Summary Microglial research has advanced considerably in recent decades yet has been constrained by a rolling series of dichotomies such as “resting versus activated” and “M1 versus M2.” This dualistic classification of good or bad microglia is inconsistent with the wide repertoire of microglial states and functions in development, plasticity, aging, and diseases that were elucidated in recent years. New designations continuously arising in an attempt to describe the different microglial states, notably defined using transcriptomics and proteomics, may easily lead to a misleading, although unintentional, coupling of categories and functions. To address these issues, we assembled a group of multidisciplinary experts to discuss our current understanding of microglial states as a dynamic concept and the importance of addressing microglial function. Here, we provide a conceptual framework and recommendations on the use of microglial nomenclature for researchers, reviewers, and editors, which will serve as the foundations for a future white paper. https://www.cell.com/neuron/fulltext/S0896-6273(22)00953-9?_returnURL=https://linkinghub.elsevier.com/retrieve/pii/S0896627322009539?showall=true
Very deep and interesting read. Summary of what I read so far: Microglia aren't either resting or activated as many assume. They're constantly active, but play different roles at different times. They are highly receptive to their chemical environment, so subtle signals can change their behavior a lot Activation isn't necessarily bad. With certain brain conditions, microglia could play an active role in "cleaning up." Microglia do a lot: They're involved in synapse remodeling (rearranging connections between neurons, crucial for learning), neuronal function, tissue repair, blood-brain barrier permeability, vasculogenesis (making new blood vessels), inflammation, myelination (creating the protective coating of myelin), and neurogenesis (See figure 2) They listen to signals from the rest of the body. Sickness behavior (the fatigue that comes with an infection to encourage rest) involves microglia but we're not sure how. They explain how scientists should describe microglia in research. They shouldn't refer to microglia as "resting" because they're always doing something, and they shouldn't describe them as simply "activated" because there are many ways in which they can be activated, or how this is measured.
