Evaluation of the EpiOcularTM Tissue Model as an Alternative to the Draize Eye Irritation Test

Development of Sensitive In Vitro Protocols for the Biocompatibility Testing of Medical Devices and Pharmaceuticals Intended for Contact with the Eyes: Acute Irritation and Phototoxicity Assessment

This study introduces a novel in vitro methodology that employs the 3-D reconstructed tissue model, EpiOcular, to assess the irritation and phototoxicity potential of medical devices and drugs in contact with the eye. Our study evaluated diverse test materials, including medical devices, ophthalmological solutions and an experimental drug (cemtirestat), for their potential to cause eye irritation and phototoxicity. The protocols used in this study with the EpiOcular tissue model were akin to those used in the ultra-mildness testing of cosmetic formulations, which is challenging to predict with standard in vivo rabbit tests. To design these protocols, we leveraged experience gained from the validation project on the EpiDerm skin irritation test for medical devices (ISO 10993-23:2021) and the OECD TG 498 method for photo-irritation testing. The predictions were based on the tissue viability and inflammatory response, as determined by IL-1α release. By developing and evaluating these protocols for medical devices, we aimed to expand the applicability domain of the tests referred to in ISO 10993-23. This will contribute to the standardisation and cost-effective safety evaluation of ophthalmic products, while reducing reliance on animal testing in this field. The findings obtained from the EpiOcular model in the photo-irritation test could support its implementation in the testing strategies outlined in OECD TG 498.

In Vitro and Ex Vivo Models for Assessing Drug Permeation across the Cornea

Drug permeation across the cornea remains a major challenge due to its unique and complex anatomy and physiology. Static barriers such as the different layers of the cornea, as well as dynamic aspects such as the constant renewal of the tear film and the presence of the mucin layer together with efflux pumps, all present unique challenges for effective ophthalmic drug delivery. To overcome some of the current ophthalmic drug limitations, the identification and testing of novel drug formulations such as liposomes, nanoemulsions, and nanoparticles began to be considered and widely explored. In the early stages of corneal drug development reliable in vitro and ex vivo alternatives, are required, to be in line with the principles of the 3Rs (Replacement, Reduction, and Refinement), with such methods being in addition faster and more ethical alternatives to in vivo studies. The ocular field remains limited to a handful of predictive models for ophthalmic drug permeation. In vitro cell culture models are increasingly used when it comes to transcorneal permeation studies. Ex vivo models using excised animal tissue such as porcine eyes are the model of choice to study corneal permeation and promising advancements have been reported over the years. Interspecies characteristics must be considered in detail when using such models. This review updates the current knowledge about in vitro and ex vivo corneal permeability models and evaluates their advantages and limitations.

Toxic External Exposure Leading to Ocular Surface Injury

The surface of the eye is directly exposed to the external environment, protected only by a thin tear film, and may therefore be damaged by contact with ambient particulate matter, liquids, aerosols, or vapors. In the workplace or home, the eye is subject to accidental or incidental exposure to cleaning products and pesticides. Organic matter may enter the eye and cause infection. Ocular surface damage can trigger a range of symptoms such as itch, discharge, hyperemia, photophobia, blurred vision, and foreign body sensation. Toxin exposure can be assessed clinically in multiple ways, including via measurement of tear production, slit-lamp examination, corneal staining, and conjunctival staining. At the cellular level, environmental toxins can cause oxidative damage, apoptosis of corneal and conjunctival cells, cell senescence, and impaired motility. Outcomes range from transient and reversible with complete healing to severe and sight-compromising structural changes. Classically, evaluation of tolerance and safety was carried out using live animal testing; however, new in vitro and computer-based, in silico modes are superseding the gold standard Draize test. This review examines how environmental features such as pollutants, temperature, and seasonality affect the ocular surface. Chemical burns to the eye are considered, and approaches to protect the ocular surface are detailed.

