Dual mode of TGF-β function in periodontal ligamental cell calcification

Materials and Methods: Human primary PDL cells, HPDLs and mouse PDL cell clone, MPDL22 were cultured in the calcification medium including L-ascorbic acid and β-glycelophosphate in the presence or absence of BMP-2, TGF-β and FGF-2 w/wo SB431542. Calcified nodule formation and mRNA expression of calcification related genes were examined by Alizarin staining and real-time PCR. Collagen synthesis in PDL cells was monitored by van Gieson staining and real-time PCR for Col1. Cell proliferation rate was determined by BrdU incorporation. Results: In the calcification culture, SB431542 treatment in the early period dramatically enhanced the BMP-2 dependent calcification and upregulated the expression of Runx2 and Osterix. Conversely, cell growth rate in the early period and collagen synthesis in the late period was inhibited by SB431542 treatment.

Conclusion: Treatment with SB431542 and BMP-2 accelerated the PDL cells calcification by the inhibition of endogenous TGF-β signaling in the early cytodifferentiation stage. Suppressed TGF-β dependent collagen synthesis in this period was not so affective on the totally outputs of mineralized matrix formation. We also determined the phase specific TGF-β function on PDL cells calcification. Development of LDDS for small chemical compound and growth factors might be a strong candidate for a novel periodontal regenerative therapy in the future.