Scientists from the United States and Israel have developed miniature three-dimensional (3D) models of the earliest developmental stage of the human central nervous system in laboratories, which have been growing for 40 days. This is the first time scientists have simulated all components of the embryonic brain and spinal cord in the laboratory, which is expected to deepen people's understanding of brain diseases that occur during early development. The related research paper was published in the journal Nature on the 28th. Organoid is a mini 3D model cultivated from live tissue, aimed at mimicking the unique complexity of human organs. In recent years, scientists have cultivated a large number of organoids, including brain organoids. But the research team stated that the latest achievement is the first time scientists have simulated all components of an embryonic brain in the laboratory: the forebrain, midbrain, hindbrain, and spinal cord. The new model uses human pluripotent stem cell cultivation. The team first formed a row of stem cells approximately 4.39 centimeters long and 0.018 centimeters wide, similar in shape and size to the neural tubes present in 4-week-old human embryos. Then, they inserted this row of cells into a microfluidic device containing many microchannels, exposing the cells to different chemicals, promoting cell growth, and forming a 3D structure similar to the early central nervous system. They also added a gel to drive stem cells to differentiate into neurons. Within 40 days, cells within organoids self-organized into structures similar to the early stages of human embryonic brain and spinal cord development, perfectly mimicking the developmental level of an 11 week old embryo. Researchers indicate that the new model still has some limitations. The neural tubes in organoids appear vastly different from those in humans, making them unlikely to be used for studying diseases caused by underdeveloped neural tubes. They hope to further improve and use stem cells collected directly from patients to study different human brain diseases. (Lai Xin She)