Fabrication of functional basal ganglia circuitry in vitro: from nano- and micro-scale topographies to microfluidic devices.

Abstract

According to the European Brain Council, the annual total cost of brain disorders such as Huntington’s disease (HD) and Parkinson’s disease (PD) in Europe is approximately €386 billion. In order to develop therapies for neurodegenerative diseases, model systems that accurately
reproduce the complex circuitry of the adult brain are needed. Neuron circuits developed in vitro could be used for studying pathogenesis of disorders and for high-throughput screening of potential therapies. In vitro models may offer the potential for highly reproducible and controllable cell circuitry, mimicking to some extent the complex neural connectivity required for function.
Nano- and micro-scale substrates could be fabricated using techniques such as electrospinning, lithography and microfluidics to direct neurite orientation in order to build in vitro models that mimic in vivo circuitry. Poly-lactic acid (PLA) nano-fibres and polydimethylsiloxane (PDMS) micro-groove constructs were either pre-coated with poly-D-lysine (PDL) and laminin (LN) or pre-aligned
astrocytes to study attachment and orientation of striatal neurites. Neurites were more responsive to substrates made up of combined topography and chemical cues; PDL and LN coated PDMS micro-grooves yielded the best neurite alignment. Excitability of striatal and cortical neurons was verified via an electrophysiology technique of patch clamp. PDMS microfluidic devices fabricated via lithographic techniques, were developed for co-culturing basal ganglia (BG) cells to model BG
in vivo circuitry. Cell populations in the microfluidic device displayed electrical activity monitored using a calcium imaging technique. Connectivity was determined by eliminating activity of one cell population using tetrodotoxin (TTX) and studying response of remaining cell populations. Micro-contact printing was further explored as a technique for patterning BG cell circuitry instead of microfluidic devices. The microfluidic-based functional and complex model developed herein provides platform technology that can be useful for pharmaceutical and regenerative therapy and evaluation, therefore massively reducing costs currently associated with neurodegenerative diseases.