The authors thank Pertti Panula for the access to the Zebrafish unit and Henri Koivula for the guidance and help with the zebrafish experiments. This research was supported by the Academy of Finland, the Jane and Aatos Erkko Foundation, the Finnish Cultural Foundation, and the ATIP-Avenir Program. Imaging was performed at the Electron Microscopy unit and the Light Microscopy Unit, Institute of Biotechnology, supported by HiLIFE and Biocenter Finland.

All experiments were approved by the national animal experiment board.
1. Preparations
<ol>
	<li>Prepare the tricaine stock solution used for anesthesia26 in advance (0.4% stock solution used in this protocol). Use gloves and keep the materials in a fume hood whenever possible.
	<ol>
		<li>For 50 mL of a 0.4% solution, weigh 200 mg of tricaine powder into a 50 mL tube. Dissolve the powder in approximately 45 mL of double-distilled water.</li>
		<li>Adjust the pH of the tricaine stock solution to 7 with 1 M Tris (pH 8.8, ~1.25 mL). Add the Tris solution to the tricaine stock in aliquots, mix the stock thoroughly after each aliquot, and check the pH after each addition of Tris.</li>
	</ol>
	</li>
	<li>Before the experiment, prepare a 0.02% working solution of tricaine.
	<ol>
		<li>Thaw 2 mL of 0.4% stock solution and add to 40 mL of system water (final concentration 0.02%). Place the solution in a small container.</li>
	</ol>
	</li>
	<li>Before the experiment, prepare the recovery water containing analgesic. Use gloves and keep the materials in fume hood whenever possible.
	<ol>
		<li>For one liter of recovery water, weigh 2.5 mg of lidocaine hydrochloride powder and dissolve it in fresh system water. Check the pH and adjust to 7 if necessary.</li>
	</ol>
	</li>
	<li>Before the experiment, prepare the fixing solution (2.5% glutaraldehyde in 0.1 M sodium phosphate (Na-PO4) solution at pH 7.4). Use gloves and keep the materials in a fume hood.
	<ol>
		<li>For 10 mL of the fixing solution, pipette 5 mL of 0.2 M Na-PO4 into a tube. Add 0.5 mL of 50% glutaraldehyde, and add double-distilled water to obtain the final volume of 10 mL. Protect the solution from light, and keep it on ice or in the fridge prior to use. 
		NOTE: If samples must be collected for several hours after wounding, prepare the fixing solution just prior to use.</li>
	</ol>
	</li>
	<li>Prepare the equipment for wounding (Figure 1).
	<ol>
		<li>Fill the recovery tanks or smaller containers with system water.</li>
		<li>Have the ophthalmic burr ready. Check that the burr tip is clean. If needed, remove cell debris with a moist cotton swab.</li>
		<li>Make an incision to the side of a soft sponge, and moisten the sponge with system water. Place the sponge on the base/stage of a dissecting microscope. Ensure enough working space for using the burr and enough illumination from the sides and/or above to see the eye surface properly.</li>
	</ol>
	</li>
</ol>
2. Anesthesia
<ol>
	<li>Transfer a fish from the tank to the 0.02% tricaine solution with a net as gently as possible.</li>
	<li>Monitor the anesthesia, checking for lack of response to light mechanical stimulus. 
	NOTE: For consistent anesthesia, a 2 min exposure to tricaine is used prior to abrasion with adult wild-type AB fish. With fish of other genetic background, a different duration may be needed.</li>
</ol>
3. Abrasion
<ol>
	<li>Gently place the anesthetized fish with a spoon into the incision on the sponge, head protruding from the sponge surface.</li>
	<li>Turn on the burr, and focus the microscope view onto the eye surface.</li>
	<li>Carefully approach the eye surface with the burr tip. When touching the eye surface, start moving the burr tip on the eye surface with circular motion. Avoid sudden movement, as it might lead to the eye tilting in the socket and the burr tip to slip.</li>
	<li>When the abrasion is done, carefully place the fish in system water containing the analgesic for recovery.</li>
	<li>Clean the burr right after use with a moist cotton swab.</li>
</ol>
4. Collecting samples
<ol>
	<li>At the desired time point, pick the fish up with a net and place it in 0.02% tricaine solution. Keep the animal in the solution until the opercular movement has ceased completely, and the fish does not react to touching.</li>
	<li>Place the fish on a Petri dish with a spoon, and hold it with tweezers. Decapitate the fish with dissecting scissors. Avoid making any scratches on the eye surface when handling the sample.</li>
	<li>Put the tissue into a sample tube containing 0.1 M Na-PO4.
	<ol>
