The study was funded by the Atomic Energy Council of Taiwan (Grant No. A-IE-01-03-02-02), Ministry of Science and Technology (Grant No. NMRPG3E6202-3), and Chang Gung Medical Research Project (Grant No. CMRPG3H1281).

All of the experimental procedures in animal studies were approved by the Research Ethics Committee at the Chang Gung Memorial Hospital and adhered to the ARVO statement for use of animals in ophthalmic and vision research.
1. Ex vivo wound healing model of the mouse corneal epithelium
<ol>
	<li>Preparation of the mice
	<ol>
		<li>Administer general anesthesia to C57BL/6 mice by intraperitoneal delivery of ketamine hydrochloride (80-100&#160;mg/kg of body weight) and xylazine (5-10 mg/kg of body weight).&#160;</li>
		<li>Ensure that general anesthesia is working by confirming loss of movement to a noxious stimulus and loss of righting reflex in mice.</li>
		<li>Fix the mice head by hand and apply topical anesthesia on both eyes with one drop of 0.5% proparacaine hydrochloride ophthalmic solution (Figure 1A). Disinfect the ocular surface and lids three times with 5% betadine.&#160;</li>
	</ol>
	</li>
	<li>Creation of murine corneal epithelial wound model 
	NOTE: Perform the below procedures under a stereomicroscope. The corneal wound was created in vivo, not ex vivo, to manipulate the eyeball better and close to the real-world situation. This is a terminal procedure; therefore, only clean instruments (not sterile technique) are&#160;required.&#160;
	<ol>
		<li>Mark the central cornea of the mouse using a skin biopsy punch (2 mm in diameter) to confirm a well-circumscribed and well-measurable area of the wound.</li>
		<li>Gently indent the punch over the central cornea to leave a circular mark (Figure 1B). Utilizing a hand-held corneal rust ring remover with a 0.5 mm burr, debride the corneal epithelium down to the Bowman&#39;s layer ensuring not to damage the latter (Figure 1C). Remove the residual, loose tissues inner to the wound margin with corneal forceps.</li>
		<li>Confirm the area of debridement with fluorescein staining (Figure 1D). To perform fluorescein staining, put a drop of normal saline onto a fluorescein paper to dissolve fluorescein, and then place the fluorescein-containing drop onto murine epithelial defect for visualizing it under Cobalt blue light.</li>
	</ol>
	</li>
	<li>Ex vivo culture of the murine corneal abrasion wound model.
	<ol>
		<li>For harvesting the murine eyeballs, proceed as follows.</li>
		<li>Sacrifice the mice by cervical dislocation after inducing anesthesia with 5% isoflurane in an induction chamber. Ensure that anesthesia is working by confirming the loss of movement to a noxious stimulus and loss of righting reflex in mice.</li>
		<li>Gently press with the tip of forceps at the superior and inferior orbital rims to push the eyeball out. Introduce the tip of the closed corneal scissors into the retrobulbar space along the inferior orbital wall, ensuring not to penetrate the eyeball.</li>
		<li>Hold the eyeball steady with 0.3 mm corneal forceps, and then cut off the optic nerve and periorbital soft tissue with corneal scissors to isolate the eyeball.</li>
		<li>For ex vivo culturing of murine eyeballs, proceed as follows.</li>
		<li>Prepare a 48-well plate with melted wax inside the well and wait for solidification. With the tip of conjunctiva forceps, create a round hole on the surface of solidified wax for accommodating the eyeballs.</li>
		<li>Place the harvested eyeballs directly onto the 48-well plate (Figure 1E) with wax-covered bottoms and sidewalls to establish stabilization (Figure 1F).</li>
		<li>Culture the eyeballs with Dulbecco&#39;s modified eagle medium (DMEM) containing 1% fetal bovine serum (FBS) in a humidified atmosphere of 5% CO2 at 37 &#176;C with or without antibiotics, depending on the purpose of the study. 
		NOTE: If the model is used for studying corneal epithelial wound healing, antibiotics would be required to prevent infection. However, if this model is used to evaluate the efficacy of antibiotics or mixed agents, prophylactic antibiotics would not be necessary.</li>
		<li>Immerse the ocular surface with the culture medium without causing the eyeball to float.</li>
		<li>Document the course of wound healing by fluorescein staining (step 1.2.3) and collecting photographs with a digital camera under Cobalt blue light. 
