Page 53 - IJB-9-3

International Journal of Bioprinting Curved cell-guided structures printed by FDM

than the other groups (P < 0.01), while the migration investigated the process of cell migration in the experiment.
speed of R3 was significantly faster than SL (P < 0.05). The Cells polarize and form tentative pseudopodia at the front
average single-cell migration speed was the average ratio to create adhesion points during migration . When a cell
[39]
of the cell migration distance (Li) to the observation time encounters a boundary that cannot cross, it will retract
(t) (Figure 4D). The average single-cell migration speed the original pseudopodia and form a new one in the other
first increased and then decreased with the increasing direction to change the migration direction due to the
channel radii, reaching the maximum in R2, albeit only force between the cell and the channel wall. Therefore, we
having a significant difference with straight channels (P inferred that the curvature mainly influenced the force
< 0.05) (Figure 4E). Notably, the trends of the front-end of cell–boundary interaction and the number of invalid
speed of collective cells and single-cell migration speed pseudopodia (need to retract and form a new one) to
with curvature were consistent, and the front-end speed regulate the cell behavior (Figure 5C). The forces generated
of collective cells speed was smaller than the single-cell from cell–boundary interaction were proportional to the
migration speed at the same curvature. area of the cell intersecting the boundary. The invalid
pseudopodia were generated from the node of the cell
3.4. Simulation of cell migration in curved channels perimeter within the boundary. Therefore, the accumulative
The migration of cells in curved channels was simulated intersection area and the number of invalid pseudopodia
based on the modified Odde’s model, which considered were recorded during the simulation, and their correlation
the external force generated by cell–boundary and cell–cell with cell migration speed was analyzed to prove the
interactions (F ), the force acting on the cell body from hypothesis. The results showed that the accumulative
ext
the substrate (F ), the force acting on modules from the intersection area was positively linear and correlated with
cell
substrate (F mod ), and membrane tension (F mem ), with force cell migration speed (Figure 5D). The number of invalid
balance in Cartesian coordinates to calculate cell migration modules was negatively allometric correlated with the cell
(Figure 5A). The adhesion proteins (fibronectin) were migration speed (Figure 5E), indicating that our hypothesis
strained to ensure that the external force generated by cell– was accurate.
boundary and cell–cell interactions was exist (Figure S2).
Altogether, the abovementioned results demonstrated
First, the migration of cells in curved and straight that the M-22 cells can sense and respond to curved
channels with a width of 100 μm was simulated and structures with curvature on the millimeter scale.
compared to the experimental results to estimate the
model’s applicability. The magnitude of the migration speed 4. Discussion
of all groups in the simulation was close to the speed of the
experiment, and the trend of change in migration speed Most cells grow in a curved topographic environment that
with curvature was also consistent with the experimental can impact their behavior and function. Meanwhile, the
findings, indicating that the model can accurately describe structures of the curved scaffolds can affect the activities
the migration of cells in the curved channels (Figure 5B). of the seeded cells, which is crucial for the success of
tissue engineering. The curvatures at the organ level
Subsequently, the cell migration in the channels with (millimeter scale) sensed by cells are approximately planar.
different widths (D = 50, 100, 150, and 200 μm) and However, most of the research was concentrated on the
various radii (R = 1.5, 2, 2.5, 3, and infinite mm) was effect of micro- and nano-scale spatial curvature on cells,
simulated. Interestingly, the maximum migration speed underestimating the importance of milli-scale planar
was observed at various radii when the width of channels curvatures. In this study, planar channels with 1.5, 2, 2.5, 3,
was different. The cell migrated the fastest at R1.5 when the and infinity (straight line) mm in radius, 100 μm in width,
channel width was 200 μm, but migrated fastest at R2 when and 150 μm in depth were printed on the silicide glass sheets
the channel width was 150, 100, and 50 μm. The radius to investigate the effect of planar milli-scale curvature on
corresponding to the maximum migration speed increased the proliferation, morphology, orientation, and migration
as the channel width decreased, implying that the width of the spindle cells (M-22 cells). We demonstrated that
of the induced channel and the relative size of the cells the curved channels had a more significant impact on the
affected the migration speed of cells in the channels with cells than straight channels, with differences between
the same curvature. Moreover, the migration speed was the curved groups. The cell proliferation and migration
increased with a decrease in channel width at the same speed first increased and then decreased with increasing
curvature, which was consistent with the experiment in channel radius, reaching a maximum in group R2. The
reference . cells were first round in shape and then elongated as the
[38]
Furthermore, the mechanism by which curvature radius increased, and were roundest at R2. The orientation
affected cell behavior was explored. We observed and angle fluctuated with increasing radius, and cells were the

Volume 9 Issue 3 (2023) 45 https://doi.org/10.18063/ijb.681