Hypoxia-induced PVR was delayed in Nbeal2^−/− mice compared with WT mice. Whole-slide scans were obtained using the Leica Aperio VERSA brightfield scope (×40 objective, 0.5-micron resolution). (A) At day 21, hypoxia-induced muscularization of vessels of <50 μm was attenuated in Nbeal2^−/− compared with WT mice. At day 35, hypoxia-induced muscularization of vessels of <50 μm was similar between WT and Nbeal2^−/− mice. (B) Representative α-SMA staining in the distal lung (original magnification ×10; scale bars, 200 μm). (C) At day 21, the hypoxia-induced increase in MWT was prevented in Nbeal2^−/− mice. At day 35, the hypoxia-induced increase in MWT was similar between WT and Nbeal2^−/− mice. (D) Representative vessel images (original magnification ×40; scale bars, 50 μm). Statistics: P ≤.05 by 2-way ANOVA with Tukey post hoc analysis. Comparisons: (∗) WT compared with WT baseline, (#) Nbeal2^−/− compared with Nbeal2^−/− baseline, (^) WT compared with Nbeal2^−/−. HPF, high-powered field; HPX, hypoxia; NMX, normoxia.