Development of an oral mucosal irritation test using a three-dimensional human buccal oral mucosal model

The oral mucosa can become irritated by oral care products and lip cosmetics. Therefore, it is important to determine the irritation potential of their ingredients and products during safety evaluations. We developed a method for oral mucosal irritation test using EpiOral, which is a three-dimensional cultured model. Exposure of sodium lauryl sulphate (SLS) to EpiOral showed a dose-dependent decrease in cell viability. Under 120 min exposure conditions, SLS irritation was detected when 60% cell viability was set as a criterion. Evaluation of the irritancy of SLS and four other raw materials used in oral products at three laboratories under the above conditions confirmed good transferability of the test. Focused on the similarity of the oral and eye mucous, 32 chemicals categorised by the UN-GHS eye-irritation classification were evaluated to ensure the reliability of our criteria at these laboratories. The concordance rate between the UN-GHS classification and our test results was 100% for irritants and 60% for non-irritants. The good intra-laboratory reproducibility of our test was confirmed from the evaluation results of negative and positive controls, and the good inter-laboratory reproducibility was confirmed from the results of 32 chemicals. These findings showed that oral mucosal irritation can be evaluated using EpiOral.

Tissue Engineered Mini-Cornea Model for Eye Irritation Test

BACKGROUND

Eye irritation tests with animals have been conducted for a long time. However, the subjective decision to irritation, the anatomic/physiologic difference between species and humans, and ethical issues are crucial problems. Various research groups have paid attention to alternative testing methods. In these senses, we fabricated in vitro mini-cornea models with immortalized human corneal epithelial cells (iHCECs) and keratocytes (iHCKs) and used them for irritation tests. This study hypothesized that our mini-cornea model could present different viability tendencies according to test chemicals with different irritancy levels.

METHODS

Cells used in this study were characterized with cornea-specific markers by immunocytochemistry and western blot. To make a three-dimensional hemisphere construct like cornea stroma, we cultured iHCKs under modified culture conditions verified by matrix formation and total collagen content. iHCECs were seeded on the construct and cultured at an air-liquid interface. The model was treated with 2-phenoxyethanol, triton X-100, sodium lauryl sulfate, and benzalkonium chloride.

RESULTS

iHCECs and iHCKs presented their specific cell markers. In modifying the culture condition, the group treating ascorbic acid (200 µg/ml) presented an intact cellular matrix and included the highest collagen content; thus, we used this condition to fabricate the mini-cornea model. The model shows hemisphere shape and homogenous cell distributions in histological analysis. We observed different sensitivity tendencies by types of chemicals, and the model's viability significantly decreased when the chemical concentration increased.

CONCLUSION

In this study, we performed and observed irritation tests using a tissue-engineered mini-cornea model and considered to apply as an alternative approach for animal tests.

In-house performance assessment of 3D QobuR-Reconstructed Human Cornea-Like Epithelium (RhCE) for the evaluation of eye hazard

To replace the Draize eye irritation test (OECD Test Guideline 404), several test methods based on reconstructed cornea-like epithelium (RhCE) have been developed and adopted in the OECD TG 492. The objective of this study was to stablish the experimental procedures and evaluate the performance assessment of QobuR-RhCE, an in-house RhCE model to be used for the evaluation of eye hazard. We define the essential structural, functional and procedural elements of the test method components to help assuring that the proposed test method is based on the same concepts as the validated reference methods. Performance assessment was evaluated in accordance with the revised performance standards for the assessment of proposed similar or modified in vitro reconstructed human cornea-like epithelium and the minimum list of reference chemicals was evaluated. As result, the proposed method scored 93.3% sensibility, 60% specificity, 76.7% accuracy and 96.7% within-laboratory reproducibility (WLR), providing a similar performance in comparison to the validated reference methods. Additionally, we describe a secondary endpoint based on Transepithelial Electrical Resistance (TEER) that could be of use to better discriminate between irritants and non-irritants. Taken together the results indicate that the QobuR-RhCE test method is an accurate screening tool that can be used as a standalone alternative to evaluate ocular irritation.

Approaches to Safety Evaluation of Baby Wipes

Disposable baby wipes manufactured by Procter & Gamble, soft sheets bearing lotion that is balanced to maintain natural skin pH, are convenient for cleaning the diaper area and a quick cleanup on baby’s face and hands.

Mucus-producing 3D cell culture models

In vitro cell-based models have been used for a long time since they are normally easily obtained and have an advantageous cost-benefit. Besides, they can serve a variety of ends, from studying drug absorption and metabolism to disease modeling. However, some in vitro models are too simplistic, not accurately representing the living tissues. It has been shown, mainly in the last years, that fully mimicking a tissue composition and architecture can be paramount for cellular behavior and, consequently, for the outcomes of the studies using such models. Because of this, 3D in vitro cell models have been gaining much attention, since they are able to better replicate the in vivo environment. In this review we focus on 3D models that contain mucus-producing cells, as mucus can play a pivotal role in drug absorption. Being frequently overlooked, this viscous fluid can have an impact on drug delivery. Thus, the aim of this review is to understand to which extent can mucus affect mucosal drug delivery and to provide a state-of-the-art report on the existing 3D cell-based mucus models.

