Interleukin-6 decreases FGF-2 expression of human periodontal ligament cells

Objectives:

Interleukin-6 (IL-6) is a major mediator of host defense against tissue injury and bacterial infection. IL-6 is significantly increased in pathologically inflammatory conditions caused by periodontal diseases. It is generally accepted that periodontal ligaments play important roles for periodontal tissue regeneration and they are influenced by IL-6 in the process of its regeneratio. So, to clarify the cytologic characterization of periodontal ligament cells, we investigated the effect of IL-6 against human periodontal ligament (HPL) cells using fibroblast growth factor (FGF)-2 as a cell-proliferating marker.

Methods:

HPL cells were obtained from explant cultures of periodontal ligaments in the third molars extracted from three patients who gave informed consent. They were cultured to confluence in a 60 mm plastic culture dish with Dulbecco's modified Eagle's medium (D-MEM) supplemented with 10% fetal bovine serum, 100 units/ml penicillin, 100 µg/ml streptomycin, and 3 µg/ml amphotericin B under the condition of 5% CO₂ incubation at 37°C. The HPL cells in cultures at the 4th-8th passages were harvested and seeded at a density of 3x10⁴ cells/well with D-MEM. After 4 weeks cultivation, the HPL cells were added with IL-6 at a concentration of 0, 0.01, 0.1, and 1 ng/ml for 72h. After the completion of harvesting, these samples were examined with a real-time polymerase chain reaction (PCR) and by immunohistochemical staining.

Results:

From both observations with a real-time PCR method and by immunohistochemical staining, the FGF-2 mRNA expressions in the group of IL-6 (0.01~1ng/ml) application were decreased and down-regulated at every concentration examined in comparison to that in the control group.

Conclusions:

This result suggests that IL-6 can inhibit the function of cell proliferation in periodontal ligament cells through some pathological mechanism.