Yonsei Med J.  2014 Jan;55(1):99-106. 10.3349/ymj.2014.55.1.99.

Rosiglitazone, a Peroxisome Proliferator-Activated Receptor-gamma Agonist, Restores Alveolar and Pulmonary Vascular Development in a Rat Model of Bronchopulmonary Dysplasia

• Lee HJ
• Lee YJ
• Choi CW
• Lee JA
• Kim EK
• Kim HS
• Kim BI
• Choi JH

• KMID: 1779892
• DOI: http://doi.org/10.3349/ymj.2014.55.1.99

Abstract

PURPOSE
We tested whether rosiglitazone (RGZ), a peroxisome proliferator-activated receptor-gamma agonist, can restore alveolar development and vascular growth in a rat model of bronchopulmonary dysplasia (BPD).
MATERIALS AND METHODS
A rat model of BPD was induced through intra-amniotic delivery of lipopolysaccharide (LPS) and postnatal hyperoxia (80% for 7 days). RGZ (3 mg/kg/d, i.p.) or vehicle was given daily to rat pups for 14 days. This model included four experimental groups: No BPD+vehicle (V), No BPD+RGZ, BPD+V, and BPD+RGZ. On D14, alveolarization, lung vascular density, and right ventricular hypertrophy (RVH) were evaluated.
RESULTS
Morphometric analysis revealed that the BPD+RGZ group had significantly smaller and more complex airspaces and larger alveolar surface area than the BPD+V group. The BPD+RGZ group had significantly greater pulmonary vascular density than the BPD+V group. Western blot analysis revealed that significantly decreased levels of vascular endothelial growth factor (VEGF) and its receptor VEGFR-2 by the combined exposure to intra-amniotic LPS and postnatal hyperoxia were restored by the RGZ treatment. RVH was significantly lesser in the BPD+RGZ group than in the BPD+V group.
CONCLUSION
These results suggest that RGZ can restore alveolar and pulmonary vascular development and lessen pulmonary hypertension in a rat model of BPD.

Keyword

Bronchopulmonary dysplasia; peroxisome proliferator-activated receptor-gamma; rosiglitazone; alveolarization

MeSH Terms

Animals
Bronchopulmonary Dysplasia/*drug therapy
Female
Hypertension, Pulmonary/drug therapy
Immunohistochemistry
Lung/drug effects/pathology
PPAR gamma/*agonists
Rats
Rats, Sprague-Dawley
Thiazolidinediones/*therapeutic use
Vasodilator Agents/*therapeutic use
PPAR gamma
Thiazolidinediones
Vasodilator Agents

Figure

• 

  Fig. 1 Alveolar development. Representative photomicrographs of the lung sections on D14 are displayed (A). Top left: No BPD+V, top right: No BPD+RGZ, bottom left: BPD+V, bottom right: BPD+RGZ. Rosiglitazone significantly restored alveolarization, which was significantly inhibited by intra-amniotic LPS administration and postnatal hyperoxia exposure (smaller and more complex airspaces are noted in the BPD+RGZ group than in the BPD+V group). H&E stained. Magnification ×200. Scale bar indicates 100 µm. Morphometric data are shown (B and C). Mean cord length (B) and surface area (C) are displayed in bar graphs. Rosiglitazone significantly decreased Lm and increased SA in the animals which were exposed to intra-amniotic LPS and postnatal hyperoxia, but not in the animals which were not exposed to intra-amniotic LPS or postnatal hyperoxia (No BPD groups). *p<0.05 versus No BPD+V, †p<0.05 versus BPD+V. BPD, bronchopulmonary dysplasia; RGZ, rosiglitazone; V, vehicle; LPS, lipopolysaccharide.

• 

  Fig. 2 Pulmonary vascular development. Representative PECAM-1 immunohistochemistry photomicrographs of the lung sections on D14 are displayed (A). Top left: No BPD+V, top right: No BPD+RGZ, bottom left: BPD+V, bottom right: BPD+RGZ. Rosiglitazone significantly restored pulmonary vascular development, which was significantly inhibited by intra-amniotic LPS administration and postnatal hyperoxia exposure. Arrows indicate vessels stained with PECAM-1. Magnification ×400. Scale bar indicates 50 µm. The number of vessels per high-powered field (HPF) is displayed in a bar graph (B). The number of vessels per HPF, which was significantly decreased by intra-amniotic LPS administration and postnatal hyperoxia exposure, was significantly increased by the rosiglitazone treatment. However, in the animals which were not exposed to intra-amniotic LPS or postnatal hyperoxia (No BPD groups), rosiglitazone did not alter the number of vessels per HPF. Vascular density (PECAM-1-positive area as a proportion of total area of lung parenchyme) is displayed in a bar graph (C). The vascular density, which was significantly decreased by intra-amniotic LPS administration and postnatal hyperoxia, was increased by the rosiglitazone treatment. However, in the animals in the No BPD groups, rosiglitazone did not alter vascular density. *p<0.05 versus No BPD+V, †p<0.05 versus BPD+V. BPD, bronchopulmonary dysplasia; RGZ, rosiglitazone; V, vehicle; LPS, lipopolysaccharide; PECAM, platelet endothelial cell adhesion molecule.

• 

  Fig. 3 Angiogenic growth factor VEGF and its receptor VEGFR-2 levels in the lungs on D14. Lung VEGF (A) and VEGFR-2 (B) levels are displayed in bar graphs. Combined exposure to intra-amniotic LPS and postnatal hyperoxia significantly decreased VEGF and VEGFR-2 levels in the lungs. Rosiglitazone restored lung VEGF and VEGFR-2 levels in the animals which were exposed to intra-amniotic LPS and postnatal hyperoxia to comparable levels in the animals which were not exposed to intra-amniotic LPS or postnatal hyperoxia (No BPD groups). However, rosiglitazone did not alter lung VEGF and VEGFR-2 levels in the No BPD groups. *p<0.05 versus No BPD+V. BPD, bronchopulmonary dysplasia; RGZ, rosiglitazone; V, vehicle; VEGF, vascular endothelial growth factor; LPS, lipopolysaccharide.

• 

  Fig. 4 Fulton's index for right ventricular hypertrophy on D14 as a marker of pulmonary hypertension. Rosiglitazone significantly decreased Fulton's index (right ventricular weight/weight of left ventricle plus interventricular septum) in the animals exposed to intra-amniotic LPS and postnatal hyperoxia. However, rosiglitazone did not cause alternation in the Fulton's index in the animals which were not exposed to intra-amniotic LPS or postnatal hyperoxia. †p<0.05 versus BPD+V. RV, right ventricle; LV, left ventricle; IVS, interventricular septum; BPD, bronchopulmonary dysplasia; RGZ, rosiglitazone; V, vehicle; LPS, lipopolysaccharide.

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