Fu Qiang Wen

Matrix metalloproteinase-9 activates TGF-β and stimulates fibroblast contraction of collagen gels

Matrix metalloproteinase-9 (MMP-9) is a matrix-degrading enzyme implicated in many biological processes, including inflammation. It is produced by many cells, including fibroblasts. When cultured in three-dimensional (3D) collagen gels, fibroblasts contract the surrounding matrix, a function that is thought to model the contraction that characterizes both normal wound repair and fibrosis. The current study was designed to evaluate the role of endogenously produced MMP-9 in fibroblast contraction of 3D collagen gels. Fibroblasts from mice lacking expression of MMP-9 and human lung fibroblasts (HFL-1) transfected with MMP-9 small-interfering RNA (siRNA) were used. Fibroblasts were cast into type I collagen gels and floated in culture medium with or without transforming growth factor (TGF)-β1 for 5 days. Gel size was determined daily using an image analysis system. Gels made from MMP-9 siRNA-treated human fibroblasts contracted less than control fibroblasts, as did fibroblasts incubated with a nonspecific MMP inhibitor. Similarly, fibroblasts cultured from MMP-9-deficient mice contracted gels less than did fibroblasts from control mice. Transfection of the MMP-9-deficient murine fibroblasts with a vector expressing murine MMP-9 restored contractile activity to MMP-9-deficient fibroblasts. Inhibition of MMP-9 reduced active TGF-β1 and reduced several TGF-β1-driven responses, including activity of a Smad3 reporter gene and production of fibronectin. Because TGF-β1 also drives fibroblast gel contraction, this suggests the mechanism for MMP-9 regulation of contraction is through the generation of active TGF-β1. This study provides direct evidence that endogenously produced MMP-9 has a role in regulation of tissue contraction of 3D collagen gels mediated by fibroblasts.

Glucocorticoids Modulate TGF-β Production by Human Fetal Lung Fibroblasts

TGF-β is thought to play a central role in pulmonary fibrosis inducing fibroblast differentiation and extracellular matrix synthesis. In human lung fibroblasts, it is still unclear how various TGF-β isoforms affect TGF-β production and whether glucocorticoids, commonly used agents to treat fibrotic lung disease, modulate these processes. To this end, human fetal lung fibroblasts (HFLF) were cultured with various concentrations of glucocorticoids (budesonide, dexamethasone or hydrocortisone) with and without TGF-β1, -β2, or -β3. Post-culture media were collected for ELISA assays of TGF-β1, -β2, and -β3 . TGF-β mRNA was assessed by real time RT-PCR. Smad 2, 3, and 4 and AP-1 complex (c-fos and c-Jun) cellular localization were evaluated by immunostaining. TFG-β2 and -β3 stimulated TGF-β1 production significantly (p < 0.01 relative to control). TGF-β1 stimulated TGF-β2 production (p < 0.01 relative to control). TGF-β3 was undetectable. Glucocorticoids significantly inhibited TGF-β1 and TGF-β2 production and reduced expression of the up-regulated TGF-β1 and TGF-β2 mRNA induced by exogenous TGF-β1, -β2, or -β3 (p < 0.01 for each) but had no effect on Smads. Although c-jun-related nuclear staining was not intensified in TGF-β-stimulated cells, it was reduced by glucocorticoids. Thus, TGF-β isoforms may stimulate production of various TGF-β isoforms in the lung. Glucocorticoids then may block TGF-β production by modulating mRNA levels and c-Jun.

Cigarette Smoke Stimulates MMP‐1 Production by Human Lung Fibroblasts Through the ERK1/2 Pathway

An imbalance between proteases and anti‐proteases is believed to play an important role in the pathogenesis of emphysema. In this study, we explored the hypothesis that cigarette smoke can alter tissue structure through an effect on the release of matrix metalloproteinase‐1 (MMP‐1) and type I tissue inhibitor of metalloproteinases (TIMP‐1). Cigarette smoke extract (CSE) significantly stimulated pro‐MMP‐1 production (determined by ELISA and immunoblots) and mRNA expression (by real‐time RT‐PCR) by human fetal lung fibroblasts (HFL‐1) in a concentration‐dependent manner (2.5–10%). High concentrations of CSE (10%) could potentially activate the latent form of MMP‐1 as the high molecular weight (52 kDa) form was converted into a low molecular weight (42 kDa) form consistent with active MMP‐1. TIMP‐1 production, however, was not significantly altered by the concentrations of CSE tested. After 30 min exposure, CSE significantly induced ERK1/2 phosphorylation, which then gradually decreased from 90 minutes to 3 hours. PD98059, a specific inhibitor of ERK‐MAPK, significantly blocked the CSE effect on ERK1/2 phosphorylation. Furthermore, PD98059 significantly inhibited the CSE effect on MMP‐1 production and mRNA expression by fibroblasts. These results suggest that cigarette smoke stimulates production and likely activates MMP‐1 through activating ERK1/2 signal transduction pathway. By inducing MMP‐1, cigarette smoke may result in excess tissue destruction and contribute to the development of emphysema.

