We thank Sonja Dufentester and Elke Weber for expert technical assistance. We thank Faekah Gohar for proofreading the manuscript and Stefan Br&#252;ckner for medical informatics support. This work was supported by an interdisciplinary grant from the Else-Kr&#246;ner-Fresenius-Stiftung (2012_A94). D. Bettenworth was supported by a research fellowship from the Faculty of Medicine, Westf&#228;lische Wilhelms-Universit&#228;t M&#252;nster. M. Br&#252;ckner was supported by a &#8220;Gerok&#8221; rotational position of the Deutsche Forschungsgemeinschaft (DFG SFB1009B8).&#160;We thank Heike Blum for illustration of the mouse cartoon.

All animal experiments were approved by the Landesamt f&#252;r Natur, Umwelt und Verbraucherschutz (LANUV) according to German Animal Protection Law.
1. Materials and Experimental Setup
<ol>
	<li>Animal care
	<ol>
		<li>Use female or male mice of any strain weighing 20 to 25 g and house them according to local animal care legislation.</li>
		<li>Feed mice with special chow for rodents and apply alfalfa-free chow at least three days prior to fluorescence examinations to minimize endoluminal auto-fluorescence.</li>
		<li>Provide autoclaved drinking water ad libitum.</li>
	</ol>
	</li>
	<li>Induction of acute DSS-induced colitis
	<ol>
		<li>Prepare a 3% (w/v) dextran sulfate sodium (DSS, molecular weight: 36,000&#8211;50,000 Da) solution by dissolving 3 g of DSS in 100 ml autoclaved water. Offer this solution as the exclusive drinking water to mice ad libitum and calculate 5 ml of DSS-solution per mouse/day. Feed control mice with autoclaved water without DSS ad libitum9.</li>
	</ol>
	</li>
	<li>Induction of colorectal cancer
	<ol>
		<li>Dissolve mutagenic azoxymethane (AOM) (CAUTION! May cause cancer and genetic damage!) in sterile isotonic saline to obtain a final concentration of 1 mg/ml. Apply a single dose of 10 mg AOM per kg bodyweight intra-peritoneally using a 1 ml syringe (30 G)10.</li>
		<li>Challenge mice (excluding control mice) with repetitive cycles of 3% (w/v) DSS from day 0 to 7, day 14 to 21, day 28 to 35 and day 42 to 49 to induce inflammatory driven colorectal cancerogenesis. Feed mice with autoclaved water only in between these challenges (see Figure 4A for a detailed time schedule). Feed control mice with autoclaved water throughout the experiment.</li>
	</ol>
	</li>
	<li>Preparation of fluorescence endoscopy (FE)
	<ol>
		<li>Use Fluorescein-Isothiocyanat (FITC) - dextran (molecular weight 70,000 Da; FITC:Glucose = 1:250) for detection of colonic adenoma by visual enhancement of dysplasia associated vascular pattern.</li>
		<li>Administer 60 mg FITC-conjugated dextran diluted in 100 &#181;l PBS intravenously 5 min before fluorescence endoscopic examination.</li>
	</ol>
	</li>
	<li>Anesthesia
	<ol>
		<li>Provide continuous isoflurane supply for anesthesia (1.5 L O2/min; 1.5&#8211;2 vol% isoflurane [2-chloro-2-(difluoromethoxy)-1,1,1-trifluoro-ethane]). Use special veterinary anesthesia equipment with a facemask to tightly control anesthesia.</li>
	</ol>
	</li>
	<li>Preparation of enema
	<ol>
		<li>Instill 2 ml of fluid enema (contents: disodium hydrogenphosphate 1.5% (w/v) and sodium dihydrogenphosphate 11% (w/v)) into the colon if significant fecal loading is suspected that may obscure the view.</li>
	</ol>
	</li>
</ol>
2. Technical Equipment
<ol>
	<li>Use a veterinary endoscopic workstation that is developed and approved for the use of small animal endoscopy. Connect the workstation to a camera unit, a xenon light source, an air pump and to a conventional PC monitor for white light endoscopy. Then connect the camera and the miniature rigid telescope (1.9 mm outer diameter, 10 cm length; Figure 5).</li>
	<li>Use endoscope sheath with working channel (Figure 5D) for the application of biopsy forceps or injection tube. Use the sheath without working channel for diagnostic colonoscopy.</li>
	<li>Configure the settings of the light source for fluorescence endoscopy to excite used tracers (e.g., 490 nm for FITC-conjugated dextran). Additionally, integrate an appropriate bandpass filter between the telescope and the camera (e.g., 525 nm for FITC-conjugated dextran).</li>
	<li>Insert flexible biopsy forceps (3 Charr., 28 cm) through the working channel of the endoscope to obtain biopsies.</li>
	<li>Introduce flexible injection tube (0.96 mm) through the working channel for topical, intramucosal or endoluminal administration of diagnostic or therapeutic agents.</li>
	<li>Use a heatable examination table with a temperature of 42 &#176;C. This prevents mice becoming hypothermic during the examination.</li>
</ol>
3. Anesthesia of Animals
<ol>
	<li>Place mouse in a small but leakproof box and administer isoflurane (100% (v/v), 5 vol%, 3 L/min). Wait until the mouse loses consciousness.</li>
