Effect of Wnt6 on human dental papilla cells in vitro

The Wnt signaling pathway plays an important role in tissue development by acting on proliferation, differentiation, and cell fate decisions. Because the role of Wnt6 in tooth development was still unknown, the purpose of this study was to investigate the role of Wnt6 in tooth morphogenesis and dental tissue mineralization by elucidating its effect on human dental papilla cells (hDPCs) in vitro.

Human dental papilla cells were enzymatically separated from tooth germs. Recombinant adenovirus encoding full-length Wnt6 cDNA was constructed to overexpress Wnt6, and the biologic effects of Wnt6 on hDPCs were investigated. Wnt6-transduced changes in hDPC proliferation were examined by means of a 5-bromodeoxyuridine (BrdU) incorporation assay and cell cycle analysis. Wnt6-transduced changes in hDPC differentiation were investigated by evaluating alkaline phosphatase (ALPase) activity, by a mineralization assay, and analysis of mineralization-related gene expression including ALP, type I collagen (Col I), osteonectin (ON), osteopontin (OPN), bone sialoprotein (BSP), and dentin matrix protein-1 (DMP-1).

Wnt6 overexpression had no significant effect on the proliferation of hDPCs by BrdU incorporation assay and flow cytometric analysis. Wnt6 enhanced differentiation of hDPCs into functional odontoblast-like cells with up-regulated activity of ALPase and the expression of mineralization-related genes such as ALP, Col I, ON, OPN, BSP, and DMP-1. Wnt6 overexpression also promoted the mineralization of hDPCs.

Our findings verified that Wnt6 plays an important role in tooth development by promoting hDPC differentiation, without significant effects on hDPC proliferation.