Expression and effect of tumor necrosis factor-α in human dental follicle cells in vitro

Yingchun Bi, DDS, PhD, Zhu Lin, DDS, PhD, Zuolin Jin, DDS, PhD, Hong Qian DDS, PhD, Xuepeng Chen, DDS, PhD, Yongkuan Zhang, PhD, and Xueying Han, DDS

Department of Orthodontics, College of Stomatology, The Fourth Military Medical University, Xi’an,
P. R. China

Purpose: To investigate (1) the effect of interleukin-1α (IL-1α) on tumor necrosis factor-α (TNF-α) expression, (2) the induced effect of TNF-α on the expression of monocyte chemoattractant protein-1 (MCP-1), and (3) the corresponding signal transduction pathway in the human dental follicle cells (HDFCs).
Materials and Methods: Primary HDFCs were cultured. The fifth passaged HDFCs were incubated with IL-1α. Then examined the expression of TNF-α by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assays (ELISA). The expression of MCP-1 was examined after HDFCs incubatied with TNF-α by ELISA and RT-PCR. Furthermore, the induction of MCP-1 mRNA expression by TNF-α was inhibited by SB203580, SP600125, and PD98059.
Results: The results of RT-PCR and ELISA revealed that IL-1α increases the TNF-α gene expression and secretion significantly at concentration of 25-100 ng/mL (p<0.05). Furthermore, TNF-α enhances MCP-1 gene expression and secretion at concentration of 10-100 ng/mL (p<0.05) and the action is inhibited by SP600125, the special inhibitor of c-Jun N-terminal kinase (JNK).
Conclusion: IL-1α induces expression of TNF-α by HDFCs. One of the actions of TNF-α in tooth eruption may be that it enhances MCP-1 gene expression and secretion and these events require JNK activity, which recruits monocytes into the dental follicle, where these cells are fused to form osteoclasts to resorb alveolar bone for the formation of an eruption pathway. (Int Chin J Dent 2007; 7: 35-42.)

Key Words: dental follicle, interleukin-1α, monocyte chemoattractant protein-1, tumor necrosis factor-α.