Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4HQ, UK.
Sci Rep. 2019 Aug 2;9(1):11277. doi: 10.1038/s41598-019-47653-z.
As the outer lens in the eye, the cornea needs to be strong and transparent. These properties are governed by the arrangement of the constituent collagen fibrils, but the mechanisms of how this develops in mammals is unknown. Using novel 3-dimensional scanning and conventional transmission electron microscopy, we investigated the developing mouse cornea, focusing on the invading cells, the extracellular matrix and the collagen types deposited at different stages. Unlike the well-studied chick, the mouse cornea had no acellular primary stroma. Collagen fibrils initially deposited at E13 from the presumptive corneal stromal cells, become organised into fibril bundles orthogonally arranged between cells. Extensive cell projections branched to adjacent stromal cells and interacted with the basal lamina and collagen fibrils. Types I, II and V collagen were expressed from E12 posterior to the surface ectoderm, and became widespread from E14. Type IX collagen localised to the corneal epithelium at E14. Type VII collagen, the main constituent of anchoring filaments, was localised posterior to the basal lamina. We conclude that the cells that develop the mouse cornea do not require a primary stroma for cell migration. The cells have an elaborate communication system which we hypothesise helps cells to align collagen fibrils.
作为眼睛的外透镜，角膜需要坚固且透明。这些特性由组成胶原纤维的排列方式决定，但哺乳动物中这种排列方式是如何发展的尚不清楚。本研究使用新型三维扫描和传统透射电子显微镜，研究了发育中的小鼠角膜，重点研究了入侵细胞、细胞外基质和不同阶段沉积的胶原类型。与研究充分的鸡不同，小鼠角膜没有无细胞的初级基质。胶原纤维最初在 E13 从假定的角膜基质细胞中沉积，然后在细胞之间呈正交排列的纤维束中组织化。广泛的细胞突起分支到相邻的基质细胞，并与基膜和胶原纤维相互作用。I 型、II 型和 V 型胶原从 E12 开始在表面外胚层的后部表达，并从 E14 开始广泛表达。IX 型胶原在 E14 时定位于角膜上皮。VII 型胶原是锚定纤维的主要成分，位于基膜的后部。本研究得出的结论是，发育中的小鼠角膜的细胞不需要初级基质来进行细胞迁移。这些细胞有一个精细的通讯系统，我们假设这个系统有助于细胞排列胶原纤维。
