Temporal changes in expression of transforming growth factor-β superfamily members and their receptors during bovine preodontoblast differentiation in vitro

Transforming growth factor (TGF)-β superfamily members and their receptors play a part in the differentiation of pulp cells into odontoblasts during reparative dentinogenesis. Bovine primary pulp-cell culture has been used as an in vitro model for proliferation and differentiation of pulp cells into preodontoblasts. To explore the molecular cascade of odontoblast differentiation, Northern blot analyses and reverse transcriptase polymerase chain reaction were here used to investigate the expression patterns of the genes for TGF-β superfamily members: TGF-β1 namely bone morphogenetic protein (BMP)-4, BMP-7, activin-βA and activin-βB and their type I and type II receptors, namely activin receptor-like kinase (ALK)-2 (ActR-I), ALK-3 (BMPR-IA), ALK-4 (ActR-IB), ALK-5 (TβR-I), BMPR-II and TβR-II, during differentiation of pulp cells into preodontoblasts in bovine adult pulp-cell culture. TGF-β1 and BMP-4 mRNAs were expressed from day 14 when matrix formation increased. BMP-7 mRNA was expressed only on day 28 when osteocalcin appeared. ALK-2 mRNA was increased from the bi;ginning of the culture. ALK-3 and ALK-5 mRNAs first decreased on day 14 and increased again on day 21. T βR-II and BMPR-11 mRNAs were almost constant. These results suggest that the differentiation of pulp cells into preodontoblasts may be regulated by changes in the temporally coordinated expression pattern of TGF-β superfamily members and their receptors, including up-regulation of transcription of TGF-β1 BMP-4, BMP-7, ALK-2, ALK-3 and ALK-5.