title: IL6 and the human limbal stem cell niche: a mediator of epithelial-stromal interaction.
abstract: The corneal epithelium is maintained by the limbal epithelial stem cells (LESCs). In this study, an in vitro model is proposed for the investigation of cell-cell interactions involving LESC maintenance. Imaging of the limbal niche demonstrated close spatial arrangement between basal limbal epithelial cells within putative LESC niche structures and fibroblasts in the stroma. Interactions of the human limbal epithelial (HLE) cells and mitotically active human limbal fibroblasts (HLF) were studied for the first time in a serum-free in vitro model that simulated aspects of the limbal niche microenvironment. HLE cocultured in a ratio 3:1 with HLF exhibited enhanced expression of the putative stem cell markers ABCG2 and p63α and holoclones were preserved as shown by colony-forming efficiency assays, clonal analysis, and colony characterisation. Interleukin 6 (IL6) was found to be up-regulated in the 3.1SF system when compared to the HLE culture with growth-arrested fibroblasts and serum (gold standard system, GS). IL6 caused a time-dependent phosphorylation of STAT3 in HLE cells. STAT3 and IL6 inhibition in 3.1SF cultures significantly reduced HLE colony-forming efficiency, suggesting a previously undetected STAT3-mediated involvement of IL6 in the maintenance of HLE cells in a progenitor-like state.
authors.affiliation: Department of Ocular Biology and Therapeutics, UCL Institute of Ophthalmology, London, UK. m.notara@ucl.ac.uk
authors.forename: Maria
authors.initials: M
authors.lastname: Notara
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Shortt
authors.forename: Grazyna
authors.initials: G
authors.lastname: Galatowicz
authors.forename: Virginia
authors.initials: V
authors.lastname: Calder
authors.forename: Julie T
authors.initials: JT
authors.lastname: Daniels
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D017209:Apoptosis; D049109:Cell Proliferation; D018920:Coculture Techniques; D019573:Epithelium, Corneal / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D016850:Limbus Corneae / Q000166:cytology* / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D017154:Stromal Cells / Q000166:cytology; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D015850:Interleukin-6; D009363:Neoplasm Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins