Objectives: Dental pulp tissue is frequently infected or inflamed due to dental caries, trauma or cavity preparation. After pulp injury, there is an accumulation of inflammatory cells that release pro-inflammatory cytokines such as tumor necrosis factor-a (TNF-a). However, the effect of TNF-a on dental pulp cells (DPCs) is poorly understood.
Methods: DPCs were obtained from 3rd molars collected from 3 adults at Okayama University Hospital under the approved guidelines and protocol (Okayama-University Ethics Committee #418). DPCs were cultured in a-MEM, and subconfluent cultures were treated with 10 ng/ml rhTNF-a (R&D) for 2 days. Subsequently, cells were washed and passaged to remove rhTNF-a completely. The effects of this rhTNF-a pretreatment on the stem cell-like phenotype of DPCs were evaluated by colony formation assay, flow cytometry (FACS), immunofluorescence staining, measurement of the telomerase activity and multilineage differentiation experiments.
Results: rhTNF-a (0-160 ng/ml) did not affect either the proliferation or viability of DPCs. rhTNF-a pretreatment increased the gene expression of nanog more than 2 times (P<0.05, t-test) and oct4 more than 1.5 times (P<0.001, t-test), and enhanced the percentage of stem cell maker antigens, such as STRO-1, SSEA4 and CD146. The colony-forming units and telomerase activity of DPCs were also significantly increased by pretreatment with rhTNF-a. Moreover, rhTNF-a pretreated-DPCs differentiated more easily into osteo/odontogenic, adipogenic and chondrogenic lineages.
Conclusion: Pretreatment of the dental pulp cells with rhTNF-a reinforced their stem cell-like phenotype in vitro.