Angiogenesis-related gene expression profiling in ventilated preterm human lungs

Preterm infants exposed to oxygen and mechanical ventilation are at risk for bronchopulmonary dysplasia (BPD), a multifactorial chronic lung disorder characterized by arrested alveolar development and nonsprouting, dysmorphic microvascular angiogenesis. The molecular regulation of this BPD-associated pathological angiogenesis remains incompletely understood. In this study, the authors used focused microarray technology to characterize the angiogenic gene expression profile in postmortem lung samples from short-term ventilated preterm infants (born at 24 to 27 weeks' gestation) and age-matched control infants. Microarray analysis identified differential expression of 13 of 112 angiogenesis-related genes. Genes significantly up-regulated in ventilated lungs included the antiangiogenic genes thrombospondin-1, collagen XVIII alpha-1, and tissue inhibitor of metalloproteinase-1 (TIMP1), as well as endoglin, transforming growth factor-alpha, and monocyte chemoattractant protein-1 (CCL2). Increased expression of thrombospondin-1 in ventilated lungs was verified by real-time polymerase chain reaction (PCR) and immunolocalized primarily to intravascular platelets and fibrin aggregates. Down-regulated genes included proangiogenic angiogenin and midkine, as well as vascular endothelial growth factor (VEGF)B, VEGF receptor-2, and the angiopoietin receptor TEK/Tie-2. In conclusion, short-term ventilated lungs show a shift from traditional angiogenic growth factors to alternative, often antisprouting regulators. This angiogenic shift may be implicated in the regulation of dysmorphic angiogenesis and, consequently, deficient alveolarization characteristic of infants with BPD.