Social Isolation Disrupts Myelin Production

Social isolation is a common malady in early adulthood and can become chronic.

Focusing on this significant health issue, a new study shows how social isolation disrupts myelin, a protein crucial to the development of the nervous system's support cells.

The study conducted by researchers at the University of Buffalo and Mt. Sinai School of Medicine on mice reveals that prolonged period of social isolation produces less myelin in the region of the brain responsible for complex emotional and cognitive behavior.

Through this research the researchers throw new light on brain plasticity and its ability to adapt to the changing environmental conditions. 

According to the paper's lead authors, Karen Dietz, Ph.D, research scientist at Buffalo University, neurons aren't the only brain structures that undergo changes in response to an individual's environment and experience.

The research talks of the changes in the brain's white matter, or myelin that have been seen before in psychiatric disorders. It was noticed amongst the young animals how environmental conditions led to myelin changes.

"This research reveals for the first time a role for myelin in adult psychiatric disorders," Dietz says. "It demonstrates that plasticity in the brain is not restricted to neurons, but actively occurs in glial cells, such as the oligodendrocytes, which produce myelin."

 Myelin is an insulating layer that forms around nerves, including those in the brain and spinal cord. It is composed of about 80 percent lipid and 20 percent protein. Normal nerve function is lost in demyelinating disorders, such as multiple sclerosis and the rare, fatal, childhood disease, Krabbe's disease.

The paper highlights that stress of social isolation disrupts the sequence in which the myelin-making cells, the oligodendrocytes, are formed.

To prove the hypothesis, the researchers isolated the adult mice for nearly eight weeks to induce a depressive like state. They were later introduced to a new mouse, one they hadn't seen before. While mice are normally highly motivated to be social, they noticed that those who had been socially isolated did not show any interest in interacting with the new mouse. This behaviour was interpreted as a new model of social avoidance and withdrawal.

Brain tissue analysis of the socially isolated animals revealed significantly lower than normal levels of gene transcription for oligodendrocyte cells in the prefrontal cortex, a brain region responsible for emotional and cognitive behavior.

"This research provides the first explanation of the mechanism behind how this brain plasticity occurs," says Dietz, "showing how this change in the level of social interaction of the adult animal resulted in changes in oligodendrocytes." 

The key change was that cellular nuclei in the prefrontal cortex contained less heterochromatin, a tightly packed form of DNA material, which was unavailable for gene expression.

"This process of DNA compaction is what signifies that the oligodendrocytes have matured, allowing them to produce normal amounts of myelin," says Dietz. "We have observed in socially isolated animals that there isn't as much compaction, and the oligodendrocytes look more immature. As adults age, normally, you would see more compaction, but when social isolation interferes, there's less compaction and therefore, less myelin being made."

The research also highlighted that myelin production was back to normal after a period of social integration. This indicates that environmental intervention was sufficient to reverse the negative consequences of adult social isolation.

"The new paper, together with a report published earlier this year by another group showing myelin changes triggered by social isolation early in life, will broaden investigations into brain plasticity," says  Dietz.

"This research suggests that maybe recovery from an MS episode might be enhanced by social interaction," she says. "This opens another avenue of investigation of how mood and myelin disorders may interact with one another." Major funding for the research came from the National Institutes of Health.