Apoptosis in chronic adult periodontitis analyzed by in situ DNA breaks, electron microscopy, and immunohistochemistry
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Background: Apoptosis is an evolutionary form of physiological cell death. Previous studies suggest that apoptosis is involved in the pathogenesis of periodontal diseases. Therefore, we studied the apoptotic events in the gingival tissue of chronic adult periodontitis patients. Methods: Gingival tissue biopsies from 22 patients with chronic adult periodontitis and from 11 healthy controls were obtained. Criteria for patient inclusion in the periodontitis group were a minimum of 14 natural teeth, excluding third molars, with at least 10 posterior teeth; 5 to 6 sites with probing depth ≥5 mm; attachment loss ≥3 mm; and extensive radiographic bone loss. The control group included healthy subjects with no prior history of periodontal disease. Apoptosis was determined using the terminal TdT-mediated dUTP-biotin nick end labeling (TUNEL) technique; electron microscopic analysis; and expression of Caspase-3, Fas, FasL, Bcl-2, and p53 by immunohistochemistry. Results: TUNEL-positive cells and cells exhibiting chromatin condensation by electron microscopy were observed in the inflammatory infiltrate of biopsies obtained from periodontitis patients. Most of the TUNEL-positive cells belonged to neutrophil cell populations as they were stained with anti-myeloperoxidase. Positive staining for active-caspase 3, Fas, FasL, and p53 was only observed in the inflammatory infiltrate from periodontitis biopsies, whereas Bcl-2 cells were present in both periodontitis patients and healthy controls. Conclusions: Our findings establish that apoptosis is induced in the periodontal tissue by host and microbial factors and support the hypothesis that apoptotic mechanisms could be implicated in the inflammatory process associated with gingival tissue destruction observed in adult periodontitis patients.