Modeling Heat Shock Protein Expression Produced by a Heat Wrap

The healing effect of therapeutic hyperthermia induced by widely available heat wrap products is understood to be based on concomitant temperature dependent vasodilation and increase in mass transport. We hypothesize that an additional mechanism of healing associated with increased heat shock protein (HSP) expression is also a contributing factor. HSP expression is controlled by the level and duration of heating and can have a potent effect on healing. We have developed a combined thermal stress and HSP expression model for bioheat transport into the tissues of the back produced by a therapeutic heat wrap. The model predicts temperature distribution in the deep tissues of the back by a modified version of the Pennes (1948, “Analysis of Tissue and Arterial Blood Temperatures in the Resting Human Forearm,” J. Appl. Physiol., 1(2), pp. 93–122) bioheat equation. The model also predicts HSP70/actin concentrations based on existing empirical expression data from our laboratory as a function of heating time and temperature. Thermal boundary conditions were input for a typical heat wrap worn for its functional duration of 8 h or more. Temperatures in the paraspinal muscles of the back increase by a minimum of $1°C$ after 1 h of heating and persist for at least 2 h. HSP70/actin expression is increased 1.7-fold above the control. The model demonstrates that elevated HSP expression may provide an important contribution to the healing process in injured tissue when a therapeutic heat wrap is worn.