by Sharon Begley, Stat
Minuscule blobs of human brain tissue have come a long way in the four years since scientists in Vienna discovered how to create them from stem cells.
The most advanced of these human brain organoids — no bigger than a lentil and, until now, existing only in test tubes — pulse with the kind of electrical activity that animates actual brains. They give birth to new neurons, much like full-blown brains. And they develop the six layers of the human cortex, the region responsible for thought, speech, judgment, and other advanced cognitive functions.
These micro quasi-brains are revolutionizing research on human brain development and diseases from Alzheimer’s to Zika, but the headlong rush to grow the most realistic, most highly developed brain organoids has thrown researchers into uncharted ethical waters. Like virtually all experts in the field, neuroscientist Hongjun Song of the University of Pennsylvania doesn’t “believe an organoid in a dish can think,” he said, “but it’s an issue we need to discuss.”
Those discussions will become more urgent after this weekend. At a neuroscience meeting, two teams of researchers will report implanting human brain organoids into the brains of lab rats and mice, raising the prospect that the organized, functional human tissue could develop further within a rodent. Separately, another lab has confirmed to STAT that it has connected human brain organoids to blood vessels, the first step toward giving them a blood supply.
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