Background: Bronchopulmonary dysplasia (BPD) is the most common and serious chronic lung disease of premature infants. Connective tissue growth factor (CTGF) plays an important role in tissue development and remodeling. We have previously shown that targeted overexpression of CTGF in alveolar type II epithelial cells results in BPD-like pathology and activates β-catenin in neonatal mice. Methods: Utilizing this transgenic mouse model and ICG001, a specific pharmacological inhibitor of β-catenin, we tested the hypothesis that β-catenin signaling mediates the effects of CTGF in the neonatal lung. Newborn CTGF mice and control littermates received ICG001 (10 mg/kg/dose) or placebo (dimethyl sulfoxide, equal volume) by daily i.p. injection from postnatal day 5 to 15. Alveolarization, vascular development, and pulmonary hypertension (PH) were analyzed. results: Administration of ICG001 significantly downregulated expression of cyclin D1, collagen 1a1, and fibronectin, which are the known target genes of β-catenin signaling in CTGF lungs. Inhibition of β-catenin signaling improved alveolar and vascular development and decreased pulmonary vascular remodeling. More importantly, the improved vascular development and vascular remodeling led to a decrease in PH. conclusion: β-Catenin signaling mediates the autocrine and paracrine effects of CTGF in the neonatal lung. Inhibition of CTGF-β-catenin signaling may provide a novel therapy for BPD.
INTRODUCTIONBronchopulmonary dysplasia (BPD) is the most common and serious chronic lung disease of premature infants (1). Over the past four decades, the incidence of this disease has significantly increased as a result of improved survival of extremely-low-birthweight infants (2). The pathology of BPD is increasingly being recognized as a developmental arrest of the immature lung caused by injurious stimuli such as mechanical ventilation, oxygen exposure, and intrauterine or postnatal infections. Larger and simplified alveoli, decreased vascular growth, and variable interstitial fibrosis are the key pathological features observed in lungs of infants who died of BPD (1). The combination of decreased vascular growth and excessive pulmonary vascular remodeling leads to pulmonary hypertension (PH) which significantly contributes to the morbidity and mortality of these infants (3). Yet, the underlying cellular and molecular mechanisms are poorly defined, and there is no effective therapy.Connective tissue growth factor (CTGF) is a matricellular protein that plays an important role in tissue development and remodeling (4). Recent studies have highlighted the potential role of CTGF in BPD development and progression. The clinical association of CTGF with BPD is best established by studies demonstrating increased CTGF concentrations in bronchoalveolar lavage fluid from preterm infants developing BPD (5) and increased CTGF expression in lung tissues of infants who died of BPD (6). Multiple studies have examined the potential role of CTGF in experimental BPD and demonstrated that increased CTG...