Retinal phenotype of APOB100 transgenic mice on a Western diet with human-like hyperlipidemia and cholesterol crystals in the retina and choroid

lab animal Article https://doi.org/10.1038/s41684-026-01693-x Retinal phenotype of APOB100 transgenic mice on a Western diet with human-like hyperlipidemia and cholesterol crystals in the retina and choroid Check for updates Nicole El-Darzi1, Tim F. Dorweiler    2,3, Natalia Mast1, Julia Busik2 & Irina A. Pikuleva    1 Drusen and subretinal drusenoid deposits, the pathognomonic lesions for age-related macular degeneration (AMD), are rich in cholesterol. Yet, AMD is not consistently linked to plasma lipids. Here wild-type and human apolipoprotein B100-expressing (APOB100) mice were put on a Western type of diet for 13 months and then assessed for plasma lipid profile, high-density lipoprotein (HDL) heterogeneity, status of intraretinal and choroidal vasculatures, retinal structure, function, levels of cholesterol and other sterols, lipid and cholesterol distribution and expression of cholesterol-related genes. The dietary effects were more pronounced in APOB100 mice, which had human-like hyperlipidemia and different subpopulations of HDL3, than in wild-type mice. In addition, the APOB100 retina showed increased cholesterol input from the systemic circulation, higher cholesterol content, more cholesterol crystals, elevated expression of HDL-related genes, lipid accumulation in the retinal pigment epithelium and Bruch’s membrane, and impaired function compared with the wild-type retina. Remarkably, in both genotypes, cholesterol crystals were detected in the choroid, piercing toward Bruch’s membrane and leading to macrophage infiltration. Our data indicate how plasma lipid profile could be linked to AMD and that cholesterol crystals in the choroid should be further investigated as contributors to AMD development and progression. The neural retina (NR) is an extension of the brain that initiates the transmission of the visual signal1. The NR lines the back of the eye and is composed of different neuron types, which are organized in layers (Fig. 1a). The outermost layer of the NR consists of the photoreceptor cells, which form a complex with the apical side of the underlying monolayer of retinal pigment epithelium (RPE). The RPE’s basal side rests on Bruch’s membrane (BrM), a planar vessel wall, which separates the NR–RPE complex (often called the retina) from the choroid (Ch)2,3. The Ch mainly provides blood supply to the RPE and photoreceptors, and the remaining retina is served by the retinal vascular network4. The endothelial cells of retinal blood vessels are nonfenestrated and form tight junctions or the inner blood–retinal barrier, which prevents passage of plasma proteins 1 and lipoprotein particles (LPPs) into the NR. Conversely, the blood vessels of the Ch are fenestrated, and plasma macromolecules can reach the RPE, which has tight junctions and forms part of the outer blood–retina barrier. Yet, the RPE has various receptors on both of its sides (Fig. 1b), which mediate the selective exchange between the Ch and RPE as well as between the RPE and NR4,5. Age-related macular degeneration (AMD) is a leading cause of blindness in older individuals of industrialized countries6. AMD is a multifactorial disease with age, genetic factors, environment and lifestyle contributing to disease susceptibility and progression7. Early AMD stage is characterized by cholesterol-rich deposits accumulated external to the RPE: subretinal drusenoid deposits (SDDs) located apically to the RPE Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA. 2Department of Biochemistry and Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA. 3Present address: Department of Surgery, Harvard Medical School, Boston, MA, USA. e-mail: Lab Animal Article https://doi.org/10.1038/s41684-026-01693-x a b Inner blood– retinal barrier Muller cell Blood vessel lumen Endothelium HDLlike Pericyte Retina NR Intermediate vascular plexus Deep vascular plexus Apical side Retinal vascular network Superficial vascular plexus RPE Photoreceptors RPE ABCA1/ ABCG1 CD36 UC BrM APOB, MTTP SOAT1 Choroidal vascular network Outer blood– retinal barrier Tight junctions CD36 LDLR oxLDL LDL SR-BI SR-BII ABCA1, ABCG1 Basal side Fenestrated capillaries Ch BrM LPP HDL Fig. 1 | The retina and RPE. a, Schematic representation of the retina showing its overall structure, supporting vascular networks and blood–retina barriers. While only three plexi of the retinal vasculature are indicated as having the inner blood– retinal barrier, all blood vessels within the NR have this barrier. b, Schematic representation of a RPE cell showing various cholesterol-related proteins and receptors. See the main text for details. Panel a was licensed from Carlson Stock Art and is adapted from ref. 92 under a Creative Commons license CC BY 4.0. Panel b is adapted from ref. 26 under a Creative Commons license CC BY 4.0. CD36, cluster of differentiation 36; LDLR, LDL receptor; MTTP, microsomal TG transfer protein; oxLDL, oxidized LDL; SOAT1, sterol O-acyl-transferase 1; SR-BI and SRBII, scavenger receptor class B members I and II, respectively. (in the subretinal space between the photoreceptors and RPE) and/or drusen found basolaterally to the RPE in BrM8–12. As these extracellular deposits become larger, they ultimately lead to RPE atrophy, photoreceptor degeneration and, in some cases (10–15%), abnormal blood vessel growth (neovascularization) into the retina13–16. Several polymorphisms in the genes (CETP, LIPC, APOE and ABCA1) related to high-density lipoprotein (HDL) in the systemic circulation are risk factors for AMD17. Nevertheless, numerous studies did not find consistent associations between AMD and plasma lipid profiles7,18,19, leading to several explanations. First, plasma lipid profiles can be specific to the disease stage (early, intermediate or late) or disease type (non-neovascular or vascular) as AMD is a heterogeneous disease19. Second, AMD could be linked to a specific HDL subclass, as HDL particles are heterogeneous and may differ in their AMD risk-conferring properties7,18. Accordingly, small rodent models with blood content similar to that of humans are required to test these explanations and decipher the role of HDL and plasma lipid profile in AMD etiology and progression. Indeed, humans carry most of their blood cholesterol on low-density lipoprotein (LDL), whereas rodents carry it on HDL. Hence, the two species have very different absolute amounts and ratios between their LDL and HDL. In normolipidemic humans, the LDL/HDL ratio should not exceed 2.2 (<100/>45 mg/dL, Table 1)20, whereas in C57BL/6J mice and Golden Syrian hamsters, this ratio varies from 0.04 (2.2/51 mg/dL) to 0.09 (5.8/66 mg/dL) and from 0.21 (17/81 mg/dL) to 0.49 (27/55 mg/dL), respectively, depending on the diet21. In addition, of the two HDL subclasses (HDL2 and HDL3), HDL2 is the predominant HDL subclass in mice (71%) and hamsters (66%) but is (...truncated)