2013 Volume 22 Issue 3 Pages 343-350
Numerous disorders and types of injuries require bone tissue regeneration for the repair of bone defects. Previous attempts have been made to apply bone morphogenetic protein (BMP), a bioactive growth factor, to the defect site for bone reconstruction in various animal models. However, many of these studies evaluated the efficacy of BMP using texture and soft X-ray imaging performed after the laboratory animal was euthanized. As such, any attempts to observe the induction of new bone formation over a continuous time scale within the same laboratory animal has been difficult. Accordingly, a setup in which BMP-induced ectopic bone formation is assessed over the long term has become extremely important. To date, there are no reports to verify the long-term preservation of BMP-induced bone formation at sites of repair. In this study, we performed a long-term and continuous observation of new bone formation after the addition of BMP using a new three-dimensional micro X-ray computed tomography technology, R_mCT. BMP was implanted into a gap in the fascia of the femur in a mouse, and scanning using this new technology was continued for 320 days. The following tests were performed: (1) observation using 3-dimensional construction imaging; (2) measurement of the mean ratio of new bone volume to total volume, and (3) measurement of the density of new bone formation. From these tests, we observed that BMP-induced ectopic bone persists for up to 320 days, with minimal losses in bone volume or density, unlike previously accepted notions. We also present details of the structural changes in this ectopic bone.
