Biomedical subjects

Xiangde Liu

Publications and source records attributed to Xiangde Liu.

At least 19 recordsLinked to original sources

PubMed2007

Prostaglandin E(2) protects human lung fibroblasts from cigarette smoke extract-induced apoptosis via EP(2) receptor activation.

Prostaglandin E(2) (PGE(2)) has been shown to have a strong cytoprotective effect, inhibiting apoptosis. In the present study, we evaluated whether PGE(2) has a protective effect on cigarette smoke extract (CSE)-induced apoptosis in human lung fibroblasts. Apoptosis was assessed by various methods, including DNA content analysis. CSE (15%-20%) led to apoptosis and induced imbalance in favor of pro- over anti-apoptotic protein expression and activated caspases. PGE(2) blocked CSE-induced apoptosis and modulated the balance of pro- and anti-apoptotic proteins and decreased the activation of caspases. This anti-apoptotic effect was mediated via EP(2) receptor activation as the EP(2) agonist butaprost mimicked PGE(2) activity and siRNA for the EP(2) receptor blocked it. An adenylyl cyclase inhibitor was found to abolish the PGE(2)-mediated cytoprotective effect. Correspondingly, c-AMP analogs blocked CSE-induced apoptosis. Consistently, the protein kinase A (PKA) inhibitor KT-5720 abolished PGE(2)-mediated protection. PGE(2) and butaprost phosphorylated Bad and KT-5720 blocked phosphorylation. These results suggest that PGE(2) inhibits CSE-induced apoptosis via EP(2) receptor activation and activation of PKA, which leads to an alteration in the balance between pro- and anti-apoptotic factors. Through such a mechanism, PGE(2) may alter survival of cells in the smoke-exposed lungs, thus affecting the pathogenesis of cigarette smoke-induced disease.

Adenylyl Cyclase Inhibitors↗

PubMed2006

STAT3 activation inhibits human bronchial epithelial cell apoptosis in response to cigarette smoke exposure.

We have previously reported that cigarette smoke can induce DNA damage in human lung cells without leading to apoptosis or necrosis. In this study, we report that STAT3 is required for the survival of human bronchial epithelial cells (HBECs) following cigarette smoke-induced DNA damage. Cigarette smoke extract (CSE) exposure increases STAT3 phosphorylation (Tyr 705) and DNA binding activity in HBECs. CSE also stimulates IL-6 release and mRNA expression. Anti-IL-6 neutralizing antibody partially blocks STAT3 activation and renders the cells sensitive to CSE-induced DNA damage. Suppression of STAT3 by siRNA results in severe DNA damage and cell death in response to CSE exposure. These findings suggest that STAT3 mediates HBEC survival in response to CSE-induced DNA damage, at least in part, through the IL-6/STAT3 signaling pathway.

Apoptosis↗

PubMed2006

Thrombin and TNF-alpha/IL-1beta synergistically induce fibroblast-mediated collagen gel degradation.

Degradation of preexisting and newly synthesized extracellular matrix is thought to play an important role in tissue remodeling. The current study evaluated whether thrombin and TNF-alpha/IL-1beta could collaboratively induce collagen degradation by human fetal lung fibroblasts (HFL-1) and adult bronchial fibroblasts cultured in three-dimensional collagen gels. TNF-alpha/IL-1beta alone induced production of matrix metalloproteinases (MMPs)-1, -3, and -9, which were released in latent form. With the addition of thrombin, the latent MMPs were converted into active forms and this resulted in collagen gel degradation. Part of the activation of MMPs by thrombin resulted from direct activation of MMP-1, MMP-2, MMP-3, and MMP-9 in the absence of cells. In addition, tissue inhibitor of metalloproteinase-1 production was inhibited by the combination of thrombin and TNF-alpha/IL-1beta. These results suggest that thrombin and TNF-alpha/IL-1beta synergize to induce degradation of three-dimensional collagen gels through increasing the production and activation of MMPs, and that this effect is mediated through both direct activation of MMPs by thrombin and indirectly by thrombin activation of fibroblasts. Through such mechanisms, thrombin could contribute to many chronic lung disorders characterized by tissue remodeling.

