Three Dimensional Human Neuro-Spheroid Model of Alzheimer’s Disease Based on Differentiated Induced Pluripotent Stem Cells

Abstract

The testing of candidate drugs to slow progression of Alzheimer’s disease (AD) requires clinical trials that are lengthy and expensive. Efforts to model the biochemical milieu of the AD brain may be greatly facilitated by combining two cutting edge technologies to generate three-dimensional (3D) human neuro-spheroid from induced pluripotent stem cells (iPSC) derived from AD subjects. We created iPSC from blood cells of five AD patients and differentiated them into 3D human neuronal culture. We characterized neuronal markers of our 3D neurons by immunocytochemical staining to validate the differentiation status. To block the generation of pathologic amyloid β peptides (Aβ), the 3D-differentiated AD neurons were treated with inhibitors targeting β-secretase (BACE1) and γ-secretases. As predicted, both BACE1 and γ-secretase inhibitors dramatically decreased Aβ generation in iPSC-derived neural cells derived from all five AD patients, under standard two-dimensional (2D) differentiation conditions. However, BACE1 and γ-secretase inhibitors showed less potency in decreasing Aβ levels in neural cells differentiated under 3D culture conditions. Interestingly, in a single subject AD1, we found that BACE1 inhibitor treatment was not able to significantly reduce Aβ42 levels. To investigate underlying molecular mechanisms, we performed proteomic analysis of 3D AD human neuronal cultures including AD1. Proteomic analysis revealed specific reduction of several proteins that might contribute to a poor inhibition of BACE1 in subject AD1. To our knowledge, this is the first iPSC-differentiated 3D neuro-spheroid model derived from AD patients’ blood. Our results demonstrate that our 3D human neuro-spheroid model can be a physiologically relevant and valid model for testing efficacy of AD drug.

3D culture models of Alzheimer’s disease: a road map to a “cure-in-a-dish”

“…To date, several research groups have reported the usage of iPSCs in AD modeling, which provide a proof-of-principle for modeling patient-specific AD pathology in human brain-like environment [25–30, 37–42, 48, 49, 52, 53]. These patient-derived AD neurons were mainly generated from FAD patients but also a few from sAD patients.…”

“…In general, only a handful of SAD patients showed the increased Aβ levels, which have not been replicable between patients [38–41, 49, 50]. It is not easy to determine whether these variabilities stem from the presence of multiple genetic variants or differential neuronal differentiation conditions due to the lack of isogenic control cell lines.…”

Three‐Dimensional Models of the Human Brain Development and Diseases

“…In a different approach, Lee et al used a combination of differentiated iPSC and 3D neurospheroids to perform a drug screening in an AD model. [144] iPSC derived from AD patients were differentiated and treated with β -site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitors to assess their effect on A β levels. Interestingly, they found that higher concentrations of the inhibitor were needed in order to lower A β in neurospheroids model, likely due to the diminished surface exposure of neurospheroids, lower diffusion rate and more time required for the inhibitor to penetrate into the spheroids.…”

“…This model represent a more physiologically relevant system to the human brain compared to other current cell culture systems and allows high-throughput quantification in addition to proteomics analyses. [144] …”

Making Neurons from Human Stem Cells

“…These types of cell models are important, because they can be made from human cells, which are easier to get and cheaper to use than cells from animals. In fact, a recent study used iPSCs from patients with Alzheimer's disease and made them into a three-dimensional cell model [5]. The researchers showed that there is a buildup of abnormal protein in the cell model that is just like what happens in the in vivo disease.…”