A summary report of the COLIPA international validation study on alternatives to the draize rabbit eye irritation test

Brazilian National Network of Alternative Methods (RENAMA) 10th Anniversary: Meeting of the Associated Laboratories, May 2022

The Brazilian National Network of Alternative Methods (RENAMA), which is linked to the Ministry of Science, Technology and Innovation, is currently comprised of 51 laboratories from CROs, academia, industry and government. RENAMA's aim is to develop and validate new approach methodologies (NAMs), as well as train researchers and disseminate information on their use - thus reducing Brazilian, and consequently Latin American, dependence on external technology. Moreover, it promotes the adoption of NAMs by educators and trained researchers, as well as the implementation of good laboratory practice (GLP) and the use of certified products. The RENAMA network started its activities in 2012, and was originally comprised of three central laboratories - the National Institute of Metrology, Quality and Technology (INMETRO); the National Institute of Quality Control in Health (INCQS); and the National Brazilian Biosciences Laboratory (LNBio) - and ten associated laboratories. In 2022, RENAMA celebrated its 10th anniversary, a milestone commemorated by the organisation of a meeting attended by different stakeholders, including the RENAMA-associated laboratories, academia, non-governmental organisations and industry. Ninety-six participants attended the meeting, held on 26 May 2022 in Balneário Camboriú, SC, Brazil, as part of the programme of the XXIII Brazilian Congress of Toxicology 2022. Significant moments of the RENAMA were remembered, and new goals and discussion themes were established. The lectures highlighted recent innovations in the toxicological sciences that have translated into the assessment of consumer product safety through the use of human-relevant NAMs instead of the use of existing animal-based approaches. The challenges and opportunities in accepting such practices for regulatory purposes were also presented and discussed.

Comparison between HET-CAM protocols and a product use clinical study for eye irritation evaluation of personal care products including cosmetics according to their surfactant composition

The hen's egg test on chorioallantoic membrane (HET-CAM) is one of the most frequently used alternative tests for prediction of ocular irritation of cosmetic products. There are different HET-CAM protocols widely accepted, but there is no information about which of the protocols better correlates with the results obtained in product use clinical study under the conditions of use. Two Fix Time Methods (FTM) -Lüepke and the ICCVAM guideline - and two Reaction Time Methods (RTM) -ECVAM DBALM Prot. No. 47 and No. 96- were employed to test 18 cosmetic products. Simultaneously, they were evaluated by an ophthalmological clinical test. A unified classification system was used, and products were classified into four irritation levels: non-irritant, weak, moderate and severe irritant. The duration of use (rinse-off or leave-on), and the concentration and type of surfactants were taken into account in the analysis. All the products that were classified as non-irritant by any HET-CAM protocols were also safe in the product use clinical study. The product that was found to be non-safe in the product use clinical evaluation was also unsuitable by most of the HET-CAM protocols. These results were employed to develop an algorithm that allows selecting the appropriate HET-CAM protocol for each type of product to be tested.

In vitro reconstructed 3D corneal tissue models for ocular toxicology and ophthalmic drug development

Testing of all manufactured products and their ingredients for eye irritation is a regulatory requirement. In the last two decades, the development of alternatives to the in vivo Draize eye irritation test method has substantially advanced due to the improvements in primary cell isolation, cell culture techniques, and media, which have led to improved in vitro corneal tissue models and test methods. Most in vitro models for ocular toxicology attempt to reproduce the corneal epithelial tissue which consists of 4-5 layers of non-keratinized corneal epithelial cells that form tight junctions, thereby limiting the penetration of chemicals, xenobiotics, and pharmaceuticals. Also, significant efforts have been directed toward the development of more complex three-dimensional (3D) equivalents to study wound healing, drug permeation, and bioavailability. This review focuses on in vitro reconstructed 3D corneal tissue models and their utilization in ocular toxicology as well as their application to pharmacology and ophthalmic research. Current human 3D corneal epithelial cell culture models have replaced in vivo animal eye irritation tests for many applications, and substantial validation efforts are in progress to verify and approve alternative eye irritation tests for widespread use. The validation of drug absorption models and further development of models and test methods for many ophthalmic and ocular disease applications is required.

The Use of Simultaneous Fluorescence and Differential Phase Confocal Microscopy to Study Alamar Blue™ Reduction in an Epithelial Cell Line

The Alamar Blue™ reduction assay is used as an indicator of cellular viability in in vitro tests for the prediction of ocular irritancy. Alamar Blue itself has a low cytotoxicity, so repeat exposure and recovery studies can be performed on the same cells. This paper contains the results of a preliminary investigation of interactions between the Alamar Blue dye and a confluent monolayer of epithelial Madin-Darby canine kidney cells. This was performed by using an experimental fluorescence microscope and differential phase confocal microscope designed for studying live samples in vitro. The initiation of Alamar Blue reduction to its fluorescent product did not occur at the same time in all cells, but started in a small number and spread progressively through their immediate neighbours. There was clear localisation of the reduced (fluorescent) Alamar Blue within the nuclei and other organelles.

Skin irritation potential of cosmetic preservatives: An exposure-relevant study

BACKGROUND

Preservatives represent one of the main causes of skin irritation and contact allergies.

AIMS

To comprehensively evaluate the skin irritation potential of phenoxyethanol, methylparaben, propylparaben, imidazolidinyl urea, and DMDM hydantoin under regulatory acceptable concentrations.

METHODS

A patch test and repeated open application test (ROAT) were applied to evaluate skin irritation in vivo. In vitro alternative methods consisting of the keratinocyte cytotoxicity assay, red blood cell (RBC) test, and hen's egg test-chorioallantoic membrane (HET-CAM) were performed to elucidate the mechanism of preservative-induced irritation responses.

RESULTS

The patch test showed that all test substances showed a weak erythema response. Propylparaben had the highest occlusive irritancy potential in the patch test, owing to damage to the cell membrane. The two formaldehyde releasers showed noticeable skin irritation potential in the ROAT through their cytotoxicity to keratinocytes, while a visible response was observed after applying phenoxyethanol and the two parabens. No filtration was noticed in the in vivo tests, which might be attributed to the failure of subcutaneous vessel alteration by the preservatives.

