Abstract title: Functional and morphological effects of 12 kDa C-terminal ApoE fragments in rat cortex cultures

Poster number:P0238 / #943

Authors: Christina Nodin1, Charlotte Mattsson2, Charlotte Sahlin2, Christer Möller2, Johanna Fälting2, Johan Pihl1, Paul Karila1, Susanne Fabre2
Affiliations: 1Cellectricon AB, Mölndal, Sweden, 2BioArctic AB, Research & Development, Stockholm, Sweden

Aims: In a previous study, 12 kDa C-terminal ApoE fragments were identified to be increased in Alzheimer’s disease (AD) brain as compared to non-demented controls (NDC). To evaluate potential effects of these fragments in AD pathogenesis we used optical electrophysiology and high content imaging (HCA)-based assays to study effects on function and morphology of neurons and astrocytes in neuronal rat cortical cultures.
Methods: Embryonic rat cortical (rCtx) 384-well format cultures were either transduced with Adenoassociated viruses (AAVs) carrying vectors encoding C-terminal ApoE fragments, or fragments were added directly to cells. Neuronal and astrocyte morphology was quantified using HCA. Further, an optical electrophysiology platform was used to investigate effects on neuronal network activity.
Results: Extracellular addition of 12 kDa C-terminal ApoE fragments to rCtx cultures did not result in any effects on either morphological or functional parameters. This was probably caused by an inadequate uptake of the fragments by the cells. However, using AAV-based expression of 12 kDa C-terminal ApoE fragments, successful expression was demonstrated intracellularly in both neurons and astrocytes. As a result of fragment expression, the number of astrocytes and the density of the astrocytic network was decreased, whereas no effects were observed on the neuronal morphology. The astrocytes thus appeared to be more vulnerable to transduction with AAV-ApoE fragments compared to the neurons. Interestingly, spontaneous neuronal activity was affected by expression of ApoE fragments.
Conclusions: An AAV-based approach to achieve intracellular expression of ApoE fragments was established. Expression of ApoE fragments caused a decrease in astrocytic number and cellular network density. Further, neuronal activity was altered in presence of the 12 kDa C-terminal ApoE fragments. Future studies should include appropriate AAV-controls to ensure the specific effects observed.