Mesoscale substrate curvature overrules nanoscale contact guidance to direct bone marrow stromal cell migration

Abstract

The intrinsic architecture of biological tissues and of implanted biomaterials provides cells with large-scale geometrical cues. To understand how cells are able to sense and respond to complex structural environments, a deeper insight into the cellular response to multi-scale and conflicting geometrical cues is needed. In this study, we subjected human bone marrow stromal cells (hBMSCs) to mesoscale cylindrical surfaces (diameter 250-5000 µm) and nanoscale collagen fibrils (diameter 100-200 nm) that were aligned perpendicular to the cylinder axis. On flat surfaces and at low substrate curvatures (cylinder diameter > 1000 µm), cell alignment and migration were governed by the nanoscale collagen fibrils, consistent with the contact guidance effect. With increasing surface curvature (decreasing cylinder diameter, < 1000 µm), cells increasingly aligned and migrated along the cylinder axis, i.e. the direction of zero curvature. An increase in phosphorylated myosin light chain levels was observed with increasing substrate curvature, suggesting a link between substrate-induced cell bending and the F-actin-myosin machinery. Taken together, this work demonstrates that geometrical cues of up to 10× cell size can play a dominant role in directing hBMSC alignment and migration and that the effect of nanoscale contact guidance can even be overruled by mesoscale curvature guidance.

Cell‐Perceived Substrate Curvature Dynamically Coordinates the Direction, Speed, and Persistence of Stromal Cell Migration

“…In contrast, cell migration on convex cylindrical surfaces was persistently directed along the longitudinal axis of the cylinder (Figure b). To quantify this anisotropic migration, we calculated an anisotropy index d x /d y : the ratio of migration distance in the longitudinal ( x ) and circumferential ( y ) directions of the cylinders . Consistent with our qualitative observations, on convex surfaces d x /d y exceeds 1 on all cylinder sizes, indicating an anisotropic migration towards the longitudinal cylinder axis.…”

“…This effect becomes increasingly pronounced with decreasing cylinder sizes (or increasing κ). This positive‐curvature‐mediated cell alignment can be explained by the cells' aversion to bending . It was proposed before in a mechanical model that cells with mature stress fibers orient themselves in a direction of least curvature to avoid bending of stress fibers .…”

“…In the case of convex cylindrical structures, fibroblasts and smooth muscle cells have been shown to orient toward the longitudinal axis of the cylinders, that is, the direction of minimal curvature . Our recent work demonstrated that this guidance effect by convex mesoscale cylindrical structures can even overrule co‐existing nanoscale contact guidance cues . While these early findings start to uncover the importance of considering anisotropic substrate curvatures, how they translate to cell migration behavior on concave anisotropic structures or even more complex geometries encountered in tissues and biomaterial scaffolds remains unknown.…”

Laser‐Assisted Strain Engineering of Thin Elastomer Films to Form Variable Wavy Substrates for Cell Culture

“…Recently, bigger concave or convex structures have also shown to guide cell orientation and migration . However, the use of these curved substrates is still rare in biological studies.…”

“…However, the use of these curved substrates is still rare in biological studies. The flexibility of these methods is limited to the fabrication of a mold and abrupt angles are often present at the edges of the structures …”