Figure 1

Migration tracks of cells under varying neural differentiation states in response to SDF-1α. (a) Morphological features of MSCs under varying neural differentiation states including undifferentiation, 24-h preinduction, 5-h induction, 18- and 48-h maintenance (upper panel) and the representative cell of each state in the boxed area is enlarged to the bottom right corner (lower panel). (b) Schematic representation of Dunn chamber with the overlying coverslip, showing the position of the inner well, bridge, and outer well. (c) Cells over the annular bridge between the inner and outer well of Dunn chamber can be observed under phase-contrast optics. The black arrow on the top right corner indicates the direction of the outer well and the left bottom one indicates the inner well. Cell migration on the bridge was recorded continuously by time-lapse frame grabbing. (d) Schematic diagram of migration tracks, the starting point for each cell is the intersection between the X- and Y- axes (0, 0), and the source of SDF-1α is at the top. (e) Representative time-lapse sequences of cell migration in varying neural differentiation states in the absence or presence of SDF-1α. Arrowheads indicate the source of SDF-1α. (f–h) FMI values, migration speed (μm/min) and CXCR4 expression of MSCs under varying differentiation states. FMI is the ratio of effective displacement to the total path length²⁸. Migration speed was calculated for each time-lapse interval (5 minutes), and the mean speed was derived for 4 hours. CXCR4 expression was detected by RT-qPCR. Untreated cells were in serum-free medium without SDF-1α (bars in gray), chemotaxis was studied by adding SDF-1α in the outer well (bars in dark) (>20 cells, n = 3). Data represent the mean ± SEM from at least three independent experiments. Scale bar: 50 μm. Differences were considered statistically significant when *P < 0.05, **P < 0.01 compared with SDF-1α group of each state and ^#P < 0.05, ^##P < 0.01 compared with any other groups under the same treatment.