Impact of TNFR1 pro-inflammatory receptor ablation in amelogenesis and dental enamel biomineralization in mice

Immune response has been speculated as a player in dental enamel defects. Therefore, the aim of this study was to investigate the effects of ablation of the TNFR1 gene, which encodes the receptor-1 of the pleiotropic protein tumor necrosis factor-α, in amelogenesis and enamel biomineralization. Six male knockout mice for the TNFR1 receptor and six wild-type C57BL/6 mice were used for the study. The lower incisors were used for visual photographic analysis, computerized microtomography, scanning electron microscopy (SEM), surface microhardness evaluation and mineral component analysis by energy dispersive X-ray. The presence and synthesis of MMP-20, Runx2, COX-2 and ameloblastin were investigated using immunohistochemistry and in situ zymography. Data was analyzed using Student t test. No visual changes were found in the incisors and there was no difference in mineral density between the groups. Nonetheless, SEM showed a difference in the conformation of the enamel prisms of incisors extracted from TNFR1 ^-/- animals, as well as a lower Ca content and enamel surface microhardness. Regarding the signaling and molecules involved in amelogenesis, there was a higher expression of MMP-20, COX-2, Runx2, and ameloblastin in TNFR1 ^-/- animals. The absence of the TNFR1 receptor has an impact on signaling for the formation of tooth enamel, resulting in lower surface hardness and lower calcium composition.