Corneal Development: Different Cells from a Common Progenitor.

Development of the vertebrate cornea is a multistep process that involves cellular interactions between various ectodermal-derived tissues. Bilateral interactions between the neural ectoderm-derived optic vesicles and the cranial ectoderm give rise to the presumptive corneal epithelium and other epithelia of the ocular surface. Interactions between the neural tube and the adjacent ectoderm give rise to the neural crest cells, a highly migratory and multipotent cell population. Neural crest cells migrate between the lens and presumptive corneal epithelium to form the corneal endothelium and the stromal keratocytes. The sensory nerves that abundantly innervate the corneal stroma and epithelium originate from the neural crest- and ectodermal placode-derived trigeminal ganglion. Concomitant with corneal innervation is the formation of the limbal vascular plexus and the establishment of corneal avascularity. This review summarizes historical and current research to provide an overview of the genesis of the cellular layers of the cornea, corneal innervation, and avascularity.