An essential role for resident fibroblasts in experimental lung fibrosis is defined by lineage-specific deletion of high-affinity type II transforming growth factor β receptor.
BACKGROUND
Fibrotic response to lung injury depends on development of a fibrogenic population of myofibroblasts. The importance of resident interstitial fibroblasts and role of transforming growth factor β (TGFβ) in this process is unclear.


OBJECTIVE
To define the importance of TGFβ signaling in resident lung fibroblasts in the development of experimental pulmonary fibrosis.


METHODS
A compound genetic strategy in which mice homozygous for a floxed high-affinity type II TGFβ receptor (TβRII) allele were crossed with a transgenic strain harboring a fibroblast-specific transgene encoding ligand-dependent Cre-recombinase was used. TβRII was deleted by postnatal administration of tamoxifen over 5 days to compound mutant mice with appropriate littermate controls. Illumina microarray gene profiling and quantitative reverse transcriptase-polymerase chain reaction were used to confirm anergy to TGFβ in explanted lung fibroblasts. Bleomycin lung injury was used to induce lung fibrosis, which was analyzed by histology and biochemical methods. Immunofluorescence was used to define cell populations after lung injury.


RESULTS
There was significant attenuation of fibrosis in mice after deletion of TβRII in resident fibroblasts. At 7 days after injury the number of fibrocytes and myofibroblasts was substantially reduced. Potential regulators of fibrosis were suggested by gene expression profiles that identified key candidate profibrotic genes, including connective tissue growth factor and endothelin-1 expressed by wild-type but not mutant lung fibroblasts.


CONCLUSIONS
Intact TGFβ signaling in resident pulmonary fibroblasts is essential for pulmonary fibrosis to develop. Our data support a key regulatory role of these cells in determining fibrocyte recruitment and myofibroblast differentiation.
Hoyles
Rachel K
RK
Centre for Rheumatology and Connective Tissue Diseases, UCL Medical School, Royal Free Campus, London, United Kingdom.
Derrett-Smith
Emma C
EC
Khan
Korsa
K
Shiwen
Xu
X
Howat
Sarah L
SL
Wells
Athol U
AU
Abraham
David J
DJ
Denton
Christopher P
CP
D000818:Animals; D001761:Bleomycin; D015153:Blotting, Western; D019070:Cell Lineage; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D020869:Gene Expression Profiling / Q000379:methods; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D040081:Protein Array Analysis / Q000379:methods; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D011658:Pulmonary Fibrosis / Q000235:genetics* / Q000378:metabolism*; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D017384:Sequence Deletion / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D013629:Tamoxifen; D014158:Transcription, Genetic / Q000235:genetics
D018125:Receptors, Transforming Growth Factor beta; D013629:Tamoxifen; D001761:Bleomycin; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II