Cell Line↗

PubMed2006

Transforming growth factor-beta receptor type 1 (TGFbetaRI) kinase activity but not p38 activation is required for TGFbetaRI-induced myofibroblast differentiation and profibrotic gene expression.

Transforming growth factor-beta (TGFbeta) is a major mediator of normal wound healing and of pathological conditions involving fibrosis, such as idiopathic pulmonary fibrosis. TGFbeta also stimulates the differentiation of myofibroblasts, a hallmark of fibrotic diseases. In this study, we examined the underlying processes of TGFbetaRI kinase activity in myofibroblast conversion of human lung fibroblasts using specific inhibitors of TGFbetaRI (SD-208) and p38 mitogen-activated kinase (SD-282). We demonstrated that SD-208, but not SD-282, inhibited TGFbeta-induced SMAD signaling, myofibroblast transformation, and collagen gel contraction. Furthermore, we extended our findings to a rat bleomycin-induced lung fibrosis model, demonstrating a significant decrease in the number of myofibroblasts at fibroblastic foci in animals treated with SD-208 but not those treated with SD-282. SD-208 also reduced collagen deposition in this in vivo model. Microarray analysis of human lung fibroblasts identified molecular fingerprints of these processes and showed that SD-208 had global effects on reversing TGFbeta-induced genes involved in fibrosis, inflammation, cell proliferation, cytoskeletal organization, and apoptosis. These studies also revealed that although the p38 pathway may not be needed for appearance or disappearance of the myofibroblast, it can mediate a subset of inflammatory and fibrogenic events of the myofibroblast during the process of tissue repair and fibrosis. Our findings suggest that inhibitors such as SD-208 may be therapeutically useful in human interstitial lung diseases and pulmonary fibrosis.

Activin Receptors, Type I↗

PubMed2006

Reactive nitrogen species augment fibroblast-mediated collagen gel contraction, mediator production, and chemotaxis.

Reactive nitrogen species (RNS) such as peroxynitrite cause cellular injury and tissue inflammation. Excessive production of nitrotyrosine, which is a footprint of RNS, has been observed in the airways of patients with asthma and chronic obstructive pulmonary disease, disorders characterized by tissue remodeling. The aim of this study was to evaluate whether RNS can affect tissue remodeling through direct effects on fibroblasts, and to determine if these effects depend on production of transforming growth factor-beta (TGF-beta). To accomplish this, human fetal lung fibroblasts (HFL-1) were used to assess fibroblast-mediated contraction of floating gels and chemotaxis toward fibronectin. In addition, the ability of fibroblasts to release TGF-beta1, fibronectin, and vascular endothelial growth factor (VEGF) was assessed by enzyme-linked immunosorbent assay. Authentic peroxynitrite significantly augmented gel contraction (P < 0.01) and chemotaxis (P < 0.01) compared with control in a concentration-dependent manner. Similarly, the peroxynitrite donor 3-morpholynosidenonimine hydrochloride (SIN-1) also augmented gel contraction (P < 0.01). RNS also significantly increased TGF-beta1 (P < 0.01), fibronectin (P < 0.01), and VEGF (P < 0.01) release into the media in both 3D gel and monolayer culture. Anti-TGF-beta antibody reversed RNS-augmented gel contraction (P < 0.01) and mediator production (P < 0.01). Anti-TGF-beta antibody also partially, but significantly, reversed RNS-augmented chemotaxis toward fibronectin (P < 0.01). Finally, peroxynitrite enhanced expression of alpha5beta1 integrin, which is a receptor for fibronectin (P < 0.01), and neutralizing anti-TGF-beta antibody suppressed peroxynitrite-augmented alpha5beta1 expression (P < 0.01). These results suggest that RNS can affect the tissue repair process by modulating TGF-beta1.

