Human tripartite cortical network model for temporal assessment of alpha-synuclein aggregation and propagation in Parkinson’s Disease

Abstract

Previously, several in vitro and in vivo studies have shown that the pathological hallmark of Parkinson’s disease (PD), malicious strains of alpha-synuclein (α-s) protein, are transferred between cells via different routes, thus participating in disease progression. The amplification of α-s and propagation of its aggregated forms are described as prion-like propagation widely supported by in vitro rodent and human cell studies. In this study, our focus was on temporal assessment of functional changes during α-s aggregation and propagation in human induced pluripotent stem cell (hiPSC)-derived neuronal cultures and in engineered networks. Here, we report for the first time an engineered circular tripartite human neuronal network model in a microfluidic chip integrated with microelectrode arrays (MEAs) as a platform to study functional markers during α-s aggregation and propagation. We showed a progressive aggregation of α-s in conventional neuronal cultures and in the exposed (proximal) compartments of circular tripartite networks after we preformed α-s fibril (PFF) exposure. Moreover, aggregated forms propagated through axonal transportation to distal compartments of the circular tripartite networks. We observed impacts of α-s aggregation on both the structure and function of neuronal cells, such as in presynaptic proteins, mitochondrial motility, receptor channel expression, calcium oscillations and neuronal activity. The model enabled an assessment of the early, middle, and late phases of α-s aggregation and its propagation during a 13-day follow-up period. Taken together, this temporal analysis suggested a complex interplay of structural and functional changes during the in vitro propagation of α-s aggregates.