title: Human retinal pigment epithelium cells as functional models for the RPE in vivo.
abstract: OBJECTIVE
  The two most commonly used in vitro models of the retinal pigment epithelium (RPE) are fetal human RPE (fhRPE) and ARPE-19 cells; however, studies of their barrier properties have produced contradictory results. To compare their utility as RPE models, their morphologic and functional characteristics were analyzed.
  
  
  METHODS
  Monolayers of both cell types were grown on permeable membrane filters. Barrier function and cellular morphology were assessed by transepithelial resistance (TER) measurements and immunohistochemistry. Protein expression was evaluated by immunoblotting and ELISA assays, and retinoid metabolism characterized by HPLC.
  
  
  RESULTS
  Both cultures developed tight junctions. However, only the fhRPE cells were pigmented, uniform in size and shape, expressed high levels of RPE markers, metabolized all-trans retinal, and developed high TER (>400 Ωcm(2)). The net secretion of pigment-epithelium-derived factor (PEDF) was directed apically in both cultures, but fhRPE cells exhibited secretion rates a thousand-fold greater than in ARPE-19 cells. The net secretion of vascular endothelial growth factor (VEGF) was significantly higher in fhRPE cultures and the direction of this secretion was basolateral; while net secretion was apical in ARPE-19 cells. In fresh media, VEGF-E reduced TER in both cultures; however, in conditioned media fhRPE cells did not respond to VEGF-E administration, but retreatment of the conditioned media with anti-PEDF antibodies allowed fhRPE cells to fully respond to VEGF-E.
  
  
  CONCLUSIONS
  Properties of fhRPE cells align with a functionally normal RPE in vivo, while ARPE-19 cells resemble a pathologic or aged RPE. These results suggest a utility for both cell types in understanding distinct, particular aspects of RPE function.
authors.affiliation: Department of Ophthalmology, Medical University of South Carolina, SEI-Room 518E, 167 Ashley Avenue, Charleston, SC 29425, USA. ablonczy@musc.edu
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Ablonczy
authors.forename: Mohammad
authors.initials: M
authors.lastname: Dahrouj
authors.forename: Peter H
authors.initials: PH
authors.lastname: Tang
authors.forename: Yueying
authors.initials: Y
authors.lastname: Liu
authors.forename: Kumar
authors.initials: K
authors.lastname: Sambamurti
authors.forename: Alan D
authors.initials: AD
authors.lastname: Marmorstein
authors.forename: Craig E
authors.initials: CE
authors.lastname: Crosson
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D001681:Biological Assay / Q000379:methods*; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D005136:Eye Proteins / Q000378:metabolism; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D009414:Nerve Growth Factors / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology* / Q000502:physiology*; D012172:Retinaldehyde / Q000378:metabolism; D015843:Serpins / Q000378:metabolism; D019108:Tight Junctions / Q000502:physiology; D014212:Tretinoin / Q000378:metabolism / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014764:Viral Proteins / Q000494:pharmacology; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D000970:Antineoplastic Agents; D005136:Eye Proteins; D009414:Nerve Growth Factors; D012172:Retinaldehyde; D015843:Serpins; D014212:Tretinoin; D042461:Vascular Endothelial Growth Factor A; D014764:Viral Proteins; D000099174:Pigment Epithelium-Derived Factor; C084758:VEGF-like protein, Orf virus; C467484:VEGFA protein, human