Genipin, a cross-linking agent, promotes odontogenic differentiation of human dental pulp cells

Introduction: The aim of this study was to investigate the effects of genipin, a natural collagen cross-linking agent, on odontogenic differentiation of human dental pulp cells (hDPCs) because the mechanical properties of collagen allow it to serve as a scaffold for engineering of pulp-dentin complex. Furthermore, the role of extracellular signal-regulated kinase (ERK) was investigated as a mediator of the differentiation. Methods: The odontogenic differentiation was analyzed by alkaline phosphatase activity, real time-polymerase chain reaction, Western blotting, and alizarin red S staining. The morphologic features of hDPCs cultured in genipintreated collagen were evaluated by scanning electron microscopy. For the assessment of mechanical properties of collagen treated with genipin, the surface roughness and compressive strength were measured. Results: Alkaline phosphatase activity, the expression of odontogenic markers, and mineralized nodule formation increased in the genipin-treated group. Genipin also activated ERK, and treatment with ERK inhibitor blocked the expression of the markers. The cells cultured in genipin-treated collagen spread across the substrate and attached in close proximity to one another. The proliferation and differentiation of hDPCs cultured in genipin-treated collagen were facilitated. The mechanical properties of collagen, such as surface roughness and compressive strength, were increased by treatment with genipin. Conclusions: Our results show that genipin promotes odontogenic differentiation of hDPCs via the ERK signaling pathway. Furthermore, the enhanced mechanical properties of the collagen scaffold induced by genipin may play important roles in cell fate. Consequently, the application of genipin might be a new strategy for dentin-pulp complex regeneration.