Ultrastructural changes in a murine model of graded Bruch membrane lipoidal degeneration and corresponding VEGF164 detection.
OBJECTIVE
To evaluate ultrastructural changes in low-density lipoprotein (LDL) receptor knockout (R(-/-)) mice consuming different diets as a potential model of Bruch membrane (BM) lipoidal degeneration and to determine the distribution and concentration of VEGF(164) in this mouse model.


METHODS
Eight-month-old LDL-R(-/-) mice and wild-type controls were fed a standard or a high-fat diet. Animals were killed, and plasma cholesterol levels were determined. Using transmission electron microscopy, BM thickness, lipid vacuole size, and retinal pigment epithelial height were measured. Degenerative alterations of choriocapillaris, RPE, and photoreceptors were described and graded. Using light microscopy, VEGF(164) immunohistoreactivity was graded. Neutral lipids were detected with oil red O.


RESULTS
Choriocapillaris, BM, RPE, and photoreceptors of standard diet control animals showed a regular architecture. LDL-R(-/-) mice fed a standard diet showed more diffuse focal alterations than control mice fed a high-fat diet. Within the choriocapillaris, the basement membrane was thickened, endothelial fenestration numbers were reduced, and lumina narrowed. BM thickness increased with a loss of regular structure. With pronounced BM degeneration, lipid inclusions increased in number and size. A decrease in retinal pigment epithelial cell height was accompanied by signs of intracellular degeneration. Photoreceptor outer segments showed focal degeneration and the formation of vacuoles. All these changes were most pronounced in LDL-R(-/-) mice after a high-fat diet. VEGF(164) was found exclusively in the choriocapillaris, positively correlating with the amount of lipid accumulation in BM.


CONCLUSIONS
Feeding a standard or a high-fat diet to LDL-R(-/-) mice and wild-type controls resulted in a reproducible model of graded BM lipoidal degeneration that resembled alterations in aged human eyes. This model provides a valuable tool for investigating biological responses to lipoidal degeneration.
Schmidt-Erfurth
Ursula
U
Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.
Rudolf
Martin
M
Funk
Marion
M
Hofmann-Rummelt
Carmen
C
Franz-Haas
Nikola-Simone
NS
Aherrahrou
Zouhair
Z
Schlötzer-Schrehardt
Ursula
U
D000818:Animals; D050197:Atherosclerosis / Q000150:complications; D016570:Bruch Membrane / Q000378:metabolism* / Q000648:ultrastructure*; D002784:Cholesterol / Q000097:blood; D004041:Dietary Fats / Q000008:administration & dosage; D004195:Disease Models, Animal; D005260:Female; D007124:Immunoenzyme Techniques; D050356:Lipid Metabolism; D008268:Macular Degeneration / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D010857:Pigment Epithelium of Eye / Q000648:ultrastructure; D011973:Receptors, LDL / Q000172:deficiency / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D004041:Dietary Fats; D011973:Receptors, LDL; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D002784:Cholesterol