Proceedings of The Physiological Society

Physiology 2012 (Edinburgh) (2012) Proc Physiol Soc 27, PC140

Poster Communications

Migration of the transplanted bone marrow-derived cells into periodontal ligaments due to orthodontic mechanical stress

M. Tomida1, H. Tsujigiwa2, K. Nakano3, R. Muraoka4, T. Nakamura1, N. Asanuma1, H. Nagatsuka2, T. Kawakami3

1. Physiology, Matsumoto Dental University, Shiojiri, Japan. 2. Oral Pathology and Medicine, Okayama University, okayama, Japan. 3. Hard Tissue Pathology Unit, Matsumoto Dental University, Siojiri, Japan. 4. Orthodontics, Matsumoto Dental University, Siojiri, Japan.

Bone marrow-derived cells (BMC) have abilities to migrate and differentiate into teeth and also periodontal ligament fibroblast cells. We examined the effect of orthodontic mechanical stress on the transplanted BMC migration into periodontal tissues using green fluorescence protein (GFP) transgenic mice. BMC from GFP transgenic mice were transplanted into 8 week-old female C57BL/6 immunocompromised recipient mice (n=10), which had undergone 10 Gy of lethal whole-body irradiation. After successful transplantation, 5 mice under inhalation anesthesia using isoflurane (Isoflu: Dainippon Sumitomo Pharma Co., Osaka, Japan) and gas-air mixture (4.0% concentration) received orthodontic mechanical stress by Wald method 5 times in 5 weeks. Five mice were used as the control without receiving orthodontic mechanical stress. After that, the regional tissues were removed and fixed in formalin fixative. Paraffin-embedded sections were immunohistochemically analyzed using Dako Envision + Kit-K4006 (Dako, Glostrup, Denmark) and a primary anti-GFP-polyclonal rabbit antibody (#598; 1/500; MBL, Nagoya, Japan). For semiquantitative evaluation of immunohistochemical staining, the following procedures were performed. First, immunohistochemical images of the fixed magnification from the periodontal tissues were prepared and pixel density was counted for each image. Then typical immunohistochemically positive staining portion was defined as positive area. The pixel number of the positive area in the periodontal tissue was compared with the previously calculated total pixel number of the periodontal tissue and the ratio of these numbers was obtained. 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, such as osteoclasts and macrophages, and furthermore the positive cells gathered adjacent blood vessels. The data suggest that GFP-positive BMC migrate into periodontal tissues and differentiate into periodontal tissue component-cells. In the experimental group, numerous GFP-positive cells appeared in the periodontal tissues which received intermittent stimulation of orthodontic mechanical stress, but few GFP-positive cells were seen in the control specimens. The pixel ratio number in the experimental group was 5.77 ± 3.24 % (mean ± SD), while in the control group, it was 0.71±0.45 % (mean ± S.D.); thus the ratio in experimental group was significantly greater than that of the control group (Mann-Whitney U test: p<0.001). These results suggest that orthodontic mechanical stress induces migration of transplanted BMC and their differentiation into periodontal tissue cells.

Where applicable, experiments conform with Society ethical requirements