The authors would like to thank Dr. John Harbell for his scientific support and time dedicated to the EIT project. The authors also would like to thank Beiersdorf AG (Germany), IIVS (USA), Mary Kay Inc. (USA), Avon Products Inc. (USA), Procter &#38; Gamble/Cosmital (Switzerland), Laboratoire Pierre Fabre (France), Harlan Laboratories (United Kingdom), and LVMH Parfume (France) for participation in Multi-center International Pre-Validation and Validation Studies of the Eye Irritation Test15.

<ol>
	<li>National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM). <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Request+for+Ocular+Irritancy+Test+Data+From+Human,+Rabbit,+and+In+Vitro+Studies+Using+Standardized+Testing+Methods.">Request for Ocular Irritancy Test Data From Human, Rabbit, and In Vitro Studies Using Standardized Testing Methods.</a> Federal Register. 72 (109), 31582-31583 (2007).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+(EC)+No+1907/2006+of+the+European+Parliament+and+of+the+Council+of+18+December+2006+concerning+the+Registration,+Evaluation,+Authorisation+and+Restriction+of+Chemicals+(REACH),+establishing+a+European+Chemicals+Agency,+amending+Directive+1999/45/EC+and+repealing+Council+Regulation+(EEC)+No+793/93+and+Commission+Regulation+(EC)+No+1488/94+as+well+as+Council+Directive+76/769/EEC+and+Commission+Directives+91/155/EEC,+93/67/EEC,+93/105/EC+and+2000/21/EC.">Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), establishing a European Chemicals Agency, amending Directive 1999/45/EC and repealing Council Regulation (EEC) No 793/93 and Commission Regulation (EC) No 1488/94 as well as Council Directive 76/769/EEC and Commission Directives 91/155/EEC, 93/67/EEC, 93/105/EC and 2000/21/EC.</a> OJ. L396 (49), 1-849 (2006).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Globally Harmonized System of Classification and Labelling of Chemicals (GHS). , (2013).</li><li>Draize, J. H., Woodard, G., Calvery, H. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+the+Study+of+Irritation+and+Toxicity+of+Substances+Applied+Topically+to+the+Skin+and+Mucous+Membranes.">Methods for the Study of Irritation and Toxicity of Substances Applied Topically to the Skin and Mucous Membranes.</a> J Pharmacol Exp Ther November. 82, 377-390 (1944).</li><li>Adriaens, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retrospective+analysis+of+the+Draize+test+for+serious+eye+damage/eye+irritation:+importance+of+understanding+the+in+vivo+endpoints+under+UN+GHS/EU+CLP+for+the+development+and+evaluation+of+in+vitro+test+methods.">Retrospective analysis of the Draize test for serious eye damage/eye irritation: importance of understanding the in vivo endpoints under UN GHS/EU CLP for the development and evaluation of in vitro test methods.</a> Arch tox. 88, 701-723 (2014).</li><li>Balls, M., Botham, P. A., Bruner, L. H., Spielmann, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+EC/HO+international+validation+study+on+alternatives+to+the+Draize+eye+irritation+test.">The EC/HO international validation study on alternatives to the Draize eye irritation test.</a> Toxicol in Vitro. 9, 871-929 (1995).</li><li>Curren, R. D., Harbell, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ocular+safety:+a+silent+(in+vitro)+success+story.">Ocular safety: a silent (in vitro) success story.</a> Altern Lab Anim. 30, 69-74 (2002).</li><li>Wilhelmus, K. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Draize+Eye+Test.">The Draize Eye Test.</a> Survey of Ophthalmology. 45, 493-515 (2001).</li><li>Curren, R. D., Harbell, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+alternatives+for+ocular+irritation.">In vitro alternatives for ocular irritation.</a> Environ health persp. 106, 485-492 (1998).</li><li>McCain, N. E., Binetti, R. R., Gettings, S. D., Jones, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+ocular+irritation+ranges+of+market-leading+cosmetic+and+personal-care+products+using+an+in+vitro+tissue+equivalent.">Assessment of ocular irritation ranges of market-leading cosmetic and personal-care products using an in vitro tissue equivalent.</a> Toxicologist. 66, 243 (2002).