Background: Transforming growth factor beta (TGFβ), a multifunctional cytokine, plays a crucial
role in the accumulation of extracellular matrix components in lung fibrosis, where lung fibroblasts
are considered to play a major role. Even though the effects of TGFβ on the gene expression of
several proteins have been investigated in several lung fibroblast cell lines, the global pattern of
response to this cytokine in adult lung fibroblasts is still unknown.
Methods: We used Affymetrix oligonucleotide microarrays U95v2, containing approximately
12,000 human genes, to study the transcriptional profile in response to a four hour treatment with
TGFβ in control lung fibroblasts and in fibroblasts from patients with idiopathic and sclerodermaassociated
pulmonary fibrosis. A combination of the Affymetrix change algorithm (Microarray Suite
5) and of analysis of variance models was used to identify TGFβ-regulated genes. Additional criteria
were an average up- or down- regulation of at least two fold.
Results: Exposure of fibroblasts to TGFβ had a profound impact on gene expression, resulting in
regulation of 129 transcripts. We focused on genes not previously found to be regulated by TGFβ
in lung fibroblasts or other cell types, including nuclear co-repressor 2, SMAD specific E3 ubiquitin
protein ligase 2 (SMURF2), bone morphogenetic protein 4, and angiotensin II receptor type 1 (AGTR1),
and confirmed the microarray results by real time-PCR. Western Blotting confirmed induction at the protein level of AGTR1, the most highly induced gene in both control and fibrotic lung
fibroblasts among genes encoding for signal transduction molecules.
Upregulation of AGTR1 occurred through the MKK1/MKK2 signalling pathway.
Immunohistochemical staining showed AGTR1 expression by lung fibroblasts in fibroblastic foci
within biopsies of idiopathic pulmonary fibrosis.
Conclusions: This study identifies several novel TGFβ targets in lung fibroblasts, and confirms
with independent methods the induction of angiotensin II receptor type 1, underlining a potential
role for angiotensin II receptor 1 antagonism in the treatment of lung fibrosis.