title: Lineage tracing in the adult mouse corneal epithelium supports the limbal epithelial stem cell hypothesis with intermittent periods of stem cell quiescence.
abstract: The limbal epithelial stem cell (LESC) hypothesis proposes that LESCs in the corneal limbus maintain the corneal epithelium both during normal homeostasis and wound repair. The alternative corneal epithelial stem cell (CESC) hypothesis proposes that LESCs are only involved in wound repair and CESCs in the corneal epithelium itself maintain the corneal epithelium during normal homeostasis. We used tamoxifen-inducible, CreER-loxP lineage tracing to distinguish between these hypotheses. Clones of labelled cells were induced in adult CAGG-CreER;R26R-LacZ reporter mice and their distributions analysed after different chase periods. Short-lived clones, derived from labelled transient amplifying cells, were shed during the chase period and long-lived clones, derived from stem cells, expanded. At 6 weeks, labelled clones appeared at the periphery, extended centripetally as radial stripes and a few reached the centre by 14 weeks. Stripe numbers depended on the age of tamoxifen treatment. Stripes varied in length, some were discontinuous, few reached the centre and almost half had one end at the limbus. Similar stripes extended across the cornea in CAGG-CreER;R26R-mT/mG reporter mice. The distributions of labelled clones are inconsistent with the CESC hypothesis and support the LESC hypothesis if LESCs cycle between phases of activity and quiescence, each lasting several weeks.
authors.affiliation: Centre for Integrative Physiology, University of Edinburgh Medical School, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK.
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Dorà
authors.affiliation: Medical and Developmental Genetics Section, MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hill
authors.affiliation: School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
authors.forename: J Martin
authors.initials: JM
authors.lastname: Collinson
authors.affiliation: Centre for Integrative Physiology, University of Edinburgh Medical School, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK. Electronic address: John.West@ed.ac.uk.
authors.forename: John D
authors.initials: JD
authors.lastname: West
mesh_terms: D000818:Animals; D019070:Cell Lineage; D049109:Cell Proliferation; D019573:Epithelium, Corneal / Q000166:cytology / Q000378:metabolism*; D006706:Homeostasis; D016850:Limbus Corneae / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D014945:Wound Healing
keywords: Cornea; Limbal epithelial stem cells; Limbus; Lineage tracing; Stem cell quiescence; Stem cells