Scientists Grow Miniature Human Brains in Mice – Innovita Research

Back in 2013, researchers achieved human brain organoids for the first time, which they had eventually managed to induce to form structures like those seen in the brains of foetuses. The problem with the brainy organoids is their short life-span.

“In our hands, the organoids stop growing around five weeks,” said Fred Gage of the Salk Institute. “It’s a function of size rather than time. We see some cell death even in the edge of the organoids starting at 10 weeks, which becomes really dramatic over time. This is an obvious hurdle for long-time study.”

A potential solution to the premature death of cerebral organoids was announced in a report published in the journal Nature Biotechnology, on Monday by researchers from the Salk Institute for Biological Studies in the US.

In the report, the researchers describe how they took human brain organoids which had been growing in lab dishes for 31 to 50 days and implanted them into mouse brains by first scooping out a small amount of native tissue.

Researchers implanted mini human brains into the skulls of mice, leaving a transparent cover, which displayed the engineered implanted cells in fluorescent green. Image credit:, CC0 Public Domain.

Around 80 percent of the implants took, and were sprouting additional neurons within 12 weeks. By 14 days almost all of the organoids developed a dense network of blood vessels carrying nutrients and oxygen – a process which does not take place when growing the organoids on a petri dish.

The new technique allowed the miniature human cerebrums to develop normally and to survive for up to 233 days – well beyond the “shelf-life” of their counterparts grown in the lab.

While the organoids were found to send axons into the native neurons of the host, behavioural tests did not indicate any differences compared to regular mice. The short-lived memory advantage found early on completely disappeared the very next day.

However, the test used to gauge the ability of the mice was very simple and specific, prompting Gage to claim that it’s much too early to be making any strong general conclusions in terms of the cognitive abilities, and even much less so – subjective experiences, of the mice in the study.

Successful application of the new technique could aid researchers in studying the brain not only under normal conditions, but also under pathological ones, such as in the case of schizophrenia.