title: Wnt/β-catenin signaling regulates proliferation of human cornea epithelial stem/progenitor cells.
abstract: OBJECTIVE
  To investigate the expression and role of the Wnt signaling pathway in human limbal stem cells (LSCs).
  
  
  METHODS
  Total RNA was isolated from the human limbus and central cornea. Limbal or cornea-specific transcripts were identified through quantitative real-time PCR. Protein expression of Wnt molecules was confirmed by immunohistochemistry on human ocular tissue. Activation of Wnt signaling using lithium chloride was achieved in vitro and its effects on LSC differentiation and proliferation were evaluated.
  
  
  RESULTS
  Expression of Wnt2, Wnt6, Wnt11, Wnt16b, and four Wnt inhibitors were specific to the limbal region, whereas Wnt3, Wnt7a, Wnt7b, and Wnt10a were upregulated in the central cornea. Nuclear localization of β-catenin was observed in a very small subset of basal epithelial cells only at the limbus. Activation of Wnt/β-catenin signaling increased the proliferation and colony-forming efficiency of primary human LSCs. The stem cell phenotype was maintained, as shown by higher expression levels of putative corneal epithelial stem cell markers, ATP-binding cassette family G2 and ΔNp63α, and low expression levels of mature cornea epithelial cell marker, cytokeratin 12.
  
  
  CONCLUSIONS
  These findings demonstrate for the first time that Wnt signaling is present in the ocular surface epithelium and plays an important role in the regulation of LSC proliferation. Modulation of Wnt signaling could be of clinical application to increase the efficiency of ex vivo expansion of corneal epithelial stem/progenitor cells for transplantation.
authors.affiliation: Cornea and Uveitis Division, Jules Stein Eye Institute, Los Angeles, California 90095, USA.
authors.forename: Martin N
authors.initials: MN
authors.lastname: Nakatsu
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Ding
authors.forename: Madelena Y
authors.initials: MY
authors.lastname: Ng
authors.forename: Thuy T
authors.initials: TT
authors.lastname: Truong
authors.forename: Fei
authors.initials: F
authors.lastname: Yu
authors.forename: Sophie X
authors.initials: SX
authors.lastname: Deng
mesh_terms: D000328:Adult; D000368:Aged; D049109:Cell Proliferation; D016039:Corneal Transplantation; D019573:Epithelium, Corneal / Q000166:cytology* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D016850:Limbus Corneae / Q000166:cytology / Q000378:metabolism; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D051153:Wnt Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D060508:Wnt3 Protein; D055815:Young Adult; D051176:beta Catenin / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C484142:WNT10A protein, human; C555507:WNT3 protein, human; C490674:WNT6 protein, human; C092778:WNT7A protein, human; D051153:Wnt Proteins; C540523:Wnt11 protein, human; D060508:Wnt3 Protein; D051176:beta Catenin; D012313:RNA