Antisense oligonucleotides for PDGF-B and its receptor inhibit mechanical strain-induced fetal lung cell growth

Abstract

An intermittent mechanical strain regimen, which simulates fetal breathing movements, has been shown to enhance DNA synthesis and cell division of fetal rat lung cells. The signaling mechanism through which the physical stimulus is transduced is unknown. Herein, we report that mechanical strain (5% elongation, 60 cycles/min) of fetal lung cells, cultured in a three-dimensional environment provided by Gelfoam sponges, increased the mRNA levels of platelet-derived growth factor B (PDGF-B) and beta-receptor (PDGF-beta-R) within 5 min of the onset of strain. Both PDGF-BB and PDGF-beta-R proteins were increased after a 24-h intermittent strain (15 min/h). Phosphorothioate antisense PDGF-B oligonucleotides (ON) at 15 microM abolished the strain-enhanced DNA synthesis and cell growth. Scrambled PDGF-B ON had no such effect. A neutralizing PDGF-BB antibody (10 micrograms/ml) also attenuated strain-induced DNA synthesis. Furthermore, the strain-induced stimulatory effect on DNA synthesis of fetal lung cells was blocked by tyrphostin 9 (1 microM), a PDGF receptor-associated tyrosine kinase inhibitor, but not by its inactive structural analogue tyrphostin 1. Antisense but not sense PDGF-beta-R ON (10 microM) also abrogated the strain-enhanced DNA synthesis. These results suggest that physical forces such as fetal breathing movements regulate fetal lung cell growth by controlling PDGF-B and PDGF-beta-R gene expression.

Spontaneous Peristaltic Airway Contractions Propel Lung Liquid through the Bronchial Tree of Intact and Fetal Lung Explants

“…But the rhythmic forces the musculature generates are not limited to these highly compliant tissues. It also generates forces across the airway wall and adjacent parenchyma which could well provide the stimulus to growth factor production via mechanotransduction (9,36), a suggestion supported by the finding that a pulsatile stimulus is more effective than a static one in stimulating lung growth in vitro (37,38).…”

Mechanical control of stem cell differentiation

“…Multiple activation mechanisms are simultaneously at play including release of autocrine growth factors (Resnick et al, 1993;Liu et al, 1995;Reusch et al, 1996;Robbins et al, 1997;Cillo et al, 2000;Wu et al, 2001;Zheng et al, 2001;Lindahl et al, 2002), activation of mechanically-sensitive kinases such as Src (Liu et al, 1996;Han et al, 2004;Jiang et al, 2005;Na et al, 2008), FAK (Li et al, 1997;Smith et al, 1998;Leucht et al, 2007), and ERK (Yamazaki et al, 1995;Takahashi and Berk, 1996;Jalali et al, 1998;MacKenna et al, 1998;Schmidt et al, 1998;Chen et al, 2000;Iqbal and Zaidi, 2005), and initiation of second messenger signaling (Sadoshima and Izumo, 1997;Liu et al, 1999). Thus mechanical signals have extensive potential to regulate and synergize with classical biochemical signal transduction pathways induced by soluble factors to control stem cell differentiation.…”

Thoughts on the pulmonary blood-gas barrier

“…It is possible that some other cell in the parenchyma, such as an epithelial cell, fibroblast, or some other pericyte responds to the increased tension and sends a signal to the endothelial cell. It is known that cultures of type II alveolar epithelial cells are responsive to stretch (63), and cultures of pulmonary fibroblasts respond to stretch with an increase in proliferation through an autocrine growth factor mechanism (5) that involves platelet-derived growth factor-B (PDGF-B) (31).…”