Effects of transforming growth factor-β1 on odontoblastic differentiation in dental papilla cells is determined by IPO7 expression level

Abstract

Transforming growth factor β1 (TGF-β1) is one of the broad-spectrum growth-promoting factors that participate in tooth development. The influence of TGF-β1 on the odontoblastic differentiation is still controvercy. Mouse primary dental papilla cells (mDPCs) as well as an immortalized mouse dental papilla cell line (mDPC6Ts) were treated with exogenous TGF-β1 during odontoblastic differentiation. RT-qPCR, Western blot, alizarin red staining and ALP staining were carried out to investigate the influence of TGF-β1 on odontoblastic differentiation. IPO7, important for SMAD complex translocation was also detected in mDPCs and mDPC6Ts in response to TGF-β1. After silencing IPO7 by transfection, the translocation process of P-SMAD2 was investigated by nuclear and cytoplasmic extraction as well as co-immunoprecipitation assay. The odontogenic markers, mineralization and IPO7 expression were significantly up-regulated in TGF-β1-treated mDPCs while down-regulated in mDPC6Ts. The total level of P-SMAD2 was not influenced by IPO7 in mDPCs, however, IPO7 could bind to P-SMAD2 and affect the nuclear-cytoplasm-shuttling of P-SMAD2. Our data demonstrated that TGF-β1 plays opposite roles in odontoblast differentiation in mDPCs and immortalized mouse dental papilla cell line (mDPC6Ts), which is determined by IPO7.