LL-37 enhances the pro-angiogenic activity of MSCs. (A) LL-37 or the combination of FGF and VEGFA was added to cold Matrigel with or without MSCs and injected into nude mice (n < 6). The absence of growth factors and cells served as negative control. After 7 to 10 days, Matrigel plugs were surgically removed, fixed, sectioned, and stained by H&E. Representative images of vascular channels are shown. (Scale bar, 100 μm.) (B) The average number of vascular channels in each plug section was determined by counting 3 high-powered fields of view then graphically represented. Values are mean ± SE. *, P < 0.05, **, P < 0.01, ***, P < 0.001. (C) Example of MSCs in perivascular areas identified by Ki-67 staining. (D) Fluorescently labeled, serum-starved MSCs were seeded onto Matrigel in the presence of 5 μg/mL LL-37 or 10 ng/mL FGF2 and allowed to incubate overnight. Formation of tubules, indicative of their pericyte-like differentiation, was captured by microscopy at ×200 the next day.