Name: establishing a porcine ex vivo cornea model for studying drug treatments against bacterial keratitis
Uploaded: 2020-05-12T13:30:00
Description: Watch this Scientific Journal Video about Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis at JoVE.com

The authors would like to thank Elliot Abattoir in Chesterfield for providing porcine eyes. The glass rings were made based on our design by the glass blower Dan Jackson from the Department of Chemistry at the University of Sheffield. The authors would like to thank the Medical Research Council (MR/S004688/1) for funding. The authors would like to also thank Mrs Shanali Dikwella for technical help with cornea preparation. The authors would like to thank Mr Jonathan Emery for help with formatting pictures.

Albino laboratory rabbits were sacrificed in the laboratory for other planned experimental work under home office approved protocols. The eyes were not required for experimental use in those studies so they were used for this protocol.
1. Sterilization
<ol>
	<li>CRITICAL STEP: Disinfect all forceps and scissors by soaking for 1 h in 5% (v/v) solution of Distel in distilled water, clean with a brush, rinse with tap water and sterilize in an oven at 185 &#176;C for a minimum of 2 h.</li>
	<li>...

<ol>
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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+and+Characterization+of+an+Air-Liquid+Canine+Corneal+Organ+Culture+Model+To+Study+Acute+Herpes+Keratitis.">Establishment and Characterization of an Air-Liquid Canine Corneal Organ Culture Model To Study Acute Herpes Keratitis.</a> Journal of Virology. 88 (23), 13669-13677 (2014).</li><li>Madhu, S. N., Jha, K. K., Karthyayani, A. P., Gajjar, D. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+Caprine+Model+to+Study+Virulence+Factors+in+Keratitis.">Ex vivo Caprine Model to Study Virulence Factors in Keratitis.</a> Journal of Ophthalmic &amp; Vision Research. 13 (4), 383-391 (2018).</li><li>Vermeltfoort, P. B. J., van Kooten, T. G., Bruinsma, G. M., Hooymans, A. M. M., vander Mei, H. C., Busscher, H. 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The main driver behind the development of this keratitis model using ex vivo porcine cornea is to provide researchers developing novel antimicrobials with a representative in vitro model to more accurately determine antimicrobial efficacy at the preclinical stages. This will provide researchers involved in developing new antimicrobials greater control over drug design and formulation at the pre-clinical stages, increase success at clinical trials, reduce use of animals by enabling targeted studies and result in faster tr...

Corneal infections are important causes of blindness and occur in epidemic proportions in low- and mid-income countries. The etiology of the disease varies from region to region but bacteria account for a large majority of these cases. Pseudomonas aeruginosa is an important pathogen that causes a rapidly progressive disease. In many cases, patients are left with stromal scarring, irregular astigmatism, require transplant or in the worst case scenario, lose an eye1,2.
Bacterial keratitis caused by P. aeruginosa is a difficult eye infection to treat particularly due to the increasing emergence of antimicrobial resistant strains of P. aeruginosa. Within the last decade, it has become apparent that testing and developing new treatments for corneal infections, in general, and those caused by Pseudomonas sp., in particular, are essential to combat the current trend in antibiotic resistance3.
For testing the efficacy of new treatments for corneal infections, conventional in vitro microbiological methods are a poor surrogate due to the difference in bacterial physiology during laboratory culture and during infections in vivo as well as due to the lack of the host interface4,5. In vivo animal models, however, are expensive, time-consuming, can only deliver a small number of replicates and raise concerns about animal welfare.
In this article, we demonstrate a simple and reproducible organotypic ex vivo porcine model of keratitis that can be used to test various treatments for acute and chronic infections. We have used P. aeruginosa for this experiment but the model also works well with other bacteria, and organisms such as fungi and yeast which cause keratitis.

