THE MESSENGER-RNA EXPRESSION OF CYTOKINES AND THEIR RECEPTORS IN CULTURED IRIS PIGMENT EPITHELIAL-CELLS - A COMPARISON WITH RETINAL-PIGMENTEPITHELIAL-CELLS

It has been suggested that human iris pigment epithelial (IPE) cells i solated from iridectomized tissue could be used as autologous cells fo r transplantation into the subretinal space in diseases with dysfuncti onal retinal pigment epithelium (RPE). RPE cells synthesize a number o f cytokines and their receptors which are important for its proper fun ction. Nearly nothing is known about the capacity of IPE to synthesize cytokines or responding to them. To compare the mRNA expression of 36 cytokines or their receptors in cultured adult IPE cells and RPE cell s we used semi-quantitative reverse transcription polymerase chain rea ctions (RT-PCR). Included in our assay were cytokines with known expre ssion in RPE to get a broad basis for comparing IPE cells: basic fibro blast growth factor (bFGF or FGF-2), and one of its receptor (FGFR-1), epidermal growth factor (EGF), and its receptor EGF-R, transforming g rowth factor beta (TGF beta), and its type III receptor TGF beta-R3, t he platelet-derived growth factors and receptors (PDGF A, PDGF B, PDGF -R alpha, PDGF-R beta), tumor necrosis factor alpha (TNF alpha), and t wo receptors TNF-R1 and TNF-R2, insulin (INS) with receptor INS-R, ins ulin-like growth factors (IGF1, IGF2), and receptors (IGF-1 R, IGF2-R) , vascular endothelial growth factor (VEGF), and two receptors (VEGF-R 1 or FLT-1 and VEGF-R-2 or FLK-1), the receptor for VEGF-C: VEGF-R3 or FLK-4, interleukin 6 (IL6), and its receptor (IL6-R), nerve growth fa ctor (NGF), interleukin 1 alpha (IL1 alpha), and a receptor (IL1-R). I n addition, cytokines or their receptors not known to be expressed in RPE were included to widen our picture of cytokine gene expression in the eye: stem cell factor (SCF), its receptor (SCF-R), low-affinity ne rve growth factor receptor p75 (p75(NGF-R), ciliary neutrothropic fact or (CNTF), and its receptor (CNTF-R), glycoprotein 130 interleukin 6 t ransducer (gp130 (IL6-SD), leukemia inhibitory factor (LIF), and its r eceptor (LIF-R). Semiquantitative expression data were obtained using series of fivefold dilutions of each cDNA and a fixed number of PCR cy cles. The expression of RPE 65, glyceraldehyde-3-phosphate dehydrogena se (GAPDH), and beta 2-microglobulin (B2MG) was used as a control for cellular origin, RNA quality and PCR conditions. With the exception of insulin and tumor necrosis factor alpha all other cytokines analysed and their receptors were expressed in both IPE and RPE cells, even tho ugh the levels varied. No qualitative or quantitative difference were observed in the mRNA expression level of 34 (94%) of the cytokines or receptors between IPE and RPE. In contrast, the mRNA expression level of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 [VEGF-RS (FLK-1)] was lower in TPE than in RP E cells. As an increased expression of VEGF in the RPE in maculae with age-related macular disease could be involved in its pathogenesis, a decreased expression of angiogenic growth factors in IPE cells could p ossibly be beneficial for the therapy of age-related maculopathy if in deed other tasks of nonfunctional RPE cells could be performed by IPE cells. The similarity of the mRNA expression pattern in 94% of the cyt okines analyzed supports the assumption that IPE cells potentially can perform functions of RPE cells in the appropriate environment. (C) 19 98 Academic Press.