Effects Of The Absence Of both Complement Factor H And Apolipoprotein E On Retinal Morphology In Mice

Abstract

Purpose: : Apolipoprotein E deficient mouse (apoE-/-), experimental model of genetic hypercholesterolemia, shows ultrastructural retinal alterations. Complement factor H (CFH) is involved in inflammatory process associated to retinal degenerations. We aimed to investigate the effect of the absence of CFH and apoE genes in mouse retinal pigment epithelium (RPE) and Bruch's Membrane (BM).

Methods: : Eight WT, 15 CFH-/-/apoE-/- (DKO) and 19 CFH+/-/apoE+/- (DH) mice older than 12 months were used (all mice were in C57BL6/J background). Light microscopy was performed to analyze the following morphological parameters in the retinal sections (Toluidine Blue). Apoptotic-like nuclei from the outer nuclear layer (ONL) were counted using AnalySIS software. The thickness of the whole retina and the outer nuclear layer section were measured by ImageJ image processing program. Samples were also processed for Transmission Electron Microscopy (TEM) visualization. For comparisons after a significant ANOVA among groups, post-hoc tests were applied (SPSS v.15.0).

Results: : Apoptotic-like nuclei were significantly higher (p<0.001) among WT and genetically modified groups (p<0.001) and between DKO and DH groups (p<0.05). However, no differences were found for ONL and total retina among groups. In the TEM visualization structural abnormalities were found in DKO mice compared to WT. BM appeared swelled and with vacuoles were shown inside the membrane. Moreover, basal laminar deposits were observed in genetically modified groups whereas in the RPE electrodense and electrolucent vacuoles, phagosomes and swelling of interdigitations could be found in genetically mice.

Conclusions: : These results show that the absence of CFH and apoE is involved in the development of RPE and BM morphological alterations and apoptosis of ONL cells. This animal model could be useful as a model of retinal degeneration.

Keywords: retina • Bruch's membrane