Iloprost up-regulates Inflammatory Cytokines in HDPCs under Static Mechanical Forces

Objectives: Dental pulp tissues subjected to excessive or prolonged occlusal forces may develop inflammation by the increase of pro-inflammatory cytokines released by dental pulp cells. Human Dental Pulp cells (HDPCs) could increase the expression of IL-1 and IL-6 under 2 hours of mechanical pressure application. Iloprost; a prostacyclin analogue, could promote vascular endothelial growth factor (VEGF) and Collagen I (Col1) gene expression in HDPCs and also inhibit some pro-inflammatory mediators resulting in anti-inflammatory property in some specific tissues. The aim of this study was to determine the effect of iloprost to HDPCs on the regulation of inflammation-related gene expression under static mechanical forces
Methods: HDPCs were pre-treated with/without iloprost for one hour and then received 2 g/cm³ static mechanical pressure for two hours. The applied force, using computerized mechanical force generated apparatus, could be visualized in real-time. Samples were collected and isolated for PCR. The datas were statistically analyzed by using student T-test and ANOVA.
Results: The loading forces at 2 g/cm3 at 2 hours did not affect cell death confirmed by MTT. The results showed that iloprost further increased the expression of VEGF and Col1 mRNA expression under 2 hours compared to non-loading group and control groups in HDPCs. Interestingly, IL-1β and IL-6 mRNA expression were also up-regulated in mechanical/iloprost group, while ALP was not affected by iloprost or mechanical loading.
Conclusions: Our results indicated that iloprost increased the expression of proliferative markers, such as VEGF and Col1, under mechanical pressure. Surprisingly, IL-1β and IL-6 genes, which are pro-inflammatory markers, were also up-regulated. These results may suggest that iloprost influenced the expression of both pro and anti-inflammatory pathway in dental pulp. The understanding of the responses of HDPCs to iloprost could be applied for clinical treatment, especially in traumatic tooth or heavy force- applied tooth.