Two-dimensional orientational response of smooth muscle cells to cyclic stretching

It was hypothesized that an orientated cellular tissue for incorporation into vital, functioning hybrid artificial organs can be prepared by periodically applying mechanical stresses on a hybrid tissue. Therefore, the effect of cyclic stretching on the two-dimensional (2-D) orientation response of arterial smooth muscle cells (SMCs) was studied. Smooth muscle cells derived from bovine aortas were seeded onto transparent elastomeric membranes made of polyurethane, and subjected to periodical stretching with various amplitudes from 5-20% at frequencies of 15 to 120 RPM for up to 24 hours. Phase-contrast microscopic views of SMCs were time-lapse video recorded. The orientation angle to the direction of stretching (OA) and cellular longitudinal length (CLL) of individual cells were analyzed by a computerized image processor. After several hours, SMCs subjected to the stress exhibited orientation responses perpendicular to the direction of stretching, evidenced by a significant increase in OA. The responses were more rapid under operating conditions with higher amplitudes and frequencies of stretching. Meanwhile, little significant change in CLL was observed. These findings indicate that an applied mechanical stress induces a significant orientation response, without morphologic alteration of SMCs. The mechanically induced orientation response provides a fundamental basis for more structured hybrid organs and tissue engineering.