Fig. 5
a Representative histology and b vascular density in 14-day-old rats exposed to either postnatal RA or hyperoxia and treated with either NS or surfactant on postnatal day 4 and either NS or hUC-MSCs (3 × 104 or 3 × 105 cells) on postnatal day 5. The endothelium of the blood vessel with vWF immunoreactivity was indicated by the black arrow. The rats reared in hyperoxia and treated with NS yielded a significantly lower vascular density than those reared in RA and treated with NS or surfactant. Treatment with surfactant and hUC-MSCs (3 × 104 or 3 × 105 cells) significantly augmented the hyperoxia-induced decrease in the vascular density. Treatment with surfactant and hUC-MSCs (3 × 105 cells) more significantly increased vascular density than did the treatment of surfactant and hUC-MSCs (3 × 104 cells). Data are shown as box-and-whisker plots. **P < 0.01 and ***P < 0.001. MSCs mesenchymal stem cells, NS normal saline, O2 oxygen-enriched atmosphere, RA room air, S surfactant, vWF von Willebrand factor