Systemic and Local Lipids in Nonhuman Primates With Drusen and Age-Related Maculopathies

Lipids are a principal component of drusen and are involved in the pathobiology of age-related macular degeneration (AMD). Nonhuman primates (NHPs) develop macular drusen and may provide insight into circulating or local lipids in AMD.

We evaluated aged rhesus macaques by fundus photography, optical coherence tomography (OCT), and fundus autofluorescence, as well as measured fasting plasma glucose, total cholesterol, high- and low-density lipoproteins, triglycerides, and apolipoprotein (Apo) A1, B, CIII, and E. Retinal tissues were collected for electron microscopy and immunostained for oil red O, ApoE, and ApoB.

Among 203 adult macaques (mean age 19.1 ± 3.1 years), 25 animals (12.1%) exhibited soft drusen with sub-RPE deposits, while 59 (28.6%) had yellow punctate dots that were mostly hyperautofluorescent without RPE elevation on OCT. Drusen prevalence increased with older age (P = 0.001) but not with plasma lipids (P > 0.05 for all), while the punctate dot phenotype was associated with older age (P = 0.014), higher fasting glucose (P = 0.023), low-density lipoprotein cholesterol (P = 0.022), and ApoB (P = 0.017). Ultrastructure revealed NHP drusen consisting of extracellular sub-RPE lipid particles, whereas punctate dots appeared to correspond to individual RPE cells with intracellular lipid vacuoles. Both sub-RPE and intra-RPE lipids of the two phenotypes contained neutral lipids and ApoE, while ApoE and ApoB appeared to be expressed in RPE.

In rhesus macaques, soft drusen are extracellular lipid deposits associated with older age, while punctate dots are intracellular lipids linked to age, hyperglycemia, and hyperlipidemia, suggesting differential dysregulation of lipid transport in these NHP models of AMD.