Animals that are socially isolated for long periods make less
myelin in the region of the brain responsible for complex emotional
and cognitive behavior, according to researchers at UB and Mt.
Sinai School of Medicine.
Their findings, published
online in Nature Neuroscience, show that brain
plasticity—the brain’s ability to adapt to
environmental changes—occurs not only in neurons but
myelin-producing glial cells as well.
“This research provides the first explanation of the
mechanism behind brain plasticity,” says Karen Dietz, PhD,
research scientist in pharmacology and
toxicology and one of the paper’s lead authors.
Dietz and her colleagues found that the stress of social
isolation disrupts the sequence in which oligodendrocytes, the
myelin-making cells, are formed.
Their experiment involved isolating adult mice for eight weeks
to induce a depressive-like state. Although mice are typically
social, the isolated animals showed no interest in interacting with
a mouse they hadn’t seen before.
Brain tissue analyses of the isolated mice revealed that the
oligodendrocytes had significantly lower than normal levels of
heterochromatin, a tightly packed form of DNA, in the prefrontal
cortex.
DNA compaction signifies that the oligodendrocytes have matured.
This, in turn, allows the oligodendrocytes to produce normal
amounts of myelin, the fatty material crucial for a properly
functioning nervous system.
“As adults age, you would normally see more compaction,
but when social isolation interferes, there’s less compaction
and, therefore, less myelin being made,” Dietz says.
The research also showed that myelin production returned to
normal after a four-week period of social integration, suggesting
that environmental intervention reverses the negative effects of
adult social isolation.
Although myelin changes have been previously observed in
psychiatric conditions, this study is the first to indicate that
myelin plays a role in adult psychiatric disorders, Dietz
says.
Demyelinating disorders, which result in a loss of normal nerve
function, have been associated with depression, so the new research
also has implications for questions about multiple sclerosis and
other demyelinating conditions, she adds.
“The research suggests that recovery from an MS episode
might be enhanced by social interaction. It opens another avenue of
investigation of how mood and myelin disorders may interact with
one another.”
The new research—together with another group’s
showing myelin changes triggered by social isolation early in
life—is expected to broaden investigations into brain
plasticity.
Dietz conducted the study while a postdoctoral researcher at Mt.
Sinai. It was funded by the National
Institutes of Health.
David
Dietz, PhD, assistant professor of pharmacology and toxicology,
is one of the paper’s co-authors.
Their collaborators from Mt. Sinai are:
- lead author Jia Liu, PhD, postdoctoral researcher
- corresponding author Patrizia Casaccia, MD, PhD, professor of
genetics and genomic sciences, neuroscience and neurology
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