Midbrain dopaminergic (mDA) neurons play a critical role in regulating postural reflexes and movement as well as modulating psychological processes. Dysfunction or degeneration of mDA neurons is involved in a number of neurological disorders including Parkinson’s disease. Availability of large quantities of human mDA neurons would greatly enhance our ability to reveal pathological processes underlying mDA neuron degeneration and to identify treatments for these neurological conditions. Human pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), provide an unlimited source for mDA neurons. Here we describe a chemically defined protocol for mDA neuron differentiation. PSCs are first converted to neuroepithelia in a chemically defined medium without any growth factors, followed by patterning the neuroepithelia to midbrain progenitors with fibroblast growth factor 8 (FGF8) and sonic hedgehog (SHH) and subsequent differentiating to functional mDA neurons. This protocol typically yields about half of the neuronal population being mDA neurons, determined by expression of mDA markers, electrophysiological recordings, and the ability to reverse functional deficit in a rat model of Parkinson’s disease.
