Department of Oral Health Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
Development. 2010 Nov;137(21):3545-9. doi: 10.1242/dev.052415. Epub 2010 Sep 28.
Most dentate vertebrates, including humans, replace their teeth and yet the process is poorly understood. Here, we investigate whether dental epithelial stem cells exist in a polyphyodont species, the leopard gecko (Eublepharis macularius). Since the gecko dental epithelium lacks a histologically distinct site for stem cells analogous to the mammalian hair follicle bulge, we performed a pulse-chase experiment on juvenile geckos to identify label-retaining cells (LRCs). We detected LRCs exclusively on the lingual side of the dental lamina, which exhibits low proliferation rates and is not involved in tooth morphogenesis. Lingual LRCs were organized into pockets of high density close to the successional lamina. A subset of the LRCs expresses Lgr5 and other genes that are markers of adult stem cells in mammals. Also similar to mammalian stem cells, the LRCs appear to proliferate in response to gain of function of the canonical Wnt pathway. We suggest that the LRCs in the lingual dental lamina represent a population of stem cells, the immediate descendents of which form the successional lamina and, ultimately, the replacement teeth in the gecko. Furthermore, their location on the non-tooth-forming side of the dental lamina implies that dental stem cells are sequestered from signals that might otherwise induce them to differentiate.
大多数有齿脊椎动物，包括人类，都会换牙，但这一过程知之甚少。在这里，我们研究了多齿动物——豹纹守宫（Eublepharis macularius）中是否存在牙上皮干细胞。由于守宫的牙上皮缺乏类似于哺乳动物毛囊隆突的组织学上明显的干细胞部位，我们对幼年守宫进行了脉冲追踪实验，以鉴定标记保留细胞（LRCs）。我们仅在牙板的舌侧检测到 LRCs，该区域增殖率较低，不参与牙齿形态发生。舌侧 LRCs 组织成靠近接替层的高密度口袋。LRCs 的一部分表达 Lgr5 和其他在哺乳动物中作为成体干细胞标记的基因。与哺乳动物干细胞相似，LRCs 似乎在经典 Wnt 通路功能获得时增殖。我们认为，舌侧牙板中的 LRCs 代表了干细胞群体，其直接后代形成接替层，并最终形成守宫的替换牙。此外，它们位于牙板的非牙齿形成侧，这意味着牙干细胞被隔离在可能导致其分化的信号之外。
