Effects of Chymase on the Macular Region in Monkeys and Porcine Müller Cells: Probable Involvement of Chymase in the Onset of Idiopathic Macular Holes

Abstract

Objectives: To investigate chymase involvement in idiopathic macular hole onset, the effects of chymase on monkey eyes and cultured Müller cells were investigated. Methods: Immunohistochemistry using antinestin and antiglial fibrillary acidic protein antibodies was performed in a normal monkey eye. After chymase was injected into the monkey vitreous, histological changes in the retina were evaluated using the TdT-mediated dUTP nick-end labeling (TUNEL) assay. Expression of c-kit, a stem cell factor receptor, and nestin was examined in porcine Müller cells cultured with basic fibroblast growth factor. The effects of chymase on proliferation and TUNEL staining in Müller cells were also examined. Results: The number of nestin and glial fibrillary acidic protein-positive cells was higher in the macula than in other regions. Thickening of the posterior hyaloid membrane and some apoptotic cells were found in the macula of chymase-treated eyes. The expression of c-kit and nestin in Müller cells was shown and enhanced when cultured with basic fibroblast growth factor. Exposure to chymase inhibited Müller cell proliferation and produced TUNEL-positive cells. Conclusions: There might be Müller cells possessing atypical properties near the macular region and chymase might cause fibrosis and apoptosis through these cells. These findings suggest that increased chymase activity may result in idiopathic macular hole onset.