Scientists grow human brain tissue in mice with breakthrough technique

Sergiu Pașca, a Romanian-born scientist leading a program at Stanford University, headed a team that successfully grew human brain tissue within mice.

Researchers removed most of the cerebral cortex and hippocampus from rodents, then replaced it with tissue derived from human stem cells in a process called xenocortication. This allowed human cells to integrate into the animal’s brain and occupy a large portion of its cranial cavity.

Previous attempts to transplant human brain tissue into mice failed because the host animal’s faster development overwhelmed the human graft. Pașca’s team overcame this by creating mice lacking a neocortex and hippocampus, then providing intensive care, including surrogate mothers and a high-calorie diet, to the pups. This enabled the implanted human tissue to grow and, over three months, form up to 92% of the animal’s cortical tissue, reaching a density of around 32,000 neurons per cubic millimeter.

The resulting brain tissue developed rare neurons not typically found in rodents, including layer-five projection neurons and Von Economo cells, neurons present in complex brains like those of humans and whales. This platform allows scientists to observe the development of human neural circuits and study conditions like autism and schizophrenia using living tissue, potentially speeding up drug development and offering insights unavailable from examining either mouse brains or human brains after death.

The team already used this method to identify a potential drug for Timothy syndrome, a rare genetic disorder, which is now in human trials.