Rib resection and healing in the mouse: a new model of bone repair

Bone is one of the very few tissues in our body that has the capacity for repair without leaving a scar. However, there are instances when bone repair fails. In injuries or surgical situations where a large portion of bone is missing, healing can be completely compromised. Anecdotal reports in humans have suggested that the rib may be one of the only long bones in the body that has the capacity to repair large defects. The aim of this project is to study the healing of a segmental defect in murine ribs to determine if healing occurs with the help of innate factors. Surgeries were performed on adult CD-1 mice where a piece of the vertebral rib was removed leaving the periosteum intact. Control surgeries were also performed where both the rib and the surrounding periosteum were resected. Animals were sacrificed at various time points and the rib cages were dissected to analyze the healed region. We found that when the periosteum was left behind, the resected region would be completely filled in within 1-2 months. The healed bone had restored the original morphology with only some minor irregularities. In the control surgeries there was no sign of regeneration except modestly at the cut ends. Based on our studies, we found that the mouse model can be effectively used to study large defects. Furthermore, we believe that the periosteum plays a key role in the healing process and may serve as a repository for stem cells that can mediate the repair. Eventually our hope is that this research will give a better insight in developing ways to stimulate large defect repair in other locations of the body.