Fibrotic Tissue Remodeling Research Articles

Prostaglandin E 2 Promotes Net Plasminogen Activation in Human Lung Fibroblasts

RATIONALE: Fibrotic tissue remodeling is central to the pathogenesis of both airway remodeling in asthma and parenchymal remodeling in fibrotic interstitial lung disorders. Evidence from both patients and animal models implicates prostaglandin E2 (PGE2) as well as the degree of fibrinolysis, in turn dictated by the balance of urokinase plasminogen activator (uPA) and plasminogen activator inhibitor (PAI-1), as key anti-fibrotic mediators. However, little is known about the cross-talk between these two mediator systems.

Welcome to Fibrogenesis & Tissue Repair

Fibroproliferative diseases affecting different organs and systems constitute the largest burden and challenge of modern medicine. Nearly 45% of all deaths in the developed world are caused by chronic inflammatory and fibrogenic disorders such as cardiovascular disease, pulmonary fibrosis, progressive kidney disease, systemic sclerosis, liver cirrhosis and inflammatory bowel disease. In addition, chronic inflammation and fibrotic tissue remodelling associated with neo-angiogenesis represent key mechanisms leading to the development of cancer, thus accounting for an additional number of deaths. Regardless of the final clinical outcome, all chronic fibrogenic disorders have a major impact on the quality of life of millions of individuals worldwide and represent a major cost for public health. Despite the massive impact of fibroproliferative diseases on human health, there are no approved treatment options that directly target the mechanisms of fibrosis. Since research performed over the past thirty years has made it increasingly clear that fibroproliferative disorders often share common mechanisms [1,2], encouraging communication between scientists working in different subspecialties of experimental or clinical medicine and the pharmaceutical industry will help identify common targets and foster the development of new therapeutic strategies. Accordingly, the main aim of Fibrogenesis & Tissue Repair is to fill the gap in communication which exists between scientists working on fibrogenesis and tissue repair in different disciplines, allowing them to exchange ideas and to work on common targets. Fibrogenesis & Tissue Repair publishes original and high-quality research articles providing novel insights into the mechanisms, diagnosis and treatment of human diseases characterized by chronic wound healing or fibrogenesis and leading to end-stage organ failure. In particular, the journal focuses on the discovery and characterization of the mechanisms of fibrogenesis and tissue repair common to, or specific for, different organ systems. Along these lines, Fibrogenesis & Tissue Repair is divided into five major fibroproliferative disease areas: gastrointestinal and liver, renal, rheumatology and connective tissue, lung, heart and vessels. Particular emphasis is given to those submissions leading to a significant advancement in the fields of genetic predisposition, diagnostic biomarkers and drug discovery. The journal also publishes important advancements in the areas of regenerative medicine, cell therapy and stromal involvement in the genesis of cancer and metastasis. We also solicit reviews in emerging areas of research based on suggestions from members of our Editorial Board [3], whose expertise spans a wide range of disciplines. Online, open-access publication [4] means that all Fibrogenesis & Tissue Repair articles will be available to readers without charge and that movies and animations are only a click away. The benefits of open access are particularly pronounced in a journal such as Fibrogenesis & Tissue Repair that aims to promote the rapid exchange of ideas between different specialities. Manuscripts submitted to Fibrogenesis & Tissue Repair will be reviewed by internationally recognized experts in the fields of fibrogenesis, inflammation, and tissue regeneration, selected in part from our Editorial Board. Reviews will be rapid and the suitability of a manuscript for publication will be assessed solely on criteria of scientific excellence. Upon acceptance, articles will be made immediately available online and deposited in PubMed and PubMed Central. Only once a manuscript is accepted for publication will the authors be required to pay an Article Processing Charge to cover the costs of handling their manuscript [5]. The authors are not charged extra for colour figures and there is no page limit. We sincerely hope that the scientific community involved in the study of fibrogenic diseases and, more broadly, in promoting regenerative medicine will contribute and respond with renewed enthusiasm to this call. The Editors are committed to making this new venture a success, and we hope to receive your contributions in the near future.

Common and unique mechanisms regulate fibrosis in various fibroproliferative diseases

Fibroproliferative diseases, including the pulmonary fibroses, systemic sclerosis, liver cirrhosis, cardiovascular disease, progressive kidney disease, and macular degeneration, are a leading cause of morbidity and mortality and can affect all tissues and organ systems. Fibrotic tissue remodeling can also influence cancer metastasis and accelerate chronic graft rejection in transplant recipients. Nevertheless, despite its enormous impact on human health, there are currently no approved treatments that directly target the mechanism(s) of fibrosis. The primary goals of this Review series on fibrotic diseases are to discuss some of the major fibroproliferative diseases and to identify the common and unique mechanisms of fibrogenesis that might be exploited in the development of effective antifibrotic therapies.