CONCLUSIONS

Commonly used cosmetic preservatives have minor skin irritation potential with mild erythema reaction under practical use, especially formaldehyde releasers and propylparaben.

Assessing the dyeing efficiency and irritation potentials of plant hair dyes: A multi-analytical in vitro approach

BACKGROUND

The interest toward dyeing hairs with plant colorants has grown in popularity considering its low-toxic nature. However, researches reporting plant hair dyes are limited and the potential adverse effects of irritation are unclear.

OBJECTIVES

This study is aimed to provide an avenue by which to more accurately assess the dyeing efficiency and irritation potentials of plant hair dyes.

METHODS

Four extracted plant colorants were incorporated in hydrogel hair dyes that were directly applied on unbleached gray human hairs. Their dyeing performances and the effect of an iron (Ⅱ) mordant were photometrically measured in CIELab coordinates and color strength. The eye and skin irritancy was assessed by combining various in vitro methods, including bovine corneal opacity and permeability (BCOP) assay in combination with histopathological analysis, Hen's egg test on chick chorioallantoic membrane (HET-CAM) and a test on reconstructed human epidermis models.

RESULTS

The investigated hair dyes exhibited desirable dyeing efficiency on human hairs. Post-treatment with the iron (Ⅱ) mordant caused a significant increase in color strength with subtle changes to the hue of dyed color. In the irritation testing, the four hair dyes were categorized as slight-to-mild eye irritants but possessed no skin irritation potential, while the mordant was determined as a non-irritant.

CONCLUSIONS

The results demonstrate the efficacy of a multi-analytical approach for in vitro assessment of various plant colorants for hair dyeing. The investigated plant extracts are suitable for producing viable colors on human hairs and may serve as a low-irritating alternative to the synthetic hair dyes.

Assessment of the Eye Irritating Properties of Chemicals by Applying Alternatives to the Draize Rabbit Eye Test: The Use of QSARs and In Vitro Tests for the Classification of Eye Irritation

Huggins has reported on the current situation relating to the development of alternatives to the Draize eye irritation test with rabbits, and an ECVAM Working Group have reviewed the efforts needed in order to replace this animal test within the next 10 years by using the results of non-animal assessment methods. Our report reviews regulatory experience gained over the last 20 years with the EU chemicals notification procedure with respect to the assessment of eye lesions observed in Draize tests. The nature of eye lesions and their importance for classification and labelling of possible hazards to human eyes are evaluated and discussed, with a view to promoting the development of specific in vitro assays which are able to discriminate between eye damage, moderate eye irritation, and minor irritation effects which are completely reversible within a few days. Structural alerts for the prediction of eye irritation/corrosion hazards to be classified and labelled according to international classification criteria, are presented, which should be validated in accordance with internationally agreed (OECD) principles for (Q)SAR system validation. Physicochemical limit values for prediction of the absence of any eye irritation potential relevant for human health can make available a definition of the applicability domains of alternative methods developed for the replacement of the Draize eye irritation test.

Biostatistical Methods for the Validation of Alternative Methods for In Vitro Toxicity Testing

Statistical methods for the validation of toxicological in vitro test assays are developed and applied. Validation is performed either in comparison with in vivo assays or in comparison with other in vitro assays of established validity. Biostatistical methods are presented which are of potential use and benefit for the validation of alternative methods for the risk assessment of chemicals, providing at least an equivalent level of protection through in vitro toxicity testing to that obtained through the use of current in vivo methods. Characteristic indices are developed and determined. Qualitative outcomes are characterised by the rates of false-positive and false-negative predictions, sensitivity and specificity, and predictive values. Quantitative outcomes are characterised by regression coefficients derived from predictive models. The receiver operating characteristics (ROC) technique, applicable when a continuum of cut-off values is considered, is discussed in detail, in relation to its use for statistical modelling and statistical inference. The methods presented are examined for their use for the proof of safety and for toxicity detection and testing. We emphasise that the final validation of toxicity testing is human toxicity, and that the in vivo test itself is only a predictor with an inherent uncertainty. Therefore, the validation of the in vitro test has to account for the vagueness and uncertainty of the "gold standard" in vivo test. We address model selection and model validation, and a four-step scheme is proposed for the conduct of validation studies. Gaps and research needs are formulated to improve the validation of alternative methods for in vitro toxicity testing.

The FRAME Alternatives Laboratory Database. 1. In Vitro Basal Cytotoxicity determined by the Kenacid Blue Total Protein Assay

A database of over 280 chemicals has been compiled by using a mouse 3T3-L1 fibroblast-like cell line in exponential growth, exposed to chemicals for 72 hours in a 96-well tissue culture plate format, and determining cell number via the Kenacid blue (KB) assay for total protein. Ranking the chemicals according to their basal cytotoxicity, expressed as the concentration (mM) that inhibits increase in total cellular protein over 72 hours by 50% (the ID50 value) shows a wide range of ID50 values, from 0.00003mM to 10,096mM. This information includes the results for MEIC chemicals 1–50, and we have now added basal cytotoxicity data for 23 of the next 25 MEIC chemicals. When the neutral red uptake (NRU) assay was performed with the same cell cultures, before the KB assay, very similar indications of basal cytotoxicity were obtained. Comparisons between the results with 3T3-L1 cells and with a human fibroblast-like cell line, BCL-D1 showed a significant difference in order of magnitude of the ID50 value for only 5 of 52 chemicals. However, there was a difference in ID50 value of more than one order of magnitude for 8 of 24 chemicals tested with an undifferentiated teratocarcinoma cell line, F9.