		&#8203;NOTE: In prospective experiments with mice models of mechanical corneal injury, those receiving corneal abrasion and tested further for the efficacy of therapeutic agents are viewed as an experimental group, and those receiving corneal abrasion without further treatment are regarded as a negative control group.</li>
	</ol>
	</li>
</ol>
2. In vivo rabbit model of corneal alkali injury
NOTE: In this model, an alkali burn injury is induced followed by mechanical debridement of the corneal epithelium to generate a well-defined and even wound area for subsequent quantification. Sterilize all instruments before use.
<ol>
	<li>Preparation of the rabbit with pre-operative analgesia, including intramuscular injection of systemic analgesics and topical eye drops.
	<ol>
		<li>Administer general anesthesia to New Zealand white rabbits by intramuscular injection of ketamine hydrochloride (35-44 mg/kg of body weight), mixed with xylazine (5-10 mg/kg of body weight) at the hind leg.</li>
		<li>After positioning the rabbit and covering it with a towel, apply topical anesthesia over the right eye with a drop of 0.5% proparacaine hydrochloride ophthalmic solution (Figure 2A) under a stereomicroscope.&#160;Disinfect the ocular surface and lids three times with 5% betadine.</li>
	</ol>
	</li>
	<li>Inducing alkali burn injury over the cornea
	<ol>
		<li>Place circular filter papers with a diameter of 8 mm (cut using an 8 mm punch) in a Petri dish. Using a dropper, add 0.5 N sodium hydroxide (NaOH) into the Petri dish to soak the filter papers. Drain excess NaOH solution from the filter papers before placing them onto the rabbit cornea. 
		CAUTION: 0.5 N NaOH may cause severe erosive injury to human tissues. Wear gloves when handling. If the skin or the eyes come in contact with NaOH droplets, irrigation with copious amounts of normal saline and medical help are required to reduce further damage.</li>
		<li>After opening the eyelids with a lid speculum and confirming that the rabbit nictitating membrane is not interfering with the insertion of filter paper (Figure 2B), place the circular filter paper soaked in 0.5 N NaOH onto the central cornea for 30 s, and then remove it with forceps (Figure 2C).</li>
		<li>After removing the filter paper, rinse the ocular surface with 10 mL of normal saline to wash out alkali material.</li>
	</ol>
	</li>
	<li>Completing corneal epithelial defect
	<ol>
		<li>Debride the corneal epithelium within the opacified area down to the Bowman&#39;s membrane using a corneal rust ring remover with a 0.5 mm burr (Figure 2D).</li>
		<li>Confirm the area of debridement with fluorescein staining under the Cobalt blue light and remove residual corneal epithelium using corneal forceps (Figure 2E).</li>
	</ol>
	</li>
	<li>Secure wound condition with tarsorrhaphy
	<ol>
		<li>Confirm that the nictitating membrane smoothly covers the ocular surface and corneal epithelial defect at the nasal side. Ensure that the nictitating membrane is not folded or distorted too much to interfere with the process of wound healing and the experiment.</li>
		<li>Perform a temporary tarsorrhaphy with or without topical agents using a 6-0 suture to protect the ocular surface and prevent the rabbit from scratching it (Figure 2F). Ensure that the suture for tarsorrhaphy is at 3-4 mm from upper and lower lid margins with 4-5 ties and longer knots to prevent the rabbit from breaking the sutures. 
		NOTE: If the experiment is not involved in an antibiotics study, topical agents with antibiotics could be considered.</li>
		<li>In this rabbit model, those receiving alkali burn and removal of corneal epithelium were regarded as the control group. 
		NOTE: In prospective experiments, the rabbits receiving alkali burn corneal injury and further treated with therapeutic agents is viewed as an experimental group. The rabbits receiving alkali burn treatment only, without further treatment, are regarded as a negative control group.</li>
	</ol>
	</li>
	<li>Post-operative analgesia and pain control
	<ol>
		<li>Assess the physiological condition and USDA pain levels for 7 days after the procedure, by monitoring pain and distress in the animals. Consider the use of tobramycin ointment and one drop of 0.5% proparacaine hydrochloride ophthalmic solution according to the result of the assessment. Administer Buprenorphine HCl (0.03 mg/kg) every 6-8 hours for&#160;3 days. 
		NOTE: For daily measurement of defect area and observation after surgery, the procedure belongs to USDA category D.</li>
	</ol>
	</li>
</ol>

