Effect of all-trans retinoic acid, testosterone, and dexamethasone on in vitro angiogenesis. hMVEC were cultured on the surface of a three-dimensional fibrin matrix in incubation medium containing 20 ng/mL TNF-α and 20 ng/mL bFGF, supplemented with hormone or vehicle. After 9 days of culture, nonphase contrast photographs were taken with the plane of focus beneath the endothelial surface monolayer. (A) Incubation medium from which bFGF and TNF-α had been omitted; (B) incubation medium + vehicle (0.01% [vol/vol] DMSO); (C) incubation medium + all-trans retinoic acid (1 μmol/L); (D) incubation medium + testosterone (1 μmol/L); (E) incubation medium + dexamethasone (1 μmol/L); (F) incubation medium + vehicle; cross-section through a fibrin matrix perpendicular to the surface of the matrix, stained with hematoxylin and phloxin. Lumens surrounded by endothelial cells are indicated by arrows (original magnification ×40). Bar represents 500 μm (A through E).