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

Abstract

In vitro aerosol systems offer advantages in generating aerosols and exposing cell cultures at the air-liquid interface (ALI), mimicking human exposure. However, dilution technologies, principles, and characteristics of exposure chambers differ between systems. In addition, various cell types and biological end points can be assessed, meaning that in vitro aerosol data are presented in different ways, so researchers are unable to compare data between systems, studies, and laboratories. In this case study we present the comparison of in vitro data across multiple aerosol exposure studies using a 3R4F reference tobacco product. The first aim assessed whether a consistent in vitro dosimetry approach could gain insight into the characterization of ALI aerosol exposure systems. The second aim assessed whether cytotoxicity data sets generated on contrasting exposure systems with different experimental setups could be directly compared. Cytotoxicity data generated from five independent studies were compared. When plotted on the x-axis as a function of dilution principle, the ''standard way'' to present whole aerosol data, there was little read across between the data sets. Expressing each data set as a function of particulate dose (lg/cm 2) and nicotine concentration (mg), however, allowed comparisons between all data sets and with human daily exposure estimates. Furthermore, compared as a function of dose, the data set showed remarkable commonalities between themselves despite clear study differences. The data demonstrate that in vitro dosimetry techniques can align data between contrasting setups and experimental protocols to facilitate comparisons and provide a link between in vitro, in vivo, and human dosimetry studies.

An interlaboratory in vitro aerosol exposure system reference study

“…3 Thorne et al took this one step further in a case study and demonstrated that delivered dose and biological response can be compared across systems if a consistent measure of exposure was used to normalize data. 27 Underpinning these steps, individual system characterizations which ensure that these systems are fully understood and detailed in regard to their application and nuances must be conducted by each laboratory. To some extent, validation of these systems are ongoing with pre-validation efforts made with individual system characterizations, which appear to be more common place than interlaboratory efforts.…”

A survey of aerosol exposure systems relative to the analysis of cytotoxicity: A Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA) perspective

“…Several recent studies have demonstrated this concept successfully, by bridging data across studies and systems. 19,39 This concept is especially important in the world of next generation tobacco products, such as heated tobacco products and e-cigarettes (ENDS), due to their increasing popularity. Exposure systems are diversifying even further from the ones investigated here, so establishing a strategy to compare between studies and systems is even more important.…”

“…Any strategy for comparing across independent studies must therefore factor in the variability of cell line choice and its impact on results, both in variability and the outcome. A recent study 39 examined just this concept, and demonstrated that different continuous cell lines BALB/C and H292 gave the same response in cytotoxicity on different whole aerosol exposure systems when normalised for delivered dose (mass mg/cm 2 and nicotine mg/ml). The study further demonstrated that two different 3D cell systems (MucilAir TM and EpiAirway TM ) gave the similar results when normalised to mass and nicotine (mass mg/cm 2 and nicotine mg/ml) for a cytotoxicity endpoint.…”

Breathing in vitro: Designs and applications of engineered lung models

“…118 Several studies illustrate the value of these systems, which can be found in the papers by Thorne who provided a comprehensive review of the major tobacco smoke exposure systems available to 2013, 118 and a comparison of in vitro data across multiple smoke exposure studies using reference cigarettes and considering three different smoking machines. 119 In the latter review, Thorne demonstrated that in vitro dosimetry techniques can align data between contrasting setups and experimental protocols, resulting in a link between in vitro, in vivo, and human dosimetry studies.…”