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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dimensions+and+morphology+of+the+cornea+in+three+strains+of+mice.">Dimensions and morphology of the cornea in three strains of mice.</a> Investigative Ophthalmology &amp; Visual Science. 50 (8), 3648-3654 (2009).</li><li>Wang, X., 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=MANF+promotes+diabetic+corneal+epithelial+wound+healing+and+nerve+regeneration+by+attenuating+hyperglycemia-induced+endoplasmic+reticulum+stress.">MANF promotes diabetic corneal epithelial wound healing and nerve regeneration by attenuating hyperglycemia-induced endoplasmic reticulum stress.</a> Diabetes. 69 (6), 1264-1278 (2020).</li><li>Ma, X., 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=Corneal+epithelial+injury-induced+norepinephrine+promotes+Pseudomonas+aeruginosa+keratitis.">Corneal epithelial injury-induced norepinephrine promotes Pseudomonas aeruginosa keratitis.</a> Experimental Eye Research. 195, 108048 (2020).</li><li>Chan, M. F., Werb, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+corneal+injury.">Animal models of corneal injury.</a> Bio Protocol. 5 (13), 1516 (2015).</li><li>Lan, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetics+and+function+of+mesenchymal+stem+cells+in+corneal+injury.">Kinetics and function of mesenchymal stem cells in corneal injury.</a> Investigative Ophthalmology &amp; Visual Science. 53 (7), 3638-3644 (2012).</li><li>Watanabe, M., 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=Promotion+of+corneal+epithelial+wound+healing+in+vitro+and+in+vivo+by+annexin+A5.">Promotion of corneal epithelial wound healing in vitro and in vivo by annexin A5.</a> Investigative Ophthalmology &amp; Visual Science. 47 (5), 1862-1868 (2006).</li><li>Murataeva, N., 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=Cannabinoid+CB2R+receptors+are+upregulated+with+corneal+injury+and+regulate+the+course+of+corneal+wound+healing.">Cannabinoid CB2R receptors are upregulated with corneal injury and regulate the course of corneal wound healing.</a> Experimental Eye Research. 182, 74-84 (2019).</li><li>Carter, K., 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=Characterizing+the+impact+of+2D+and+3D+culture+conditions+on+the+therapeutic+effects+of+human+mesenchymal+stem+cell+secretome+on+corneal+wound+healing+in+vitro+and+ex+vivo.">Characterizing the impact of 2D and 3D culture conditions on the therapeutic effects of human mesenchymal stem cell secretome on corneal wound healing in vitro and ex vivo.</a> Acta Biomaterialia. 99, 247-257 (2019).</li><li>Sanie-Jahromi, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Propagation+of+limbal+stem+cells+on+polycaprolactone+and+polycaprolactone/gelatin+fibrous+scaffolds+and+transplantation+in+animal+model.">Propagation of limbal stem cells on polycaprolactone and polycaprolactone/gelatin fibrous scaffolds and transplantation in animal model.</a> Bioimpacts. 10 (1), 45-54 (2020).</li><li>Sun, M. M., 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=Epithelial+membrane+protein+(EMP2)+antibody+blockade+reduces+corneal+neovascularization+in+an+In+vivo+model.">Epithelial membrane protein (EMP2) antibody blockade reduces corneal neovascularization in an In vivo model.</a> Investigative Ophthalmology &amp; Visual Science. 60 (1), 245-254 (2019).</li><li>Yang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cannabinoid+receptor+1+suppresses+transient+receptor+potential+vanilloid+1-induced+inflammatory+responses+to+corneal+injury.">Cannabinoid receptor 1 suppresses transient receptor potential vanilloid 1-induced inflammatory responses to corneal injury.</a> Cell Signal. 25 (2), 501-511 (2013).</li><li>Bai, J. Q., Qin, H. F., Zhao, S. 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Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-inflammatory+protein+TSG-6+reduces+inflammatory+damage+to+the+cornea+following+chemical+and+mechanical+injury.">Anti-inflammatory protein TSG-6 reduces inflammatory damage to the cornea following chemical and mechanical injury.</a> Proceedings of the National Academy of Sciences of the United States of America. 107 (39), 16875 (2010).</li><li>Wang, T., 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=Evaluation+of+the+effects+of+biohcly+in+an+in+vivo+model+of+mechanical+wounds+in+the+rabbit+cornea.">Evaluation of the effects of biohcly in an in vivo model of mechanical wounds in the rabbit cornea.</a> Journal of Ocular Pharmacology and Therapeutics. 35 (3), 189-199 (2019).</li><li>Gong, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+nintedanib+thermos-sensitive+hydrogel+on+neovascularization+in+alkali+burn+rat+model.">Effect of nintedanib thermos-sensitive hydrogel on neovascularization in alkali burn rat model.</a> International Journal of Ophthalmology. 13 (6), 879-885 (2020).</li><li>Yao, L., 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=Role+of+mesenchymal+stem+cells+on+cornea+wound+healing+induced+by+alkali+burn.">Role of mesenchymal stem cells on cornea wound healing induced by alkali burn.</a> PLoS One. 7 (2), 30842 (2012).</li></ol>

The authors have no competing financial interests.