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.

Three-Dimensional Human Cell Culture Models to Study the Pathophysiology of the Anterior Eye

In recent decades, the establishment of complex three-dimensional (3D) models of tissues has allowed researchers to perform high-quality studies and to not only advance knowledge of the physiology of these tissues but also mimic pathological conditions to test novel therapeutic strategies. The main advantage of 3D models is that they recapitulate the spatial architecture of tissues and thereby provide more physiologically relevant information. The eye is an extremely complex organ that comprises a large variety of highly heterogeneous tissues that are divided into two asymmetrical portions: the anterior and posterior segments. The anterior segment consists of the cornea, conjunctiva, iris, ciliary body, sclera, aqueous humor, and the lens. Different diseases in these tissues can have devastating effects. To study these pathologies and develop new treatments, the use of cell culture models is instrumental, and the better the model, the more relevant the results. Thus, the development of sophisticated 3D models of ocular tissues is a significant challenge with enormous potential. In this review, we present a comprehensive overview of the latest advances in the development of 3D in vitro models of the anterior segment of the eye, with a special focus on those that use human primary cells.

Discovery of Ezrin Expression as a Potential Biomarker for Chemically Induced Ocular Irritation Using Human Corneal Epithelium Cell Line and a Reconstructed Human Cornea-like Epithelium Model

Numerous studies have attempted to develop a new in vitro eye irritation test (EIT). To obtain more reliable results from EIT, potential new biomarkers that reflect eye irritation by chemicals must be identified. We investigated candidate biomarkers for eye irritation, using a proteomics approach. Sodium lauryl sulfate (SLS) or benzalkonium chloride (BAC) was applied on a reconstructed human cornea-like epithelium model, MCTT HCE, and corneal protein expression was examined by two-dimensional gel electrophoresis. We found that ezrin (EZR) was significantly upregulated by SLS or BAC. In addition, upregulation of EZR in immortalized human corneal cells treated with SLS or BAC was confirmed by quantitative reverse transcription-PCR and western blot analysis. Furthermore, other well-known eye irritants such as cetylpyridinium bromide, Triton X-100, cyclohexanol, ethanol, 2-methyl-1-pentanol, and sodium hydroxide significantly increased EZR expression in immortalized human corneal cells. Induction of EZR promoter activity in irritant-treated human corneal cells was confirmed by a luciferase gene reporter assay. In conclusion, EZR expression may be a potential biomarker for detecting eye irritation, which may substantially improve the performance of in vitro EIT.

CON4EI: CONsortium for in vitro Eye Irritation testing strategy - EpiOcular™ time-to-toxicity (EpiOcular ET-50) protocols for hazard identification and labelling of eye irritating chemicals

Assessment of acute eye irritation potential is part of the international regulatory requirements for testing of chemicals. The objective of the CON4EI (CONsortium for in vitro Eye Irritation testing strategy) project was to develop tiered testing strategies for eye irritation assessment for all drivers of classification. A set of 80 reference chemicals (38 liquids and 42 solids) was tested with eight different alternative methods. Here, the results obtained with reconstructed human cornea-like epithelium (RhCE) EpiOcular™ in the EpiOcular time-to-toxicity Tests (Neat and Dilution ET-50 protocols) are presented. The primary aim of this study was to evaluate whether test methods can discriminate chemicals not requiring classification for serious eye damage/eye irritancy (No Category) from chemicals requiring classification and labelling for Category 1 and Category 2. In addition, the predictive capacity in terms of in vivo drivers of classification was investigated. The chemicals were tested in two independent runs by MatTek In Vitro Life Science Laboratories. Results of this study demonstrate very high specificity of both test protocols. With the existing prediction models described in the SOPs, the specificity of the Neat and Dilution method was 87% and 100%, respectively. The Dilution method was able to correctly predicting 66% of GHS Cat 2 chemicals, however, prediction of GHS Cat 1 chemicals was only 47%-55% using the current protocols. In order to achieve optimal prediction for all three classes, a testing strategy was developed which combines the most predictive time-points of both protocols and for tests liquids and solids separately. Using this new testing strategy, the sensitivity for predicting GHS Cat 1 and GHS Cat 2 chemicals was 73% and 64%, respectively and the very high specificity of 97% was maintained. None of the Cat 1 chemicals was underpredicted as GHS No Category. Further combination of the EpiOcular time-to-toxicity protocols with other validated in vitro systems evaluated in this project, should enable significant reduction and even possible replacement of the animal tests for the final assessment of the irritation potential in all of the GHS classes.

