Objectives: Osteoadherin (OSAD) is a small leucine-rich proteoglycan that was recently identified in bone and dentin and suspected to play a role in the organization and the mineralization of collagenous matrices. In order to elucidate mechanisms regulating OSAD synthesis in human dental tissues, we studied the effects of TGFb 1 on pulp cells both in cultures of tooth thick slices containing mature odontoblasts and in explant cultures giving rise to early secretory odontoblasts or pulpal fibroblasts.

Methods: Immunohistochemical staining was performed on tooth slices with antibodies against molecules involved in TGFb 1 signaling and OSAD and semi-quantitative RT-PCR analysis of OSAD mRNAs was achieved from explant cultures.

Results: Tb RI, Tb RII, SMAD2, SMAD3, SMAD4 were detected in pulp cells in vivo and maintained after culture with TGFb 1. A strong staining for OSAD was observed in odontoblasts in vivo, but sub-odontoblastic cells and central fibroblasts were more weakly stained. After three days of culture of tooth slices in the presence of TGFb 1, OSAD synthesis was increased in mature odontoblasts close to the growth factor-delivery system. Semi-quantitative RT-PCR analysis achieved from explant culture mRNAs revealed an over-expression of the OSAD gene in both early secretory odontoblasts and pulpal fibroblasts stimulated by TGFb 1.

Conclusions: Taken together, our results suggest that TGFb 1 increased osteoadherin expression in pulpal fibroblasts, early secretory and mature odontoblasts. In this way, this growth factor could regulate the organization and the mineralization of the dentin extracellular matrix and thus promote dental pulp repair in vivo.

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