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 activation on AMD-like pathology using APOE/cfh-/- double transgenic mice. 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 cfh-/- transgenic mice to establish the APOE4/cfh-/- 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 that the ERGs of aged APOE4/cfh-/- mice on normal diet and on HFC display impaired visual function compared to APOE4 controls on normal diet. Histological review reveals that aged APOE4/cfh-/- mice on and off HFC diet display a similar number of basal deposits and degree of vacuolization as compared to APOE4 controls. However, RPE was more damaged in APOE4/cfh-/- mice than APOE4 controls, especially in mice fed a HFC diet.Analysis of complement components in plasma confirmed that there was less C3 and more C3b in APOE4/cfh-/- animals compared to APOE4 and APOE4/sCrry (which produces excess complement inhibition) controls.
Conclusions: :
These initial findings suggest that the effect of excess complement activation, modeling CFH loss-of-function, on an AMD-like murine model damages visual function. This supports the central importance of complement factor H in the pathophysiology of AMD and use of this animal model to study complement dysregulation in AMD.
Keywords: age-related macular degeneration • immunomodulation/immunoregulation • transgenics/knock-outs