A Stanford University team has developed a mouse model in which transplanted human cortical organoids expand to occupy most of the available cortical tissue, integrate with the host nervous system, and generate long-range projections and neuron types that are poorly reproduced in conventional organoid models. Published in Nature, the “xenocortication” approach provides a new in vivo system for studying human cortical development, neurological disease, and potential therapeutic interventions.
The work, led by Sergiu Pașca and colleagues at Stanford's Brain Organogenesis Program, builds on the group's 2022 Nature study in which human cortical organoids transplanted into newborn rats matured and integrated into host sensory and behavioral circuits. That earlier approach was constrained by competition with intact host cortex. In the new model, the researchers genetically depleted much of the mouse neocortex and hippocampus before transplanting human cortical organoids, creating substantially more space for the grafts to grow and connect.
By three months after transplantation, human-derived tissue accounted for approximately 92% of the combined cortical tissue volume in the xenocortical mice. The grafts generated a broader range of developing cortical neurons than conventional organoid models, including deep-layer projection neurons and cells resembling von Economo neurons, which are difficult to reproduce in vitro. Human-derived axons also extended through the mouse nervous system as far as the cervical spinal cord, while recordings showed coordinated electrical activity across the graft.
The researchers also tested the platform as a disease model by exposing xenocortical mice to hypoxia intended to mimic aspects of perinatal brain injury. The human grafts showed cellular responses to low oxygen, while the animals developed measurable motor deficits, providing a proof of concept that injury to the transplanted human tissue can be linked to whole-animal readouts.