International Journal of Medical Sciences

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13 December 2017

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Int J Med Sci 2015; 12(9):689-694. doi:10.7150/ijms.12883

Research Paper

Histological Evaluation of Periodontal Ligament in Response to Orthodontic Mechanical Stress in Mice

Keiko Kaneko1, Saeka Matsuda1, Rina Muraoka2, Keisuke Nakano1,3, Takami Iwasaki4, Mihoko Tomida4, Hidetsugu Tsujigiwa5, Hitoshi Nagatsuka3, Toshiyuki Kawakami1✉

1. Department of Hard Tissue Research, Matsumoto Dental University Graduate School of Oral Medicine, Shiojiri, Japan
2. Department of Orthodontics, Matsumoto Dental University School of Dentistry, Shiojiri, Japan
3. Department of Oral Pathology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
4. Department of Social Dentistry, Matsumoto Dental University School of Dentistry, Shiojiri, Japan
5. Department of Life Science, Faculty of Science, Okayama University of Science, Okayama, Japan

Abstract

The purpose of the study was to determine the cell dynamics in periodontal ligament in response to mechanical stress during orthodontic movement. Following Waldo's method, a square sheet of rubber dam was inserted in between the first and second maxillary molars in 10 ddY mice leaving the stress load for 3 hours. After 3 days and at 1 week, cell count on pressure and tension sides of the periodontal ligament was determined. Furthermore, the type of cell present after mechanical stress was identified using GFP bone marrow transplantation mouse model. Immunohistochemistry was carried out at 0 min (immediately after mechanical stress), 24 hours, 1 week, 2 weeks and 6 months. Temporal changes in the expression of GFP-positive bone marrow derived cells were examined. Moreover, double immunofluorescent staining was performed to determine the type of cell in the periodontal ligament. Cell count on the tension side tremendously increased 3 days after mechanical stress. At 1 week, spindle and round cell count increased compared to the control group. These changes were observed on both tension and pressure sides. Cell count on pressure side at 3 days (22.11+/-13.98) and at 1 week (33.23+/-11.39) was higher compared to the control group (15.26+/-8.29). On the tension side, there was a significantly increased at 3 days (35.46+/-11.85), but decreased at 1 week (29.23+/-13.89) although it is still higher compared to the control group (AD+/-SD: 10.37+/-8.69). Using GFP bone marrow transplantation mouse model, GFP positive cell count increased gradually over time in 6 months. GFP positive cells were also positive to CD31, CD68 and Runx2 suggesting that fibroblasts differentiated into osteoclasts and tissue macrophages. In conclusion, mechanical stress during orthodontic movement promoted the increase in the number of cells in the periodontal ligament on both tension and pressure sides. The increase in the number of cells in the periodontal ligament is believed to be due to the migration and cell division of undifferentiated mesenchymal cells.

Keywords: Periodontal Ligament, Orthodontic Mechanical Stress, Cell movement, Cell differentiation, Immunohistochemistry

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How to cite this article:
Kaneko K, Matsuda S, Muraoka R, Nakano K, Iwasaki T, Tomida M, Tsujigiwa H, Nagatsuka H, Kawakami T. Histological Evaluation of Periodontal Ligament in Response to Orthodontic Mechanical Stress in Mice. Int J Med Sci 2015; 12(9):689-694. doi:10.7150/ijms.12883. Available from http://www.medsci.org/v12p0689.htm