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Tuhina Prasad, Ping Zhu, Amrisha Verma, Paramita Chakrabarty, Awilda M Rosario, Todd E Golde, Qiuhong Li; Increased levels of amyloid β peptides in RPE via AAV-mediated gene transfer mimics AMD-like pathology in mice. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3765.
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Age-related macular degeneration (AMD) is a progressive retinal neurodegenerative disorder and shares several common characteristics of Alzheimer’s disease (AD). Recent studies have provided evidence that amyloid β (Aβ), a major extracellular deposit in the senile plaques of the AD brain, is also found in drusen, the extracellular deposits characteristic of AMD patients. The goal of this study is to investigate the effects of selective increase of human Aβ42 and Aβ40 in adult mouse retina and to examine the contribution of each to retinal pathophysiology via AAV mediated gene delivery.
AAV1 vectors encoding BRI-Aβ cDNAs, fusions between human Aβ peptides and the BRI protein involved in amyloid deposition in British and Danish familial dementia were used to achieve high-level subretinal expression and secretion of the specific encoded Aβ peptide. C57Bl6J mice were randomly divided into following groups based on the vector injected subretinally: (1) AAV1-Bri-Aβ40, (2) AAV1-Bri-Aβ42, (3) Combination of AAV1-Bri-Aβ40 and Aβ42, (4) Control vector AAV1-Bri-Delta KR and (5) Uninjected control. In vivo retinal morphology was assessed by fundus and OCT imaging. Visual function was evaluated by ERG six weeks after injection. Retinal histology was evaluated from paraffin-embedded H&E stained sections. Immunofluorescence was performed to examine Aβ peptides, gliosis, and cell death using specific markers.
The large drusen-like extracellular deposits were present in the subretinal space in AAV1-Bri-Aβ40 or Aβ42 injected eyes, absent in control vector injected or uninjected eyes. Immunofluorescence study showed that these deposits were positive for Aβ. Besides the subretinal deposits, the thickness of photoreceptor outer nuclear layer is normal and the ERG responses were only slightly affected in eyes with single vector injection of AAV1-Bri-Aβ40 or Aβ42. Combination of both vectors resulted in more drusen-like deposits, correlated with more severe reduction in ERG responses and photoreceptor cell loss.
Our results show that overexpression of either Aβ40 or Aβ42 peptide in the retina is sufficient to initiate Aβ deposition, combination of both caused more severe retinal pathophysiology and that AAV-mediated gene transfer of Aβ peptides is a valuable tool to model aspects of AMD.
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