Mouse and rabbit models of corneal injury provide a useful ex vivo and in vivo platform for monitoring wound healing, testing new therapeutics, and studying underlying mechanisms of wound healing and treatment pathways. Different animal models can be used for a short-term or long-term experiment, depending on the purpose of the research. For instance, after creating an epithelial defect on mouse cornea in vivo, a confined epithelial defect could be used to monitor liquid therapeutic agents in a...

The human cornea consists of five major layers and plays a pivotal role in ocular refraction to maintain visual acuity and structural integrity for protecting intraocular tissues1. The outermost part of the cornea is the corneal epithelium, composed of five to six layers of cells that sequentially differentiate from the basal cells and move upward to shed from the ocular surface1. Compared to the cornea in humans and New Zealand rabbits, mouse cornea has a similar corneal structure, but thinner periphery than the central part due to a reduced thickness in the epithelium and the stroma2. Because of its unique position in the ocular optic system, many external insults such as mechanical injury, bacterial inoculation, and chemical agents may easily endanger epithelial integrity and further lead to vision-threatening epithelium defect, infectious keratitis, corneal melting, and even corneal perforation.
Although various therapeutic agents, such as lubricants, antibiotics, anti-inflammatory agents, auto-serum products, and amniotic membrane have already been used to improve re-epithelialization and reduce scarring, other potential treatment modalities that can enable wound healing, reduce inflammation, and suppress scar formation are still being developed and tested on different platforms. Various animal models for corneal epithelial wound healing have been proposed, including corneal epithelium removal with a corneal rust ring remover in diabetic mouse3, linear scratches over mouse corneal epithelium by a sterile 25 G needle for bacterial inoculation4, trephine-assisted removal of the corneal epithelium by corneal rust ring remover5, epithelial cautery over half of the cornea and limbus6, trephine-facilitated rabbit corneal abrasion by a dulled scalpel blade7, and bovine cornea injury by flash freezing in liquid nitrogen8.
Other than mechanical injury to the corneal epithelium, chemical agents are also common insults to the ocular surface, especially acidic and alkali agents. Sodium hydroxide (NaOH, 0.1-1 N for 30-60 s) is one of the commonly used chemicals in murine and rabbit models of corneal chemical burn9,10,11,12,13. 100% ethanol had also been applied to the cornea in the rat chemical burn model, followed by additional mechanical scrapping using a surgical blade14. Since maintenance of a healthy ocular surface relies on functional units, including the eyelids, Meibomian glands, lacrimal system, the conjunctiva, and the cornea, in vivo animal models have some merits over ex vivo cultured cornea epithelial cells or corneal tissues. In this article, the mouse model of corneal abrasion wound, and the rabbit model of corneal alkali burn are demonstrated.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>6/0 Ethicon vicryl suture</td>
			<td>Ethicon</td>
			<td>6/0VICRYL</td>
			<td>tarsorrhaphy</td>
		</tr>
		<tr>
			<td>Barraquer lid speculum</td>
			<td>katena</td>
			<td>K1-5355</td>
			<td>15 mm</td>
		</tr>
		<tr>
			<td>Barraquer needle holder</td>
			<td>Katena</td>
			<td>K6-3310</td>
			<td>without lock</td>
		</tr>
		<tr>
			<td>Barron Vacuum Punch 8.0 mm</td>
			<td>katena</td>
			<td>K20-2108</td>
			<td>for cutting filter paper</td>
		</tr>
		<tr>
			<td>C57BL/6 mice</td>
			<td>National Laboratory Animal Center</td>
			<td>RMRC11005</td>
			<td>mouse strain</td>
		</tr>
		<tr>
			<td>Castroviejo forceps 0.12 mm</td>
			<td>katena</td>
			<td>K5-2500</td>
			<td></td>
		</tr>
		<tr>
			<td>Corneal rust ring remover with 0.5 mm burr</td>
			<td>Algerbrush IITM; Alger Equipment Co., Inc. Lago Vista, TX</td>
			<td>CHI-675</td>
			<td>for debridement of the corneal epithelium</td>
		</tr>
		<tr>
			<td>Filter paper</td>
			<td>Toyo Roshi Kaisha,Ltd.</td>
			<td>1.11</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescein sodum ophthalmic strips U.S.P</td>
			<td>OPTITECH</td>
			<td>OPTFL100</td>
			<td>staining for corneal epithelial defect</td>
		</tr>
		<tr>
			<td>Ketamine hydrochloride</td>
			<td>Sigma-Aldrich</td>
			<td>61763-23-3</td>
			<td>intraperitoneal or intramuscular anesthetics</td>
		</tr>
		<tr>
			<td>New Zealand White Rabbits</td>
			<td>Livestock Research Institute, Council of Agriculture,Executive Yuan</td>
			<td></td>
			<td>Rabbit models</td>
		</tr>
		<tr>
			<td>Normal saline</td>
			<td>TAIWAN BIOTECH CO., LTD.</td>
			<td>100-120-1101</td>
			<td></td>
		</tr>
		<tr>
			<td>Proparacaine</td>
			<td>Alcon</td>
			<td>ALC2UD09</td>
			<td>topical anesthetics</td>
		</tr>
		<tr>
			<td>Skin biopsy punch 2mm</td>
			<td>STIEFEL</td>
			<td>22650</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride (NaOH)</td>
			<td>Sigma-Aldrich</td>
			<td>1310-73-2</td>
			<td>a chemical agent for alkali burn</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Carl Zeiss Meditec, Dublin, CA</td>
			<td>SV11</td>
			<td>microscope for surgery</td>
		</tr>
		<tr>
			<td>Westcott Tenotomy Scissors Medium</td>
			<td>katena</td>
			<td>K4-3004</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylazine hydrochloride 23.32 mg/10 mL</td>
			<td>Elanco animal health Korea Co., LTD.</td>
			<td>047-956</td>
			<td>intraperitoneal or intramuscular anesthetics</td>
		</tr>
	</tbody>
</table>