	<li>Transfer the mouse onto the examination table for endoscopy. Continue isoflurane inhalation via face mask with a dose 100% v/v, 1.5 vol%, 1.5 L/min. Always apply eye ointment to prevent eye dryness while under anesthesia.</li>
	<li>Evaluate efficacy of anesthesia by checking the reflexes. Check the &#8216;turn around reflex&#8217;: if sufficiently anaesthetized, a mouse laying on its back should not turn around. Check the &#8216;toes reflex&#8217;: when anesthesia is adequate, soft pinching in between the animal&#8217;s toes should not lead to withdrawal of leg (stage of surgical tolerance).</li>
</ol>
4. Colonoscopy
<ol>
	<li>Lay anesthetized mouse prone /on its back on the examination table.</li>
	<li>Administer 2 ml of enema via buttoned cannula into the colon if significant fecal loading is suspected that may obscure the view. Wait for mice to defecate after administering the enema. Insert the endoscope very carefully to avoid perforation.</li>
	<li>Open both valves of the sheath with one of them being connected to the air pump. Seal the other valve with your index finger to dispense air. Inflate colon with air, slowly and carefully, especially in case of biopsy or injection.</li>
	<li>Advance endoscope only as far as the right colonic flexure to avoid perforation (4&#8211;5 cm from anus).</li>
	<li>Diagnostic colonoscopy
	<ol>
		<li>Examine the mucosa for inflammatory or malignant alterations while pulling back the endoscope. Pull back slowly to assess the whole circumference of the bowel. Assess intraluminal pathologies using appropriate established scoring systems as required.</li>
		<li>To warrant identical endoscopic position for image acquisition during repetitive visualizations of wound areas, note the distance between the murine anus and the mucosal lesion. Moreover, use the tip of the biopsy forceps as a spacer to achieve identical distance between the endoscope and the wound area during image acquisition. The wound size is related to the size of the endoscope sheath, which comprises 3 mm. 
		NOTE: Place endoscope in identical position by optical comparison with photo documentation of previous examinations. Measure lesions in the same angle and distance at each follow up endoscopic examination.</li>
	</ol>
	</li>
	<li>Biopsy procedure
	<ol>
		<li>Take biopsies with the help of two investigators. Introduce the biopsy forceps carefully through the working channel until the tip of the forceps is visible on the monitor to the second investigator. Open and close forceps carefully to avoid perforation.</li>
		<li>Move forceps to the site of pathology.</li>
	</ol>
	</li>
	<li>Injection procedure
	<ol>
		<li>Perform injection procedure with the help of two investigators. Pre-fill flexible injection tube (0.96 mm) completely with the agent to be administered. Push tube through the working channel until the cannula (30 G) is visible on the monitor to the second investigator. Prepare the fine syringe and gently administer the requested amount of diagnostic or therapeutic agent. Injection volumes should be 50 &#181;l maximum.</li>
		<li>Insert the needle into the submocosa at an angle of 15&#8211;30 degrees. Face the bevel in direction of the mucosa. The mucosa shows a characteristic lifting sign after successful injection.</li>
	</ol>
	</li>
	<li>Fluorescence endoscopy (FE)
	<ol>
		<li>Administer 60 mg FITC-conjugated dextran diluted in 100 &#181;l PBS intravenously prior to fluorescence endoscopic examination.</li>
		<li>Check the optimal time point between injection of your fluorescent labeled tracer and the imaging procedure which is dependent on tracer pharmacology. Configure settings of bandpass filter system in accordance to excitation and emission wavelength of the tracer used. Perform fluorescence endoscopy for non-specific blood volume tracers (e.g., FITC) immediately after intravenous injection of the fluorescent dye to assess the vascular pattern of the mucosal surface.</li>
		<li>Consider imaging several hours after tracer application in case of targeted tracers or &#8216;smart probes&#8217; to provide a better target to background-ratio.</li>
		<li>Perform photo- and video-documentation of the results.</li>
	</ol>
	</li>
</ol>
5. Post-colonoscopy
<ol>
	<li>Separate the mouse in a vacant cage and lay it on a paper towel to protect the mouse from aspirating the litter. Warm the mouse with a redlight lamp to prevent hypothermia. Observe the mouse and do not leave unattended until it has regained sufficient consciousness to maintain sternal recumbency. Once completely conscious, place the mouse back to its respective cage.</li>
	<li>At the end of experiment, place mouse in a small but leakproof box and administer CO2 (100% (v/v), 100 vol%, 3 L/min). Wait until the mouse loses complete consciousness and stops breathing. Dispatch mouse by neck fracture. Perform abdominal laparotomy and explant the colon. Open the colon longitudinally and wash it for further histological or molecular evaluation.</li>
</ol>

