Microglia Mechanobiology under the Impact of Intrinsic and Extrinsic Forces During Neurodegenerative Diseases and Traumatic Brain Injuries
Abstract:
Microglia are known for providing immune responses as residential macrophages of the Central Nervous System. However, they tend to become pro-inflammatory in the brain under the mechanical forces expressed by brain tissues during neurodegenerative diseases. These mechanical forces can be divided into intrinsic and extrinsic categories depending on whether they impact the organism from within or outside. Both types of forces transform the mechanical properties of the substrate. Intrinsic forces have a long-lasting impact on microglia, lasting for months or even years, as seen in Alzheimer's or Parkinson's diseases. These forces are connected directly to the mechanical characteristics of the substrate, such as the stiffness of Aβ proteins or α-synuclein proteins. On the other hand, extrinsic forces are short-term, lasting only a few minutes, and come from outside the organism, such as in traumatic brain injuries. These forces induce shear stress and strain and change the substrate's stiffness. This review delves into the difference between the microglia mRNA gene profile under intrinsic vs. extrinsic forces. The mechanism of direct and non-direct impact of the substrate stiffness on microglia morphology and inflammatory gene profile in Alzheimer's and Parkinson's diseases, during microelectrodes implantation, and in the case of traumatic brain injuries are analyzed.
