Differences in the developmental origins of the periosteum may influence bone healing.

BACKGROUND AND OBJECTIVE: The jaw bone, unlike most other bones, is derived from neural crest stem cells, so we hypothesized that it may have different characteristics to bones from other parts of the body, especially in the nature of its periosteum. The periosteum exhibits osteogenic potential and has received considerable attention as a grafting material for the repair of bone and joint defects. MATERIAL AND METHODS: Gene expression profiles of jaw bone and periosteum were evaluated by DNA microarray and real-time polymerase chain reaction. Furthermore, we perforated an area 2 mm in diameter on mouse frontal and parietal bones. Bone regeneration of these calvarial defects was evaluated using microcomputed tomography and histological analysis. RESULTS: The DNA microarray data revealed close homology between the gene expression profiles within the ilium and femur. The gene expression of Wnt-1, SOX10, nestin, and musashi-1 were significantly higher in the jaw bone than in other locations. Microcomputed tomography and histological analysis revealed that the jaw bone had superior bone regenerative abilities than other bones. CONCLUSION: Jaw bone periosteum exhibits a unique gene expression profile that is associated with neural crest cells and has a positive influence on bone regeneration when used as a graft material to repair bone defects. A full investigation of the biological and mechanical properties of jaw bone as an alternative graft material for jaw reconstructive surgery is recommended.

Soft-diet feeding after weaning affects behavior in mice: Potential increase in vulnerability to mental disorders.

Mastication is one of the most important oral functions, and the period during which mastication is acquired overlaps with the term of rapid development and maturation of the neural systems. In particular, the acquisition period after weaning is related to the potential onset of mental disorders. However, the roles of mastication during this period for brain development remain largely unknown. Therefore, we used a series of standard behavioral analyses, assessment of hippocampal cell proliferation, and the expression of brain-derived neurotrophic factor (BDNF), TrkB, and Akt1 in the hippocampus and frontal cortex of mice to investigate the effects of post-weaning mastication on brain function. We fed 21-day-old C57BL6/J male mice either a hard or a soft diet for 4weeks and conducted a series of standard behavioral tests from 7weeks of age. Further, histological analysis with bromodeoxyuridine was performed to compare hippocampal cell proliferation at 7 and 14weeks of age. Real-time polymerase chain reaction was performed to compare BDNF, TrkB, and Akt1 expression in the hippocampus and frontal cortex of 14-week-old mice. Compared to mice fed a hard diet (HDM), soft-diet mice (SDM) showed behavioral impairments, including decreased home cage activity, increased open field test activity, and deficits in prepulse inhibition. These results were similar to those observed in mouse models of schizophrenia. However, no effects were observed on anxiety-like behaviors or memory/learning tests. Compared to HDM, SDM showed significantly decreased hippocampal cell proliferation and hippocampal BDNF and Akt1 gene expression at 14weeks of age. A soft diet after weaning may have resulted in histological and molecular changes in the hippocampus and influenced outcomes of behavioral tests related to mental disorders. Our findings suggest that soft-diet feeding after weaning may affect both physical and mental development of mice, and may increase vulnerability to mental disorders.