Within the past few years, scientists have successfully grown organs such as kidneys and livers in laboratories. It’s possible that some day, such lab-grown organs could be used as transplants, particularly when grown from the recipient’s own cells. Now, a team at the Institute of Molecular Biotechnology of the Austrian Academy of Sciences has succeeded in growing miniature human brains. While no one is suggesting that they could be swapped in for a patient’s existing brain, they could prove to be a boon to the field of medical research.

The team, led by Dr. Jürgen Knoblich, started by analyzing human stem cells – a cell type that has the capacity to change into any other type of cell found in the body. Specifically, the scientists were interested in discovering what growth conditions are required for such cells to differentiate into various types of brain tissue cells.

Once those conditions had been identified, stem cells were used to create neuroectoderm, a layer of cells which is the “starting material” from which all components of the nervous system (including the brain) are derived. Bits of that neuroectoderm were then placed within droplets of gel, which served as a three-dimensional scaffolding for tissue growth. That collection of seeded gel droplets was subsequently placed in a spinning bioreactor, to aid in the absorption of nutrients.

After spending 15 to 20 days in the reactor, the neuroectoderm fragments had formed into a piece of continuous brain tissue, known as a cerebral organoid. In the middle of that organoid was a fluid-filled cavity, that resembled a brain’s cerebral ventricle. By the 20 to 30 day mark, the tissue had differentiated into specific neural regions, including a cerebral cortex, retina, meninges (membranes that envelope the central nervous system) and choroid plexus (the area in the brain where cerebral spinal fluid is produced).

Comparison of one of the mini brains (right) to the developing brain of a mouse (left)

The little brains reached their maximum size after two months, although they continued to thrive – they’re presently 10 months old, and still going. The scientists believe that growth halted due to the lack of a circulatory system.

It is now hoped that such lab-grown brains could be used as models for understanding brain disorders, and the testing of treatments. Already, Knoblich’s team has had some success in that area.

The researchers created some of their mini brains using stem cells from someone suffering from microcephaly, a disorder in which the brain is unusually small. Sure enough, the brains that they created were even smaller than the regular mini brains. Upon analyzing them, however, the scientists discovered that their diminutive size may be due to the fact their brain cells differentiate prematurely, and that a change in the direction in which they divide may also play a part in the disorder.

A paper on the research was published yesterday in the journal Nature.

Source: Institute of Molecular Biotechnology via New Scientist