Oka Kyoko, Morokuma Masakazu, Imanaka-Yoshida Kyoko, Sawa Yoshihiko, Isokawa Keitaro, Honda Masaki J
Department of Anatomy, Nihon University School of Dentistry, Tokyo, Japan.
Eur J Oral Sci. 2012 Dec;120(6):484-94. doi: 10.1111/eos.12003. Epub 2012 Oct 16.
Fragments of Hertwig's epithelial root sheath persist in the periodontal ligament (PDL) in small clusters known as epithelial rests of Malassez (ERM). It is generally agreed that ERM are maintained as a quiescent and exclusively dental epithelial cluster in PDL. However, we speculate that homeostasis and cellular turnover underlies cluster maintenance. We also hypothesize that the fate of ERM clusters - diminishing or remaining - might be regulated via the presence or absence of epithelial stem cells therein. Histological analysis of aging mouse molar PDL showed that ERM clusters gradually increase in size with increasing age. Immunocytochemistry and cell culture revealed that ERM clusters contained Ki67-positive cells and were able to expand when brought in culture. The TdT-mediated biotin-dUTP nick-end labeling (TUNEL) procedure also detected signs of apoptosis. Finally, we identified putative epithelial stem cells in the clusters by 5-bromo-2'-deoxyuridine (BrdU) pulse-chase experiments and immunohistochemistry, using the stem-cell marker leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5). The results suggest that ERM clusters are maintained in the PDL, via cellular turnover, throughout life.
赫特维希上皮根鞘的碎片以小簇的形式存在于牙周韧带（PDL）中，这些小簇被称为马拉瑟上皮剩余（ERM）。人们普遍认为，ERM在PDL中作为静止且仅含牙齿上皮的簇得以维持。然而，我们推测细胞稳态和细胞更新是簇维持的基础。我们还假设，ERM簇的命运——缩小或留存——可能通过其中上皮干细胞的有无来调节。对老龄小鼠磨牙PDL的组织学分析表明，ERM簇的大小会随着年龄增长而逐渐增大。免疫细胞化学和细胞培养显示，ERM簇含有Ki67阳性细胞，并且在培养时能够扩增。TdT介导的生物素-dUTP缺口末端标记（TUNEL）法也检测到了凋亡迹象。最后，我们通过5-溴-2'-脱氧尿苷（BrdU）脉冲追踪实验和免疫组织化学，使用干细胞标志物富含亮氨酸重复序列的G蛋白偶联受体5（Lgr5），在簇中鉴定出了假定的上皮干细胞。结果表明，ERM簇在整个生命过程中通过细胞更新在PDL中得以维持。
