Contact guidance of mesenchymal stem cells by flagellin-modified substrates: Aspects of cell-surface interaction from the point of view of liquid crystal theory

A major challenge for the tissue engineering is the regulation of cell behavior using topographical cues of the artificial biomaterials without biochemical stimuli. In this study, micropatterned substrates with ridge/groove topography (pitch size of 6–80 µm) and upper adhesive layer from non-animal origin RGD peptide flagellin were created on the basis of polydimethylsiloxane (PDMS). The obtained flagellin(FL)-modified PDMS microstructures revealed both physicochemical and biological anisotropic properties. Mesenchymal stem cells (MSCs) sensed and reshaped in response to the ridge/groove patterned surface similar to water microdroplets behavior. Cultivation of MSCs on the micropatterned FL-PDMS substrates led to cell polarization in a direction parallel to the pattern and the degree of MSCs orientation increased with the enhance in the pitch size from 8 to 20 µm, and then decreased. The MSCs orientation on micropatterned FL-PDMS substrates was explained from the point of view of nematic liquid crystal theories assuming that stem cells can be considered as active nematic phase and their orientation order can be evaluated by P2 parameter. In accordance with the theory, an enhanced orientation effect of the surface profile can be reached by providing a strong polar interaction between the cells and the patterned surface of the substrate. Surface modification by FL layer increased the polar interaction between the MSCs and the surface resulting in stimulation of the isotropic-to-nematic transition. In summary, our data make a significant contribution to understanding the fundamentals of the influence of substrate topographical features on MSCs topology and can be useful for the rational design of scaffolds intended to manipulate cell behavior without exogenous stimuli.