A stress-related signal may help the brain repair itself after injury. Researchers found that myelin-producing precursor cells rapidly release the stress hormone corticotropin-releasing hormone (CRH) near damaged brain tissue. This hormone helps control how those cells mature and rebuild protective nerve insulation. The same system also influences brain development and the thickness of myelin later in life.
Oligodendrocyte progenitor cells (OPCs) are precursor cells that mature into oligodendrocytes. Oligodendrocytes produce myelin, which insulates nerve fibers (axons). Myelin is crucial for efficient information transmission in the brain. Damage to myelin can lead to severe neurological issues, as seen in conditions like multiple sclerosis.
In a study using laboratory mice, researchers observed that OPCs multiply significantly around brain wounds. A portion of these OPCs activate CRH. This CRH response begins within hours of an injury and subsides after about three days. This rapid, short-term release suggests CRH plays an important role in the initial stages of healing.
CRH receptor 1, found on other OPCs, allows these cells to respond to the released CRH. When CRH receptor 1 is absent, OPCs multiply faster after an injury. However, this does not lead to better repair. Fewer mature oligodendrocytes are produced in the long term. This indicates CRH helps regulate the timing of OPC maturation, which is essential for effective myelin restoration.
The CRH system also impacts normal brain development. CRH receptor 1 is present on OPCs even without injury. Mice lacking CRH receptor 1 produced more OPCs during early development. These changes resulted in thicker myelin sheaths in adult brains, particularly around thin axons. This suggests CRH receptor 1 on OPCs is important for both injury repair and myelin development.
Neurons are known to release CRH, especially under stress. Stress during early childhood is a risk factor for psychiatric disorders. The findings suggest the CRH system in OPCs may contribute to stress-associated psychiatric disorders like depression. Understanding CRH signaling's role in OPCs and myelin formation could lead to new therapeutic approaches.
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