(789a) Control of Durotaxis Through Patterned Rigidity

We have developed an innovative platform to facilitate the study of adherent cell migration in response to rigidity gradients or durotaxis. Specially formulated polyacrylamide hydrogel with tunable stiffness was casted on rigid patterned supports to fabricate a flat compliant gel layer with variable thickness. The resulting gel’s apparent stiffness increased with decreasing gel thickness, as validated by indentation measurements. By careful manipulation of the thickness of the gel substrate through the embedded features, the results showed a statistically significant difference in fibroblast durotaxis. Fibroblasts, which were known to migrate toward stiffer substrates, were found to accumulate in regions where the gel thickness was less than 15 µm. In addition, when the bulk gel elastic shear modulus was tuned from 3 to 30 kPa, the stiffness range of tissues in contact with fibroblasts in vivo, this critical thickness remained constant. This system was capable of directing collective cell patterning for concentrations of up to 15x10⁵ cells / ml of culture medium. This finding suggests that even in the presence of multiple cell to cell interactions, the elasticity gradient provided by underlying topographical patterns is sufficient to induce durotaxis. As expected, no durotaxis was observed when cells were pretreated with drugs known to interfere with the cytoskeletal network, or when we genetically interfered with cell adhesion.

One significant achievement of this novel procedure is that the rigidity-patterned surface requires neither advanced photolithography techniques nor access to clean room facilities. Moreover, the inert gel surface is isotropic, independent of cell types, and supports long-term cell viability. This enables the study of cell migratory behavior in conventional biology laboratories and can contribute to the development of next-generation scaffolds suitable for tissue engineering applications.