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The authors have nothing to disclose.

Epithelial wound healing is an ongoing process. Continuous physiological exfoliation of surface cells within the gastrointestinal mucosa occurs requiring frequent regeneration of epithelial cells 16. Consequently, impaired wound healing has an immense impact on several diseases including gastrointestinal ulcers and 17 anastomotic leakage 18. Evaluation of molecular background as well as potential drug candidates to stimulate epithelial healing may only be incompletely performed in cell cu...

Animal models have greatly enriched our understanding of numerous intestinal pathologies. The laboratory mouse (Mus musculus) has emerged as a prime animal model in biomedical research due to its abundant genetic and genomic information and is readily available in transgenic and knockout strains. In addition to enhancing understanding disease pathogenesis, animal models are also importantly used for testing drug candidates as well as preclinical diagnostic or therapeutic interventions. However, despite the variety of mouse models mimicking human disease, many diagnostic and interventional options that are routinely used in patient care are not available for mice. Accordingly, surveillance strategies to monitor the course of murine disease or the effect of therapeutic interventions are often limited to indirect observations or post mortem analyses. While non-invasive procedures exist for monitoring mice vitality like disease activity indices, quantification of weight loss or gain, blood, urine and feces analyses, these are only indirect indicators and are biased by inter-individual variability. Additionally, post mortem analyses prevent longitudinal observations at repetitive time points. Sophisticated imaging techniques to monitor disease activity in mice have only recently been introduced 1,2. Although these imaging techniques allow for repetitive analyses, they only provide a descriptive and often imprecise view on the gut, do not enable direct mucosal visualization or allow diagnostic or therapeutic interventions such as biopsy acquisition or topical and intramucosal application of drug candidates.
Recently, high-resolution endoscopic systems for use in live mice have been developed 3,4. For the first time these endoscopic techniques allow direct visualization of endoluminal colonic disease pathologies such as wound healing or intestinal inflammation providing objective, real-time status allowing longitudinal studies in the same animal at repetitive time points. Aside from allowing repeated biopsies in an individual mouse, endoscopic systems can also be used to therapeutically influence a distinct tumor or localized inflammation by allowing direct application of a substance to the area of interest. Furthermore, as therapeutic and control substances can be delivered directly to the area of interest, this can be performed in the same mouse, excluding inter-individual variability. These systems have now been employed for the assessment of colonic inflammation, wound healing, laparoscopic liver biopsies and orthotopic induction of liver tumors 8 and tumor development using various scoring systems such as the murine endoscopic index of colitis severity (MEICS) 5-7. MEICS consists of five parameters to assess inflammation: thickening of the colon wall, changes of the vascular pattern, presence of fibrin, granularity of the mucosal surface, and stool consistence.
In this protocol we describe the use of rigid endoscopy in murine models of intestinal wound healing, inflammation and colon cancer. First, we demonstrate the endoscopic evaluation of wound healing and colonic inflammation as well as longitudinal assessment of colitis activity and the study of cancerogenesis in the murine colon. Beyond the descriptive use of murine endoscopy, we provide detailed instructions on the use of endoscopic instrumentation to obtain biopsies, and the topical and intramucosal application of different components of interest (e.g., drug candidates or tumor cells). Finally, we demonstrate the use of murine fluorescence endoscopy, which employs sophisticated molecular imaging techniques, in the setting of colorectal tumors.

