Mechanisms of FH Protection Against Neovascular AMD

Area of Science:

• Ophthalmology and Vision Science
• Immunology and Inflammation
• Genetics and Molecular Biology

Background:

• Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly.
• The complement factor H (FH) gene's common 402H allele is a major AMD risk factor.
• AMD pathogenesis involves vascular and inflammatory processes linked to complement alternative pathway (AP) deregulation.

Purpose of the Study:

• To investigate the functional role of FH in choroidal neovascularization (CNV), a key feature of neovascular AMD (nAMD).
• To determine if recombinant FH (recFH) can inhibit CNV and if the H402 risk variant impacts this function.
• To identify specific FH domains responsible for its effects on CNV and associated inflammation.

Main Methods:

• A murine model of CNV was used to mimic neovascular AMD.
• Intraocular administration of wild-type recFH, H402 risk variant recFH, and truncated FH variants.
• Assessment of CNV size, deposition of complement fragments (C3, MAC), and recruitment of microglia/macrophages.

Main Results:

• Intraocular recFH significantly reduced CNV, C3 fragment deposition, MAC formation, and immune cell infiltration, comparable to anti-VEGF therapy.
• recFH with the H402 risk variant showed no effect on CNV, establishing a causal link between this allele and disease etiology.
• The N-terminal region of FH (recFH1-7) mediated inhibition of CNV and inflammation, while the C-terminal region (recFH7-20) showed anti-angiogenic effects via thrombospondin-1 (TSP-1) upregulation.

Conclusions:

• FH plays a critical mechanistic role in regulating pathological neovascularization and inflammation in nAMD.
• The H402 risk variant of FH is functionally deficient in preventing CNV, underscoring its etiological significance.
• Targeting specific FH domains offers a potential therapeutic strategy for nAMD, distinct from current anti-VEGF treatments.