Three-dimensional structure of the mammalian limbal stem cell niche
Abstract
Purpose
Although the existence of the limbal stem cell (LSC) niche is accepted, precise knowledge of its 3D architecture remains incomplete.
Methods
The LSC niche was explored on freshly excised corneoscleral rims from human donors (n = 47), pigs (n = 15) and mice (n = 27) with full-field optical coherence microscopy (FFOCM).
Results
Limbal crypt features were detected in 90% of human corneoscleral rims, extending between the palisades of Vogt as radial (74%) and/or rounded (23%) forms, often branching off to or becoming interconnected by sub-scleral radially or circumferentially oriented crypts (56%). [kg1] Mean crypt volume represented 16% of sampled limbal volume on the vertical axis and 8% on the horizontal axis. In pigs, palisades were finer and crypts wider with relatively uniform distribution around the eye, and radial orientation, connecting to numerous narrow criss-crossing invaginations beneath the sclera. In mice, only a circumferential limbal trough was detected. Mean crypt volume represented 13% of limbal volume in humans, 9% in pigs and 7% in mice. FFOCM combined with fluorescence showed presence of p63-α+ cells and cytokeratin-3 + cells in the limbal crypts. LSC density increased with percentage limbal volume occupied by crypts. Colony Forming Efficiency increased with limbal crypt volume. [kg1] See how to rephrase all this.
Conclusions
Crypt architecture in the three species appears associated with eye exposure to light. Clone production correlated strongly with the limbal crypt volume in humans indicating that limbal crypts constitute a niche for adult limbal stem cells. FFOCM imaging could assist in assessment of the richness of the limbal crypts and targeted biopsy for cell culture.
