Researchers at Harvard University have grown human brain organoids for approximately seven years, far exceeding the typical lifespan of a few months for such lab-grown structures. The peppercorn-sized clumps of neural tissue, derived from stem cells, continued to change and mature over the years despite developing outside an embryo or body.
Senior author Paola Arlotta, a professor at Harvard, said the organoids "recorded the passage of time and retain a memory of the developmental steps already performed" on a cellular level. This does not imply consciousness or human-like memory, but rather that the cells' past developmental state is molecularly engraved.
The team used three recently developed genetic clocks to assess the biological age of the organoids. All three clocks indicated the lab-grown cells aged in patterns similar to normal human brain cells, confirming they followed a natural developmental trajectory over the extended period.
In a separate experiment, researchers combined organoid cells that had developed for one year with cells only two weeks old. The older cells accelerated their development, beginning to produce neurons that typically require around four months to form. Arlotta described this as effectively "warping time" for brain development.
The previous record for sustaining brain organoids was just under two years. Scientists hope these long-lived models will help reveal how disorders such as autism and schizophrenia emerge and progress across the lifespan, and allow drug testing without relying on animal models.
Arlotta emphasized that organoids are "biological models" or "avatars" far less complex than actual brains, lacking sensory input and higher-order functions. The scientific consensus holds they are not capable of consciousness. The organoids used in this study were destroyed after the experiments concluded.
The study was published in the journal Nature. Researchers noted that unlike brains in a body, organoids do not face systemic illness, raising the theoretical question of how long they could survive, though Arlotta said "nobody really knows" the upper limit.
Oldest human brain cells grown in lab 'recorded passage of time'
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