MatTek’s EpiDerm™ in vitro 3-D human skin tissue model and EpiOcular™ in vitro 3-D human corneal tissue model have become increasingly important as replacements for traditional animal-based toxicology testing in the cosmetics, personal care products, household cleaning products, chemical and pharmaceutical industries.
Two EpiDerm-based test methods, skin irritation and dermal corrosion, are now formally validated as alternative methods in the European Union (EU) while several others continue through the validation process as defined by regulators in the EU (ECVAM) and the United States (ICCVAM).
MatTek’s EpiAirway™ human cell-derived in vitro 3-D tracheal/bronchial tissue 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 3-D buccal (inner cheek) tissue model and EpiVaginal™ human cell-derived in vitro 3-D ecto-cervical vaginal tissue model are also well-suited for cytotoxicity studies.
Contact MatTek to receive a list of Contract Testing Labs (CTL's) using our in vitro tissue models in their toxicology assays.
- EpiDerm™ Skin Model
EpiDerm In Vitro Toxicology Tests
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.
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.
MatTek offers 2 Skin Irritation test methods – one for Hazard Identification (the ECVAM-validated method for irritant/non-irritant determination), the other for measuring Irritation Potency Assessment (typical application: formulation development). The basic differences between the two tests and an overview of each test method are provided on MatTek’s Skin Irritation Measurement Web page (link below).
ECVAM-Validated EpiDerm Skin Irritation Test Method:
The ECVAM Scientific Advisory Committee (ESAC) endorsed the scientific validity of the EpiDerm SIT (Skin Irritation Test) method at its November 2008 meeting (link to MatTek press release).
The EpiDerm SIT (Skin Irritation Test) method is a modification of the previously validated EpiDerm skin irritation method. The main modification is the increased exposure time to test substances from 15 to 60 minutes, while all other essential model parameters remained unchanged.
Please review the EpiDerm Skin Irritation "Hazard Identification" test method on the EpiDerm Skin Irritation Measurement Web page for more details on this ECVAM-validated test method (link below).
Additional Skin Irritation Information:
Detailed Skin Irritation Measurement Information
EpiDerm Skin Irritation Technical References
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-CORR) 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.
Detailed Dermal Corrosion Measurement Information
EpiDerm Dermal Corrosion Technical References
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.
Detailed Dermal Phototoxicity Measurement Information
EpiDerm Dermal Phototoxicity Technical References
- EpiOcular™ Eye Model
EpiOcular In Vitro Toxicology Tests
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.
Learn more about EpiOcular as a Draize Test alternative
EpiOcular Ocular Irritation Technical References
Review In Vitro Assay Basics
Detailed PRODUCT Information
Detailed APPLICATIONS Information
Request MatTek Literature
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%.