Occlusal stimuli regulate interleukin-1 beta and FGF-2 expression in rat periodontal ligament

While many studies reported the structural changes in the periodontal ligament (PDL) under hypofunctional conditions, the associations of cytokine growth factors are still unclear. They are known to take part in inflammation, and may affect the biological properties of hypofunctional tooth. To investigate the hypofunctional PDL and the recovery from this condition, we focused on interleukin-1 beta (IL-1beta) and basic fibroblast growth factor (FGF-2). Male Wistar rats were divided into occluded, non-occluded, and recovery groups. An anterior bite plate was used to eliminate the occlusal contact of molars in the non-occluded group, and was then removed for the recovery group. After occlusal stimuli were eliminated for 7 and 14 days, and after 3 and 7 days of recovery from 7 days in the hypofunctional condition, the PDLs of the lower first molars were investigated immunohistochemically. The lack of occlusal stimuli caused atrophic changes in the PDL with the upregulation of IL-1beta and decreased expression of FGF-2, while decreased IL-1beta and enhanced FGF-2 expression were observed in the recovery process. These results suggest that occlusal stimuli regulate IL-1beta and FGF-2 expression, and the nature of this regulation may differ from that in the healing process of an inflammatory reaction.