for flow cytometry analysis. In addition, supernatants can be collected for protein measurement by ELISA. In conclusion, the presented ex vivo model opens the possibility to further study inflammatory lesional biology, which may result in identification of novel disease mechanisms and therapeutic targets.

A Human Ex Vivo Atherosclerotic Plaque Model to Study Lesion Biology

Atherosclerosis is a chronic inflammatory process. This manuscript illustrates an easy to use ex vivo model to investigate fresh carotid or coronary artery plaques. The ex vivo model allows for the investigation of potential substances on the inflammatory milieu in human atherosclerotic lesions and results can be analyzed by various methods.

Atherosclerosis is a chronic inflammatory disease of the vasculature. There are various methods to study the inflammatory compound in atherosclerotic ...

Tissue-simulating Phantoms for Assessing Potential Near-infrared Fluorescence Imaging Applications in Breast Cancer Surgery

Inaccuracies in intraoperative tumor localization and evaluation of surgical margin status result in suboptimal outcome of breast-conserving surgery (BCS). Optical imaging, in particular near-infrared fluorescence (NIRF) imaging, might reduce the frequency of positive surgical margins following BCS by providing the surgeon with a tool for pre- and intraoperative tumor localization in real-time. In the current study, the potential of NIRF-guided BCS is evaluated using tissue-simulating breast phantoms for reasons of standardization and training purposes.
Breast phantoms with optical characteristics comparable to those of normal breast tissue were used to simulate breast conserving surgery. Tumor-simulating inclusions containing the fluorescent dye indocyanine green (ICG) were incorporated in the phantoms at predefined locations and imaged for pre- and intraoperative tumor localization, real-time NIRF-guided tumor resection, NIRF-guided evaluation on the extent of surgery, and postoperative assessment of surgical margins. A customized NIRF camera was used as a clinical prototype for imaging purposes.
Breast phantoms containing tumor-simulating inclusions offer a simple, inexpensive, and versatile tool to simulate and evaluate intraoperative tumor imaging. The gelatinous phantoms have elastic properties similar to human tissue and can be cut using conventional surgical instruments. Moreover, the phantoms contain hemoglobin and intralipid for mimicking absorption and scattering of photons, respectively, creating uniform optical properties similar to human breast tissue. The main drawback of NIRF imaging is the limited penetration depth of photons when propagating through tissue, which hinders (noninvasive) imaging of deep-seated tumors with epi-illumination strategies.

Near-infrared fluorescence (NIRF) imaging may improve therapeutic outcome of breast cancer surgery by enabling intraoperative tumor localization and evaluation of surgical margin status. Using tissue-simulating breast phantoms containing fluorescent tumor-simulating inclusions, potential clinical applications of NIRF imaging in breast cancer patients can be assessed for standardization and training purposes.

Inaccuracies in intraoperative tumor localization and evaluation of surgical margin status result in suboptimal outcome of breast-conserving surgery ...

Murine Endoscopy for In Vivo Multimodal Imaging of Carcinogenesis and Assessment of Intestinal Wound Healing and Inflammation

Mouse models are widely used to study pathogenesis of human diseases and to evaluate diagnostic procedures as well as therapeutic interventions preclinically. However, valid assessment of pathological alterations often requires histological analysis, and when performed ex vivo, necessitates death of the animal. Therefore in conventional experimental settings, intra-individual follow-up examinations are rarely possible. Thus, development of murine endoscopy in live mice enables investigators for the first time to both directly visualize the gastrointestinal mucosa and also repeat the procedure to monitor for alterations. Numerous applications for in vivo murine endoscopy exist, including studying intestinal inflammation or wound healing, obtaining mucosal biopsies repeatedly, and to locally administer diagnostic or therapeutic agents using miniature injection catheters. Most recently, molecular imaging has extended diagnostic imaging modalities allowing specific detection of distinct target molecules using specific photoprobes. In conclusion, murine endoscopy has emerged as a novel cutting-edge technology for diagnostic experimental in vivo imaging and may significantly impact on preclinical research in various fields.

Murine Endoscopy for In Vivo Multimodal Imaging of Carcinogenesis and Assessment of Intestinal Wound Healing and Inflammation

Small animal imaging techniques allow serial diagnostic examinations and therapeutic interventions in vivo. Recently, the scope of applications has significantly widened and currently includes assessment of colonic tumor development, wound healing and monitoring of inflammation. This protocol illustrates these diverse potential applications of murine endoscopy.

Mouse models are widely used to study pathogenesis of human diseases and to evaluate diagnostic procedures as well as therapeutic interventions ...

