Fig. 1.

Top (A) and side (B) views of a stretch chamber and indenter to illustrate the principle of cell stretching. An I-shaped teflon indenter pushed up against a silicone rubber membrane secured to a square frame results in a principal stretch oriented along the long axis of the indenter. The small tension generated in the orthogonal direction is opposed by the tendency for the membrane to compress orthogonal to the principal stretch direction. The extensions at the corners of the indenter increase the uniformity of the strain field over the indenter, resulting in a virtually uniaxial stretch. Cells were seeded in the central 4 × 4-cm region of the membrane where strain was uniform.