Mitchell Klausner

Further development of the EpiDerm 3D reconstructed human skin micronucleus (RSMN) assay.

The upcoming ban on testing of cosmetics in animals by the European Unions 7th Amendment to the Cosmetics Directive will require genotoxicity safety assessments of cosmetics ingredients and final formulations to be based primarily on in vitro genotoxicity tests. The current in vitro test battery produces an unacceptably high rate of false positives, and used by itself would effectively prevent the use and development of many ingredients that are actually safe for human use. To address the need for an in vitro test that is more predictive of genotoxicity in vivo, we have developed an in vitro micronucleus assay using a three-dimensional human reconstructed skin model (EpiDerm) that more closely mimics the normal dermal exposure route of chemicals. We have refined this model and assessed its ability to predict genotoxicity of a battery of chemicals that have been previously classified as genotoxins or non-genotoxins based on in vivo rodent skin tests. Our reconstructed skin micronucleus assay correctly identified 7 genotoxins and 5 non-genotoxins, demonstrating its potential to have a higher predictive value than currently available in vitro genotoxicity tests, and its utility as part of a comprehensive in vitro genotoxicity testing strategy.

Development of an in vitro alternative assay method for vaginal irritation

The vaginal mucosa is commonly exposed to chemicals and therapeutic agents that may result in irritation and/or inflammation. In addition to acute effects, vaginal irritation and inflammation can make women more susceptible to infections such as HIV-1 and herpes simplex virus 2 (HSV-2). Hence, the vaginal irritation potential of feminine care formulations and vaginally administered therapeutic agents is a significant public health concern. Traditionally, testing of such materials has been performed using the rabbit vaginal irritation (RVI) assay. In the current study, we investigated whether the organotypic, highly differentiated EpiVaginal™ tissue could be used as a non-animal alternative to the RVI test. The EpiVaginal tissue was exposed to a single application of ingredients commonly found in feminine hygiene products and the effects on tissue viability (MTT assay), barrier disruption (measured by transepithelial electrical resistance, TEER and sodium fluorescein (NaFl) leakage), and inflammatory cytokine release (interleukin (IL)-1α, IL-1β, IL-6, and IL-8) patterns were examined. When compared to untreated controls, two irritating ingredients, nonoxynol 9 and benzalkonium chloride, reduced tissue viability to <40% and TEER to <60% while increasing NaFl leakage by 11-24% and IL-1α and IL-1β release by >100%. Four other non-irritating materials had minimal effects on these parameters. Assay reproducibility was confirmed by testing the chemicals using three different tissue production lots and by using tissues reconstructed from cells obtained from three different donors. Coefficients of variation between tissue lots reconstructed with cells obtained from the same donor or lots reconstructed with cells obtained from different donors were less than 10% and 12%, respectively. In conclusion, decreases in tissue viability and barrier function and increases in IL-1α and IL-1β release appear to be useful endpoints for preclinical screening of topically applied chemicals and formulations for their vaginal irritation potential.

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

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

Microvesicating effects of sulfur mustard on an in vitro human skin model

Bis-(beta-chloroethyl) sulfide (SM) is a potent skin vesicant previously used for chemical warfare. Progress in determination of the mechanistic basis of SM pathology, and development of prophylactic and/or therapeutic countermeasures to SM exposure has been hampered by lack of physiologically relevant models of human skin. The current work evaluated a newly developed tissue engineered full-thickness human skin model in a completely in vitro approach to investigation of SM-induced dermal pathology. The model was first characterized with regard to overall morphology, lipid composition, basement membrane (BM) composition and ultrastructural features that are important targets of SM pathologic activity. Well-developed BM ultrastructural features were observed at the dermal-epidermal junction (DEJ), thus demonstrating successful resolution of a primary deficiency of models previously evaluated for SM studies. Studies were then conducted to evaluate histopathological effects of SM on the model. Good replication of in vivo effects was observed, including apoptosis of basal keratinocytes (KC) and microblister formation at the DEJ. Tissue engineered skin models with well-developed basement membrane structures thus appear to be useful tools for in vitro mechanistic studies of SM vesicant activity and development of preventive/therapeutic approaches for SM pathology.

