Myofibroblast Invasion Research Articles

A simple mouse model of pericardial adhesions

BackgroundPostoperative pericardial adhesions are considered a risk factor for redo cardiac surgery. Several large- and medium-size animal models of pericardial adhesions have been reported, but small animal models for investigating the development of anti-adhesion materials and molecular mechanisms of this condition are lacking. In this study, we aimed to establish a simple mouse model of pericardial adhesions to address this gap.MethodsWe administered blood, minocycline, picibanil, and talc into the murine pericardial cavity via one-shot injection. Micro-computed tomography analyses of contrast agent-injected mice were carried out for methodological evaluation. We investigated various dosages and treatment durations for molecules identified to be inducers of pericardial adhesion. The adhesive grade was quantified by scoring the strength and volume of adhesion tissues at sacrificed time points. Histological staining with hematoxylin and eosin and Masson’s trichrome, and immunostaining for F4/80 or αSMA was performed to investigate the structural features of pericardial adhesions, and pathological features of the pericardial adhesion tissue were compared with human clinical specimens.ResultsAdministration of talc resulted in the most extensive pericardial adhesions. Micro-computed tomography imaging data confirmed that accurate injection into the pericardial cavity was achieved. We found the optimal condition for the formation of strong pericardial adhesions to be injection of 2.5 mg/g talc for 2 weeks. Furthermore, histological analysis showed that talc administration led to an invasion of myofibroblasts and macrophages in the pericardial cavity and epicardium, consistent with pathological findings in patients with left ventricular assistive devices.ConclusionsWe successfully established a simple mouse model of talc-induced pericardial adhesions, which mimics human pathology and could contribute to solving the clinical issues related to pericardial adhesions.

FOXF1 Inhibits Pulmonary Fibrosis by Preventing CDH2-CDH11 Cadherin Switch in Myofibroblasts

SUMMARYIdiopathic pulmonary fibrosis (IPF) is characterized by aberrant accumulation of collagen-secreting myofibroblasts. Development of effective therapies is limited due to incomplete understanding of molecular mechanisms regulating myofibroblast expansion. FOXF1 transcription factor is expressed in resident lung fibroblasts, but its role in lung fibrosis remains unknown due to the lack of genetic mouse models. Through comprehensive analysis of human IPF genomics data, lung biopsies, and transgenic mice with fibroblast-specific inactivation of FOXF1, we show that FOXF1 inhibits pulmonary fibrosis. FOXF1 deletion increases myofibroblast invasion and collagen secretion and promotes a switch from N-cadherin (CDH2) to Cadherin-11 (CDH11), which is a critical step in the acquisition of the profibrotic phenotype. FOXF1 directly binds to Cdh2 and Cdh11 promoters and differentially regulates transcription of these genes. Re-expression of CDH2 or inhibition of CDH11 in FOXF1-deficient cells reduces myofibroblast invasion in vitro. FOXF1 inhibits pulmonary fibrosis by regulating a switch from CDH2 to CDH11 in lung myofibroblasts.

Transforming growth factor β1 (TGFβ1)-induced CD44V6-NOX4 signaling in pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive clinical syndrome of fatal outcome. The lack of information about the signaling pathways that sustain fibrosis and the myofibroblast phenotype has prevented the development of targeted therapies for IPF. Our previous study showed that isolated fibrogenic lung fibroblasts have high endogenous levels of the hyaluronan receptor, CD44V6 (CD44 variant containing exon 6), which enhances the TGFβ1 autocrine signaling and induces fibroblasts to transdifferentiate into myofibroblasts. NADPH oxidase 4 (NOX4) enzyme, which catalyzes the reduction of O2 to hydrogen peroxide (H2O2), has been implicated in the cardiac and lung myofibroblast phenotype. However, whether CD44V6 regulates NOX4 to mediate tissue repair and fibrogenesis is not well-defined. The present study assessed the mechanism of how TGF-β-1-induced CD44V6 regulates the NOX4/reactive oxygen species (ROS) signaling that mediates the myofibroblast differentiation. Specifically, we found that NOX4/ROS regulates hyaluronan synthesis and the transcription of CD44V6 via an effect upon AP-1 activity. Further, CD44V6 is part of a positive-feedback loop with TGFβ1/TGFβRI signaling that acts to increase NOX4/ROS production, which is required for myofibroblast differentiation, myofibroblast differentiation, myofibroblast extracellular matrix production, myofibroblast invasion, and myofibroblast contractility. Both NOX4 and CD44v6 are up-regulated in the lungs of mice subjected to experimental lung injury and in cases of human IPF. Genetic (CD44v6 shRNA) or a small molecule inhibitor (CD44v6 peptide) targeting of CD44v6 abrogates fibrogenesis in murine models of lung injury. These studies support a function for CD44V6 in lung fibrosis and offer proof of concept for therapeutic targeting of CD44V6 in lung fibrosis disorders.

