Evidence for expansion-based temporal BMP4/NOGGIN interactions in specifying periodontium morphogenesis.

Dental follicle cells in the periodontium are known to have the ability to differentiate into fibroblasts, cementoblasts, and osteoblasts during mouse periodontal development. From embryonic day 14 (E14) to postnatal day 11 (PN11), histological observations showed dramatic alterations in the relative width of the periodontal ligament (PDL)-forming region between the alveolar bone-forming and tooth root-forming area. At PN2, the width of the PDL-forming region showed a minimum, but with a higher expression of NOGGIN and proliferation cell nuclear antigen than the other regions. At PN11, the relative width of the PDL-forming region had expanded. Transplantation of individual regions of the developing tooth germ under the kidney renal capsule showed that dental follicle cells at E14 possessed the potential to develop into mineralized tissue after 3 weeks. These results suggested that the recovery of PDL width at PN11 may have resulted from cell proliferation and molecular interactions between osteogenic factors and their antagonists, such as interactions between bone morphogenetic protein 4 (BMP4) and NOGGIN, simlilar to those observed in suture, limb, and somite formation. To confirm the molecular interaction between BMP4 and NOGGIN, NOGGIN-protein bead implantation onto cultures was employed in vitro. This study thus indicates that harmonious interactions between NOGGIN and BMP in PDL-forming cells, which show higher cell proliferation than neighboring cells, might be important for proper periodontium development.