Shear Measurements of Cerebrospinal Fluid Flow in Mice*

Amyloid beta 42 is found in plaques in the brains of Alzheimer’s disease patients and is believed to be a factor in damaging and killing neurons. The process of accumulation of amyloid beta 42 leading to the formation of plaques is not well understood. One mechanism that has been correlated with amyloid protein aggregation is molecular distortion due to shear in fluid flow [Trumbore, Journal of Alzheimer’s Disease 59, 543-557 (2017)]. After acquiring images using two-photon microscopy, we performed particle tracking velocimetry to obtain quantitative measurements of cerebrospinal fluid flowing within spaces around arteries in the brains of living mice. We determined the velocity and shear rate in the cerebrospinal fluid with high resolution by applying phase averaging over the cardiac cycle. Our measurement of shear rate offers a potential mechanism by which fibril formation rises leading to an increased risk for Alzheimer’s disease.