Effect of Silica in the Manufacture of Autologous Serum Eye Drops on Corneal Stromal Cells

Abstract

Purpose: The aim of this study was to evaluate the effect of serum clot activator, silica (SiO2), which may be used for making autologous serum eye drops, on human corneal fibroblasts. Methods: Cultured human corneal fibroblasts were exposed to 10%, 20%, and 30% silica for 1, 6, and 24 hours; methyl thiazolyl tetrazolium–based colorimetric assay was performed to determine the survival rate of fibroblasts and lactate dehydrogenase leakage assay to assess the cytotoxicity. The apoptotic response was evaluated by flow cytometric analysis and fluorescence staining with Annexin V and propidium iodide. Cellular morphology was evaluated by inverted phase-contrast light microscopy and electron microscopy. Results: The survival rate of human corneal fibroblasts and cytotoxicity showed both dose-dependent and time-dependent responses. The fluorescent micrograph and flow cytometry showed that as the exposure time increased, more cells underwent apoptosis or necrosis after treatment with 30% silica. When observed with light and electron microscopy, the number of corneal fibroblasts decreased and they were more detached from the dish. In addition, damaged corneal fibroblasts showed degenerative changes after exposure to 30% silica. Conclusions: Silica showed dose-dependent and time-dependent toxicity in human corneal fibroblasts. It is safer to keep the blood in tubes without a clot activator when manufacturing autologous serum eye drops to prevent possible corneal cytotoxicity.