<table border="0" cellpadding="0" cellspacing="0" width="1467">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:469px;">Name</td>
			<td style="width:423px;">Company</td>
			<td style="width:320px;">Catalogue Number</td>
			<td style="width:255px;">Comment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;"></td>
			<td style="width:423px;"></td>
			<td style="width:320px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:469px;">Reagents</td>
			<td style="width:423px;"></td>
			<td style="width:320px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Alfalfa-free diet</td>
			<td>Harlan Laboritories, Madison, USA</td>
			<td style="width:320px;">2014</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Azoxymethane (AOM)</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">A5486</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bepanthen eye ointment</td>
			<td style="width:423px;">Bayer, Leverkusen, Germany</td>
			<td style="width:320px;">80469764</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dextran sulphate sodium (DSS)</td>
			<td>TdB Consulatancy, Uppsala, Sweden</td>
			<td>DB001</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Eosin</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">E 4382</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Ethylenediaminetetraacetic acid (EDTA)&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">E 9884</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Falcon Tube 50ml</td>
			<td>BD Biosciences, Erembodegem, Belgium</td>
			<td style="width:320px;">352070</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Florene 100V/V</td>
			<td>Abbott, Wiesbaden, Germany</td>
			<td style="width:320px;">B506</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fluorescein-Isothiocyanat (FITC)&#8211;dextrane&#160;</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">FD4-250MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:469px;">Haematoxylin&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">HHS32-1L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:469px;">Isopentane (2- Methylbutane)</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">M32631-1L</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Methylene blue</td>
			<td style="width:423px;">Merck, Darmstadt, Germany</td>
			<td style="width:320px;">1159430025</td>
			<td></td>
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			<td height="21" style="height:21px;width:469px;">O.C.T. Tissue Tek compound&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:423px;">Sakura, Zoeterwonde, Netherlands</td>
			<td style="width:320px;">4583</td>
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			<td height="21" style="height:21px;width:469px;">Omnican F - canula</td>
			<td style="width:423px;">Braun, Melsungen, Germany</td>
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			<td height="21" style="height:21px;width:469px;">Phosphate buffered saline, PBS</td>
			<td style="width:423px;">Lonza, Verviers, Belgium</td>
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			<td></td>
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			<td height="20" style="height:20px;">Sodium Chloride 0,9%</td>
			<td>Braun, Melsungen, Germany</td>
			<td style="width:320px;">5/12211095/0411</td>
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			<td>Altromin, Lage, Germany</td>
			<td style="width:320px;">1320</td>
			<td></td>
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			<td height="20" style="height:20px;">Tissue-Tek Cryomold</td>
			<td>Sakura, Leiden, Netherlands</td>
			<td style="width:320px;">4566</td>
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			<td height="21" style="height:21px;width:469px;">Vitro &#8211; Clud&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:423px;">R. Langenbrinck, Teningen, Germany</td>
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			<td height="20" style="height:20px;">AIDA Control</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">20 096020</td>
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			<td>Semrock, Rochester, USA</td>
			<td style="width:320px;">HC 716/40</td>
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			<td height="20" style="height:20px;">Bandpass filter</td>
			<td>Semrock, Rochester, USA</td>
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		<tr height="20">
			<td height="20" style="height:20px;">Biopsy Forceps, 3 Fr., 28cm</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">61071ZJ</td>
			<td></td>
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			<td height="20" style="height:20px;">Dell Monitor</td>
			<td>Dell, Frankfurt am Main, Germany</td>
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			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">61029D</td>
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			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">61029C</td>
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			<td height="20" style="height:20px;">Fiber Optic Light Cable, 3.5mm</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">69495NL</td>
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			<td height="20" style="height:20px;">Fluorescein Blue Filter System</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">20100032</td>
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			<td height="20" style="height:20px;">Fluorescein Barrier Filter</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
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			<td height="20" style="height:20px;">Foot switch</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">20010430</td>
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			<td height="20" style="height:20px;">HOPKINS Telescope, 1.9mm, Length 10cm</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">1830231</td>
			<td></td>
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			<td height="20" style="height:20px;">SCB D-light P&#160;</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">20 133720</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;">SCB tricam SL II</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">20 2230 20</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tubing set instruments VETPUMP II</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">69811</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;">Tricam PDD PAL</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">20221037</td>
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			<td height="20" style="height:20px;">UniVet Porta</td>
			<td>Groppler Medizintechnik, Deggendorf, Germany</td>
			<td style="width:320px;">BKGM 0451</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;">Vetpump 2</td>
			<td>Karl Storz - Endoskope, Tuttlingen, Germany</td>
			<td style="width:320px;">69321620</td>
			<td></td>
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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.