Glucagon-like petide-2 acts on colon cancer myofibroblasts to stimulate proliferation, migration and invasion of both myofibroblasts and cancer cells via the IGF pathway

Glucagon-like peptide (GLP)-2 stimulates intestinal epithelial proliferation by acting, in part, via IGF release from sub-epithelial myofibroblasts. The response of myofibroblasts to GLP-2 remains incompletely understood. We studied the action of GLP-2 on myofibroblasts from colon cancer and adjacent tissue, and the effects of conditioned medium from these cells on epithelial cell proliferation, migration and invasion. GLP-2 stimulated proliferation, migration and invasion of myofibroblasts and the proliferative and invasive responses of cancer-associated myofibroblasts were greater than those of myofibroblasts from adjacent tissue. The responses were inhibited by an IGF receptor inhibitor, AG1024. Conditioned medium from GLP-2 treated myofibroblasts increased proliferation, migration and invasion of SW480, HT29, LoVo epithelial cells and these responses were inhibited by AG1024; GLP-2 alone had no effect on these cells. In addition, when myofibroblasts and epithelial cells were co-cultured in Ibidi chambers there was mutual stimulation of migration in response to GLP-2. The latter increased both IGF-1 and IGF-2 transcript abundance in myofibroblasts. Moreover, a number of IGF binding proteins (IGFBP-4, −5, −7) were identified in myofibroblast medium; in the presence of GLP-2 there was increased abundance of the cleavage products of IGBBP-4 and IGFBP-5 suggesting activation of a degradation mechanism that might increase IGF bioavailability. The data suggest that GLP-2 stimulates cancer myofibroblast proliferation, migration and invasion; GLP-2 acts indirectly on epithelial cells partly via increased IGF expression in myofibroblasts and partly, perhaps, by increased bioavailability through degradation of IGFBPs.

Mechanosensing by the α6-integrin confers an invasive fibroblast phenotype and mediates lung fibrosis

Matrix stiffening is a prominent feature of pulmonary fibrosis. In this study, we demonstrate that matrix stiffness regulates the ability of fibrotic lung myofibroblasts to invade the basement membrane (BM). We identify α6-integrin as a mechanosensing integrin subunit that mediates matrix stiffness-regulated myofibroblast invasion. Increasing α6-expression, specifically the B isoform (α6B), couples β1-integrin to mediate MMP-2-dependent pericellular proteolysis of BM collagen IV, leading to myofibroblast invasion. Human idiopathic pulmonary fibrosis lung myofibroblasts express high levels of α6-integrin in vitro and in vivo. Genetic ablation of α6 in collagen-expressing mesenchymal cells or pharmacological blockade of matrix stiffness-regulated α6-expression protects mice against bleomycin injury-induced experimental lung fibrosis. These findings suggest that α6-integrin is a matrix stiffness-regulated mechanosensitive molecule which confers an invasive fibroblast phenotype and mediates experimental lung fibrosis. Targeting this mechanosensing α6(β1)-integrin offers a novel anti-fibrotic strategy against lung fibrosis.

Inflammatory reaction as determinant of foreign body reaction is an early and susceptible event after mesh implantation.