</li><li>Niranjan, P., Dang, A. H., January, B. G., Gomez, C., Harbell, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+the+EpiOcular+assay+for+preclinical+qualification+of+formulas+for+human+clinical+studies.">Use of the EpiOcular assay for preclinical qualification of formulas for human clinical studies.</a> Toxicologist. 96, 249 (2007).</li><li>Yin, X. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prediction+of+ocular+irritation+potential+of+surfactants-based+formulations+at+different+concentrations+using+the+EpiOcular+model.">Prediction of ocular irritation potential of surfactants-based formulations at different concentrations using the EpiOcular model.</a> Toxicologist. 108, 378 (2009).</li><li>Harbell, J., Curren, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+methods+for+the+prediction+of+ocular+and+dermal+toxicity.">In vitro methods for the prediction of ocular and dermal toxicity.</a> Handbook of Toxicology. , (2001).</li><li>Kaluzhny, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+EpiOcular(TM)+eye+irritation+test+for+hazard+identification+and+labelling+of+eye+irritating+chemicals+in+response+to+the+requirements+of+the+EU+cosmetics+directive+and+REACH+legislation.">Development of the EpiOcular(TM) eye irritation test for hazard identification and labelling of eye irritating chemicals in response to the requirements of the EU cosmetics directive and REACH legislation.</a> Altern Lab Anim. 39, 339-364 (2011).</li><li>Pfannenbecker, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cosmetics+Europe+Multi-Laboratory+Pre-Validation+of+the+EpiOcular+Reconstituted+Human+Tissue+Test+Method+for+the+Prediction+of+Eye+Irritation.">Cosmetics Europe Multi-Laboratory Pre-Validation of the EpiOcular Reconstituted Human Tissue Test Method for the Prediction of Eye Irritation.</a> Toxicol in vitro. , (2013).</li><li>MatTek Corporation. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> EpiOcular™ Eye Irritation Test (OCL-200-EIT) for the prediction of acute ocular irritation of chemicals for use with Reconstructed Human EpiOcular Model (OCL-200-EIT). Protocol#MK-24-007-0055. , (2014).</li><li>Kaluzhny, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EpiOcular+Eye+Irritation+Test+(EIT)+for+Hazard+Identification+and+Labeling+of+Eye+Irritating+Chemicals:+Protocol+Optimization+for+Solid+Materials+and+Extended+Shipment+Times.">EpiOcular Eye Irritation Test (EIT) for Hazard Identification and Labeling of Eye Irritating Chemicals: Protocol Optimization for Solid Materials and Extended Shipment Times.</a> Altern Lab Anim. 43 (2), 101-127 (2015).</li><li>Kolle, S. N., Kandarova, H., Wareing, B., van Ravenzwaay, B., Landsiedel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-house+validation+of+the+EpiOcular(TM)+eye+irritation+test+and+its+combination+with+the+bovine+corneal+opacity+and+permeability+test+for+the+assessment+of+ocular+irritation.">In-house validation of the EpiOcular(TM) eye irritation test and its combination with the bovine corneal opacity and permeability test for the assessment of ocular irritation.</a> Altern Lab Anim. 39, 365-387 (2011).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconstructed+Human+Cornea-like+Epithelium+(RhCE)+Test+Method+for+Identifying+Chemicals+Not+Requiring+Classification+and+Labelling+for+Eye+Irritation+or+Serious+Eye+Damage.+Draft+proposal+for+a+new+test+guideline..">Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage. Draft proposal for a new test guideline..</a> OECD Guideline for the Testing of Chemicals. , (2014).</li><li>Blazka, M. E., Harbell, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+the+ocular+irritation+potential+of+54+test+articles+using+the+EpiOcular+Human+tissue+Construct+Model.">Evaluating the ocular irritation potential of 54 test articles using the EpiOcular Human tissue Construct Model.</a> Toxicol. In Vitro. , (2003).</li><li>Kandarova, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+EpiDerm+Test+Protocol+for+the+Upcoming+ECVAM+Validation+Study+on+In+Vitro+Skin+Irritation+Tests+&#8212;+An+Assessment+of+the+Performance+of+the+Optimised+Test.">The EpiDerm Test Protocol for the Upcoming ECVAM Validation Study on In Vitro Skin Irritation Tests &#8212; An Assessment of the Performance of the Optimised Test.</a> Altern Lab Anim. 33, 351-367 (2005).</li></ol>

Publication fees for this article were paid by MatTek Corporation. The authors are employees of MatTek Corporation.

