Transplanting human tissue into animals

Nearly one in five Americans lives with a mental illness. Unfortunately there’s a limited set of options for treating psychiatric disorders. One reason for that is that these disorders are still defined based on people’s behavior or invisible internal states — things like depressed mood or hallucinations.

But of course, all our thoughts and behaviors are governed by our brains.  And there’s a lot of research that makes it clear that many disorders, including schizophrenia, autism, and probably depression, may have their origin during early-stage brain development. The problem is that we still don’t know which brain circuits specifically are responsible for these disorders — or how they got that way.

Studying human brain circuits as they develop is — obviously — challenging. But what if we could rewind the clock and follow the development of neurological circuits in real time? Believe it or not, new technologies may soon make  this  possible.

Today's guest is Sergiu Pasca, Kenneth T. Norris, Jr. Professor of Psychiatry and Behavioral Sciences at Stanford University School of Medicine and Bonnie Uytengsu and Family Director of the Stanford Brain Organogenesis Program at the Wu Tsai Neurosciences Institute.

Pasca and his team have developed techniques to create tiny models of a patient's brain tissue in the lab — models called brain organoids and assembloids. They can watch these models grow in lab dishes from a few cells into complex circuits. And they can even transplant them into rats to see how they integrate into a working brain.

While all this may sound like science fiction, these techniques are fueling a revolution in scientists' ability to observe human brain development in real time, trace the origins of psychiatric disorders and — hopefully — develop new treatments.

Further Reading

• Reverse engineering human brain by growing neural circuits in the lab | Wu Tsai Neuro
• Human brain cells transplanted into rat brains hold promise for neuropsychiatric research | News Center | Stanford Medicine
• Sergiu P. Pasca: How we're reverse engineering the human brain in the lab | TED Talk
• Assembloid models usher in a new era of brain science | Stanford Medicine
• Human Brains Are Hard to Study. Sergiu Paşca Grows Useful Substitutes. | Quanta Magazine

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