The Institute for In Vitro Sciences (IIVS) is sponsoring a series of workshops to identify, discuss and develop recommendations for optimal scientific/technical approaches for utilizing in vitro assay data within and across tobacco and nicotine product categories. Workshops provide a unique opportunity for invited expert stakeholders to share experiences and to develop recommendations that may serve as a resource for developing optimal approaches and data to evaluate the toxicity of tobacco and nicotine products. It is envisioned that some of these recommendations would form the basis for the generation of guidance documents and/or serve as authoritative reference publications for optimal methodologies and data interpretation and to support regulatory submissions. Invited experts for the IIVS workshops include scientists from tobacco companies, contract research organizations, US regulatory agencies, and other in vitro assay experts with tobacco product and/or genetic toxicology experience. The format for this workshop series is primarily discussion among participants which provides an environment to tackle issues in detail. Participants are expected to actively participate by collecting relevant published and unpublished non-proprietary research information, to offer experiences and expert opinions, and to actively share with other workgroup members. While the focus will be on the widely used regulatory in vitro genetic toxicology assays, it is important to note that much of the discussion will be applicable to all in vitro assays. As a part of the workshop discussion, data gaps will be identified. Thus, in addition to recommendations based on current information, this workshop series will provide key research questions that need to be addressed by the scientific community. This will provide a useful roadmap for research that can have direct impact on the regulation of tobacco products and on protecting human health related to consumer use of tobacco products. The product of these workshops will be a series of scientific publications and meeting presentations that can be utilized by all stakeholders. Prior to the first workshop (November 27-28, 2018) important issues for using in vitro genotoxicity assays for evaluating tobacco and nicotine products were identified. During the first workshop issues were triaged into three priority categories based on the amount of available information.
The Family Smoking Prevention and Tobacco Control Act gave the FDA regulatory authority over next generation tobacco products (NGTP) such as E-vapor products. E-vapor product liquids contain a variety of ingredient combinations that should be assessed for human risk. One human lung-relevant testing platform with reasonable throughput, is human precision-cut lung slices (HuPCLS). HuPCLS are arguably the most complex non-animal model of the lung, retaining native architecture and immune-competent cells over multi-week culture periods. HuPCLS were exposed to three concentrations (0.1%, 0.5%, and 1.2%) of propylene glycol (PG ; an E-vapor product constituent) continuously for 16 days. Exposure-effects were evaluated biochemically (WST-8 assay) and histologically viability assessment of H&E stained slides). Positive control treatments consisted of 10μM Phortress and 13μM bleomycin. HuPCLS were fed every day with fresh medium ± treatment and harvested at days 4, 8, and 16. Untreated control UC) HuPCLS viability was confirmed using protein and a denylate kinase assays. Over 16 days in culture, UC lost 30% viability while WST-8 results indicated no loss over 16 days in culture. Phortress caused severe damage by day 4 and bleomycin by day 8 (histologically & WST-8 viability). Prolonged 1.2% PG exposure diminished WST-8 viability by ~30% at day 16 which agreed with histological results. High osmolality is the suspected mechanism of toxicity. There was no effect histologically or via WST-8 viability for prolonged exposure to 0.1% and 0.5% PG. In summary, PG, a common E-vapor product ingredient, at 1.2% had adverse effects in a human pulmonary model in an exaggerated exposure regimen(prolonged exposures with changes in osmolarity). The HuPCLS platform has huge potential to serve as a screening tool for e-liquid(and other materials of concern) by elucidating potentially relevant, long-term events following NGTP ingredient exposure.
The Transient Receptor Potential Vanilloid type 1 (TRPV1) receptor is one of the most well characterized pain-inducing receptors and has been recently identified as a valuable tool to predict eye stinging potential of surfactant based formulations. In this study we sought to predict eye stinging of nonsurfactant based cosmetic formulations by studying TRPV1 activity using the NociOcular assay. In the NociOcular assay, TRPV1 expressing neuroblastoma cells are exposed to test substance and TRPV1 activity is measured by acute increases in intracellular calcium. Three of the formulations induced stinging in the human test and were also positive in the NociOcular assay. The other four formulations evaluated were classified as stinging in the human test, but a conclusive determination could not be made in the NociOcular assay as the formulations were not fully soluble in assay buffers. The formulations were also evaluated in the EpiOcularTM assay, an established in vitro model for eye irritation utilized by the cosmetics industry. The Epiocular™ assay results did not correlate with the human sting data. Our data support that the NociOcular assay may be a valuable in vitro tool to predict human eye stinging sensation for cosmetic formulations. Future efforts seeks to further expand the applicability of the assay to product types other than surfactant based formulations.