We have presented the Eye Irritation Test (Figure 1) that was developed for the EpiOcular tissue model. The EIT is able to separate ocular irritants and corrosives (GHS Categories 1 and 2 combined) from materials that do not require labeling (GHS No Category) with high degree of sensitivity and specificity17. The EIT as presented herein does not discriminate between GHS Category 1 from Category 2 chemicals. The EIT was validated for classification and labeling of ocular irritation potential of a wide range of chemicals, including cosmetic and pharmaceutical ingredients. In conjunction with other in vitro tests, the EIT will serve as a replacement for the in vivo rabbit eye irritation test.
The EIT uses two similar but distinct protocols for liquid and solid materials, which vary in the length of exposure and post-exposure incubation periods (Figure 1). The endpoint used in the EIT is tissue viability, determined by the MTT assay, which has been previously used in validated human epithelial tissue models20,21. To perform this assay, no special equipment besides standard cell culture equipment is needed. Due to the high level of tissue-to-tissue reproducibility, n = 2 tissues instead of the usually recommended n = 3 are used. The ability to use n= 2 tissues is a critical aspect of the protocol, since it allows an experienced operator to process two tissues simultaneously, thereby minimizing the variability of the assay that can arise due to the different handling of individual tissues14. Also, by using n = 2 tissues per test article, the irritancy of 10 test substances of the same physical state (liquid or solid), along with the positive and negative controls, can be evaluated using one kit (24 tissues).
Other key points that ensure reliable classification of materials are specifications for the positive control substance (tissue viability &#8804;50.0%), reproducibility between duplicate tissues (difference &#60;20.0%), and negative control OD readings (&#62;0.8 and &#60;2.5).
When performing the EIT test, it is important to adhere to the validated protocol and to the suggested dosing and rinsing schedules (Tables 3 and 4), since deviation from the protocol or changes in the incubation periods may result in altered outcome. Likewise, deviations from the 3 hr time for MTT incubation will result in different MTT readings and may affect assay result.
Occasionally, a test chemical may have optical or other properties which may interfere with MTT tissue viability assay or cause reduction of MTT. For instance, a test chemical may directly reduce MTT into blue-purple reaction product, or may be a colored substance that absorbs light in the same range as MTT formazan (~570 nm). However, these test chemicals will present a problem only, if at the time of the MTT assay, a sufficient amount of the material is still present on (or absorbed by) the tissue. To avoid this interference, extensive rinsing procedures are incorporated into the EIT protocol. If rinsing does not remove the TA and the TA interferes with MTT reduction, additional controls must be used to detect and correct for it. Briefly, if direct MTT reduction of the test chemical is suspected, 50 &#181;l (or 50 mg for solids) of the chemical in question is incubated for 3 hr with working MTT solution at SCC (NC, 50 &#181;l of sterile deionized water, should be run concurrently). If the MTT solution turns blue-purple, the test article is presumed to have reduced the MTT. In this case a functional check using freeze-killed tissue controls should be performed to evaluate whether the test material is binding to the tissue and leading to a false MTT reduction signal. If there is appreciable MTT reduction in the TA-exposed, killed tissue control (relative to the amount in the untreated viable tissue), the mean tissue viability of the test article must be corrected by subtracting the mean viability of the killed control.
The EIT errs on the side of safety, as demonstrated by the low incidence of false negative classifications14,15,18. Importantly, none of the GHS Category 1 chemicals, which are corrosive to the eye and which represent the most serious ocular hazard, were classified as non-irritating in this assay14,15,18,19. Finally, one of the major advantages of the RhCE in vitro test method is the possibility of testing neat liquid and solid materials (which is not possible with two-dimensional, submerged cell cultures).
The EIT will &#160;contribute significantly in determining the ocular irritation potential of a wide range of materials according to the UN GHS classification and labeling system. The replacement of animals to determine ocular toxicity has been a goal of toxicological research for many years. The EIT test method has completed a formal validation study supported by EURL ECVAM in 2014 and the EpiOcular EIT was implemented into the OECD test Guidelines as OECD TG 492&#160;in 2015.