Local tolerance testing under REACH: Accepted non-animal methods are not on equal footing with animal tests

In general, no single non-animal method can cover the complexity of any given animal test. Therefore, fixed sets of in vitro (and in chemico) methods have been combined into testing strategies for skin and eye irritation and skin sensitisation testing, with pre-defined prediction models for substance classification. Many of these methods have been adopted as OECD test guidelines. Various testing strategies have been successfully validated in extensive in-house and inter-laboratory studies, but they have not yet received formal acceptance for substance classification. Therefore, under the European REACH Regulation, data from testing strategies can, in general, only be used in so-called weight-of-evidence approaches. While animal testing data generated under the specific REACH information requirements are per se sufficient, the sufficiency of weight-of-evidence approaches can be questioned under the REACH system, and further animal testing can be required. This constitutes an imbalance between the regulatory acceptance of data from approved non-animal methods and animal tests that is not justified on scientific grounds. To ensure that testing strategies for local tolerance testing truly serve to replace animal testing for the REACH registration 2018 deadline (when the majority of existing chemicals have to be registered), clarity on their regulatory acceptance as complete replacements is urgently required.

In Vitro Cell Models for Ophthalmic Drug Development Applications

Tissue engineering is a rapidly expanding field that aims to establish feasible techniques to fabricate biologically equivalent replacements for diseased and damaged tissues/organs. Emerging from this prospect is the development of in vitro representations of organs for drug toxicity assessment. Due to the ever-increasing interest in ocular drug delivery as a route for administration as well as the rise of new ophthalmic therapeutics, there is a demand for physiologically accurate in vitro models of the eye to assess drug delivery and safety of new ocular medicines. This review summarizes current existing ocular models and highlights the important factors and limitations that need to be considered during their use.

Evaluation of Eye Irritation Potential of Solid Substance with New 3D Reconstructed Human Cornea Model, MCTT HCE(TM)

The eye irritation potential of drug candidates or pharmaceutical ingredients should be evaluated if there is a possibility of ocular exposure. Traditionally, the ocular irritation has been evaluated by the rabbit Draize test. However, rabbit eyes are more sensitive to irritants than human eyes, therefore substantial level of false positives are unavoidable. To resolve this species difference, several three-dimensional human corneal epithelial (HCE) models have been developed as alternative eye irritation test methods. Recently, we introduced a new HCE model, MCTT HCE^TM which is reconstructed with non-transformed human corneal cells from limbal tissues. Here, we examined if MCTT HCE^TM can be employed to evaluate eye irritation potential of solid substances. Through optimization of washing method and exposure time, treatment time was established as 10 min and washing procedure was set up as 4 times of washing with 10 mL of PBS and shaking in 30 mL of PBS in a beaker. With the established eye irritation test protocol, 11 solid substances (5 non-irritants, 6 irritants) were evaluated which demonstrated an excellent predictive capacity (100% accuracy, 100% specificity and 100% sensitivity). We also compared the performance of our test method with rabbit Draize test results and in vitro cytotoxicity test with 2D human corneal epithelial cell lines.

Identification of cornifelin and early growth response-1 gene as novel biomarkers for in vitro eye irritation using a 3D reconstructed human cornea model MCTT HCE™

Evaluation of the eye irritation is essential in the development of new cosmetic products. Draize rabbit eye irritation test has been widely used in which chemicals are directly applied to rabbit eye, and the symptoms and signs of eyes are scored. However, due to the invasive procedure, it causes substantial pain and discomfort to animals. Recently, we reported in vitro eye irritation test method using a 3D human corneal epithelial model (MCTT HCE™) which is reconstructed from remaining human tissues after a corneal transplantation. This model exhibited an excellent predictive capacity for 25 reference chemicals (sensitivity 100%, specificity 77% and accuracy 88% vs. GHS). To improve the test performance, we explored new biomarkers for the eye irritation through transcriptomic approach. Three surfactants were selected as model eye irritants that include sodium lauryl sulfate, benzalkonium chloride and triton X-100. After test chemicals were treated, we investigated differentially expressed genes through a whole-gene microarray (Affymetrix GeneChip(®) Human Gene 2.0 ST Array, 48,000 probes). As a result, we identified that mRNAs of cornifelin (CNFN), a constituent of the insoluble cornified cell envelope of stratified squamous epithelia, and early growth response-1 (EGR1), a nuclear transcriptional regulator, were significantly up-regulated by all three irritants. Up-regulation of CNFN and EGR1 was further confirmed by Q-RT-PCR, and immunohistochemistry revealed increased level of CNFN in irritant-treated tissues, supporting the relevance of CNFN and EGR1 as new biomarkers for eye irritation.

