Application of amyloid-secreting cellular systems in the development of preclinical models of relevance to Alzheimer's disease

UoM administered thesis: Phd

Abstract

Alzheimer's disease (AD) is the most common type of dementia associated with a progressive decline in cognitive function, amyloid plaque deposition and neurofibrillary tangle formation. Oligomeric forms of the amyloid-beta peptide (A-beta-o) are considered the initiating trigger which cause synaptotoxicity leading to an impairment in memory. Although many preclinical animal models of AD exist, they often only mimic acute, short-term effects of A-beta-o. Their main limitation is their inadequate replication of the progressiveness of AD. This project aims to assess the usefulness of 2-dimensional and 3-dimensional amyloid-secreting cellular systems in the development of a novel preclinical in vivo model for AD research. Formulation of a biocompatible delivery system allows the sustained secretion of A-beta-o for use in developing rodent models of chronic, sporadic AD. Chinese hamster ovary (CHO) cells expressing the human amyloid precursor protein gene (named 7PA2 cells) and wild-type cells were cultured in standard 2D conditions and conditioned media (CM) was analysed using ELISA, dot blot and westerns. A-beta-o from 7PA2 cells were injected into the hippocampus of adult female rats. A novel object recognition (NOR) task and a Y-maze test were performed to assess cognitive deficits. Brains were collected and synaptic markers analysed using western analysis. 7PA2 cells consistently secreted A-beta 1-42 over time. Prefibrillar oligomeric A-beta (~48 kDa) was secreted into the CM. Rats injected with 7PA2 CM showed progressive deficits in NOR starting at Day 4, becoming significant at Day 7 and remaining persistent at Day 14. Deficits were observed in the Y-maze at Day 8. Synaptic dysregulation accompanied cognitive decline as seen in a reduction in post-synaptic marker PSD-95, increase in pre-synaptic marker SNAP-25 and a decrease in parvalbumin compared with controls. Cell encapsulation in alginate was optimised by altering fabrication parameters (flow rate, electrostatic potential and vibration frequency). In conclusion, bioengineered 3D cellular systems encapsulating A-beta-o-secreting cells in an alginate microbead were found to be successful in their potential to model chronic A-beta secretion. Future engraftment of microbeads in the rat brain will allow the assessment of chronic A-beta deposition on cognition and pathology to better model aspects of sporadic AD.

Details

Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award date1 Aug 2020