Department of Pediatrics , University of Toronto , Ontario , Canada .
Am J Physiol 269 : L178-84 ( 1995)
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 .