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Improved Generation of Ventral Midbrain Neurons from Human Induced Pluripotent Stem Cells

Review of "Stimulation of L-type calcium channels increases tyrosine hydroxylase and dopamine content in ventral midbrain cells induced from somatic cells" from STEM CELLS Translational Medicine by Stuart P. Atkinson 

The screening of therapeutic approaches for ventral midbrain disorders, which includes childhood dystonia or Parkinson's disease, requires a source of high‐quality human dopamine‐producing ventral midbrain cells; furthermore, such cells may also play a key role in cell replacement and modeling approaches. The robust generation of dopaminergic cells from human induced pluripotent stem cells (hiPSCs) currently uses a modified dual SMAD inhibition approach to create neuroectoderm with simultaneous sonic hedgehog exposure [1-3]. Of note, small changes to dosing or timing can lead to significant shifts in cell types produced with potentially significant therapeutic consequences [4], thereby necessitating extensive quality control steps before their application.

Now, a new STEM CELLS Translational Medicine article from researchers led by Carl Ernst (McGill University and Douglas Hospital Research Institute, Montreal, Quebec, Canada) report on their significantly improved protocol for the generation of ventral midbrain neurons from hiPSCs and their use of techniques such as live calcium imaging and electrophysiology as quality control measures [5]. Overall, the authors believe that their new advance will improve the accuracy of disease modeling/small molecule screening and allow for the more rapid development of cell replacement therapy for ventral midbrain disorders.

Jefri et al. employed a previously described protocol for the development of midbrain dopamine neurons from hiPSCs [1, 2] with an additional two‐step purification step that isolates midbrain neural progenitor cells and then aggregates them into organoid bodies to promote self-renewal and cell amplification. Subsequent neuronal differentiation then allowed for the rapid and robust generation of a highly pure population of dopamine neurons that exhibit calcium pacemaking activity and classical electrophysiological properties. Of note, calcium flux analysis suggested that mature ventral midbrain neurons displayed higher firing frequency and enhanced subnetwork connectivity than more immature cells.

The authors then exposed hiPSC-derived ventral midbrain neurons to the BAY‐K8644 L‐type calcium channel agonist for 15 days, which permitted a significant increase in the levels of tyrosine hydroxylase, the rate‐limiting enzyme for dopamine synthesis. As expected, the study also found increased intracellular levels of dopamine and enhanced dopamine release, which the authors suggest derives from a BAY‐K8644-mediated strengthening of cell-to-cell connectivity that permitted the immediate influx of calcium to coincide in all cells [6].

Overall, the authors describe how a few simple modifications can enhance the differentiation of hiPSCs into ventral midbrain neurons expressing elevated levels of tyrosine hydroxylase and dopamine, which may lead to the development of more accurate disease models and enhanced small molecule screens for ventral midbrain specific disorders such as including Parkinson's disease.

For more on the enhanced generation of ventral midbrain neurons and all the new cell therapies aimed at treating devastating neural disorders, stay tuned to the Stem Cells Portal!


References

  1. Chambers SM, Fasano CA, Papapetrou EP, et al., Highly efficient neural conversion of human ES and iPS cells by dual inhibition of SMAD signaling. Nature Biotechnology 2009;27:275-280.
  2. Nolbrant S, Heuer A, Parmar M, et al., Generation of high-purity human ventral midbrain dopaminergic progenitors for in vitro maturation and intracerebral transplantation. Nature Protocols 2017;12:1962-1979.
  3. Kikuchi T, Morizane A, Doi D, et al., Human iPS cell-derived dopaminergic neurons function in a primate Parkinson’s disease model. Nature 2017;548:592-596.
  4. Politis M, Oertel WH, Wu K, et al., Graft-induced dyskinesias in Parkinson's disease: High striatal serotonin/dopamine transporter ratio. Movement Disorders 2011;26:1997-2003.
  5. Jefri M, Bell S, Peng H, et al., Stimulation of L-type calcium channels increases tyrosine hydroxylase and dopamine in ventral midbrain cells induced from somatic cells. STEM CELLS Translational Medicine 2020;9:697-712.
  6. Liu Y, Dore J, and Chen X, Calcium Influx through L-type Channels Generates Protein Kinase M to Induce Burst Firing of Dopamine Cells in the Rat Ventral Tegmental Area. Journal of Biological Chemistry 2007;282:8594-8603.