Detecting Aβ deposition and RPE cell senescence in the retinas of SAMP8 mice.
Our previous study indicated that Aβ-induced Retinal Pigment Epithelial (RPE) cell senescence may be associated with chronic inflammation in age-related macular degeneration (AMD). The present study was designed to explore whether Aβ deposition and RPE senescence could be found in the senescence-prone mouse strain 8 (SAMP8), which is an animal model for AMD.



Eyes of both SAMP8 and age-matched SAMR1 (SAM resistant) mice were examined in vivo by fundus photography and electroretinography (ERG). Retinal morphological features were assessed using light and electron microscopy. Aβ deposition and p16-positive senescent RPE cells were traced using immunofluorescence labeling. P16 expression was detected using western blot. Expressions of IL-6 and IL-8 in RPE/choroid were analyzed using RT-PCR.



In fundus of SAMP8, age-dependent increase of drusen-like lesions and the increase of granular autofluorescent spots were respectively detected using IR (near-infrared) and AF (autofluorescence) imaging of confocal scanning laser ophthalmoscope. The amplitude of the ERGs declined with age in SAMP8 and these changes were paralleled with the significant changes in retinal morphological features examined by funduscopy. Histopathological analysis found significant loss of photoreceptor outer segments (OS) and abnormal localization of RPE cells in aged SAMP8 mice. Degenerative changes in RPE cells of aged SAMP8 mice, including massive vacuoles, thickened Bruch's membrane (BrM), and loss of basal infoldings were further confirmed by electron microscopy. Increased Aβ deposits in OS layer and p16-positive senescent RPE cells were observed using immunofluorescence microscopy. Western blot confirmed that P16 expression was significantly increased in RPE cells of aged SAMP8 mice. Expressions of proinflammatory IL-6 and IL-8 were significantly upregulated in RPE/choroid of aged SAMP8 mice.



Our results showed that aged SAMP8 mice developed ocular pathology similar to some features of human AMD. In this AMD mouse model, Aβ deposition and RPE senescence may be associated with AMD development, and RPE senescence is likely a mechanistic link between Aβ deposition and inflammation.
Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University, Shanghai 200072, China.
Le
L
Feng
Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University, Shanghai 200072, China.
Lining
L
Cao
Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University, Shanghai 200072, China.
Yao
Y
Zhang
Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University, Shanghai 200072, China.
Fang
F
Wang
D000367:Age Factors; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D016922:Cellular Senescence; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004195:Disease Models, Animal; D004596:Electroretinography; D004847:Epithelial Cells / Q000502:physiology*; D005654:Fundus Oculi; D006801:Humans; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008268:Macular Degeneration / Q000473:pathology*; D051379:Mice; D046529:Microscopy, Electron, Transmission; D010781:Photography; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000378:metabolism*
D016229:Amyloid beta-Peptides; C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D015850:Interleukin-6; D016209:Interleukin-8; C577686:interleukin-6, mouse