		<li>Rinse the tissue by replacing the 0.1 M Na-PO4 with clean buffer so that no blood remains in the solution.</li>
	</ol>
	</li>
</ol>
5. Sample processing for electron microscopy
<ol>
	<li>Fix the tissue in 2.5% glutaraldehyde/0.1 M Na-PO4 (pH 7.4) for ~24 h at +4 &#176;C. Keep the sample on a rotating/shaking sample holder to ensure proper fixation.</li>
	<li>Remove the fixing solution and rinse the sample several times with 0.1 M Na-PO4.</li>
	<li>Dissect the sample at this point.
	<ol>
		<li>Place the sample onto a drop of 0.1 M Na-PO4 on a dissecting plate. If both eyes from the same fish must be imaged, cut the head sample into two with fine dissecting scissors.</li>
		<li>Alternatively, collect the eyes only by carefully placing the tips of fine tweezers into the eye socket from the side of the eye, taking extra care not to scratch the eye surface. Then, pull the eye out from the socket.</li>
		<li>Transfer the dissected sample into a tube containing 0.1 M Na-PO4. Ensure there is no extra tissue in the sample tube, as it may adhere to the top of the eye during sample processing.</li>
	</ol>
	</li>
	<li>Store the sample in 0.1 M Na-PO4 (maximum one week) at +4 &#176;C.</li>
	<li>Process the samples for electron microscopy imaging.
	<ol>
		<li>Postfix the samples in 2% osmium tetroxide in 0.1 M Na-PO4 buffer for 1 h at room temperature (RT).</li>
		<li>Wash the samples 3 times for 5 minutes each wash in 0.1 M Na-PO4 at RT.</li>
		<li>Dehydrate the samples successively in 30%, 50%, and 70% ethanol for 1 h in each solution at RT.</li>
		<li>Immerse the samples in 96% ethanol for 2-3 h at RT.</li>
		<li>Next, incubate the samples two times in 100% ethanol, first for 1 h and then in fresh 100% ethanol overnight at +4 &#176;C.</li>
		<li>Subject the samples to 30 cycles in an automated critical point dryer.</li>
	</ol>
	</li>
	<li>Embed and platinum-coat the samples.
	<ol>
		<li>Place an adhesive tab onto a mount. If the sample must be marked on top of the mount, leave a piece of tab cover paper on the tab and write the sample ID on the paper.</li>
		<li>Place the mount with the tab on the base of a dissecting microscope.</li>
		<li>Gently place the tissue sample on the mount with fine tweezers, cornea facing up.</li>
		<li>Coat the specimen with platinum using the appropriate device. After coating, store the samples at room temperature until imaging.</li>
	</ol>
	</li>
</ol>
6. Imaging (Figure 2)
<ol>
	<li>Operate the devices as advised in the user&#39;s manual and by imaging experts.</li>
	<li>Acquire images of the desired magnification, and use 2,000-2,500x images for analysis.</li>
	<li>Adjust the brightness and contrast so that there are no overexposed areas in the image, and cell borders and microridges are seen as clearly as possible. 
	NOTE: The position and angle of the tissue affect the brightness and contrast settings. They may need to be adjusted from sample to sample and between different regions of the tissue.</li>
</ol>
7. Measuring cell shape, size, and microridge pattern
<ol>
	<li>Open the TIFF image in Fiji ImageJ 1.5327. Set the scale using the scale bar of the image: create a line equal in size to the scale bar with the Line tool. Select Analyze | Set scale, and type in the known distance. Open the ROI manager from the Analyze | Tools menu.</li>
	<li>For cell size and roundness, select Analyze | Set measurements | Shape descriptors. Use the Magnifying glass tool to see the cells under magnification. Select cells with the Polygon tool, and add each selection to the ROI manager. Finally, measure the selected cells, and save the measurement.</li>
	<li>Microridge analysis (Figure 3 and Figure 4)
	<ol>
		<li>Ensure that the image is in 8-bit format from the Image | Type menu.</li>
		<li>Select a cell with the Polygon tool, and clear the background from Edit | Clear outside.</li>
		<li>Smoothen the image one to three times by selecting Process | Smooth, and adjust the brightness and contrast from Image | Adjust | Brightness/Contrast so that the microridges stand out as clearly as possible.</li>
		<li>Convolve the image from Process | Filters | Convolve, turn into binary from Process | Binary | Make binary, and skeletonize the black-and-white image by selecting Process | Binary | Skeletonize.</li>
		<li>Use the Analyze skeleton function in the Analyze | Skeleton menu to measure the microridge parameters and save the values. 
		NOTE: In SEM, individual images may differ in brightness and contrast. Thus, the steps in the analysis may need adjustments from image to image.</li>
	</ol>
	</li>
</ol>