Effects of ozone nano-bubble water on periodontopathic bacteria and oral cells - in vitro studies

The aims of the present study were to evaluate the bactericidal activity of a new antiseptic agent, ozone nano-bubble water (NBW3), against periodontopathogenic bacteria and to assess the cytotoxicity of NBW3 against human oral cells. The bactericidal activities of NBW3 against representative periodontopathogenic bacteria, Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) were evaluated using in vitro time-kill assays. The cytotoxicity of NBW3 was evaluated using three-dimensional human buccal and gingival tissue models. The numbers of colony forming units (CFUs)/mL of P. gingivalis and A. actinomycetemcomitans exposed to NBW3 dropped to below the lower limit of detection (<10 CFUs mL^-1) after only 0.5 min of exposure. There were only minor decreases in the viability of oral tissue cells after 24 h of exposure to NBW3. These results suggest that NBW3 possesses potent bactericidal activity against representative periodontopathogenic bacteria and is not cytotoxic to cells of human oral tissues. The use of NBW3 as an adjunct to periodontal therapy would be promising.

Safety Assessment of Diethanolamides as Used in Cosmetics

Cocamide diethanolamine (DEA) and some of the other diethanolamides are mainly used as surfactant foam boosters or viscosity increasing agents in cosmetics, although a few are reported to be used as hair and skin conditioning agents, surfactant-cleansing or surfactant-emulsifying agents, or as an opacifying agent. The Cosmetic Ingredient Review (CIR) Expert Panel considered new data and information from previous CIR reports to assess the concerns about the potential for amidases in human skin to convert these diethanolamides into DEA and the corresponding fatty acids. The Expert Panel concluded that these diethanolamides are safe as used when formulated to be nonirritating and when the levels of free DEA in the diethanolamides do not exceed those considered safe by the Panel. The Panel also recommended that these ingredients not be used in cosmetic products in which N-nitroso compounds can be formed.

Ocular toxicity of authentic lunar dust

Background

Dust exposure is a well-known occupational hazard for terrestrial workers and astronauts alike and will continue to be a concern as humankind pursues exploration and habitation of objects beyond Earth. Humankind’s limited exploration experience with the Apollo Program indicates that exposure to dust will be unavoidable. Therefore, NASA must assess potential toxicity and recommend appropriate mitigation measures to ensure that explorers are adequately protected. Visual acuity is critical during exploration activities and operations aboard spacecraft. Therefore, the present research was performed to ascertain the ocular toxicity of authentic lunar dust.

Methods

Small (mean particle diameter = 2.9 ± 1.0 μm), reactive lunar dust particles were produced by grinding bulk dust under ultrapure nitrogen conditions. Chemical reactivity and cytotoxicity testing were performed using the commercially available EpiOcular^TM assay. Subsequent in vivo Draize testing utilized a larger size fraction of unground lunar dust that is more relevant to ocular exposures (particles <120 μm; median particle diameter = 50.9 ± 19.8 μm).

Results

In vitro testing indicated minimal irritancy potential based on the time required to reduce cell viability by 50% (ET50). Follow-up testing using the Draize standard protocol confirmed that the lunar dust was minimally irritating. Minor irritation of the upper eyelids was noted at the 1-hour observation point, but these effects resolved within 24 hours. In addition, no corneal scratching was observed using fluorescein stain.

Conclusions

Low-titanium mare lunar dust is minimally irritating to the eyes and is considered a nuisance dust for ocular exposure. No special precautions are recommended to protect against ocular exposures, but fully shielded goggles may be used if dust becomes a nuisance.

