抄録
Cell traction force (CTF) is important in many aspects of cellular activities such as migration, tensional homeostasis, and shape change. Traction force microscopy (TFM) has been used widely to measure CTF. However, this method is not sutable for the cells on stiff substrates, i.e., those with physiological stiffness. Towards estimation of CTF of cells on stiff substrate, we investigated the relationship between CTF and retardance, phase shift of polarized light when it passes through birefringent material, because birefringence may change with internal stress. Vascular smooth muscle cells were cultured on a glass bottom dish and treated with calyculin A and Y-27632 to increase and decrease, respectively, CTF. Cell retardance was measured with a birefringence imaging system, pol-scope, and normalized by the retardance at 0 min. Retardance increased and decreased significantly in cells treated with calyculin A and Y-27632, respectively, compared to control cells 50 min after administration of the reagents. When measurement of cell retardance and TFM were performed simultaneously on a single cell cultured on a polyacrylamide gel substrate with elastic modulus of 15 kPa, retardance correlated significantly with CTF. These results may indicate that retardance can be used to estimate CTF of cells cultured on substrates with physiological stiffness.
