The Unexpected Role of Microglia

Anxiety disorders affect roughly one in five people in ⁤the United States, making them among the most widespread mental health challenges. Although common, ⁢scientists still have many questions about⁣ how anxiety begins⁤ and⁢ is controlled within the brain. New ​research from the University of Utah‍ has now pinpointed two unexpected groups​ of brain cells in mice that behave like “accelerators”‍ and ‍”brakes” for anxious behavior.

The team discovered that the cells responsible ⁣for adjusting‌ anxiety levels are not neurons, which typically relay long-distance electrical signals and form circuits throughout the body. Instead, a specific class of immune cells known as microglia appears to play a⁤ central role in determining whether ⁢mice show​ anxious behavior.One subset of microglia increases ⁣anxiety responses, while another reduces them.

“This is a paradigm shift,” says Donn Van Deren, PhD, a postdoctoral research fellow⁢ at the University of pennsylvania who carried out the work while at University of ⁢Utah Health. “It shows that when the brain’s immune system ⁤has a defect and is not healthy,it can result⁤ in very specific neuropsychiatric disorders.”

From Confusing Results ‍to a Dual-Action System

Earlier experiments had ⁤already suggested that‌ microglia influence anxiety,but researchers initially believed that ‌all microglia functioned in the same way. When they interfered ‍with a particular subset known as Hoxb8 microglia,the mice began behaving as though ⁣they were anxious. However, when researchers blocked the ‌activity of ⁢all ‌microglia at once, including both Hoxb8 and non-Hoxb8 ‌groups, the mice behaved ‌normally.

These confusing results led the team to suspect that ‌the two types of microglia might work in opposite directions. Hoxb8 microglia might ‍help prevent anxiety, while non-Hoxb8 microglia might promote it. Further investigation confirmed this hypothesis: activating non-Hoxb8 microglia increased anxiety-like ​behavior, while ⁢activating Hoxb8 microglia reduced it.

“It’s like there’s a gas pedal​ and a brake pedal,” explains Van Deren in a University of Utah News release. ⁢”One type of microglia is pushing anxiety up, and the other is pushing it down.”

Microglia: More Than Just brain Cleaners

For years, microglia were primarily understood as the brain’s resident⁢ immune cells, responsible for clearing debris and fighting off infection. However, recent research has revealed a‍ much more complex role for these cells in brain development ‍and function, including synaptic pruning-the ​process of eliminating unnecessary connections between neurons.

this new ⁢study adds another layer to that complexity, demonstrating that microglia can ​directly modulate behavioral states. The researchers used single-cell RNA sequencing to⁢ analyze the gene expression profiles of ⁢the two microglia subtypes,