Animals↗

PubMed2006

New strategy to prevent ascending cholangitis in larger choledochoduodenal fistula.

BACKGROUND: Choledochoduodenal fistula (CDF) is a complication of common bile duct stones or cholangitis in Asia. It is unclear as to which type of the fistula needs surgical treatment. METHODS: To determine whether the sizes of CDF imply different clinical presentations and treatments, we reviewed 50 patients with CDF and their treatments during a recent 14-year period. For treatments of CDF, we applied the conventional methods, including removal of stone and complete decompression of biliary obstruction to treat the original bile lesions. In addition, according to the sizes of fistula and the frequencies of ascending cholangitis, we proposed the following strategies for fistula treatments: (i) for fistula orifices larger than 1 cm, a transection of common bile duct was applied to prevent the reflux of duodenal juice; (ii) for fistula orifices between 0.5 and 1.0 cm, an effective biliary drainage was applied; and (iii) for fistula orifices less than 0.5 cm, non-surgical treatments were applied. RESULTS: We found that hepatic biliary duct stones and hepatic biliary duct strictures were associated with more severe cholangitis (P = 0.037 and P = 0.009, respectively), but not with the episodes of cholangitis (P = 0.654 and P = 0.664, respectively). In contrast, the sizes of fistula >1 cm were associated with more frequent episodes of cholangitis (r = 0.774; P < 0.001). CONCLUSION: The larger fistula increases frequency of cholangitis episodes and needs surgical treatment for fistula itself.

Bile Duct Diseases↗

PubMed2005

TGF-beta1 and serum both stimulate contraction but differentially affect apoptosis in 3D collagen gels.

Apoptosis of fibroblasts may be key for the removal of cells following repair processes. Contraction of three-dimensional collagen gels is a model of wound healing and remodeling. Here two potent inducers of contraction, TGF-beta1 and fetal calf serum (FCS) were evaluated for their effect on fibroblast apoptosis in contracting collagen gels. Human fetal lung fibroblasts were cultured in floating type I collagen gels, exposed to TGF-beta1 or FCS, and allowed to contract for 5 days. Apoptosis was evaluated using TUNEL and confirmed by DNA content profiling. Both TGF-beta1 and serum significantly augmented collagen gel contraction. TGF-beta1 also increased apoptosis assessed by TUNEL positivity and DNA content analysis. In contrast, serum did not affect apoptosis. TGF-beta1 induction of apoptosis was associated with augmented expression of Bax, a pro-apoptotic member of the Bax/Bcl-2 family, inhibition of Bcl-2, an anti-apoptotic member of the same family, and inhibition of both cIAP-1 and XIAP, two inhibitors of the caspase cascade. Serum was associated with an increase in cIAP-1 and Bcl-2, anti-apoptotic proteins. Interestingly, serum was also associated with an apparent increase in Bax, a pro-apoptotic protein. Blockade of Smad3 with either siRNA or by using murine fibroblasts deficient in Smad3 resulted in a lack of TGF-beta induction of augmented contraction and apoptosis. Contraction induced by different factors, therefore, may be differentially associated with apoptosis, which may be related to the persistence or resolution of the fibroblasts that accumulate following injury.

Apoptosis↗

PubMed2005

Smad3 mediates TGF-beta1-induced collagen gel contraction by human lung fibroblasts.