ex vivo and in vivo animal models for mechanical and chemical injuries of corneal epithelium

Corneal injury to the ocular surface, including chemical burn and trauma, may cause severe scarring, symblepharon, corneal limbal stem cells deficiency, and result in a large, persistent corneal epithelial defect. Epithelial defect with the following corneal opacity and peripheral neovascularization result in irreversible visual impairment and hinder future management, especially keratoplasty. Since the animal model can be used as an effective drug development platform, models of corneal injury to the mouse and alkali burn to rabbit corneal epithelium are developed here. New Zealand white rabbit is used in the alkali burn model. Different concentrations of sodium hydroxide can be applied onto the central circular area of the cornea for 30 s under intramuscular and topical anesthesia. After copious isotonic normal saline irrigation, residual loose corneal epithelium was removed with corneal burr deep down to the Bowman's layer within this circular area. Wound healing was documented by fluorescein staining under Cobalt blue light. C57BL/6 mice were used in the traumatic model of murine corneal epithelium. The murine central cornea was marked using a skin punch, 2 mm in diameter, and then debrided by a corneal rust ring remover with a 0.5 mm burr under a stereomicroscope. These models can be prospectively used to validate the therapeutic effect of eye drops or mixed agents such as stem cells, which potentially facilitate corneal epithelial regeneration. By observing corneal opacity, peripheral neovascularization, and conjunctival congestion with stereomicroscope and imaging software, therapeutic effects in these animal models can be monitored.

Ex vivo wound healing model of the mouse corneal epithelium: 
After in vivo debridement of mouse corneal epithelium with hand-held corneal rust ring remover, a mildly depressed central corneal area with positive fluorescein stain can be found in the central 2 mm area (Figure 3A-B). After harvesting the mouse eyeball, it was easily fixed onto a wax-coated 48-well culture plate without significant rotati...

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Ex Vivo and In Vivo Animal Models for Mechanical and Chemical Injuries of Corneal Epithelium

Here, animal models based on mouse and rabbit are developed for mechanical and chemical injury of corneal epithelium to screen new therapeutics and the underlying mechanism.

Ex Vivo and In Vivo Animal Models for Mechanical and Chemical Injuries of Corneal Epithelium

Corneal injury to the ocular surface, including chemical burn and trauma, may cause severe scarring, symblepharon, corneal limbal stem cells deficiency, ...

