Altshuler, A. | bioRxiv Science

bioRxiv2021

Soft limbal niche maintains stem cell compartmentalization and function through YAP

Stem cells (SCs) decision to self-renew or differentiate largely depends on the external control of their niche. However, the complex mechanisms that underlie this crosstalk are poorly understood. To address this question, we focused on the corneal epithelial SC model in which the SC niche, known as the limbus, is spatially segregated from the differentiation compartment. We report that the unique biomechanical property of the limbus supports the nuclear localization and function of Yes-associated protein (YAP), a putative mediator of the mechanotransduction pathway. Perturbation of tissue stiffness or YAP activity affects SC function as well as tissue integrity under homeostasis and significantly inhibited the regeneration of the SC population following SC depletion. In vitro experiments revealed that substrates with the rigidity of the corneal differentiation compartment inhibit YAP localization and induce differentiation, a mechanism that is mediated by the TGF{beta}-SMAD2/3 pathway. Taken together, these results indicate that SC sense biomechanical niche signals and that manipulation of mechano-sensory machinery or its downstream biochemical output may bear fruits in SC expansion for regenerative therapy. HighlightsO_LIYAP is essential for limbal SC function, regeneration, and dedifferentiation C_LIO_LILox over-expression stiffens the limbal niche, affects SC phenotype and corneal integrity C_LIO_LICorneal rigidity represses YAP and stemness in a SMAD2/3-dependent manner C_LIO_LIManipulation of mechanosensory or TGF-{beta} pathway influences limbal SC expansion in vitro C_LI

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bioRxiv2020

Capturing limbal epithelial stem cell population dynamics, signature and their niche

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 one of 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 performed an in-depth analysis of the murine limbal epithelium by single-cell RNA sequencing and quantitative lineage tracing. The generated data provided an atlas of cell states of the corneal epithelial lineage, and particularly, revealed the co-existence of two novel LSC populations that reside in separate and well-defined sub-compartments. In the “outer” limbus, we identified a primitive widespread population of quiescent LSCs (qLSCs) that uniformly express Krt15/Gpha2/Ifitm3/Cd63 proteins, while the “inner” limbus host prevalent active LSCs (aLSCs) co-expressing Krt15-GFP/Atf3/Mt1-2/Socs3. Analysis of LSC population dynamics suggests that while qLSCs and aLSCs possess different proliferation rates, they both follow similar stochastic rules that dictate their self-renewal and differentiation. Finally, T cells were distributed in close proximity to qLSCs. Indeed, their absence or inhibition resulted in the loss of quiescence and delayed wound healing. Taken together, we propose that divergent regenerative strategies are tailored to properly support tissue-specific physiological constraints. The present study suggests that in the case of the cornea, quiescent epithelial SCs are abundant, follow stochastic rules and neutral drift dynamics.Competing Interest StatementThe authors have declared no competing interest.View Full Text

cell biology↗