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

Summary

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.

Abstract

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.

Introduction

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....

Protocol

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

1. Preparation of the mice
   1. Administer general anesthesia to C57BL/6 mice by intraperitoneal delivery of ketamine hydrochloride (80-100 mg/kg of body weight) an.......

Discussion

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.......

Materials

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