Fibrogenic cell fate during fibrotic tissue remodelling observed in rat and human cultured liver slices

Fibrotic liver remodelling was studied in culture of precision-cut liver slices (PCLS) derived from fibrotic liver. Fibrosis was induced in rats by carbon tetrachloride (CCl4) treatment or bile duct ligation. Human fibrotic livers were also used. PCLS were cultured for 6, 24, 48, or 72 h, and the expression of alpha-smooth muscle (SM) actin, platelet-derived growth factor (PDGF) receptor-beta, and active caspase 3 was studied by immunohistochemistry. Before culture, in CCl4-treated or bile duct ligated animals, fibrosis was observed around centrolobular veins, or in portal zones, respectively. In PCLS derived from CCl4-treated animals, alpha-SM actin expression disappeared after 24h in culture while PDGF receptor-beta expression decreased progressively after 48 h. These changes were observed in absence of massive apoptosis. In PCLS derived from bile duct ligated animals, both alpha-SM actin and PDGF receptor-beta expression decreased after 48 h in culture with a massive apoptosis. In PCLS derived from human fibrotic livers, alpha-SM actin expression was dramatically reduced after 48 h in culture. After CCl4 treatment, a proportion of myofibroblasts derived from hepatic stellate cells seems to dedifferentiate while in bile duct ligation model, myofibroblasts derived from portal fibroblasts disappear by apoptosis, underlining the relevance of this model to evaluate the mechanisms involved in fibrotic liver remodelling.

Matrix Metalloproteases in Aberrant Fibrotic Tissue Remodeling

Pulmonary fibrosis, the final result of a large variety of interstitial lung diseases, is characterized by an aberrant remodeling of extracellular matrix (ECM) with a profound disturbance of the normal lung architecture. This remodeling includes the exaggerated accumulation of ECM components in the interstitial and alveolar spaces and the disruption of the basement membranes. It has long been accepted that matrix metalloproteases (MMPs) play an important role in the pathogenesis of pulmonary fibrosis, but the exact mechanisms are not well characterized. Several MMPs are strongly up-regulated in human and experimental lung fibrosis, highlighting the dynamic nature of scarring within the lung. MMPs are collectively capable of cleaving all components of the ECM and basement membranes, but importantly, they also process bioactive mediators such as growth factors, cytokines, chemokines, and cell-surface receptors. Moreover, they participate in the initiation of proteinase cascades that impact much broader substrates. Consequently, MMPs may play a central role in several interrelated processes observed in fibrosis such as ECM remodeling, basement-membrane breakdown, epithelial-cell apoptosis, cell migration, and angiogenesis.

315 Fibrotic tissue remodelling in cultured precision-cut rat liver slices

315 Fibrotic tissue remodelling in cultured precision-cut rat liver slices

The Role of Transforming Growth Factor β in Lung Development and Disease

Transforming growth factor (TGF) beta plays an important role in normal pulmonary morphogenesis and function and in the pathogenesis of lung disease. The effect of TGFbeta is regulated via a selective pathway of TGFbeta synthesis and signaling that involves activation of latent TGFbeta, specific TGFbeta receptors, and intracellular signaling via Smad molecules. All three isoforms of TGFbeta are expressed at high levels during normal lung development, being particularly important for branching morphogenesis and epithelial cell differentiation with maturation of surfactant synthesis. Small amounts of TGFbeta are still present in the adult lung, and TGFbeta is involved in normal tissue repair following lung injury. However, in a variety of forms of pulmonary pathology, the expression of TGFbeta is increased. These include chronic lung disease of prematurity as well as several forms of acute and chronic adult lung disease. While TGFbeta1 appears to be the predominant isoform involved, elevated levels of all three isoforms have been demonstrated. The increase in TGFbeta precedes abnormalities in lung function and detectable lung pathology, but correlates with the severity of the disease. TGFbeta plays a key role in mediating fibrotic tissue remodeling by increasing the production and decreasing the degradation of connective tissue via several mechanisms.

Glucocorticoids and TGF-beta1 synergize in augmenting fibroblast mediated contraction of collagen gels.

TGF-beta 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-beta 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-beta in this system. In this study, human fetal lung fibroblasts (HFL-1) were pretreated with or without TGF-beta 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-beta significantly augmented gel contraction but also induced a 30% increase in PGE2 release and increased the expression of COX-1. Glucocorticoids inhibited TGF-beta1 induced-PGE2 release, and enhanced TGF-beta augmented gel contraction without significantly affecting TGF-beta augmented COX-1 expression. Indomethacin, a COX inhibitor, increased TGF-beta augmented gel contraction but had no further effect when added together with glucocorticoids. Thus, glucocorticoids can synergize with TGF-beta in augmenting fibroblast mediated collagen gel contraction through the inhibition of PGE2 production. Such interactions between glucocorticoids and TGF-beta may account, in part, for the lack of response of fibrotic diseases to glucocorticoids.

