Abstract
Purpose: :
Analyse the wound healing processes taking place following argon laser photocoagulation in eyes of C57Bl/6J mice during ageing.
Methods: :
C57Bl/6J mice of 4 and 6 weeks, 2 to 3 months, 6 months and 1 year old underwent a standard argon laser photocoagulation protocol. One or two burns (50µm, 400mW, 0.05sec) were delivered to each retina using a slit lamp delivery system and a cover glass as a lens. Burns (intensity 0.4) were performed on both sides of the papillae and 2 disc diameter away from it. Three animals of each group were sacrificed by carbon dioxide inhalation at 7 and 14 days and 2 and 4 months after photocoagulation. Enucleated eyes were mount in Tissue tek (OCT), snap frozen, cut and processed for immunohistochemitry. Specific antibodies against GFAP and von Willebrand factor were used respectively for labelling of astrocytes or activated Müller cells and vascular endothelial cells. DAPI staining was also carried out to localise the different nuclear layers. The size of the burn and the choroidal neovascularization were analysed by Visilog 6.2 software.
Results: :
Histology demonstrates a gradual posterior invagination of the retinal inner and outer nuclear layers towards the choroid and a rupture of Bruch’s membrane. The development of neovascularization is observed for all ages tested. Size of the interruption of Bruch’s membrane and pigmented epithelium increases with mouse age and time after photocoagulation. Choroidal neovasular area is very moderate for 4 weeks old mice at any time after photocoagulation. Regression of choroidal neovascularization begins 2 months after photocoagulation for 10 weeks old mice. After 4 months, neovascularisation has disappeared. For oldest mice, choroidal neovascularization decreases but is still present after 4 months. This regression of neovascularisation is faster and more important with young mice than old mice.
Conclusions: :
Argon laser allows the development of neovascularization in this model at all mice ages tested. The neovascular reaction is very moderate with young mice less than 6 weeks. Development and growth of neovascularization after photocoagulation changed during aging with more important lesion of RPE cells and slower regression of this neovascularization in aged group.
Keywords: choroid: neovascularization • age-related macular degeneration