Abstract
Purpose :
Neovascular age-related-macular-degeneration (nAMD) is characterized by overgrowth of choriocapillaris which disrupt monolayer of retinal pigment epithelium. Signaling molecules that help to maintain local immune cell populations and regulate inflammation are considered to control nAMD. IRF5 is a transcriptional factor that controls macrophage maturation and turnover. When IRF5 is ablated genetically in mouse, the mouse eye shows spontaneous early stage of choroidal neovascularization(CNV) and reduction of mature macrophage. Here, we aim to investigate choroidal senescence as contributing factor towards nAMD in IRF5 null mice.
Methods :
Senescence markers, P16, P21, H2XA were assayed by qRT-PCR or immuno histochemistry of mouse choroid/RPE by comparing their expression levels in eye tissues of wildtype & IRF5 null mice of 6-9 month age. Expression of lineage specific markers of macrophage, CD11b, and angiogenic factors, VEGF was determined by immunohistochemistry. Lipid accumulation was examined by Bodipy-488 fluorescence. Subcellular structure for choroid and RPE were evaluated histologically using transmission electron microscopy.
Results :
Homozygous IRF5 null eyes show disruption in the Bruch’s membrane especially in the elastic layer and show presence of deposits in the collagenous layers. These changes are accompanied by an increased presence of immune cells /macrophages within or near Bruch’s membrane. Those macrophages display aging signs, such as numerous vacuoles, lipid in cytoplasm, condensed nuclei with thick layer of heterochromatin. In IRF5 null choroid, mRNA of senescence markers, CDKN2A (encoding p16ink4a) and CDKN1A (encoding p21) are elevated and CD11b positive immune cells expressing high levels of P16, P21, H2AX and VEGF, accumulating lipid deposits are increased.
Conclusions :
Loss of IRF5 induces senescence of macrophage in choroid of mice, which may drive the degenerative changes in the RPE and the Bruch’s membrane. IRF5 null eyes can serve as a model for studying aging related immune processes in nAMD pathogenesis and may help provide explanation for areas where neovascular tissues breach through the RPE monolayer.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.