β-amyloid induces a dying-back process and remote trans-synaptic alterations in a microfluidic-based reconstructed neuronal network

Bérangère Deleglise (1) , Sébastien Magnifico (2) , Eric Duplus (3) , Pauline Vaur (1) , Vanessa Soubeyre (4, 5) , Morgane Belle (4) , Maeva Vignes (4) , Jean-Louis Viovy (6) , Etienne Jacotot (3) , Jean-Michel Peyrin (3) , Bernard Brugg (3)

1 B2A - Adaptation Biologique et Vieillissement = Biological Adaptation and Ageing
2 NPA - Neurobiologie des processus adaptatifs
3 NSA - Neuronal Stress and Aging
4 CNRS - Centre National de la Recherche Scientifique
5 CSGA - Centre des Sciences du Goût et de l'Alimentation [Dijon]
6 Institut Curie [Paris]

Recent histopathological studies have shown that neurodegenerative processes in Alzheimer’s and Parkinson’s Disease develop along neuronal networks and that hallmarks could propagate trans-synaptically through neuronal pathways. The underlying molecular mechanisms are still unknown, and investigations have been impeded by the complexity of brain connectivity and the need for experimental models allowing a fine manipulation of the local microenvironment at the subcellular level. Results In this study, we have grown primary cortical mouse neurons in microfluidic (μFD) devices to separate soma from axonal projections in fluidically isolated microenvironments, and applied β-amyloid (Aβ) peptides locally to the different cellular compartments. We observed that Aβ application to the somato-dendritic compartment triggers a “dying-back” process, involving caspase and NAD+ signalling pathways, whereas exposure of the axonal/distal compartment to Aβ deposits did not induce axonal degeneration. In contrast, co-treatment with somatic sub-toxic glutamate and axonal Aβ peptide triggered axonal degeneration. To study the consequences of such subcellular/local Aβ stress at the network level we developed new μFD multi-chamber devices containing funnel-shaped micro-channels which force unidirectional axon growth and used them to recreate in vitro an oriented cortico-hippocampal pathway. Aβ application to the cortical somato-dendritic chamber leads to a rapid cortical pre-synaptic loss. This happens concomitantly with a post-synaptic hippocampal tau-phosphorylation which could be prevented by the NMDA-receptor antagonist, MK-801, before any sign of axonal and somato-dendritic cortical alteration. Conclusion Thanks to μFD-based reconstructed neuronal networks we evaluated the distant effects of local Aβ stress on neuronal subcompartments and networks. Our data indicates that distant neurotransmission modifications actively take part in the early steps of the abnormal mechanisms leading to pathology progression independently of local Aβ production. This offers new tools to decipher mechanisms underlying Braak's staging. Our data suggests that local Aβ can play a role in remote tauopathy by distant disturbance of neurotransmission, providing a putative mechanism underlying the spatiotemporal appearance of pretangles.

Keywords: tau; axonal degeneration; microfluidics; neuronal network; synapse loss

Domains: Life Sciences [q-bio]

Bérangère Deleglise, Sébastien Magnifico, Eric Duplus, Pauline Vaur, Vanessa Soubeyre, et al.. β-amyloid induces a dying-back process and remote trans-synaptic alterations in a microfluidic-based reconstructed neuronal network. Acta Neuropathologica Communications, 2014, 2, pp.145. ⟨10.1186/s40478-014-0145-3⟩. ⟨hal-01221362⟩