Consumer products such as cosmetics, detergents, and household cleaners include a variety of chemicals that may induce serious damage if they contact the eyes. Therefore, testing of these agents for eye irritation is required by the US and EU regulatory agencies to ensure consumer safety1. An assessment of the eye irritation potential of mixtures and formulations is also a requirement for complying with REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) legislation for the labeling of cosmetic ingredients under the EU Cosmetics Directive for transport of chemicals, and for the labeling of pesticides and household products2. Currently, regulatory agencies require ocular hazard assessment using the Globally Harmonized System of Classification and Labeling of Chemicals (GHS)3. GHS is mainly based on the Draize eye irritation test, the most widely used eye irritation assay in which foreign substances and mixtures are introduced directly into the conjunctival sac of the rabbit eye4. According to GHS classification, GHS Category 1 (ocular corrosives) refers to test chemicals that cause severe initial injury to the eye tissues or serious damage to the eye and vision which is not fully reversible within 21 days following exposure3,5. GHS Category 2 refers to test chemicals that produce significant changes in the eye that are fully reversible within 21 days of exposure. Test chemicals that are not corrosives or irritants are referred to as GHS No Category.
For more than 40 years, the Draize rabbit eye test has been criticized for its lack of reproducibility, overestimation of human responses, and the use of live animals5-8. These concerns have encouraged many proposals for refinement, reduction, and replacement of the in&#160;vivo&#160;test9. The need for validated non-animal alternatives was further strengthened by the adoption of the Seventh Amendment to the Cosmetics Directive, which banned the use of animals in the safety evaluation of cosmetic products (in 2005) and ingredients (in 2009)2.
Since 1996, the reconstructed cornea-like tissue model has been widely used by the cosmetic industry to evaluate the irritation potential of raw materials, surfactant-based formulations, and compounded mixtures that are designed for use in, or in the vicinity of, the eye10-13. Use of the RhCE tissue model allows direct topical application of the test material onto the tissue surface in its native, undiluted form. In this way, non-water soluble formulations can be tested without diluting them with solvents. In response to EURL ECVAM&#8217;s (European Union Reference Laboratory European Centre for the Validation of Alternative Methods) request for a widely applicable, straightforward, and economic method the Eye Irritation Test (EIT) which utilizes a single exposure time and is able to separate ocular irritants and corrosives from materials that do not require labeling was developed (Figure 1)14. Based on the results for 83 chemicals (44 liquids and 39 solids), the EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A.
In 2007, a multi-laboratory pre-validation study sponsored by Cosmetics Europe (formerly Colipa) under the auspices of the EURL ECVAM assessed the relevance and reliability of the EIT with the goal of bringing it to formal validation15. In this study, 298 independent trials were performed in seven independent laboratories. Study results demonstrated 99.7% agreement in prediction with low coefficients of variation across all participating laboratories15. As a result, in 2010 the EIT protocol entered a formal EURL ECVAM validation program. The validation study utilized 104 coded test chemicals, including individual substances and chemical mixtures, for which in vivo reference data (Draize eye irritation data) were available. Based on the success of this work, an OECD draft test guideline was submitted in 2014. It is anticipated that the EIT will contribute significantly to classification of ocular irritation potential of a wide range of materials according to the UN GHS classification and labeling system.

