Lab-Grown Human Brain Organoids Developed for Seven Years, Study Finds

Tiny clusters of human brain cells grown in a laboratory continued developing for roughly seven years, according to research reported by Phys.org and published in Nature. The period makes them the oldest human brain organoids described in the study, surpassing the previous record of just under two years. Brain organoids are peppercorn-sized structures made from stem cells. Researchers use them as simplified biological models to study human brain development and investigate conditions including autism and schizophrenia. Because most organoids survive for only a few months, they have generally offered a view of early development rather than the brain’s longer trajectory. The Harvard-led team found that the organoids kept changing and maturing even though they had never developed inside an embryo or a human body. Researchers used three recently developed genetic “clocks” to estimate the cells’ biological ages. Each indicated that the organoids changed over time in ways broadly similar to ordinary brain cells. The study described the organoids as having “recorded the passage of time,” but that phrase refers to cellular development rather than conscious memory. Paola Arlotta, the study’s senior author, emphasized that the cells did not remember events in the way a person might recall childhood. Their developmental history was instead retained at a biological level. In another experiment, the researchers combined cells that had been developing for about a year with cells only two weeks old. The younger cells followed their expected developmental pattern, while the older cells moved ahead and began producing neurons associated with a later stage—one that would normally take about four months to reach. Arlotta characterized the result as effectively warping developmental time. The researchers said this approach might eventually help scientists speed up the development of particular brain-cell types for study. They also noted that organoids are far less complex than human brains, receive no sensory input, and are widely understood by scientists not to possess consciousness or higher-order brain functions. The organoids used in the research were recently destroyed. Whether such lab-grown structures could theoretically survive longer than a human lifespan remains unknown; Arlotta said she suspected they might last somewhat longer, but offered no firm conclusion.