title: Postnatal corneal transparency, keratocyte cell cycle exit and expression of ALDH1A1.
abstract: OBJECTIVE
  Recent studies have shown that rabbit corneal keratocytes abundantly express two water-soluble proteins, transketolase (TKT) and aldehyde dehydrogenase class 1A1 (ALDH1A1), in vivo and that these proteins may contribute to corneal transparency at the cellular level. The purpose of this study was to determine the relationship between the expression of these proteins and the development of postnatal corneal transparency.
  
  
  METHODS
  Rabbits 1 day to 42 days of postnatal age were evaluated by in vivo confocal microscopy (CM) to measure corneal epithelial thickness, stromal thickness, and corneal haze. Selected corneas were then processed for immunocytochemistry and Western and Northern blot analyses, to determine stromal cell density, cell cycle entry, and expression of ALDH1A1 and TKT.
  
  
  RESULTS
  Quantitative measurement of corneal haze showed that the postnatal cornea was hazy after birth and became transparent during the first weeks after eyelid opening. Development of transparency was associated with decreased cytoplasmic light-scattering from postnatal corneal stromal cells, with the appearance of nuclear light-scattering after eyelid opening. Four days after birth, stromal cell density decreased rapidly, and the cells became quiescent, showing decreased staining by Ki67, a cell cycle marker. Whereas expression of TKT showed a gradual increase after birth, ALDH1A1 showed a marked increase after eyelid opening, and the combined expression significantly correlated with the reduction in light-scattering by postnatal stromal cells.
  
  
  CONCLUSIONS
  The data suggest that development of postnatal corneal transparency is associated with decreased keratocyte density and quiescence and the expression of TKT/ALDH1A1.
authors.affiliation: Department of Ophthalmology, University of California, Irvine, California, USA. jjester@uci.edu
authors.forename: James V
authors.initials: JV
authors.lastname: Jester
authors.forename: Young G
authors.initials: YG
authors.lastname: Lee
authors.forename: Jiying
authors.initials: J
authors.lastname: Huang
authors.forename: Jennifer
authors.initials: J
authors.lastname: Houston
authors.forename: Brook
authors.initials: B
authors.lastname: Adams
authors.forename: H Dwight
authors.initials: HD
authors.lastname: Cavanagh
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Petroll
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000378:metabolism*; D000080924:Aldehyde Dehydrogenase 1 Family; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D015152:Blotting, Northern; D015153:Blotting, Western; D002452:Cell Count; D002453:Cell Cycle / Q000502:physiology*; D003315:Cornea / Q000502:physiology*; D003319:Corneal Stroma / Q000166:cytology* / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D007527:Isoenzymes / Q000378:metabolism*; D019394:Ki-67 Antigen / Q000378:metabolism; D018613:Microscopy, Confocal; D011247:Pregnancy; D011817:Rabbits; D050697:Retinal Dehydrogenase; D014174:Transketolase / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D019394:Ki-67 Antigen; D000080924:Aldehyde Dehydrogenase 1 Family; D000444:Aldehyde Dehydrogenase; D050697:Retinal Dehydrogenase; D014174:Transketolase