eye irritation test (eit) for hazard identification of eye irritating chemicals using reconstructed human cornea-like epithelial (rhce) tissue model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and accurate assessment of ocular toxicity in man are needed. To address this need, we have developed an eye irritation test (EIT) which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model that is based on normal human cells. The EIT is able to separate ocular&#160;irritants and corrosives (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category). The test utilizes two separate protocols, one designed for liquid chemicals and a second, similar protocol for solid test articles. The EIT prediction model uses a single exposure period (30 min for liquids, 6 hr for solids) and a single tissue viability cut-off (60.0% as determined by the MTT assay). Based on the results for 83 chemicals (44 liquids and 39 solids) EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A. The EIT will contribute significantly to classifying the ocular irritation potential of a wide range of liquid and solid chemicals without the use of animals to meet regulatory testing requirements. The EpiOcular EIT method was implemented in 2015 into the OECD Test Guidelines as TG 492.

Watch this Scientific Journal Video about Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model at JoVE.com

Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

Eye Irritation Test (EIT) for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial (RhCE) Tissue Model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and ...

eye-irritation-test-eit-for-hazard-identification-eye-irritating

Universidad de Cartagena UDEC

Research

JoVE Journal

Bioengineering

37.5K Views.  MatTek Corporation. We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

Video: Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

Experimental Models for Study of Retinal Pigment Epithelial Physiology and Pathophysiology

We have developed a cell culture procedure that can produce large quantities of confluent monolayers of primary human fetal retinal pigment epithelium (hfRPE) cultures with morphological, physiological and genetic characteristics of native human RPE. These hfRPE cell cultures exhibit heavy pigmentation, and electron microscopy show extensive apical membrane microvilli. The junctional complexes were identified with immunofluorescence labeling of various tight junction proteins. Epithelial polarity and function of these easily reproducible primary cultures closely resemble previously studied mammalian models of native RPE, including human. These results were extended by the development of therapeutic interventions in several animal models of human eye disease. We have focused on strategies for the removal of abnormal fluid accumulation in the retina or subretinal space. The extracellular subretinal space separates the photoreceptor outer segments and the apical membrane of the RPE and is critical for maintenance of retinal attachments and a whole host of RPE/retina interactions.

We provide a reproducible method for culturing confluent monolayers of human fetal retinal pigment epithelial cells (hfRPE) cells that exhibit morphology, physiology, polarity, and protein and gene expression patterns of adult native tissue. This work has been extended to an animal model of several eye diseases.

We have developed a cell culture procedure that can produce large quantities of confluent monolayers of primary human fetal retinal pigment epithelium ...

Neuroscience

An In Vitro Skin Irritation Test (SIT) using the EpiDerm Reconstructed Human Epidermal (RHE) Model

The EpiDerm Skin Irritation test (EpiDerm SIT) was developed (1,2,3) and validated (4,5) for in vitro skin irritation testing of chemicals, including cosmetic and pharmaceutical ingredients. The EpiDerm SIT utilizes the 3D in vitro reconstructed human epidermal (RHE) model EpiDerm. The procedure described in this protocol allows for discrimination between irritants of GHS category 2 and non-irritants (6). The test is performed over the course of a 4 day time period, consisting of pre-incubation, 60 minute exposure, 42 hour post-incubation and MTT viability assay. After tissue receipt and overnight pre-incubation (Day 0), tissues are topically exposed to the test chemicals (Day 1), which can be liquid, semi-solids, solid or wax. Three tissues are used for each test chemical, as well as for the positive control (5% aq. SDS solution), and a negative control (DPBS). Chemical exposure lasts for 60 minutes, 35 min of which the tissues are kept in an incubator at 37&deg;C. The test substances are then removed from the tissue surface by an extensive washing procedure. The tissue inserts are blotted and transferred to fresh medium. After a 24 hr incubation period (Day 2), the medium is exchanged. The medium can be saved for further analysis of cytokines or other endpoints of interest. After the medium exchange, tissues are incubated for an additional 18 hours. At the end of the entire 42h post-incubation (day 3), the tissues are transferred into yellow MTT solution and incubated for 3 hours. The resultant purple-blue formazan salt, formed mainly by mitochondrial metabolism, is extracted for 2 hours using isopropanol. The optical density of the extracted formazan is determined using a spectrophotometer. A chemical is classified as an irritant if the tissue viability relative to the negative control treated tissues is reduced below 50%. This procedure can be used as full replacement of the in vivo rabbit skin irritation test for hazard identification and labeling of chemicals in line with EU regulations (7).

