Probing cellular response to topography in three dimensions

Abstract

Biophysical aspects of in vivo tissue microenvironments include microscale mechanical properties, fibrillar alignment, and architecture or topography of the extracellular matrix (ECM). These aspects act in concert with chemical signals from a myriad of diverse ECM proteins to provide cues that drive cellular responses. Here, we used a bottom-up approach to build fibrillar architecture into 3D amorphous hydrogels using magnetic-field driven assembly of paramagnetic colloidal particles functionalized with three types of human ECM proteins found in vivo. We investigated if cells cultured in matrices comprised of fibrils of the same size and arranged in similar geometries will show similar behavior for each of the ECM proteins tested. We were able to resolve spatial heterogeneities in microscale mechanical properties near aligned fibers that were not observed in bulk tissue mechanics. We then used this platform to examine factors contributing to cell alignment in response to topographical cues in 3D laminin-rich matrices. Multiple human cell lines extended protrusions preferentially in directions parallel or perpendicular to aligned fibers independently of the ECM coating. Focal adhesion proteins, as measured by paxillin localization, were mainly diffuse in the cytoplasm, with few puncta localized at the protrusions. Integrin β1 and fascin regulated protrusion extension but not protrusion alignment. Myosin II inhibition did not reduce observed protrusion length. Instead, cells with reduced myosin II activity generated protrusions in random orientations when cultured in hydrogels with aligned fibers. Similarly, myosin II dependence was observed in vivo, where cells no longer aligned along the abluminal surfaces of blood vessels upon treatment with blebbistatin. These data suggest that myosin II can regulate sensing of topography in 3D engineered matrices for both normal and transformed cells.

Cell-Based Strain Remodeling of a Nonfibrous Matrix as an Organizing Principle for Vasculogenesis

“…The presence of laminin seems to play a further crucial role, as functionally blocking antibodies against integrins that bind mainly to laminin inhibit tube formation, while blocking other integrins has no significant effect. Although laminin gels are amorphous per se, the formation of cell-sized fibrous structures can be induced by mechanical forces, such as the external application of fluid flow (Jang et al, 2015) or the exertion of a force via paramagnetic particles in a magnetic field (Paul et al, 2019). Here, we observed that Matrigel was rearranged into fibers by exposure to cells.…”

Bioactive potential of natural biomaterials: identification, retention and assessment of biological properties

“…We characterise the significant biological motifs, structure, and complex architectures of common starting materials that dictate cell behaviour and tissue responses differentiating from disease phenotypes. 18 Cells are sensitive to organisational motifs discussed above, such as fibril status, 19 molecule length, and molecular weight 20 as these may indicate tissue degradation and induce an inflammatory response. Finally, this review aims to highlight the importance of target tissue and substrate material characterisation, starting material selection and processing based on innate biologically active motifs, with final validation of retained biological motifs in the final product to regenerate the target tissue.…”

The effects of surface topography modification on hydrogel properties

“…Hydrogels with aligned microfibers and nanofibers were well documented to induce cell alignment along the fibers. 157–159 Alginate hydrogels made by wet spinning were exposed to shear force to reshape the hydrogel fiber into aligned sub-micrometer topography. 95 Cells were shown to orient along with fiber axis and formed cell-matrix dual alignment.…”