Oxidative DNA damage is a preliminary step during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide.

The aim of this study was to investigate oxidative DNA damage during 4-nitroquinoline 1-oxide (4NQO)-induced rat tongue carcinogenesis. For this purpose, male Wistar rats were distributed into three groups of 10 animals each and treated with 50 ppm 4NQO solution through their drinking water for 4, 12, and 20 weeks. Ten animals were used as negative control. The alkaline Comet assay modified with lesion-specific enzymes was used to detect single and double strand breaks, labile sites (SBs), and oxidised purines and pyrimidines. Although no histopathological abnormalities were induced in the epithelium after 4 weeks of carcinogen exposure, oxidative DNA damage was detected in the 'normal' oral epithelium. In pre-neoplastic lesions and squamous cell carcinomas induced after 12 and 20 weeks following carcinogen exposure, respectively, oxidative DNA damage was also increased (P < 0.05) when compared to negative control. In conclusion, our results suggest that oxidative DNA damage is an early event during multistep carcinogenesis assay induced by 4NQO. This kind of approach should be considered to persons with high risk of oral cancer, such as in smokers or alcohol consumers.

The role of matrix metalloproteinases 2 and 9 during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide.

Matrix metalloproteinases (MMPs) are implicated in a wide range of physiological and pathological processes, including morphogenesis, wound healing, angiogenesis, inflammation, and cancer. The purpose of this study was to characterize the role of MMPs as depicted by the expression of MMP-2 and MMP-9 during 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis. Male Wistar rats were distributed into three groups of 10 animals each and treated with 4-nitroquinoline 1-oxide solution at 50 ppm through their drinking water for 4, 12, and 20 weeks. Ten animals were used as control group. No histopathological abnormalities were induced in the epithelium after 4 weeks of carcinogen exposure; however, immunoexpression of MMP-2 was noticed. The same picture occurred to MMP-9, in which positive expression was detected for this immunomarker. MMP-2 and MMP-9 showed positive expression either in pre-neoplastic lesions at 12 weeks following carcinogen exposure or in well-differentiated squamous cell carcinoma induced after 20 weeks of treatment with 4NQO. Taken together, our results support the belief that MMP-2 and MMP-9 play important role during malignant transformation and conversion of oral mucosa as assessed by immunohistochemistry.

Use of platelet-rich plasma under autogenous onlay bone grafts.

OBJECTIVES: To analyze the healing of autogenous onlay bone grafts in three different situations, focusing on the interface area. MATERIAL AND METHODS: Sixteen rabbits underwent autogenous bone graft surgeries in the calvaria. The block bone grafts were positioned in three different situations: direct contact between bone graft and receptor bed, graft interposed by particulate bone, and graft interposed by platelet-rich plasma (PRP). After 7, 15, 30, and 60 days, the specimens were retrieved for histological and morphometric evaluation. RESULTS: All groups healed uneventfully and presented incorporation of the grafts after 30 days. A slightly more evident new bone formation could be observed in the PRP group in the first analyzed period, and an earlier maturation of bone in the last period, although no statistically significant differences were achieved. CONCLUSION: The use of additional material between the bone graft and the receptor bed when using the onlay technique must be carefully considered, taking into account the size of the reconstruction and the cost/benefit relation. The addition of PRP in between autogenous bone blocks and the receptor bed did not confer significant benefit for the new bone formation and healing on the calvaria of bone of rabbits.