Lab-Grown Human Brain Cells Kept Alive for Record Seven Years Aged Like a Real Brain

Peppercorn-sized clumps of human brain cells called organoids are grown from stem cells by scientists to study how brains develop and to test new medicines without using animals. Normally these organoids live for only a few months, offering a window into just the earliest stages of human brain development, which takes nearly 20 years to complete in a real person.

A US-led team grew organoids for around seven years, making them the oldest ever, more than three times longer than the previous record of just under two years, said Paola Arlotta, senior author of the study and a Harvard University professor. The organoids continued to change and mature over the years despite never being inside an embryo or a body, showing that "the brain can continue to develop outside the context of a person for this unprecedented amount of time," Arlotta said.

The study, published in the journal Nature, found the organoids "recorded the passage of time and retain a memory of the developmental steps already performed," as shown by three different genetic "clocks" that estimate the biological age of cells, all of which showed the organoids aging similarly to normal brain cells. In a further experiment, researchers mixed cells that had developed for a year with cells only two weeks old; the young cells behaved normally, but the older cells "jumped ahead a whole chunk of development," producing in weeks neurons that normally take around four months to form.

Arlotta said organoids are "biological models" that are far less complex than a real brain, do not receive sensory input, and are not considered capable of consciousness or other higher-order brain functions. Researchers hope the work could help reveal how disorders such as autism and schizophrenia emerge and progress, and Arlotta speculated the technique could one day be used to speed up the development of certain brain cells. The organoids used in this study were recently destroyed after the research concluded.