Advanced in vitro exposure systems.

An experimental aerosol air–agar interface mouse lymphoma assay methodology

13. Jul. 2020

DOI: https://doi.org/10.1016/j.mrgentox.2020.503230 

Authors
Thorne D1, Hollings M2, Kilford J2, Clements J2, Payne R2, Ballantyne M2, Dalrymple, A1, Dillon, D1, Meredith, C1, Gaҫa, M1  
 
1 British American Tobacco, R&D, Southampton, Hampshire SO15 8TL, UK. 
2 Covance Laboratories Ltd, Otely Road, Harrogate, HG1 PY, UK

 

Highlights

  • An experimental concept of exposing L5178Y cells at the air-agar-interface
  • Cells were lightly seeded on an agar surface to achieve exposure
  • Flowing air, plating and recovery efficiencies from the agar-surface were investigated
  • Positive controls were responsive, suggesting a clear cellular interaction with the agar-matrix 
  • Cigarette smoke aerosol showed a dose-response relationship with increasing mutant frequencies

 

Abstract 
This work investigates a completely novel and experimental concept of exposing L5178Y cells at the air-agar-interface to mainstream cigarette smoke aerosol (Kentucky reference 3R4F). This study highlights the associated challenges of combining a suspension cell line alongside an in vitro aerosol exposure system. To achieve a monolayer, cells were ‘seeded’ in a concentrated cell super-mix suspension onto an RPMI/agar-matrix -base. The resulting cell suspension media was adsorbed into the agar base leaving the L5178Y cells lightly suspended on the agar surface, approximating a monolayer. Cells were deemed supportable on the agar-matrix, viable and recoverable. Using Vitrocell VC 10 exposure system and the Ames 4 exposure module, L5178Y cells were successfully exposed to a dynamic cigarette smoke aerosol, recovered and assessed for mutant frequencies, using standard assay procedures. Method development included assessment of flowing air conditions, plating efficiency and recovery of L5178Y cells from the agar-matrix surface. Positive controls MMS and B[a]P were successfully incorporated into the agar-matrix and metabolic activation was achieved by S-9 incorporation into the same agar-base-matrix. B[a]P demonstrated metabolic activation and positive response, suggesting a clear cellular interaction with the agar-matrix. Whole smoke exposed cells in the presence of metabolic activation showed a clear dose response and increasing mutant frequencies, well in excess of the controls (air and incubator) and the global evaluation factor following a 2 or 3 day expression period. This experimental concept demonstrates that L5178Y cells can be exposed to cigarette smoke aerosol, using a completely novel and a previously untested approach. Although this work successfully demonstrates the approach is viable and cells can be plated and maintained on an agar-matrix, more optimisation and robustness assessment is required before it can be considered fully adapted and used alongside other whole aerosol methodologies for the assessment of cigarette smoke and other inhaled aerosols. 

 

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