Osteogenic Profile of Mesenchymal Cell Populations Contributing to Alveolar Bone Formation

Teeth develop within the surrounding periodontal tissues, involving the alveolar bone, periodontal ligament and cementum. The alveolar bone originates through the process of intramembranous ossification involving mesenchymal cells from the tooth germ. As most available data are related to endochondral ossification, we examined the molecular background of alveolar bone development. We investigated the osteogenic profile of mesenchymal cells dissected from mouse mandible slices at the stage of early alveolar bone formation. Relative monitoring of gene expression was undertaken using PCR Arrays; this included the profiles of 84 genes associated with osteogenesis. To examine the tooth-bone interface, stages with detectable changes in bone remodelling during development (E13.0, E14.0 and E15.0) were chosen and compared with each other. These results showed a statistically significant increase in the expression of the genes Fgf3, Ctsk, Icam-1, Mmp9, Itga3 and Tuft1, and of a wide range of collagens (Col1a2, Col3a1, Col7a1, Col12a1, Col14a1). Decreased expression was detected in the case of Col2a1, Sox9, Smad2 and Vegfb. To confirm these changes in gene expression, immunofluorescence analyses of Mmp9 and Sox9 proteins were performed in situ. Our research has identified several candidate genes that may be crucial for the initiation of alveolar bone formation and is the basis for further functional studies.