The calcium dynamics of human dental pulp stem cells stimulated with tricalcium silicate-based cements determine their differentiation and mineralization outcome

Calcium (Ca(2+)) signalling plays an indispensable role in dental pulp and dentin regeneration, but the Ca(2+) responses of human dental pulp stem cells (hDPSCs) stimulated with tricalcium silicate-based (TCS-based) dental biomaterials remains largely unexplored. The objective of the present study was to identify and correlate extracellular Ca(2+) concentration, intracellular Ca(2+) dynamics, pH, cytotoxicity, gene expression and mineralization ability of human dental pulp stem cells (hDPSCs) stimulated with two different TCS-based biomaterials: Biodentine and ProRoot white MTA. The hDPSCs were exposed to the biomaterials, brought in contact with the overlaying medium, with subsequent measurements of extracellular Ca(2+) and pH, and intracellular Ca(2+) changes. Messenger RNA expression (BGLAP, TGF-β, MMP1 and BMP2), cytotoxicity (MTT and TUNEL) and mineralization potential (Alizarin red and Von Kossa staining) were then evaluated. Biodentine released significantly more Ca(2+) in the α-MEM medium than ProRoot WMTA but this had no cytotoxic impact on hDPSCs. The larger Biodentine-linked Ca(2+) release resulted in altered intracellular Ca(2+) dynamics, which attained a higher maximum amplitude, faster rise time and increased area under the curve of the Ca(2+) changes compared to ProRoot WMTA. Experiments with intracellular Ca(2+) chelation, demonstrated that the biomaterial-triggered Ca(2+) dynamics affected stem cell-related gene expression, cellular differentiation and mineralization potential. In conclusion, biomaterial-specific Ca(2+) dynamics in hDPSCs determine differentiation and mineralization outcomes, with increased Ca(2+) dynamics enhancing mineralization.