Defining compartmentalized stem cell populations with distinct cell division dynamics in the ocular surface epithelium

ABSTRACTAdult tissues contain label-retaining cells (LRCs), which are relatively slow-cycling and considered to represent a property of tissue stem cells (SCs). In the ocular surface epithelium, LRCs are present in the limbus and conjunctival fornix; however, the character of these LRCs remains unclear, owing to lack of appropriate molecular markers. Using three CreER transgenic mouse lines, we demonstrate that the ocular surface epithelium accommodates spatially distinct populations with different cell division dynamics. In the limbus, long-lived Slc1a3CreER-labeled SCs either migrate centripetally toward the central cornea or slowly expand their clones laterally within the limbal region. In the central cornea, non-LRCs labeled with Dlx1CreER and K14CreER behave as short-lived progenitor cells. The conjunctival epithelium in the bulbar, fornix and palpebral compartment is regenerated by regionally unique SC populations. Severe damage to the cornea leads to the cancellation of SC compartments and conjunctivalization, whereas milder limbal injury induces a rapid increase of laterally expanding clones in the limbus. Taken together, our work defines compartmentalized multiple SC/progenitor populations of the mouse eye in homeostasis and their behavioral changes in response to injury.

Defining compartmentalized stem and progenitor populations with distinct cell division frequency in the ocular surface epithelium

SummaryAdult tissues contain label-retaining cell (LRC)s, which are relatively slow-cycling and considered to represent a unique property of tissue stem cell (SC)s. In the ocular surface epithelium, LRCs are detected in the limbus, a boundary between cornea and conjunctiva, and the fornix of the conjunctiva; however, the character of LRCs and identity of SCs remain unclear due to lack of appropriate molecular markers. Here we show that the ocular surface epithelium accommodates spatially distinct stem/progenitor populations with different cell division frequency. By combining EdU pulse-chase analysis and lineage tracing with three CreER transgenic mouse lines: Slc1a3CreER, Dlx1CreER and K14CreER, we detect distinct dynamics of epithelial SCs in the cornea and conjunctiva. In the limbus, long-lived SCs are labeled with Slc1a3CreER and they either migrate centripetally toward the central cornea or laterally expand their clones within the limbal region. In the central cornea, cells are mostly non-LRCs, labeled by Dlx1CreER and K14CreER, and the number of clones declines after a short period of time with rare long-lasting clones, suggesting their properties as short-lived progenitor cells. In the conjunctival epithelium, which consists of bulbar, fornix and palpebral conjunctiva, each territory is regenerated by compartmentalized, distinct SC populations without migrating one region to another. The severe damage of the cornea leads to the cancellation of SC compartments, causing conjunctivalization of the eye, whereas milder limbal injury induces a rapid increase of laterally-expanding clones in the limbus. Taken together, our work provides lineage tracing tools of the eye and defines compartmentalized, multiple SC/progenitor populations in homeostasis and their behavioral changes in response to injury.

Efficacy of 0.01% dexamethasone solution in comprehensive therapy of dry eye disease

Introduction. The officinal dosage of dexamethasone solution (0.1%) has a marked localized antiinflammatory effect. But the widespread use of this dose in the management of dry eye diseases is limited by the risk of damage to the cornea. Therefore, the authors developed a solution containing 0.01% dexamethasone phosphate in combination with 6% polyvinylpyrolidone and 1.5%–5.5% dextrose [3]. Aim. To study the effects of this novel anti-inflammatory solution on corneal inflammatory processes. Materials and methods. This study included a cohort of 25 patients (50 eyes) with corneal–conjunctival xerosis. Lower tear meniscus index, precorneal tear film production, stability and osmolarity, and the degree of staining of the ocular surface epithelium with vital solutions were assessed prior to the treatment and on day 28 of the study. The presence of the cytokines IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-17A, IL-1Ra, TNF-α, INF-α, and INF-γ in patients’ tear fluid and blood plasma was quantified using ELISA. All patients were asked to complete a questionnaire to evaluate subjective signs of xerosis of the ocular surface. Results. Statistically significant increases in tear meniscus index, precorneal tear film stability, and main and total tear production, with a significant decrease in tear film osmolarity were observed by day 28 of the study. In addition, positive changes in objective parameters relating to the ocular surface epithelium were further confirmed by the patients’ evaluations of their quality of life. Furthermore, the degree of staining of the ocular surface epithelium with vital solutions also decreased. Conclusions. The results of the study demonstrate the high level of effectiveness of the developed medication as a treatment for dry eye diseases of various etiologies.