Networks of cells small enough to fit on the head of a needle pin could give scientists an explosion of information about Down syndrome, Alzheimer’s disease, and the Zika virus.
These networks are called “minibrains,” and they’re a hot topic at the Society for Neuroscience meeting, currently being held in San Diego, California—where this research was announced. Minibrains start out as human skin cells, are raised in the lab to become neural stem cells, and then eventually differentiate into some of the cell types found in a real brain.
They also resemble actual neurons housed in a human brain in that they communicate similarly, and represent part of the brain’s cell diversity. This is important because animal models can only take human neuroscientific research so far.
A minibrain also grows the same way a real brain does during pregnancy (except that it stops growing once it reaches about 20,000 cells). That means researchers could connect the dots between brain vulnerability in utero and the Zika virus, which is associated with microcephaly (a birth defect) in babies who are exposed to it while still in the womb. Here’s Jon Hamilton, reporting for NPR:
When Zika began making headlines last year, scientists suspected the virus could interfere with brain development in the womb. “But you can’t study that in a mouse,” Ming said, because mice have very few of the developing brain cells that are most vulnerable to Zika infection.
A student suggested that Ming and Song use minibrains to figure out what was happening. So the couple contacted Hengli Tang, a research biologist they knew at Florida State University, who was studying the Zika virus.
That call led to studies of minibrains that showed precisely how the infection was attacking certain neural cells, especially at a point in development equivalent to the first trimester of pregnancy. “It was turning [these cells] into a viral factory,” Song said.
As a result, the minibrains infected with the virus early in their development actually decreased in size, which may help explain why a human fetus infected with the Zika virus early in pregnancy sometimes develops into a baby with a very small brain.
Perhaps more promising is minibrains’ potential to revolutionize drug manufacturing for brain disorders. Many powerful drugs for neurodegenerative diseases like Alzheimer’s and Parkinson’s have proved successful when tested in animal models, but appear flawed when tested in humans. Minibrains could help scientists find the right formula for drugs by illuminating how these diseases begin. And since no other species of animal gets Alzheimer’s, in particular, stem cells and the minibrains can play a vital role in finding treatments for this persistent disease.