BONE MORPHOGENETIC PROTEIN-7 (OSTEOGENIC PROTEIN-1, OP-1) AND TOOTH DEVELOPMENT

Bone morphogenetic proteins (BMPs) form a family of growth factors ori ginally isolated from extracellular bone matrix that are capable of in ducing bone formation ectopically. We studied the expression, tissue l ocalization, and function of BMP-7 (OP-1) during tooth development in rodents. Patterns of BMP-7 gene expression and peptide distribution in dicated that BMP-7 was present in dental epithelium during the dental lamina, bud, and cap stages. During the bell stage, BMP-7 mRNA express ion and protein distribution shifted from dental epithelium toward the dental mesenchyme. With advancing differentiation of odontoblasts, BM P-7 protein staining in the dental papilla became restricted to the la yer of fully functional odontoblasts in the process of depositing (pre )dentin. Secretory stage ameloblasts exhibited weak immunostaining for BMP-7. A restricted pattern of staining in ameloblasts became apparen t in post-secretory stages of amelogenesis. Also, cells of the forming periodontal ligament were immunopositive. Histological analysis of to oth development in neonatal BMP-7-deficient mice did not reveal obviou s changes compared with wild-type mice. We conclude that, in developin g dental tissues, BMP-7 has distribution and expression patterns simil ar to those of other BMP members but is not an essential growth factor for tooth development, possibly because of functional redundancy with other BMP members or related growth factors.