Level 1 - Absolute Beginner
Scientists did a new experiment with brain cells. The work comes from a team at Stanford University in the United States.
They grew small balls of human brain cells in a lab. These balls are called organoids. They put them into baby mice.
The mice did not have most of their own cortex. The cortex is the top part of the brain.
The human cells grew a lot. They made links with the mouse brain. The cells are still very young. Scientists hope to learn about brain illness.
- scientist
- A person who studies nature and the world.
- brain
- The part of the body that thinks.
- cell
- A tiny living part of the body.
- lab
- A room where scientists work.
- mouse
- A small animal with a long tail.
- cortex
- The top layer of the brain.
- grow
- To get bigger.
- illness
- Being sick.
Level 2 - Elementary
A study in the journal Nature describes a new way to study the human brain. Coverage credits a team at Stanford University led by Sergiu Pasca. The Nature issue of October 8 also carried a News and Views article about the work.
The team grew human cortical organoids, which are small clumps of brain cells made in the lab. They placed them into mice that were engineered to lack most of their cortex and hippocampus, two important brain areas.
The grafted human tissue grew a great deal. It turned into many types of human nerve cells and formed circuits that joined the mouse brain. After about three months it had long connections and organized electrical activity.
The tissue stays immature. Reports compare it to a fetal brain in mid pregnancy, without the six layers of a grown cortex. Scientists say the mice could help test ideas about autism and other conditions.
- journal
- A magazine where scientists publish their studies.
- clump
- A small group stuck together.
- engineered
- Changed on purpose using science.
- hippocampus
- A brain area linked to memory.
- graft
- To place living tissue into another body.
- circuit
- A path along which signals travel.
- immature
- Not fully grown.
- condition
- A health problem.
Level 3 - Intermediate
Human brain tissue grown in a dish has been made to thrive inside a living mouse brain that is largely missing its own cortex, according to research published in Nature and described in an accompanying News and Views article in the journal's October 8 issue. Coverage attributes the work to a Stanford University group led by Sergiu Pasca, and calls the animals xenocortical mice.
The researchers started with human cortical organoids, clumps of cells coaxed to form the kind of tissue found in the outer brain. They transplanted these into mice that had been genetically engineered so that most of the neocortex and hippocampus never formed, leaving room for the foreign tissue to expand.
The grafts grew extensively, matured into a wide range of human neural cell types and organised themselves into circuits that integrated with the host brain. By three months, the human tissue had made long range connections to the mouse nervous system and was producing organised electrical activity.
The limits are as important as the promise. Reports stress that the tissue remains extremely immature, closer to a mid gestation fetal brain than an adult one, and does not develop the six layered structure of a mature cortex. Still, a living model with human cells could help researchers test how conditions such as autism and schizophrenia arise, while raising questions about how far such chimeras should go.
- thrive
- To grow strongly and healthily.
- accompanying
- Appearing together with something else.
- coax
- To gently persuade or guide.
- neocortex
- The newest and largest part of the cortex in mammals.
- integrate
- To combine so that parts work together.
- gestation
- The time of development before birth.
- chimera
- A living thing made of cells from different species.
- host
- The living body that receives a graft.
Level 4 - Advanced
A Nature paper, and the News and Views commentary that accompanied it in the 8 October issue, describes an audacious chimera: human cortical organoids that have colonised the brains of mice engineered to lack most of their own neocortex and hippocampus. Coverage credits the Stanford laboratory of Sergiu Pasca, and the animals have been dubbed xenocortical mice.
The logic of the experiment is to remove the competition. Earlier transplants went into an intact cortex, where the graft had to share space with the host tissue. Here the graft inherits the real estate. It grew extensively, differentiated into a diverse range of human neural cell types and organised into circuits that integrated with the host, and by three months it had established long range connections with the mouse nervous system and produced organised electrical activity.
Candour about the limits runs through the reporting. The tissue remains extremely immature, nearer to a mid gestation fetal brain than to an adult one, and it lacks the six layered architecture that defines a mature cortex. A mouse brain also supplies the wiring, blood supply and sensory input, so what is being modelled is development in a hybrid setting, not a human mind in miniature.
Even so, the approach opens a route to studying disorders such as autism and schizophrenia in living human tissue that develops over months rather than days. It also revives an old bioethical debate about chimeras and the degree of humanisation that is acceptable in animal hosts, a debate that will now be conducted with data rather than speculation.
- audacious
- Boldly daring, even shocking.
- colonise
- To spread through and settle in a place.
- dub
- To give a name or nickname to.
- differentiate
- To change into a specialised kind of cell.
- candour
- Honest and open speech.
- architecture
- Here, the structure and organisation of tissue.
- humanisation
- Making something more human in character.
- speculation
- Guessing without firm evidence.
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