The Effect of Harmine on Dental Pulp Stem Cells Differentiation Into Neural Cells in Two-Dimensional and Three-Dimensional Cell Cultures

Background: As the repair capacity of the nervous system is low, stem cell therapy is a trend for replacement therapy. Dental pulp stem cells (DPSCs) have the potential to differentiate into many tissues, such as neurons. Harmine (7-methoxy-1methyl-9H-pyrido[3,4-b] indole) is an alkaloidal component of medicinal plants with a long history in traditional medicine. Alginate is a biocompatible hydrogel widely used as a biomaterial base in various scaffolds. Objectives: This study investigated whether harmine and encapsulation of cells in alginate hydrogel could improve DPSCs differentiation into neural cells. Methods: DPSCs were cultured under standard stem cell culture conditions, then encapsulated in alginate hydrogel, and treated with differentiation medium with and without harmine. After 14 days, cell proliferation and differentiation were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, real-time polymerase chain reaction (RT-PCR), and flow cytometry. Results: Harmine (5 and 10 μM) significantly increased the proliferation and viability of DPSCs compared to the control group in both two-dimensional and three-dimensional culture systems (P < 0.05). The expression levels of three neural cell markers (nestin, microtubule-associated protein [MAP-2], and β-tubulin III) in DPSCs-derived neural cells cultured in two-dimensional and three-dimensional culture systems were significantly increased in harmine-treated two-dimensional and three-dimensional culture systems compared to the control group (P < 0.05). Conclusions: Either harmine or alginate hydrogel had an accelerating effect on DPSCs differentiation into neural cells. Harmine also increased the proliferation of the cells.