Candidate MRTP Aerosol has Low Impact on Organotypic Gingival Cultures

Objectives: One of the major lifestyle-related risk factors for periodontal diseases is smoking, which can alter the structure of the epithelial mucosa, impair the inflammatory response, and modify the redox condition of the oral cavity. Harm reduction through the development of Modified Risk Tobacco Products (MRTP) provides a promising opportunity for adult smokers who would otherwise continue cigarette smoking. Using a systems toxicology approach, we investigated and compared the effects of exposure to reference (3R4F) cigarette smoke (CS) with exposure to aerosol from a heat-not-burn technology-based potential MRTP, the Tobacco Heating System (THS) 2.2.
Methods: Human gingival epithelial organotypic cultures (EpiGingival™; MatTek) were repeatedly exposed (3 days) to 28 min CS or THS2.2 aerosol. CS and THS2.2 aerosol exposures were performed with similar nicotine content (49.4 or 84.6 mg nicotine/L CS for 3R4F and 54.6 or 100.4 mg/L aerosol for THS2.2), and employed in the exposure design. The inflammatory status was measured by quantifying the release of proinflammatory mediators. Transcriptomics and metabolomics analysis were also performed.
Results: Minor histopathological alterations and minimal cytotoxicity were observed upon THS2.2 aerosol exposure, while marked toxicity was observed for CS. Transcriptomics analysis indicated a general reduction in the relative biological impact factor (~79% lower than CS for the high THS2.2 aerosol concentration) and the analysis of selected biological networks, such as oxidative stress, xenobiotic metabolism, and inflammation, showed alterations in cultures exposed to THS2.2 aerosol were consistently lower than CS. According to the transcriptomics results, the metabolomic investigation confirmed the reduced impact in THS2.2 aerosol-exposed cultures compared to CS, with only 13 metabolites altered versus 181, respectively.
Conclusions: This study indicates that exposure to THS2.2 aerosol had a lower impact than CS on the pathophysiology of human gingival organotypic cultures and that this model system resembled the response of native gingival epithelium to CS and disease conditions, making it a possible candidate for pre-clinical in vitro investigations.