Development and evaluation of microdevices for studying anisotropic biaxial cyclic stretch on cells

Mechanical effects on cells have received more and more attention in the studies of tissue engineering, cellular pathogenesis, and biomedical device design. Anisotropic biaxial cyclic stress, reminiscent of the in vivo cellular mechanical environment, may promise significant implications for biotechnology and human health. We have designed, fabricated and characterized a microdevice that imparts a variety of anisotropic biaxial cyclic strain gradients upon cells. The device is composed of an elastic membrane with microgroove patterns designed to associate cell orientation axes with biaxial strain vectors on the membrane and a Flexcell stretcher with timely controlled vacuum pressure. The stretcher generates strain profile of anisotropic biaxial microgradients on the membrane. Cell axes determined by the microgrooves are associated with the membrane strain profile to impose proper biaxial strains on cells. Using vascular smooth muscle cells as a cell model, we demonstrated that the strain anisotropy index of a cell was likely one of the determinant mechanical factors in cell structural and functional adaptations. The nuclear shape and cytoskeleton structure of smooth muscle cells were influenced by mechanical loading, but were not significantly affected by the strain anisotropy. However, cell proliferation has profound responses to strain anisotropy.