A Human Corneal Equivalent Constructed from SV40-immortalised Corneal Cell Lines

Within the last decade, extensive research in the field of tissue and organ engineering has focused on the development of in vitro models of the cornea. The use of organotypic, three-dimensional corneal equivalents has several advantages over simple monolayer cultures. The aim of this study was to develop a corneal equivalent model composed of the same cell types as in the natural human tissue, but by using immortalised cell lines to ensure reproducibility and to minimise product variation. We report our success in the establishment of an SV40-immortalised human corneal keratocyte cell line (designated HCK). A collagen matrix, built up with these cells, displayed the morphological characteristics of the human stromal tissue and served as a biomatrix for the immortalised human corneal epithelial and endothelial cells. Histological cross-sections of the whole-cornea equivalents resemble human corneas in tissue structure. This organotypic in vitro model may serve as a research tool for the ophthalmic science community, as well as a model system for testing for eye irritancy and drug efficacy.

Cosmetics Europe compilation of historical serious eye damage/eye irritation in vivo data analysed by drivers of classification to support the selection of chemicals for development and evaluation of alternative methods/strategies: the Draize eye test Reference Database (DRD)

A thorough understanding of which of the effects assessed in the in vivo Draize eye test are responsible for driving UN GHS/EU CLP classification is critical for an adequate selection of chemicals to be used in the development and/or evaluation of alternative methods/strategies and for properly assessing their predictive capacity and limitations. For this reason, Cosmetics Europe has compiled a database of Draize data (Draize eye test Reference Database, DRD) from external lists that were created to support past validation activities. This database contains 681 independent in vivo studies on 634 individual chemicals representing a wide range of chemical classes. A description of all the ocular effects observed in vivo, i.e. degree of severity and persistence of corneal opacity (CO), iritis, and/or conjunctiva effects, was added for each individual study in the database, and the studies were categorised according to their UN GHS/EU CLP classification and the main effect driving the classification. An evaluation of the various in vivo drivers of classification compiled in the database was performed to establish which of these are most important from a regulatory point of view. These analyses established that the most important drivers for Cat 1 Classification are (1) CO mean ≥ 3 (days 1-3) (severity) and (2) CO persistence on day 21 in the absence of severity, and those for Cat 2 classification are (3) CO mean ≥ 1 and (4) conjunctival redness mean ≥ 2. Moreover, it is shown that all classifiable effects (including persistence and CO = 4) should be present in ≥60 % of the animals to drive a classification. As a consequence, our analyses suggest the need for a critical revision of the UN GHS/EU CLP decision criteria for the Cat 1 classification of chemicals. Finally, a number of key criteria are identified that should be taken into consideration when selecting reference chemicals for the development, evaluation and/or validation of alternative methods and/or strategies for serious eye damage/eye irritation testing. Most important, the DRD is an invaluable tool for any future activity involving the selection of reference chemicals.

Estimation of the chemical-induced eye injury using a weight-of-evidence (WoE) battery of 21 artificial neural network (ANN) c-QSAR models (QSAR-21): part I: irritation potential

Evaluation of potential chemical-induced eye injury through irritation and corrosion is required to ensure occupational and consumer safety for industrial, household and cosmetic ingredient chemicals. The historical method for evaluating eye irritant and corrosion potential of chemicals is the rabbit Draize test. However, the Draize test is controversial and its use is diminishing - the EU 7th Amendment to the Cosmetic Directive (76/768/EEC) and recast Regulation now bans marketing of new cosmetics having animal testing of their ingredients and requires non-animal alternative tests for safety assessments. Thus, in silico and/or in vitro tests are advocated. QSAR models for eye irritation have been reported for several small (congeneric) data sets; however, large global models have not been described. This report describes FDA/CFSAN's development of 21 ANN c-QSAR models (QSAR-21) to predict eye irritation using the ADMET Predictor program and a diverse training data set of 2928 chemicals. The 21 models had external (20% test set) and internal validation and average training/verification/test set statistics were: 88/88/85(%) sensitivity and 82/82/82(%) specificity, respectively. The new method utilized multiple artificial neural network (ANN) molecular descriptor selection functionalities to maximize the applicability domain of the battery. The eye irritation models will be used to provide information to fill the critical data gaps for the safety assessment of cosmetic ingredient chemicals.

A Comparison of Three Cytotoxicity Endpoints in the Corneal HCE-T Model

The prediction of ocular irritation potential from in vitro assays still presents a problem, despite a number of validation trials. A study with coded cosmetic formulations, for which historic in vivo data were available, has been conducted with a human corneal multi-layered model system. This corneal model, the HCE-T model, was developed by using HCE-T cells, a transfected human corneal epithelial cell line. The relative effectiveness of three endpoints that provide a measure of cytotoxicity in the HCE-T model was evaluated. Cell viability immediately after exposure to the test materials was determined by using the MTT and Alamar Blue™ (AB) assays, and, 24 hours later, by using the MTT, AB and lactate assays. Viability measurements with the MTT, AB and lactate assays gave similar dose-response curves at the 24-hour endpoint. One formulation (an anti-dandruff shampoo) caused a less severe drop in viability in assays conducted immediately after the exposure than at the 24-hour time-point. There was little deterioration in viability with the other test materials. The ranking of the test formulations on the basis of relative loss of viability and release of lactate resulted in the same order as for the Modified Maximum Average Draize Test Score. Comparison of the HCE-T model cytotoxicity assay results with historic in vitro data from two different cytotoxicity assays, conducted by using fibroblast monolayer cultures and the same materials, indicated that the multi-layered corneal model had a greater predictive ability. The results of a blind trial with the lactate assay in two laboratories indicated that the techniques required were transferable between laboratories. The lactate results were reproducible between laboratories, even when cultures derived from different passage human corneal cells were tested, provided that the passage number was below 20.

