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The aim of this study was to investigate the effect of prolonged release of iloprost, a prostacyclin analog, on angiogenesis and dental pulp healing in a rat model of mechanical pulp exposure. The profile of iloprost release from poly (lactic-co-glycolic) acid (PLGA) microspheres was evaluated, and expression of vascular endothelial growth factor (VEGF) mRNA was determined. The molars of rats were subjected to mechanical pulp exposure and 5 different forms of treatment: Ca(OH) 2 , PLGA (blank), iloprost, and iloprost/PLGA. Blood flow was determined at 0, 3, and 7 days using laser Doppler flowmetry. After 30 days, the tooth specimens were collected, and subjected to micro-CT and immunohistological analysis. The results showed that iloprost release from the microspheres was prolonged for 4 days, and that the treatment increased tooth blood flow for up to 7 days. At 30 days, an increase of mineralized tissue formation and dentin bridge formation was observed in the iloprost and iloprost/PLGA microsphere groups. VEGF expression was significantly increased in the iloprost/PLGA microsphere group relative to the other groups. In conclusion, this PLGA microsphere iloprost delivery system significantly increased dental pulp blood flow in a prolonged manner and increased tertiary dentin formation in this rat pulp injury model. Prolonged prostacyclin release could be a potentially useful approach for regeneration of dental pulp.

Iloprost increases the expression of angiogenic factors and increases dental pulp flow, suggesting the potential of iloprost as a biomolecule to promote dental pulp regeneration. However, the methods to clinically deliver iloprost into the limited root canal area of a tooth and control its release are limited. The purpose of this study was to prepare a thermo-sensitive injectable hydrogel from pluronic F127 (PF127) for delivering iloprost to induce dental pulp regeneration. The PF127 hydrogels were fabricated using thermal crosslinking. The maximum cumulative release iloprost from the hydrogel at 25°C was 60%. No significant cytotoxicity or morphological changes were observed in human dental pulp cells (HDPCs) at any of the PF127 gel concentrations of the iloprost carrier. Moreover, the effect of the 20%wt PF127 gels containing iloprost on the expression of VEGF in HDPCs increased vascular endothelial growth factor (VEGF) gene expression at 72 h. The thermo-sensitive hydrogel at 20%wt PF127 containing iloprost could be used for prolonged drug release in dental applications.

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Iloprost's anti‐inflammatory effects on human dental pulp stem cells (HDPCs) are currently unknown. We hypothesized that iloprost could downregulate the expression of inflammatory‐related genes and protein in an inflamed HDPC in vitro model. To induce inflammation, the HDPCs were treated with a cocktail of interleukin‐1 beta, interferon‐gamma, and tumour necrosis alpha, at a ratio of 1:10:100. Iloprost (10−6 M) was then added or not to the cultures. Interleukin‐6 (IL‐6) and interleukin‐12 (IL‐12) mRNA expression were assessed by real‐time polymerase chain reaction. IL‐6 protein expression was assessed by enzyme‐linked immunosorbent assay. The results were analysed using one‐way ANOVA or the Kruskal–Wallis test. The cytokine cocktail induced more robust IL‐6 expression than LPS treatment. Iloprost slightly, yet significantly, downregulated IL‐6 and IL‐12 mRNA expression. These findings suggest that iloprost might be used as a beneficial component in vital pulp therapy.