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From Sci-Fi to Medical Research: Brain Organoids

Sofia Cruz Tetlalmatzi 

posted: January 31st, 2019

Imagine a living, thinking human brain grown out of a test tube. Straight out of a sci-fi movie isn’t it? Well, turns out that this might not be as farfetched as you would’ve thought. Today, scientists are able to grow mini brains that present active neural networks. Long term maturation of these brain organoids allows them to have oscillatory activity, like the brain waves typically observed in human brain encephalographies.

During gestation, as cells divide, they differentiate and organize to form the tissue and organs that conform a living being. By this same principle, culturing pluripotent stem cells should give rise to differentiation. When allowed to grow in 3D, whether by floating freely in solution or by being embedded in some culture matrix, these cells will self-organize on their own into brain like spheres, forming organoids.

These organoids have already been used in medical research. Notably, in Brazil, there was an observed correlation between the circulation of Zika virus and an outbreak of microcephalic cases. To test this relationship, brain organoids were exposed to Zika virus. This revealed that the virus was killing early progenitor cells in the cortical layers. Furthermore, the brain organoids were also used to test drugs to prevent infection or inhibit viral replication.

However far we’ve come, our sci-fi picture is still a long way ahead. The brain organoids alone cannot develop more organized structures because there are pieces missing: glia and blood.  Glia can be produced separately and then incorporated, but vascularization is more difficult to achieve. The lack of blood prevents nutrients from reaching to inner cells of the organoids, causing necrosis.

But, are these brain organoids functional at all? Currently, it is unknown whether the neurons in brain organoids are creating circuitry or if they are randomly connected.  Moreover, the inability of comparing brain organoids to brains in utero further complicates the assessment of the organoid’s success.  Still, there is much left to learn from today’s mini brains, and before you know it, we’ll be living that sci-fi movie you imagined.

 

Source:

Trujillo, C. A., & Muotri, A. R. (2018). Brain Organoids and the Study of Neurodevelopment. Trends in Molecular Medicine, 24(12), 982–990. https://doi.org/10.1016/j.molmed.2018.09.005