Researchers from the University of Colorado School of Medicine have found that immune cells known as microglia may play a key role in how the brain forms connections between neurons.
For the study, the researchers observed the development of the central nervous system in larval zebrafish. This is because these fish share many aspects of nervous system development with humans. Moreover, they are transparent, meaning that the cells in their nervous system are easy to watch as they develop.
In watching the fish, the researchers found that microglia, immune cells in the brain that protect against infection, also appear to regulate myelination- the formation of a fatty sheath around neural fibers to increase their speed of transmission. Microglia seem to do so by examining and then removing some of these fatty sheaths in a process called 'phagocytosis'- or cellular 'eating'.
The researchers further noted that the amount of myelin consumed by the microglia seemed to depend on the amount of neuronal activity between the underlying neurons. Thus, they suspect that the microglia may be able to interact with neurons to decide whether or not to remove their myelin sheaths.
As abnormalities in myelination are characteristic of numerous neurological and neuropsychiatric diseases from Alzheimer's to schizophrenia and autism, understanding how myelination works is extremely important for both understanding and developing therapeutics to combat these diseases.
As such, the researchers believe that their findings will lead to an improved understanding of some neurological and neuropsychiatric diseases' potential causes.
"Learning how microglia, oligodendrocytes, and neurons work together to build a functional nervous system could ultimately help our understanding of how these cells interact in diseases of development or aging and may influence strategies for myelin repair," says Alexandria N. Hughes, first author of the study and a graduate student in the University of Colorado's Graduate School Neuroscience Program.