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 2009, the Bovine Corneal Opacity and Permeability (BCOP) test was accepted by the regulatory bodies for the identification of corrosive and severe ocular irritants (Global Harmonised System [GHS] Category 1). However, no in vitro test is currently accepted for the differentiation of ocular irritants (GHS Category 2) and non-irritants (GHS No Category). Human reconstructed tissue models have been suggested for incorporation into a tiered testing strategy to ultimately replace the Draize rabbit eye irritation test (OECD TG 405). The purpose of this study was to evaluate whether the EpiOcular(TM) reconstructed cornea-like tissue model and the COLIPA pre-validated EpiOcular Eye Irritation Test (EpiOcular-EIT) could be used as suitable components of this testing strategy. The in-house validation of the EpiOcular-EIT was performed by using 60 test substances, including a broad variety of chemicals and formulations for which in vivo data (from the Draize rabbit eye irritation test) were available. The test substances fell into the following categories: 18 severe irritants/corrosives (Category 1), 21 irritants (Category 2), and 21 non-irritants (No Category). Test substances that decreased tissue viability to ≤ 60% (compared to the negative control tissue) were considered to be eye irritants (Category 1/2). Test substances resulting in tissue viability of > 60% were considered to be non-irritants (No Category). For the assessed dataset and the classification cut-off of 60% viability, the EpiOcular-EIT provided 98% and 84% sensitivity, 64% and 90% specificity, and 85% and 86% overall accuracy for the literature reference and BASF proprietary substances, respectively. Applying a 50% tissue viability cut-off to distinguish between irritants and non-irritants resulted in 93% and 82% sensitivity, 68% and 100% specificity, and 84% and 88% accuracy for the literature reference and BASF proprietary substances, respectively. Further, in the EpiOcular-EIT (60% cut-off), 100% of severely irritating substances under-predicted by the BCOP assay were classified as Category 1/2. The results obtained in this study, based on 60 test substances, indicate that the EpiOcular-EIT and the BCOP assay can be combined in a testing strategy to identify strong/severe eye irritants (Category 1), moderate and mild eye irritants (Category 2), and non-irritants (No Category) in routine testing. In particular, when the bottom-up strategy with the 60% viability cut-off was employed, none of the severely irritating substances (Category 1) were under-predicted to be non-irritant. Sensitivity for Category 1/2 substances was 100% for literature reference substances and 89% for BASF SE proprietary substances.

Final Report on the Safety Assessment of Sodium Cetearyl Sulfate and Related Alkyl Sulfates as Used in Cosmetics

Sodium cetearyl sulfate is the sodium salt of a mixture of cetyl and stearyl sulfate. The other ingredients in this safety assessment are also alkyl salts, including ammonium coco-sulfate, ammonium myristyl sulfate, magnesium coco-sulfate, sodium cetyl sulfate, sodium coco/hydrogenated tallow sulfate, sodium coco-sulfate, sodium decyl sulfate, sodium ethylhexyl sulfate, sodium myristyl sulfate, sodium oleyl sulfate, sodium stearyl sulfate, sodium tallow sulfate, sodium tridecyl sulfate, and zinc coco-sulfate. These ingredients are surfactants used at concentrations from 0.1% to 29%, primarily in soaps and shampoos. Many of these ingredients are not in current use. The Cosmetic Ingredient Review (CIR) Expert Panel previously completed a safety assessment of sodium and ammonium lauryl sulfate. The data available for sodium lauryl sulfate and ammonium lauryl sulfate provide sufficient basis for concluding that sodium cetearyl sulfate and related alkyl sulfates are safe in the practices of use and concentration described in the safety assessment.

The MatTek story - how the three Rs principles led to 3-D tissue success!

MatTek Corporation has been working diligently for over 15 years to replace traditional animal-based toxicity and efficacy tests with alternative test methods based on human-cell derived, three-dimensional (3-D) tissue models. First discussed in detail by W.M.S. Russell and R.L. Burch 50 years ago in their book, The Principles of Humane Experimental Technique, and now fully integrated into forward-looking publications such as Toxicity Testing in the 21st Century: A Vision and a Strategy, the concept of replacing animals in test procedures with human cells and/or human cell-derived in vitro 3-D tissues is being embraced by the world's research scientists and toxicologists at an ever-increasing rate. 3-D in vitro models are being utilised not only for humanitarian reasons, but also because human 3-D tissues, in particular, produce more-physiologically relevant scientific data. Early on in MatTek's efforts to develop this alternative test method, senior management sought the assistance of experts within the in vitro testing and animal rights communities, to help define the specific in vitro human 3-D tissue products needed and navigate the regulatory landscape, especially in Europe where the replacement of animal-based testing with non-animal alternative test methods was well underway. MatTek was fortunate to receive that expert assistance on both fronts from Professor Michael Balls, who at that time was the newly-elected first director of ECVAM. In 1997, with the guidance and support of Professor Balls and others in the animal rights community, MatTek began the effort to validate several of its human 3-D tissue-based alternative test methods. Today, two MatTek human cell-derived 3-D tissue-based test methods are validated as full replacements for existing animal-based tests, with more tests in the validation pipeline. In addition, MatTek in vitro tissue models are in use worldwide by chemical, pharmaceutical and consumer product companies, as evidenced by citations in hundreds of patents and scientific articles from these industries. This article concludes with MatTek's thoughts on the direction that human 3-D tissue-based in vitro testing will take in the future.

