Extracellular matrix deposition by primary human lung fibroblasts in response to TGF-beta 1 and TGF-beta 3

Increased collagen and extracellular matrix (ECM) deposition within the lun g is a characteristic feature of lung fibrosis. Transforming growth factor (TGF)-beta isoforms play a pivotal role in the production of collagen and E CM. In this study, we investigated the effects of TGF-beta 1 and TGF-beta 3 on the main processes controlling ECM deposition using primary human lung fibroblasts. We analyzed 1) collagen metabolism by [H-3]proline incorporati on, 2) matrix metalloproteinase (MMP) expression by substrate gel zymograph y, and 3) tissue inhibitor of metalloproteinases (TIMP) expression by Weste rn blot analysis. TGF-beta 1 and TGF-beta 3 increased the percentage of sec reted collagens in supernatants of primary fibroblasts from 8.0 +/- 1.2 (co ntrol) to 23.6 +/- 4.6 and 22.3 +/- 1.3%, respectively. The collagen percen tage in deposited ECM was increased from 5.8 +/- 0.3 (control) to 9.0 +/- 0 .5 and 8.8 +/- 0.5% by TGF-beta 1 and TGF-beta 3, respectively. Secretion o f MMP-1 (interstitial collagenase) by fibroblasts was reduced by both TGF-b eta isoforms, whereas secretion of MMP-2 (gelatinase A) was unaffected by e ither of the two isoforms. Both TGF-beta isoforms increased TIMP-1 protein expression, whereas TIMP-2 protein was decreased. We thus conclude that TGF -beta 1 and TGF-beta 3 are equally potent in increasing ECM deposition. The ir fibrotic effect in lung fibroblasts results from 1) an increase in the s ecretion and deposition of total ECM and collagens, 2) a decrease in MMP-1 secretion, and 3) an increase of TIMP-1 expression.