[Aim] We examined the transplanted bone marrow-derived cell migration into the periodont ligament tissues. Mesenchymal cells in the bone marrow have abilities of cell migration and differentiation into periodontal cells. We examined the cytological remodeling dynamism of the periodontal ligament tissue due to orthodontic mechanical stress, using mouse experimental model. [Methods] After the approving by Animal Experimental Control Committee of the University, Bone marrow cells from GFP transgenic mice were transplanted into 8 week-old female C57BL/6 mice, which had undergone 10 Gly of lethal whole-body irradiation for the purpose of inactive all bone marrow/white cells of in the recipient mice. After successful transplantation, the mice received orthodontic mechanical stress using the Waldo method; and the mice were compared as control without receiving orthodontic mechanical stress. Paraffin-sections were immunohistochemically (IHC), fluorescence IHC and TRAP staining techniques and analyzed using a primary anti-GFP-polyclonal rabbit antibody. Semi-quantitative evaluation of IHC staining was prepared and pixel density was counted for each image. Then typical IHC positive staining part was defined as positive area. The pixel number of positive area in the periodontal tissue was compared with the previously calculated total pixel number of the periodontal tissue and the ratio was obtained. The examination results were analysed using Mann-Whitney U test. [Results and Discussion] We examined the transplanted bone marrow-derived cell migration into periodontal tissues. The IHC revealed that GFP-positive cells were detected in the periodontal tissues, both in the experimental and control specimens. The GFP-positive cells histopathologically differentiated into some cell types. The fluorescence IHC and TRAP staining techniques demonstrated these cells were detected as osteoclasts and macrophages. Furthermore, GFP-positive cells gathered adjacent blood vessels. The data suggest that GFP-positive bone marrow-derived cell migration into periodontal ligament tissues and differentiate periodontal tissues component-cells. The GFP-positive cells histopathologically differentiated into some cell types. The fluorescence IHC and TRAP staining techniques demonstrated these cells were detected as osteoclasts and macrophages. Furthermore, GFP-positive cells gathered adjacent blood vessels. The data suggest that GFP-positive bone marrow-derived cell migrate into periodontal tissues and differentiate periodontal component-cells. As a results of the examination group specimens and control group, the ratio of pixel number of GFP-positive cells in the examination group showed 5.77 ± 3.24 % (mean ± SD); and that in the control group, 0.71±0.45 % (mean ± SD). The examination group was greater than that of control group (p<0.001). [Conclusions] These results suggest that orthodontic mechanical stress induces bone marrow cell migration and differentiation into periodontal ligament tissue component cells.