In vivo pulmonary vascular lesions overexpress ID3, VEGFR3, and Pyk2. Lung vascular lesions from the rodent SuHx model of severe PAH were stained with antibodies against: ID3 (blue), VEGFR3 (red), and Pyk2 (green) followed by immunofluorescent detection by confocal microscopy. (A) Both vehicle control and 3 wk chronic hypoxia treatment groups showed a uniform monolayer of cells lining the lumen of the pulmonary artery. SU5416-treated lungs exposed to chronic hypoxia for 3 wk (bottom row) showed a partially blocked lumen with cells stacked on top of each other instead of forming a monolayer. Representative images are from one of three lungs per group. Scale bar = 70 μm (B) Percent of cells expressing each marker amongst treatment groups when treated with vehicle control, hypoxia only, and SU5416 + hypoxia. Error bars represent the mean of expressed marker positive cells ± SD. ** p<0.01 vs. Control in normal/control (810), exposed in hypoxia and Sugen 5416/chronic hypoxia condition of lung tissue. Data were analyzed by ANOVA; Tukey HSD test for multiple comparisons.