Glucocorticoids and TGF-β1 Synergize in Augmenting Fibroblast Mediated Contraction of Collagen Gels

TGF-β plays a central role in the initiation and progression of pulmonary fibrosis. Glucocorticoids are frequently used to treat fibrotic diseases, but beneficial effects are often modest. Both TGF-β and glucocorticoids have been reported to increase fibroblast contraction of native collagen gels, a model of fibrotic tissue remodeling. Therefore, we sought to determine how glucocorticoids interact with TGF-β in this system. In this study, human fetal lung fibroblasts (HFL-1) were pretreated with or without TGF-β for 72 h before they were cast into type I collagen gels. Various concentrations of glucocorticoids (budesonide or hydrocortisone) were added at the time of casting. Gel size was then monitored at different times after gel release. The surrounding media were collected for the assay of prostaglandin E2 (PGE2) and the cell lysates were analyzed for cyclooxygenase (COX) expression by immunoblot. Glucocorticoids alone significantly enhanced fibroblast-mediated contraction of collagen gels (P < 0.01) and dose-dependently inhibited PGE2 release by HFL-1 fibroblasts. TGF-β significantly augmented gel contraction but also induced a 30% increase in PGE2 release and increased the expression of COX-1. Glucocorticoids inhibited TGF-β1 induced-PGE2 release, and enhanced TGF-β augmented gel contraction without significantly affecting TGF-β augmented COX-1 expression. Indomethacin, a COX inhibitor, increased TGF-β augmented gel contraction but had no further effect when added together with glucocorticoids. Thus, glucocorticoids can synergize with TGF-β in augmenting fibroblast mediated collagen gel contraction through the inhibition of PGE2 production. Such interactions between glucocorticoids and TGF-β may account, in part, for the lack of response of fibrotic diseases to glucocorticoids.

Glucocorticoids Modulate TGF-β Production

TGF-β is thought to play a central role in pulmonary fibrosis inducing fibroblast differentiation and extracellular matrix synthesis. In human lung fibroblasts, it is still unclear how various TGB-β isoforms affect TGF-β production and whether glucocorticoids, commonly used agents to treat fibrotic lung disease, modulate these processes. To this end, human fetal lung fibroblasts (HFL-1) were cultured with various concentrations of glucocorticoids (budesonide, dexamethasone or hydrocortisone) with and without TFG-β1, -β2, and -β3. TGF-β mRNA was assessed by real time RT-PCR. Smad 2, 3, and 4 and AP-1 complex (c-fos and c-Jun) cellular localization were evaluated by immunostaining. TGF-β2 and -β3 stimulated TGF-β1 production significantly (p < 0.01 relative to control). TGF-β1 stimulated TGF-β2 production (p < 0.01 relative to control). TGF-β3 was undetectable. Glucocorticoids significantly inhibited TGF-β1 and -β2 production and reduced expression of the upregulated TGF-β1 and -β2 mRNA induced by exogenous TGF-β1, -β2 or -β3 (p < 0.01 for each) but had no effect on Smads. Although c-jun-related nuclear staining was not intensified in TGF-β-stimulated cells, it was reduced by glucocorticoids. Thus, TGF-β isoforms may stimulate production of various TGF-β isoforms in the lung. Glucocorticoids then may block TGF-β production by modulating mRNA levels and c-Jun.

Fibroblasts and monocyte macrophages contract and degrade three-dimensional collagen gels in extended co-culture

BackgroundInflammatory cells are believed to play a prominent role during tissue repair and remodeling. Since repair processes develop and mature over extended time frames, the present study was designed to evaluate the effect of monocytes and fibroblasts in prolonged culture in three-dimensional collagen gels.MethodsBlood monocytes from healthy donors and human fetal lung fibroblasts were cast into type I collagen gels and maintained in floating cultures for three weeks.ResultsFibroblast-mediated gel contraction was initially inhibited by the presence of monocytes (P < 0.01). However, with extended co-culture, contraction of the collagen gels was greatly augmented (P < 0.01). In addition, with extended co-culture, degradation of collagen in the gels occurred. The addition of neutrophil elastase to the medium augmented both contraction and degradation (P < 0.01). Prostaglandin E2 production was significantly increased by co-culture and its presence attenuated collagen degradation.ConclusionThe current study, therefore, demonstrates that interaction between monocytes and fibroblasts can contract and degrade extracellular matrix in extended culture.

IL-4 and IL-13 Induce Chemotaxis of Human Foreskin Fibroblasts, but Not Human Fetal Lung Fibroblasts

Through shared receptors, IL-4 and IL-13 have been suggested to regulate not only inflammatory cells, but also to play a role in stimulating fibroblasts during fibrotic processes. Previous studies have shown that IL-4 is a chemoattractant for foreskin fibroblasts. The current study was designed to determine the effect of IL-4 and IL-13 on the migration of two types of fibroblasts: foreskin and human fetal lung fibroblasts (HFL-1). Using the Boyden blindwell chamber method, human foreskin or fetal lung fibroblasts (both 106/mL) were placed in upper wells with various concentrations of IL-4 or IL-13 in the lower wells as chemoattractants. Both IL-4 (1 pg/mL) and IL-13 (100 pg/mL) induced foreskin fibroblast chemotaxis, up to 50 ± 8 and 24 ± 7 cells/5 high-power fields, respectively (both p< 0.05). In contrast, neither cytokine induced migration of the lung fibroblasts although both type of cells express IL-4 receptor and IL-13 α1 receptor. These results suggest that fibroblasts are heterogeneous with regard to their ability to respond to cytokine-driven chemotaxis. Therefore, the role of specific cytokines in mediating fibrotic responses might vary depending on local mesenchymal cell responses.