Obsessive-compulsive mice, which were once pulling their hair out from too much grooming, are now sitting pretty. Their cure? A bone marrow transplant. In a study published today in Cell, scientists show an unsuspected link between a psychological disorder and the immune system.
Here’s how they did it:
Step 1 – Finding the Problem
Since excessive cleaning is a behavior, scientists first thought to look for defects in the mouse brain. They noticed that mice with a mutant version of the gene Hoxb8 were the ones cleaning themselves bald. Hoxb8 is important for creating microglia–nervous system repair cells that search for damage in the brain.
Although some microglia start out in the brain, others are born in the bone marrow and move in. Overall, adult mice with faulty Hoxb8 harbored about 15% fewer microglia in the brain than normal. [ScienceNow]
Since many microglia move from bone marrow to brain, the scientists decided to give the compulsive mice, with the mutant Hoxb8 gene, a marrow transplant.
Inserting a “pacemaker” into the brain to emit regular pulses of electricity and quell disordered neural activity may sound like a therapy of last resort, but if current experiments show beneficial results the brain surgery may one day be commonplace. But some scientists are cautioning that research on so-called deep brain stimulation may be pressing ahead too quickly, and warn that long-term effects of the surgery are not yet clear.
A growing number of psychiatric researchers are testing the method’s effectiveness on a host of psychiatric disorders. Until recently, deep brain stimulation was approved in the U.S. only to treat certain movement disorders, primarily those of Parkinson’s disease, for which it diminishes tremors and rigidity and improves mobility. To date, more than 60,000 patients worldwide have had the devices implanted [Los Angeles Times]. But now large clinical trials are in the works that will test the use of deep brain stimulation for obsessive compulsive disorder, epilepsy, and depression. Smaller experiments are beginning to assess the therapy’s effectiveness on a wide range of disorders including anorexia, drug addiction, obesity, traumatic brain injury, and Alzheimer’s.
Deep brain stimulation can now be used to treat obsessive compulsive disorder, or OCD, which causes uncontrollable worries and anxiety in its sufferers. Medtronic‘s Reclaim deep-brain stimulation (DBS) device received approval from the Food and Drug Administration after a study of 26 patients with severe OCD that showed a 40 percent reduction in symptoms after a year of deep brain stimulation therapy. All the patients had tried and failed other therapies [Chicago Tribune].
The Reclaim device is implanted under the skin of the chest and then connected to four electrodes in the brain. The electrodes deliver steady pulses of electricity that block abnormal brain signals [AP]; the device is controlled by a battery-run component outside the body. Hooman Azmi, a neurosurgeon at Hackensack University Medical Center, said, “This is essentially like a pacemaker for the brain” [WebMD Health News].
Both people with obsessive-compulsive disorder (OCD) and their unaffected family members show decreased activity in a brain region that’s key to decision-making, and researchers say the finding could help them identify people who are at risk of developing the disorder.
In a new study, volunteers performed a task that required mental flexibility, as the correct response changed over time. Researchers used a functional MRI to take brain scans during the experiment, and found that people with OCD and their relatives showed decreased activity in the orbitofrontal cortex. The region, located behind the eyes, helps us make decisions and keeps compulsive behaviors, such as gambling and excessive drinking, in check. Some studies have found abnormalities in this region in people with OCD, but its role in the disorder is unclear [ScienceNow Daily News].