PDGF-Rα gene expression predicts proliferation, but PDGF-A suppresses transdifferentiation of neonatal mouse lung myofibroblastsReport as inadecuate




PDGF-Rα gene expression predicts proliferation, but PDGF-A suppresses transdifferentiation of neonatal mouse lung myofibroblasts - Download this document for free, or read online. Document in PDF available to download.

Respiratory Research

, 10:119

First Online: 25 November 2009Received: 27 April 2009Accepted: 25 November 2009

Abstract

BackgroundPlatelet-derived growth factor A PDGF-A signals solely through PDGF-Rα, and is required for fibroblast proliferation and transdifferentiation fibroblast to myofibroblast conversion during alveolar development, because pdgfa-null mice lack both myofibroblasts and alveoli. However, these PDGF-A-mediated mechanisms remain incompletely defined. At postnatal days 4 and 12 P4 and P12, using mouse lung fibroblasts, we examined a how PDGF-Rα correlates with ki67 proliferation marker or alpha-smooth muscle actin αSMA, myofibroblast marker expression, and b whether PDGF-A directly affects αSMA or modifies stimulation by transforming growth factor beta TGFβ.

MethodsUsing flow cytometry we examined PDGF-Rα, αSMA and Ki67 in mice which express green fluorescent protein GFP as a marker for PDGF-Rα expression. Using real-time RT-PCR we quantified αSMA mRNA in cultured Mlg neonatal mouse lung fibroblasts after treatment with PDGF-A, and-or TGFβ.

ResultsThe intensity of GFP-fluorescence enabled us to distinguish three groups of fibroblasts which exhibited absent, lower, or higher levels of PDGF-Rα. At P4, more of the higher than lower PDGF-Rα + fibroblasts contained Ki67 Ki67+, and Ki67+ fibroblasts predominated in the αSMA + but not the αSMA- population. By P12, Ki67+ fibroblasts comprised a minority in both the PDGF-Rα + and αSMA+ populations. At P4, most Ki67+ fibroblasts were PDGF-Rα + and αSMA- whereas at P12, most Ki67+ fibroblasts were PDGF-Rα- and αSMA-. More of the PDGF-Rα + than - fibroblasts contained αSMA at both P4 and P12. In the lung, proximate αSMA was more abundant around nuclei in cells expressing high than low levels of PDGF-Rα at both P4 and P12. Nuclear SMAD 2-3 declined from P4 to P12 in PDGF-Rα-, but not in PDGF-Rα + cells. In Mlg fibroblasts, αSMA mRNA increased after exposure to TGFβ, but declined after treatment with PDGF-A.

ConclusionDuring both septal eruption P4 and elongation P12, alveolar PDGF-Rα may enhance the propensity of fibroblasts to transdifferentiate rather than directly stimulate αSMA, which preferentially localizes to non-proliferating fibroblasts. In accordance, PDGF-Rα more dominantly influences fibroblast proliferation at P4 than at P12. In the lung, TGFβ may overshadow the antagonistic effects of PDGF-A-PDGF-Rα signaling, enhancing αSMA-abundance in PDGF-Rα-expressing fibroblasts.

List of abbreviations usedPDGF-APlatelet-derived growth factor A

αSMAAlpha-smooth muscle actin

PDGF-RαPlatelet-derived growth factor receptor alpha

TGFβTransforming growth factor beta

GFPGreen fluorescent protein

SMADHomologs of the drosophila protein, Mothers Against Decapentaplegic MAD and the C. elegans protein, SMA

P4postnatal day 4

ECMExtracellular matrix

PBS0.145 M NaCl, 0.0015 M KH2PO4, 0.0027 M KCl, 0.0086 M Na2HPO4, pH 7.4;

BSAbovine serum albumin

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Author: Patricia W Kimani - Amey J Holmes - Ruth E Grossmann - Stephen E McGowan

Source: https://link.springer.com/



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