(149e) Mesenchymal Stem Cell Alignment On the Pre-Stretched Surface

Mechanical cues in the cellular environment play important roles in guiding various cell behaviors, such as cell alignment, migration, proliferation, and differentiation. Numerous studies have shown that mechanical cyclic stretch can induce cells to align perpendicular to the stretch direction, while relatively fewer studies focus on static stretch. However, almost all of the previous studies of static stretch were post-stretch, which means the cells were first seeded to allow attachment and then the substrate subsequently stretched. In contrast, we create a static pre-stretched anisotropic surface in which the cells are seeded after the substrate is stretched. The results show that cells align in the direction of pre-stretch, which is induced by the anisotropy that can be predicted by the theory of finite elasticity.

The experimental results agreed with a "Cell mechano-active sensing" model, which suggests that the cells can sense and respond to surface anisotropy by orienting in the direction of maximal effective stiffness. In this study we employed a theory of "small deformation superimposed on large" to predict the anisotropy induced by the uniaxial pre-stretch. After a 10% uniaxial pre-stretch, the effective stiffness that the cells sense in the stretched direction is 1.33 times of that in the perpendicular direction. Next, we explored the impact of pre-stretch magnitude on cell orientation angle distribution. Cells (mesenchymal stem cells or primary neurons) seeded on poly-L-lysine coated PDMS membrane surfaces with 10%, 20%, or 30% pre-stretch were quantified after 4 days of culture for their cell orientation angles. The results showed that the ratio of cells that orient parallel (within ±10°) increased with the magnitude of the stretch.

In summary, we demonstrated that cells aligned on static pre-stretched anisotropic surface, and the number of cells that aligned in parallel orientation increased with the pre-stretch magnitude. Besides alignment of MSCs, we investigated the impact of pre-stretched surface on axonal growth and orientation. The results showed that axonal alignment also increased with the pre-stretch magnitude and a larger pre-stretch can promote thicker and longer axonal growth.