They managed to create mini-brains with functional blood-brain barriers

For the first time, scientists have succeeded in developing miniature models of the human brain incorporating the blood-brain barrier (BBB), a vital safety system that protects our brains from harmful substances. These models, the size of a sesame seed, represent a significant advance in the study of neurological diseases.

The blood-brain barrier: a guardian of the brain

The blood-brain barrier (BBB) ​​plays a vital role in protecting the brain from potentially harmful substances. It functions as a selective filter by lining the blood vessels of the brain and allowing only certain essential substances, such as hormones and glucose, to pass through.

At the same time, she blocks the entry of toxins and bacteria. However, this same protection poses a significant challenge for the development of medical treatments, because the BBB also prevents many drugs from entering the brain.

Ziyuan Guo, a neurobiologist and co-author of the study, points out that the absence of a human model Authentic BBB has been a major obstacle to research into neurological diseases.

Until now, scientists have relied on animal models to study the BBB and brain development. However, they do not accurately reflect the characteristics and functioning of the human brain. The differences between animal and human brains are indeed significant, limiting the accuracy of research and conclusions drawn from animal studies.

It is here that the new miniaturized models of the human brain come into play. These are in fact designed to more precisely imitate the development and functionality of the human brain, including the blood-brain barrier. By creating miniature replicas of the human BBB, scientists can study its behavior and reaction to different substances in a context that is much closer to reality.

The blood-brain barrier lines the blood vessels that pass through the brain and deliver nutrients and sugar to the organ. Credits: by Ben Brahim Mohammed, CC BY 3.0

Assembloids: a revolutionary new technology

In detail, these models combine brain organoids (three-dimensional clusters of brain cells cultured from stem cells) with blood vessel organoids that mimic the body’s vascular system. Together they form “assembloids” which simulate the growth and interaction of maturing brain cells and blood vessels.

A month after being combined, the two types of organoids merged into spherical structures, each measuring approximately the size of a sesame seed.

To demonstrate the utility of these models, the researchers cultured assembloids with cells from patients with cerebral cavernous malformation. This abnormality is characterized by abnormally shaped blood vessels in the nervous system. It sometimes results from genetic mutations and can cause serious symptoms like strokes and seizures.

The assembloids thus have developed the cellular characteristics of this malformationthus offering new information about it.

Initial tests show that these assembloids can be cultured for five months or more. This growth period roughly corresponds to the second trimester of brain development in utero.

In the future, the team of researchers plans to cultivate similar assembloids using stem cells from people with different brain diseases. This would allow the creation of models reflecting the underlying biology of various neurological pathologies.

Note that these assembloids are not only promising for the study of brain diseases. They could also be used to test new drugs, study how toxins damage the brain and the blood-brain barrier, and discover new strategies for delivering drugs across it.

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