Mechanical stiffening and delayed cell death of endothelial cells exposed to impulsive pressure.

Head impact induces rapid fluctuations in intracranial pressure, which are implicated in vascular damage even in the absence of skull fracture. Endothelial cells lining the inner lumen of blood vessels sense mechanical stimuli and transduce them into biological responses. We hypothesized that impact-induced pressure fluctuations alter endothelial cell mechanics and contribute to delayed endothelial injury. In this study, impulsive pressures with amplitudes and frequencies comparable to those generated during head impact were applied to cultured endothelial cells. Cellular stiffness was evaluated by measuring Young's modulus using atomic force microscopy, while mitochondrial membrane potential, caspase-3/7 activation, and cell viability were assessed using fluorescence imaging. Endothelial cells exposed to impulsive pressure showed a significant increase in stiffness after 1 h of loading, followed by mitochondrial membrane potential disruption after 3 h, caspase-3/7 activation after 6 h, and delayed cell death after 24 h. These findings suggest that rapid pressure fluctuations associated with head impact may induce time-dependent mechanobiological responses in endothelial cells, thereby contributing to microvascular damage following traumatic brain injury.