Objective: To better understand Parkinson’s disease (PD) pathophysiology and enhance therapeutic development by bioengineering an in vitro nigrostriatal system that mimics the complex architecture of the native system.

Background: Most in vitro approaches to modeling PD developed to date fail to recapitulate a key aspect of the nigrostriatal pathway which is a long-projecting axonal pathways synapsing on specific neural populations which likely contributes to the preferential vulnerability of many affected pathways and possibly contributes to pathophysiological progression. As an adjunct to our development of tissue engineered neural networks (TENNs) for therapeutic restoration [1,2], we have also developed TENNs constructs with striatal target tissue incorporated to replicate the structure and function of the native nigrostriatal system.

Method: Ventral mesencephalic dopaminergic neurons and medium spiny neurons (MSNs) from the striatum were isolated from rat embryos. Tissue-engineered nigrostriatal pathways were formed by seeding dopaminergic neuron aggregates at one end of hollow hydrogel micro-columns with a central extracellular matrix, up to several centimeters in length. Several days later, a tissue-engineered MSN aggregate was seeded on the distal end. Immunocytochemistry (ICC) and confocal microscopy were used to assess viability (Hoechst nuclear stain), and mitochondrial dynamics (MitoTracker Red), as well as cytoarchitecture and synaptic integration by labelling axons (β-tubulin), neurons/dendrites (MAP2), dopaminergic neurons/axons (tyrosine hydroxylase), and MSNs (DARPP-32).

Results: Confocal microscopy confirmed extensive axonal-dendritic integration and synapse formation between dopaminergic neurons and the somata/processes of MSNs. Therefore, these constructs recapitulated the cytoarchitecture of the natural nigrostriatal pathway: a discrete population of dopaminergic neurons with long-projecting axonal tracts synapsing with a population of MSNs. Mitochondria staining revealed dynamic intra-axonal mitochondrial transport. In addition, seeding nigrostriatal constructs with alpha-synuclein preformed fibrils revealed uptake and aggregation of alpha-synuclein.

Conclusion: Tissue-engineered nigrostriatal constructs recapitulate the architecture of the nigrostriatal pathway and can be seeded with alpha-synuclein fibrils to investigate axonal transport and cell-to-cell transmission.

References: [1] Struzyna LA et al. J Tissue Eng Regen Med. 2018 Jul;12(7):1702-1716 [2] Harris JP et al. NPJ Parkinsons Dis. 2020 Jan 8;6:4

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MDS Abstracts - https://www.mdsabstracts.org/abstract/bioengineered-nigrostriatal-constructs-model-lewy-pathology/