Discrete limbal epithelial stem cell populations mediate corneal homeostasis and wound healing

The accessibility and transparency of the cornea permit robust stem cell labeling and in vivo cell fate mapping. Limbal epithelial stem cells (LSCs) that renew the cornea are traditionally viewed as rare, slow-cycling cells that follow deterministic rules dictating their self-renewal or differentiation. Here, we combined single-cell RNA sequencing and advanced quantitative lineage tracing for in-depth analysis of the murine limbal epithelium. These analysis revealed the co-existence of two LSC populations localized in separate and well-defined sub-compartments, termed the “outer” and “inner” limbus. The primitive population of quiescent outer LSCs participates in wound healing and boundary formation, and these cells are regulated by T cells, which serve as a niche. In contrast, the inner peri-corneal limbus hosts active LSCs that maintain corneal epithelial homeostasis. Quantitative analyses suggest that LSC populations are abundant, following stochastic rules and neutral drift dynamics. Together these results demonstrate that discrete LSC populations mediate corneal homeostasis and regeneration. [Display omitted] •Discovery of two limbal stem cell (LSC) populations and, their signature and niches•The outer limbus hosts quiescent LSCs while inner LSCs actively renew the cornea•LSCs are abundant in their niche, following stochastic rules and neutral drift dynamics•T cells regulate outer LSC quiescence, marker expression, and wound healing response Single-cell RNA sequencing combined with quantitative lineage tracing revealed the existence, signature, and dynamics of two distinct murine LSC populations, which reside in spatially defined sub-compartments, termed the “outer” and “inner” limbus. Each LSC population exhibits distinct cycling properties, regulation by the niche, and function under homeostasis and regeneration.