Sep 04, 2013 11:06 AM EDT By Russell Westerholm, UniversityHerald Reporter

Sleep is a chance in everyone's day to recharge the body, but new research says it is also responsible for rebuilding brain cells, according to a press release.

The new animal study, published Wednesday in the Journal of Neuroscience, found that during sleep, cells reproduce and go on to form insulating material known as myelin. The cells pad the nerve projections in the brain and spinal cord, the researchers said, and the work could lead to a better understanding of how sleep affects brain repair and growth.

Myelin is a necessity to a healthy brain and scientists previously did not know exactly how sleep affected its production. Certain genes are turned on during sleep and off while awake, but scientists had not been able to make the connection.

Like the insulation in an electrical wire, myelin is vital to encourage the flow of impulses from one cell to the next.

"For a long time, sleep researchers focused on how the activity of nerve cells differs when animals are awake versus when they are asleep," Chiara Cirelli, MD and PhD, at the University of Wisconsin (UW)-Madison, said. "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."

Cirelli and her colleagues found that genes promoting the production of myelin were turned on when the test mice went to sleep. When the animal was forced to stay awake, those genes remained off and promoted cell death.

"These findings hint at how sleep or lack of sleep might repair or damage the brain," said Mehdi Tafti, PhD, who studies sleep at the University of Lausanne in Switzerland and was not involved with this study.

Oligodendrocyte precursor cells (OPCs) were found to produce oligodendrocytes, which are the genes that produce myelin. On further analysis, the researchers found OPCs doubled during rapid eye movement (REM) sleep, or the deep, healthy and restful kind of sleep.

Further research is needed, but Cirelli speculated that chronic sleep loss and lack of sleep can contribute to diseases like multiple sclerosis (MS), which damages myelin. Future experiments will analyze that connection.

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