RESUMO
INTRODUCTION: Calcium hydroxide is used in direct pulp capping of uncontaminated exposed vital pulps caused by mechanical or traumatic injury. Calcium hydroxide creates a high alkaline pH environment and initiates a mineralized tissue formation in the pulp. The exact mechanism by which calcium hydroxide induces the reparative dentin formation is unknown. Because Eph receptors and ephrin ligands play a role in pulp stem cell migration and proliferation, our hypothesis is that calcium hydroxide-related odontogenic/osteogenic differentiation may be associated with Eph-ephrin interaction. The aim of this study was to investigate whether Eph-ephrin interaction regulates odontogenic/osteogenic differentiation with calcium hydroxide. METHODS: Primary pulp cells were harvested from the molars of C57BL/6 mice. The cells were treated with calcium hydroxide. Immunofluorescence was used to detect protein expression. A knockout of the ephrinB1 or EphB2 gene was performed with short hairpin RNAs. Cell migration, proliferation, and gene expression were then analyzed. RESULTS: Calcium hydroxide stimulated EphB2 gene expression but suppressed ephrinB1 gene expression at the proliferation stage. However, calcium hydroxide stimulated both ephrinB1 and EphB2 gene expression at the differentiation stage. In addition, EphB2 localized at ephrinB1-positive cells at the area of Dentin sialoprotein (DSP) staining, which increased with calcium hydroxide treatment. Knockdown of ephrinB1-EphB2 significantly suppressed cell proliferation. Additionally, knockdown of the ephrinB1 gene caused cell migration, whereas a lack of the EphB2 gene suppressed calcium hydroxide-induced mineralization from primary pulp cells. CONCLUSIONS: EphrinB1-EphB2 interaction contributes to calcium hydroxide-induced odontogenic/osteogenic differentiation. This observation is the first finding of the mechanism of calcium hydroxide-induced odontogenic/osteogenic differentiation.
Assuntos
Hidróxido de Cálcio/farmacologia , Polpa Dentária/citologia , Efrina-B1/fisiologia , Odontogênese/fisiologia , Osteogênese/fisiologia , Receptor EphB2/fisiologia , Células-Tronco/fisiologia , Álcalis , Animais , Calcificação Fisiológica/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Polpa Dentária/efeitos dos fármacos , Dentina Secundária/efeitos dos fármacos , Efrina-B1/efeitos dos fármacos , Efrina-B1/genética , Proteínas da Matriz Extracelular/efeitos dos fármacos , Técnicas de Inativação de Genes , Concentração de Íons de Hidrogênio , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Odontogênese/efeitos dos fármacos , Osteogênese/efeitos dos fármacos , Fosfoproteínas/efeitos dos fármacos , RNA Interferente Pequeno/genética , Receptor EphB2/efeitos dos fármacos , Receptor EphB2/genética , Sialoglicoproteínas/efeitos dos fármacos , Células-Tronco/efeitos dos fármacosRESUMO
INTRODUCTION: Histological studies of immature human permanent necrotic teeth with or without apical periodontitis after revascularization have not been reported. This case report describes the histological findings of tissue formed in the canal space of an immature permanent tooth #9 with irreversible pulpitis without apical periodontitis after revascularization. METHODS: An immature human permanent tooth #9 was fractured 3.5 weeks after revascularization and could not be retained. The tooth was extracted and prepared for routine histological and immunohistochemical evaluation in order to examine the nature of tissue formed in the root canal following the revascularization procedure. RESULTS: At 3.5 weeks after revascularization, more than one half of the canal was filled with loose connective tissue similar to the pulp tissue. A layer of flattened odontoblast-like cells lined along the predentin. Layers of epithelial-like cells, similar to the Hertwig's epithelial root sheath, surrounded the root apex. No hard tissue was formed in the canal. CONCLUSIONS: Based on the histological findings in the present case, regeneration of pulp-like tissue is possible after revascularization. In this case, both the apical papilla and the Hertwig's epithelial root sheath survived in an immature permanent tooth despite irreversible pulpitis but without apical periodontitis.