Purpose. To investigate and relate the ultrashort-term and long-term courses of determinants for foreign body reaction as biocompatibility predictors for meshes in an animal model. Materials and Methods. Three different meshes (TVT, UltraPro, and PVDF) were implanted in sheep. Native and plasma coated meshes were placed bilaterally: (a) interaperitoneally, (b) as fascia onlay, and (c) as muscle onlay (fascia sublay). At 5 min, 20 min, 60 min, and 120 min meshes were explanted and histochemically investigated for inflammatory infiltrate, macrophage infiltration, vessel formation, myofibroblast invasion, and connective tissue accumulation. The results were related to long-term values over 24 months. Results. Macrophage invasion reached highest extents with up to 60% in short-term and decreased within 24 months to about 30%. Inflammatory infiltrate increased within the first 2 hours, the reached levels and the different extents and ranking among the investigated meshes remained stable during long-term follow up. For myofibroblasts, connective tissue, and CD31+ cells, no activity was detected during the first 120 min. Conclusion. The local inflammatory reaction is an early and susceptible event after mesh implantation. It cannot be influenced by prior plasma coating and does not depend on the localisation of implantation.

Inhibition of muscle fibrosis and improvement of muscle histopathology in dysferlin knock-out mice treated with halofuginone.

Absence of, or loss-of-function mutations in the dysferlin gene (dysf) result in dysferlinopathy, characterized by increased muscle inflammation, collagen deposition and deterioration in muscle function. We evaluated halofuginone efficacy in improving muscle histopathology in mice with deleted dysf transmembrane domain. Quadriceps sublumbar and longissimus muscles of 9-month-old dysf-/- mice treated with halofuginone for 4 months exhibited a reduction in centrally-nucleated myofibers, inflammatory infiltrates and collagen content. Late onset of dysferlinopathy makes it ideal for evaluating the efficacy of early treatments on late outcome. The dysf-/- mice were treated with halofuginone for 3 to 4 months starting at 1, 5 or 9 months of age, and quadricep muscle histopathology was evaluated at 12 months. Collagen content and number of centrally nucleated myofibers decreased after early halofuginone treatment, administered when myofibers with central nuclei and inflammatory infiltrates are evident, but there was almost no fibrosis. When administered at the beginning of fibrosis it resulted in a further decrease in the number of centrally-nucleated myofibers with no additional decrease in collagen levels. Cardiac fibrosis was almost completely abolished following early halofuginone treatment. Halofuginone inhibited Smad3 phosphorylation and its translocation to the nucleus and increased the activity of matrix metalloproteinases 9 and 2 responsible for resolution of pre-existing collagen. Macrophage and myofibroblast invasion into the dystrophic muscle at the site of myofibers with central nuclei was inhibited by halofuginone. These results suggest that early halofuginone treatment can prevent the late outcome of dysferlinopathy and can cause resolution of the established fibrosis when administered at later stages.

Hypoxic remodelling of Ca 2+ stores does not alter human cardiac myofibroblast invasion

Cardiac fibroblasts are the most abundant cell type in the heart, and play a key role in the maintenance and repair of the myocardium following damage such as myocardial infarction by transforming into a cardiac myofibroblast (CMF) phenotype. Repair occurs through controlled proliferation and migration, which are Ca 2+ dependent processes, and often requires the cells to operate within a hypoxic environment. Angiotensin converting enzyme (ACE) inhibitors reduce infarct size through the promotion of bradykinin (BK) stability. Although CMF express BK receptors, their activity under the reduced O 2 conditions that occur following infarct are entirely unexplored. Using Fura-2 microfluorimetry on primary human CMF, we found that hypoxia significantly increased the mobilisation of Ca 2+ from intracellular stores in response to BK whilst capacitative Ca 2+ entry (CCE) remained unchanged. The enhanced store mobilisation was due to a striking increase in CMF intracellular Ca 2+-store content under hypoxic conditions. However, BK-induced CMF migration or proliferation was not affected following hypoxic exposure, suggesting that Ca 2+ influx rather than mobilisation is of primary importance in CMF migration and proliferation.

Cortical Neural Precursors Inhibit Their Own Differentiation via N-Cadherin Maintenance of β-Catenin Signaling

Little is known about the architecture of cellular microenvironments that support stem and precursor cells during tissue development. Although adult stem cell niches are organized by specialized supporting cells, in the developing cerebral cortex, neural stem/precursor cells reside in a neurogenic niche lacking distinct supporting cells. Here, we find that neural precursors themselves comprise the niche and regulate their own development. Precursor-precursor contact regulates beta-catenin signaling and cell fate. In vivo knockdown of N-cadherin reduces beta-catenin signaling, migration from the niche, and neuronal differentiation in vivo. N-cadherin engagement activates beta-catenin signaling via Akt, suggesting a mechanism through which cells in tissues can regulate their development. These results suggest that neural precursor cell interactions can generate a self-supportive niche to regulate their own number.

