The central nervous system (CNS) is a conglomerate of diverse, interconnected tissues that each contain cell phenotypes specific to their distinct anatomical region. Recent studies have demonstrated that CNS cells derived from human pluripotent stem cells (hPSCs) must be of the appropriate regional phenotype to model tissue-specific disease pathologies in vitro as well as produce a regenerative effect upon transplantation. Yet, only a limited number of regional CNS phenotypes can be derived from hPSCs due to the complex regimen of developmental cues necessary to effectively instruct region-specific neural differentiation.
Here, we present a chemically defined protocol for deriving forebrain neural stem cells (NSCs) from hPSCs with greater than 90% efficiency in under 6 days (Lippmann et al. Stem Cells 2014). Also, we have successfully deciphered the regimen of developmental cues that govern differentiation of hPSCs into NSC phenotypes specific to any diverse hindbrain or spinal cord region (Lippmann et al. Stem Cell Reports 2015). These NSC cultures can be differentiated into a spectrum of respective regional hindbrain and spinal cord motor neuron phenotypes, which can be matured to fire action potentials and innervate skeletal muscle fibers in vitro.
Hence, our chemically defined protocols vastly expand the diversity of regional CNS phenotypes that can be derived from hPSCs. They enable access to the hundreds of different regional motor neuron phenotypes present in the human hindbrain and spinal cord, which are the sole means of transmitting efferent signals from the CNS to peripheral tissues including skeletal muscles that provide motor function. Our findings have significant implications for modeling degenerative disorders that target hindbrain and spinal cord motor neurons (e.g. Amyotrophic Lateral Sclerosis) and developing regenerative cell therapies for paralysis.