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

For more than two decades, scientists have been trying to replace the regulatory in vivo Draize eye test by in vitro methods, but so far only partial replacement has been achieved. In order to better understand the reasons for this, historical in vivo rabbit data were analysed in detail and resampled with the purpose of (1) revealing which of the in vivo endpoints are most important in driving United Nations Globally Harmonized System/European Union Regulation on Classification, Labelling and Packaging (UN GHS/EU CLP) classification for serious eye damage/eye irritation and (2) evaluating the method’s within-test variability for proposing acceptable and justifiable target values of sensitivity and specificity for alternative methods and their combinations in testing strategies. Among the Cat 1 chemicals evaluated, 36–65 % (depending on the database) were classified based only on persistence of effects, with the remaining being classified mostly based on severe corneal effects. Iritis was found to rarely drive the classification (<4 % of both Cat 1 and Cat 2 chemicals). The two most important endpoints driving Cat 2 classification are conjunctiva redness (75–81 %) and corneal opacity (54–75 %). The resampling analyses demonstrated an overall probability of at least 11 % that chemicals classified as Cat 1 by the Draize eye test could be equally identified as Cat 2 and of about 12 % for Cat 2 chemicals to be equally identified as No Cat. On the other hand, the over-classification error for No Cat and Cat 2 was negligible (<1 %), which strongly suggests a high over-predictive power of the Draize eye test. Moreover, our analyses of the classification drivers suggest a critical revision of the UN GHS/EU CLP decision criteria for the classification of chemicals based on Draize eye test data, in particular Cat 1 based only on persistence of conjunctiva effects or corneal opacity scores of 4. In order to successfully replace the regulatory in vivo Draize eye test, it will be important to recognise these uncertainties and to have in vitro tools to address the most important in vivo endpoints identified in this paper.

Assessment of the dermal and ocular irritation potential of lomefloxacin by using in vitro methods

The evaluation of eye and skin irritation potential is essential to ensuring the safety of human in contact with a wide variety of substances. Despite this importance of irritation test, little is known with respect to the irritation potency of lomefloxacin, a fluoroquinolone antibiotic, which has been known to cause phototoxicity with an abnormal reaction of the skin. Thus, to investigate the tendency of lomefloxacin to cause eye and skin irritation, we carried out in vitro eye irritation test using Balb/c 3T3, and in vitro skin irritation test using KeraSkin^TM human skin model system. 3T3 neutral red uptake assay has been proposed as a potential replacement alternative for the Draize Eye irritation test. In this study, the IC₅₀ value obtained for lomefloxacin was 375 μg. According to the classification model used for determining in vitro categories, lomefloxacin was classified as moderately irritant. For evaluation of skin irritation, engineered epidermal equivalents (KeraSkin^TM) were subjected to 10 and 25 mg of lomefloxacin for 15 minutes. Tissue damage was assessed by tissue viability evaluation, and by the release of a pro-inflammatory mediator, interleukin-1α. Lomefloxacin increased the interleukin-1α release after 15 minutes of exposure and 42 hours of post incubation, although no decrease in viability was observed. Therefore, lomefloxacin is considered to be moderately irritant to skin and eye.

Assessment of Initial Damage and Recovery Following Exposure of MDCK Cells to an Irritant

The ability of Madin-Darby canine kidney cells (MDCK ) to form cell tight-junctions and orientate correctly on porous membranes has been exploited to model corneal barrier function. While the ability to monitor recovery profiles has not yet been included in a prevalidation trial, its inclusion facilitates the prediction of potential adverse reactions. Combining a viability assay (Alamar blue reduction) with the fluorescein leakage assay, the chemical effects on cell membrane and adhesion molecules can be distinguished. The dose-response curves obtained with Tween 20, isopropanol and benzalkonium chloride indicate that Tween 20 at 200mg/ml caused a 50% decline in Alamar blue reduction and fluorescein retention, while 100mg isopropanol/ml and 0.1mg benzalkonium chloride/ml cause similar effects. The more severe the initial damage the longer the recovery period. If a 20% increase in fluorescein leakage gave recovery in 48 hours, 50% gave marginal recovery in 96 hours. Comparable effects were noted for the restoration of the ability to reduce the Alamar blue dye. Resolution of the damaging effects of benzalkonium chloride and isopropanol took longer than for Tween 20, as is the case in the rabbit in vivo.

Performance of the Neutral Red uptake assay in the COLIPA international validation study on alternatives to the rabbit eye irritation test

The neutral red uptake (NRU) assay was included as part of the COLIPA international validation trial of in vitro alternatives to the Draize eye irritation test. In a blind trial, 55 substances were tested at four laboratories. Following testing, a prediction of the in vivo Draize modified maximum average score (MMAS) for each substance was made by each laboratory using a prediction model relating mean NR(50) value (concentration causing 50% reduction in NRU from that of untreated control cells) to MMAS. Following statistical analysis of the results and breaking of the code, assessment of the results and further analysis was carried out by the participating laboratories. This paper presents the conclusions with regard to the NRU assay. The initial trial analysis indicated that the interlaboratory reproducibility of results of the NRU assay was good. However, there was a poor correlation between observed and predicted MMAS (using the proposed prediction model) when all the test substances were analysed together (r=0.246). Data analysis of subsets of substances indicated that the best predictions were for pure surfactants only (r=0.843) although this data did not fit within the limits of the prediction model. The NRU assay therefore appears to have limited use as a complete Draize replacement. A further examination of the COLIPA trial data may identify combinations of assays which may be more useful than the individual assays which, like NRU, have been shown to be poor predictors of eye irritation.

The Performance of the Tissue Equivalent Assay using the Skin(2)(TM) ZK1200 Model in the COLIPA International Validation Study on Alternatives to the Draize Eye Irritation Test

The tissue equivalent assay (TEA) (Osborne et al., 1995) was used to evaluate 55 mixed ingredients and formulations in the COLIPA International Validation Study on Alternatives to the Draize Rabbit Eye Irritation Test (Brantom et al., 1997). The TEA can be used to test all types of materials since it uses a topical application approach and is not limited to only testing liquid or soluble materials. A prediction model (PM) for the test was developed using historical eye irritation data from a total of 132 materials on which in vivo and in vitro data were available. A regression model was derived from these data and used to relate the in vitro endpoint (t(50)) obtained in the study to a Draize MMAS (modified maximum average score). This provided a measure of the predicted in vivo eye irritation scores. In the current study, two separate laboratories used the same protocol to test the same set of coded materials and the results of both laboratories were compared to the initial PM. The TEA met the reliability criteria of the validation study in reproducing the predefined PM in both laboratories, and a good relationship between predicted and observed Draize MMAS values was obtained (r=0.906 and r=0.850). Good correlations were maintained when separate analyses were made of the formulations and ingredients included in the test set. Good relationships between the in vitro endpoint and individual Draize tissue scores (r>0.8) were also exhibited. Although insufficient data were available to make an assessment of interlaboratory variation, some difference in the reproducibility of the assay was noted between the two laboratories, particularly for the highly irritating materials. However, the consistency of data was encouraging and the discrepancies seen between the laboratories suggested a sensitivity of the model to subtle differences in application techniques, and in handling and timing. Taken together, these results indicate the utility of the TEA test for these types of substances and the need to more fully address the issue of interlaboratory reproducibility.

