Abstract
DAI is caused by sudden inertial loading to the head associated with rapid deformation of brain tissue, resulting in the stretching of neural axons. Periodic swellings along axons and axonal bulbs at disconnected terminal ends of axons that are the morphological hallmarks of DAI pathology lead to the disconnection of neuronal cells from tissues, resulting in cell death. The β-amyloid precursor protein (β-APP) that is conveyed by axonal transport accumulates where axonal transport is disrupted. The cultured rat brain neuronal cells were stretched to a strain of 0.10, 0.15, 0.22, or 0.30 at a strain rate of 11, 21, 27, or 38 /s. The sham control is put in the stretching device without mechanical loading and then is incubated under conditions of 5% CO2 and 100% humidity at 37℃. β-APP was stained at 3h post-loading and observed using fluorescence microscopy. As a result, β-APP accumulated in swellings and bulbs following stretching and β-APP-accumulated axons significantly increased following a strain of 0.22 with a strain rate of 27 /s and a strain of 0.30 with a strain rate of 38 /s in a stretch-dependent manner compared to sham control. These results suggest that the threshold of interruption of axonal transport is strains of 15-22% at strain rates of 21-27/s and the accumulation of β-APP is a quantitative marker for traumatic axonal injury at a cellular level.
