Construction of brain tissues from human iPSCs for investigation of disease mechanisms

抄録

In humans, the brain develops over a long period of time, from the early embryonic days to the postnatal year. Cellular and molecular mechanisms on the brain development have been studied mostly in model animals and post-mortem specimens. However, it is uncertain whether such studies fully reveal the mechanisms that occur in living humans. Emergence of human induced pluripotent stem cells (iPSCs) provides us an opportunity to investigate the development and dysfunction of the human brain. We previously developed 3D culture systems using human PSCs that recapitulate in vivo human brain development. We utilized the self-organizing principles that autonomously appear in the cell population of human PSC reaggregates after neural differentiation. We succeeded in generation of 3D cerebellar tissues that correspond to the cerebellar anlage of human embryos. 3D reaggregate culture followed by long-term 2D co-culture with other neural progenitors enabled to differentiate cerebellar neuronal precursors into mature cerebellar neurons, including Purkinje cells with elaborated dendritic arbors. These culture techniques were further applied to investigation of neurological disorders. We have succeeded in generation of differentiated Purkinje cells from spinocerebellar ataxia (SCA) patient-derived iPSCs by combining the 3D self-organizing culture and the 2D co-culture for maturation. We demonstrated that SCA-derived Purkinje cells exhibit vulnerability to severe culture environment and that this vulnerability is suppressed by treatment with existing drugs. The platform based on the iPSC technology and the self-organizing stem cell 3D culture will become a powerful tool for investigating human brain development and the neuronal diseases.