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3.2K Views.  Chang-Gung Memorial Hospital. Here, animal models based on mouse and rabbit are developed for mechanical and chemical injury of corneal epithelium to screen new therapeutics and the underlying mechanism.

Video: Ex Vivo and In Vivo Animal Models for Mechanical and Chemical Injuries of Corneal Epithelium

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In vivo 19F MRI allows quantitative cell tracking without the use of ionizing radiation. It is a noninvasive technique that can be applied to humans. Here, we describe a general protocol for cell labeling, imaging, and image processing. The technique is applicable to various cell types and animal models, although here we focus on a typical mouse model for tracking murine immune cells. The most important issues for cell labeling are described, as these are relevant to all models. Similarly, key imaging parameters are listed, although the details will vary depending on the MRI system and the individual setup. Finally, we include an image processing protocol for quantification. Variations for this, and other parts of the protocol, are assessed in the Discussion section. Based on the detailed procedure described here, the user will need to adapt the protocol for each specific cell type, cell label, animal model, and imaging setup. Note that the protocol can also be adapted for human use, as long as clinical restrictions are met.

In vivo 19F MRI for Cell Tracking

We describe a general protocol for in vivo cell tracking using MRI in a mouse model with ex vivo labeled cells. A typical protocol for cell labeling, image acquisition processing and quantification is included.

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

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

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

In Vivo and Ex Vivo Approaches to Study Ovarian Cancer Metastatic Colonization of Milky Spot Structures in Peritoneal Adipose

High-grade serous ovarian cancer (HGSC), the cause of widespread peritoneal metastases, continues to have an extremely poor prognosis; fewer than 30% of women are alive 5 years after diagnosis. The omentum is a preferred site of HGSC metastasis formation. Despite the clinical importance of this microenvironment, the contribution of omental adipose tissue to ovarian cancer progression remains understudied. Omental adipose is unusual in that it contains structures known as milky spots, which are comprised of B, T, and NK cells, macrophages, and progenitor cells surrounding dense nests of vasculature. Milky spots play a key role in the physiologic functions of the omentum, which are required for peritoneal homeostasis. We have shown that milky spots also promote ovarian cancer metastatic colonization of peritoneal adipose, a key step in the development of peritoneal metastases. Here we describe the approaches we developed to evaluate and quantify milky spots in peritoneal adipose and study their functional contribution to ovarian cancer cell metastatic colonization of omental tissues both in vivo and ex vivo. These approaches are generalizable to additional mouse models and cell lines, thus enabling the study of ovarian cancer metastasis formation from initial localization of cells to milky spot structures to the development of widespread peritoneal metastases.

In Vivo and Ex Vivo Approaches to Study Ovarian Cancer Metastatic Colonization of Milky Spot Structures in Peritoneal Adipose

We outline a protocol that implements both in vivo and ex vivo approaches to study ovarian cancer colonization of peritoneal adipose tissues, particularly the omentum. Furthermore, we present a protocol to quantitate and analyze immune cell-structures in the omentum known as milky spots, which promote metastases of peritoneal adipose.

High-grade serous ovarian cancer (HGSC), the cause of widespread peritoneal metastases, continues to have an extremely poor prognosis; fewer than 30% of ...

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

The epithelial barrier is the first innate defense of the gastrointestinal tract and selectively regulates transport from the lumen to the underlying tissue compartments, restricting the transport of smaller molecules across the epithelium and almost completely prohibiting epithelial macromolecular transport. This selectivity is determined by the mucous gel layer, which limits the transport of lipophilic molecules and both the apical receptors and tight junctional protein complexes of the epithelium. In vitro cell culture models of the epithelium are convenient, but as a model, they lack the complexity of interactions between the microbiota, mucous-gel, epithelium and immune system. On the other hand, in vivo assessment of intestinal absorption or permeability may be performed, but these assays measure overall gastrointestinal absorption, with no indication of site specificity. Ex vivo permeability assays using &#34;intestinal sacs&#34; are a rapid and sensitive method of measuring either overall intestinal integrity or comparative transport of a specific molecule, with the added advantage of intestinal site specificity. Here we describe the preparation of intestinal sacs for permeability studies and the calculation of the apparent permeability (Papp) of a molecule across the intestinal barrier. This technique may be used as a method of assessing drug absorption, or to examine regional epithelial barrier dysfunction in animal models of gastrointestinal disease.

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

This protocol describes the use of excised intestinal tissue preparations or "intestinal sacs" as an ex vivo model of intestinal barrier function. This model may be used to assess integrity of both the epithelial barrier and the mucous gel layer at specific intestinal sites in animal models of digestive disease.