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R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ABCB5+is+a+limbal+stem+cell+gene+required+for+corneal+development+and+repair.">ABCB5 is a limbal stem cell gene required for corneal development and repair.</a> Nature. 511 (7509), 353-357 (2014).</li><li>Pan, Y. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrabow:+multispectral+cell+labeling+for+cell+tracing+and+lineage+analysis+in+zebrafish.">Zebrabow: multispectral cell labeling for cell tracing and lineage analysis in zebrafish.</a> Development. 140 (13), 2835-2846 (2013).</li></ol>

The authors have no conflicts of interest to disclose.

Corneal physical injuries are the most common cause of ophthalmology patient visits to the hospital. Therefore, it is important to establish relevant models for the study of different aspects of corneal pathophysiology. So far, the mouse is the most commonly used model for the study of corneal wound healing. However, adding eyedrops on murine wounded eyes to validate the impact of specific drugs on corneal wound healing can be difficult. In this respect, the zebrafish model is particularly useful for the pharmacological ...

As most of the epithelia are in contact with the external environment, they are prone to physical injury, making them well suited for the study of wound healing processes. Among the well-studied tissues, the cornea is an extremely useful model in the investigation of the cellular and molecular aspects of wound healing. As a transparent external surface, it provides physical protection to the eye and is the first element to focus the light onto the retina. While the structure and cell composition of the retina differ between species1, these elements of the cornea are generally similar in all camera-type eyes, regardless of species.
The cornea is composed of three main layers2. The first and outermost layer is the epithelium, which is constantly renewed to ensure its transparency. The second layer is the stroma, which contains scattered cells, called keratocytes, within a thick layer of strictly organized collagen fibers. The third and innermost layer is the endothelium, which allows nutrient and liquid diffusion from the anterior chamber to the outer layers. The epithelial and stromal cells interact via growth factors and cytokines3. This interaction is highlighted by the rapid apoptosis and subsequent proliferation of keratocytes after epithelial injury4,5. In case of a deeper wound, such as a puncture, keratocytes take an active part in the healing process6.
Being in contact with the external environment, corneal physical injuries are common. Many of them are caused by small foreign objects7, such as sand or dust. The reflex of eye rubbing can lead to extensive epithelial abrasions and corneal remodelling8. According to wound size and depth, these physical injuries are painful and take several days to heal9. The optimal wound healing characteristics of a model facilitate the understanding of the cellular and molecular aspects of wound closure. Furthermore, such models have also proved useful for testing new molecules with the potential to accelerate corneal healing, as previously demonstrated10,11.
The protocol described here aims to use zebrafish as a relevant model to study corneal physical injury. This model is highly convenient for pharmacological screening studies as it allows molecules to be added directly to the tank water and, therefore, to come into contact with a healing cornea. The details provided here will help scientists perform their studies on the zebrafish model. The in vivo injury is performed with a dulled ocular burr. The impact on epithelial cells adjoining or at a distance from it can be analyzed by specifically removing the central corneal epithelium. In recent years, numerous reports focused on such a method on rodent cornea12,13,14,15,16,17; however, to date, only a single report has applied this method to zebrafish18.
Because of its simplicity, the physical wound is useful in delineating the role of epithelial cells in wound closure. Another well-established model of corneal injury is the chemical burn, especially the alkali burn19,20,21. However, such an approach indirectly damages the entire eye surface, including the peripheral cornea and corneal stroma19. Indeed, alkali burns potentially induce corneal ulcers, perforations, epithelial opacification, and swift neovascularization22, and the uncontrollable outcome of alkali burns disqualifies that approach for general wound healing studies. Numerous other methods are also used to investigate corneal wound healing according to the particular focus of the study in question (e.g., complete epithelial debridement23, the combination of chemical and mechanical injury for partial-thickness wound24, excimer laser ablation for wounds extending to the stroma25). The use of an ocular burr restricts the focal point to the epithelial response to the wound and provides a highly reproducible wound.
