Neuroscience is full of neurons- like the ‘007’ movie series full of James Bond. We saw Mr.Bond doing all superhero adventures to keep the world in control. However Mr.Bond couldn’t be successful without his ever protective, sophisticated and adaptive tools that help him escape from powerful villains. Is there someone out there to support neurons in complex situations? Well there are many to call for.
Microglia, oligodendrocytes and astrocytes are the supporting partners for CNS neurons while Schwann cells and macrophages support PNS neurons. In general microglia and macrophages protect neurons from villains such as bacteria and viruses through immune surveillance whereas astrocytes offer structural and trophic support. The oligodendrocytes and Schwann cells in turn are generally recognized for facilitating myelination and conduction velocity in neurons. However, the listing of jobs are not strictly specific to one type of cells and there are multiple, and overlapping, functions exist, for example both microglia and astrocytes do synapse pruning, both macrophages and Schwann cells clear neuronal milieu, and both Schwann cells and astrocytes feed neurons. Raising the bar of complexity further, some of these cell types express same molecular markers rendering their studies in isolation difficult in vivo, and more interestingly same cells act or appear differently depending on the context, kind of resembling the unpredictable attitude of Mr.Bond!!!
Needless to say, a large space of the poster session at the SFN over the last three days was occupied by these cells claiming their supporting roles. Choosing the winner for the best performance was absolutely impossible. One of the works that raised my curiosity discussed about dark microglia. Have you ever heard of them? These are phagocytically more active microglia that appears during stress and disease conditions such as Alzheimer’s disease. It has a characterized dark cytoplasm, for which they were named after, and project their ramifications around axons as if to facilitate pruning of synapses. It is particularly interesting that the authors observed dark microglia in postnatal day 5 brains implicating a major role for them during development. Another group studied the effect of replacing brain microglia with peripheral macrophages which threw some lights on macrophage plasticity in the CNS. Many more works on microglia will be presented tomorrow at 1-5pm. Type ‘Microglia in Disease’ in the neuroscience app…………………. you got it!!!