In vivo monitoring of intestinal wound healing 
During routine endoscopy, mucosal wounds were induced mechanically by miniature biopsy forceps with a diameter of 3 French (equals 1 mm; Figure 1A). Subsequently, wound healing was monitored by daily endoscopic examinations and quantified by measurement of the residual wound area using image editing software, e.g., ImageJ (Figure 1B). The individual wound closure over time is expresse...

Watch this Scientific Journal Video about Murine Endoscopy for In Vivo Multimodal Imaging of Carcinogenesis and Assessment of Intestinal Wound Healing and Inflammation at JoVE.com

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.

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 ...

murine-endoscopy-for-vivo-multimodal-imaging-carcinogenesis

Universidad de Cartagena UDEC

Research

JoVE Journal

Medicine

18.5K Views.  University Hospital Münster. 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. 

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

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.

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.

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

Functional Assessment of Intestinal Motility and Gut Wall Inflammation in Rodents: Analyses in a Standardized Model of Intestinal Manipulation

Inflammation of the gastrointestinal tract is a common reason for a variety of human diseases. Animal research models are critical in investigating the complex cellular and molecular of intestinal pathology. Although the tunica mucosa is often the organ of interest in many inflammatory diseases, recent works demonstrated that the muscularis externa (ME) is also a highly immunocompetent organ that harbours a dense network of resident immunocytes.1,2 These works were performed within the standardized model of intestinal manipulation (IM) that leads to inflammation of the bowel wall, mainly limited to the ME. Clinically this inflammation leads to prolonged intestinal dysmotility, known as postoperative ileus (POI) which is a frequent and unavoidable complication after abdominal surgery.3 The inflammation is characterized by liberation of proinflammatory mediators such as IL-64 or IL-1&beta; or inhibitory neurotransmitters like nitric oxide (NO).5 Subsequently, tremendous numbers of immunocytes extravasate into the ME, dominated by polymorphonuclear neutrophils (PMN) and monocytes and finally maintain POI.2 Lasting for days, this intestinal paralysis leads to an increased risk of aspiration, bacterial translocation and infectious complications up to sepsis and multi organ failure and causes a high economic burden.6
In this manuscript we demonstrate the standardized model of IM and in vivo assessment of gastrointestinal transit (GIT) and colonic transit. Furthermore we demonstrate a method for separation of the ME from the tunica mucosa followed by immunological analysis, which is crucial to distinguish between the inflammatory responses in these both highly immunoactive bowel wall compartments. All analyses are easily transferable to any other research models, affecting gastrointestinal function.

Postoperative ileus (POI) is a complication of abdominal surgery leading to increased morbidity and a prolonged hospital stay. Because prophylactic or therapeutic strategies are lacking intensified research is necessary. Therefore we established a standardized and feasible mouse model to investigate the pathophysiology of POI and to study potential therapeutic options.

Inflammation of the gastrointestinal tract is a common reason for a variety of human diseases. Animal research models are critical in investigating the ...

Murine Model of Wound Healing

Wound healing and repair are the most complex biological processes that occur in human life. After injury, multiple biological pathways become activated. Impaired wound healing, which occurs in diabetic patients for example, can lead to severe unfavorable outcomes such as amputation. There is, therefore, an increasing impetus to develop novel agents that promote wound repair. The testing of these has been limited to large animal models such as swine, which are often impractical. Mice represent the ideal preclinical model, as they are economical and amenable to genetic manipulation, which allows for mechanistic investigation. However, wound healing in a mouse is fundamentally different to that of humans as it primarily occurs via contraction. Our murine model overcomes this by incorporating a splint around the wound. By splinting the wound, the repair process is then dependent on epithelialization, cellular proliferation and angiogenesis, which closely mirror the biological processes of human wound healing. Whilst requiring consistency and care, this murine model does not involve complicated surgical techniques and allows for the robust testing of promising agents that may, for example, promote angiogenesis or inhibit inflammation. Furthermore, each mouse acts as its own control as two wounds are prepared, enabling the application of both the test compound and the vehicle control on the same animal. In conclusion, we demonstrate a practical, easy-to-learn, and robust model of wound healing, which is comparable to that of humans.

