Objectives: Bone morphogenetic proteins (BMPs) are considered to have the potential to initiate mineralized tissue formation. The purpose of this study was to investigate the effects of BMP-7, a potent bone-inducing factor, on mineralized tissue associated genes of cementoblasts, a cell type associated with tooth root formation.

Methods: Osteocalcin promoter driven SV40 transgenic mice were used to obtain immortalized cementoblasts (OCCM.30). Cells were treated with DMEM containing 1) 5% FBS (Fetal Bovine Serum) + ascorbic acid (AA, 50 mg/ml), 2) 5% FBS+ BMP-7 (50 ng/ml)+AA. After 72 hours, total RNA was isolated from cementoblasts and cDNA was synthesized from 1.0 mg total RNA. Real-time quantitative RT-PCR experiments were performed for mineralized tissue markers including bone sialoprotein (BSP), osteocalcin (OCN), osteopontin (OPN), matrix gla protein (MGP), and runt related transcription factor-2 (Runx2). GAPDH served as a housekeeping/reference gene for normalization. In vitro mineralization was assayed using von Kossa staining.

Results: In cells exposed to BMP-7, OCN transcripts increased almost 4-fold, while a mild increase was detected in BSP and OPN mRNA expression. Conversely, a slight decrease was noted in both MGP and Runx2 mRNA expression compared to control. Furthermore, BMP-7 treatment markedly stimulated cementoblast-mediated biomineralization in vitro when compared to untreated cells at day 8.

Conclusion: BMP-7 was demonstrated to increase expression of markers of cementoblasts and mineralized tissue, namely OCN, BSP, and OPN, as well as to stimulate mineralization by cementoblasts. MGP, a negative regulator of mineralization was decreased by BMP-7. These studies suggest the potential application of BMP-7 in therapies aimed at regenerating periodontal tissues lost as a consequence of disease (Selcuk University/BAP).

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