Development of a novel frontal bone defect mouse model for evaluation of osteogenesis efficiency

The skull defect model is the existing representative osteogenesis model. The skull defect model involves monitoring osteogenesis patterns at the site of a skull defect, which has the advantages that identical defects can be induced across individual experimental animals and the results can be quantitatively evaluated. However, it can damage the cerebrum because it requires a complex surgery performed on the parietal bone. This study aims to develop a new osteogenesis model that compensates for the weak points of the existing model. Male 8-week-old imprinting control region mice were put under inhalational anesthesia, and the surgery area was disinfected with 70% ethanol prior to the creation of a 5-mm incision along the sagittal line between the glabella with a pair of scissors. The incised area was opened and, after we checked the positions of the inferior cerebral vein and the sagittal suture, a 21-gauge needle was used to make two symmetrical holes with respect to the sagittal suture 3 mm below the inferior cerebral vein and 2 mm on either side of the sagittal suture. After images were obtained using micro-computed tomography, the degree of osteogenesis was quantitatively analyzed. In addition, mRNA extracted from the site of the defect confirmed a significant increase in mRNA levels of collagen 1a, alkaline phosphatase, bone sialoprotein, osteocalcin, and Runx2, known markers for osteoblasts. The promotion of osteogenesis could be observed at the site of the defect, by histological analysis.