Transforming growth factor-beta1 (TGF-beta1) is a key mediator in tissue repair and fibrosis. Using small interference RNA (siRNA), the role of Smad2 and Smad3 in TGF-beta stimulation of human lung fibroblast contraction of collagenous matrix and induction of alpha-SMA and the role of alpha-SMA in contraction were assessed. HFL-1 cells were transfected with Smad2, Smad3 or control-siRNA, and cultured in floating Type I collagen gels +/- -TGF-beta1. TGF-beta1 augmented gel contraction in Smad2-siRNA- and control-siRNA-treated cells, but had no effect in Smad3-siRNA-treated cells. Similarly, TGF-beta1 upregulated alpha-SMA in Smad2-siRNA- and control-siRNA-treated cells, but had no effect on Smad3-siRNA-treated cells. Alpha-SMA-siRNA-treated cells did not contact the collagen gels with or without TGF-beta1, suggesting alpha-SMA is required for gel contraction. Thus, Smad3 mediates TGF-beta1-induced contraction and alpha-SMA induction in human lung fibroblasts. Smad3, therefore, could be a target for blocking contraction of human fibrotic tissue induced by TGF-beta1.

Actins↗

PubMed2005

Cigarette smoke extract induces DNA damage but not apoptosis in human bronchial epithelial cells.

Whether DNA damage caused by cigarette smoke leads to repair or apoptosis has not been fully elucidated. The current study demonstrates that cigarette smoke induces single-strand DNA damage in human bronchial epithelial cells. Cigarette smoke also stimulated caspase 3 precursors as well as intact poly (ADP-ribose) polymerase (PARP) production, but did not activate caspase 3 or cleave PARP, while the alkaloid camptothecin did so. Neither apoptosis nor necrosis was induced by cigarette smoke when the insult was removed within a designated time period. In contrast, DNA damage following cigarette smoke exposure was repaired as evidenced by decreasing terminal dUTP-biotin nick-end labeling positivity. The PARP inhibitor, 3-aminobenzamide blocked this repair. Furthermore, cells subjected to DNA damage were able to survive and proliferate clonogenically when changed to smoke-free conditions. These results suggest that cigarette smoke-induced DNA damage in bronchial epithelial cells is not necessarily lethal, and that PARP functions in the repair process. Our data also suggest that the potency of cigarettes as a carcinogen may result from their ability to induce DNA damage while failing to trigger the apoptotic progression permitting survival of cells harboring potentially oncogenic mutations.

Apoptosis↗

PubMed2005

Smad3 mediates TGF-beta1 induction of VEGF production in lung fibroblasts.

Transforming growth factor-beta1 (TGF-beta1) is a key factor in a variety of physiological and pathological processes. Vascular endothelial growth factor (VEGF) is a key angiogenic factor, and vascular change is one of the features of airway remodeling. We examined the effect of TGF-beta1 on VEGF production by fibroblasts from mice lacking expression of Smad2 or Smad3 as well as human lung fibroblasts treated with or without Smad2 or Smad3 siRNA. TGF-beta1 stimulated VEGF production by fibroblasts from Smad2 deficient animals and wildtype animals. In contrast, TGF-beta1 did not affect VEGF production by fibroblasts from Samd3 deficient mice. Similarly, TGF-beta1 failed to stimulate VEGF production by HFL-1 cells treated with Samd3 siRNA but significantly increased VEGF production by the cells treated with Smad2 siRNA. These result suggest that TGF-beta1 stimulation of VEGF production by fibroblasts is regulated by Smad3 but not by Smad2 signaling.

Animals↗

PubMed2004

Cells derived from the circulation contribute to the repair of lung injury.

Bone marrow (stem/progenitor) cells have been shown to "differentiate" into cells in multiple tissues, including lung. A low number of hematopoietic stem/progenitor cells also circulate in peripheral blood. The physiologic roles of these cells are still uncertain. This study was designed to test, using parabiotic mice that were joined surgically, whether stem/progenitor cells in blood contributed to the regeneration of lung after injury. Parabiotic mice were generated surgically by joining green fluorescent protein transgenic mice and wild-type littermates. These mice developed a common circulation (approximately 50% green cells in blood) by 2 weeks after surgery. The wild-type mouse was either uninjured or lethally irradiated or received intratracheal elastase or the combination of radiation with intratracheal elastase injection. Radiation or the combination of radiation with elastase significantly increased the proportion of bright green cells in the lungs of the wild-type mice. Morphologically, interstitial monocytes/macrophages, subepithelial fibroblast-like interstitial cells, and additionally type I alveolar epithelial cells immunostained for green fluorescent protein in wild-type mice. Approximately 5 to 20% of lung fibroblasts primary cultured from injured wild-type mice were green fluorescent protein expressing cells, indicating their blood derivation. This study demonstrates that stem/progenitor cells in blood contribute to the repair of lung injury in irradiated mice.