The epithelial barrier is the first innate defense of the gastrointestinal tract and selectively regulates transport from the lumen to the underlying ...

Generation of Microtumors Using 3D Human Biogel Culture System and Patient-derived Glioblastoma Cells for Kinomic Profiling and Drug Response Testing

The use of patient-derived xenografts for modeling cancers has provided important insight into cancer biology and drug responsiveness. However, they are time consuming, expensive, and labor intensive. To overcome these obstacles, many research groups have turned to spheroid cultures of cancer cells. While useful, tumor spheroids or aggregates do not replicate cell-matrix interactions as found in vivo. As such, three-dimensional (3D) culture approaches utilizing an extracellular matrix scaffold provide a more realistic model system for investigation. Starting from subcutaneous or intracranial xenografts, tumor tissue is dissociated into a single cell suspension akin to cancer stem cell neurospheres. These cells are then embedded into a human-derived extracellular matrix, 3D human biogel, to generate a large number of microtumors. Interestingly, microtumors can be cultured for about a month with high viability and can be used for drug response testing using standard cytotoxicity assays such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and live cell imaging using Calcein-AM. Moreover, they can be analyzed via immunohistochemistry or harvested for molecular profiling, such as array-based high-throughput kinomic profiling, which is detailed here as well. 3D microtumors, thus, represent a versatile high-throughput model system that can more closely replicate in vivo tumor biology than traditional approaches.

Patient-derived xenografts of glioblastoma multiforme can be miniaturized into living microtumors using 3D human biogel culture system. This in vivo-like 3D tumor assay is suitable for drug response testing and molecular profiling, including kinomic analysis.

The use of patient-derived xenografts for modeling cancers has provided important insight into cancer biology and drug responsiveness. However, they are ...

Depletion of Mouse Cells from Human Tumor Xenografts Significantly Improves Downstream Analysis of Target Cells

The use of in vitro cell line models for cancer research has been a useful tool. However, it has been shown that these models fail to reliably mimic patient tumors in different assays1. Human tumor xenografts represent the gold standard with respect to tumor biology, drug discovery, and metastasis research 2-4. Tumor xenografts can be derived from different types of material like tumor cell lines, tumor tissue from primary patient tumors4 or serially transplanted tumors. When propagated in vivo, xenografted tissue is infiltrated and vascularized by cells of mouse origin. Multiple factors such as the tumor entity, the origin of xenografted material, growth rate and region of transplantation influence the composition and the amount of mouse cells present in tumor xenografts. However, even when these factors are kept constant, the degree of mouse cell contamination is highly variable.
Contaminating mouse cells significantly impair downstream analyses of human tumor xenografts. As mouse fibroblasts show high plating efficacies and proliferation rates, they tend to overgrow cultures of human tumor cells, especially slowly proliferating subpopulations. Mouse cell derived DNA, mRNA, and protein components can bias downstream gene expression analysis, next-generation sequencing, as well as proteome analysis 5. To overcome these limitations, we have developed a fast and easy method to isolate untouched human tumor cells from xenografted tumor tissue. This procedure is based on the comprehensive depletion of cells of mouse origin by combining automated tissue dissociation with the benchtop tissue dissociator and magnetic cell sorting. Here, we demonstrate that human target cells can be can be obtained with purities higher than 96% within less than 20 min independent of the tumor type.

Human tumor xenografts are vascularized and infiltrated by cells of mouse origin during the growth phase in vivo. To circumvent the bias caused by these contaminating cells during downstream analysis, we developed a method allowing for comprehensive depletion of all mouse cells by magnetic cell sorting.

The use of in vitro cell line models for cancer research has been a useful tool. However, it has been shown that these models fail to reliably mimic ...

In Vivo Evaluation of the Mechanical and Viscoelastic Properties of the Rat Tongue

The tongue is a highly innervated and vascularized muscle hydrostat on the floor of the mouth of most vertebrates. Its primary functions include supporting mastication and deglutition, as well as taste-sensing and phonetics. Accordingly, the strength and volume of the tongue can impact the ability of vertebrates to accomplish basic activities such as feeding, communicating, and breathing. Human patients with sleep apnea have enlarged tongues, characterized by reduced muscle tone and increased intramuscular fat that can be visualized and quantified by magnetic resonance imaging (MRI). The abilities to measure force generation and viscoelastic properties of the tongue constitute important tools for obtaining functional information to correlate with imaging data. Here, we present techniques for measuring tongue force production in anesthetized Zucker rats via electrical stimulation of the hypoglossal nerves and for determining the viscoelastic properties of the tongue by applying passive Lissajous force/deformation curves.

