Unraveling the biology of bipolar disorder using induced pluripotent stem‐derived neurons

Objectives Bipolar disorder has been studied from numerous angles, from pathological studies to large‐scale genomic studies, overall making moderate gains toward an understanding of the disorder. With the advancement of induced pluripotent stem ( iPS ) cell technology, in vitro models based on patient samples are now available that inherently incorporate the complex genetic variants that largely are the basis for this disorder. A number of groups are starting to apply iPS technology to the study of bipolar disorder. Methods We selectively reviewed the literature related to understanding bipolar disorder based on using neurons derived from iPS cells. Results So far, most work has used the prototypical iPS cells. However, others have been able to transdifferentiate fibroblasts directly to neurons. Others still have utilized olfactory epithelium tissue as a source of neural‐like cells that do not need reprogramming. In general, iPS and related cells can be used for studies of disease pathology, drug discovery, or stem cell therapy. Conclusions Published studies have primarily focused on understanding bipolar disorder pathology, but initial work is also being done to use iPS technology for drug discovery. In terms of disease pathology, some evidence is pointing toward a differentiation defect with more ventral cell types being prominent. Additionally, there is evidence for a calcium signaling defect, a finding that builds on the genome‐wide association study results. Continued work with iPS cells will certainly help us understand bipolar disorder and provide a way forward for improved treatments.