In vitro study of the effects of iloprost-thermosensitive gel on human dental pulp stem cells

Aim: Iloprost, a prostacyclin (PGI₂) analogue, promotes angiogenesis and cellular proliferation, suggesting its potential as a regenerative agent in dental pulp therapy. However, its liquid form and short half-life pose challenges for clinical application and sustained delivery. This study aimed to design a thermosensitive, injectable hydrogel to enable controlled Iloprost release and to evaluate the cytotoxicity and VEGF gene expression effects of both the hydrogel and Iloprost on dental pulp stem cells (DPSCs) in vitro. Materials and Methods: QbD approach was employed for hydrogel formulation, utilizing Modde® software to establish a Design of Experiments (DoE). A hydrogel was prepared using 18% Poloxamer 407 and 5% Poloxamer 188 by cold method. Iloprost was incorporated at two concentrations (10⁻⁶ M and 2×10⁻⁶ M). The formulations were characterized for adhesion, cohesion, gelation temperature, and viscosity. DPSCs were exposed to the formulations, and cytotoxicity was assessed using the MTT assay, while VEGF mRNA expression was analyzed by RT-qPCR. Results:Characterization results indicated that the hydrogel formulations were suitable for DPSC application. Poloxamer-only groups showed cytotoxicity in the MTT assay, whereas Iloprost groups did not exhibit cytotoxic effects at 24 hours. RT-qPCR analysis revealed a significant increase in VEGF expression at 24 and 72 hours in the 10⁻⁶ M Iloprost group compared to the control. Conclusion: The undiluted hydrogel formulation showed cytotoxicity, indicating the need for further studies with diluted forms. However, the absence of cytotoxicity and the upregulation of VEGF expression in Iloprost-treated groups support its potential as a therapeutic agent for dentin-pulp regeneration. Keywords: Poloxamer 407, Poloxamer 188, Iloprost, MTT, RT-PCR, Quality by Design