Long-term development of human iPSC-derived pyramidal neurons quantified after transplantation into the neonatal mouse cortex

One of the main obstacles for studying the molecular and cellular mechanisms underlying human neurodevelopment in vivo is the scarcity of experimental models. The discovery that neurons can be generated from human induced pluripotent stem cells (hiPSCs) paves the way for novel approaches that are stem cell-based. Here, we developed a technique to follow the development of transplanted hiPSC-derived neuronal precursors in the cortex of mice over time. Using post-mortem immunohistochemistry we quantified the differentiation and maturation of dendritic patterns of the human neurons over a total of six months. In addition, entirely hiPSCderived neuronal parenchyma was followed over eight months using two-photon in vivo imaging through a cranial window. We found that transplanted hiPSCderived neuronal precursors exhibit a "protracted" human developmental programme in different cortical areas. This offers novel possibilities for the sequential in vivo study of human cortical development and its alteration, followed in "real time".