Abstract: One of the principle ways that cells interact with their environment is by exerting mechanical forces. In order to understand the generation and application of forces by cells, the location, direction and magnitude of forces applied to a surface must be known and these related to dynamic cellular structures. Light microscopy is the method of choice for simultaneous measurements of these quantities, and therefore the surface must have suitable optical properties. These challenges have been approached by imaging cellular and cytoskeletal dynamics in living cells along with strain produced by traction forces in transparent silicone rubber substrata. The silicone has an index of refraction very similar to glass, facilitating many types of optical microscopy. Fluorescence microscopy was used to study cytoskeletal dynamics in fibroblasts by microinjecting a fluorescent analog of the motor protein myosin II. Cell- substratum contacts were studied by interference contrast microscopy (IRM), and cell morphology was monitored by Nomarski Differential Interference Contrast (DIC). Changes in traction force at cell-substratum contacts correlated strongly with assembly of myosin into the cytoskeleton. An important optical property of the silicone rubber used here allows its mechanical properties to be matched to the cells under study: illumination by UV light increases compliance, permitting measurement of forces in the range of nanonewtons to micronewtons during cell locomotion, contraction, and division. !15
展开▼
