Regulate Pulp Cells Activities by TGF-beta1, BMP-2 and Extracellular Matrix

Objectives: In the pulpo-dentin complex, transforming growth factor-beta1 (TGF-beta1) and bone morphogenetic proteins (BMPs) regulate pulp tissue repair and dentinogenesis during development and response to external irritation. The purpose of this study is to evaluate the effect of BMP-2 and TGF-beta 1 on dental pulp cells.

Methods: Primary human dental pulp cells were cultured in culture plates with/without coating with collagen or fibronectin . They were exposed to various concentrations of BMP-2 or TGF-beta1 for some periods. Viable cell numbers were estimated by MTT assay. Cell differentiation and mineralization was evaluated by alkaline phosphatase (ALP) and Alizarin red staining. Changes in mRNA expression were determined by reverse-transcriptase polymerase chain reaction.

Results: BMP-2 (50-250 ng/ml) or TGF-beta1 (1-10 ng/ml) by itself unexpectedly down-regulated the proliferation and ALP activity of dental pulp cells cultured in both regular medium and mineralization medium (with vitamin C and beta- glycerophosphate). Pyrrolidine thiocarbamate (PDTC, a NF-kB inhibitor) and dexamethasone stimulated the ALP activity and mineralization. Culture of pulp cells on collagen- and FN-coated plates declined the growth rate and ALP activity. However, culture of pulp cells on collagen and FN stimulated the integrin alphav, alpha3, beta1, beta3 mRNA expression. TGF-beta 1 also induced integrin beta1, connective tissue growth factor (CTGF), alpha-smooth muscle actin but down-regulated Runx-2, integrin alpha1 and beta3 mRNA expression in dental pulp cells, similarly these events are regulated by BMP-2. Moreover, SB431542 (an ALK5/Smad2/3 inhibitor) prevented the TGF-beta1-induced decline of ALP activity in pulp cells.

Conclusion: TGF-beta1 and BMP-2 may affect the proliferation and differentiation of dental pulp cells at specific stages concomitant with other extracellular matrix. These events are associated with changes in integrins, CTGF, smooth muscle actin,Runx-2 and possibly mediated by ALK-5/Smad 2/3 signaling. (Supported by National Science Council, Taiwan)