TEMPORAL CHANGES IN EXPRESSION OF TRANSFORMING GROWTH-FACTOR-BETA SUPERFAMILY MEMBERS AND THEIR RECEPTORS DURING BOVINE PREODONTOBLAST DIFFERENTIATION IN-VITRO

Transforming growth factor (TGF)-beta superfamily members and their re ceptors play a part in the differentiation of pulp cells into odontobl asts during reparative dentinogenesis. Bovine primary pulp-cell cultur e has been used as an in vitro model for proliferation and differentia tion of pulp cells into preodontoblasts. To explore the molecular casc ade 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-beta superfamily members : TGF-beta(1), namely bone morphogenetic protein (BMP)-4, BMP-7, activ in-beta(A) and activin-beta(B), 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 (T beta R-I), BMPR-II and T beta R-II, durin g differentiation of pulp cells into preodontoblasts in bovine adult p ulp-cell culture. TGF-beta(1) and BMP-4 mRNAs were expressed from day 14 when matrix formation increased. BMP-7 mRNA was expressed only on d ay 28 when osteocalcin appeared. ALK-2 mRNA was increased from the beg inning of the culture. ALK-3 and ALK-5 mRNAs first decreased on day 14 and increased again on day 21. T beta R-II and BMPR-II mRNAs were alm ost constant. These results suggest that the differentiation of pulp c ells into preodontoblasts may be regulated by changes in the temporall y coordinated expression pattern of TGF-beta superfamily members and t heir receptors, including up-regulation of transcription of TGF-beta(1 ), BMP-4, BMP-7, ALK-2, ALK-3 and ALK-5. (C) 1997 Elsevier Science Ltd .