Scientists grew lab-grown brain organoids and discovered they possess biological clocks
Researchers from Harvard University have grown brain tissue from stem cells, maintaining its activity for six years. The findings revealed internal "biological clocks" within nerve cells, offering new avenues for studying autism and schizophrenia.
How can the human brain be studied over many years without harming a living person? Until recently, this question was one of science's greatest riddles. Now, a team of researchers from Harvard University has presented a significant breakthrough: they utilized human stem cells—cells capable of transforming into any tissue in the body—to grow tiny three-dimensional structures of brain tissue known as "organoids." The researchers managed to keep these "tiny brains" alive and active for nearly six years, whereas previous models survived for only a few months.
The achievement, published in the journal Nature, demonstrated that these brain tissues not only survived but continued to develop naturally: the cells created neural connections—synapses—and automatically generated continuous electrical activity for two years.
One of the surprising discoveries was that the cells continued to "count time." By testing molecular markers indicative of biological age, the researchers found an almost perfect match: a five-year-old organoid displayed the genetic characteristics of a four-year-old child's brain.
"The cells recorded the passage of time in their gene activity," explained Prof. Paola Arlotta, who led the research.
To allow them to live longer, the team developed a special nutrient medium that preserved electrical activity, acting as a form of "fitness workout" that maintains cellular vitality.
The cells' "internal clock"
During the experiment, the researchers discovered that the cells possess an internal "developmental compass." When young cells were mixed with older ones in the same organoid, a laboratory phenomenon occurred: the young cells "trained" the older ones, accelerating the creation of new nerve cells. Simultaneously, older cells were able to shorten processes, creating mature nerve cells in just two weeks—a cycle that typically takes about two months. This finding proves that the cells precisely recognize their position on the timeline.
Because human brain development is a slow process spanning approximately 20 years, experiments on laboratory animals do not provide an accurate picture. This new model allows, for the first time, a detailed study of how a human brain develops over many years.
"These models give us a rare opportunity to understand in depth how conditions like autism and schizophrenia are created and develop in later stages of life," explained Dr. Andrea Beckel-Mitchener from the US National Institute of Mental Health (NIH).
In the scientific community, it is clarified that these are not real or thinking brains: the tiny tissues are very simple, are not connected to sensory input or blood vessels, and lack consciousness. The research was conducted under the strict ethical supervision of Harvard University in accordance with the most stringent international procedures.
