Researchers at Harvard University have successfully kept human brain organoids alive for almost six years, significantly exceeding the typical lifespan of such cultures. During this extensive period, the cells within these organoids continued to develop at a rate comparable to that of actual human brain cells.
Brain organoids are small-scale biological models composed of various living neural cells that establish connections and communicate with each other. The scientists examined organoids of different ages, ranging from a few weeks to five years, analyzing over 400,000 cells in total.
Remarkably, the findings revealed that these cells adhere to a "biological calendar." Changes in gene expression were consistent with the actual time each organoid spent in the laboratory. For instance, molecular differences were noted between one-year-old cells and those that were three or five years old, reflecting the natural progression of brain development.
To further investigate how well these cells "remember" their age, the researchers created chimeric organoids using both young and old cells. The older cells were found to bypass certain developmental stages they had previously experienced, producing more mature neuron types much faster than expected. A process that typically takes over two months was achieved in just about two weeks by these cells.
The researchers characterize this phenomenon as a form of memory regarding the passage of time, suggesting that these cells possess an intrinsic mechanism that regulates the pace of human brain maturation.
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