Methods: The premolars of beagle dogs were extracted. After 3 months healing, β-TCP was implanted into cylindrical artificial bone defects (4.5 x 8 mm). After 4, 7 and 14 days, all specimens were taken out, and total RNA was isolated from bone tissues using FastPrep and RNeasy Kit. Gene expression profiles and signaling pathway were examined using microarray coupled with IPA. PCR was used to confirm mRNA levels.
Results: It was found that β-TCP implantation led to a two-fold change in 3,409 genes on day 4, 3,956 genes on day 7, and 6,899 genes on day 14.Among them, transforming growth factor (TGF)-β2, Smad4 and plasminogen activator inhibitor-1 (PAI-1) were up-regulated on days 4 and 7, bone morphogenetic protein2 (BMP2) and TGF-β1 were up-regulated on days 4 and 14, which involved in TGF-β/BMP signaling pathway from IPA. The mRNA levels of these genes were successfully confirmed by RT- and real-time PCR.
Conclusion: TGF-β superfamily of growth factors, including the TGF-βs, activins, and BMPs, provide cells with a broad spectrum of regulatory signals through the intracellular Smad pathway and play crucial roles in ossification. The results suggest that β-TCP may effectively provide increased signals through TGF-β/BMP signaling to induce mesenchymal cells differentiation into osteogenic cells capable of producing bone.