An In Vitro Skin Irritation Test SIT using the EpiDerm Reconstructed Human Epidermal RHE Model

In this video, we demonstrate the EpiDerm Skin Irritation test (EpiDerm SIT) developed and validated for in vitro skin irritation testing of chemicals, including cosmetic and pharmaceutical ingredients.

The EpiDerm Skin Irritation test (EpiDerm SIT) was developed (1,2,3) and validated (4,5) for in vitro skin irritation testing of chemicals, including ...

Biology

A Chronic Autoimmune Dry Eye Rat Model with Increase in Effector Memory T Cells in Eyeball Tissue

Dry eye disease is a very common condition that causes morbidity and healthcare burden and decreases the quality of life. There is a need for a suitable dry eye animal model to test novel therapeutics to treat autoimmune dry eye conditions. This protocol describes a chronic autoimmune dry eye rat model. Lewis rats were immunized with an emulsion containing lacrimal gland extract, ovalbumin, and complete Freund&#39;s adjuvant. A second immunization with the same antigens in incomplete Freund&#39;s adjuvant was administered two weeks later. These immunizations were administered subcutaneously at the base of the tail. To boost the immune response at the ocular surface and lacrimal glands, lacrimal gland extract and ovalbumin were injected into the forniceal subconjunctiva and lacrimal glands 6 weeks after the first immunization. The rats developed dry eye features, including reduced tear production, decreased tear stability, and increased corneal damage. Immune profiling by flow cytometry showed a preponderance of CD3+ effector memory T cells in the eyeball.

This report describes a method to induce chronic experimental autoimmune dry eye in Lewis rats through immunization with an emulsion of rat lacrimal gland extract, ovalbumin, and complete Freund's adjuvant, followed by the injection of lacrimal gland extract and ovalbumin into the forniceal subconjunctiva and lacrimal glands six weeks later.

Dry eye disease is a very common condition that causes morbidity and healthcare burden and decreases the quality of life. There is a need for a suitable ...

Immunology and Infection

Cultivating a Three-dimensional Reconstructed Human Epidermis at a Large Scale

A three-dimensional human epidermis model reconstructed from neonatal primary keratinocytes is presented. Herein, a protocol for the cultivation process and the characterization of the model is described. Neonatal primary keratinocytes are grown submerged on permeable polycarbonate inserts and lifted to the air-liquid interface three days after seeding. After fourteen days of stimulation with defined growth factors and ascorbic acid in high calcium culture medium, the model is fully differentiated. Histological analysis revealed a completely stratified epidermis, mimicking the morphology of native human skin. To characterize the model and its barrier functions, protein levels and localization specific for early-stage keratinocyte differentiation (i.e., keratin 10), late-stage differentiation (i.e., involucrin, loricrin, and filaggrin) and tissue adhesion (i.e., desmoglein 1), were assessed by immunofluorescence. The tissue barrier integrity was further evaluated by measuring transepithelial electrical resistance. Reconstructed human epidermis was responsive to proinflammatory stimuli (i.e., lipopolysaccharide and tumor necrosis factor alpha), leading to increased cytokine release (i.e., interleukin 1 alpha and interleukin 8). This protocol represents a straightforward and reproducible in vitro method to cultivate reconstructed human epidermis as a tool to assess environmental effects and a broad range of skin-related studies.

This protocol describes a straightforward method to cultivate three-dimensional reconstituted human epidermis in a reproducible and robust manner. Additionally, it characterizes the structure-function relationship of the epidermal barrier model. The biological responses of the reconstituted human epidermis upon proinflammatory stimuli are also presented.

A three-dimensional human epidermis model reconstructed from neonatal primary keratinocytes is presented. Herein, a protocol for the cultivation process ...