In Vivo Evaluation of the Mechanical and Viscoelastic Properties of the Rat Tongue

We describe a surgical procedure in an anesthetized rat model for determining the muscle tone and viscoelastic properties of the tongue. The procedure involves specific stimulation of the hypoglossal nerves and application of passive Lissajous force/deformation curves to the muscle.

The tongue is a highly innervated and vascularized muscle hydrostat on the floor of the mouth of most vertebrates. Its primary functions include ...

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, normothermic ex vivo liver perfusion (NEVLP) has been introduced as a method to evaluate and modify organ function. NEVLP has many advantages in comparison to hypothermic and subnormothermic perfusion including reduced preservation injury, restoration of normal organ function under physiologic conditions, assessment of organ performance, and as a platform for organ repair, remodeling, and modification. Both murine and porcine NEVLP models have been described. We demonstrate a rat model of NEVLP and use this model to show one of its important applications &#8212; the use of a therapeutic molecule added to liver perfusate. Catalase is an endogenous reactive oxygen species (ROS) scavenger and has been demonstrated to decrease ischemia-reperfusion in the eye, brain, and lung. Pegylation has been shown to target catalase to the endothelium. Here, we added pegylated-catalase (PEG-CAT) to the base perfusate and demonstrated its ability to mitigate liver preservation injury. An advantage of our rodent NEVLP model is that it is inexpensive in comparison to larger animal models. A limitation of this study is that it does not currently include post-perfusion liver transplantation. Therefore, prediction of the function of the organ post-transplantation cannot be made with certainty. However, the rat liver transplant model is well established and certainly could be used in conjunction with this model. In conclusion, we have demonstrated an inexpensive, simple, easily replicable NEVLP model using rats. Applications of this model can include testing novel perfusates and perfusate additives, testing software designed for organ evaluation, and experiments designed to repair organs.

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant liver donor shortage, and criteria for liver donors have been expanded. Normothermic ex vivo liver perfusion (NEVLP) has been developed to evaluate and modify organ function. This study demonstrates a rat model of NEVLP and tests the ability of pegylated-catalase, to mitigate liver preservation injury.

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, ...

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.

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 ...

An Ex Vivo Tissue Culture Model for Fibrovascular Complications in Proliferative Diabetic Retinopathy

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and one of the leading causes of blindness in working-age adults. No current animal models of diabetes and oxygen-induced retinopathy develop the full-range progressive changes manifested in human proliferative diabetic retinopathy (PDR). Therefore, understanding of the disease pathogenesis and pathophysiology has relied largely on the use of histological sections and vitreous samples in approaches that only provide steady-state information on the involved pathogenic factors. Increasing evidence indicates that dynamic cell-cell and cell-extracellular matrix (ECM) interactions in the context of three-dimensional (3D) microenvironments are essential for the mechanistic and functional studies towards the development of new treatment strategies. Therefore, we hypothesized that the pathological fibrovascular tissue surgically excised from eyes with PDR could be utilized to reliably unravel the cellular and molecular mechanisms of this devastating disease and to test the potential for novel clinical interventions. Towards this end, we developed a novel method for 3D ex vivo culture of surgically-excised patient-derived fibrovascular tissue (FT), which will serve as a relevant model of human PDR pathophysiology. The FTs are dissected into explants and embedded in fibrin matrix for ex vivo culture and 3D characterization. Whole-mount immunofluorescence of the native FTs and end-point cultures allows thorough investigation of tissue composition and multicellular processes, highlighting the importance of 3D tissue-level characterization for uncovering relevant features of PDR pathophysiology. This model will allow the simultaneous assessment of molecular mechanisms, cellular/tissue processes and treatment responses in the complex context of dynamic biochemical and physical interactions within the PDR tissue architecture and microenvironment. Since this model recapitulates PDR pathophysiology, it will also be amenable for testing or developing new treatments.

Here, we present a protocol to study the pathophysiology of proliferative diabetic retinopathy by using patient-derived, surgically-excised, fibrovascular tissues for three-dimensional native tissue characterization and ex vivo culture. This ex vivo culture model is also amenable for testing or developing new treatments.

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and one of the leading causes of blindness in working-age adults. No ...

Methods Article

Ex Vivo and In Vivo Animal Models for Mechanical and Chemical Injuries of Corneal Epithelium