title: Indocyanine green concentrations used in chromovitrectomy cause a reversible functional alteration in the outer blood-retinal barrier.
abstract: OBJECTIVE
  To assess tight junction integrity in cultured human foetal retinal pigment epithelium (RPE) after exposure to clinically relevant indocyanine green (ICG) concentrations.
  
  
  METHODS
  Human foetal RPE was cultured with the Hu & Bok method. The apical compartments of well-differentiated cultures were exposed to 0.125, 0.05 and 0.025 mg/ml ICG with or without 10-min illumination. Vehicle and trypsin/EDTA or EDTA alone served as controls. Three minutes was chosen to mimic surgical exposure time, while 3 h was used for toxicity assays, with subsequent wash out. Cell-cell junctions were studied before and after exposure by phase contrast microscopy and immunofluorescence (ZO-1). Blood-retinal barrier function was measured through transepithelial electrical resistance (TER).
  
  
  RESULTS
  At 6-8 weeks postconfluence, RPE had grown into pigmented hexagonal monolayers with stable TER (435-1227 Ω*cm(2) ). After 3 min ICG exposure, cell morphology remained unchanged, with patchy cell-cell dissociation in positive controls. A continuous ZO-1 signal was detected in ICG groups, whereas trypsin controls showed patchy loss of the tight junction stain. TER had dropped at 1.5 h after 3 min exposure to 22.8 ± 3.1%, compared with 10.2 ± 3.9% in positive controls. Surgical light illumination did not affect TER. After 3 h exposure to 0.05 mg/ml ICG, TER decreased to 58.1 ± 8.3%, while vehicle controls maintained similar levels as prior to exposure (92.7 ± 2.4%). TER recovered in all ICG groups to prior levels within 3 days.
  
  
  CONCLUSIONS
  Indocyanine green (ICG) exposure induced a transient decrease in transepithelial electrical resistance, despite unaltered tight junction structure.
authors.affiliation: Department of Ophthalmology, University of Bonn, Bonn, Germany.
authors.forename: Zengping
authors.initials: Z
authors.lastname: Liu
authors.forename: Carsten H
authors.initials: CH
authors.lastname: Meyer
authors.forename: Rolf
authors.initials: R
authors.lastname: Fimmers
authors.forename: Boris V
authors.initials: BV
authors.lastname: Stanzel
mesh_terms: D001813:Blood-Retinal Barrier / Q000502:physiology*; D002478:Cells, Cultured; D004396:Coloring Agents / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D017097:Electric Impedance; D019084:Fluorescent Antibody Technique, Indirect; D005865:Gestational Age; D006801:Humans; D007208:Indocyanine Green / Q000633:toxicity*; D008858:Microscopy, Phase-Contrast; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism; D014019:Tissue Donors; D014821:Vitrectomy; D062826:Zonula Occludens-1 Protein / Q000378:metabolism
chemical_list: D004396:Coloring Agents; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D007208:Indocyanine Green
keywords: blood-retinal barrier; cell culture; chromovitrectomy; indocyanine green; retinal pigment epithelium; tight junctions; transepithelial electrical resistance