title: Pigment epithelium-derived factor decreases outflow facility.
abstract: OBJECTIVE
  Pigment epithelium-derived factor (PEDF) regulates blood-retinal barrier function. As a constituent of aqueous humor, the role of PEDF in conventional outflow function is unknown. The goals of the study were to examine the effects of PEDF on barrier function of cultured Schlemm's canal (SC) endothelia and outflow facility in mouse eyes in situ.
  
  
  METHODS
  To model the inner wall of SC, transendothelial electrical resistance (TEER) of human SC and porcine angular aqueous plexus (AAP) cells was monitored. To examine an intact conventional outflow pathway, enucleated eyes from culled C57BL/6 mice were perfused with PEDF using a computer-controlled system. Purified PEDF (0.1 and 1 μg/mL) was perfused at four different pressure steps (4, 8, 15, 20 mm Hg), measuring flow to determine outflow facility (slope of flow/pressure relationship).
  
  
  RESULTS
  Pigment epithelium-derived factor increased TEER of porcine AAP cells in a dose-dependent fashion (0.3-3 μg/mL), and 1 μg/mL recombinant PEDF or conditioned media from pigmented retinal pigment epithelial monolayers stabilized TEER of human SC monolayers over time (0-48 hours). In perfusion experiments, we observed a 43.7% decrease in outflow facility (0.016 vs. 0.029 μL/min/mm Hg, P = 4.5 × 10⁻⁵) in eyes treated with 1 μg/mL PEDF compared to vehicle-perfused controls, and a 19.9% decrease (0.021 vs. 0.027 μL/min/mm Hg, P = 0.003) at 100 ng/mL PEDF.
  
  
  CONCLUSIONS
  Pigment epithelium-derived factor increased barrier function in both the in vitro and in situ models of the inner wall of SC. Modification of PEDF signaling in SC cells may be therapeutically exploited to increase outflow facility in people with ocular hypertension or decrease outflow facility in those with hypotony.
authors.affiliation: Department of Ophthalmology, Duke University, Durham, North Carolina.
authors.forename: Morgan E
authors.initials: ME
authors.lastname: Rogers
authors.forename: Iris D
authors.initials: ID
authors.lastname: Navarro
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Perkumas
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Niere
authors.forename: R Rand
authors.initials: RR
authors.lastname: Allingham
authors.forename: Craig E
authors.initials: CE
authors.lastname: Crosson
authors.forename: W Daniel
authors.initials: WD
authors.lastname: Stamer
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000502:physiology*; D001813:Blood-Retinal Barrier / Q000502:physiology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004727:Endothelium / Q000378:metabolism / Q000648:ultrastructure; D005136:Eye Proteins / Q000378:metabolism*; D005260:Female; D005901:Glaucoma / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008855:Microscopy, Electron, Scanning; D009414:Nerve Growth Factors / Q000378:metabolism*; D015843:Serpins / Q000378:metabolism*; D013552:Swine; D014129:Trabecular Meshwork / Q000378:metabolism* / Q000648:ultrastructure; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D005136:Eye Proteins; D009414:Nerve Growth Factors; D015843:Serpins; D000099174:Pigment Epithelium-Derived Factor
keywords: PEDF; Schlemm's canal; VEGF; aqueous humor; glaucoma; growth factors; outflow facility; trabecular meshwork
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