Abstract
Purpose: :
There is strong evidence implicating local inflammation and complement dysregulation in AMD. Complement factor H (CFH) polymorphisms are the strongest genetic risk factor, but little is known about how risk is conferred. Since CFH is a known complement alternative pathway inhibitor, we studied the in vivo effects of excess complement inhibition on AMD-like pathology using APOE4/sCrry double transgenic mice. Similar to CFH, soluble complement receptor 1-related protein y (sCrry) is a homologue of human complement receptor 1 and a potent mouse complement inhibitor. Here, we analyzed whether this complement system manipulation worsened or ameliorated the APOE4 AMD-like phenotype.
Methods: :
The APOE4 murine model manifests an AMD-like phenotype in animals aged over 65 weeks and fed a high fat cholesterol-enriched (HFC) diet. Homozygous APOE4/APOE4 mice were crossed with sCrry transgenic mice to establish the APOE4/sCrry double transgenic line. Experimental animals were aged and fed a HFC diet. We used electroretinograms (ERGs), histology, immunohistochemistry, Western blots, C3a ELISA and C3 hemolysis assays to study the impact of complement cascade dysregulation.
Results: :
Preliminary results show there were no differences in ERGs between groups, but histological review showed that aged APOE4/sCrry+ animals have slightly less basal deposits and healthier retinal pigmented epithelium (RPE). Moreover, immunohistochemistry found less active C3b fragments in the sub-RPE of these animals when compared to APOE4/sCrry negative (-) littermates lacking sCrry. As expected with complement inhibition, biochemical analyses of plasma confirmed more C3 and less C3a in APOE4/sCrry+ animals on HFC diet compared to APOE4/sCrry- controls on HFC diet.
Conclusions: :
These initial findings suggest that the effect of excess complement inhibition, modeling CFH gain-of-function, on an AMD-like murine model is slightly protective. This supports the possibility that dysregulated excess complement activation may play a role in AMD disease pathogenesis and progression.
Keywords: age-related macular degeneration • immunomodulation/immunoregulation • transgenics/knock-outs