Visualizing the Contribution of Keratin-14+ Limbal Epithelial Precursors in Corneal Wound Healing.
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ABSTRACT:
SUBMITTER: Park M
PROVIDER: S-EPMC6335450 | biostudies-literature | 2019 Jan
REPOSITORIES: biostudies-literature
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Project description:Stem cells (SCs) are traditionally viewed as rare, slow-cycling cells that follow deterministic rules dictating their self-renewal or differentiation. It was several decades ago, when limbal epithelial SCs (LSCs) that regenerate the corneal epithelium were among the first sporadic, quiescent SCs ever discovered. However, LSC dynamics, heterogeneity and genetic signature are largely unknown. Moreover, recent accumulating evidence strongly suggested that epithelial SCs are actually abundant, frequently dividing cells that display stochastic behavior. In this work, we combined single-cell RNA sequencing and advanced quantitative lineage tracing for in-depth analysis of the murine limbal epithelium. The generated data provides an atlas of cell states of the entire corneal epithelial lineage and reveales the co-existence of two novel LSC populations that reside in separate and well-defined sub-compartments. In the “outer” limbus, we discovered a primitive widespread population of quiescent LSCs (qLSCs) that uniformly express Krt15/Gpha2/Ifitm3/Cd63 proteins that serve as SC reservoire and in boundary formation. In the “inner” peri-corneal limbus, we identified prevalent active LSCs (aLSCs) that express Krt15-GFP/Atf3/Mt1-2/Socs3 and maintain homeostasis. We propose that these SC populations are abundant, follow stochastic rules and neutral drift dynamics. Notably, we provide evidence that T cells serve as niche cells for qLSCs, regulating quiescence and wound response. Taken together, we propose that divergent regenerative strategies are tailored to properly support tissue specific physiological constraints.
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Project description:Corneal transparency, dependent on the integrity of epithelial cells, is essential for vision. Corneal epithelial damage is one of the most commonly observed ocular conditions and proper wound healing is necessary for corneal transparency. Sirt6, a histone deacetylase, has been shown to regulate many cellular events including aging and inflammation. However, its specific role in corneal epithelial wound healing remains unknown. Here we demonstrated that Sirt6 was expressed in corneal epithelial cells and its expression decreased with age. In an in vivo corneal epithelial wound healing model, Sirt6 deficiency resulted in delayed and incomplete wound healing and was associated excessive inflammation in the corneal stroma and dysfunction of Notch signaling, leading to keratinization of the corneal epithelium and corneal opacity. Aging Sirt6-deficient mice spontaneously developed corneal keratitis with extensive infiltration of inflammatory cells into the cornea. In vitro experiments demonstrated that primary corneal epithelial cells with Sirt6 downregulation expressed increased basal levels of inflammatory genes and exhibited hyper-inflammatory reactivity to IL-1β and TNFα treatment. These results provide compelling evidence that Sirt6 is a critical regulator of inflammation in the cornea, and is responsible for corneal epithelial wound healing, thus contributing to the maintenance of epithelial integrity and corneal transparency.
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