Medium-throughput computer aided micro-island method to assay embryonic dopaminergic neuron cultures in vitro

Abstract

In Parkinson's disease (PD) midbrain dopaminergic (DA) neurons degenerate and die, causing loss of motor function. Currently no therapies exist to ameliorate neurodegeneration or to restore DA neurons, although neurotrophic factors (NTFs) are promising leads. Prior in vivo studies the NTFs are routinely assessed in vitro by quantifying the survival of DA neurons from embryonic rodent midbrain cultures. Current in vitro methods are limited in terms of assay reliability, arduous workflow, low throughput, low statistical power and may obscure detection of molecules with minor yet critically important therapeutic effects. We have developed a medium-throughput, micro-island culture method. It permits analysis of 10-12 data points from a single embryo - several fold more than any previously published method - and enables comparisons of DA neurons from a single gene knockout (KO) embryo. It is computer-aided, improves statistical power and decreases the number of animals and workload per experiment. This method enhances testing capabilities of NTFs and other factors, and enables small scale screening of chemical drug libraries. We have validated the method by confirming the known effects of glial cell line-derived neurotrophic factor (GDNF) and neurturin (NRTN), and demonstrated additive effects via simultaneous addition of GDNF and heparin binding growth associated molecule (HB-GAM). We also show for the first time that DA neurons isolated from GDNF receptor RET-deficient mice are still GDNF responsive, suggesting the presence of an alternative non-RET receptor for GDNF in the DA system. Finally, the method can be adapted for analyses of other low abundance neuronal systems.