Ide Y, Nakahara T, Nasu M, Ishikawa H
Department of Developmental and Regenerative Dentistry, School of Life Dentistry at Tokyo, The Nippon Dental University, Tokyo, Japan.
Oral Dis. 2015 Mar;21(2):232-9. doi: 10.1111/odi.12253. Epub 2014 May 21.
To investigate the mechanisms that cause damage to root formation as a result of irradiation to the mouse head, morphological changes in molar dental roots and cell dynamics in Hertwig's epithelial root sheath (HERS), and surrounding mesenchymal tissue were examined.
To perform the experiments, 5-day-old C57BL/6 mice were randomly divided into three groups: the control group (0 Gy) and irradiated groups (10 and 20 Gy). Micro-CT analysis, HE staining, immunohistochemistry analysis, and TUNEL assay were then performed.
Roots in irradiated mice were dose-dependently shorter than those of control mice. Cells located outside the root dentin, with abnormal morphology in irradiated mice, were positive for an odontoblast marker. HERS fragmentation occurred earlier in irradiated mice than in control mice, and HERS was trapped by the calcified apical tissue. A dose-dependent reduction in the number of proliferating cells within the apical dental pulp and periapical periodontal ligament surrounding HERS was observed in irradiated mice. Apoptotic cells in the dental pulp and periodontal ligament surrounding HERS were hardly seen.
These results indicate that the early disappearance of HERS and the proliferative suppression of the surrounding mesenchymal cells, which was induced by irradiation, caused dental root malformation.
研究小鼠头部受照射导致牙根形成受损的机制，检测磨牙牙根的形态变化以及赫特维希上皮根鞘（HERS）及其周围间充质组织中的细胞动态。
为进行实验，将5日龄的C57BL/6小鼠随机分为三组：对照组（0 Gy）和照射组（10 Gy和20 Gy）。随后进行显微CT分析、苏木精-伊红（HE）染色、免疫组织化学分析和末端脱氧核苷酸转移酶介导的缺口末端标记（TUNEL）检测。
受照射小鼠的牙根比对照小鼠的牙根短，且呈剂量依赖性。在受照射小鼠中，位于牙根牙本质外、形态异常的细胞对成牙本质细胞标记物呈阳性。HERS断裂在受照射小鼠中比对照小鼠更早发生，并且HERS被钙化的根尖组织包绕。在受照射小鼠中，观察到HERS周围的根尖牙髓和根尖牙周膜内增殖细胞数量呈剂量依赖性减少。在HERS周围的牙髓和牙周膜中几乎未见凋亡细胞。
这些结果表明，照射诱导的HERS早期消失以及周围间充质细胞的增殖抑制导致了牙根畸形。