Intranasal Delivery of Recombinant Human Parathyroid Hormone [hPTH (1–34)], Teriparatide in Rats

The aim of this study was to explore the nasal route as an alternative to daily subcutaneous injections of hPTH (1–34). Anesthetized rats were surgically prepared and nasally dosed with aqueous solutions of hPTH (1–34). Plasma samples were assayed by radioimmunoassay and data generated fit to two‐ (intravenous) and one‐ (intranasal) compartment pharmacokinetic models using WinNonlin®. The toxicity of hPTH (1–34) solution administered to the rats was assessed by screening its effect on transepithelial electrical resistance, potential difference, paracellular marker permeation, tissue viability, and protein leakage using the EpiAirway® tissue model. The intranasal absorption of hPTH (1–34) was rapid; the absorption rate constants (α) were 33.2 ± 24 h− 1 [without bovine serum albumin (BSA)] and 9.8 ± 5.1 h− 1 (with 1% BSA). The maximum plasma concentrations (Cmax): 151 ± 24 pg/mL (without BSA) and 176 ± 37 (with 1% BSA) were attained within approximately 15 min. The intranasal bioavailabilities (Fabs) were 12.1 ± 3.4% (without BSA) and 17.6 ± 1.5% (with 1% BSA). The hPTH (1–34) formulation administered to the rats had no detrimental effect on the EpiAirway® tissue epithelial electrical parameters and functional integrity. Based on the results of this study, the nasal route appears to be a prospective alternative to subcutaneous injections of hPTH (1–34).

A plasmacytoid dendritic cell (CD123+/CD11c−) based assay system to predict contact allergenicity of chemicals

A predictive allergenicity test system for assessing the contact allergenicity of chemicals is needed by the cosmetic and pharmaceutical industry to monitor product safety in the marketplace. Development of such non-animal alternative assay systems for skin sensitization and hazard identification has been pursued by policy makers and regulatory agencies. We investigated whether phenotypic and functional changes to a subset of dendritic cells (DC), plasmacytoid DC (pDC), could be used to identify contact allergens. To achieve this goal, normal human DC were generated from CD34+ progenitor cells and cryopreserved. Frozen DC were thawed and the pDC fraction (CD123+/CD11c-) was harvested using FACS sorting. The pDC were cultured, expanded, and exposed to chemical allergens (N=26) or non-allergens (N=22). Concentrations of each chemical that resulted in >50% viability was determined using FACS analysis of propidium iodide stained cells using pDC from 2 to 5 donors. Expression of the surface marker, CD86, which has been implicated in dendritic cell maturation, was used as a marker of allergenicity. CD86 expression increased (> or =1.5-fold) for 25 of 26 allergens (sensitivity=96%) but did not increase for 19 of 22 non-allergens (specificity=86%). In a direct comparison to historical data for the regulatory approved, mouse local lymph node assay (LLNA) for 23 allergens and 22 non-allergens, the pDC method had sensitivity and specificity of 96% and 86%, respectively, while the sensitivity and specificity of the LLNA assay was 83% and 82%, respectively. In conclusion, CD86 expression in pDC appears to be a sensitive and specific indicator to identify contact allergenicity. Such an assay method utilizing normal human cells will be useful for high throughput screening of chemicals for allergenicity.

Evaluation of EpiDerm full thickness-300 (EFT-300) as an in vitro model for skin irritation: studies on aliphatic hydrocarbons.

