Effects of electronic cigarette liquid on monolayer and 3D tissue-engineered models of human gingival mucosa

Background. there is limited data available on potential biological effects of e-cigarettes on human oral tissues. the aimof this study was to evaluate the effects of e-cigarette liquid on the proliferation of normal and cancerous monolayer and 3dmodels of human oral mucosa and oral wound healing after short-term and medium-term exposure.methods. normal human oral fibroblasts (nof), immortalized okf6-teret-2 human oral keratinocytes, and canceroustr146 keratinocyte monolayer cultures and 3d tissue engineered oral mucosal models were exposed to different concentrations (0.1%, 1%, 5% and 10%) of e-cigarette liquid (12 mg/ml nicotine) for 1 hour daily for three days and for 7 days. tissueviability was monitored using the prestoblue assay. wounds were also produced in the middle surface of the monolayersystems vertically using a disposable cell scraper. the alterations in the cell morphology and wound healing were visualizedusing light microscopy and histological examination.results. statistical analysis showed medium-term exposure of tr146 keratinocytes to 5% and 10% e-liquid concentrationssignificantly increased the viability of the cancer cells compared to the negative control. short-term exposure of nofs to10% e-liquid significantly reduced the cell viability, whereas medium-term exposure to all e-liquid concentrations significantly reduced the nof cells’ viability. okf6 cells exhibited significantly lower viability following short-term and mediumterm exposure to all e-cigarette concentrations compared to the negative control. 3d oral mucosal model containing normaloral fibroblasts and keratinocytes showed significant reduction in tissue viability after exposure to 10% e-liquid, whereasmedium-term exposure resulted in significantly lower viability in 5% and 10% concentration groups compared to the negativecontrol. there was a statistically significant difference in wound healing times of both nof and okf6 cells after exposureto 1%, 5% and 10% e-cigarette liquid.conclusion. medium-term exposure to high concentrations of the e-cigarette liquid had cytotoxic effects on normal humanoral fibroblasts and okf6 keratinocytes, but a stimulatory cumulative effect on the growth of cancerous tr146 keratinocytecells as assessed by the prestoblue assay and histological evaluation of 3d oral mucosal models. in addition, e-liquid exposure prolonged the wound healing of nof and okf6 oral mucosa cells.