Validation of Nanobody and Antibody Based In Vivo Tumor Xenograft NIRF-imaging Experiments in Mice Using Ex Vivo Flow Cytometry and Microscopy

This protocol outlines the steps required to perform ex vivo validation of in vivo near-infrared fluorescence (NIRF) xenograft imaging experiments in mice using fluorophore labelled nanobodies and conventional antibodies.
First we describe how to generate subcutaneous tumors in mice, using antigen-negative cell lines as negative controls and antigen-positive cells as positive controls in the same mice for intraindividual comparison. We outline how to administer intravenously near-infrared fluorophore labelled (AlexaFluor680) antigen-specific nanobodies and conventional antibodies. In vivo imaging was performed with a small-animal NIRF-Imaging system. After the in vivo imaging experiments the mice were sacrificed. We then describe how to prepare the tumors for parallel ex vivo analyses by flow cytometry and fluorescence microscopy to validate in vivo imaging results.
The use of the near-infrared fluorophore labelled nanobodies allows for non-invasive same day imaging in vivo. Our protocols describe the ex vivo quantification of the specific labeling efficiency of tumor cells by flow cytometry and analysis of the distribution of the antibody constructs within the tumors by fluorescence microscopy. Using near-infrared fluorophore labelled probes allows for non-invasive, economical in vivo imaging with the unique ability to exploit the same probe without further secondary labelling for ex vivo validation experiments using flow cytometry and fluorescence microscopy.

Validation of Nanobody and Antibody Based In Vivo Tumor Xenograft NIRF-imaging Experiments in Mice Using Ex Vivo Flow Cytometry and Microscopy

This protocol outlines the steps required to perform ex vivo validation of in vivo near-infrared fluorescence xenograft imaging experiments in mice using fluorophore labelled nanobodies and conventional antibodies.

This protocol outlines the steps required to perform ex vivo validation of in vivo near-infrared fluorescence (NIRF) xenograft imaging experiments in mice ...

Combined Near-infrared Fluorescent Imaging and Micro-computed Tomography for Directly Visualizing Cerebral Thromboemboli

Direct thrombus imaging visualizes the root cause of thromboembolic infarction. Being able to image thrombus directly allows far better investigation of stroke than relying on indirect measurements, and will be a potent and robust vascular research tool. We use an optical imaging approach that labels thrombi with a molecular imaging thrombus marker&#160;&#8212; a Cy5.5 near-infrared fluorescent (NIRF) probe that is covalently linked to the fibrin strands of the thrombus by the fibrin-crosslinking enzymatic action of activated coagulation factor XIIIa during the process of clot maturation. A micro-computed tomography (microCT)-based approach uses thrombus-seeking gold nanoparticles (AuNPs) functionalized to target the major component of the clot: fibrin. This paper describes a detailed protocol for the combined in vivo microCT and ex vivo NIRF imaging of thromboemboli in a mouse model of embolic stroke. We show that in vivo microCT and fibrin-targeted glycol-chitosan AuNPs (fib-GC-AuNPs) can be used for visualizing both in situ thrombi and cerebral embolic thrombi. We also describe the use of in vivo microCT-based direct thrombus imaging to serially monitor the therapeutic effects of tissue plasminogen activator-mediated thrombolysis. After the last imaging session, we demonstrate by ex vivo NIRF imaging the extent and the distribution of residual thromboemboli in the brain. Finally, we describe quantitative image analyses of microCT and NIRF imaging data. The combined technique of direct thrombus imaging allows two independent methods of thrombus visualization to be compared: the area of thrombus-related fluorescent signal on ex vivo NIRF imaging vs. the volume of hyperdense microCT thrombi in vivo.

This protocol describes the application of combined near-infrared fluorescent (NIRF) imaging and micro-computed tomography (microCT) for visualizing cerebral thromboemboli. This technique allows the quantification of thrombus burden and evolution. The NIRF imaging technique visualizes fluorescently labeled thrombus in excised brain, while the microCT technique visualizes thrombus inside living animals using gold-nanoparticles.

Direct thrombus imaging visualizes the root cause of thromboembolic infarction. Being able to image thrombus directly allows far better investigation of ...

Induction of Accelerated Atherosclerosis in Mice: The "Wire-Injury" Model

Atherosclerosis is a proliferative fibro-inflammatory disease developing in the arterial wall, inducing a deficient blood flow or a lack of blood flow. Moreover, by rupture of the defective vascular wall, atherosclerosis induces occlusive thrombus formation, which represents the main cause of myocardial infarction or stroke and the most frequent cause of death. Despite the advances in the cardiovascular field, many questions remain unanswered, and additional basic research is essential to improve our understanding of the molecular mechanisms during atherosclerosis and its effects. Due to limited clinical studies, there is a need for representative animal models recreating atherosclerotic conditions such as neointima formation after stent implantation, balloon angioplasty, or endarterectomy. Since the mouse presents many advantages and is the most frequently used model for studying molecular processes, the current study proposes an invasive procedure of endothelial denudation, also known as the wire-injury model, which is representative of the human condition of neointima formation in arteries after revascularization procedures.

Induction of Accelerated Atherosclerosis in Mice: The &quot;Wire-Injury&quot; Model

This study describes an invasive procedure for the induction of accelerated atherosclerosis in mice. In comparison to other methods using electric- or cryo-induced injury, mechanical-induced injury mimics the human condition of restenosis after revascularization therapies and is ideal for the study of the molecular mechanisms involved.

Atherosclerosis is a proliferative fibro-inflammatory disease developing in the arterial wall, inducing a deficient blood flow or a lack of blood flow. ...