Effect of steroid hormones, retinoids, thyroid hormone, and 1,25-dihydroxyvitamin D3 on tube formation. hMVEC were cultured on the surface of a three-dimensional fibrin matrix in incubation medium containing 20 ng/mL bFGF and 20 ng/mL TNF-α. (A) Shows the effect of vehicle, 0.01% (vol/vol) DMSO (con) or 1 μmol/L 17β-estradiol (E2), testosterone (test), progesterone (prog), dexamethasone (dex), or 2-methoxyestradiol (2-ME) and (B) shows the effect of 1 μmol/L of 1,25-dihydroxyvitamin D3 (D3), thyroid hormone (T3), all-transretinoic acid (at-RA), or 9-cis retinoic acid (9-cis RA) on tube formation. The data represent the average ± SD of three to six experiments with the number of experiments indicated in parentheses for each condition, with each experiment performed in duplicate, and are expressed as percentage of control values. Total tube-length/cm² under control conditions ranged from 32 to 329 mm/cm² (average = 130 mm/cm²) between the different experiments. * P< .05, *** P < .0001.