Protein based nanoparticles as platforms for aspirin delivery for ophthalmologic applications

Most conventional ophthalmic dosage forms, though simplistic are limited by poor bioavailability in the posterior chamber of the eye. Application of nanotechnology has the potential to overcome this problem. By varying aspirin albumin ratios from 0.06 to 1.0, we obtained electrokinetically stable, pharmacologically active albumin based aspirin nanoparticles of <200 nm diameter with low polydispersity. In vitro release study showed nanoparticle formulation can release aspirin at a sustained rate for prolonged duration (90% at 72 h) and 11% drug release in the posterior chamber over a period of 72 h under simulated condition. Stability of the formulation was well maintained on storage for six months and after reconstitution for 24 h. The formulation showed no hemolysis in contrast to the high hemolysis due to the free drug. This study shows that aspirin loaded albumin nanoparticles prepared by coacervation holds promise as a formulation for topical delivery in diabetic retinopathy.

Eye irritation potential: usefulness of the HET-CAM under the Globally Harmonized System of classification and labeling of chemicals (GHS)

Extensive research has been conducted over the past decades to develop alternatives to the rabbit eye irritation test (Draize test) used in a regulatory context to assess eye irritation potentials. Although no single in vitro test has emerged as being completely acceptable for full replacement, various tests are considered to be suitable and are regularly used to assess certain aspects. Amongst these, the Hen's Egg Test Chorioallantoic Membrane (HET-CAM) has gained regulatory acceptance in various countries to classify severe eye irritants. In this retrospective study, historical eye irritation data (in vivo and in vitro) from 137 samples (approx. 75% non-irritants; 25% (severe) irritants) tested both in the HET-CAM and Draize eye test was compared with regard to the predicted eye irritation classes under the GHS and the traditional EU classification system (DSD).The overall concordance was in the range of 80-90%. A high specificity (96-98%, depending on the classification system and the chosen discrimination) but rather low sensitivity (48-65%) was observed. The study indicates that HET-CAM results are useful as part of weight-of-evidence assessments or in tiered approaches to assess eye irritation potentials rather than as stand-alone classification method.

Validation study of the Short Time Exposure (STE) test to assess the eye irritation potential of chemicals

Short time exposure (STE) test is a cytotoxicity test in SIRC cells (rabbit corneal cell line) that assesses eye irritation potential following a 5-min chemical exposure. This validation study assessed transferability, intra- and inter-laboratory reproducibility, and predictive capacity of STE test in five laboratories (supported by Japanese Society for Alternatives to Animal Experiments). Sodium lauryl sulfate, calcium thioglycolate, and Tween 80 were evaluated, in triplicate, using 5%, 0.5%, and 0.05% concentrations in physiological saline, to confirm transferability. Good transferability was noted when similar mean relative viabilities and rank classifications were obtained in all five laboratories and were comparable to data from test method developing laboratory. Good intra- and inter-laboratory reproducibility was obtained with four assay controls (three solvents and one positive control), and four assay controls and 25 chemicals, respectively. STE irritation category based on relative viability of a 5% solution of 25 blinded test chemicals showed good correlation with Globally Harmonized System (GHS) categories (NI; I: Cat. 1 and 2). The STE prediction model, using relative viability of the 5% and 0.05% solutions, provided an irritation rank (1, 2, or 3) that had a good correlation (above 80%), or predictive capacity, with GHS irritation ranks in all laboratories. Based on these findings, the STE test is a promising alternative eye irritation test that could be easily standardized.

Survey of ocular irritation predictive capacity using Chorioallantoic Membrane Vascular Assay (CAMVA) and Bovine Corneal Opacity and Permeability (BCOP) test historical data for 319 personal care products over fourteen years

The Chorioallantoic Membrane Vascular Assay (CAMVA) and Bovine Corneal Opacity and Permeability (BCOP) test are widely used to predict ocular irritation potential for consumer-use products. These in vitro assays do not require live animals, produce reliable predictive data for defined applicability domains compared to the Draize rabbit eye test, and are rapid and inexpensive. Data from 304 CAMVA and/or BCOP studies (319 formulations) were surveyed to determine the feasibility of predicting ocular irritation potential for various formulations. Hair shampoos, skin cleansers, and ethanol-based hair styling sprays were repeatedly predicted to be ocular irritants (accuracy rate=0.90-1.00), with skin cleanser and hair shampoo irritation largely dependent on surfactant species and concentration. Conversely, skin lotions/moisturizers and hair styling gels/lotions were repeatedly predicted to be non-irritants (accuracy rate=0.92 and 0.82, respectively). For hair shampoos, ethanol-based hair stylers, skin cleansers, and skin lotions/moisturizers, future ocular irritation testing (i.e., CAMVA/BCOP) can be nearly eliminated if new formulations are systematically compared to those previously tested using a defined decision tree. For other tested product categories, new formulations should continue to be evaluated in CAMVA/BCOP for ocular irritation potential because either the historical data exhibit significant variability (hair conditioners and mousses) or the historical sample size is too small to permit definitive conclusions (deodorants, make-up removers, massage oils, facial masks, body sprays, and other hair styling products). All decision tree conclusions should be made within a conservative weight-of-evidence context, considering the reported limitations of the BCOP test for alcohols, ketones, and solids.