As with each method of wound infliction, the use of an ocular burr has advantages and disadvantages. The main disadvantage is that the response being mostly epithelial, it does not perfectly reflect the abrasions seen in the clinical setting. However, this method has numerous advantages, including the ease with which it can be set up and performed, its precision, its reproducibility, and the fact that it is noninvasive, making it a method well tolerated by animals.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >0.1M Na-PO4 (sodium phosphate buffer), pH 7.4</td>
			<td >in-house</td>
			<td ></td>
			<td >Solution is prepared from 1M sodium phosphate buffer (1M Na2HPO4 adjusted to pH 7.4 with 1M NaH2PO4).</td>
		</tr>
		<tr >
			<td >0.2M Na-PO4 (sodium phosphate buffer), pH 7.4</td>
			<td >in-house</td>
			<td ></td>
			<td >Solution is prepared from 1M sodium phosphate buffer (1M Na2HPO4 adjusted to pH 7.4 with 1M NaH2PO4).</td>
		</tr>
		<tr >
			<td >0.5mm burr tips</td>
			<td >Alger Equipment Company</td>
			<td >BU-5S</td>
			<td></td>
		</tr>
		<tr >
			<td >1M Tris, pH 8.8</td>
			<td >in-house</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >adhesive tabs</td>
			<td >Agar Scientific</td>
			<td >G3347N</td>
			<td></td>
		</tr>
		<tr >
			<td >Algerbrush burr, Complete instrument</td>
			<td >Alger Equipment Company</td>
			<td >BR2-5</td>
			<td></td>
		</tr>
		<tr >
			<td >Cotton swaps</td>
			<td >Heinz Herenz Hamburg</td>
			<td >1030128</td>
			<td></td>
		</tr>
		<tr >
			<td >Dissecting plate</td>
			<td >in-house</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >Dissecting tools</td>
			<td >Fine Science Tools</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >double-distilled water</td>
			<td >in-house</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >Eppedorf tubes, 2ml</td>
			<td >any provider</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >Ethyl 3-aminobenzoate methanesulfonate salt</td>
			<td >Sigma</td>
			<td >A5040</td>
			<td>Caution: causes irritation.</td>
		</tr>
		<tr >
			<td >Glutaraldehyde, 50% aqueous solution, grade I</td>
			<td >Sigma</td>
			<td >G7651</td>
			<td>Caution: toxic.</td>
		</tr>
		<tr >
			<td >Lidocaine hydrochloride</td>
			<td >Sigma</td>
			<td >L5647</td>
			<td>Caution: toxic.</td>
		</tr>
		<tr >
			<td >mounts</td>
			<td >Agar Scientific</td>
			<td >G301P</td>
			<td></td>
		</tr>
		<tr >
			<td >Petri dish</td>
			<td >Thermo Scientific</td>
			<td >101VR20</td>
			<td></td>
		</tr>
		<tr >
			<td >pH indicator strips</td>
			<td >Macherey-Nagel</td>
			<td >92110</td>
			<td></td>
		</tr>
		<tr >
			<td >Plastic spoons</td>
			<td >any provider</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >Plastic tubes, 15 ml</td>
			<td >Greiner Bio-One</td>
			<td >188271</td>
			<td></td>
		</tr>
		<tr >
			<td >Plastic tubes, 50 ml</td>
			<td >Greiner Bio-One</td>
			<td >227261</td>
			<td></td>
		</tr>
		<tr >
			<td >Scanning electron microscope</td>
			<td >FEI</td>
			<td >Quanta 250 FEG</td>
			<td></td>
		</tr>
		<tr >
			<td >Soft sponge</td>
			<td >any provider</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >Sputter coater</td>
			<td >Quorum Technologies</td>
			<td >GQ150TS</td>
			<td></td>
		</tr>
		<tr >
			<td >Stereomicroscope</td>
			<td >Leica</td>
			<td ></td>
			<td></td>
		</tr>
	</tbody>
</table>

zebrafish corneal wound healing: from abrasion to wound closure imaging analysis

As the transparent surface of the eye, the cornea is instrumental for clear sight. Due to its location, this tissue is prone to environmental insults. Indeed, the eye injuries most frequently encountered clinically are those to the cornea. While corneal wound healing has been extensively studied in small mammals (i.e., mice, rats, and rabbits), corneal physiology studies have neglected other species, including zebrafish, despite zebrafish being a classic research model.
This report describes a method of performing a corneal abrasion on zebrafish. The wound is performed in vivo on anesthetized fish using an ocular burr. This method allows for a reproducible epithelial wound, leaving the rest of the eye intact. After abrasion, wound closure is monitored over the course of 3 h, after which the wound is reepithelialized. By using scanning electron microscopy, followed by image processing, the epithelial cell shape, and apical protrusions can be investigated to study the various steps during corneal epithelial wound closure.
The characteristics of the zebrafish model permit study of the epithelial tissue physiology and the collective behavior of the epithelial cells when the tissue is challenged. Furthermore, the use of a model deprived of the influence of the tear film can produce&#160;new answers regarding corneal response to stress. Finally, this model also allows the delineation of the cellular and molecular events involved in any epithelial tissue subjected to a physical wound. This method can be applied to the evaluation of drug effectiveness in preclinical testing.