Loss of myeloid cell-derived vascular endothelial growth factor accelerates fibrosis

Tissue injury initiates a complex series of events that act to restore structure and physiological homeostasis. Infiltration of inflammatory cells and vascular remodeling are both keystones of this process. However, the role of inflammation and angiogenesis in general and, more specifically, the significance of inflammatory cell-derived VEGF in this context are unclear. To determine the role of inflammatory cell-derived VEGF in a clinically relevant and chronically inflamed injury, pulmonary fibrosis, we deleted the VEGF-A gene in myeloid cells. In a model of pulmonary fibrosis in mice, deletion of VEGF in myeloid cells resulted in significantly reduced formation of blood vessels; however, it causes aggravated fibrotic tissue damage. This was accompanied by a pronounced decrease in epithelial cell survival and a striking increase in myofibroblast invasion. The drastic increase in fibrosis following loss of myeloid VEGF in the damaged lungs was also marked by increased levels of hypoxia-inducible factor (HIF) expression and Wnt/beta-catenin signaling. This demonstrates that the process of angiogenesis, driven by myeloid cell-derived VEGF, is essential for the prevention of fibrotic damage.

Chronic hypoxia inhibits MMP-2 activation and cellular invasion in human cardiac myofibroblasts

Cardiac myofibroblasts are pivotal to adaptive remodelling after myocardial infarction (MI). These normally quiescent cells invade and proliferate as a wound healing response, facilitated by activation of matrix metalloproteinases, particularly MMP-2. Following MI these reparative events occur under chronically hypoxic conditions yet the mechanisms by which hypoxia might modulate MMP-2 activation and cardiac myofibroblast invasion have not been investigated. Human cardiac myofibroblasts cultured in collagen-supplemented medium were exposed to normoxia (20% O2) or hypoxia (1% O2) for up to 48 h. Secreted levels of total and active MMP-2 were quantified using gelatin zymography, TIMP-2 and membrane-associated MT1-MMP were quantified with ELISA, whole cell MT1-MMP by immunoblotting and immunocytochemistry and MT1-MMP mRNA with real-time RT-PCR. Cellular invasion was assessed in modified Boyden chambers and migration by scratch wound assay.In the human cardiac myofibroblast, MT1-MMP was central to MMP-2 activation and activated MMP-2 necessary for invasion, confirmed by gene silencing. MMP-2 activation was substantially attenuated by hypoxia (P<0.001), paralleled by inhibition of myofibroblast invasion (P<0.05). In contrast, migration was independent of either MT1-MMP or MMP-2. Reduced membrane expression of MT1-MMP (P<0.05) was responsible for the hypoxic reduction of MMP-2 activation, with no change in either total MMP-2 or TIMP-2. In conclusion, hypoxia reduces MMP-2 activation and subsequent invasion of human cardiac myofibroblasts by reducing membrane expression of MT1-MMP and may delay healing after MI. Regulation of these MMPs remains an attractive target for therapeutic intervention.

Stroma reactions and cancer invasion

Stroma reactions and cancer invasion

Simvastatin inhibits TNFα-induced invasion of human cardiac myofibroblasts via both MMP-9-dependent and -independent mechanisms

