title: Extracellular matrix deposition by primary human lung fibroblasts in response to TGF-beta1 and TGF-beta3.
abstract: Increased collagen and extracellular matrix (ECM) deposition within the lung is a characteristic feature of lung fibrosis. Transforming growth factor (TGF)-beta isoforms play a pivotal role in the production of collagen and ECM. In this study, we investigated the effects of TGF-beta1 and TGF-beta3 on the main processes controlling ECM deposition using primary human lung fibroblasts. We analyzed 1) collagen metabolism by [3H]proline incorporation, 2) matrix metalloproteinase (MMP) expression by substrate gel zymography, and 3) tissue inhibitor of metalloproteinases (TIMP) expression by Western blot analysis. TGF-beta1 and TGF-beta3 increased the percentage of secreted collagens in supernatants of primary fibroblasts from 8.0 +/- 1.2 (control) to 23.6 +/- 4.6 and 22.3 +/- 1.3%, respectively. The collagen percentage in deposited ECM was increased from 5.8 +/- 0.3 (control) to 9.0 +/- 0.5 and 8.8 +/- 0.5% by TGF-beta1 and TGF-beta3, respectively. Secretion of MMP-1 (interstitial collagenase) by fibroblasts was reduced by both TGF-beta isoforms, whereas secretion of MMP-2 (gelatinase A) was unaffected by either of the two isoforms. Both TGF-beta isoforms increased TIMP-1 protein expression, whereas TIMP-2 protein was decreased. We thus conclude that TGF-beta1 and TGF-beta3 are equally potent in increasing ECM deposition. Their fibrotic effect in lung fibroblasts results from 1) an increase in the secretion and deposition of total ECM and collagens, 2) a decrease in MMP-1 secretion, and 3) an increase of TIMP-1 expression.
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D017364:Collagenases / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism* / Q000648:ultrastructure*; D018093:Gelatinases / Q000378:metabolism; D006801:Humans; D020781:Matrix Metalloproteinase 1; D020778:Matrix Metalloproteinase 2; D008666:Metalloendopeptidases / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000032:analysis; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000032:analysis; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014316:Tritium