Characterization and Application of the VITROCELL VC1 Smoke Exposure System and 3D EpiAirway Models for Toxicological and e-Cigarette Evaluations

Abstract

The VITROCELL VC1 Ò smoke exposure machine is an aerosol exposure system that has been used to conduct toxicological assessments with cigarettes and e-cigarettes and can be used with the human 3D EpiAirwayÔ tissue model (MatTek Corporation). The goals of this study were to assess exposure parameters of the VC1, and evaluate donor-to-donor variability of three EpiAirway tissue donors with the following endpoints: viability, barrier integrity, and gene promoter/expression regulation. Additionally, we applied the EpiAirway model to assess the effects of aerosol from two reference combustible cigarettes and two e-cigarettes. Whole smoke (WS) exposures with Kentucky Reference 3R4F cigarettes and Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA) Monitor were conducted under International Organization for Standardization or Health Canada Intense (HCI) conditions, and e-cigarette exposures were conducted under modified HCI conditions. Particulate deposition and collection were consistent across independent assessments. A decrease in barrier function was accompanied with a dose-dependent decrease in viability for all donors. IC 50 values were reproducible (coefficient of variations, CVs <20%) for all donors with both assays. Under HCI conditions, tissue viability and barrier integrity declined rapidly following 3R4F exposures, while no decline in either endpoint was observed with either e-cigarette. Increases in nuclear factor erythroid 2-related factor 2 (Nrf2) promoter activation through the antioxidant response element and gene expression associated with oxidative stress, inflammation, and metabolism were observed following 3R4F WS exposures, and the Nrf2 promoter was differentially regulated by 3R4F WS compared with gas-vapor-phase exposures. No activation in the Nrf2 promoter was observed for e-cigarette exposures. Collectively, the consistency of the VC1 system and EpiAirway model supports the use of these systems in respiratory toxicological assessments. Furthermore, these systems effectively discriminate the toxic impact of smoke from a combustible cigarette on cell viability and oxidative stress while showing no impact of e-cigarettes in these experiments.

A Case Study for the Comparison ofIn VitroData Across Multiple Aerosol Exposure Studies with Extrapolation to Human Dose

“…Consequently, these systems have applications outside the tobacco industry, but limited information and fewer guidelines exist for the assessment of airborne chemicals in vitro. 11,12 The environment of whole aerosol exposure is diverse in that many combinations exist ranging from those obtained from the same source (uni-source), both exposure system and chamber from the same supplier, [13][14][15] multisourced systems, where technologies have been combined from different suppliers, [16][17][18][19] and finally bespoke where systems have been independently manufactured. 20,21 Irrespective of origin or design, all exposure systems have the main components in common: a smoking engine that generates aerosol, normally consisting of a smoking head and syringe/piston linked to a dilution set up either in the syringe or separate, and an exposure chamber/module that houses the cell cultures.…”

“…To further compound this disparity, whole smoke data are presented in many varying ways, such as ratios of smoke to air, flow rate of mixing air applied to the smoke dilutor, percentages or concentrations of smoke, smoke fractions, cigarette puff numbers, or exposure times. 15,[21][22][23][24] None of these methods offers an indication of cellular exposure or delivered dose. Quantifying dose at the cellular level or at the exposure interface through in vitro dosimetry approaches is a fast-emerging and growing field of research.…”

Characterization of a Vitrocell VC1 Using Nicotine Dosimetry: An Essential Component Toward StandardizedIn VitroAerosol Exposure of Tobacco and Next Generation Nicotine Delivery Products

“…These findings are consistent with other published VC1 dosimetry data, with consistent particulate generation at the source. 21 A concern for any exposure system where multiple test systems may be subjected to smoke or aerosol is whether the exposures are uniform. To this end, aerosol delivery to the cellular interface, as measured in the chamber exposure cell culture medium, was also quantified and found to be reproducible across replicate well positions, p = 0.855 ( Fig.…”

“…Again, such observations are confirmed by other studies utilizing dosimetry approaches, where reproducible aerosol delivery across the exposure module wells was shown. 21,22 Proof of uniform exposure within the same module is important in demonstrating the reliability and accuracy of replicate experiments with the same exposure.…”

“…[15][16][17][18][19] For example, Neilson et al, 20 as part of an in vitro assessment of e-cigarettes in RhuA using a VC1 Smoking Robot, employed the use of quartz crystal microbalances (QCMs) to measure deposited mass and confirm aerosol delivery to the tissues. In another example, using a VC1 smoking robot, Fields et al, 21 assessed aerosols from reference 3R4F cigarette smoke and e-cigarettes by fluorometric analysis of aerosols collected at generation source and cellular exposure. In a previously reported interlaboratory study in four independent laboratories and six different Vitrocell VC10 (VC10) Smoking Robots, the QCMs enabled the robust assessment and characterization of 3R4F whole aerosol generation.…”