Human lung parenchyma but not proximal bronchi produces fibroblasts with enhanced TGF-beta signaling and alpha-SMA expression.

TitleHuman lung parenchyma but not proximal bronchi produces fibroblasts with enhanced TGF-beta signaling and alpha-SMA expression.
Publication TypeJournal Article
Year of Publication2010
AuthorsPechkovsky, DV, Hackett, TL, An, SS, Shaheen, F, Murray, LA, Knight, DA
JournalAm J Respir Cell Mol Biol
Date Published2010 Dec
KeywordsActins, Adolescent, Adult, Aged, Bronchi, Child, Preschool, Demography, Dipeptides, Female, Fibroblasts, Gene Expression Profiling, Gene Expression Regulation, Humans, Male, Matrix Metalloproteinase 2, Matrix Metalloproteinase 9, Matrix Metalloproteinase Inhibitors, Protein-Serine-Threonine Kinases, Receptors, Transforming Growth Factor beta, RNA, Messenger, Signal Transduction, Smad3 Protein, Smad7 Protein, Transforming Growth Factor beta1, Young Adult

Given the contribution various fibroblast subsets make to wound healing and tissue remodeling, the concept of lung fibroblast heterogeneity is of great interest. However, the mechanisms contributing to this heterogeneity are unknown. To this aim, we compared molecular and biophysical characteristics of fibroblasts concurrently isolated from normal human proximal bronchi (B-FBR) and distal lung parenchyma (P-FBR). Using quantitative RT-PCR, spontaneous expression of more than 30 genes related to repair and remodeling was analyzed. All P-FBR lines demonstrated significantly increased basal α-smooth muscle actin (α-SMA) mRNA and protein expression levels when compared with donor-matched B-FBR. These differences were not associated with sex, age, or disease history of lung tissue donors. In contrast to B-FBR, P-FBR displayed enhanced transforming growth factor (TGF)-β/Smad signaling at baseline, and inhibition of either ALK-5 or neutralization of endogenously produced and activated TGF-β substantially decreased basal α-SMA protein in P-FBR. Both B-FBR and P-FBR up-regulated α-SMA after stimulation with TGF-β1, and basal expression levels of TGF-β1, TGF-βRI, and TGF-βRII were not significantly different between fibroblast pairs. Blockade of metalloproteinase-dependent activation of endogenous TGF-β did not significantly modify α-SMA expression in P-FBR. However, resistance to mechanical tension of these cells was significantly higher in comparison with B-FBR, and added TGF-β1 significantly increased stiffness of both cell monolayers. Our data suggest that in contrast with human normal bronchial tissue explants, lung parenchyma produces mesenchymal cells with a myofibroblastic phenotype by intrinsic mechanisms of TGF-β activation in feed-forward manner. These results also offer a new insight into mechanisms of human fibroblast heterogeneity and their function in the airway and lung tissue repair and remodeling.

Alternate JournalAm. J. Respir. Cell Mol. Biol.
PubMed ID20061511
Grant List / / Canadian Institutes of Health Research / Canada