The aim of the present study was to examine: (1) the effects of nicotine on human gingival fibroblasts (HGF); (2) differences between smokers (greater than or equal to 10 cigarettes/day at least for 5 years) and non-smokers; (3) differences between patients; of different age. HGF were obtained, through biopsies during periodontal surgical procedures, from 15 patients which were divided in 4 groups: 4 patients, smokers aged less than or equal to 25 years; 4 patients non-smokers aged less than or equal to 25 years; 3 patients, smokers aged greater than or equal to 40 years; 4 patients, non-smokers aged greater than or equal to 40 years. Nicotine has been tested in 3 different concentrations: 6 mu g/ml 60 mu g/ml; 600 mu g/ml. To assess cells viability, the neutral red (NR) test was used; to evaluate cell proliferation, the Hoechst test was employed. After 48 h of nicotine exposure, it was found that 600 mu g/ml nicotine was strongly cytotoxic to HGF of all groups, with a significant reduction of both proliferation and viability of cells versus control. Comparison between groups of the same age: when comparing untreated HGF (i.e., control values) of smokers less than or equal to 25 years versus non-smokers less than or equal to 25 years, cell proliferation, but not viability, was found to be increased in smokers. Both viability and proliferation of control cells of smokers greater than or equal to 40 years were increased versus non-smokers greater than or equal to 40 years. HGF of non-smokers less than or equal to 25 years, when exposed to nicotine 600 mu g/ml, have less viability and proliferation than HGF of smokers of the same age. Comparison between groups of different age: In the smoker group, untreated HGF (i.e., control values) had similar viability and proliferation, irrespective of age, but nicotine 600 mu g/ml kills more HGF in smokers less than or equal to 25 years than in smokers greater than or equal to 40 years. In non-smokers, untreated HGF less than or equal to 25 years replicate less, but are not less viable than HGF greater than or equal to 40 years. When challenged with nicotine 600 mu g/ml, HGF less than or equal to 25 years were less viable than HGF greater than or equal to 40 years. From this study, it appears that the smoking history and the patient age could be relevant for final evaluation of the results, since HGF from smokers are less sensitive to nicotine than HGF from non-smokers, and cells from older donors are more resistant to nicotine than cells from younger donors.