Animals↗

PubMed2004

Reversible cigarette smoke extract-induced DNA damage in human lung fibroblasts.

Cigarette smoke contains thousands of chemicals, many of which may contribute to cytotoxicity and carcinogenesis. Using assays detecting DNA strand breaks (terminal transferase dUTP nick end labeling [TUNEL]) and DNA content (flow cytometry), we evaluated the genotoxic effect of cigarette smoke extract (CSE) on human fetal lung fibroblasts (HFL-1) cultured in three-dimensional collagen gels as well as in monolayer culture. When HFL-1 cells were exposed to CSE, DNA strand breaks were detected in most, as determined by TUNEL. This effect was dependent on CSE concentration, duration of CSE exposure, and the density of HFL-1 cells cast into the collagen gels. Buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, significantly increased DNA damage induced by 1% CSE, and N-acetylcysteine, a glutathione precursor, blocked 5% CSE from inducing DNA damage. After CSE exposure, most cells were TUNEL-positive, but DNA quantification revealed no hypodiploid cells, indicating that apoptosis was not occurring during the CSE exposure. CSE-induced DNA damage was reversible, and cells proliferated when CSE was removed after 24 h exposure. These results demonstrate that cigarette smoke can induce DNA damage in HFL-1 cells cultured in both three-dimensional collagen gels and monolayer cultures, and that oxidants likely play a role in this damage. Moreover, this DNA damage is reversible, with cells surviving and TUNEL positivity reversing when CSE is removed within 24 h.

Acetylcysteine↗

PubMed2004

Interferon-gamma inhibits transforming growth factor-beta production in human airway epithelial cells by targeting Smads.

Because interferon (IFN)-gamma may attenuate pulmonary fibrosis, we hypothesized that IFN-gamma may regulate transforming growth factor (TGF)-beta production by airway epithelial cells. Human bronchial epithelial cells (HBECs) were incubated with IFN-gamma +/- TGF-beta1, -beta3, or interleukin (IL)-1beta, platelet-derived growth factor (PDGF), epidermal growth factor, and IL-4. TGF-beta2 protein was measured by enzyme-linked immunosorbent assay and mRNA expression for TGF-beta2, Smad 2, 3, 4, and 7 was evaluated by real-time reverse transcriptase-polymerase chain reaction. Localization of Smads 2, 3, 4, and 7 was evaluated by immunostaining. Exogenous TGF-beta1 and 3, IL-1beta, PDGF, and IL-4 enhanced TGF-beta2 release by HBECs (P < 0.01). IFN-gamma reduced basal and TGF-beta or IL-4-augmented TGF-beta2 release, but had little effect on IL-1beta- or PDGF-augmented TGF-beta2 release. IFN-gamma stimulated Smad 7 protein and mRNA expression. Smad 7-specific siRNA decreased Smad 7 protein expression both in control and IFN-gamma-treated cells. The inhibitory effect of IFN-gamma on TGF-beta2 production was abrogated when the HBECs were treated with Smad 7 siRNA. These results suggest that IFN-gamma down regulates TGF-beta2 production by HBECs by regulating Smad 7. Through this mechanism, IFN-gamma may play an important role in tissue remodeling.

Cells, Cultured↗

PubMed2004

Cytokines modulate cilomilast response in lung fibroblasts.

