title: Loss of corneal epithelial heparan sulfate leads to corneal degeneration and impaired wound healing.
abstract: OBJECTIVE
  Heparan sulfate (HS) is a highly modified glycosaminoglycan (GAG) bound to a core protein to form heparan sulfate proteoglycans (HSPGs) that are vital in many cellular processes ranging from development to adult physiology, as well as in disease, through interactions with various protein ligands. This study aimed to elucidate the role of HS in corneal epithelial homeostasis and wound healing.
  
  
  METHODS
  An inducible quadruple transgenic mouse model was generated to excise Ext1 and Ndst1, which encode the critical HS chain elongation enzyme and N-deacetylase/N-sulfotransferase, respectively, in keratin 14-positive cells upon doxycycline induction.
  
  
  RESULTS
  EXT(Δ/ΔCEpi) mice (deletion of Ext1 in corneal epithelium) induced at P20 presented progressive thinning of the corneal epithelium with a significant loss in the number of epithelial layers by P55. EXT(Δ/ΔCEpi) mice presented tight junction disruption, loss of cell-basement membrane adhesion complexes, and impaired wound healing. Interestingly, EXT(Δ/ΔCEpi) and NDST(Δ/ΔCEpi) mice presented an increase in cell proliferation, which was assayed by both Ki67 staining and 5-ethynyl-2'-deoxyuridine (EdU) incorporation. Moreover, EXT(Δ/ΔCEpi) mice presented compromised epithelial stratification 7 days after a debridement wound. The conditional knockout of HS from keratocytes using the keratocan promoter led to no corneal abnormalities or any disruption in wound healing.
  
  
  CONCLUSIONS
  Corneal epithelial cells require HS for maintaining corneal homeostasis, and the loss of epithelial HS leads to both impaired wound healing and impaired corneal stratification.
authors.affiliation: Department of Ophthalmology University of Cincinnati, Cincinnati, Ohio, United States.
authors.forename: Vivien Jane
authors.initials: VJ
authors.lastname: Coulson-Thomas
authors.affiliation: Department of Ophthalmology University of Cincinnati, Cincinnati, Ohio, United States.
authors.forename: Shao-Hsuan
authors.initials: SH
authors.lastname: Chang
authors.affiliation: Department of Ophthalmology, Chang-Gung Memorial Hospital, Chang-Gung University College of Medicine, Linko, Taiwan.
authors.forename: Lung-Kun
authors.initials: LK
authors.lastname: Yeh
authors.affiliation: Department of Biochemistry, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Yvette May
authors.initials: YM
authors.lastname: Coulson-Thomas
authors.affiliation: Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, California, United States.
authors.forename: Yu
authors.initials: Y
authors.lastname: Yamaguchi
authors.affiliation: Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California-San Diego, La Jolla, California, United States.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Esko
authors.affiliation: Department of Ophthalmology University of Cincinnati, Cincinnati, Ohio, United States.
authors.forename: Chia-Yang
authors.initials: CY
authors.lastname: Liu
authors.affiliation: Department of Ophthalmology University of Cincinnati, Cincinnati, Ohio, United States.
authors.forename: Winston
authors.initials: W
authors.lastname: Kao
mesh_terms: D000818:Animals; D003316:Corneal Diseases / Q000378:metabolism*; D019573:Epithelium, Corneal / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006497:Heparan Sulfate / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology*; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D008854:Microscopy, Electron; D014945:Wound Healing / Q000502:physiology*
chemical_list: D006497:Heparan Sulfate