The Development and Evaluation of In Vitro Alternative Assays: A Personal Perspective

Over the past 30 years, FRAME has actively participated in the development, evaluation and validation of in vitro alternative methods through the FRAME Alternatives Laboratory (FAL) in the University of Nottingham Medical School. Much has been learned through collaboration with industry (especially the cosmetics industry), other organisations (especially ECVAM), and certain individuals (notably Dr Björn Ekwall), particularly in relation to the need to use human cell cultures and to obtain, wherever possible, high-quality human data for use in in vivo/in vitro comparisons. Reference is made to the author's experience as Director of the FAL, notably in the development of in vitro assays for basal cytotoxicity, phototoxicity and the effects of repeated dosage.

Inter-laboratory study of short time exposure (STE) test for predicting eye irritation potential of chemicals and correspondence to globally harmonized system (GHS) classification

Short time exposure (STE) test using rabbit corneal cell line (SIRC) cells was developed as an alternative eye irritation test. STE test uses relative viability as the endpoint after cells are exposed to the test material at constant concentrations for 5 min. In this inter-laboratory study with 3 laboratories, 44 chemicals with a wide range of classes were evaluated for the transferability, between-lab reproducibility and predictive capacity of the STE test as an alternative eye irritation test. Globally harmonized system (GHS) classification based on Draize eye irritation test data was used as the comparative in vivo data. Transferability was assessed using standard chemicals (sodium lauryl sulfate, calcium thioglycolate, and Tween 80) and the coefficient variations (CVs) of relative viabilities between 3 labs were less than 0.13. The irritation category (Irritant or Non irritant) at each test concentration (5% and 0.05%) in STE test was the same in 3 laboratories for all 44 tested chemicals. The predictive capacity irritation category classification between STE test and GHS were compared, and a good correlation was confirmed (accuracy was 90.9% at all laboratories). In addition, the STE rankings of 1, 2, and 3 classified by the prediction model (PM) based on the relative viability at two concentrations (5% and 0.05%) were highly correlated with the GHS ranks of non-irritant, category 1, and category 2, respectively (accuracy was 75.0% at all laboratories). These results suggest that the STE test possessed easy transferability, reproducibility, good predictive performance.

FRAME and the validation process

FRAME's historical involvement in the development of the principles of validation, whereby the reliability and relevance of a procedure are established for a specific purpose, and in the practical application of the process, is summarised, and examples of participation in various validation studies on in vitro tests are reviewed. Emphasis is placed on the need for a parallel invalidation process, and on the role of ATLA as a forum for objective reporting and discussion on all aspects of the validation process.

In vitro assessment of eye irritancy using the Reconstructed Human Corneal Epithelial SkinEthic HCE model: application to 435 substances from consumer products industry

The 7th amendment of the EU Cosmetics Directive led to the ban of eye irritation testing for cosmetic ingredients in animals, effective from March 11th 2009. Over the last 20years, many efforts have been made to find reliable and relevant alternative methods. The SkinEthic HCE model was used to evaluate the in vitro eye irritancy potential of substances from a cosmetic industry portfolio. An optimized protocol based on a specific 1-h treatment and a 16-h post-treatment incubation period was first assessed on a set of 102 substances. The prediction model (PM) based on a 50% viability cut-off, allowed to draw up two classes (Irritants and Non-Irritants), with good associated sensitivity (86.2%) and specificity (83.5%). To check the robustness of the method, the evaluated set was expanded up to 435 substances. Final performances maintained a high level and were characterized by an overall accuracy value > 82% when using EU or GHS classification rules. Results showed that the SkinEthic HCE test method is a promising in vitro tool for the prediction of eye irritancy. Optimization datasets were shared with the COLIPA Eye Irritation Project Team and ECVAM experts, and reviewed as part of an ongoing progression to enter an ECVAM prospective validation study for eye irritation.

Application of the reconstructed rabbit corneal epithelium model to assess the in-vitro eye irritant test of chemicals

The rabbit corneal epithelium model (RCE model) was developed as a three-dimensional in vitro model to replace animal testing for the assessment of eye irritation. In the model, a stratified culture of rabbit corneal epithelial cells is grown at the air-liquid interface on collagen gel that acts as a parabasal membrane. Histological cross-sections show that the structure of the RCE model closely parallels that of the rabbit corneal epithelium. The eye irritation potency of test samples is estimated from the measurement of viability using the MTT assay in conjunction with the RCE model. A set of 30 chemicals belonging to different families with known in vivo Draize score was investigated with the in vitro eye irritation test using the RCE model in order to internally validate the protocol. Use of the RCE model at concentrations of 0.05%, 0.50%, and 1.00% and the calculation of the IC(50) and percentage of viability allowed the irritants to be divided into four classes. The performance of the in vitro eye irritation test at a concentration of 0.50% using the RCE model was characterized by good sensitivity (92.3%), good specificity (100%), and good accuracy (93.3%) compared with the irritation classification predicted by in vivo Draize score at concentrations of 10% and 100%. These results indicate that the RCE model may provide a useful and sensitive in vitro eye irritation test as an alternative method to the Draize test.

In vitro eye irritancy test of polyoxyethylene alkyl derivatives using a reconstructed rabbit corneal epithelium model

We have developed the Rabbit Corneal Epithelial (RCE) Model to evaluate the in vitro eye irritation potential of chemicals including pharmaceuticals, cosmetics and their raw ingredients. In the model, a stratified culture of rabbit corneal epithelial cells is grown at the air-liquid interface on an amnion acting as a parabasal membrane. The alkaline exposure was restored each day in the presence of no irritants, although with the addition of sodium lauryl sulfate (SLS), which is a major irritant, the restoration of deficit was inhibited on the RCE model in a dose-dependent manner. The results of this test were comparable with those of the Draize test, and thus, this method using the RCE model may prove to be a useful and sensitive in vitro eye irritation test. The in vitro eye irritation potential of polyoxyethylene alkyl derivatives, polyoxyethylene lauryl ether (PLE), polyoxyethylene cetyl ether (PCE), polyoxyethylene stearyl ether (PSE), polyoxyethylene oleyl ether (POE), and polyoxyethylene behenyl ether (PBE) were evaluated using the RCE model containing an alkaline exposure. POE inhibited 90.2% of the restoration of deficit at a concentration of 0.5% on the 4th day after addition. Depending on the structure, an activity relationship was defined. The polyoxyethylene alkyl derivatives had distinctly different inhibitory potencies against the restoration of deficit, according to their substitution patterns. POE inhibited the restoration of deficit greater than other polyoxyethylene alkyl derivatives on the RCE model. These results indicated that the oleyl chain of POE is an important factor for inhibiting the restoration of deficit on the RCE model.

