title: Astrocytes increase barrier properties and ZO-1 expression in retinal vascular endothelial cells.
abstract: OBJECTIVE
  Diabetic retinopathy and other diseases associated with retinal edema are characterized by increased microvascular leakage. Astrocytes have been proposed to maintain endothelial function in the brain, suggesting that glial impairment may underlie the development of retinal edema. The purpose of this study was to test the effects of astrocytes on barrier properties in retinal microvascular endothelial cells.
  
  
  METHODS
  Bovine retinal microvascular endothelial cells were exposed to conditioned media from rat brain astrocytes. Transendothelial electrical resistance (TER) was determined on 24-mm Transwell (Cambridge, MA) polycarbonate filters with the End-Ohm device (World Precision Instruments, Sarasota, FL). ZO-1 protein content was quantified by microtiter enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Astrocyte-conditioned medium (ACM) significantly increased TER (P < 0.0001) and ZO-1 content (P < 0.01). Both serum-containing and serum-free N1B defined ACM increased ZO-1 expression, but heating abolished the effect. Serum-free ACM decreased cell proliferation by 16%.
  
  
  CONCLUSIONS
  Astrocytes release soluble, heat-labile factors that increase barrier properties and tight junction protein content. These results suggest that astrocytes enhance blood-retinal barrier properties, at least in part by increasing tight junction protein expression. Our findings suggest that glial malfunction plays an important role in the pathogenesis of vasogenic retinal edema.
authors.affiliation: Department of Ophthalmology, Penn State University College of Medicine, Milton S. Hershey Medical Center, Hershey 17033, USA.
authors.forename: T W
authors.initials: TW
authors.lastname: Gardner
authors.forename: E
authors.initials: E
authors.lastname: Lieth
authors.forename: S A
authors.initials: SA
authors.lastname: Khin
authors.forename: A J
authors.initials: AJ
authors.lastname: Barber
authors.forename: D J
authors.initials: DJ
authors.lastname: Bonsall
authors.forename: T
authors.initials: T
authors.lastname: Lesher
authors.forename: K
authors.initials: K
authors.lastname: Rice
authors.forename: W A
authors.initials: WA
authors.lastname: Brennan
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000502:physiology*; D001813:Blood-Retinal Barrier / Q000502:physiology*; D002417:Cattle; D002455:Cell Division; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D004553:Electric Conductivity; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000096:biosynthesis*; D010750:Phosphoproteins / Q000096:biosynthesis*; D051381:Rats; D012171:Retinal Vessels / Q000378:metabolism*; D019108:Tight Junctions / Q000502:physiology; D062826:Zonula Occludens-1 Protein
chemical_list: D017077:Culture Media, Conditioned; D008565:Membrane Proteins; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein