Age-related macular degeneration-like phenotypic features develop at the early ages of Cxcr5/Nrf2 double knockout mice: An accelerated AMD model

Age-related macular degeneration (AMD) is a leading cause of blindness for older adults. The aim of this study is to develop an accelerated mouse model of AMD and characterize its phenotypic features. Cxcr5 knockout (KO) mice and Nrf2 KO mice were bred to create Cxcr5/Nrf2 double knockout (DKO) mice. AMD-like features in Cxcr5/Nrf2 DKO mice were compared with those in CXCR5 KO mice and C57BL6 wild-type (WT) controls. The assessment included fundus and optical coherence tomography (OCT) imaging, periodic acid-Schiff (PAS) and immunofluorescence staining of retinal pigment epithelium (RPE)-choroid flat mounts and sections. Stained samples were imaged with fluorescent microscopy, and Western blots were used to monitor protein expression changes. The staining of cleaved caspase-3, peanut agglutinin (PNA) lectin, and MAP2 was performed to assess the presence of retinal degeneration and cell apoptosis. Quantification with statistical analysis was performed with Graphpad software. The 2- 4-, and 6-month-old DKO mice exhibited increased hypopigmented spots on fundus and sub-RPE abnormalities on OCT as compared to the Cxcr5 KO mice, and C57BL6 WT controls. Aberrant RPE/sub-RPE depositions and increased Bruchs membrane (BM) thickness were demonstrated by PAS-stained sections. The DKO mice had strong autofluorescence (A2E) and increased RPE/sub-RPE depositions of IgG and AMD-associated proteins ({beta} amyloid, Apolipoprotein E, complement 5b-9, and B-crystallin). The protein expression of AMD-associated proteins and Transmembrane Protein 119 (TMEM119) microglia marker were upregulated at the RPE/BM/choroid complex of DKO mice. The adult DKO mice underwent accelerated retinal degeneration and cell apoptosis compared to the KO and the WT mice. Together, the data suggest that the Cxcr5/Nrf2 DKO mice develop significant AMD-like characteristics at an early age and may serve as an accelerated AMD model. Sumary StatementA new animal model is developed to mimic early AMD characteristics in adult mice