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.

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.

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.

Development of a hemicornea from human primary cell cultures for pharmacotoxicology testing

We report the reconstruction and characterization of a hemicornea (epithelialized stroma), using primary human cells, for use in research and as an alternative to the use of animals in pharmacotoxicology testing. To create a stromal equivalent, keratocytes from human corneas were cultured in collagen-glycosaminoglycan-chitosan foams. Limbal stem cell-derived epithelial cells were seeded on top of these, giving rise to hemi-corneas. The epithelium appeared morphologically similar to its physiological counterpart, as shown by the basal cell expression of p63 isoforms including, in some cases, the stem cell marker p63DeltaNalpha, and the expression of keratin 3 and 14-3-3sigma in the upper cell layers. In addition, the cuboidal basal epithelial cells were anchored to a basement membrane containing collagen IV, laminin 5, and hemidesmosomes. In the stromal part, the keratocytes colonized the porous scaffold, formed a network of interconnecting cells, and synthesized an ultrastructurally organized extracellular matrix (ECM) containing collagen types I, V, and VI. Electron microscopy showed the newly synthesized collagen fibrils to have characteristic periodic striations, with diameters and interfibril spacings similar to those found in natural corneas. Compared to existing models for corneal pharmacotoxicology testing, this new model more closely approaches physiological conditions by including the inducing effects of mesenchyme and cell-matrix interactions on epithelial cell morphogenesis.

Organotypic human oral tissue models for toxicological studies

Three-dimensional models of the human oral epithelia have been developed to test the irritation of oral-care products and to provide systems to study the pathology of the oral cavity. The in vitro tissue models, cultured using normal oral epithelial cells and serum free medium, adopt a buccal or gingival phenotype. The buccal tissue (designated ORL-200) is 8-12 cell layers thick and non-cornified; the gingival tissue (designated GIN-100) is 9-13 layers thick and cornified at the apical surface. The tissues express cytokeratins 13 and 14 similar to their corresponding native oral tissues. The MTT viability assay was used to assess inter-lot and intra-lot reproducibility. The MTT average intra-lot coefficient of variation (CV) was less than 10% for both tissues and the time required to reduce tissue viability by 50% (ET-50) following application of 1% Triton-X 100 averaged 1.02+/-0.33 h (n=26) and 7.97+/-0.80 h (n=14) for the buccal and gingival tissues, respectively. The utility of the buccal tissue for irritation studies was examined by testing prototype dentifrice formulations and commercially available products including mouthwashes, toothpastes, and oral cleansers. Use of the MTT ET-50 assay and cytokine release clearly differentiated between the formulations and the oral care products. In conclusion, the oral tissue models represent highly reproducible, non-animal means to screen the irritation potential of newly developed oral care products and should be useful to study the innate immunity, biology, and pathology of the oral mucosa.

The Interaction and Compatibility Between a Soft Contact Lens and an Ophthalmic Drug

PURPOSE

To investigate the interaction and compatibility between a soft contact lens (SCL) and an ophthalmic drug.

METHODS

Samples were prepared with the nonionic SCL (groups I and II), the anionic SCL (group IV), and the zwitter ionic SCL (group IV). Chlorpheniramine maleate and sodium cromoglycate were used to measure the drug uptake into the SCL.

RESULTS

The results showed the largest drug uptake into the anionic SCL accompanied with dimensional changes and lower drug uptakes into the nonionic and the zwitter ionic SCL with dimensional stability. The cell permeability of the substances when instilled in the eye over the SCL was also measured. The zwitter ionic SCL allowed cell permeability comparable to that by oral administration.

CONCLUSIONS

These results indicated the possibility for the zwitter ionic SCL as a lens to be worn concomitantly with ophthalmic drug instillation.

