The response of neural-like cells to mechanical stimuli and hypoxia

Traumatic brain injury (TBI) is a major cause of mortality in the United States. Despite this, the response of the neuron to the mechanical deformations produced in TBI has not been determined quantifiably. A device is presented here that introduces a dynamic deformation to a culture of differentiated NG108-15 neuroblastoma cross glioma hybrid cells while simultaneously altering the chemical environment of the cell. This device was employed to determine the response of these cells to strains ranging from 0.07 to 0.45 at a strain rate of either 0.1 or 10 s$\sp{-1}$. The increase in intracellular free calcium concentration, as determined using the intracellular fluorescent calcium indicator dye, Fura-2, was employed as an index of the neural response. The cells were shown to respond in a strain-dependent fashion at strain rates of 10 s$\sp{-1}$. Furthermore, the pre-application of chemical hypoxia (2-deoxyglucose and salicylate) did not alter this response within two minutes of the mechanical insult. To provide insight into this behavior, a numerical model of the short term intracellular calcium homeostasis was developed and compared to the actual cellular data. The model illustrated that a strain-dependent increase in plasma membrane permeability is sufficient to account for the observed in vitro increase in intracellular free calcium concentration and that this increase is dependent on the degree of metabolic compromise. This work implies that, in TBI, moderate hypoxia does not significantly effect the short term neural response to trauma. In addition, the neural response increases as an exponential function of the magnitude of the applied strain at high strain rates. In summary, the system developed here provides a novel method to apply a known mechanical deformation and chemical environment to cultured neural-like cells