A murine model of cutaneous wound healing that can be used to assess therapeutic compounds in physiological and pathophysiological settings.

Wound healing and repair are the most complex biological processes that occur in human life. After injury, multiple biological pathways become activated. ...

A Murine Model of Irreversible and Reversible Unilateral Ureteric Obstruction

Obstruction of the kidney may affect native or transplanted kidneys and results in kidney injury and scarring. Presented here is a model of obstructive nephropathy induced by unilateral ureteric obstruction (UUO), which can either be irreversible (UUO) or reversible (R-UUO). In the irreversible UUO model, the ureter may be obstructed for variable periods of time in order to induce increasingly severe renal inflammation and interstitial fibrotic scarring. In the reversible R-UUO model the ureter is obstructed to induce hydronephrosis, tubular dilation and inflammation. After a suitable period of time the ureteric obstruction is then surgically reversed by anastomosis of the severed previously obstructed ureter to the bladder in order to allow complete decompression of the kidney and restoration of urinary flow to the bladder. The irreversible UUO model has been used to investigate various aspects of renal inflammation and scarring including the pathogenesis of disease and the testing of potential anti-inflammatory or anti-fibrotic therapies. The more challenging model of R-UUO has been used by some investigators and does offer significant research potential as it allows the study of inflammatory and immune processes and tissue remodeling in an injured and scarred kidney following the removal of the injurious stimulus. As a result, the R-UUO model offers investigators the opportunity to explore the resolution of kidney inflammation together with key aspects of tissue repair. These experimental models are of relevance to human disease as patients often present with obstruction of the renal tract that requires decompression and are commonly left with significant residual kidney impairment that has no current treatment options and may lead to eventual end stage kidney failure.

The murine model of irreversible unilateral ureteric obstruction (UUO) is presented together with the model of reversible UUO in which the ureteric obstruction is relieved by anastomosis of the severed ureter into the bladder. These models enable the study of renal inflammation and scarring as well as tissue remodeling.

Obstruction of the kidney may affect native or transplanted kidneys and results in kidney injury and scarring. Presented here is a model of obstructive ...

Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation

Cardiovascular disease is the leading cause of morbidity and mortality in the world. Atherosclerotic plaques, consisting of lipid-laden macrophages and calcification, develop in the coronary arteries, aortic valve, aorta, and peripheral conduit arteries and are the hallmark of cardiovascular disease. In humans, imaging with computed tomography allows for the quantification of vascular calcification; the presence of vascular calcification is a strong predictor of future cardiovascular events. Development of novel therapies in cardiovascular disease relies critically on improving our understanding of the underlying molecular mechanisms of atherosclerosis. Advancing our knowledge of atherosclerotic mechanisms relies on murine and cell-based models. Here, a method for imaging aortic calcification and macrophage infiltration using two spectrally distinct near-infrared fluorescent imaging probes is detailed. Near-infrared fluorescent imaging allows for the ex vivo quantification of calcification and macrophage accumulation in the entire aorta and can be used to further our understanding of the mechanistic relationship between inflammation and calcification in atherosclerosis. Additionally, a method for isolating and culturing animal aortic vascular smooth muscle cells and a protocol for inducing calcification in cultured smooth muscle cells from either murine aortas or from human coronary arteries is described. This in vitro method of modeling vascular calcification can be used to identify and characterize the signaling pathways likely important for the development of vascular disease, in the hopes of discovering novel targets for therapy.

Vascular calcification is an important predictor of and contributor to human cardiovascular disease. This protocol describes methods for inducing calcification of cultured primary vascular smooth muscle cells and for quantifying calcification and macrophage burden in animal aortas using near-infrared fluorescence imaging.

Cardiovascular disease is the leading cause of morbidity and mortality in the world.  Atherosclerotic plaques, consisting of lipid-laden macrophages and ...

