Inhibition of CXCR1/2 reduces muscularization and leukocyte infiltration into lungs of L1Cre(+)Bmpr2^f/f mice. The left lung from L1Cre(−)Bmpr2^f/f (Ai) and L1Cre(+)Bmpr2^f/f mice (Aii) treated with vehicle or SCH527123 was inflated with 1% (volume/volume) formalin, processed for histologic assessment, and then stained with anti-VWF and anti–α-SMA. The extent of α-SMA staining as a measure of pulmonary artery muscularization was assessed in 100 small vessels (30-70 μm) per animal and assigned as nonmuscularized (no α-SMA staining), partially muscularized, or fully muscularized (thick unbroken wall of smooth muscle), and the percentage distribution of each calculated per group (B). Data are the mean ± SEM for a minimum of 8 animals per group. *P < .05, ***P < .001 compared with L1Cre(−)Bmpr2^f/f mice by Dunnett test. Slides were mounted using VECTORSHIELD (Vector Laboratories) and viewed using a 20× objective lens. Images were captured using a DMLB microscope and digital camera. Digital image acquisition was performed using IM50 Version 4.0 imaging software (Leica Microsystems) and digital image slide viewing using ImageScope software (Aperio Technologies).