When brain cells, neurons, die, their debris need to be quickly and efficiently removed for the surrounding brain tissue to continue to function properly. Elimination of the dead neuron corpses, is accomplished through phagocytosis (Phagocytosis is a specific form of endocytosis by which cells engulf and internalize solid matter). Phagocytosis is carried out by highly specialized cells in the brain called microglia (Microglia are a type of glial cell located throughout the brain and spinal cord. Microglia account for 10–15% of all cells found within the brain. As the resident macrophage cells, they act as the first and main form of active immune defense in the central nervous system). These small cells have many ramifications that are in constant motion and are specially equipped to detect and destroy any foreign element, including dead neurons. Or so it was thought until now.
A new study, published May 26, 2016 in PLOS Biology, investigates, for the first time, the process of neuronal death and microglial phagocytosis in the diseased brain. To this end, scientists collected brain samples from epilepsy patients and from epileptic mice.
It is known that during epilepsy-associated seizures, neurons die. However, contrary to what happens in the healthy brain, during epilepsy, microglia seem to be “blind” and unable to find the dead neurons and to destroy them. Their behavior is abnormal. Therefore, dead neurons cannot be eliminated and accumulate, spreading the damage to neighboring neurons and triggering an inflammatory response that worsens the brain injury.
This discovery opens a new avenue to explore therapies that could alleviate the effects of brain diseases. In fact, the research group that undertook these studies is currently developing drugs, hoping to boost this cleaning process -phagocytosis- and help in the treatment of epilepsy.