This study describes a method using an ophthalmic burr in zebrafish corneal wound healing experiments. The method is modified from previous studies on mice, where the burr was shown to remove the epithelial cell layers efficiently13. The challenges in zebrafish corneal wounding include the relatively small size of the eye, and in the case of time-consuming experiments, the need to maintain a constant water flow through the gills (as described by Xu and colleagues28). The ma...

Watch this Scientific Journal Video about Zebrafish Corneal Wound Healing: From Abrasion to Wound Closure Imaging Analysis at JoVE.com

Zebrafish Corneal Wound Healing: From Abrasion to Wound Closure Imaging Analysis

This protocol focuses on damaging the ocular surface of zebrafish through abrasion to assess the subsequent wound closure at the cellular level. This approach exploits an ocular burr to partly remove the corneal epithelium and uses scanning electron microscopy to track changes in cell morphology during wound closure.

As the transparent surface of the eye, the cornea is instrumental for clear sight. Due to its location, this tissue is prone to environmental insults. ...

zebrafish-corneal-wound-healing-from-abrasion-to-wound-closure

Research

JoVE Journal

Biology

2.8K Views.  University of Helsinki. Corneatransparantie is instrumenteel voor helder zicht. In pathologische context kan deze transparantie een uitdaging zijn. Het bestuderen van pathogenesemechanisme vereist eenvoudige modellen met een hoge gelijkenis met menselijke organen.In deze aspecten is zebravis een uitstekend model. En dit is de eerste gedetailleerde beschrijving van hoornvliesslijtage bij zebravissen. Deze techniek is een eenvoudige en snelle manier om oppervlaktetoegang tot het oog te induceren.De wonds...

Video: Zebrafish Corneal Wound Healing: From Abrasion to Wound Closure Imaging Analysis

RNA Isolation from Embryonic Zebrafish and cDNA Synthesis for Gene Expression Analysis

Many important and complex laboratory procedures require an input of high quality, intact RNA.  A degraded sample or the presence of impurities can lead to disastrous results in downstream experimental applications.  It is therefore, of utmost importance to use solid techniques with numerous safeguards and quality control checks to ensure a superior sample.  Herein, we detail a protocol to isolate total RNA from whole zebrafish embryos using a commercially available chemical denaturant and subsequent cleanup to remove traces of DNA and impurities using a commercial RNA isolation kit. As RNA is relatively unstable and easily prone to cleavage by RNAses, most protocols assay gene expression using a cDNA product that is directly synthesized from an RNA template. We detail a procedure to convert RNA into the more stable cDNA product using a commercially available kit. Throughout these procedures there are numerous quality control checks to ensure that the sample is not degraded or contaminated.  The end product of these protocols is cDNA that is suitable for microarray analysis, RT-PCR or long-term storage.    

The isolation of high quality, intact RNA is an essential step in many laboratory protocols. Here, we demonstrate RNA extraction from whole zebrafish embryos and cDNA synthesis for subsequent application in various experimental procedures including gene expression microarray analysis.

Many important and complex laboratory procedures require an input of high quality, intact RNA.  A degraded sample or the presence of impurities can lead ...

Development of automated imaging and analysis for zebrafish chemical screens. 

