Figure 3.

Sustained Slit2 delivery using sodium alginate bead microencapsulation inhibits medulloblastoma cell invasion. (a) Schematic showing the position of sodium alginate beads relative to the tumor spheroid. Arrow represents placement of sodium alginate bead. (b) Western blot analysis of Slit2 expression (~200 kDa) in conditioned medium of encapsulated Slit2 cells over 6 days. Lanes 1 and 2 represent conditioned medium from human embryonic kidney (HEK) and Slit2 monolayer cultures as negative and positive controls, respectively. Lanes 3–5 represent conditioned medium from Slit2 beads on days 1, 3 and 6 in culture. Lanes 6–7 represent conditioned medium from HEK beads on days 3 and 6. (c–e) Photographs of UW3 spheroids surrounded by (c) four empty beads, (d) four beads encapsulating HEK cells and (e) four beads encapsulating Slit2 cells. Scale bar = 250 μm. (f–h) Quantification of total invasion by (f) UW3 spheroids, (g–h) C6 and U251 glioma spheroids implanted with empty, HEK or Slit2 beads. Error bars represent s.e.m. Asterisks indicate significance at P < 0.05, P < 0.01** and P < 0.001***. (i–k) Confocal images of UW3 spheroids (DiI labeled-red) confronted with human fetal astrocyte aggregates (DiO labeled-green) in the presence of (i) HEK sodium alginate beads or (j) Slit2 sodium alginate beads after 5 days. Scale bar 250 μm. Results are representative of three independent trials. (k) Quantification of the number of medulloblastoma cells infiltrating astrocyte aggregates after 5 days.