Investigating Synapse Function In Organotypic Hippocampal Slice Culture Models of Neurodegeneration

Organotypic hippocampal slice cultures (OHSCs) are a useful in vitro model for researching synapse dysfunction; they provide easy access to the tissue for biomarker analysis, whilst retaining much of the neuronal architecture and endogenous cell types, representing a reasonable compromise between the advantages of *in vivo* and *in vitro* preparations. OHSCs prepared from TgCRND8 mice develop phenotypic changes that are relevant to early changes in human Alzheimer’s disease (AD), including increased amyloid beta and progressive loss of the presynaptic protein synaptophysin; however, direct analysis of functional changes in this model has not yet been achieved. Additionally, wild type mice exposed to the inflammatory molecule Lipopolysaccharide (LPS) experience similar loss of presynaptic protein, indicating the possible loss of presynaptic terminals. Synapse dysfunction and loss are some of the earliest changes in AD and other neurodegenerative conditions; by understanding how changes in neuronal and synaptic activity are related to the mechanisms of synapse loss in OHSCs we have the best chances of identifying possible therapeutic targets for combatting cognitive decline in neurodegenerative diseases. In this thesis we develop an electrophysiological method for investigating synapse function in OHSCs, establishing a robust experiment and analysis pipeline using whole cell patch clamping to measure spontaneous and miniature synaptic events in CA1 pyramidal neurones. Applying this method to long term (8 weeks) TgCRND8 OHSCs, we found that activity within OHSCs underwent significant changes throughout the culture period, but there were no strong genotype related effects, despite decreases in the presynaptic protein synaptophysin. We go on to investigate function in an LPS induced neuroinflammation model in OHSCs, and found significant impairment of excitatory and inhibitory synaptic function, accompanied by significant decreases in membrane capacitance. Ablation of microglia in these cultures partially recovered LPS induced synaptophysin loss, but did not recover functional deficits. These results provide insight into how best OHSCs should be used as a tool to explore neurodegeneration, indicating that they may be best suited for research with acute models rather than long term chronic models. Additionally, they underscore the need for critical evaluation of synaptophysin as a marker of presynaptic health and function.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Humphrey, Robert

Advisor dc:contributor.advisor

• Coleman, Michael

• Alzheimer's Disease
• Amyloid beta
• Electrophysiology
• Hippocampus
• Inflammation
• Organotypic Hippocampal Slice Cultures
• Patch Clamp
• Synaptophysin

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/b6a90d5f-492d-4445-9b4e-4d101a97c3c9/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.109149

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/369269