Involvement of M1/M2 Macrophage Polarization in Reparative Dentin Formation

Abstract

In cases in which dental pulp tissue is accidentally exposed, direct pulp capping is often performed to induce reparative dentin formation. Although macrophages are essential for the inflammatory response and tissue repair, the emergence pattern and the role of macrophages in dental pulp tissue have not been clarified. Here, we investigated the emergence of M1/M2 macrophages in dental pulp tissue after a direct pulp capping and the effects of M2 macrophages on odontoblastic differentiation of the dental pulp stem cell (DPSC) clones. The emergence of macrophages in dental pulp tissue was investigated using a rat direct pulp capping model. Alizarin Red S staining and quantitative RT-PCR was performed to examine the effect of M2 macrophages on the mineralization and odontoblastic differentiation of DPSC clones. Immunohistochemical staining revealed that M1 macrophages were detected in dental pulp tissue after treatment and increased in number at three days after treatment. However, M2 macrophages gradually increased in number in dental pulp tissue after treatment, with the highest level recorded at seven days post-operation. Additionally, conditioned medium from M2 macrophages induced odontoblast-like differentiation of DPSC clones. These results suggest that macrophages play a role in the inflammatory response and reparative dentin formation after dental pulp exposure.

Sensory nerves, but not sympathetic nerves, promote reparative dentine formation after dentine injury via CGRP‐mediated angiogenesis: An in vivo study

“…Additionally, the involvement of CGRP‐labelled nerves in the modulation of inflammation, particularly in M2 macrophage polarization, and its potential role in tertiary dentine formation remains uncertain. In light of the findings that CGRP modulates the transformation of macrophages to the M2 phenotype through the PI3K/AKT signalling pathway in keratitis (Yuan et al., 2022) and M2 macrophages promote odontoblast‐like differentiation of dental pulp stem cells (Kadowaki et al., 2022), it is imperative to expose the pulp chamber to induce invasion of bacteria and provoke an inflammatory response in the future study to ensure the role of CGRP in regulating macrophage polarization in dental pulp.…”