We demonstrate the application of image-based high-content screening (HCS) methodology to identify small molecules that can modulate the FGF/RAS/MAPK pathway in zebrafish embryos. The zebrafish embryo is an ideal system for in vivo high-content chemical screens. The 1-day old embryo is approximately 1mm in diameter and can be easily arrayed into 96-well plates, a standard format for high throughput screening. During the first day of development, embryos are transparent with most of the major organs present, thus enabling visualization of tissue formation during embryogenesis. The complete automation of zebrafish chemical screens is still a challenge, however, particularly in the development of automated image acquisition and analysis. We previously generated a transgenic reporter line that expresses green fluorescent protein (GFP) under the control of FGF activity and demonstrated their utility in chemical screens 1. To establish methodology for high throughput whole organism screens, we developed a system for automated imaging and analysis of zebrafish embryos at 24-48 hours post fertilization (hpf) in 96-well plates 2. In this video we highlight the procedures for arraying transgenic embryos into multiwell plates at 24hpf and the addition of a small molecule (BCI) that hyperactivates FGF signaling 3. The plates are incubated for 6 hours followed by the addition of tricaine to anesthetize larvae prior to automated imaging on a Molecular Devices ImageXpress Ultra laser scanning confocal HCS reader. Images are processed by Definiens Developer software using a Cognition Network Technology algorithm that we developed to detect and quantify expression of GFP in the heads of transgenic embryos. In this example we highlight the ability of the algorithm to measure dose-dependent effects of BCI on GFP reporter gene expression in treated embryos.

Development of automated imaging and analysis for zebrafish chemical screens.

We report the development of a system for automated imaging and analysis of zebrafish transgenic embryos in multiwell plates. This demonstrates the ability to measure dose dependent effects of a small molecule, BCI, on Fibroblast Growth Factor reporter gene expression and provide technology for establishing high-throughput zebrafish chemical screens.

We demonstrate the application of image-based high-content screening (HCS) methodology to identify small molecules that can modulate the FGF/RAS/MAPK ...

Live Imaging of Cell Extrusion from the Epidermis of Developing Zebrafish

Homeostatic maintenance of epithelial tissues requires the continual removal of damaged cells without disrupting barrier function. Our studies have found that dying cells send signals to their live neighbors to form and contract a ring of actin and myosin that ejects it out from the epithelial sheet while closing any gaps that might have resulted from its exit, a process termed cell extrusion1. The optical clarity of developing zebrafish provides an excellent system to visualize extrusion in living epithelia. Here we describe a method to induce and image extrusion in the larval zebrafish epidermis. To visualize extrusion, we inject a red fluorescent protein labeled probe for F-actin into one-cell stage transgenic zebrafish embryos expressing green fluorescent protein in the epidermis and induce apoptosis by addition of G418 to larvae. We then use time-lapse imaging on a spinning disc confocal microscope to observe actin dynamics and epithelial cell behaviors during the process of apoptotic cell extrusion. This approach allows us to investigate the extrusion process in live epithelia and will provide an avenue to study disease states caused by the failure to eliminate apoptotic cells.

Dying cells are extruded from epithelial tissues by concerted contraction of neighboring cells without disrupting barrier function. The optical clarity of developing zebrafish provides an excellent system to visualize extrusion in living epithelia. Here we describe methods to induce and image extrusion in the larval zebrafish epidermis at cellular resolution.

Homeostatic maintenance of epithelial tissues requires the continual removal of damaged cells without disrupting barrier function.  Our studies have found ...

Analysis of Embryonic and Larval Zebrafish Skeletal Myofibers from Dissociated Preparations

The zebrafish has proven to be a valuable model system for exploring skeletal muscle function and for studying human muscle diseases. Despite the many advantages offered by in vivo analysis of skeletal muscle in the zebrafish, visualizing the complex and finely structured protein milieu responsible for muscle function, especially in whole embryos, can be problematic. This hindrance stems from the small size of zebrafish skeletal muscle (60 &mu;m) and the even smaller size of the sarcomere. Here we describe and demonstrate a simple and rapid method for isolating skeletal myofibers from zebrafish embryos and larvae. We also include protocols that illustrate post preparation techniques useful for analyzing muscle structure and function. Specifically, we detail the subsequent immunocytochemical localization of skeletal muscle proteins and the qualitative analysis of stimulated calcium release via live cell calcium imaging. Overall, this video article provides a straight-forward and efficient method for the isolation and characterization of zebrafish skeletal myofibers, a technique which provides a conduit for myriad subsequent studies of muscle structure and function.

Zebrafish are an emerging system for modeling human disorders of the skeletal muscle. We describe a fast and efficient method to isolate skeletal muscle myofibers from embryonic and larval zebrafish. This method yields a high-density myofiber preparation suitable for study of single skeletal muscle fiber morphology, protein subcellular localization, and muscle physiology.

The zebrafish has  proven to be a valuable model system for exploring skeletal muscle function and  for studying human muscle diseases. Despite  the many ...

