Cloning and Expression of Glucocorticoid-induced Genes in Fetal Rat Lung Fibroblasts

doi:10.1074/jbc.270.6.2722

Cloning and Expression of Glucocorticoid-induced Genes in Fetal Rat Lung Fibroblasts

TRANSFORMING GROWTH FACTOR-β₃(*)

From the Medical Research Council Group in Lung Development and the Neonatal Research Division, Department of Paediatrics, Hospital for Sick Children Research Institute, University of Toronto, Toronto, Ontario M5G 1X8, Canada

^§ To whom correspondence should be addressed:
Div. Neonatology, Hospital for Sick Children, 555 University Ave., Toronto, Ontario, M5G 1X8, Canada.
Tel.: 416-598-6772; Fax: 416-813-5002.

Abstract

Glucocorticoids have been shown to accelerate fetal lung type II cell maturation, and this effect appears, in part, to be mediated via fibroblasts. To identify glucocorticoid induced genes in fetal lung fibroblasts, we screened a cDNA library from cortisol-treated fetal lung fibroblasts with a subtracted cDNA probe which was enriched for sequences specific for cortisol-treated fetal lung fibroblasts. Fifty-seven clones were isolated from the cDNA library. One cDNA represented ≈30% of the 57 clones. Analysis of DNA sequence homology suggested that this cDNA encodes the rat transforming growth factor-β₃ (TGFβ₃). We found that TGFβ₃ mRNA was expressed in fetal lung fibroblasts but not epithelial cells. Expression of message in fetal lung fibroblasts was developmentally regulated. TGFβ₃ mRNA levels were low during the pseudoglandular stage (day 18), peaked during the early canalicular stage of lung development (day 19), then fell again at days 20 and 21 (term = 22 days). Exposure of fetal lung fibroblasts to cortisol increased TGFβ₃ mRNA expression in a time- and dose-dependent manner. Maternal administration of dexamethasone also enhanced mRNA expression of TGFβ₃ in fetal lung fibroblasts. These data suggest that glucocorticoids may mediate their stimulatory effect on lung maturation by inducing TGFβ₃ expression in fetal lung fibroblasts.

Footnotes

↵* These studies were supported by a group grant from the Medical Research Council of Canada and an equipment grant from the Ontario Thoracic Society. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank(TM)/EMBL Data Bank with accession number(s) U03491[GenBank].
↵¹ The abbreviations used are:

TGFβ₃

transforming growth factor-β₃

bp

base pair(s)

GAPDH

glyceraldehyde-3-phosphate dehydrogenase

kb

kilobase(s)

PCR

polymerase chain reaction

MEM

Eagle's minimal essential medium

PIPES

1,4-piperazinediethanesulfonic acid

DSPC

disaturated phosphatidylcholine

FPF

fibroblast pneumocyte factor.
- Received July 29, 1994.
- Revision received September 22, 1994.