Function, Age-Related Expression and Molecular Characterization of PEDF, A Neurotrophic Serpin Secreted by Human RPE Cells

  • Joyce Tombran-Tink


The retinal pigment epithelium (RPE) is a highly specialized neuroepithelium that develops in advance of and lies adjacent to the neural retina where it plays a critical role in retinal homeostasis. RPE cells are multifunctional in nature and have been compared to machropages (Elner et al., 1981, Young and Bok, 1969), oligodendrocytes (Steinberg and Wood, 1974), astrocytes (Immel and Steinberg, 1986), melanocytes (Feeny-Burns, 1980) and hepatocytes (Bok 1985). The unique geography of this singled-celled epithelial layer allows it to establish a definitive blood-retinal barrier (Cunha-Vaz 1979) and to function as a transporting ang absorbing epithelium (Miller and Steinberg 1982; Misfeldt et al., 1976). In the vertebrate retina, a closed, extracellular microenvironment exists that is bounded by the apical membrane of RPE cells distally and photoreceptor inner segments and Muller cell processes proximally. Tight junctions effectively isolates if from most larger blood components and it is thought that most of the IPM components are synthesized by surroundings cells. This highly specialized matrix constitutes a novel conduit for the transfort nutrients, metabolites or trophic factors between the two cell layers and also facilities intercellular communication. Thus, analysis of the IPM is of importance because it contributes to our understanding of essentials aspects of retinal development, homeostasis and visual function. RPE cells from a functional complex with photoreceptor neurons of the retina and interacts with them through IPM. Cultured RPE cells synthesize and secrete several trophic factors including a photoreceptor-survival promoting factor (PSPA) (Hewitt et al., 1990), PDGF (Campochairo 1988), FGF (Plouet 1988), TGF-α (Fassio et al., 1988) and TGF-β (Connor et al., 1988).


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Copyright information

© Springer Science+Business Media New York 1995

Authors and Affiliations

  • Joyce Tombran-Tink
    • 1
  1. 1.Laboratory of Retinal, Cell and Molecular BiologyNational Institutes of Health, National Eye InstituteBethesdaUSA

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