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H. Yang, X. Yang, E. Chaum; Transgenic IGF–1 Gene Expression and the Extracellular Matrix Substrate Modify the Expression of IGF Binding Proteins in the Human Retinal Pigment Epithelium. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):704.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have previously demonstrated that the IGF binding protein (IGFBP) gene family is ubiquitously expressed in explanted human retinal pigment epithelial (RPE) cells. The purpose of these studies is to determine the role of IGF–1 signaling on the expression pattern of IGFBPs and to determine whether the tissue culture substrate affects IGFBP expression in the RPE. Methods:Naive explanted human RPE cells (RPE–8) and IGF–1–transduce RPE–8 cells with low (clone 49), intermediate (clone 14) or high (clone 62) levels of expression of a biologically active IGF–1 transgene were cultured in serum–free media in 6–well plastic plates coated with fibronectin, laminin, Matrigel, collagen IV, collagen V, elastin or hyaluronic acid substrate. After reaching maximal confluence, the cells were refed and grown for 72–hours, after which, the media was collected. Secreted IGFBPs in the media were quantified using ELISA assays. Results: The level of secreted IGFBP–3 protein was substantially reduced in transgenic IGF–1 clones, compared to controls. There was a dose–dependent decrease in the secretion of IGFBP–3 in all three IGF–1 transduced cell lines (P<0.05). The observed IGFBP–3 secretion by IGF–1 transduced clones was independent of the ECM substrates on which the cells were grown. Our studies also demonstrated that the amount of IGFBP–3 secretion is significantly decreased in the presence of ECM substrates, compared with culture on plastic. Conclusions: Transgenic expression of IGF–1 influences the secretion of IGFBP–3 in human RPE cells. The increased level of transgenic expression of IGF–1 down–regulates the expression of IGFBP–3 in a dose–dependent fashion. ECM substrates also alter the expression of IGFBP–3, decreasing IGFBP–3 protein expression relative to culture on plastic. Possible mechanisms of this effect are discussed.
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