Corneal Graft Biology, Engineering and Imaging Laboratory, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France.
Stem Cells. 2012 Nov;30(11):2523-34. doi: 10.1002/stem.1212.
The control of corneal transparency depends on the integrity of its endothelial monolayer, which is considered nonregenerative in adult humans. In pathological situations, endothelial cell (EC) loss, not offset by mitosis, can lead to irreversible corneal edema and blindness. However, the hypothesis of a slow, clinically insufficient regeneration starting from the corneal periphery remains debatable. The authors have re-evaluated the microanatomy of the endothelium in order to identify structures likely to support this homeostasis model. Whole endothelia of 88 human corneas (not stored, and stored in organ culture) with mean donor age of 80 ± 12 years were analyzed using an original flat-mounting technique. In 61% of corneas, cells located at the extreme periphery (last 200 μm of the endothelium) were organized in small clusters with two to three cell layers around Hassall-Henle bodies. In 68% of corneas, peripheral ECs formed centripetal rows 830 ± 295 μm long, with Descemet membrane furrows visible by scanning electron microscopy. EC density was significantly higher in zones with cell rows. When immunostained, ECs in the extreme periphery exhibited lesser differentiation (ZO-1, Actin, Na/K ATPase, CoxIV) than ECs in the center of the cornea but preferentially expressed stem cell markers (Nestin, Telomerase, and occasionally breast cancer resistance protein) and, in rare cases, the proliferation marker Ki67. Stored corneas had fewer cell clusters but more Ki67-positive ECs. We identified a novel anatomic organization in the periphery of the human corneal endothelium, suggesting a continuous slow centripetal migration, throughout life, of ECs from specific niches.
角膜透明性的控制取决于其内皮单层的完整性，而成年人的内皮细胞被认为是不可再生的。在病理情况下，内皮细胞（EC）的丢失，而不是有丝分裂的补偿，可导致不可逆的角膜水肿和失明。然而，从角膜周边开始缓慢、临床不足的再生假说仍然存在争议。作者重新评估了内皮细胞的微观解剖结构，以确定可能支持这种内稳态模型的结构。使用原创的平面安装技术，对 88 个人眼角膜（未保存和在器官培养中保存）的整个内皮进行了分析，平均供体年龄为 80±12 岁。在 61%的角膜中，位于极周边（内皮的最后 200μm）的细胞组织成小簇，围绕 Hassall-Henle 小体有两到三层细胞。在 68%的角膜中，周边 EC 形成了长 830±295μm 的向心行，扫描电子显微镜下可见到 Descemet 膜陷窝。EC 密度在行区域显著更高。在极端周边进行免疫染色时，EC 表现出较少的分化（ZO-1、肌动蛋白、Na/K ATPase、CoxIV），而角膜中心的 EC 分化程度更高，但优先表达干细胞标志物（Nestin、端粒酶，偶尔还有乳腺癌耐药蛋白），在极少数情况下，增殖标志物 Ki67 也呈阳性。保存的眼角膜中细胞簇较少，但 Ki67 阳性的 EC 较多。我们在人眼角膜内皮的周边区域发现了一种新的解剖组织，表明在整个生命过程中，EC 从特定的小生境中持续缓慢向中心迁移。
