title: TGF-beta receptor types I and II are differentially expressed during corneal epithelial wound repair.
abstract: OBJECTIVE
  It has been demonstrated that cells migrating to cover an epithelial débridement wound exit the cell cycle and that the cell-cycle inhibitor p15(INK4b) is upregulated in these cells. TGF-beta signaling has been implicated in both of these processes, and this study was conducted to determine whether the expression and localization of TGF-beta receptor (TbetaR)-I and -II are altered during corneal epithelial wound repair.
  
  
  METHODS
  Three-millimeter superficial keratectomy wounds and 3-mm débridement wounds were made in central rat cornea and allowed to heal in vivo for 1 to 48 hours. Immunofluorescence microscopy and Western blot analysis were used to determine the localization and expression of TbetaR-I and -II. Unwounded rat corneas served as control samples. To determine the effect of epidermal growth factor (EGF) and TGF-beta1 on p15(INK4b) and TbetaR-I and -II expression, human corneal epithelial cells were grown in culture to 50% to 60% confluence, and EGF (5 ng/ml) and/or TGF-beta1 (2 ng/ml) were added for 6 hours. Cells were harvested and p15(INK4b) and TBR-I and -II levels were assayed by using Western blot analysis.
  
  
  RESULTS
  In unwounded corneas, TbetaR-I and TbetaR-II were present at low levels across the cornea, with higher levels in limbal epithelium. Both TbetaR-I and -II were upregulated after wounding. However, levels of TbetaR-II appeared to increase in the epithelial cells that had migrated to cover the wound area, whereas TbetaR-I was upregulated in the entire corneal epithelium. Western blot analysis indicated that both TbetaR-I and -II were upregulated threefold after wounding. In cultured cells, EGF and TGF-beta1 stimulated TbetaR-II; however, neither one stimulated TbetaR-I expression. TGF-beta1 stimulated p15(INK4b) protein levels threefold.
  
  
  CONCLUSIONS
  After wounding, TbetaR-I and TbetaR-II were both expressed at high levels in cells migrating to cover a corneal wound, suggesting that TGF-beta signaling is involved in blocking migrating cells from progressing through the cell cycle. This blockage, at least in part, involves the inhibitor p15(INK4b). In addition, although both TbetaR-I and TbetaR-II are upregulated during wound repair, they appear to be differentially regulated.
authors.affiliation: Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114-2500, USA. zieske@vision.eri.harvard.edu
authors.forename: J D
authors.initials: JD
authors.lastname: Zieske
authors.forename: A E
authors.initials: AE
authors.lastname: Hutcheon
authors.forename: X
authors.initials: X
authors.lastname: Guo
authors.forename: E H
authors.initials: EH
authors.lastname: Chung
authors.forename: N C
authors.initials: NC
authors.lastname: Joyce
mesh_terms: D030201:Activin Receptors, Type I; D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques / Q000379:methods; D019573:Epithelium, Corneal / Q000293:injuries / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D008297:Male; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015854:Up-Regulation; D014945:Wound Healing
chemical_list: D018125:Receptors, Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; C000625843:Tgfbr1 protein, rat