Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCB257

Poster Communications

Intracerebral injection of conditioned medium from certain human iPSC-derived neurons blocks hippocampal LTP in the live rat

N. Hu1, T. T. O'Malley2, S. Moore3, D. M. Walsh2, F. J. Livesey3, M. J. Rowan1

1. Department of Pharmacology & Therapeutics and Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland. 2. Ann Romeny Centre for Neurologic Diseases, Brigham & Women's Hospital, Harvard Institutes of Medicine, Boston, Massachusetts, United States. 3. The Gurdon Institute, Cambridge Stem Cell Institute and Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.

Induced pluripotent stem cells (iPSCs) from genetic forms of Alzheimer's disease (AD) are important tools to study molecular aspects of the disease. We previously found that neurons generated from familial AD iPSCs generate increased amounts of longer, toxic amyloid ß-protein (Aβ) peptides1. We predicted therefore that iPSC-derived neurons may release synaptotoxic mediators to cause synaptic dysfunction, which is widely accepted as the main cellular mechanism of early AD. Here we determined if such factors impair hippocampal long-term potentiation (LTP) in the live rat. Adult (250-350 g) male Wistar rats were used in all experiments. Prior to the surgery, animals were anesthetized with urethane (1.5-1.6 g/kg, i.p.). Cortical neurons were produced from iPSCs derived from fibroblasts of individuals with APP duplication, or mutation in PSEN1 (Intron 4). A stainless-steel cannula (22 gauge, 0.7 mm outer diameter) was implanted above the right lateral ventricle. Intracerebroventricular (i.c.v.) injection of vehicle or conditioned medium (CM) was made via an internal cannula. Field excitatory postsynaptic potentials (EPSPs) were recorded from the stratum radiatum in the CA1 area of the right hippocampus in response to stimulation of the ipsilateral Schaffer collateral-commissural pathway. LTP was induced using 200 Hz high frequency stimulation (HFS) consisting of one set of ten trains of twenty pulses (inter-train interval of 2 s). Test EPSPs were triggered a 50% maximum EPSP response and raised to 75% maximum during the HFS. The magnitude of LTP is expressed as the percentage of pre-HFS baseline EPSP amplitude (± s.e.m.) ("Pre"), compared by paired t and one-way ANOVA-Tukey. Acute injection of CM from APP duplication 30 min pre HFS inhibited LTP at 3h post-HFS (102.8 ± 2.6%, n = 6, P > 0.05 compared with Pre; P < 0.05 compared with non-demented control). Similarly, acute injection of CM from PSEN1 neurons also inhibited LTP at 3h post-HFS (108.2 ± 3.7%, n=6, P < 0.05 compared with Pre; P < 0.05 compared with non-demented control). In contrast, i.c.v. injection of CM from non-demented control neurons did not significantly affect LTP (121.9 ± 2.6%, n = 7, P < 0.05 compared with Pre; P > 0.05 compared with 126.1 ± 3.8% in the vehicle control). Interestingly, CM from PSEN1 neurons that had been immunodepleted of Aß failed to inhibit LTP (129.7 ± 2.1%, n=6, P < 0.05 compared with Pre and P > 0.05 compared with vehicle control group). Our data indicate that cortical neurons derived from individuals with certain genetic forms of AD release soluble agents that impair LTP that is mediated by Aß peptides.

Where applicable, experiments conform with Society ethical requirements