Synaptophysin depletion and intraneuronal Aβ in organotypic hippocampal slice cultures from huAPP transgenic mice

Background: To date, there are no effective disease-modifying treatments for Alzheimer's disease (AD). In order to develop new therapeutics for stages where they are most likely to be effective, it is important to identify the first pathological alterations in the disease cascade. Changes in A beta concentration have long been reported as one of the first steps, but understanding the source, and earliest consequences, of pathology requires a model system that represents all major CNS cell types, is amenable to repeated observation and sampling, and can be readily manipulated. In this regard, long term organotypic hippocampal slice cultures (OHSCs) from neonatal amyloid mice offer an excellent compromise between in vivo and primary culture studies, largely retaining the cellular composition and neuronal architecture of the in vivo hippocampus, but with the in vitro advantages of accessibility to live imaging, sampling and intervention. Results: Here, we report the development and characterisation of progressive pathological changes in an organotypic model from TgCRND8 mice. A beta(1-40) and A beta(1-42) rise progressively in transgenic slice culture medium and stabilise when regular feeding balances continued production. In contrast, intraneuronal A beta continues to accumulate in close correlation with a specific decline in presynaptic proteins and puncta. Plaque pathology is not evident even when A beta(1-42) is increased by pharmacological manipulation (using calpain inhibitor 1), indicating that soluble A beta species, or other APP processing products, are sufficient to cause the initial synaptic changes. Conclusions: Organotypic brain slices from TgCRND8 mice represent an important new system for understanding mechanisms of A beta generation, release and progressive toxicity. The pathology observed in these cultures will allow for rapid assessment of disease modifying compounds in a system amenable to manipulation and observation.