In order to further promote the implementation of Directive 2010/63/EU, the European Commission issued calls for a number of related projects last year. One of these projects is aimed at facilitating the uptake of non-animal alternatives by developing two e-learning modules. The contract for this project was awarded to a consortium consisting of SYRCLE, the Swiss 3R Competence Centre, lnstitute for ln Vitro Sciences, Pharma Launcher and Ecorys UK. This consortium will develop two modules, i.e., one eLearning module focused on searching for existing non-animal alternatives (including systematic reviews) and one module targeted at researchers who want to develop reliable and relevant non-animal alternatives for regulatory use taking into account Good In Vitro Method Practices (GIVIMP). The quality of the developed modules will be assessed by external review groups. The learning outcomes will be presented to the commission along with the design of the assignments through which these outcomes will be realised.
While the skin sensitization hazard of substances can readily be identified using non-animal methods, the classification of potency into UN GHS sub-categories 1A and 1B remains challenging. The kinetic direct peptide reactivity assay (kDPRA) is a modification of the DPRA (OECD TG 442C) wherein the reaction kinetics of a test substance towards a synthetic cysteine-containing peptide is evaluated. For this purpose, several concentrations of the test substance are incubated with the synthetic peptide for several incubation times at 25°C. After the respective incubation time, the reaction is stopped by addition of the fluorescent dye monobromobimane (mBBr). The highly reactive and non-fluorescent mBBr rapidly reacts with unbound cysteine moieties of the model peptide to form a fluorescent complex. The remaining non-depleted peptide concentration is determined thereafter by fluorescence measurement at precisely defined time points. Kinetic rates of peptide depletion are then used to distinguish between two levels of skin sensitization potency, i.e. to discriminate between CLP/UN GHS sub-categories 1A and 1B. During an in house validation (Wareing et al., 2017) 35 of 38 substances with LLNA-based sensitizing potency were correctly assigned to the potency sub-categories, and the predictivity for 14 human data was similarly high. These results warranted the kDPRA for further validation. Here we present the results of a ring trial testing 24 blind-coded chemicals in seven labs. In parallel we present the extension of the kDPRA database to further assess the predictive capacity of the assay. Eventually the kDPRA should be used as a part of defined approach(es) with a quantitative data integration procedure for skin sensitization potency assessment.
It is recommended that an evaluation of the impact of shipping of Reconstructed human Epidermis (RhE) tissues be conducted especially after long-haul airfreight shipments. The OECD Test Guideline 439 (OECD TG 439), In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method, recommends that users do so by verifying the barrier properties of the tissues after receipt. In this study, LabCyte EPI-MODEL 24 tissues were received in the USA after an overnight shipment from Japan and were tested to evaluate their performance after shipment using several endpoints. First, the viability of untreated tissues incubated overnight in culture medium was assessed using the vital dye MTT and expressed as Optical Density (OD570-650) values. The calculated OD values were 1.2 (J-TEC) and 0.99 (IIVS) and within the range established by the manufacturer (0.8 - 2.5). The barrier function was further evaluated after the tissues were exposed to the assay negative control (Phosphate Buffered Saline - PBS) and to four concentrations of the positive control, Sodium Lauryl Sulfate (SLS) (1.0, 2.0, 3.0 and 4.0 mg/mL). The calculated IC50 values were 2.7 mg/mL (J-TEC) and 3.4 mg/mL (IIVS), respectively, and within the established historical range (1.4 - 4.0 mg/mL). The analysis of the results generated by the two labs (J-TEC and IIVS) demonstrated that the tissue lot met the acceptance criteria developed by the tissue manufacturer under conditions of shipping stress. Finally, the histological analysis of untreated fixed tissues identified all tissue layers and supported the conclusion that the tissue model was acceptable for use in subsequent studies after long-haul airfreight shipment. Such shipping studies are critical to gaining confidence in the tissues’ performance when used for research, industrial, and regulatory testing purposes.
