title: Nerve growth factor promotes corneal epithelial migration by enhancing expression of matrix metalloprotease-9.
abstract: OBJECTIVE
  Nerve growth factor (NGF) is a neuropeptide essential for the development, survival, growth, and differentiation of corneal cells. Its effects are mediated by both TrkA and p75 receptors. Clinically relevant use of NGF was introduced to treat neurotrophic ulcerations in patients. Herein, we examine the mechanisms by which NGF enhances epithelial wound healing both in vivo and in vitro.
  
  
  METHODS
  An animal model using adult hens was implemented for the in vivo experiments. Laser ablation keratectomy was performed and animals were observed for up to 7 days. Epithelial healing was measured with fluorescein. In addition, proliferation was measured using BrdU incorporation and both TrkA and matrix metalloprotease-9 (MMP-9) expression were measured by immunohistochemistry (IHC) and Western blot (WB). In vitro experiments were carried out with telomerase-immortalized human corneal epithelial cells (HCLE). The rate of proliferation was measured using a colorimetric assay and BrdU incorporation. Real-time migration was evaluated with an inverted microscope. MMP-9 expression was evaluated by immunocytochemistry (ICC), WB, zymography, and RT-PCR. Finally, beta-4 integrin (β4) expression was assessed by ICC and WB.
  
  
  RESULTS
  Faster epithelial healing was observed in NGF-treated corneas compared with controls (P < 0.01). These corneas showed increased proliferation, TrkA upregulation, and enhanced MMP-9 presence (P < 0.01). In vitro, faster spreading and migration were observed in response to NGF (P < 0.01). Enhanced proliferation, as well as enhanced TrkA and MMP-9 expression, and decreased β4 levels were observed after adding NGF (P < 0.01).
  
  
  CONCLUSIONS
  NGF plays a major role during the epithelial healing process by promoting migration, a process that is accelerated by cell spreading. This effect is mediated by both the upregulation of MMP-9 and cleavage of β4 integrin.
authors: Duke Eye Center, Duke University, Durham, NC 27705, USA. tomas.blanco@duke.edu
authors: Tomas
authors: T
authors: Blanco-Mezquita
authors: Carmen
authors: C
authors: Martinez-Garcia
authors: Rui
authors: R
authors: Proença
authors: James D
authors: JD
authors: Zieske
authors: Stefano
authors: S
authors: Bonini
authors: Alessandro
authors: A
authors: Lambiase
authors: Jesus
authors: J
authors: Merayo-Lloves
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002645:Chickens; D003320:Corneal Ulcer / Q000188:drug therapy* / Q000378:metabolism; D004195:Disease Models, Animal; D019573:Epithelium, Corneal / Q000187:drug effects* / Q000293:injuries; D005260:Female; D007150:Immunohistochemistry; D039663:Integrin beta4 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D020932:Nerve Growth Factor / Q000494:pharmacology*; D011897:Random Allocation; D014945:Wound Healing / Q000187:drug effects*
chemical_list: C059834:ITGB4 protein, human; D039663:Integrin beta4; D020932:Nerve Growth Factor; D020780:Matrix Metalloproteinase 9
keywords: MMP-9; NGF; TrkA; corneal epithelium migration; corneal epithelium proliferation
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