Lipopolysaccharide upregulates the proliferation, migration, and odontoblastic differentiation of NG2+ cells from human dental pulp in vitro

NG2(+) cells have been proven to differentiate into odontoblasts in vivo, and their contribution to odontoblasts is significantly increased, especially after tooth injury. However, their characteristics in vitro, especially under an inflammatory environment, are still not fully understood. Therefore, this study aimed to explore their proliferation, migration, and odontoblastic differentiation ability after treatment with lipopolysaccharide (LPS) in vitro. In our study, NG2(+) cells were isolated from the human dental pulp by magnetic-activated cell sorting, and these isolated cells were proven to be NG2(+) by immunostaining. When compared with human dental pulp cells (hDPCs), the NG2(+) cells showed no significant differences in cell migration with or without LPS incubation, but their proliferative ability was weaker. When treated with LPS, NG2(+) cells expressed elevated levels of pro-inflammatory cytokines including interleukin-1 beta (IL-1 beta), IL-6, IL-8, and tumor necrosis factor-alpha, and among these, the expression of IL-1 beta and IL-6 were higher than that of hDPCs. Their multipotent differentiation potential was confirmed by the induction of odontoblastic and adipogenic differentiation, and LPS increased their odontoblastic differentiation capacity. In the odontoblastic differentiation process, Wnt5a, BMP2, and BMP7 mRNA were increased, while the canonical Wnt-related genes were decreased. In conclusion, the LPS stimulation promotes the migration, proliferative, and odontoblastic differentiation ability of NG2(+) cells from the human dental pulp in vitro, and bone morphogenetic protein and the noncanonical Wnt pathway may be involved in their odontoblastic differentiation. These results indicated their special roles in tooth injury repair and potential application in pulp regeneration.