Science & technology

Stanford Grows Mice With Half-Human Brains

Are 90% human-brain mice the breakthrough model neuroscience needed or a chimera outpacing our ethical guardrails?

Published 1 day ago

Stanford Grows Mice With Half-Human Brains

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Above: Stock image of a lab rat. Image credit: Stefan Klein/ullstein bild/Getty Images

The Facts

Researchers at Stanford University reported Wednesday in the journal Nature that they had transplanted lab-grown human brain tissue into mice genetically engineered to lack a cortex and hippocampus, creating animals whose brains are about half human by volume.
Max Kozlov on X
Nature
The Scientist
The newborn mice received injections of roughly 100,000 human cells derived from reprogrammed donated skin cells. The rodents lacked about 14 million mouse brain cells and ended up with as many as 4 million human neurons, researchers said.
The Guardian
NPR
Two to three months after the procedure, the grafted tissue had expanded nearly fivefold, connected to the mouse blood supply and filled more than 90% of the empty cavity, with projections reaching into the animals' spinal cords.
Nature
Science
Behavioral testing showed the animals were not enhanced by the transplants, said lead researcher Sergiu Pasca. Madeline Lancaster of the MRC Laboratory of Molecular Biology said none of the mice's behavior was made up of human behavior.
BBC News
The New York Times
The grafts produced von Economo neurons, cells linked to social cognition that had never been grown in a dish and previously studied only in autopsied brains. They are among the first cells to die in frontotemporal dementia.
The Scientist
STAT
Five hours of low oxygen damaged the human neurons and impaired the mice's gait and balance, pointing to uses in studying cerebral palsy. Limitations include immature tissue and no clear cortical layering, co-author Kevin Kelley said.
The Telegraph
The Guardian
Kevin Kelley on X

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The Spin

Narrative A

Finally, a model that breaks the wall between lab dishes and real human neurobiology. Human cortical cells grown in mice missing their own cortex expand, wire into the nervous system, reach the spinal cord and even produce specialized neuron types that never show up in a dish. That means real testing grounds for cerebral palsy, dementia and neurodevelopmental disorders — and behavioral tests show no boost to rodent smarts.

Sergiu P. Pasca on X

Nature

Narrative B

Though extraordinary, growing mice with brains that are more than 90% human-derived tissue is a milestone that current oversight systems were never built to handle. Nobody can yet say whether these chimeras carry any human-like capacities of consciousness or cognition, and one-protocol-at-a-time review boards have no view of the field as a whole. Guardrails must be built now, with patients, ethicists and the public as co-designers.