Effects of Leukemia Inhibitory Factor on Proliferation and Odontoblastic Differentiation of Human Dental Pulp Cells

Introduction: The purpose of this study was to determine whether the leukemia inhibitory factor (LIF) is expressed in human dental tissue and exerts its effect on proliferation and odontoblastic differentiation of the dental pulp cells (DPCs). Methods: An immunohistochemical assay was used to detect the expression of LIE and leukemia inhibitory factor receptor (LIFR) in the human dental pulp. The proliferation of DPCs was examined by culturing human primary DPCs in the presence of LIE with different doses or the neutralizing antibody to LIF. Western blot was performed to assay the phosphorylation of Janus kinase 2 (Jak2) and signal transducer and activator of transcription 3 (Stat3) in the presence or absence of LIF and/or AG 490, a specific inhibitor of Jak2. The odontoblastic differentiation of DPCs was determined using the alkaline phosphatase (ALP) activity assay, quantification of bone sialoprotein (BSP) and dentin sialophosphoprotein (DSPP) gene expression, and mineralization nodule formation. Results: LIE and LIFR were present in the odontoblasts and DPCs. LIF induced proliferation of DPCs, which was inhibited by the LIE neutralizing antibody and AG 490. LIE induced phosphorylation of Jak2 and Stat3 but not in the presence of the AG490. ALP activity of DPCs, in the absence or presence of mineralization induction medium, was inhibited by LIF. Furthermore, the mineralization nodule formation and the expression of BSP and DSPP were inhibited by LIF. This inhibition on differentiation was attenuated by the AG490. Conclusions: LIE and LIFR are expressed in the human dental pulp. LIF promotes the proliferation of DPCs, and the odontoblastic differentiation is inhibited via the Jak2-Stat3 signaling pathway. (J Endod 2011;37:819-824)