Scientists at the University of Wisconsin, Madison say they have shown that sleep increases the reproduction of oligodendrocytes, which are the cells that form myelin. They published their research (“Effects of Sleep and Wake on Oligodendrocytes and Their Precursors”) in today’s issue of The Journal of Neuroscience and note that this work might lead to new insights about sleep’s role in brain repair and growth.
Scientists have known for years that many genes are turned on during sleep and off during periods of wakefulness. However, it was unclear how sleep affects specific cell types, such as oligodendrocytes, which make myelin in the healthy brain and in response to injury. Much like the insulation around an electrical wire, myelin allows electrical impulses to move rapidly from one cell to the next.
In the current study, Chiara Cirelli, M.D., Ph.D., and colleagues measured gene activity in oligodendrocytes from mice that slept or were forced to stay awake.
“We found that hundreds of transcripts being translated in oligodendrocytes are differentially expressed in sleep and wake,” wrote the investigators. “Genes involved in phospholipid synthesis and myelination or promoting OPC proliferation are transcribed preferentially during sleep, while genes implicated in apoptosis, cellular stress response, and OPC differentiation are enriched in wake.”
“These findings hint at how sleep or lack of sleep might repair or damage the brain,” noted Mehdi Tafti, Ph.D., who studies sleep at the University of Lausanne in Switzerland and was not involved with this study.
Additional analysis revealed that the reproduction of oligodendrocyte precursor cells doubles during sleep, particularly during rapid eye movement, which is associated with dreaming.
“For a long time, sleep researchers focused on how the activity of nerve cells differs when animals are awake versus when they are asleep,” said Dr. Cirelli. “Now it is clear that the way other supporting cells in the nervous system operate also changes significantly depending on whether the animal is asleep or awake.”
Additionally, Dr. Cirelli speculated the findings suggest that extreme and/or chronic sleep loss could possibly aggravate some symptoms of multiple sclerosis (MS). He noted that future experiments may examine whether an association between sleep patterns and severity of MS symptoms exists.