title: In vitro phagocytosis of collagens by immortalised human retinal Müller cells.
abstract: OBJECTIVE
  This study is a first step to investigate phagocytosis of collagens by human retinal Müller cells, since Müller cells could be involved in remodelling of the vitreous and vitreoretinal interface in the human eye.
  
  
  METHODS
  Müller cells in culture were exposed to 2.0 microm fluorescent latex beads coated with BSA and human types I, II, and IV collagen and to non-coated beads for 2, 12, 24, and 48 h. To influence phagocytosis, cytochalasin B and anti-integrin subunits (alpha1, alpha2, and beta1) were added to the cells. Phagocytosis was evaluated by flow cytometry, transmission electron microscopy (TEM) and confocal microscopy.
  
  
  RESULTS
  Müller cells preferred to phagocytose beads coated with type II collagen compared with type IV collagen-, BSA- and non-coated beads. Phagocytosis of type I collagen-coated beads was intermediate. TEM and confocal microscopic evaluation confirmed phagocytosis of the beads. No significant differences were observed in phagocytosis of type II collagen-coated beads in the case of addition of cytochalasin B and anti-integrin subunits. Immunohistochemical analyses revealed that Müller cells were positive, under all tested circumstances, for vimentin and CRALBP. Less than 5% of the cells tested were GFAP positive.
  
  
  CONCLUSIONS
  Our observations demonstrate that human Müller cells in culture prefer to phagocytose type II collagen. In contrast, the phagocytosis of type IV collagen is comparable with the control coatings. We speculate that the relatively limited collagen phagocytosis by Müller cells supports a possible role for Müller cells in the slow process of vitreoretinal remodelling in adult human eyes.
authors.affiliation: Department of Ophthalmology, University of Groningen, University Medical Center Groningen, P.O. Box 30.001, 9700 RB, Groningen, The Netherlands. t.l.ponsioen@ohk.umcg.nl
authors.forename: Theodorus Leonardus
authors.initials: TL
authors.lastname: Ponsioen
authors.forename: Marja Johanna Adriana
authors.initials: MJ
authors.lastname: van Luyn
authors.forename: Roelofje Jacoba
authors.initials: RJ
authors.lastname: van der Worp
authors.forename: Ilja Maria
authors.initials: IM
authors.lastname: Nolte
authors.forename: Johanna Martina Maria
authors.initials: JM
authors.lastname: Hooymans
authors.forename: Leonoor Inge
authors.initials: LI
authors.lastname: Los
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D024042:Collagen Type I / Q000378:metabolism*; D024043:Collagen Type II / Q000378:metabolism*; D024141:Collagen Type IV / Q000378:metabolism*; D003571:Cytochalasin B / Q000494:pharmacology; D005347:Fibroblasts / Q000502:physiology; D005434:Flow Cytometry; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D016023:Integrins / Q000378:metabolism; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D008863:Microspheres; D009457:Neuroglia / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D012160:Retina / Q000166:cytology*; D014746:Vimentin / Q000378:metabolism
chemical_list: C020932:11-cis-retinal-binding protein; D002352:Carrier Proteins; D024042:Collagen Type I; D024043:Collagen Type II; D024141:Collagen Type IV; D005904:Glial Fibrillary Acidic Protein; D016023:Integrins; D014746:Vimentin; D003571:Cytochalasin B