Inhibition of migration but stimulation of proliferation of human retinal pigment epithelial cells cultured with uniform vesicles of silicone oil

Abstract

It has been hypothesized that emulsification of silicone oil might stimulate preretinal membrane formation and proliferative vitreoretinopathy. This study aimed to test the effects of vesicles of silicone oil (VSO), which were prepared by a novel membrane emulsification technique, on the migration and proliferation of human retinal pigment epithelial (hRPE) cells in vitro. VSO were produced by extrusion of the oil through a Supor membrane (Pall Life Sciences, Port Washington, NY, USA) with 0.45 microm pore size under a pressure of 0.1 MPa. hRPE cells were incubated with stained 25% VSO for 24 h to assess whether hRPE cells could phagocytize VSO. A wound-healing model was used by denuding cells from a glass slide to assess the migration of hRPE cells. The cells were then incubated with 25%, 50% and 100% VSO with or without serum for up to 72 h. The number of cells that had entered the denuded area was counted under a microscope. To assess the proliferative activity, the cells were incubated with 25%, 50% and 100% VSO, with or without serum, for 24 h. A total of 100 nuclei were examined for each slide, and the numbers of stained argyrophilic nucleolar organizer regions (AgNORs) in the nuclei were measured. The mean vesicle diameter of VSO prepared was 4.25 +/- 0.77 microm. The stained 25% VSO were phagocytized by hRPE cells. After the cells cultured with serum-free Dulbecco's Modified Eagle Medium (DMEM) were incubated with VSO, the numbers of migratory cells at higher concentrations (50% and 100%) of VSO were significantly decreased (48.9 +/- 5.37 and 10.6 +/- 3.03 respectively) compared to controls (69.9 +/- 9.88; P < 0.01). After the cells cultured with serum-free DMEM were incubated with VSO, the number of AgNORs in nucleus at 100% VSO was significantly increased compared to controls (3.1 +/- 0.72 vs 1.6 +/- 0.6; P < 0.01). The result indicated that VSO inhibited the migration but stimulated the proliferation of hRPE cells.