Morphogenesis of rabbit corneal endothelium

Abstract

We studied ultrastructurally the development of rabbit corneal endothelium from the 13th day of gestation to 3 days after birth. Precursor corneal endothelial cells, stromal cells, and a vascular network migrate in close association with each other between the developing corneal and lens epithelia. During development, newly deposited extracellular fibrous matrices separate the prospective endothelium from the capillaries and corneal stroma. The extracellular matrix between the apical endothelial surface and the vascular network loses its fibrous appearance early in development. Simultaneously, randomly organized fibrils are deposited on the basal endothelial surface facing the stroma. These fibrils, gradually obscured by the deposition of a nonfibrous component, eventually become part of Descemet's membrane. Early in development, prospective endothelial cells cannot be distinguished morphologically from the overlying corneal stromal cells. Morphologic differentiation of the endothelial cell is characterized by the formation of sinuous lateral borders that interdigitate with those of adjacent cells to form a continuous single-cell layer of tissue. The basal endothelial membrane forms a pitted surface, distinguishing it from the apical cell membrane. Intercellular junctions between lateral membranes, a cilium projecting into the anterior chamber, and deposition of Descemet's membrane on the basal endothelial surface contribute to the polarization of the endothelium. Throughout most of corneal development the vascular pupillary membrane maintains a close association with the apical surface of the differentiating endothelium. We conclude that fetal corneal endothelium develops within a complex extracellular matrix environment and in proximity to the underlying vascular network. These structures play an important role in the morphogenesis of corneal endothelium.

The keratocyte: Corneal stromal cell with variable repair phenotypes

“…This is followed by two waves of neural crest cell migration: the first wave of mesenchymal cells forms the endothelial cell layer, and the second wave invades the primary stroma and forms the corneal keratocyte population (Hay, 1979). In contrast to the chick, other species, such as rodents, exhibit only a single influx of mesenchymal cells, which contributes to both corneal stromal and endothelial cells (Cintron, Covington, & Kublin, 1983).…”

Corneal development associated with eyelid opening

“…For example, in reptiles, birds, and primates, including humans, two waves are observed -first, endothelial cells then keratocytes. However, in rodents, cats, rabbits, and cattle, a single migration of cells, resulting in both cell types, is observed (Cintron et al, 1983). In the chick, the epithelial cells secrete a collagenous matrix (termed the primary stroma) prior to the influx of neural crest cells (Hay, 1979).…”

The integrin needle in the stromal haystack: emerging role in corneal physiology and pathology

“…This is unexpected, considering that the keratocytes are the cells mainly responsible for the production of stromal extracellular matrix (ECM) (Cintron et al 1983;Haustein 1983) and probably are mainly responsible for the unique arrangement and assembly of the matrix. A theme of importance that has not seen the limelight, mostly due to absence of in vivo studies, is the role of mechanical communication of keratocytes with their extracellular environment in maintaining corneal structural integrity.…”