HUVEC spheroids in collagen were treated with conditioned medium with or without VEGF (25 ng/ml). After 24 h, the cumulative sprout length per spheroid was quantified. Data are representative of three independent experiments with ten spheroids per group. Scale bar, 100 μm. Control vs. Sema3C (− VEGF), *P = 0.0276; control vs. Sema3CΔ13 (− VEGF), *P = 0.0443; control vs. Sema3C (+ VEGF), *P = 0.028 and control vs. Sema3CΔ13 (+ VEGF), *P = 0.032. 