Visualizing Cytoplasmic Flow During Single-cell Wound Healing in Stentor coeruleus

Although wound-healing is often addressed at the level of whole tissues, in many cases individual cells are able to heal wounds within themselves, repairing broken cell membrane before the cellular contents leak out. The giant unicellular organism Stentor coeruleus, in which cells can be more than one millimeter in size, have been a classical model organism for studying wound healing in single cells. Stentor cells can be cut in half without loss of viability, and can even be cut and grafted together. But this high tolerance to cutting raises the question of why the cytoplasm does not simply flow out from the size of the cut. Here we present a method for cutting Stentor cells while simultaneously imaging the movement of cytoplasm in the vicinity of the cut at high spatial and temporal resolution. The key to our method is to use a &#34;double decker&#34; microscope configuration in which the surgery is performed under a dissecting microscope focused on a chamber that is simultaneously viewed from below at high resolution using an inverted microscope with a high NA lens. This setup allows a high level of control over the surgical procedure while still permitting high resolution tracking of cytoplasm.

Visualizing Cytoplasmic Flow During Single-cell Wound Healing in Stentor coeruleus

The giant ciliate Stentor coeruleus is a classical system for studying regeneration and wound healing in single cells.&#160;By imaging Stentor cells simultaneously at low and high magnification it is possible to measure cytoplasmic flows before, during, and after wounding.

Although wound-healing is often addressed at the level of whole tissues, in many cases individual cells are able to heal wounds within themselves, ...

Methods for Skin Wounding and Assays for Wound Responses in C. elegans

The C. elegans epidermis and cuticle form a simple yet sophisticated skin layer that can repair localized damage resulting from wounding. Studies of wound responses and repair in this model have illuminated our understanding of the cytoskeletal and genomic responses to tissue damage. The two most commonly used methods to wound the C. elegans adult skin are pricks with microinjection needles, and local laser irradiation. Needle wounding locally disrupts the cuticle, epidermis, and associated extracellular matrix, and may also damage internal tissues. Laser irradiation results in more localized damage. Wounding triggers a succession of readily assayed responses including elevated epidermal Ca2+ (seconds-minutes), formation and closure of an actin-containing ring at the wound site (1-2 hr), elevated transcription of antimicrobial peptide genes (2-24 hr), and scar formation. Essentially all wild type adult animals survive wounding, whereas mutants defective in wound repair or other responses show decreased survival. Detailed protocols for needle and laser wounding, and assays for quantitation and visualization of wound responses and repair processes (Ca dynamics, actin dynamics, antimicrobial peptide induction, and survival) are presented.

Methods for Skin Wounding and Assays for Wound Responses in C. elegans

The adult C. elegans skin is a tractable model for studies of epithelial wound responses, including wound closure, scar formation, and innate immunity.

The C. elegans epidermis and cuticle form a simple yet sophisticated skin layer that can repair localized damage resulting from wounding. Studies of wound ...

Nephrotoxin Microinjection in Zebrafish to Model Acute Kidney Injury

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid decline in renal function and development of the clinical syndrome known as acute kidney injury (AKI). Pharmacological agents used to treat medical circumstances ranging from bacterial infection to cancer, when administered individually or in combination with other drugs, can initiate AKI. Zebrafish are a useful animal model to study the chemical effects on renal function in vivo, as they form an embryonic kidney comprised of nephron functional units that are conserved with higher vertebrates, including humans. Further, zebrafish can be utilized to perform genetic and chemical screens, which provide opportunities to elucidate the cellular and molecular facets of AKI and develop therapeutic strategies such as the identification of nephroprotective molecules. Here, we demonstrate how microinjection into the zebrafish embryo can be utilized as a paradigm for nephrotoxin studies.

Renal injuries incurred from nephrotoxins, which include drugs ranging from antibiotics to chemotherapeutics, can result in complex disorders whose pathogenesis remains incompletely understood. This protocol demonstrates how zebrafish can be used for disease modeling of these conditions, which can be applied to the identification of renoprotective measures.

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid ...