Multimodal Quantitative Phase Imaging with Digital Holographic Microscopy Accurately Assesses Intestinal Inflammation and Epithelial Wound Healing

The incidence of inflammatory bowel disease, i.e., Crohn&#39;s disease and Ulcerative colitis, has significantly increased over the last decade. The etiology of IBD remains unknown and current therapeutic strategies are based on the unspecific suppression of the immune system. The development of treatments that specifically target intestinal inflammation and epithelial wound healing could significantly improve management of IBD, however this requires accurate detection of inflammatory changes. Currently, potential drug candidates are usually evaluated using animal models in vivo or with cell culture based techniques in vitro. Histological examination usually requires the cells or tissues of interest to be stained, which may alter the sample characteristics and furthermore, the interpretation of findings can vary by investigator expertise. Digital holographic microscopy (DHM), based on the detection of optical path length delay, allows stain-free quantitative phase contrast imaging. This allows the results to be directly correlated with absolute biophysical parameters. We demonstrate how measurement of changes in tissue density with DHM, based on refractive index measurement, can quantify inflammatory alterations, without staining, in different layers of colonic tissue specimens from mice and humans with colitis. Additionally, we demonstrate continuous multimodal label-free monitoring of epithelial wound healing in vitro, possible using DHM through the simple automated determination of the wounded area and simultaneous determination of morphological parameters such as dry mass and layer thickness of migrating cells. In conclusion, DHM represents a valuable, novel and quantitative tool for the assessment of intestinal inflammation with absolute values for parameters possible, simplified quantification of epithelial wound healing in vitro and therefore has high potential for translational diagnostic use.

Accurate assessment of anti-inflammatory effects is of utmost importance for the evaluation of potential new drugs for the treatment of inflammatory bowel disease. Digital holographic microscopy provides assessment of inflammation in murine and human colonic tissue samples as well as automated multimodal evaluation of epithelial wound healing in vitro.

The incidence of inflammatory bowel disease, i.e., Crohn&#39;s disease and Ulcerative colitis, has significantly increased over the last decade. The ...

Fluorescence-mediated Tomography for the Detection and Quantification of Macrophage-related Murine Intestinal Inflammation

Murine models of disease are indispensable to scientific research. However, many diagnostic tools such as endoscopy or tomographic imaging are not routinely employed in animal models. Conventional experimental readouts often rely on post mortem and ex vivo analyses, which prevent intra-individual follow-up examinations and increase the number of study animals needed. Fluorescence-mediated tomography enables the non-invasive, repetitive, quantitative, three-dimensional assessment of fluorescent probes. It is highly sensitive and permits the use of molecular makers, which allows for the specific detection and characterization of distinct molecular targets. In particular, targeted probes represent an innovative tool for analyzing gene activation and protein expression in inflammation, autoimmune disease, infection, vascular disease, cell migration, tumorigenesis, etc. In this article, we provide step-by-step instructions on this sophisticated imaging technology for the in vivo detection and characterization of inflammation (i.e., F4/80-positive macrophage infiltration) in a widely used murine model of intestinal inflammation. This technique might also be used in other research areas, such as immune cell or stem cell tracking.

Target-specific probes represent an innovative tool for analyzing molecular mechanisms, such as protein expression in various types of disease (e.g., inflammation, infection, and tumorigenesis). In this study, we describe a quantitative three-dimensional tomographic assessment of intestinal macrophage infiltration in a murine model of colitis using F4/80-specific fluorescence-mediated tomography.

Murine models of disease are indispensable to scientific research. However, many diagnostic tools such as endoscopy or tomographic imaging are not ...

Microscopy Based Methods for the Assessment of Epithelial Cell Migration During In Vitro Wound Healing

Cell migration is a mandatory aspect for wound healing. Creating artificial wounds on research animal models often results in costly and complicated experimental procedures, while potentially lacking in precision. In vitro culture of epithelial cell lines provides a suitable platform for researching the cell migratory behavior in wound healing and the impact of treatments on these cells. The physiology of epithelial cells is often studied in non-confluent conditions; however, this approach may not resemble natural wound healing conditions. Disrupting the epithelium integrity by mechanical means generates a realistic model, but may impede the application of molecular techniques. Consequently, microscopy based techniques are optimal for studying epithelial cell migration in vitro. Here we detail two specific methods, the artificial wound scratch assay and the artificial migration front assay, that can obtain quantitative and qualitative data, respectively, on the migratory performance of epithelial cells.

