In Vitro Toxicology Testing
MatTek’s EpiDerm™ in vitro human skin model and EpiOcular™ in vitro human corneal model have become increasingly important as replacements for or as complements to traditional animal-based toxicology testing in the cosmetics, personal care, household products, and pharmaceutical industries.
One EpiDerm assay is now formally validated as an alternative method in both the European Union (EU) and the United States, while several others continue through the validation process as defined by regulators in Europe (ECVAM) and the United States (ICCVAM).
MatTek’s EpiAirway™ human cell-derived in vitro tracheal/bronchial model is ideally suited for inhalation toxicology studies. EpiAirway was also recently used by nanotoxicology researchers examining the translocation properties of nano-sized particles in the human respiratory tract.
MatTek’s recently developed EpiOral™ human cell-derived in vitro buccal (inner cheek) model and EpiVaginal™ human cell-derived in vitro ecto-cervical vaginal model are also well-suited for cyto-toxicity studies.
Contact MatTek to receive a list of Contract Testing Labs (CTL's) using our in vitro tissue models in their toxicology assays.
EpiDerm In Vitro Toxicology Tests
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EpiDerm™ Skin Model
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EpiDerm consists of normal human epidermal keratinocytes that have been cultured in chemically defined medium on a permeable polycarbonate membrane to produce a stratified, highly differentiated, organotypic tissue model of the human epidermis. The EpiDerm tissue consists of metabolically and mitotically active cells which are organized into basal, spinous, and granular layers along a multi-layered stratum corneum. The tissue construct has an air-liquid interface and exhibits in vivo-like morphological and growth characteristics that allows test materials to be directly applied to the surface of the tissue. EpiDerm tissue approximates the barrier of normal human skin, and the topical mode of application of the test material mimics the route of human exposure. Method endpoint is the MTT ET-50 Tissue Viability Assay.1
EpiDerm (Model EPI-200) has been used successfully as an in vitro alternative in a number of toxicology tests, most notably Dermal Corrosion, Skin Irritation, and Dermal Phototoxicity. More detail is given for each of these EpiDerm toxicological test procedures below, and a detailed protocol is available for each test method by completing the MatTek Online Information Request Form.
Dermal Corrosion:
Dermal Corrosion is generally defined as "the production of scarring usually as result of corrosive tissue destruction (necrosis) following the application of a substance", and is irreversible. The EpiDerm dermal corrosion protocol is based on the experience that corrosive chemicals are cytotoxic after a short term exposure to the stratum corneum (outer layer) of the epidermis. The assay is designed to predict and classify the skin corrosivity potential of a chemical.
The EpiDerm (Model EPI-200) dermal corrosion test method is now a validated alternative test procedure to the Draize Rabbit Skin Corrosion Test in both the European Union (EU) and the United States.
More detailed Dermal Corrosion information is available by clicking here.
Click here to review Dermal Corrosion technical references on the MatTek Web site.
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Skin Irritation Potential:
Skin Irritation Potential (cutaneous toxicity) is defined as the reversible inflammatory response of the epidermis to a topically applied substance. A typical application is testing the skin irritation potential of new cosmetic product formulations while in development to identify chemicals that might induce adverse skin reactions. The traditional assay method is the Draize Rabbit Skin Irritation Test.
Although EpiDerm (Model EPI-200) is not yet a validated alternative test method for the determination of skin irritation potential, there has been significant recent progress, particularly in Europe, to confirm EpiDerm as a validated alternative test method. This progress in summarized in the following MatTek report, “Assessment of Human Skin Irritation: Validation of In Vitro Models”. Please click here to read the report’s Executive Summary and to receive a copy of the full 11 page report.
More detailed Skin Irritation information is available by clicking here.
Click here to review Skin Irritation technical references on the MatTek Web site.
