Abstract
Purpose :
A common polymorphism in complement factor H (CFH) that switches a tyrosine at position 402 to a histidine is linked to susceptibility to developing age-related macular degeneration (AMD), and other less common variants of CFH are associated with higher penetrance early onset forms of the disease. In the retina, the retinal pigmented epithelium (RPE) is the major site of CFH expression. The purpose of this study was to characterise the retinal phenotype of RPE-specific Cfh knock-out (KO) mice using the Best-Cre and Trp1-Cre strains as drivers, and investigate complement homeostasis in the retina of these mutant strains.
Methods :
mRNA was extracted from the RPE of wild type (WT) and Cfh Best1-Cre KO at age 5 months. Changes in gene expression levels were tested by qRT-PCR for CFH, C3, C5, C3aR, C5aR, CFI, CFB, CFD and CFP. Retinas were isolated from WT, Cfh Best1-Cre KO and Cfh Trp1-Cre mice and retinal morphology was assessed using toluidine blue-stained fixed frozen sections. Neuroretinal whole mounts were stained with collagen IV to visualize retinal vessels and GFAP for microglia/astrocytes. RPE whole mounts and fixed frozen sections were stained for C3 and the C3 breakdown products C3b, iC3b and C3c.
Results :
qRT-PCR confirmed the absence of CFH mRNA in the RPE of Cfh Best1Cre KO strain. Retinal vasculature and microglia/astrocyte staining appeared normal in the mutant strains but the Cfh Trp1-Cre mice exhibited sporadic staining of C3 and iC3b on photoreceptor outer segments.
Conclusions :
The presence of FH in the RPE-choroid is important for complement homeostasis in the mouse retina. Collagen IV and GFAP staining of neuroretinal whole mounts appeared normal in WT and Cfh knock-out mice. Retinal fixed frozen sections staining for C3 and the C3 breakdown products C3b, iC3b, C3c showed sporadic staining of both C3 and C3b, iC3b, C3c in Cfh Trp1-Cre mice compared to age matched wild types (WT).
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.