title: Myofibroblast and extracellular matrix origins in proliferative vitreoretinopathy.
abstract: BACKGROUND
  To evaluate origins of the fibrocontractive cell populations and their relation to collagens I and II in proliferative vitreoretinopathy (PVR).
  
  
  METHODS
  Human PVR membranes were evaluated by indirect immunofluorescence for GFAP, cytokeratin-18 (CK-18), α-smooth muscle actin (αSMA), collagens I and II. Collagen expression by porcine Müller and retinal pigment epithelial cells (RPE) was evaluated using RT-PCR of RNA harvested from freshly isolated primary and proliferating cultures.
  
  
  RESULTS
  Collagen I was detected in all PVR samples and was widely distributed in the extracellular matrix. In contrast, collagen II was present in only two of the ten samples and was localized to thin, acellular bands near the border of the tissues. Using cell type-specific markers CK-18 and GFAP, RPE and glia were localized to the collagen I-rich matrices. Cells positive for GFAP and CK-18 can also co-express αSMA. Normal and proliferating RPE express collagen I, but Müller cells show no evidence of collagen I expression until they proliferate in culture. In contrast, normal RPE and Müller cells contain message for collagen II which is lost shortly after introduction into culture.
  
  
  CONCLUSIONS
  Collagen I appears to be the predominate fibrillar collagen in human PVR membranes and collagen II a comparatively minor component. Müller cells and RPE are physically associated with the collagen I matrix and are capable of expressing this protein suggesting that they are the origin. It also appears that the majority of myofibroblasts in PVR membranes are derived from either RPE or Müller cells suggesting that they play a major role in membrane development.
authors.affiliation: University of Alabama School of Medicine, Birmingham, AL, 35294, USA.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Feist
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: King
authors.forename: Robert
authors.initials: R
authors.lastname: Morris
authors.forename: C Douglas
authors.initials: CD
authors.lastname: Witherspoon
authors.forename: Clyde
authors.initials: C
authors.lastname: Guidry
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism*; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism*; D063928:Ependymoglial Cells / Q000378:metabolism / Q000473:pathology*; D005109:Extracellular Matrix / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D053538:Keratin-18 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D058628:Myofibroblasts / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000473:pathology*; D013552:Swine; D018630:Vitreoretinopathy, Proliferative / Q000378:metabolism / Q000473:pathology*
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D024042:Collagen Type I; D024043:Collagen Type II; D005904:Glial Fibrillary Acidic Protein; D053538:Keratin-18; D012333:RNA, Messenger