An In Vitro Tier Evaluation for the Identification of Cosmetic Ingredients Which are Not Ocular Irritants

A tier evaluation system was assessed as an alternative method for the identification of cosmetic ingredients which are not ocular irritants. The system employed monolayer cultures of SIRC cells, an established cell line originally derived from the rabbit cornea, and a three-dimensional living dermal model (LDM), MATREX™, which consists of human dermal fibroblasts in a contracted collagen lattice. Effects on the cell monolayer cultures were determined by using SIRC cell-Crystal Violet staining (SIRC-CVS), and effects on the LDM were assessed by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. A non-irritating ingredient was defined as a compound having a maximal average total score (MAS) of 5 or less in the Draize eye test, as this is the criterion used in the Japanese draft guidance for evaluating cosmetic ingredients. Among 34 test substances with known characteristics, 30 were classified accurately. Based on these encouraging results, the possibility of simplifying the MTT assay on the LDM for more-practical use, by selecting only three concentration levels to discriminate non-irritants from irritants, was assessed. The simplified method, involving a three-dose set (the three-dose method), was confirmed as being suitable for the identification of non-irritating ingredients, with triethanolamine used as a negative reference standard. Finally, the LDM was used to evaluate compounds at similar concentrations to those tested in vivo, aiming to predict the concentration at which an ingredient can be formulated into products without causing eye irritation. On the basis of previous validation data and our additional results, it was found that test samples that resulted in a cell viability of 50% or more in this model, could be classified as non-irritating ingredients. In all, these results indicate that the tier evaluation system may be suitable for the evaluation of ingredients intended to be used in cosmetics and medicated cosmetics in Japan.

An Integrated Decision-tree Testing Strategy for Eye Irritation with Respect to the Requirements of the EU REACH Legislation

This paper presents some results of a joint research project, sponsored by Defra and conducted by FRAME and Liverpool John Moores University, on the status of alternatives to animal testing with regard to the European Union REACH (Registration, Evaluation and Authorisation of Chemicals) system for the safety testing and risk assessment of chemicals. The project covered all the main toxicity endpoints associated with REACH. This paper focuses on the use of alternative (non-animal) methods (both in vitro and in silico) for eye irritation testing. The manuscript reviews numerous in vitro tests and their possible collation into test batteries, in silico models and a refined in vivo method (the low volume eye test), before combining the use of all these methods into an integrated testing strategy. The aim of this strategy is a reduction in the number of animal tests which would need to be performed in the process of fulfilling the REACH system criteria; this would also lead to a lowering of the number of animals required in compliance with the REACH system requirements.

An integrated decision-tree testing strategy for eye irritation with respect to the requirements of the EU REACH legislation

This paper presents some results of a joint research project, sponsored by Defra and conducted by FRAME and Liverpool John Moores University, on the status of alternatives to animal testing with regard to the European Union REACH (Registration, Evaluation and Authorisation of Chemicals) system for the safety testing and risk assessment of chemicals. The project covered all the main toxicity endpoints associated with REACH. This paper focuses on the use of alternative (non-animal) methods (both in vitro and in silico) for eye irritation testing. The manuscript reviews numerous in vitro tests and their possible collation into test batteries, in silico models and a refined in vivo method (the low volume eye test), before combining the use of all these methods into an integrated testing strategy. The aim of this strategy is a reduction in the number animal tests which would need to be performed in the process of fulfilling the REACH system criteria; this would also lead to a lowering of the number of animals required in compliance with the REACH system requirements.

Phototoxicity and acute toxicity studies conducted by the FRAME Alternatives Laboratory: a brief review

FRAME and the University of Nottingham have been in association for the past 25 years. During this time, the research in the FRAME Alternatives Laboratory (FAL) at the University of Nottingham, which is partly funded by FRAME and also, more recently, by ECVAM, has involved participation in a number of international validation studies. Validation has become a pre-requisite for the regulatory acceptance of in vitro alternative test procedures, and a number of key lessons have been learned from these studies. The directors of validation studies need to ensure that standard operating procedures (SOPs) are fully complied with, and that the equipment used is certified to be of an acceptable standard. Database managers need to be able to check the original data, and to ensure adherence to procedures agreed before the study began. When the validation study is part of an integrated EU Framework Project, such as ACute-Tox, the Workpackage Leader must have the ability to understand and evaluate the data to be presented for inclusion in the study analysis, and to check that it complies with acceptance criteria. The potential to relate observed cellular biochemical changes to morphological endpoints also increases the level of understanding of the relevance and/or limitations of an assay. For example, exposure to a surfactant can induce the temporary loss of adhesion junctions between adjacent epithelial cells, resulting in the loss of barrier integrity and other effects on cell culture activity, which can potentially be restored over time. Unexpected results from the NRU phototoxicity assay with human keratinocytes instead of 3T3 cells, stimulated research into the ability of the in vitro assay, not only to identify phototoxins, but also to identify their possible mechanisms of action and mechanisms underlying the protective capacity within human primary keratinocytes in vitro. The protective effects of UV-filters can also be used to ascertain their effects on the photoactivation of drugs.

Alternative Methods for Eye and Skin Irritation Tests: An Overview

The evaluation of eye and skin irritation potential is essential to ensuring the safety of individuals in contact with a wide variety of substances designed for industrial, pharmaceutical or cosmetic use. The Draize rabbit eye and skin irritancy tests have been used for 60 years to attempt to predict the human ocular and dermal irritation of such products. The Draize test has been the standard for ocular and dermal safety assessments for decades. However, several aspects of the test have been criticised. These include: the subjectivity of the method; the overestimation of human responses; and the method's cruelty. The inadequacies of the Draize test have led to several laboratories over the last 20 years making efforts to develop in vitro assays to replace it. Protocols that use different types of cell cultures and other methods have been devised to study eye and skin irritation. Different commercial kits have also been developed to study eye and skin irritation, based on the action of chemicals on these tissues. This article presents a review of the main alternatives developed to replace the use of animals in the study of chemical irritation. Particular attention is paid to the reproducibility of each method.

