Modeling retinal Alzheimer’s disease histopathology with human iPSC‐derived retinal organoids for mechanistic and DRUG DEVELOPMENT studies

Abstract

AbstractBackgroundThe neuropathological features that characterize Alzheimer’s disease (AD), including the presence of beta‐amyloid (Aß) plaques and intracellular neurofibrillary tangles (NFTs) of abnormally phosphorylated Tau proteins (pTau), are manifested not only in the brain but also in the retina, an extension of the central nervous system. This is likely to contribute to the visual manifestations of AD that can pose additional challenges to this vulnerable population. Moreover, due to its accessibility and the availability of non‐invasive imaging technologies, the retina is being investigated as a potential biomarker of AD progression. In this context, hiPSC‐derived retinal organoids offer new opportunities for AD modeling that present advantages for DRUG DEVELOPMENT applications. Retinal organoids mimic the histoarchitecture of the native retina, have a consistent cellular composition, and are optically clear. Moreover, 3D automated reporter quantification (3D‐ARQ) technologies have been established to facilitate quantitative assay design in these models without loss of their 3D structure. Thus, we set out to develop and characterize an hiPSC‐derived retinal organoid model of AD that can be applied to the evaluation of pathophysiological mechanisms and to the validation of potential therapeutic drugs.MethodsHuman iPSC‐derived retinal organoids were generated from three healthy control (HC) and two familial AD (fAD) donors using the Zhong et al. (2014) protocol. Organoid structure, cellular composition and AD histopathology were assessed at three and six months of differentiation by immunoblotting and immunofluorescence staining, including retinal cell type‐specific markers as well as Aβ, pathological pTau forms, and NIAD‐4 staining for amyloid plaques. We also developed a NIAD‐4 fluorescence‐based assay for amyloid quantification in intact organoids using 3D‐ARQ technology.ResultsWe found similarities in the cellular composition of AD and HC retinal organoids, confirming the validity of the models. However, pathological Tau hyperphosphorylation and Aß deposits were significantly increased in AD retinal organoids compared to HCs. Finally, we developed proof of concept of a quantitative assay for amyloid plaque detection that is amenable to translational research applications.ConclusionsOur AD retinal organoid models mimic critical aspects of the histopathology of the human AD retina and constitute valuable tools for the screening and validation of candidate molecules with therapeutic potential.