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 LIF 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 LIF 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: LIF and LIFR were present in the odontoblasts and DPCs. LIF induced proliferation of DPCs, which was inhibited by the LIF neutralizing antibody and AG 490. LIF 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: LIF 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.

Roles of bone scintigraphy and resonance frequency analysis in evaluating osseointegration of endosseous implant.

The purpose of this study is to analyze the roles of two non-invasive techniques, bone scintigraphy and resonance frequency analysis (RFA), in the osseointegration assessment. Sixty implants with sandblasted/acid-etched (SA) or machined (MA) surface were placed into the distal femur condyles of 30 rabbits. At 1, 2, 4, 6, 8, and 12 weeks postsurgery, they were subjected to bone scintigraphy, digital radiographic examination, histological and histomorphometric analysis. RFA was performed on each implant both at the time of implant placement and animal sacrifice. The results showed that variation of Tc-99m-MDP uptake (bone scintigraphy value) coincided with that of new bone formation activity and accumulation of osteoblasts. Bone scintigraphy was more sensitive to the change of peri-implant bone than the digital radiographic examination. But it did not correlate with histomorphometric data and failed to detect the difference between SA and MA implants. It was found that RFA value increased with the bone-to-implant contact during the healing phase and correlated with the histomorphometric data. Moreover, RFA distinguished between the SA and MA implants. It is concluded, therefore, that bone scintigraphy may be a dynamic method on peri-implant bone healing, while RFA may be a reliable biomechanical technique that can monitor the osseointegration at macro level. We propose that the combination of these non-destructive techniques may facilitate the identification of the nature of osseointegration.