Miniature human brains coming up next?

The human brain is something so close to all of us, yet it remains one of humanity’s greatest mysteries. Understanding precisely how it develops and functions is one of the biggest challenges for modern science. A new way of trying to unfold its secrets involves growing a miniature brain in a lab.

To date, much has been discovered about the human brain by experiments using mice and rats. But there is an important difference between their brains and ours: whereas the mouse brain has a flat surface, the human brain has a surface that contains many ridges and folds. Some scientists believe that this difference, among other dissimilarities, might have prevented scientists from finding a cure for various brain diseases, such as schizophrenia and Alzheimer’s disease, in experiments using such animals.

In recent years, there has been a growing interest in conducting experiments using human brains.

The new approach uses human cells, such as embryonic stem cells and induced pluripotent stem cells, that can grow into any type of cell in the human body. After grown in a special culture dish for about a month, the cells develop into structures that are surprisingly similar to those of the brain of a 10-week-old embryo.

This miniature brain, referred to as a cerebral organoid, is now being used in various studies on brain diseases.

A group of researchers at the Institute of Molecular Biotechnology at the Austrian Academy of Sciences is using the brain-like structure to study microcephaly, a condition in which a person is born with an abnormally small head. The group found that the cerebral organoids grown from cells taken from people with microcephaly are significantly smaller than those developed under normal conditions. The group is currently studying the biochemical process responsible for causing microcephaly in a developing embryo.

Cerebral organoids are also facilitating studies of the Zika virus, a mosquito-borne virus that is believed to cause microcephaly in unborn babies of infected mothers. Recent studies in Brazil and the U.S. using these brains found evidence to support the hypothesized link between the Zika virus and microcephaly.

The researchers infected miniature brains made from healthy people with the virus. The results showed that the infected organoids’ nerve cells had been destroyed and that the organoids had become much smaller than noninfected ones.

Other scientists are working to develop new medicines using cerebral organoids. The mini brain allows scientists to see whether a new drug has the desired effects on brain structures — rather than by testing it on animals — at reduced development costs. Also, the method allows researchers to identify effects that are harmful to the brain of a developing embryo so that pregnant women can avoid taking those drugs.

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