A Rabbit Model of Aqueous-Deficient Dry Eye Disease Induced by Concanavalin A Injection into the Lacrimal Glands: Application to Drug Efficacy Studies

Dry eye disease (DED), a multifactorial inflammatory disease of the ocular surface, affects 1 in 6 humans worldwide with staggering implications for quality of life and health care costs. The lack of informative animal models that recapitulate its key features impedes the search for new therapeutic agents for DED. Available DED animal models have limited reproducibility and efficacy. A model is presented here in which DED is induced by injecting the mitogen concanavalin A (Con A) into the orbital lacrimal glands of rabbits. Innovative aspects of this model are the use of ultrasound (US) guidance to ensure optimal and reproducible injection of Con A into the inferior lacrimal gland; injection of Con A into all orbital lacrimal glands that limits compensatory production of tears; and use of periodic repeat injections of Con A that prolong the state of DED at will. DED and its response to test agents are monitored with a panel of parameters that assess tear production, the stability of the tear film, and the status of the corneal and conjunctival mucosa. They include tear osmolarity, tear break-up time, Schirmer&#39;s tear test, rose bengal staining, and tear lactoferrin levels. The induction of DED and the monitoring of its parameters are described in detail. This model is simple, robust, reproducible, and informative. This animal model is suitable for the study of tear physiology and of the pathophysiology of DED as well as for the assessment of the efficacy and safety of candidate agents for the treatment of DED.

This article describes the development of a method to induce acute or chronic dry eye disease in rabbits by injecting concanavalin A to all portions of the orbital lacrimal gland system. This method, superior to those already reported, generates a reproducible, stable model of dry eye suitable for the study of pharmacological agents.

Dry eye disease (DED), a multifactorial inflammatory disease of the ocular surface, affects 1 in 6 humans worldwide with staggering implications for ...

Medicine

Scopolamine-Induced Lacrimal Gland Dysfunction in Rats

A Rat Dry Eye Model with Lacrimal Gland Dysfunction Induced by Scopolamine

Aqueous-deficient dry eye (ADDE) is a type of dry eye disease that can result in the reduction of tear secretion quantity and quality. Prolonged abnormal tear production can lead to a disturbance in the ocular surface environment, including corneal damage and inflammation. In severe cases, ADDE can cause vision loss or even blindness. Currently, dry eye treatment is limited to eye drops or physical therapy, which can only alleviate eye discomfort symptoms and cannot fundamentally cure dry eye syndrome. To restore the function of the lacrimal gland in dry eye, we have created an animal model of lacrimal gland dysfunction in rats induced by scopolamine. Through the comprehensive evaluation of the lacrimal gland, corneas, conjunctivas, and other factors, we aim to provide a full understanding of the pathological changes of ADDE. Compared with the current dry eye mouse model, this ADDE animal model includes a functional evaluation of the lacrimal gland, providing a better platform for studying lacrimal gland dysfunction in ADDE.

Author Spotlight: Challenges in Developing Dry Eye Animal Models and Future Research Directions

Here, we establish a rat model of lacrimal gland dysfunction to provide a basis for the study of aqueous-deficient dry eye.

Aqueous-deficient dry eye (ADDE) is a type of dry eye disease that can result in the reduction of tear secretion quantity and quality. Prolonged abnormal ...

Determining the Toxicity of UV Radiation and Chemicals on Primary and Immortalized Human Corneal Epithelial Cells

