Alveolar bone healing in rats: micro-CT, immunohistochemical and molecular analysis

Abstract Alveolar bone healing after upper incisor extraction in rats is a classical model of preclinical studies. The underlying morphometric, cellular and molecular mechanism, however, remains imprecise in a unique study. Objectives The aim of this study was therefore to characterize the alveolar bone healing after upper incisor extraction in rats by micro computed tomographic (Micro-CT), immunohistochemical and real-time polymerase chain reaction (RT-PCR) analysis. Material and Methods Thirty animals (Rattus norvegicus, Albinus Wistar) were divided into three groups after upper incisors extraction at 7, 14, and 28 days. Micro-CT was evaluated based on the morphometric parameters. Subsequently, the histological analyses and immunostaining of osteoprotegerin (OPG), receptor activator of nuclear kappa B ligand (RANKL) and tartrate resistant acid phosphate (TRAP) was performed. In addition, RT-PCR analyses of OPG, RANKL, the runt-related transcription factor 2 (RUNX2), osteocalcin (OC), osteopontin (OPN), osterix (OST) and receptor activator of nuclear kappa B (RANK) were performed to determine the expression of these proteins in the alveolar bone healing. Results Micro-CT: The morphometric parameters of bone volume and trabecular thickness progressively increased over time. Consequently, a gradual decrease in trabecular separation, trabecular space and total bone porosity was observed. Immunohistochemical: There were no differences statistically significant between the positive labeling for OPG, RANKL and TRAP in the different periods. RT-PCR: At 28 days, there was a significant increase in OPG expression, while RANKL expression and the RANKL/OPG ratio both decreased over time. Conclusion Micro-CT showed the newly formed bone had favorable morphometric characteristics of quality and quantity. Beyond the RUNX2, OC, OPN, OST, and RANK proteins expressed in the alveolar bone healing, OPG and RANKL activity showed to be essential for activation of basic multicellular units during the alveolar bone healing.

Influência do ácido nicotínico ministrado na dieta e por intubagem gástrica sobre a incidência de cárie em ratos submetidos à dieta cariogênica e à ração de laboratório / The influence of nicotinic acid administered in the diet or by gastric intubation on the incidence of dental caries in rats submitted to cariogenic diet and laboratory chow

Foi estudado o efeito do ácido nicotínico ministrado na dieta e por intubagem gástrica sobre a incidência de cárie em ratos submetidos à dieta cariogênica e à ração de laboratório. Ratos que receberam ácido nicotínico misturado na dieta cariogênica ou na ração normal sofreram um aumento na incidência de cárie, porém não estatisticamente significante da dos controles sem tratamento. Por outro lado, ratos que receberam ácido nicotínico por intubagem gástrica apresentaram uma diminuição na incidência de cárie, estatisticamente significante com relação aos seus controles, sem tratamento. Os resultados demonstram que o ácido nicotínico teve uma atuação sistêmica sobre a incidência de cárie, porém a razão pela qual esta vitamina diminuiu a incidência de cárie ainda não é conhecida