Lack of Pnpla2 Accelerates Progression of AMD-Like Features in Mice

Lipid accumulation in the retinal pigment epithelium (RPE) contributes to cellular stress and progression of age-related macular degeneration (AMD). However, the regulation of lipid homeostasis in AMD development is not fully elucidated. The study investigates the effects of Pnpla2 deletion, a gene involved in lipid regulation, on key markers of RPE senescence and aging with potential relevance to AMD.

RPE flat mounts and retinal cryosections were analyzed from Pnpla2-/- and Pnpla2+/+ mice aged 3 months. Senescence-associated β-galactosidase (SA-β-gal) activity was assessed in flat mounts. DAPI was used to quantify RPE cells with single or multiple nuclei. Immunohistofluorescence was carried out to assess RPE tight junctions and expression of senescence and AMD markers using antibodies to zonula occludens 1 (ZO-1), phospho-histone (P-γ-H2AX), apolipoprotein E (ApoE), and high mobility group box 1 (HMGB1). Fundus imaging was acquired, and electroretinography (ERG) assessed visual function.

Pnpla2-/- RPE exhibited increased SA-β-gal activity, multinucleation of the population, and the translocation of HMGB1 from nucleus to cytoplasm, indicative of cellular senescence. Tight junctions were disrupted. The number of P-γ-H2AX-positive RPE cells increased by 50%, suggesting increased DNA damage. ApoE levels were elevated in Bruch's membrane and subretinal regions. At 3 months of age, attenuation of ERG c-wave amplitude was observed in both Pnpla2-/- and Pnpla2+/- mice. By 7 months of age, Pnpla2+/- mice exhibited continued attenuation of ERG c-wave amplitude and developed white spots.

Pnpla2 deficiency accelerates cellular features of RPE aging and generates AMD-like features. These findings underscore the importance of PNPLA2 in mitigating AMD progression and highlight its significance in retinal health and degeneration.