Fig. 4. TWEAK synergizes with bFGF to enhance microvessel formation. (A) Phase contrast images (all panels at 4x magnification) of HUVECs on the surface of fibrin gel matrices after three days of culture, untreated or treated with bFGF, TWEAK or bFGF + TWEAK. Results are representative of eight independent experiments. (B) Hematoxylin and eosin-stained cross-sections of the fibrin gel cultures (all panels at 20x magnification; scale bar, 100 µm). EC cells in untreated and TWEAK-treated cultures remain on the fibrin gel surface, bFGF-treated cultures exhibit invading cord-like structures, and TWEAK + bFGF-treated cultures show the structural organization of endothelial lumens (indicated by arrowheads). (C) The same cultures as in (A), with or without factors and anti-TNF and anti-IL-8 mAbs, as indicated. Capillary sprouts were counted visually using five fields per well, and the mean number per culture was normalized to the bFGF treatment, which was defined as 100%. Results are representative of seven independent experiments. The percentage increase in all of the TWEAK + bFGF treated groups was significantly higher than that in all groups treated with bFGF alone (asterisks indicate p<0.05 by Dunnett’s method), and there was no significant effect of anti-TNF, anti-IL-8 or control Ig.
