Stem Cell Activity in the Developing Human Cornea

Abstract

The adult cornea harbors stem cells (SCs) in its periphery, in a niche known as the limbus. Over the past 2 decades there has been substantial research into these adult corneal SCs, their limbal niche, and their therapeutic applications. However, few studies have investigated how this niche and its SCs develop in humans. To better characterize this development, human fetal corneas from 8.5-to 22-weeks'-gestation (n 5 173), neonatal (n 5 2), and adult (n 5 10) specimens were obtained. Histological and immunohistochemical assessments were conducted to determine embryological changes and expression of developmental and SC-related genes. Fresh fetal corneas were explanted to propagate corneal progenitors and cells characterized using reverse transcription-polymerase chain reaction, immunohistochemistry, flow cytometry, and colony-forming assays. A novel ''ridge-like'' structure was identified, circumscribing the fetal cornea, which we hypothesize represents the rudimentary SC niche. Immunohistochemistry disclosed ''stem-like'' cells across the cornea, becoming confined to this ridge with increasing gestational age. In addition, for the first time, pure longterm cultures of fetal corneal epithelium, which displayed phenotypical and functional properties similar to those of adult limbal SCs, were established. Optimization of culture techniques and purification of this SC population will allow for further investigation of their proliferative ability, with potential research and clinical applications. This study expands our understanding of limbal niche development and opens new avenues for investigation. STEM

Zebrabow: multispectral cell labeling for cell tracing and lineage analysis in zebrafish

“…In the mammalian cornea, epithelial cells with strong proliferative capacity and stem cell-like properties are initially distributed across the entire cornea (Chung et al, 1992;Collinson et al, 2002;Davies et al, 2009). As the embryo develops, corneal stem cells become restricted to the peripheral edge of the cornea, the limbus (Davies and Di Girolamo, 2010).…”

Limbal stem cells: Central concepts of corneal epithelial homeostasis

“…This is somewhat peculiar in evolutionary sense especially when the directly adjacent conjunctiva is maintained in the same way as any other epithelia [134] . In fetal eyes, adult LSC markers are found in the basal layer across the cornea [135,136] and it is unknown how the markers become segregated in the limbus during development. Investigation of limbal organogenesis has raised a possibility that the limbal papillary structures are mere developmental remnants.…”

“…Investigation of limbal organogenesis has raised a possibility that the limbal papillary structures are mere developmental remnants. The limbus does not develop until eyelids open and the ocular surface is exposed to amniotic fluid [135,136] . The papillary structures of the limbus do not form until post-natal life [137] .…”

Reconstruction of Functional Ocular Surface by Acellular Porcine Cornea Matrix Scaffold and Limbal Stem Cells Derived from Human Embryonic Stem Cells

“…Several recent studies showed that under appropriate culture conditions, ESCs can differentiate into corneal epithelial cell (CEC)-like cells, [24][25][26][27] which strongly expressed specific terminally differentiated CEC markers CK3, CK12, and Cx43/50. However, the proliferative capacity of these CEC-like cells was limited and could hardly subculture in vitro.…”