The selection of reference and proficiency chemicals is an important component of method validation and proficiency evaluations. Reference chemicals are a set of test substances used by a method developer to evaluate there liability and relevance of a new method, in comparison to reference data (usually to a validated reference method). Proficiency chemicals, as defined in OECD Guidance Document on Good In Vitro Method Practices, are defined post validation as a subset of the reference chemicals, or other chemicals with sufficient supporting data, that are used by naive laboratories to demonstrate technical competence with a validated test method. Proficiency chemicals should cover different physical states, several chemical classes within the applicability domain of the method and yield the full range of response (in the validated reference method and in vivo). They shall be commercially available (at non prohibitive costs) and have high quality reference data. If reference and subsequent proficiency chemicals are chosen without sufficient evidence for their inclusion, both test method evaluation and demonstration of technical proficiency can be hampered. In this report we present cases in which the selection of reference chemicals led to problems in the reproduction of the reference results and demonstration of technical proficiency.
Human-relevant, in vitro/ex vivo assays are considered an ethical and economically viable manner by which to screen the thousands of chemicals requiring hazard assessment. Of the 3-dimensional models, human precision-cut lung slices (PCLS) are often considered the most physiologically relevant pulmonary test system, but lower throughput and difficulties in cryopreservation have hampered PCLS use. We have modified a tissue slicer to accommodate 3 tissue cores for simultaneous slicing. Increased slice production was quantified using agarose and tissue cores in the slicer. To evaluate cryopreservation of PCLS, we have tested 5 cryopreservation formulations using PCLS (frozen on the day of slicing, or after overnight culture). Thawed slice viability in each of the groups was assessed with the WST-8 viability assay, prior to fixation and histological evaluation. The slicer modification resulted in 2.8-fold and 2.4-fold more slices from agarose cores, and lung cores, respectively. Cryopreservation efforts indicated freezing after slicing yields better average viability (48-73% of fresh, non-frozen control) than culturing overnight and freezing (13-54% of control) when assessing health over 4 days, post-thaw. Cryopreservation buffers containing University of Wisconsin preservation solution preserved viability the best (54%-90% of non-frozen control). Histological findings concurred with WST-8 viability results and indicated the retention of healthy lung tissue features (>75% of normal), post-thaw. The increased PCLS production indicates larger (or multiple) studies can be initiated from one donor lung. The promising cryopreservation results suggest slices can be banked and utilized at a later date, potentially even allowing the same donor’s tissue to be used repeatedly.
Next generation tobacco and nicotine products (NGPs) such as electronic cigarettes (EC) and tobacco heating products (THP) have reduced toxicity and hold great potential for reducing the risks associated with cigarette smoking. NGPs may also have hygiene benefits for consumers that switch to these products. In this study, the level of skin staining was assessed following exposure to a scientific reference cigarette (3R4F) and NGPs across the risk continuum; a prototype EC or a commercial THP (glo™). Test articles (TAs) were prepared by capturing cigarette smoke or EC/THP aerosol on Cambridge filter pads followed by elution with Dimethyl Sulfoxide (DMSO). Abattoir-obtained porcine skin (ø 0.5) samples were incubated at 37°C with each TA or DMSO control for 0, 0.25, 0.5, 1, 4 and 6h. Colour readings (L*, a*, b*) were measured for individual skin samples using a Konica Minolta CM-700d Spectrophotometer and mean colour change (ΔE) for each TA compared. The reference cigarette 3R4F TA showed the greatest colour change, which was significantly higher than the EC and THP TAs, both of which showed relatively little colour change. The mean ΔE values at 6 hrs were: 21.78 ± 2.80, 8.38 ± 2.93, 10.01 ± 2.53 and 9.23 ± 2.87 for 3R4F, a prototype EC, glo™ or DMSO respectively. The cigarette smoke extract significantly increased the level of staining of the skin samples whereas EC or the THP TAs induced little or no staining with values comparable to the DMSO control. For the first time, diverse NGPs across the risk continuum have been assessed in vitro for their impact on skin staining. Further studies are required to assess the long-term impact on skin staining of NGP aerosols.
FDA’s recently launched Predictive Toxicology Roadmap calls for the optimization of non-animal methods for the safety evaluation of drugs, consumer products and medical devices. We have created an Industry Consortium comprised of manufacturers of personal lubricants/vaginal moisturizers and companies interested in the advancement of animal alternatives working collaboratively with stakeholders and the US FDA to develop an in vitro testing approach that could be used in place of the rabbit vaginal irritation (RVI) in pre-market submissions.