<table>
	<tbody>
		<tr>
			<td>50 mL Falcon tube</td>
			<td>SLS</td>
			<td>352070</td>
			<td></td>
		</tr>
		<tr>
			<td>Amphotericin B</td>
			<td>Sigma</td>
			<td>A2942</td>
			<td></td>
		</tr>
		<tr>
			<td>Cellstar 12 well plate</td>
			<td>Greiner Bio-One</td>
			<td>665180</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran</td>
			<td>Sigma</td>
			<td>31425-100mg-F</td>
			<td></td>
		</tr>
		<tr>
			<td>Distel</td>
			<td>Fisher Scientific</td>
			<td>12899357</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM + glutamax</td>
			<td>SLS</td>
			<td>D0819</td>
			<td></td>
		</tr>
		<tr>
			<td>Dual Oven Incubator</td>
			<td>SLS</td>
			<td>OVe1020</td>
			<td>Sterilising oven</td>
		</tr>
		<tr>
			<td>Epidermal growth factor</td>
			<td>SLS</td>
			<td>E5036-200UG</td>
			<td></td>
		</tr>
		<tr>
			<td>F12 HAM</td>
			<td>Sigma</td>
			<td>N4888</td>
			<td></td>
		</tr>
		<tr>
			<td>Foetal calf serum</td>
			<td>Labtech International</td>
			<td>CA-115/500</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Fisher Scientific</td>
			<td>15307805</td>
			<td></td>
		</tr>
		<tr>
			<td>Handheld homogeniser 220</td>
			<td>Fisher Scientific</td>
			<td>15575809</td>
			<td>Homogeniser</td>
		</tr>
		<tr>
			<td>Heracell VIOS 160i</td>
			<td>Thermo Scientific</td>
			<td>15373212</td>
			<td>Tissue culture incubator</td>
		</tr>
		<tr>
			<td>Heraeus Megafuge 16R</td>
			<td>VWR</td>
			<td>521-2242</td>
			<td>Centrifuge</td>
		</tr>
		<tr>
			<td>Insulin, recombinant Human</td>
			<td>SLS</td>
			<td>91077C-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>LB agar</td>
			<td>Sigma</td>
			<td>L2897</td>
			<td></td>
		</tr>
		<tr>
			<td>Multitron</td>
			<td>Infors</td>
			<td>Not appplicable</td>
			<td>Bacterial incubator</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>SLS</td>
			<td>P4417</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>SLS</td>
			<td>P0781</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>Fisher Scientific</td>
			<td>12664785</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish 35x10mm CytoOne</td>
			<td>Starlab</td>
			<td>CC7672-3340</td>
			<td></td>
		</tr>
		<tr>
			<td>Povidone iodine</td>
			<td>Weldricks pharmacy</td>
			<td>2122828</td>
			<td></td>
		</tr>
		<tr>
			<td>Safe 2020</td>
			<td>Fisher Scientific</td>
			<td>1284804</td>
			<td>Class II microbiology safety cabinet</td>
		</tr>
		<tr>
			<td>Scalpel blade number 15</td>
			<td>Fisher Scientific</td>
			<td>O305</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel Swann Morton</td>
			<td>Fisher Scientific</td>
			<td>11849002</td>
			<td></td>
		</tr>
	</tbody>
</table>

establishing a porcine ex vivo cornea model for studying drug treatments against bacterial keratitis

When developing novel antimicrobials, the success of animal trials is dependent on accurate extrapolation of antimicrobial efficacy from in vitro tests to animal infections in vivo. The existing in vitro tests typically overestimate antimicrobial efficacy as the presence of host tissue as a diffusion barrier is not accounted for. To overcome this bottleneck, we have developed an ex vivo porcine corneal model of bacterial keratitis using Pseudomonas aeruginosa as a prototypic organism. This article describes the preparation of the porcine cornea and protocol for establishment of the infection. Bespoke glass molds enable straightforward setup of the cornea for infection studies. The model mimics in vivo infection as bacterial proliferation is dependent on the ability of the bacterium to damage corneal tissue. Establishment of infection is verified as an increase in the number of colony forming units assessed via viable plate counts. The results demonstrate that infection can be established in a highly reproducible fashion in the ex vivo corneas using the method described here. The model can be extended in the future to mimic keratitis caused by microorganisms other than P. aeruginosa. The ultimate aim of the model is to investigate the effect of antimicrobial chemotherapy on the progress of bacterial infection in a scenario more representative of in vivo infections. In so doing, the model described here will reduce the use of animals for testing, improve success rates in clinical trials and ultimately enable rapid translation of novel antimicrobials to the clinic.

The design of the glass molds are an innovative and original idea, the use of which allowed us to set up the model in a consistent fashion with minimal/no issues with contamination. The molds were prepared by a glass blower at the University of Sheffield based on a design (Figure 1A). The experimental setup maintains the convex shape of the cornea and holds bacteria on the top of the epithelium where infection takes place (Figure 1B).
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Watch this Scientific Journal Video about Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis at JoVE.com

Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis

This article describes a step-by-step protocol to set up an ex vivo porcine model of bacterial keratitis. Pseudomonas aeruginosa is used as a prototypic organism. This innovative model mimics in vivo infection as bacterial proliferation is dependent on the ability of the bacterium to damage corneal tissue.

When developing novel antimicrobials, the success of animal trials is dependent on accurate extrapolation of antimicrobial efficacy from in vitro tests to ...

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