Quantification of a Thermal Damage Threshold for Astrocytes Using Infrared Laser Generated Heat Gradients

The response of cells and tissues to elevated temperatures is highly important in several research areas, especially in the area of infrared neural stimulation. So far, only the heat response of neurons has been considered. In this study, primary rat astrocytes were exposed to infrared laser pulses of various pulse lengths and the resulting cell morphology changes and cell migration was studied using light microscopy. By using a finite element model of the experimental setup the temperature distribution was simulated and the temperatures and times to induce morphological changes and migration were extracted. These threshold temperatures were used in the commonly used first-order reaction model according to Arrhenius to extract the kinetic parameters, i.e., the activation energy, Ea, and the frequency factor, Ac, for the system. A damage signal ratio threshold was defined and calculated to be 6% for the astrocytes to change morphology and start migrating.