Gene Expression Changes during Human Retinal Pigment Epithelial Cell/Monocyte Interaction

Abstract

Abstract: : Purpose: To examine changes in gene expression of human retinal pigment epithelial (RPE) cells as a result of direct interaction with monocytes. In several ocular diseases, including age-related macular degeneration (AMD), there is evidence for monocyte infiltration. Monocytes and monocyte-derived cytokines may modulate RPE functions including cell proliferation and inflammatory response. Methods: Human RPE cells were isolated from a donor and co-cultured with monocytes for 4- and 24-hours. Human U-133A GeneChips and custom cDNA slides were hybridized with RNA from the unexposed cultures (control) and those co-cultured with monocytes for 4- and 24-hours. Data were analyzed using Affymetrix Microarray Suite, Data Mining Tool, and Spotfire. Results: Approximately 50% of the genes on Affymetrix U-133A GeneChip hybridized with RNA from cultured human RPE cells. Comparison of the unexposed cultures with 4- and 24-hours co-cultures identified approximately 45 genes that were up- or down-regulated as a result of RPE-monocyte interaction. Among these are Interleukin 8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), which were up-regulated several folds after 4-hours. IL-8 expression remained high even in the 24-hours co-cultures, while MCP-1 levels were reduced to the basal level in 24-hours co-cultures. Conclusions: Our results suggest that the interaction between human RPE and monocytes leads to the production of chemokines, such as IL-8 and MCP-1, by RPE. Furthermore, the expression of genes involved in immune response and cell-signaling pathways was altered in a time-dependent manner as a result of RPE-monocyte interaction. These studies should lead to a better understanding of the role of monocytes in the pathogenesis of ocular disorders, such as AMD.

Keywords: retinal pigment epithelium • gene microarray • age-related macular degeneration