Sleep Produces Cells that Grow and Repair Nerve Cell Insulation
Madison, Wisconsin - In a surprising finding, University of Wisconsin-Madison sleep researchers have found that the sleeping brain produces cells that repair and grow myelin – the “insulation” around nerve cells that is damaged in diseases such as multiple sclerosis.
A team led by Dr. Chiara Cirelli, of the UW School of Medicine and Public Health, looked at the brains of mice and found that the expression of several genes involved in making cells that create and repair the myelin sheath around nerve cells are turned on during sleep. Conversely, genes implicated in the death of those cells are preferentially produced during wakeful periods.
“It is an intriguing finding, so much so that we almost didn’t believe it at first,” says Cirelli, professor of psychiatry. “It’s very puzzling because myelin is known to grow very slowly and myelin cells typically turn over during a period of weeks and months.”
Cirelli says the idea for the study is nearly a decade old: In 2004, she and collaborator Dr. Giulio Tononi did a screen of genes and found hundreds of them were preferentially up-regulated during sleep, and down-regulated during wake. But back then, they lacked the technology to sort out which genes were regulated in different types of brain tissue. Now, thanks to transgenic mice and an analysis method called translating ribosome affinity purification (TRAP) they were able to look specifically at the genes in glial cells that make precursors to myelin cells.
They found that during sleep, hundreds of transcripts that govern the synthesis of cells called oligodendrocyte precursor cells (OPCs) are up-regulated during sleep, while genes involved in cell death, cell stress response and cell differentiation are up-regulated during wake. An assay of living cells confirmed that OPC proliferation doubles during sleep, especially during rapid eye movement phase (
Cirelli says the research could provide a mechanism for poor sleep being associated with the destruction of myelin cells, and healthy sleep being associated with growth and repair. It also suggests some further research that could lead to ways to promote myelin repair.
“It’s basic research, so we shouldn’t read too much into it,” she cautions, “but it is quite a surprising finding.”
Cirelli’s co-authors include: Michele Bellesi, Martha Pfister-Genskow, and Giulio Tononi, of the UW Department of Psychiatry; Sunduz Keles, of the UW Department of Biostatistics and Medical Informatics and Stephanie Maret of the University of Geneva, Switzerland. The article is being published in the Journal of Neuroscience. The study was supported by a grant from the UW Department of Psychiatry.
Date Published: 09/03/2013