CTGF disrupts alveolarization and induces pulmonary hypertension in neonatal mice: implication in the pathogenesis of severe bronchopulmonary dysplasia

Abstract

S. CTGF disrupts alveolarization and induces pulmonary hypertension in neonatal mice: implication in the pathogenesis of severe bronchopulmonary dysplasia. Am J Physiol Lung Cell Mol Physiol 300: L330 -L340, 2011. First published January 14, 2011; doi:10.1152/ajplung.00270.2010.-The pathological hallmarks of bronchopulmonary dysplasia (BPD), one of the most common long-term pulmonary complications associated with preterm birth, include arrested alveolarization, abnormal vascular growth, and variable interstitial fibrosis. Severe BPD is often complicated by pulmonary hypertension characterized by excessive pulmonary vascular remodeling and right ventricular hypertrophy that significantly contributes to the mortality and morbidity of these infants. Connective tissue growth factor (CTGF) is a multifunctional protein that coordinates complex biological processes during tissue development and remodeling. We have previously shown that conditional overexpression of CTGF in airway epithelium under the control of the Clara cell secretory protein promoter results in BPD-like architecture in neonatal mice. In this study, we have generated a doxycycline-inducible double transgenic mouse model with overexpression of CTGF in alveolar type II epithelial (AT II) cells under the control of the surfactant protein C promoter. Overexpression of CTGF in neonatal mice caused dramatic macrophage and neutrophil infiltration in alveolar air spaces and perivascular regions. Overexpression of CTGF also significantly decreased alveolarization and vascular development. Furthermore, overexpression of CTGF induced pulmonary vascular remodeling and pulmonary hypertension. Most importantly, we have also demonstrated that these pathological changes are associated with activation of integrin-linked kinase (ILK)/glucose synthesis kinase-3␤ (GSK-3␤)/␤-catenin signaling. These data indicate that overexpression of CTGF in AT II cells results in lung pathology similar to those observed in infants with severe BPD and that ILK/GSK-3␤/␤-catenin signaling may play an important role in the pathogenesis of severe BPD.

Pentoxifylline and prevention of hyperoxia-induced lung ­injury in neonatal rats

“…Alveolarization was assessed on hematoxylin-eosin stained tissue sections by radial alveolar count and by mean linear intercept as previously described (41,42).…”

“…Ten random images were taken with the ×20 objective on each von Willebrand factor-stained slide. The vascular density was expressed as the average number of von Willebrand factor-positive vessels (15-50 µm) counted per high-power field as previously described (42).…”

“…Total RNA isolation and cDNA reverse transcription were performed as previously described (42). Reverse-transcriptase PCR was performed using a pair of rat VEGF primers: sense, 5′-CCAGCACATAGGAGAGATGAGCTTC-3′ and antisense, 5′-GG TGTGGTGGTGACATGGTTAATC-3′, which resulted in three bands (262, 394, and 466 bp) corresponding to the three principal VEGF isoforms VEGF121, VEGF165, and VEGF189, respectively, expressed in rats (43).…”

Inhibition of β-catenin signaling protects against CTGF-induced alveolar and vascular pathology in neonatal mouse lung

“…Recent studies from our laboratory utilizing genetic gain-of-function and biological loss-of-function approaches have provided compelling evidence that a novel signaling network orchestrated by CTGF plays an important role in BPD pathogenesis (6,11,12). In our novel transgenic mouse model, targeted overexpression of CTGF in alveolar type II epithelial (AT II) cells induces the pathological hallmarks of severe BPD, including decreased alveolar and vascular development and increased vascular remodeling and PH (12). In contrast, in a hyperoxia-induced rat model of BPD, administration of a CTGF-neutralizing antibody improved alveolar and vascular development and decreased pulmonary vascular remodeling and PH (6).…”

“…Multiple studies have examined the potential role of CTGF in experimental BPD and demonstrated that increased CTGF expression is associated with chronic hyperoxia as well as mechanical ventilationinduced lung injury in neonatal rodents (6-10). Recent studies from our laboratory utilizing genetic gain-of-function and biological loss-of-function approaches have provided compelling evidence that a novel signaling network orchestrated by CTGF plays an important role in BPD pathogenesis (6,11,12). In our novel transgenic mouse model, targeted overexpression of CTGF in alveolar type II epithelial (AT II) cells induces the pathological hallmarks of severe BPD, including decreased alveolar and vascular development and increased vascular remodeling and PH (12).…”