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  • Title: TGF beta secretion modulates the density-dependent growth of pig retinal pigment epithelium in vitro.
    Author: Tezel TH, Del Priore LV.
    Journal: Ophthalmic Res; 1999; 31(3):192-202. PubMed ID: 10224502.
    Abstract:
    BACKGROUND: We aimed to identify the cytokine(s) responsible for the density-dependent growth regulation of pig retinal pigment epithelium (RPE) in vitro. METHODS: Confluent monolayers of primary pig RPE were established on bovine corneal endothelial extracellular matrix-coated tissue culture well inserts wrapped with dialysis membranes with different molecular weight cutoffs (0.5-50 kDa). These confluent RPE monolayers were then cocultured with first passage porcine RPE plated at a density of 1 cell/mm2, so that the newly plated RPE was bathed with different molecular weight fractions of the confluent cell media. Growth rates of the newly plated RPE were determined 72 h after plating and the molecular weight fraction of the confluent cell medium that inhibits the RPE proliferation was determined. First passage pig RPE (1 cell/mm2) were cocultured with confluent monolayers of primary pig RPE on inserts in the presence of different amounts of TGF-beta neutralizing antibody (0.1-100 microg/ml). Growth rates of the newly plated RPE were calculated 72 h after plating to determine the antibody concentration that would maximize the growth rate of the newly plated RPE in the presence of an adjacent confluent RPE monolayer. RESULTS: The growth rate of the newly plated RPE decreased when RPE were bathed with the 10- to 25-kDa fractions of medium from an adjacent confluent RPE monolayer. This growth inhibition reached statistical significance with the 25- to 50-kDa fractions (p < 0.05), and was abolished by adding pan-specific neutralizing antibody against TGF-beta (0.1-5 microg/ml). Blocking greater amounts of TGF-beta in the medium with higher doses of antibody (>10 microg/ml) also inhibited the growth of the newly plated RPE, in the presence or absence of a neighboring confluent cell layer. CONCLUSION: The TGF-beta family of cytokines mediates the density-dependent growth suppression of RPE in vitro. Neutralizing the effect of these cytokines by adding anti-TGF-beta antibodies can result in more rapid growth of the RPE in vivo.
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