Reconstituted human corneal epithelium: a new alternative to the Draize eye test for the assessment of the eye irritation potential of chemicals and cosmetic products

The aim of this study was to evaluate the interest of a new three-dimensional epithelial model cultivated from human corneal cells to replace animal testing in the assessment of eye tolerance. To this end, 65 formulated cosmetic products and 36 chemicals were tested by means of this in vitro model using a simplified toxicokinetic approach. The chemicals were selected from the ECETOC data bank and the EC/HO International validation study list. Very satisfactory results were obtained in terms of concordance with the Draize test data for the formulated cosmetic products. Moreover, the response of the corneal model appeared predictive of human ocular response clinically observed by ophthalmologists. The in vitro scores for the chemicals tested strongly correlated with their respective scores in vivo. For all the compounds tested, the response of the corneal model to irritants was similar regardless of their chemical structure, suggesting a good robustness of the prediction model proposed. We concluded that this new three-dimensional epithelial model, developed from human corneal cells, could be promising for the prediction of eye irritation induced by chemicals and complex formulated products, and that these two types of materials should be tested using a similar protocol. A simple shortening of the exposure period was required for the chemicals assumed to be more aggressively irritant to the epithelial tissues than the cosmetic formulae.

Evaluation of the health aspects of methyl paraben: a review of the published literature

Methyl paraben (CAS No. 99-76-3) is a methyl ester of p-hydroxybenzoic acid. It is a stable, non-volatile compound used as an antimicrobial preservative in foods, drugs and cosmetics for over 50 years. Methyl paraben is readily and completely absorbed through the skin and from the gastrointestinal tract. It is hydrolyzed to p-hydroxybenzoic acid, conjugated, and the conjugates are rapidly excreted in the urine. There is no evidence of accumulation. Acute toxicity studies in animals indicate that methyl paraben is practically non-toxic by both oral and parenteral routes. In a population with normal skin, methyl paraben is practically non-irritating and non-sensitizing. In chronic administration studies, no-observed-effect levels (NOEL) as high as 1050 mg/kg have been reported and a no-observed-adverse-effect level (NOAEL) in the rat of 5700 mg/kg is posited. Methyl paraben is not carcinogenic or mutagenic. It is not teratogenic or embryotoxic and is negative in the uterotrophic assay. The mechanism of cytotoxic action of parabens may be linked to mitochondrial failure dependent on induction of membrane permeability transition accompanied by the mitochondrial depolarization and depletion of cellular ATP through uncoupling of oxidative phosphorylation. Parabens are reported to cause contact dermatitis reactions in some individuals on cutaneous exposure. Parabens have been implicated in numerous cases of contact sensitivity associated with cutaneous exposure; however, the mechanism of this sensitivity is unknown. Sensitization has occurred when medications containing parabens have been applied to damaged or broken skin. Allergic reactions to ingested parabens have been reported, although rigorous evidence of the allergenicity of ingested paraben is lacking.

Comparative evaluation of five in vitro tests for assessing the eye irritation potential of hair-care products

This study compared five methods, the isolated rabbit eye (IRE), bovine corneal opacity and permeability (BCOP), EpiOcular, fluorescein leakage (FL) and neutral red release (NRR) assays, for predicting the eye irritation potential of hair-care formulations. Ten shampoo and seven conditioner formulations of known ocular irritation potential were tested. Each group included a market-acceptable formulation as a comparative benchmark. Predictions of ocular irritation were made by using classification models (IRE, BCOP and EpiOcular assays) or by direct comparison with benchmarks (IRE, EpiOcular, FL and NRR assays). The BCOP assay was less sensitive than the IRE test in discriminating between formulations of different irritation potentials, and did not perform as well as the other assays in identifying mild formulations. All of the assays appeared to be better at discriminating correctly between the shampoos than between the conditioners. The EpiOcular assay showed the closest concordance between the in vivo results and the in vitro data from cell-based assays (particularly for shampoos). The FL assay also showed a high concordance (particularly for conditioners). There was a tendency for these in vitro assays to over-predict eye irritation potential, but there was no under-prediction and they were particularly successful at identifying mild formulations. The NRR assay was less predictive with both shampoos and conditioners. The results from this comparative evaluation fully support the continued use of the IRE test as a suitable alternative to in vivo eye irritation testing in rabbits, although it also over-predicted the irritancies of several of the formulations. The value of using concurrent benchmarks (reference standards), appropriate to the materials being tested, in interpreting the data obtained from in vitro tests, was also demonstrated. Overall, the results indicate that further comparisons of the IRE, EpiOcular and FL assays are warranted using much larger numbers of test materials.