Expressão imuno-histoquímica das proteínas Ki-67 e Bcl-2 em crescimentos gengivais induzidos por drogas e hiperplasias gengivais inflamatórias

Abstract

Considering that the imbalance between apoptosis and cell proliferation may play an important role in the pathogenesis of drug-induced gingival overgrowth (DIGO), the present study aimed to evaluate the immunohistochemical expression of Ki-67 and Bcl-2 proteins and their relationship with histomorphologic features in DIGOs and inflammatory gingival hyperplasias (IGHs), compared with specimens of healthy gingiva (HG). The study was descriptive-analytical, cross-sectional, observational, qualitative and quantitative. The sample consisted of 20 cases of DIGO, 20 cases of IGH and 20 cases of HG, which underwent histomorphologic and immunohistochemical analysis. In histomorphologic analysis, the following aspects were evaluated: presence of elongated epithelial rete pegs, degree of collagenization, degree of vascularization, intensity and distribution of the inflammatory infiltrate. In immunohistochemical study, the labeling indexes (LIs) for anti-Ki-67 and anti-Bcl-2 antibodies were determined, both in epithelial and connective tissue of specimens. The histomorphologics results revealed presence of elongated epithelial rete pegs toward the connective tissue only in DIGOs, as well as statistically significant association of this group with intense degree of collagenization (p = 0.010). For all groups it was found a higher proportion of cases with intense vascularization, and moderate to intense inflammatory infiltrate with focal distribution (p > 0.05). With respect to immunohistochemical analysis, there were no statistically significant differences between groups regarding the Ki-67 LIs in the epithelial lining (p > 0.05). In the connective tissue, DIGOs, IGHs and HGs showed low Ki-67 LIs (p > 0.05). Regarding the Bcl-2 LIs in the epithelium, the highest mean was found in the group of DIGO (p = 0.061). In turn, in connective tissue, DIGOs showed higher number of immunopositive for Bcl-2 (45.0%) in comparison with IGHs and HGs, but no differences regarding LIs (p > 0.05). There were no statistically significant differences in Ki-67 and Bcl-2 LIs in relation to the histomorphologic characteristics of DIGOs, IGHs and HGs (p > 0.05). Furthermore, in all groups, there were no statistically significant correlations between Ki-67 and Bcl-2 LIs. Therefore, the findings of this study suggest that neither increased fibroblast proliferation nor reduced fibroblast apoptosis is involved in the pathogenesis of DIGOs. On the other hand, the morphology of elongated epithelial rete pegs observed in these lesions may be due to inhibition of apoptosis of keratinocytes rather than an increase in the proliferation of these cell types.