Cardiac Protective Effect of Aldosterone Blockade Is Mediated Through Ap-1 and Nf-κB Suppression in Angiotensin Ii-Induced Cardiac Damage

77 Aldosterone is a multifunctional mineralocorticoid affecting homeostasis of water and electrolytes, sympathetic activity, and tissue fibrosis. Aldosterone synthesis is induced by activation of the renin-angiotensin system. We tested whether or not the inhibition of aldosterone signaling can prevent fibrotic tissue remodeling in vivo. In a transgenic rat model overexpressing the human renin and angiotensinogen gens (dTGR), we investigated the effect of spironolactone (SPIRO 20 mg/kg/d) and the AT1 receptor blocker valsartan (VAL; 10 mg/kg/d) on growth factors and transcription factors leading chronic inflammation and tissue fibrosis. Untreated dTGR develop severe hypertension, cardiac hypertrophy, vasculopathy, and perivascular fibrosis. The hearts also show chronic inflammation and the animals have a 50% mortality at 7 weeks. VAL completely reversed these pathological features. SPIRO and VAL both prevented mortality, while only VAL normalized systolic blood pressure (VAL 121±9, SPIRO 161±11, dTGR 182±8, SD 109±2 mm Hg). Both reduced cardiac hypertrophy (SPIRO 4.2±0.1, VAL 3.6±0.1, dTGR 5.7±0.2, SD 3.6±0.1 mg/g) and reduced vasculopathy. Quantitative bFGF RT-PCR showed a complete mRNA reduction in the left ventricle in both treatment groups (SPIRO 11±4, VAL 5±1 dTGR 43±4, SD 4±1 arbitrary units). In contrast, RT-PCR of TGF beta and PDGF showed no upregulation in dTGR compared to non-transgenic hearts. Gel shift assay of the heart demonstrated a suppression of AP-1 and NF-κB DNA binding activity after SPIRO and VAL treatment. Immunohistology revealed reduced bFGF expression and less collagen I, fibronectin, and laminin in the interstitium of SPIRO and VAL-treated rats. These findings show that aldosterone promotes hypertrophy, cardiac remodeling, and fibrosis. In dTGR hearts this effect is at least partly mediated through the transcription factors AP-1 and NF-κB as well as bFGF. Blocking the aldosterone receptor downregulates these effector molecules and reduces angiotensin II-induced cardiac damage.

Cardiac Protective Effect of Aldosterone Blockade Is Mediated Through Ap-1 and Nf-κB Suppression in Angiotensin Ii-Induced Cardiac Damage

77 Aldosterone is a multifunctional mineralocorticoid affecting homeostasis of water and electrolytes, sympathetic activity, and tissue fibrosis. Aldosterone synthesis is induced by activation of the renin-angiotensin system. We tested whether or not the inhibition of aldosterone signaling can prevent fibrotic tissue remodeling in vivo. In a transgenic rat model overexpressing the human renin and angiotensinogen gens (dTGR), we investigated the effect of spironolactone (SPIRO 20 mg/kg/d) and the AT1 receptor blocker valsartan (VAL; 10 mg/kg/d) on growth factors and transcription factors leading chronic inflammation and tissue fibrosis. Untreated dTGR develop severe hypertension, cardiac hypertrophy, vasculopathy, and perivascular fibrosis. The hearts also show chronic inflammation and the animals have a 50% mortality at 7 weeks. VAL completely reversed these pathological features. SPIRO and VAL both prevented mortality, while only VAL normalized systolic blood pressure (VAL 121±9, SPIRO 161±11, dTGR 182±8, SD 109±2 mm Hg). Both reduced cardiac hypertrophy (SPIRO 4.2±0.1, VAL 3.6±0.1, dTGR 5.7±0.2, SD 3.6±0.1 mg/g) and reduced vasculopathy. Quantitative bFGF RT-PCR showed a complete mRNA reduction in the left ventricle in both treatment groups (SPIRO 11±4, VAL 5±1 dTGR 43±4, SD 4±1 arbitrary units). In contrast, RT-PCR of TGF beta and PDGF showed no upregulation in dTGR compared to non-transgenic hearts. Gel shift assay of the heart demonstrated a suppression of AP-1 and NF-κB DNA binding activity after SPIRO and VAL treatment. Immunohistology revealed reduced bFGF expression and less collagen I, fibronectin, and laminin in the interstitium of SPIRO and VAL-treated rats. These findings show that aldosterone promotes hypertrophy, cardiac remodeling, and fibrosis. In dTGR hearts this effect is at least partly mediated through the transcription factors AP-1 and NF-κB as well as bFGF. Blocking the aldosterone receptor downregulates these effector molecules and reduces angiotensin II-induced cardiac damage.