Microcurvature landscapes induce neural stem cell polarity and enhance neural differentiation

Tissue curvature has long been recognized as an important anatomical parameter that affects intracellular behaviors, and there is emerging interest in applying cell-scale curvature as a designer property to drive cell fates for tissue engineering purposes. Although neural cells are known to undergo dramatic and terminal morphological changes during development and curvature-limiting behaviors have been demonstrated in neurite outgrowth studies, there are still crucial gaps in understanding neural cell behaviors, particularly in the context of a three-dimensional (3D) curvature landscape similar to an actual tissue engineering scaffold. In this study, we fabricated two substrates of microcurvature (curvature-substrates) that present a smooth and repeating landscape with focuses of either a concave or a convex pattern. Using these curvature-substrates, we studied the properties of morphological differentiation in N2a neuroblastoma cells. In contrast to other studies where two-dimensional (2D) curvature was demonstrated to limit neurite outgrowth, we found that both the concave and convex substrates acted as continuous and uniform mechanical protrusions that significantly enhanced neural polarity and differentiation with few morphological changes in the main cell body. This enhanced differentiation was manifested in various properties, including increased neurite length, increased nuclear displacement, and upregulation of various neural markers. By demonstrating how the micron-scale curvature landscape induces neuronal polarity, we provide further insights into the design of biomaterials utilizing the influence of surface curvature in neural tissue engineering. Graphic abstract: [Figure not available: see fulltext.]