Defective mural cell coverage of blood vessels from Bmpr2 KD mice. (A) (Top) Elastin-Van Gieson staining of pulmonary arteries from wild-type or Bmpr2 KD mice. Note the rarified appearance of the tunica media. (Middle) Immunoflurescence staining of pulmonary arteries using anti-VWF, labeling endothelial cells, and anti-α-actin, labeling smooth muscle cells. (Bottom) Antismooth muscle α-actin immunohistochemistry of the large intestine. Arrows indicate areas missing SMCs. Bars = 50 μm. (B) Quantification of average wall thickness and wall thickness relative to external diameter of muscular, preacinar pulmonary arteries. Values are means plus or minus SD. *P < .01. (C) Immunoblots of lung extracts from 2 wild-type and 2 KD mice with the indicated antibodies.