[P2-2-08] Analysis of cementum incremental lines formation in radiation-exposed Japanese macaque teeth in the Fukushima Daiichi Nuclear Power Plant accident
Keywords:セメント質成長線、福島第一原発事故、ニホンザル
The purpose of this study is to analyze whether the formation mechanism of incremental lines in cementum in the teeth of Japanese macaques exposed by the Fukushima Daiichi Nuclear Power Plant accident was affected by radioactivity. Forty Japanese macaque tooth samples (9 in the non-exposed group and 31 in the exposed group) were used in Fukumoto's study (2023). The concentration of radioactive cesium in the body was measured by gamma-ray spectrum analysis using a germanium semiconductor detector using the thigh muscle. The samples used in this study were approved by the Tohoku University Animal Ethics Committee (2016 Kado-043-1). The tooth sample was fixed in 10% formalin solution, demineralized, sectioned to a thickness of about 4 µm, and stained with hematoxylin and eosin (HE) according to the standard method. Cementum incremental lines were observed in the HE staining specimens with light microscopy and analyzed using the image analysis software WinRoof 2018 (MITANI). The age distribution was 2 to 25 years old, as determined from the analysis of the cementum incremental lines. In juveniles, the incremental lines of the exposed group were unclear compared to that of the non-exposed group. In adults exposed to high concentrations of radioactive cesium, the incremental lines were locally irregularly spaced and obscured. The tissue structure was disturbed by a mixture of cellular and acellular cementum. It was suggested that the radiation exposure may affect cementoblasts' incremental lines formation mechanism. Thanks are given to Specially Appointed Professor Dr. M. Fukumoto and Lecturer Dr. M. Suzuki of Tohoku University for providing the research materials and radioactive cesium concentration data.