Printing channels with millimeter-scale curvature and deciphering their effect on the proliferation, morphology, orientation, and migration of M-22 cells.

Complex curved structures of tissues have been recognized to influence the behavior and function of cells. Tissue curvatures sensed by cells are approximately on the millimeter scale. However, previous research mainly focused on the effect of micro- and nano-scale spatial curved structures, underestimating the significance of milli-scale curvature. Here, we employed fused deposition modeling (FDM) with two-stage temperature control, superfine cone-shaped needle, stable air pressure, and precise motion platform for the customized production of homogeneous, precise, and curved fibers; the responses of M-22 cells to FDM-printed curved channels with radii of 1.5 to 3 mm were systematically investigated. The cells aligned with these curved channels and exhibited various aspect ratios in the channels with different curvatures. Cell proliferation, migration speed of single cells, and front-end speed of collective cells were tightly regulated by these curved structures. Also, a computational model based on force equilibrium was proposed to explore the essential factors and mechanisms of curvature affecting cell behavior. Our simulation results demonstrated that the curvature and width of channels, along with the relative size of cells, can significantly impact the cell-boundary interaction force and the number of valid pseudopodia generated by cells in the process of cell migration. These results provide a comprehensive understanding of the effect of milli-scale curvature on the cells and underpin the design of scaffolds that can be produced easily with sophisticated micro- and nano-scale curved features to regulate cell behavior in tissue engineering.