Analysis of Beta-cell Function Using Single-cell Resolution Calcium Imaging in Zebrafish Islets

Pancreatic beta-cells respond to increasing blood glucose concentrations by secreting the hormone insulin. The dysfunction of beta-cells leads to hyperglycemia and severe, life-threatening consequences. Understanding how the beta-cells operate under physiological conditions and what genetic and environmental factors might cause their dysfunction could lead to better treatment options for diabetic patients. The ability to measure calcium levels in beta-cells serves as an important indicator of beta-cell function, as the influx of calcium ions triggers insulin release. Here we describe a protocol for monitoring the glucose-stimulated calcium influx in zebrafish beta-cells by using GCaMP6s, a genetically encoded sensor of calcium. The method allows monitoring the intracellular calcium dynamics with single-cell resolution in ex vivo mounted islets. The glucose-responsiveness of beta-cells within the same islet can be captured simultaneously under different glucose concentrations, which suggests the presence of functional heterogeneity among zebrafish beta-cells. Furthermore, the technique provides high temporal and spatial resolution, which reveals the oscillatory nature of the calcium influx upon glucose stimulation. Our approach opens the doors to use the zebrafish as a model to investigate the contribution of genetic and environmental factors to beta-cell function and dysfunction.

Beta-cell functionality is important for blood-glucose homeostasis, which is evaluated at single-cell resolution using a genetically encoded reporter for calcium influx.

Pancreatic beta-cells respond to increasing blood glucose concentrations by secreting the hormone insulin. The dysfunction of beta-cells leads to ...

A Murine Model of a Burn Wound Reconstructed with an Allogeneic Skin Graft

Trivial superficial wounds heal without complications by primary intention. Deep wounds, such as full thickness burns, heal by secondary intention and require surgical debridement and skin grafting. Successful integration of the donor graft into a recipient wound bed depends on timely recruitment of immune cells, robust angiogenic response and new extracellular matrix formation. The development of novel therapeutic agents, which target some key processes involved in wound healing, are hindered by the lack of reliable preclinical models with optimized objective assessment of wound closure. Here, we describe an inexpensive and reproducible model of experimental full thickness burn wound reconstructed with an allogeneic skin graft. The wound is induced on the dorsum surface of anaesthetized inbred wild type mice from the BALB/C and SKH1-Hrhr backgrounds. The burn is produced using a brass template measuring 10 mm in diameter, which is preheated to 80 &#176;C and delivered at a constant pressure for 20 s. Burn eschar is excised 24 hours after the injury and replaced with a full thickness graft harvested from the tail of a genetically similar donor mouse. No specialized equipment is required for the procedure and surgical techniques are straightforward to follow. The method may be effortlessly implemented and reproduced in most research settings. Certain limitations are associated with the model. Due to technical difficulties, the harvest of thinner split thickness skin grafts is not possible. The surgical method we describe here allows for the reconstruction of burn wounds using full thickness skin grafts. It may be used to carry out preclinical therapeutic testing.

The aim of this study was to develop a murine model of burn wound healing. A thermal burn was induced on the dorsal skin of mice using a preheated brass template. Burned tissue was debrided and overlaid with a skin graft harvested from the tail of a genetically similar donor mouse.

Trivial superficial wounds heal without complications by primary intention. Deep wounds, such as full thickness burns, heal by secondary intention and ...

Inhibition of Wound Epidermis Formation via Full Skin Flap Surgery During Axolotl Limb Regeneration

Classical experiments in salamander regenerative biology over the last century have long established that the wound epidermis is a crucial signaling structure that forms rapidly post-amputation and is required for limb regeneration. However, methods to study its precise function at the molecular level over the last decades have been limited due to a paucity of precise functional techniques and genomic information available in salamander model systems. Excitingly, the recent plethora of sequencing technologies coupled with the release of various salamander genomes and the advent of functional genetic testing methods, including CRISPR, makes it possible to re-visit these foundational experiments at unprecedented molecular resolution. Here, I describe how to perform the classically developed full skin flap (FSF) surgery in adult axolotls in order to inhibit wound epidermis formation immediately following amputation. The wound epidermis normally forms via distal migration of epithelial cells in the skin proximal to the amputation plane to seal off the wound from the outside environment. The surgery entails immediately suturing full thickness skin (which includes both epidermal and dermal layers) over the amputation plane to hinder epithelial cell migration and contact with the underlying damaged mesenchymal tissues. Successful surgeries result in the inhibition of blastema formation and limb regeneration. By combining this surgery method with contemporary downstream molecular and functional analyses, researchers can begin to uncover the molecular underpinnings of wound epidermis function and biology during limb regeneration.

This article describes how to perform a surgical method to inhibit wound epidermis formation during axolotl limb regeneration by immediately suturing full thickness skin over the amputation plane. This method allows researchers to investigate the functional roles of the wound epidermis during the early stages of limb regeneration.

Classical experiments in salamander regenerative biology over the last century have long established that the wound epidermis is a crucial signaling ...

Zebrafish Corneal Wound Healing: From Abrasion to Wound Closure Imaging Analysis

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