Relation between cell membrane tension and repair of membrane damaged during sonoporation

We have been studying a sonoporation technique and have reported that one-shot exposure of short-pulsed ultrasound can elicit a sonoporation effect in the presence of a microbubble attached to a cell. It is generally thought that sonoporation causes more severe damage to cells cultured on a rigid scaffold than to cells suspended in a medium or to cells of in vivo tissue. One possible explanation is that a higher damage rate is caused by higher membrane tension. Since the ability of cells to rescue themselves from membrane damage is strongly dependent on their membrane tension, cells cultured on a rigid scaffold, which have higher membrane tension, may have more severe sonoporation damage. In this study, cell membrane tension was controlled by changing osmolality of the culture medium and selecting shapes of cells cultured on a coverslip, and the effect of membrane tension on ability for membrane repair was investigated by fluorescence microscopic observation that visualizes severity of sonoporation-induced cell damage. Repair rates of cells treated under isotonic and hypertonic conditions of osmolality were 55±8%and 75±14% (means ± S.D.), respectively, indicating that lower membrane tension causes higher repair rate. The repair ability was also studied using cells with different shapes. The results showed that spherical-shaped cells, which have lower membrane tension, have a minimum lethal damage level five-times higher than that of spindle-shaped cells, also suggesting that lower membrane tension can increase the ability of cells to repair sonoporation-induced membrane damage.