New Platform for Assessing Biocompatibility of Dental Monomers: HPDPCs

Objectives: A 3D dental pulp model entailing immortalized cells was previously developed for testing cytotoxicity of leachable resin monomers. To make this model clinically relevant, the use of primary human cells isolated from dental pulp would be required. The objective of this study was to assess whether primary cells can be utilized in a 3D pulp-extracellular matrix (ECM) model for cytotoxicity evaluations.
Methods: The pluripotency markers (CD105, Sox2 and Oct4) of human primary dental pulp cells (HPDPCs) obtained from two donors were determined by immunocytochemistry. The effect of various concentrations of triethyleneglycol dimethacrylate (TEGDMA) on cell stress mechanism was evaluated by smRNA-FISH assay (DDIT4 expression). Structural alterations and thickness of the constructs was assessed in different stages of development, pre-mature and mature cultures, by confocal laser scanning microscopy and image analysis program ImageJ. Expression of pluripotency markers was analyzed by immunocytochemistry. Each experiment was run in triplicate.
Results: In the presence of 0.5 mM TEGDMA, DDIT4 was already expressed and interactions between cell multilayers were reduced. At 1.5 mM TEGMA intra-structural cell interactions deteriorated further. The thicknesses of the 3D HDPCs cultures from both donors [(60.4±7.33)μm to (41.6±3.51)μm and (82.9±13.3)μm to (48.4±0.36)μm, respectively] decreased significantly (p≤0.05) in 0.5 mM TEGDMA-challenged systems compared to no-TEGDMA controls. Immortalized human dental pulp cell line (3D hTERT) demonstrated similar structural alterations as the HPDPCs and drastic decrease in thickness [(140.4±32.91)μm to (22.93±8.71)μm). Mature primary cultures supplemented with TEGDMA responded in the same manner as the premature ones [(118.3±22.30)μm to (58.4±11.20)μm, respectively]. Cultures continued to express the self-renewal markers after exposure to 1.5 mM TEGDMA.
Conclusions: 3D HPDPCs-ECM platforms, demonstrated strong potential for testing biocompatibility of residual monomers in cultures from individual donors, and may be utilized in the future to test biocompatibility in different age, sex and population groups.