Time-Dependent Changes of Cell Proliferation After Laser Photocoagulation in Mouse Chorioretinal Tissue

Abstract

PURPOSE: This study investigated the time course of cell proliferation after laser photocoagulation and analyzed the cell types of proliferating cells. METHODS: C57BL/6J mice received unilateral laser photocoagulation. Intraperitoneal bromodeoxyuridine (BrdU) injection was performed, and mice were divided into two groups according to the injection paradigm: group 1 with continuous injection and group 2 with periodic injection. Each group was again divided into four subgroups according to injection period: 0 to 3 days (n = 11), 0 to 7 days (n = 14), 0 to 14 days (n = 6), and 0 to 28 days (n = 6) after laser photocoagulation for group 1; and 0 to 3 days (n = 11), 4 to 7 days (n = 6), 8 to 14 days (n = 6), and 15 to 28 days (n = 6) after laser photocoagulation for group 2. The eyes were examined with immunohistochemistry using anti-BrdU antibody and other various antibodies for identification of proliferating cells. Manual cell counting and flow cytometry were performed for quantification. RESULTS: In group 1, the number of BrdU+ cells showed marked increase during the first 3 days of laser lesioning, reaching its maximum after 7 days (P < 0.05). Group 2 also demonstrated peak proliferation during the first 3 days, but a significantly reduced number of BrdU+ cells were detected during 4 to 7 days, 8 to 14 days, and 15 to 28 days of laser treatment (P < 0.05). BrdU+ cells colocalized with CD11b, F4/80, iba1, RPE65, CD31, and glial fibrillary acidic protein (GFAP) labeling, and CD11b+, F4/80+, and iba1+ cells constituted the main fraction of BrdU+ cells. CONCLUSIONS: Laser photocoagulation induced cell proliferation mostly during the first 3 days, and many proliferating cells were identified as inflammatory cells, RPE cells, endothelial cells, and Müller cells.