Novel Avenues to Model and Investigate Alzheimer’s Disease In Vitro

Abstract

Alzheimer's’ disease (AD) is a complex neurodegenerative disease which presents with a number of neuropathological features, most noticeably include gross brain atrophy, neuroinflammation, insoluble parenchymal amyloid-β (Aβ) deposits and intracellular neurofibrillary tangles containing hyperphosphorylated tau. Ab42-related neurotoxicity has been an evolving topic of debate within the field over many decades. The lack of molecular tools to modulate specific aspects of the amyloid aggregation pathway, a neuron-centric exploration of AD and use of in vitro models with poor face validity have all contributed to the lack of successful drug discovery within AD. This thesis sought to investigate and model AD through a number of novel avenues. These included: 1) investigating the ability of novel Ab42 monomer-sequestering drugs to protect against Ab42-induced neurotoxicity in vitro, 2) characterising the morphological and inflammatory phenotype of induced pluripotent stem cell (iPSC)-derived astrocytes and microglia from patients harboring a previously uncharacterised PSEN2 (N141I) mutation, and 3) developing a novel tuneable and bioprintable 3D culture system which supports the function of iPSC-derived CNS cells. In chapter 2, we showed that diverting the monomeric form of the Ab42 peptide away from the amyloidogenic pathway using novel Ab42 monomer-sequestering triazole-linked macrocycles prevented formation of pre-fibrillar species that are toxic to differentiated SH-SY5Y cells. In chapter 3, PSEN2 (N141I)-mutant astrocytes and microglia-like cells presented with a ‘primed’ phenotype characterised by reduced morphological complexity, exaggerated pro-inflammatory cytokine secretion and altered Aβ42 production and phagocytosis. In chapter 4, we reported the optimisation of a novel CNS-mimetic 3D hydrogel compatible with medium-high throughput 3D bioprinting. We showed that the 3D bioprinted cell-containing hydrogels enhanced neuronal differentiation and supported the viable culture of iPSC-derived astrocytes and neural progenitors. Additionally, we showed that iPSC-derived neurons from fAD patients harboring a PSEN2 (N141I) mutation exhibited alterations in spontaneous neuronal activity.