The FRAME Research Programme under the direction of Dr Richard Clothier

The work of Dr Richard Clothier (Reader in Cellular Toxicology and Director of the FRAME Alternatives Laboratory in the University of Nottingham Medical School) in relation to the FRAME Research Programme, is reviewed. He made a very substantial contribution to FRAME's laboratory research work over the last 20 years, by publishing many research papers, mainly with respect to method development and the application of new replacement toxicity test methods, particularly those involving the use of human cells in tissue culture. In addition, he participated in a number of international validation studies that have facilitated the regulatory acceptance of certain new methods. Lastly, he has been closely involved in the logistical aspects of obtaining and maintaining external research funding for FRAME from industrial sponsors.

Use of the cytosensor microphysiometer to predict results of a 21-day cumulative irritation patch test in humans

The cytosensor microphysiometer (mu phi) was investigated as a rapid, relatively inexpensive test to predict performance of skin cleansing wipes on the human 21-day cumulative irritation patch test (21CIPT). It indirectly measures metabolic rate changes in L929 cells as a function of test article dose, by measuring the acidification rate in a low-buffer medium. The dose producing a 50% reduction in metabolic rate (MRD50), relative to the baseline rate, is used as a measure of toxicity. The acute toxicity of the mu phi assay can be compared to the chronic toxicity of the 21CIPT, which is based largely on the exposure of test agents to the epidermal cells, resulting in damage and penetration of the stratum corneum leading to cell toxicity. Two series of surfactant-based cleansing wipe products were tested via the mu phi assay and 21CIPT. The first series, consisting of 20 products, was used to determine a prediction model. The second series of 38 products consisted of routine product development formulas or marketed products. Comparing the results from both tests, samples with an MRD50 greater than 50 mg/ml provided a 21CIPT score consistent with a product that performs satisfactorily in the market. When the MRD50 was greater than 78 mg/ml, the 21CIPT score was usually zero. The mu phi may be more sensitive than the 21CIPT for ranking minimally irritating materials. The mu phi assay is useful as a screen for predicting the performance of a wet wipes formula on the 21CIPT, and concurrently reduces the use of animals for safety testing in a product development program for cleansing wipes.

In vitro alternatives to the use of animals in ocular toxicology testing

Chemical substances, including household products, industrial chemicals, and cosmetics, must be tested for ocular toxicity or irritancy so that the public can be assured of their safety or warned of dangers associated with their use. The in vivo Draize test is the standard method used to meet this requirement; however, this test is coming under increasing criticism on scientific and ethical grounds. This has led to the development of a large number of proposed in vitro tests, some of which are routinely used to screen chemicals in toxicology laboratories. This review addresses regulations governing ocular irritancy testing and the current status of the movement toward use of alternative methods. Such methods include the use of cultured cells, hen's eggs, isolated animal eyes and corneas, human corneal epithelial cell lines, and the recently developed in vitro corneal equivalent models. The protocols for these methods are outlined, and their endpoints are described with respect to prediction of in vivo responses. The tests are evaluated in the context of the outcomes of validation studies and acceptance by regulatory agencies. While several of these tests yield useful information concerning ocular irritancy, to date, no in vitro alternative test has been validated as a replacement for the Draize test. If the goal of replacing the in vivo test while protecting the public from chemical eye injury is to be achieved, further development and improvement of alternative tests, as well as establishment of a human ocular toxicity data base, are required.

Evaluation of eye and skin irritation of arginine-derivative surfactants using different in vitro endpoints as alternatives to the in vivo assays

Arginine-derivative surfactants constitute a novel class of surfactants, which can be regarded as an alternative to conventional surfactants. Prior to human exposure, it is necessary to assess their irritation potential. The classical in vivo evaluation of the irritancy potential via the Draize test has been extensively criticized. In that regard, a great number of in vitro alternatives have been developed. Erythrocytes were chosen as the target cells for eye irritation assessment and hemolysis and hemoglobin denaturation were selected as appropriate endpoints. For skin irritancy assessment, the keratinocyte cell line NCTC 2544 was used and different in vitro endpoints were measured: two cytotoxicity assays (NRU and MTT) and the synthesis of the proinflammatory cytokine IL-1alpha. The eye and skin Draize tests were also performed for comparative purposes. The results point out that, according to in vivo and in vitro assays, the new arginine-derivative surfactants have lower eye and skin irritation potential than the synthetic surfactant SDS. Furthermore, in vitro methods were also able to detect differences in irritancy among the new surfactants not noticeable by the Draize tests, indicating that in vitro methods can be more sensitive than the in vivo test, offering the opportunity to detect subtle differences in irritancy.

Comparison of an Animal Product Free Medium and Normal Growth Supplement on the Growth and Barrier Integrity of a Human Corneal Epithelial Cell Line

With the development of defined media for general and specific use with cell cultures, and concern over the use of human cells and over potential prion infections associated with growth factor extracts such as bovine pituitary extract, an animal product-free medium has become available. The basic keratinocyte defined medium can be used with a choice of animal product-containing or animal product-free supplements. Human corneal epithelia cell lines were cultured in the media with these two types of supplement, and compared in terms of their growth rates, their capacity to form tight barriers, and calcium regulation of the location of a junction-associated protein, zonula occludins-1 (ZO-1). The growth rates were not different in the two media, as long as the recommended coating was applied to the culture flask for the animal product-free medium. The barrier function was equally effective for confluent cultures seeded at the same densities. A calcium concentration of 100μM or above resulted in ZO-1 localisation at the cell membrane in either medium. Hence, cultures in the media are comparable, when the coating is employed. Further experiments are being conducted to establish the comparability of responses to chronic treatment with surfactants.