In vitro angiogenic functions of LBW-ECFCs and CT-ECFCs. ECFCs were used at passage 3 as described in “Methods.” (A) Proliferation assayed by BrdU incorporation in 10 000 ECFCs. Results were expressed in arbitrary units of spectrophotometric measurements. Filled symbols indicate LBW preterm neonates with IUGR: (★), 680 g, 29 weeks; (●), 930 g, 31 weeks; (▾), 940 g, 32 weeks; (▴), 1700 g, 35 weeks; and (■), 2000 g, 36 weeks. Data are mean ± SEM of 25 independent experiments performed in triplicate. *P < .03. **P < .01. ***P < .001. (B) Representative experiment of capillary tube formation by ECFCs from a < 1500-g VLBW neonate and a > 2700-g control neonate. A total of 20 000 ECFCs/well were seeded on top of growth factor-reduced Matrigel. Tube formation was analyzed 6 and 24 hours later on a phase-contrast microscope (original magnification 20×/0.45). Scale bars represent 50 μm. Representative experiment in capillary tube formation by ECFCs from a < 1500-g VLBW neonate at 6 (i) and 24 hr (ii) and a > 2700-g control neonate at the same times (iii-iv). (C) Relative quantification of total tube (top panel), tube length (central panel), and branches (bottom panel) according to birth weight at 6 hours (gray bars) and 24 hours (black bars). Data are mean ± SEM of 25 independent experiments, each performed in triplicate. *P < .05, **P < .01, ***P < .001 vs CT at 6 hours. ‡P < .05, ‡‡P < .02 vs CT at 24 hours. (D) Representative experiment of capillary-like sprout formation from 3D spheroids obtained with ECFCs from < 1500-g extremely LBW neonate (i) and > 2700-g control neonate (original magnification ×20). Scale bars represent 50 μm. Representative experiment of capillary-like sprout formation from 3D spheroids obtained with ECFCs. (E) Quantification of sprout numbers (top panel) and sprout length (bottom panel) formed by ECFCs according to birth weight. Data are mean ± SEM of 10 independent experiments performed in triplicate. (), 6 hours: *P < .06, **P < .01, ***P < .001. (), 24 hours: ‡P < .001, ‡‡P < .01. NS indicates not significant.