Fibroblasts, as a major source of extracellular interstitial connective tissue matrix, play an important role in wound healing and the development of fibrosis. The phosphodiesterase (PDE) 4 inhibitor cilomilast inhibits fibroblast chemotaxis and fibroblast-mediated gel contraction. Using the Boyden blindwell chamber chemotaxis assay and the type I collagen gel contraction model, this study investigated whether specific cytokines modulate cilomilast's inhibitory effect through regulation of endogenous PGE(2) production. Human recombinant IL-1beta stimulated PGE(2) production and shifted the cilomilast concentration-dependence curve to the left in both assay systems, indicating increased sensitivity to cilomilast. In contrast, human recombinant IL-4 inhibited PGE(2) production and shifted the cilomilast concentration-dependence curve to the right in both systems. In summary, the inhibitory effect of cilomilast on fibroblast migration and collagen gel contraction is modulated by IL-1beta and IL-4 through regulation of PGE(2) production.

Bronchodilator Agents↗

PubMed2004

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 10(6)/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-13alpha1 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.

Cell Movement↗

PubMed2004

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.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed2003

Cigarette smoke extract inhibits chemotaxis and collagen gel contraction mediated by human bone marrow osteoprogenitor cells and osteoblast-like cells.

Cell migration and matrix remodeling are key events in tissue repair and restructuring. Osteoblasts are responsible for the production of new bone matrix during bone remodeling. The activity of these cells can be modulated by a number of factors. The current study evaluated the hypothesis that cigarette smoke extract can alter repair and remodeling responses of human osteoprogenitor cells and osteoblast-like cells and, therefore, could explain one mechanism by which cigarette smoking leads to osteoporosis. Human osteoprogenitor cells were isolated from normal human bone marrow and maintained in culture under either control conditions or conditions that induced differentiation into osteoblast-like cells. Both cell types migrated toward fibronectin and PDGF-BB as chemoattractants. Neither responded to TGF-beta1. The osteoprogenitor cells were more active in their chemotactic response. The chemotactic response of both cell types was inhibited by cigarette smoke extract in a concentration-dependent manner. Both cell types, when cultured in three-dimensional native collagen gels maintained in floating culture, induced contraction of their surrounding matrices. Contraction was augmented by serum, PDGF-BB, and TGF-beta1. Osteoprogenitor cells were less active in inducing contraction than were osteoblast-like cells. Contraction of both cell types was inhibited by cigarette smoke extract. Cigarette smoke extract also inhibited the production of fibronectin by both cell types maintained in three-dimensional culture. Addition of exogenous fibronectin partially restored the ability of the cells to contract three-dimensional collagen gels. The current study demonstrates that cigarette smoke can interfere with the ability of bone cells to participate in repair and remodeling events. Such an effect may be one mechanism leading to the development of osteoporosis.

Becaplermin↗

PubMed2003

Smad3 mediates the TGF-beta-induced contraction of type I collagen gels by mouse embryo fibroblasts.

TGF-beta signals through TGF-beta receptors and Smad proteins. TGF-beta also augments fibroblast-mediated collagen gel contraction, an in vitro model of connective tissue remodeling. To investigate the importance of Smad2 or Smad3 in this augmentation process, embryo-derived fibroblasts from mice lacking expression of Smad2 or Smad3 genes were cast into native type I collagen gels. Fibroblast-populated gels were then released into 0.2% FCS-DMEM alone or with recombinant human TGF-beta1, beta2, beta3, or recombinant rat PDGF-BB. Gel contraction was determined using an image analyzer. All three isoforms of TGF-beta significantly augmented contraction of collagen gels mediated by fibroblasts with genotypes of Smad2 knockout (S2KO), Smad2 wildtype (S2WT), and Smad3 wildtype (S3WT), but not Smad3 knockout (S3KO) mice. PDGF-BB augmented collagen gel contraction by all fibroblast types. These results suggest that expression of Smad3 but not Smad2 may be critical in TGF-beta augmentation of fibroblast-mediated collagen gel contraction. Thus, the Smad3 gene could be a target for blocking contraction of fibrotic tissue induced by TGF-beta.

Animals↗