The research, published in the journal Science, demonstrates that brain cells, known as astrocytes, which play fundamental roles in nearly all aspects of brain function, can be adjusted by neurons in response to injury and disease. The discovery, which shows that the brain has a far greater ability to adapt and respond to changes than previously believed.
Astrocytes are star-shaped cells in our brain that surround brain neurons, and neural circuits, protecting them from injury and enabling them to function properly - in essence, one of their main roles is to 'baby-sit' neurons. Our brain contains billions of cells, each of which need to communicate between each other in order to function properly. This communication is highly dependent on the behavior of astrocytes. Until now, the mechanisms that create and maintain differences among astrocytes, and allow them to fulfill specialized roles, has remained poorly understood.
The researchers discovered that there is a little dial-like mechanism on astrocytes that enables neurons to adjust astrocytes to ensure they provide the right kind of support. "This 'dial' is likely used to tune the astrocyte's response in the normal brain but also in different diseases like Alzheimer's or Parkinson's, or injuries such as stroke and trauma, for example,'' explains the study's first author.
Researchers conducted most of their experiments on mouse models and studied a specific pathway called the Sonic Hedgehog (SHH) signaling pathway, which is well known in brain development and cancer. By using a combination of advanced genetics, molecular approaches, and microscopy techniques, they found that this signaling pathway is used in the adult brain in a completely novel way. The SHH pathway was found to induce disparate changes in astrocytes in different brain regions. Hedgehog signaling adjusted distinctive gene expression within the two astrocyte cell types. Thus, mature neurons appear to promote and maintain specific properties of associated astrocytes.
"This is an extraordinary mechanism in the healthy, mature brain that creates diversity of brain cells,'' says the senior author.