Stem cell (SC) division, deployment, and differentiation are processes that contribute to corneal epithelial renewal. Until now studying the destiny of these cells in a living mammal has not been possible. However, the advent of inducible multicolor genetic tagging and powerful imaging technologies has rendered this achievable in the translucent and readily accessible murine cornea. K14CreER^T2-Confetti mice that harbor two copies of the Brainbow 2.1 cassette, yielding up to 10 colors from the stochastic recombination of fluorescent proteins, were used to monitor K-14⁺ progenitor cell dynamics within the corneal epithelium in live animals. Multicolored columns of cells emerged from the basal limbal epithelium as they expanded and migrated linearly at a rate of 10.8 µm/day toward the central cornea. Moreover, the permanent expression of fluorophores, passed on from progenitor to progeny, assisted in discriminating individual clones as spectrally distinct streaks containing more than 1,000 cells within the illuminated area. The centripetal clonal expansion is suggestive that a single progenitor cell is responsible for maintaining a narrow corridor of corneal epithelial cells. Our data are in agreement with the limbus as the repository for SC as opposed to SC being distributed throughout the central cornea. This is the first report describing stem/progenitor cell fate determination in the murine cornea using multicolor genetic tracing. This model represents a powerful new resource to monitor SC kinetics and fate choice under homeostatic conditions, and may assist in assessing clonal evolution during corneal development, aging, wound-healing, disease, and following transplantation. Stem Cells 2015;33:157–169

Background.: A healthy cornea is reliant on a distinct population of stem cells (SC) that replace damaged or aging epithelium throughout life. Depletion of the SC pool or damage to the niche can result in a blinding and painful condition known as limbal-SC deficiency (LSCD). Although current treatment strategies for reconstituting the ocular surface for patients suffering LSCD are promising, they are complicated by transferring autologous or allogeneic progenitors in the presence of animal, human, and synthetic products. We report on the safe and efficacy of a unique autologous SC transfer technique that utilizes an Food and Drug Administration-approved contact lens (CL) as the SC substrate and carrier for patients with LSCD. Methods.: Three patients with LSCD due to aniridia (n=1) and posttreatment for recurrent ocular surface melanoma (n=2) were included. Limbal (n=2) or conjunctival biopsies (n=1) were harvested and progenitors expanded ex vivo on therapeutic CLs in the presence of autologous serum. Cell-laden CLs were transferred to the patient's corneal surface and clinical outcome measures were recorded (follow-up range, 8–13 months). Results.: A stable transparent corneal epithelium was restored in each patient. There was no recurrence of conjunctivalization or corneal vascularization, and a significant improvement in symptom score occurred in all patients. Best-corrected visual acuity was increased in all eyes after the procedure. Conclusion.: Ex vivo expansion of ocular surface epithelium in the presence of autologous serum and transplantation with the aid of a soft CLs is a promising new technique capable of achieving ocular surface rehabilitation.

Purpose. Pterygium is a proliferative, inflammatory, and invasive ocular surface disease associated with excessive ultraviolet (UV) exposure. This investigation was conducted to identify UV activated signaling pathways in pterygium epithelial cells (PECs) that mediate cytokine and growth factor production and to determine whether these pathways are sensitive to blockade by anti-inflammatory agents such as retinoic acid (RA) and interferon (IFN)-α. methods PECs were pretreated with or without inhibitors of the ERK1/2, JNK, and p38 (PD98059, SB202190, and SB203580, respectively) mitogen-activated protein kinases (MAPK) or with inhibitors of the tyrosine kinase activity of epidermal growth factor receptor (EGFR; PD153035) and platelet-derived growth factor (PDGF; AG1295); exposed to UVB (20 mJ/cm²); and then further treated with the same inhibitors. Media were harvested and analyzed by ELISA for interleukin (IL)-6, IL-8, and vascular endothelial growth factor (VEGF). Cytokine mRNA was assessed by reverse transcription–polymerase chain reaction (RT-PCR). results Inhibitors of ERK1/2, JNK, and p38 MAPKs significantly abolished the UVB-mediated increase in IL-6, IL-8, and VEGF. PD153035 reduced IL-8, AG1295 repressed IL-6, and both inhibitors partially downregulated VEGF production in UV-exposed PECs. RA and IFN-α dose dependently abrogated IL-6 and IL-8 but had no effect on VEGF expression after UV exposure. conclusions The results have identified a stress-induced intracellular pathway and potential cell-surface transmitters that may be relevant to pterygium development. Moreover, two anti-inflammatory/antiangiogenic agents were identified that reduced cytokine production in the study model. Topical application of these drugs may benefit patients with pterygia, potentially reducing the necessity for surgical interven-tion.

Inclusion of the preservative benzalkonium chloride (BAC) in ophthalmic solutions is prevalent, despite the noted potential for exacerbating dry eye disease (DED). Whilst studies incorporating BAC have assessed its' effects as a mouse model of DED, the impact on limbal epithelia is under-studied. Our investigation aimed to comprehensively assess the impact of different BAC dosing regimens and their suitability as a mouse model of DED. C57BL/6J mice (n = 72) were administered topical BAC (0.05-0.2%) over 7 days. Fluorescein staining, corneal smoothness index, and immuno-histological analyses were applied to determine architectural and cellular changes on the ocular surface following BAC treatment. The effect of BAC (0.0001-0.01%) on cultivated primary mouse corneo-limbal epithelial cells (CLECs) (n = 6) was examined using morphological and functional assays. Whilst 0.2% BAC induced severe corneal epithelial defects, 0.1% BAC dispensed once daily over 7 days, induced punctate fluorescein staining without detriment to corneal smoothness. Histochemical staining revealed disorganized basal corneal epithelial cells with enlarged cytoplasmic halos. Furthermore, PAS+ goblet cells were decreased. BAC treatment also modulated K14 expression and distribution within the limbus. In cultured CLEC, BAC triggered cell contraction and vacuolation, increased LDH release and elevated cell necrosis by 4.1-fold. Concentrations of BAC as low as 0.0001% decreased colony formation. This study describes how exposing C57BL/6 mice to BAC induce some clinicopathological features of DED seen in humans, and therefore provides the foundations to explore the consequences on the ocular surface, particularly on limbal epithelia and its' stem cells.