Synthetic Clay-based Hypoxia Mimetic Hydrogel for Pulp Regeneration: The Impact on Cell Activity and Release Kinetics Based on Dental Pulp-derived Cells In Vitro.

INTRODUCTION: Thixotropic synthetic clays have been successfully used for tissue engineering in regenerative medicine. The impact of these clays on the dental pulp, in particular in combination with hypoxia-based approaches using hypoxia mimetic agents (HMAs), is unknown. Our aim was to reveal the response of dental pulp-derived cells (DPCs) to a synthetic clay-based hydrogel and evaluate the release of HMAs. METHODS: Using resazurin-based toxicity assays, live-dead staining, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide staining, the viability of human DPCs seeded onto a synthetic clay-based hydrogel of 5%-0.15% as well as onto the hydrogels loaded with the HMAs dimethyloxalylglycine (DMOG), desferrioxamine, L-mimosine, and CoCl2 was evaluated. Furthermore, supernatant of the hydrogels loaded with HMAs were generated. Vascular endothelial growth factor (VEGF) production of DPCs in response to the supernatant was measured to reveal the cellular response to the HMAs. RESULTS: We found that the synthetic clay-based hydrogel did not impair the viability of DPCs. Cell monolayer and cell cluster formations were observed on the hydrogel. No significant increase of VEGF levels was observed in the supernatant when DPCs were cultured on hydrogels loaded with HMAs. Supernatant of DMOG-loaded hydrogels stimulated VEGF production in DPCs in the first hour, whereas the effect of desferrioxamine, L-mimosine, and CoCl2 did not reach a level of significance. CONCLUSIONS: The synthetic clay-based hydrogel represents a promising biomaterial that does not induce prominent toxic effects in DPCs. It can be loaded with DMOG to induce hypoxia mimetic activity. Overall, we provided first insights into the impact of synthetic clays on DPCs for tissue engineering purposes in regenerative endodontics.