title: Inhibition of corneal fibrosis by Smad7 in rats after photorefractive keratectomy.
abstract: BACKGROUND
  Haze or corneal subepithelial fibrosis is one of the common complications after refractive surgery procedures, such as photorefractive keratectomy (PRK), laser epithelial keratomileusis, and epipolis laser in situ keratomileusis, which would result in refractive regression, decreased visual quality, and corneal opacification. Haze directly resulted from corneal fibrosis mediated by transforming growth factor β (TGFβ). Smad7, an inhibitory Smad, can inhibit TGFβ signal transduction. Recently, the effects of Smad7 on the inhibition of fibrosis in several organs have been studied, while little is known about the effects on cornea after PRK. This study was aimed to determine the effects of lentiviral-mediated Smad7 gene expression on corneal fibrosis in rats after PRK.
  
  
  METHODS
  Four different experimental groups were established using right eyes of Sprague-Dawley rats. Thirty-two eyes underwent de-epithelialization only and served as a sham operation group (group 1). Ninety-six eyes underwent PRK operation and were further divided into group 2 (the PRK group) without lentivector administration, group 3 (the Lv-blank group) with control lentiviral vector without Smad7 administration, and group 4 (the Lv-Smad7 group) with Smad7 expressing lentiviral vector Smad7 administration. At 1 day, 1 week, 1 month, and 3 months after PRK, the transfection efficiency was determined by measuring the fluorescence signal as well as Smad7 protein and mRNA levels. Corneas were further processed for immunoblotting to assess the phosphorylation of Smad2 as a downstream event of TGFβ/Smad signaling. The expression of fibrotic markers, such as α-smooth muscle actin (α-SMA), Type III collagen (collagen III), and cell cycle-related marker Ki67, was measured by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR).
  
  
  RESULTS
  Lentivirus-mediated exogenous Smad7 gene expression in rat corneal tissue resulted in reduced activation of TGFβ/Smad signaling caused by downregulation of phosphorylation of Smad2. Smad7 also downregulated the expression of TGFβ2. Markers of cell proliferation and fibrosis, including Ki67, α-SMA, and collagen III, were inhibited by Smad7 up to 3 months after PRK operation.
  
  
  CONCLUSIONS
  Smad7 gene transfer inhibits fibrogenic responses of cornea in rats after PRK.
authors.affiliation: Department of Ophthalmology, Eye & ENT Hospital of Fudan University, Shanghai 200031, China; Department of Ophthalmology, the 85th Hospital of People's Liberation Army, Shanghai 200052, China.
authors.forename: Ti
authors.initials: T
authors.lastname: Wang
authors.forename: Xing-tao
authors.initials: XT
authors.lastname: Zhou
authors.forename: Yan
authors.initials: Y
authors.lastname: Yu
authors.forename: Jing-yin
authors.initials: JY
authors.lastname: Zhu
authors.forename: Jin-hui
authors.initials: JH
authors.lastname: Dai
authors.forename: Xiao-mei
authors.initials: XM
authors.lastname: Qu
authors.forename: Qi-hua
authors.initials: QH
authors.lastname: Le
authors.forename: Ren-yuan
authors.initials: RY
authors.lastname: Chu
mesh_terms: D000199:Actins / Q000235:genetics; D000818:Animals; D024061:Collagen Type III / Q000235:genetics; D003315:Cornea / Q000473:pathology*; D005355:Fibrosis; D015316:Genetic Therapy; D019394:Ki-67 Antigen / Q000235:genetics; D016086:Lentivirus / Q000235:genetics; D018903:Photorefractive Keratectomy / Q000009:adverse effects*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D051906:Smad7 Protein / Q000235:genetics* / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology
chemical_list: D000199:Actins; D024061:Collagen Type III; D019394:Ki-67 Antigen; D012333:RNA, Messenger; D051906:Smad7 Protein; D016212:Transforming Growth Factor beta; C439971:COL3A1 protein, human; C497808:Smad7 protein, rat; C498862:Acta2 protein, rat