Microscopy Based Methods for the Assessment of Epithelial Cell Migration During  In Vitro Wound Healing

This manuscript describes how incision-like lesions made on cultured epithelial cell monolayers conveniently model wound healing in vitro, allowing for imaging by confocal or laser scanning microscopy, and which can provide high-quality quantitative and qualitative data for studying both cell behavior and the mechanisms involved in migration.

Cell migration is a mandatory aspect for wound healing. Creating artificial wounds on research animal models often results in costly and complicated ...

Corneal Epithelial Abrasion with Ocular Burr As a Model for Cornea Wound Healing

The murine cornea provides an excellent model to study wound healing. The cornea is the outermost layer of the eye, and thus is the first defense to injury. In fact, the most common type of eye injury found in clinic is a corneal abrasion. Here, we utilize an ocular burr to induce an abrasion resulting in removal of the corneal epithelium in vivo on anesthetized mice. This method allows for targeted and reproducible epithelial disruption, leaving other areas intact. In addition, we describe the visualization of the abraded epithelium with fluorescein staining and provide concrete advice on how to visualize the abraded cornea. Then, we follow the timeline of wound healing 0, 18, and 72 h after abrasion, until the wound is re-epithelialized. The epithelial abrasion model of corneal injury is ideal for studies on epithelial cell proliferation, migration and re-epithelialization of the corneal layers. However, this method is not optimal to study stromal activation during wound healing, because the ocular burr does not penetrate to the stromal cell layers. This method is also suitable for clinical applications, for example, pre-clinical test of drug effectiveness.

This protocol describes a method to inflict an abrasion to the ocular surface of the mouse, and to follow the wound healing process thereafter. The protocol takes advantage of an ocular burr to partially remove the surface epithelium of the eye in anaesthetized mice.

The murine cornea provides an excellent model to study wound healing. The cornea is the outermost layer of the eye, and thus is the first defense to ...

Ex Vivo Corneal Organ Culture Model for Wound Healing Studies

The cornea has been used extensively as a model system to study wound healing. The ability to generate and utilize primary mammalian cells in two dimensional (2D) and three dimensional (3D) culture has generated a wealth of information not only about corneal biology but also about wound healing, myofibroblast biology, and scarring in general. The goal of the protocol is an assay system for quantifying myofibroblast development, which characterizes scarring. We demonstrate a corneal organ culture ex vivo model using pig eyes. In this anterior keratectomy wound, corneas still in the globe are wounded with a circular blade called a trephine. A plug of approximately 1/3 of the anterior cornea is removed including the epithelium, the basement membrane, and the anterior part of the stroma. After wounding, corneas are cut from the globe, mounted on a collagen/agar base, and cultured for two weeks in supplemented-serum free medium with stabilized vitamin C to augment cell proliferation and extracellular matrix secretion by resident fibroblasts. Activation of myofibroblasts in the anterior stroma is evident in the healed cornea. This model can be used to assay wound closure, the development of myofibroblasts and fibrotic markers, and for toxicology studies. In addition, the effects of small molecule inhibitors as well as lipid-mediated siRNA transfection for gene knockdown can be tested in this system.

A protocol for an ex vivo corneal organ culture model useful for wound healing studies is described. This model system can be used to assess the effects of agents to promote regenerative healing or drug toxicity in an organized 3D multicellular environment.

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

Summary

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Chapters in this video

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

Functional Assessment of Intestinal Motility and Gut Wall Inflammation in Rodents: Analyses in a Standardized Model of Intestinal Manipulation

Murine Model of Wound Healing

A Murine Model of Irreversible and Reversible Unilateral Ureteric Obstruction

Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation

Multimodal Quantitative Phase Imaging with Digital Holographic Microscopy Accurately Assesses Intestinal Inflammation and Epithelial Wound Healing

Fluorescence-mediated Tomography for the Detection and Quantification of Macrophage-related Murine Intestinal Inflammation

Microscopy Based Methods for the Assessment of Epithelial Cell Migration During In Vitro Wound Healing

Corneal Epithelial Abrasion with Ocular Burr As a Model for Cornea Wound Healing

Ex Vivo Corneal Organ Culture Model for Wound Healing Studies