title: The role of gremlin, a BMP antagonist, and epithelial-to-mesenchymal transition in proliferative vitreoretinopathy.
abstract: OBJECTIVE
  Proliferative vitreoretinopathy (PVR), a major reason for failure of retinal detachment surgery, is characterized by the formation of scarlike tissue that contains transdifferentiated retinal pigment epithelial (RPE) cells. The scar tissue occurs in response to growth factors such as transforming growth factor (TGF)-beta and epidermal growth factor (EGF). The authors postulate that transdifferentiation of RPE cells may arise via epithelial-to-mesenchymal transition (EMT). Bone morphogenetic proteins (BMPs) are expressed in the retina and have an antiproliferative role. Gremlin is expressed in the outer retina and is a BMP antagonist. The study was conducted to establish a model of PVR by inducing EMT in the human RPE cell line ARPE-19, using TGF-beta and EGF and to establish the contribution of gremlin to EMT.
  
  
  METHODS
  ARPE-19 cells were cultured and stimulated with TGF-beta1, EGF, and gremlin. The expression of alpha-smooth muscle actin (alpha-SMA), vimentin, and zona occludens (ZO)-1 were examined via PCR, Western blot analysis, and immunofluorescence. Zymography was performed for matrix metalloproteinase (MMP) activity. Scratch assays were performed to assess migration.
  
  
  RESULTS
  A model of EMT was established in the ARPE-19 cell line. The characteristics of EMT include gain of alpha-SMA, loss of ZO-1, upregulation of MMP activity and enhanced migration. Gremlin plays an important role in this process, contributing to the gain of alpha-SMA, loss of ZO-1, and upregulation of MMP activity.
  
  
  CONCLUSIONS
  EMT occurs in vitro in the ARPE-19 cell line in response to the growth factors TGF-beta1 and EGF. EMT is also induced by Gremlin.
authors.affiliation: Department of Ophthalmology, Mater Misericordiae Hospital, University College Dublin, Ireland.
authors.forename: Helena
authors.initials: H
authors.lastname: Lee
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: O'Meara
authors.forename: Colm
authors.initials: C
authors.lastname: O'Brien
authors.forename: Rosemary
authors.initials: R
authors.lastname: Kane
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors*; D002454:Cell Differentiation / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology*; D008954:Models, Biological; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D014746:Vimentin / Q000235:genetics / Q000378:metabolism; D018630:Vitreoretinopathy, Proliferative / Q000150:complications* / Q000473:pathology; D062826:Zonula Occludens-1 Protein
chemical_list: D000199:Actins; D015415:Biomarkers; D019485:Bone Morphogenetic Proteins; C486399:GREM1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; C569042:TJP1 protein, human; D053773:Transforming Growth Factor beta1; D014746:Vimentin; D062826:Zonula Occludens-1 Protein; D004815:Epidermal Growth Factor