{'fraction_non_alphanumeric': 0.04235423542354235, 'fraction_numerical': 0.03355335533553355, 'mean_word_length': 4.666666666666667, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Nicotine-induced damage affects gingival fibroblasts in the gingival tissue of rats.

BACKGROUND
Very limited information is available from in vivo studies about whether smoking and/or nicotine affect gingival tissues in the absence of plaque. The purpose of this study is to evaluate the effect of the systemic administration of nicotine in the proliferation and counting of fibroblast-like cells in the gingival tissue of rats.


METHODS
Thirty adult male Wistar rats were randomly assigned into two groups to receive subcutaneous injections of a saline solution (control group = group C) or nicotine solution (group N; 3 mg/kg) twice a day. The animals were euthanized 37, 44, or 51 days after the first subcutaneous injection. Specimens were routinely processed for serial histologic sections. Five fields of view in the connective tissue adjacent to the gingival epithelium and above the alveolar bone crest of the maxillary first molar were selected for the counting of fibroblast-like cells. Data were statistically analyzed (P <0.05).


RESULTS
The intergroup analysis detected a lower number of fibroblast-like cells in group N compared to group C on days 37 (2.65 ± 1.41 and 6.67 ± 3.25, respectively), 44 (2.70 ± 1.84 and 8.57 ± 2.37, respectively), and 51 (2.09 ± 1.41 and 7.49 ± 2.60, respectively) (P <0.05). The quantification of fibroblast-like cells showed no significant difference (P >0.05) in the intragroup analysis of control and nicotine throughout experimental periods. In the intergroup analysis, group N had reduced proliferating cell nuclear antigen-positive fibroblasts compared to group C in all periods (P <0.05).


CONCLUSION
The daily systemic administration of nicotine negatively affected, in vivo, the number and proliferation of fibroblast-like cells in the gingival tissue of rats.