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C. Dot, F. Behar, D. BenEzra, L. Jonet, B. Goldenberg, E. Picard, S. Camelo, H. ElChehab, A. Le Corre, J.-C. Jeanny; Age as an Independent Factor in Experimental Laser Induced Choroidal Neovascularization in C57bl/6j Mice. Invest. Ophthalmol. Vis. Sci. 2009;50(13):786.
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To analyse the influence of age on retinochoroidal wound healing processes and on glial, growth factor and cytokine mRNA expression profiles observed after argon laser photocoagulation (PC).
The present study was divided in cellular and molecular phases. For the cellular study, 10-12 weeks old mice (group I, n= 14) and 1 year old mice (group II, n= 14) were used. All mice in these groups underwent a standard argon laser photocoagulation (50µm, 400mW, 0.05sec). Two separated lesions were created in each retina using a slit lamp delivery system. At 1, 3, 7, 14, 60 days and 4, 6, 7 and 8 months after photocoagulation, one or two mice from each group were sacrificed by carbon dioxide inhalation. At each time point the eyes were enucleated, mounted in Tissue tek (OCT), snap frozen and processed for immunohistochemistry or flat mounted. For the molecular study (RT-PCR) of gene expression changes, ten laser burns (50µm, 400mW, 0.05sec) were delivered to each retina in young adult mice (group III, n=10) and old mice (group IV, n=10). Retinal and choroidal tissues from these treated mice were collected at 16 hours, and 1, 2, 3 and 7 days after PC. Two mice of each group did not receive photocoagulation and were used as controls. RT-PCR was performed for GFAP, VEGF, and MCP-1.
In the cellular study, CNV reaction within the first 14 days after PC, was statistically larger in the oldest group of mice (group II), with p=0.0049 and p<0.0001 between groups I and II on slide sections and on flat mounts respectively. At 4 months after photocoagulation, the CNV surface (on slide sections) was 1282 µm²+/- 90 for group I and 2999 µm² +/- 115 for group II (p<0.0001). RT-PCR showed different mRNA expression profiles with aging. In old mice, GFAP mRNA expression was significantly higher before PC. After treatment, this mRNA had a peak of expression at 16-24h and on day 7 decreasing thereafter. VEGF mRNA expression was markedly increased after PC in old mice eyes reaching 2.7 times its basal level at Day 3 versus 1.3 in young mice. MCP-1 mRNA expression was always higher than its basal level in old mice during the first week after PC, reaching two peaks at 16h and Day3.
Older mice demonstrate more extensive CNV formation and a slower pace of regression after laser photocoagulation. These observations which are also accompanied by differences in growth factors and cytokine expression profiles may provide some insight into possible therapeutic strategies in the future.
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