VEGF ameliorates pulmonary hypertension through inhibition of endothelial apoptosis in experimental lung fibrosis in rats
Laszlo Farkas, Daniela Farkas, Kjetil Ask, Antje Möller, Jack Gauldie, Peter Margetts, Mark Inman, Martin Kolb
Laszlo Farkas, Daniela Farkas, Kjetil Ask, Antje Möller, Jack Gauldie, Peter Margetts, Mark Inman, Martin Kolb
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Research Article Pulmonology

VEGF ameliorates pulmonary hypertension through inhibition of endothelial apoptosis in experimental lung fibrosis in rats

Abstract

Idiopathic pulmonary fibrosis (IPF) can lead to the development of secondary pulmonary hypertension (PH) and ultimately death. Despite this known association, the precise mechanism of disease remains unknown. Using a rat model of IPF, we explored the role of the proangiogenic and antiapoptotic growth factor VEGF in the vascular remodeling that underlies PH. In this model, adenoviral delivery of active TGF-β1 induces pulmonary arterial remodeling, loss of the microvasculature in fibrotic areas, and increased pulmonary arterial pressure (PAP). Immunohistochemistry and mRNA analysis revealed decreased levels of VEGF and its receptor, which were inversely correlated with PAP and endothelial cell apoptosis in both the micro- and macrovasculature. Treatment of IPF rats with adenoviral delivery of VEGF resulted in reduced endothelial apoptosis, increased vascularization, and improved PAP due to reduced remodeling but worsened PF. These data show that experimental pulmonary fibrosis (PF) leads to loss of the microvasculature through increased apoptosis and to remodeling of the pulmonary arteries, with both processes resulting in PH. As administration of VEGF ameliorated the PH in this model but concomitantly aggravated the fibrogenic process, VEGF-based therapies should be used with caution.

Authors

Laszlo Farkas, Daniela Farkas, Kjetil Ask, Antje Möller, Jack Gauldie, Peter Margetts, Mark Inman, Martin Kolb

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Figure 1

PF, PH, TGF-β signaling, and vascular density in AdTGF-β1–induced PF.

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PF, PH, TGF-β signaling, and vascular density in AdTGF-β1–induced PF. (A...
(A–C) PSR-stained sections from AdTGF-β1 rats at days 14 (A), 21 (B), and 56 (C) (dark field, polarized light). (D) mPAP after AdTGF-β1. White bars, AdDL70; black bars, AdTGF-β1. (E–J) Representative images for P-Smad2 (red) at day 7 in AdTGF-β1–treated (E–G) and AdDL70-treated animals (H–J). (K) Percentage of P-Smad2–positive versus total nuclei in lung parenchyma categorized according to PF degree. (L–O) Representative IHC for CD31 (L and M) and CD34 (N and O) in regions with severe PF after AdTGF-β1 (L and N) compared with AdDL70 (M and O) administration. All day 56. (P and Q) Percentage of CD31+ (P) and CD34+ (Q) area versus tissue area in lung parenchyma categorized according to PF degree. (R and S) CD34 staining is absent in α-SMA+ fibroblastic foci (dotted line) (R) and decreased in areas of high nuclear P-Smad2 immunoreactivity (red) (dotted line: fibroblastic focus) (S). Original magnification, ×25 (A–C); ×400 (E–J, L–O, and S); ×630 (R). Scale bars: 500 μm (A–C); 50 μm (G, J, L–O, R, and S). Each bar shows mean ± SEM of 3–4 animals per group (K) and 4–6 animals per group (D, P, and Q). *P < 0.05; **P < 0.01; ***P < 0.0001 (all versus AdDL70); †P < 0.05; ‡P < 0.01 (both versus Ashcroft 0–1); #P < 0.05 (1-way ANOVA).