Miniature human brain model, complex organ secret unlocking key
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Neurons (green) are moving inside a laboratory-raised brain model called assembloid, built from organoids. Credit: Sergiu Pasca's Lab, Stanford University
Neurons (green) are moving inside a laboratory-raised brain model called assembloid, built from organoids. Credit: Sergiu Pasca's Lab, Stanford University
The human brain is one of the most complex organs. Tens of billions of cells are built precisely, moving to the right location, separating into thousands of different types of cells, and creating delicate neural networks. Most of the processes start from the embryonic stage and continue to develop through early adulthood. The study of this complex process is difficult. Scientists rely on limited animal models or human brain tissue. However, "organoids," or small organ models cultured in the laboratory, have completely changed the idea of studying this biological process. This brain organoid is built from early cells. Induced pluripotent stem cells, which are adult cells that are reprogrammed to reverse their initial state. These cells can develop into a three-dimensional structure that mimics the early brain, although not as complete as the real brain, but they can reflect their developmental patterns and biological time sequences.
This key breakthrough came when researchers accidentally discovered that cells could coalesce into brain-like structures themselves, leading to experiments creating human brain organoids that can grow for months and show unique characteristics of the human brain, such as the presence of a special type of stem cell called outer radial glia, which is associated with brain enlargement in humans.
Some brain organoids (Brain organoids) can live for months, maybe even years, inside the laboratory Credit: Timothy Archibald
Some brain organoids (Brain organoids) can live for months, maybe even years, inside the laboratory Credit: Timothy Archibald
Organoids have become an important tool for studying both development and brain diseases. Researchers have been able to simulate diseases such as microcephaly, which have been found to be caused by neural stem cells that stop proliferation too quickly or study infections such as Zika virus that directly affect brain development. Scientists have also developed the concept "assembloids," which are to combine organoids from different parts of the brain to study neural circuits. For example, the connection between the cerebral cortex and the part that controls the suppressed neurons, which helps to understand the balance of neural circuits associated with diseases like autism and schizophrenia. Another approach. The chimeroids, which mix cells from different individuals to study the difference in response to drugs or neurodiversity at the cellular level.
Although organoids open the door to new understanding, there are important constraints, such as complexity that does not yet have a real brain equivalent, culture is difficult and requires a long period of time, and ethical questions that are beginning to be raised, especially the issue of whether organoids may develop to a level of "consciousness," which most scientists agree is far from that point. Another challenge is "time." The human brain takes years to develop, but research needs quick answers. Scientists are trying to speed up the development process in the laboratory, although the full impact of accelerating these processes is not yet understood. However, medical hopes are approaching. True, researchers began planning the first clinical trials of organoid-developed treatments, targeting genetic diseases that affect the brain, which could be a major step toward treating diseases that were once difficult to reach.
Brain organoids are changing the way they study the most complex organs in the body, from what used to be difficult to access, to more observable, experimental and understandable systems, and in the coming decades, this technology may help uncover the foundations of brain diseases and lead to more accurate new treatments.