The aim of this study was to understand the skin irritation effects of saturated aliphatic hydrocarbons (HCs), C9-C16, found jet fuels using in vitro 3-dimensional EpiDerm full thickness-300 (EFT-300) skin cultures. The EFT-300 cultures were treated with 2.5microl of HCs and the culture medium and skin samples were collected at 24 and 48h to measure the release of various inflammatory biomarkers (IL-1alpha, IL-6 and IL-8). To validate the in vitro results, in vivo skin irritation studies were carried out in hairless rats by measuring trans epidermal water loss (TEWL) and erythema following un-occlusive dermal exposure of HCs for 72h. The MTT tissue viability assay results with the EFT-300 tissue show that 2.5microl/tissue ( approximately 4.1microl/cm(2)) of the HCs did not induce any significant changes in the tissue viability for exposure times up to 48h of exposure. Microscopic observation of the EFT-300 cross-sections indicated that there were no obvious changes in the tissue morphology of the samples at 24h, but after 48h of exposure, tridecane, tetradecane and hexadecane produced a slight thickening and disruption of stratum corneum. Dermal exposures of C12-C16 HCs for 24h significantly increased the expression of IL-1alpha in the skin as well as in the culture medium. Similarly, dermal exposure of all HCs for 24h significantly increased the expression of interleukin-6 (IL-6) and IL-8 in the skin as well as in the culture medium in proportion to the HC chain length. As the exposure time increased to 48h, IL-6 concentrations increased 2-fold compared to the IL-6 values at 24h. The in vivo skin irritation data also showed that both TEWL and erythema scores increased with increased HCs chain length (C9-C16). In conclusion, the EFT-300 showed that the skin irritation profile of HCs was in the order of C9C10C11C12

Human Primary Cell-Based Organotypic Microtissues for Modeling Small Intestinal Drug Absorption

PurposeThe study evaluates the use of new in vitro primary human cell-based organotypic small intestinal (SMI) microtissues for predicting intestinal drug absorption and drug-drug interaction.MethodsThe SMI microtissues were reconstructed using human intestinal fibroblasts and enterocytes cultured on a permeable support. To evaluate the suitability of the intestinal microtissues to model drug absorption, the permeability coefficients across the microtissues were determined for a panel of 11 benchmark drugs with known human absorption and Caco-2 permeability data. Drug-drug interactions were examined using efflux transporter substrates and inhibitors.ResultsThe 3D–intestinal microtissues recapitulate the structural features and physiological barrier properties of the human small intestine. The microtissues also expressed drug transporters and metabolizing enzymes found on the intestinal wall. Functionally, the SMI microtissues were able to discriminate between low and high permeability drugs and correlated better with human absorption data (r2 = 0.91) compared to Caco-2 cells (r2 = 0.71). Finally, the functionality of efflux transporters was confirmed using efflux substrates and inhibitors which resulted in efflux ratios of >2.0 fold and by a decrease in efflux ratios following the addition of inhibitors.ConclusionThe SMI microtissues appear to be a useful pre-clinical tool for predicting drug bioavailability of orally administered drugs.

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

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

New Human Organotypic Corneal Tissue Model for Ophthalmic Drug Delivery Studies

Purpose The purpose of the current work was to develop a physiologically relevant, in vitro human three-dimensional (3D) corneal epithelial tissue model for use in ophthalmic drug development. Methods Normal human corneal epithelial cells were cultured at the air-liquid interface to produce the 3D corneal tissue model. Corneal barrier was determined by measuring transepithelial electrical resistance (TEER). Quantitative PCR arrays were utilized to investigate expression of 84 phase I/II metabolizing enzymes and 84 drug transporter genes. Permeability was evaluated using model compounds with a wide range of hydrophobicity, molecular weight, and excipients. Finally, different formulations of latanoprost and bimatoprost were administered and drug absorption and tissue viability and integrity were investigated. Results Histologic assessment and TEER of the corneal tissue model revealed tissue structure, thickness, and barrier formation (1000 ± 146 Ω·cm2) comparable to native human corneal epithelium. The 3D corneal tissue expressed tight junctions, mucins, and key corneal epithelial detoxification enzymes. Drug-metabolizing enzyme and transporter gene expression in 3D corneal tissue and excised human corneal epithelium were highly correlated (r2 = 0.87). Coefficients of permeation for model drugs in the tissue model and excised rabbit corneas also showed a high correlation (r2 = 0.94). As expected, latanoprost and bimatoprost free acids had much lower permeability (Papp = 1.2 × 10-6 and 1.9 × 10-6) than the corresponding prodrugs (Papp = 2.5 × 10-5 and 5.6 × 10-5), respectively. The presence of 0.02% benzalkonium chloride in ophthalmic formulations significantly affected tissue barrier and viability. Conclusions The newly developed 3D corneal tissue model appears to be very useful for evaluation of corneal drug permeability and safety during ophthalmic drug development.