This article describes the methods of measuring the toxicity of ultraviolet (UV) radiation and ocular toxins on primary (pHCEC) and immortalized (iHCEC) human corneal epithelial cell cultures. Cells were exposed to UV radiation and toxic doses of benzalkonium chloride (BAK), hydrogen peroxide (H2O2), and sodium dodecyl sulfate (SDS). Metabolic activity was measured using a metabolic assay. The release of inflammatory cytokines was measured using a multi-plex interleukin (IL)-1&#946;, IL-6, IL-8, and tumor necrosis factor-alpha (TNF-&#945;) assay, and cells were evaluated for viability using fluorescent dyes. 
The damaging effects of UV on cell metabolic activity and cytokine release occurred at 5 min of UV exposure for iHCEC and 20 min for pHCEC. Similar percent drops in metabolic activity of the iHCEC and pHCEC occurred after exposure to BAK, H2O2, or SDS, and the most significant changes in cytokine release occurred for IL-6 and IL-8. Microscopy of fluorescently stained iHCEC and pHCEC BAK-exposed cells showed cell death at 0.005% BAK exposure, although the degree of ethidium staining was greater in the iHCECs than pHCECs. Utilizing multiple methods of assessing toxic effects using microscopy, assessments of metabolic activity, and cytokine production, the toxicity of UV radiation and chemical toxins could be determined for both primary and immortalized cell lines.

This article describes the procedures used to evaluate the toxicity of UV radiation and chemical toxins on a primary and immortalized cell line.

This article describes the methods of measuring the toxicity of ultraviolet (UV) radiation and ocular toxins on primary (pHCEC) and immortalized (iHCEC) ...

Organ Culture System for Assessing the Toxicity of Intraocular Treatment Excipients and Pharmaceuticals

As the leading cause of blindness, cataracts are a significant burden for the tens of millions of people affected globally by this condition. Chemical exposures, among other environmental factors, are an established cause of cataracts. Ocular toxicity testing can assess whether pharmaceuticals and their components may contribute to lens damage that may lead to cataracts or aid the treatment of cataracts. 
In vitro studies and in vivo animal testing can be used for assessing the safety of chemicals prior to clinical studies. The Draize test-the current in vivo standard for ocular toxicity and irritancy testing-has been criticized for lack of sensitivity and objective measurements of determining ocular toxicity. In vitro cell-based assays are limited as cell cultures cannot appropriately model an intact functional lens. 
The method described here is a sensitive in vitro alternative to animal testing, designed to evaluate the response of the intact bovine lens to treatment at both the cellular activity level and for overall refractive performance. The non-toxic reagent resazurin is metabolized in proportion to the level of cell activity. The lens laser-scanner assay measures the ability of the lens to refract incident beams of light to a single point with minimal error, directly relevant to its natural function. The method may be used to determine both acute and delayed changes in the lens, as well as the recovery of the lens from chemical or environmental exposures.

The goal of this protocol is to evaluate changes in metabolic activity and refractive function of the lens in response to experimental treatment.

As the leading cause of blindness, cataracts are a significant burden for the tens of millions of people affected globally by this condition. Chemical ...

Assessment of Cornea and Tear Smoothness in an Autoimmune Dry Eye Rat Model

Source: Hou, A. et al., <a href="https://appjove.unicartagenaproxy.elogim.com/v/55592">A Chronic Autoimmune Dry Eye Rat Model with Increase in Effector Memory T Cells in Eyeball Tissue.</a>&#160;J. Vis. Exp. (2017)
This video demonstrates a method for assessing corneal smoothness and tear film stability in an autoimmune rat model. It highlights the impact of gland dysfunction on tear film stability, crucial for understanding dry eye disease.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
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JoVE Encyclopedia of Experiments

Immunology

Immunopathology

Assay and Analysis

A Method to Induce Ocular Surface Inflammation in a Murine Model

To perform intraperitoneal injection of the immunogen solution, hold the 7 to 9-weeks-old C57 Black 6 non-anesthetized female mouse softly by the tail while grasping the cage grid. Then, firmly hold the skin at the back and the neck region between the thumb and index finger and fix the tail and lower limbs between the ring and little finger against the palm. Keeping the mouse fixed with its head downward, inject 100 microliters of the prepared immunogen solution in the right or left quadrant of the lower abdominal cavity.
To perform an ocular surface challenge after immunization, apply 5 microliters of ovalbumin, or ova, or saline per eye of an anesthetized mouse, and wait for 5 minutes to get the drop absorbed by the eye. Next, collect the ocular exudates by applying 50 microliters of sterile saline to the eye immediately after the challenge.