Abstract
Purpose :
Age-related macular degeneration (AMD) is a progressive blinding disease that affects the outer retina, retinal pigment epithelium (RPE), and choroid in people over age 55. Dysregulated lipid metabolism in the RPE, accumulation of lipid deposits on the Bruch’s membrane, and drusen formation are considered hallmark features of AMD. The metabolic reprogramming and resultant imbalance among production, usage, and transport of lipids in local tissues, especially in the RPE, has emerged as a pivotal driving force of AMD pathogenesis. However, the way in which RPE synthesizes and utilizes lipids is largely unknown. In our previous studies, we found that mice with RPE-specific knockout of the Tsc1 gene, which encodes an upstream inhibitor of mTORC1, had dysregulated lipid metabolism and accumulation of lipids in the RPE as well as in Bruch’s membrane. We also found that phosphatidate phosphatase Lipin1, a protein involved in triglyceride and phospholipid metabolism, was upregulated in the RPE with hyperactive mTORC1. The goal of the current study is to examine the role of Lipin1 in the maintenance of RPE and retina homeostasis using RPE-specific Lipin1 knockout mice.
Methods :
RPE-specific knockout was established by crossing Lipin1 flox/flox mice with C57BL/6-Tg(BEST1-cre)1Jdun/J mice. The prevalence of Cre expression in RPE tissue and knockout of Lipin1 was examined using immunostaining of RPE flat-mounts and western blot analysis. Visual function was measured using electroretinogram (ERG), retinal thickness using OCT, and visualization of the fundus using a Micron IV camera. Paraffin sections of the posterior eyes stained with hematoxylin and eosin were examined for pathological changes. Neutral lipid accumulation was examined on frozen sections of the posterior eyes.
Results :
Our results demonstrated that a deficiency of Lipin1 in the RPE was associated with an age-dependent decline of RPE function as measured by ERG c wave. Retinal dysfunction was observed at the age of 11 months, as measured by scotopic a and b-wave amplitudes. Fundus examination of the mice showed pigment changes and spots resembling cell infiltration indicative of AMD pathology. Lipid accumulation in the RPE was detected in the mice as early as 4 months old.
Conclusions :
Our current study demonstrates that Lipin1 plays regulatory roles in RPE lipid metabolism, and the loss of RPE Lipin1 disrupted RPE function and led to secondary retinal dysfunction.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.