**6. Conclusions**

In general, remodeling of the periodontal ligament (PDL) tissue is occurring in all times. Thus, in the above sentences, the word "remodeling" was used in the section "Maintenance of Periodontal Ligament Homeostasis." Our experimental data suggest that the remodeling of periodontal ligament with cell acceleration at the furcation area in this experimental model has recovered using the cells in situ and the bone marrow-derived cells (BMCs). BMC migration into the PDL tissues using BMC transplantation model was examined. BMCs have abilities of cell migration and differentiation into tissues/organs in the body. The immunohistochemistry revealed that GFP-positive cells were detected in the periodontal tissues, both in the experimental and control specimens. These results suggest that orthodontic mechanical stress accelerates transplanted BMC migration into the PDL tissues. GFP-positive cells were also positive to CD31, CD68, and Runx2 suggesting that fibroblasts differentiated into osteoclasts and tissue macrophages. In this way, Notch signaling involvement was considered in our tentative examinations.
