Increase in Matrix Metalloproteinase-2 Level in the Chicken Retina after Laser Photocoagulation

Background and Objective: We investigated the levels of matrix metalloproteinase-2 (MMP-2), which has been implicated in various vitreoretinal diseases, in the retina after laser photocoagulation (LPC). Materials and Methods: The time course of MMP-2 expression in 2-day-old chicken retinas before and 6 hours, 12 hours, 1 day; 2 days, 4 days, 8 days, 16 days, and 32 days after LPC was determined by real-time PCR and gelatin zymography. The basal level of MMP-2 in the retina and vitreous was also measured by gelatin zymography. MMP-2 localization in the retina was examined by 1 immunohistochemistry. The localization of MMP-2 mRNA was determined by fluorescent in situ hybridization. The internal limiting membrane (ILM) was observed by scanning electron microscopy. Results: MMP-2 mRNA expression in the retina peaked at day 4, but gelatin zymography showed that MMP-2 peaked 6 hours after LPC and the significant increase in the level of active MMP-2 lasted for more than 4 days. The concentration of MMP-2 in the vitreous was significantly higher than that in the retina. A distinct MMP-2 signal around the ILM was identified 6 hours after LPC, but MMP-2 mRNA was not detected there. Electron microscopy showed a damaged retinal surface after LPC. Conclusion and Outlook: The significant increase in retinal MMP-2 which lasted for more than 4 days after LPC may be induced by influx from the vitreous into the retina. This MMP-2 dynamics may contribute to pathological processes in the retina after LPC. Lasers Surg. Med. 42:433-441, 2010. (C) 2010 Wiley-Liss, Inc.