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Dermal Phototoxicity:
Dermal Phototoxicity (photoirritation) is defined as “an acute reaction which can be caused by a single treatment with a chemical and UV or visible radiation. In vivo, the reaction can be evoked in all subjects provided that the concentration of chemical and dose of light are appropriate. ‘Acute’ includes both immediate and delayed (e.g. after 48 hours) reactions. The term photoirritation is used to describe phototoxic reactions in skin which are produced with topically applied substances following exposure to light.” (from ECVAM Workshop 42) A typical application is testing the phototoxicity of new sunscreen product formulations while in development to identify chemicals that might induce adverse skin reactions.
Historically phototoxicity testing has been performed on animal models. The species used most frequently are mice, guinea pigs, and rabbits. Apart from the humanitarian concerns these tests cause, there are a number of factors that affect successful testing in these models, including: species, strain, exposure site (eyes, skin), hair removal, concentration of test substance (per unit area), solvent or vehicle, administration route, time interval between administration and irradiation, light source, UV dosimetry, assessment of reactions, negative control (solvent and light), irritation control (test compound only), and positive control (known phototoxin and light). (Source: ECVAM Workshop 42)
It has been shown (in a joint EU/COLIPA validation project) that the phototoxic potential of chemicals can be correctly predicted by using cell culture monolayers in a specially designed cytotoxicity assay, the 3T3-NRU-Phototoxicity Test. Because the phototoxic potential of a chemical predicted using a cellular system may not be relevant when topically applied to the skin at low concentrations (e.g. in a formulation) there is a need for adjunct tests that allow for the assessment of safe usage concentrations on a dose per area basis before testing them in humans. Reconstituted skin models and epidermis models (EpiDerm Model EPI-200) have shown to be able to predict both, photoirritancy, as well as the photoprotective action of sunscreens. In addition, skin models can handle formulations (e.g. emulsions, suspensions) which the 3T3 test cannot handle. Therefore, in a testing strategy that is based purely on in vitro tests, there is a need to combine the basic 3T3 NRU PT with other in vitro tests that allow the safety or phototoxic potency of formulations to be assessed.
More detailed Dermal Phototoxicity information is available by clicking here.
Click here to review Dermal Phototoxicity technical references on the MatTek Web site.
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EpiOcular In Vitro Toxicology Tests
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EpiOcular™ Eye Model
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The EpiOcular (Model OCL-200) corneal model is a three-dimensional in vitro tissue construct that models the human corneal epithelium. The model consists of normal, human-derived epidermal keratinocytes (neonatal-foreskin tissue) cultured on a permeable polycarbonate membrane which forms a stratified, squamous multi-layered epithelium similar to that of the cornea. The tissue construct has an air-liquid interface and exhibits in vivo-like morphological and growth characteristics that allows test materials to be directly applied to the surface of the tissue and to approximate in vivo conditions. Method endpoint is the MTT ET-50 Tissue Viability Assay.1
Ocular (Eye) Irritation Potential:
Ocular Irritation Potential is traditionally determined using the Draize (Rabbit Eye) Ocular Irritation Test. The MatTek EpiOcular (OCL-200) in vitro corneal model is designed to replace the Draize Test.
Although EpiOcular is not yet a validated alternative test method for the determination of ocular irritation potential, there has been significant recent progress. In particular, Colgate-Palmolive Co. has been so impressed with EpiOcular test results they are building on the existing EpiOcular QC data set and championing EpiOcular through the ICCVAM validation process for acceptance by U.S. regulators. This Colgate-Palmolive project is at an advanced stage and is the culmination of a 4-plus year effort to rigorously validate EpiOcular with a broad range of test articles in a formal multi-center study.
Click here to learn more about EpiOcular as a Draize Test alternative.
Click here to review EpiOcular technical references on the MatTek Web site.
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Next Steps:
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1. MTT ET-50 Tissue Viability Assay - A colorimetric assay system that measures the reduction of a yellow tetrazolium component (MTT) into an insoluble purple formazan product by the mitochondria of viable cells. After incubation of the cells with the MTT reagent for several hours, a solution is added to lyse the cells and solubilize the colored crystals. Samples are read using an ELISA plate reader at a wavelength of 570 nm. The amount of color produced is directly proportional to the number of viable cells. ET-50 refers to the time required to reduce tissue viability to 50%.
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