Ordered Fluorapatite Stimulates DPSC Mineralization and Related Osteogenesis Profile Analysis

Our previous studies have shown good biocompatibility of fluorapitite (FA) crystal surfaces in supporting long-term growth and functional cell-matrix interaction of the human dental pulp stem cells (DPSCs). Objectives: To investigate whether this enamel-like FA surface can support the differentiation and mineralization of human dental pulp stem cells. Methods: Ordered (OR) and disordered (DS) FA surfaces were synthesized via a hydrothermal method. DPSCs were subcultured in MEM with 10% FBS on OR, DS and etched stainless steel (SSE) surfaces for 28 days. Scanning electron microscope and human pathway focused osteogenesis PCR Array were performed on the experimental specimens after 28 days with/without mineralization supplement (MS). In vitro tetracycline staining was administered to label the newly formed mineral nodules after 28 days with/without MS. These fixed and ground specimens were then observed under fluorescence microscope. Results: After mineralization induction, obvious mineral nodule formation was seen on both FA surfaces with denser mineral deposition on OR surfaces. The osteogenesis PCR array showed up regulation of multiple pro-osteogenesis molecules including runt-related transcription factor 2 (RUNX2), collagen, type X, alpha 1 (COL10A1), dentin matrix protein1 (DMP1), phosphate-regulating endopeptidase homolog, Xlinked (PHEX), etc., of the cells grown on FA surfaces, especially on OR compared to that on SSE surfaces. In addition, though identifiable tetracycline staining was shown on specimens from both FA surfaces, the OR surface stimulated scattered mineralized bone-like tissue integration within crystal layer with stronger fluorescence intensity compared to that of DS and SSE surfaces. Conclusions: Ordered, enamel-like FA substrate provided a favorable extracellular matrix microenvironment for the differentiation and mineralization of human DPSCs which appears promising in applying these FA substrate in future clinical fields such as in the creation of the enamel/dentin junction and in facilitating the pulp repair process.