Statins can reduce adverse myocardial remodeling independently of their cholesterol-lowering ability. We have previously reported that simvastatin inhibits tumor necrosis factor-α (TNFα)-induced cardiac myofibroblast invasion and MMP-9 secretion, key events in this remodeling process. The aim of the present study was to investigate the mechanisms underlying this effect. Selective MMP-9 gene silencing with siRNA oligonucleotides revealed that myofibroblast invasion through a Matrigel barrier (Boyden chamber assay) was MMP-9-dependent. In contrast, cell migration (in the absence of Matrigel) was MMP-9-independent. Simvastatin, a commonly prescribed statin, inhibited both invasion and migration of myofibroblasts and disrupted the actin cytoskeleton as determined by confocal microscopy of rhodamine–phalloidin staining. All these effects of simvastatin were mimicked by the Rho-kinase inhibitor Y27632. TNFα activated the ERK-1/2, p38 MAPK, PI-3-kinase and NF-κB pathways but not the JNK pathway, as determined by immunoblotting with phospho-specific antibodies. Quantitative RT-PCR revealed that TNFα-induced MMP-9 mRNA expression was substantially reduced by pharmacological inhibitors of the ERK-1/2, PI-3-kinase and NF-κB pathways. However, none of the signal transduction pathways studied was influenced by simvastatin treatment. Moreover, despite reducing MMP-9 secretion, simvastatin had no effect on MMP-9 promoter activity (luciferase reporter assay) and actually increased MMP-9 mRNA levels. In summary, simvastatin reduces TNFα-induced invasion of human cardiac myofibroblasts through two distinct mechanisms: (i) by attenuating cell migration via Rho-kinase inhibition and subsequent cytoskeletal disruption, and (ii) by decreasing MMP-9 secretion via a post-transcriptional mechanism.

Tumor necrosis factor ? induces human atrial myofibroblast proliferation, invasion and MMP-9 secretion: inhibition by simvastatin

Tumor necrosis factor alpha (TNFalpha) is implicated in myocardial remodeling, a process in which activated cardiac fibroblasts (myofibroblasts) secrete matrix-degrading metalloproteinases (MMPs) and undergo increased proliferation and invasion. Statins are cholesterol-lowering drugs that also have direct cellular effects, which may underlie their ability to reduce myocardial remodeling. This study investigated the effect of TNFalpha on human cardiac myofibroblast proliferation, invasion and MMP-9 secretion, and determined whether these properties were modulated by simvastatin. Human cardiac myofibroblasts were cultured from right atrial appendage. TNF receptor expression was quantified by immunoblotting. Cell proliferation, invasion, MMP-9 secretion and MMP-9 mRNA expression were determined by cell counting, Matrigel-coated modified Boyden chamber assays, gelatin zymography and RT-PCR, respectively. Human atrial myofibroblasts expressed the TNF-RI and TNF-RII receptor subtypes. TNFalpha (1 ng/ml) induced a 23.1+/-3.9% increase in cell number after 4 days (P<0.001). Additionally, TNFalpha (1-10 ng/ml) significantly (P<0.01) increased myofibroblast invasion, with a concomitant increase in MMP-9 secretion, that was due to increased MMP-9 mRNA levels. Using TNF-R-specific neutralizing antibodies, we determined that these cellular effects of TNFalpha were predominantly TNF-RI-mediated. Simvastatin (0.1-10 mumol/l) concentration dependently inhibited TNFalpha-induced myofibroblast proliferation, invasion and MMP-9 secretion. TNFalpha, acting predominantly via the TNF-R1 receptor, increased human atrial myofibroblast proliferation, invasion and MMP-9 secretion, all of which were inhibited by simvastatin. Inhibition of cytokine-induced cardiac myofibroblast activation by statins provides a rationale for their use in patients with cardiac pathologies characterized by adverse myocardial remodeling.

Critical role of N-cadherin in myofibroblast invasion and migration in vitro stimulated by colon-cancer-cell-derived TGF-beta or wounding.

Invasion of stromal host cells, such as myofibroblasts, into the epithelial cancer compartment may precede epithelial cancer invasion into the stroma. We investigated how colon cancer-derived myofibroblasts invade extracellular matrices in vitro in the presence of colon cancer cells. Myofibroblast spheroids invade collagen type I in a stellate pattern to form a dendritic network of extensions upon co-culture with HCT-8/E11 colon cancer cells. Single myofibroblasts also invade Matrigel trade mark when stimulated by HCT-8/E11 colon cancer cells. The confrontation of cancer cells with extracellular matrices and myofibroblasts, showed that cancer-cell-derived transforming growth factor-beta (TGF-beta) is required and sufficient for invasion of myofibroblasts. In myofibroblasts, N-cadherin expressed at the tips of filopodia is upregulated by TGF-beta. Functional N-cadherin activity is implicated in TGF-beta stimulated invasion as evidenced by the neutralizing anti-N-cadherin monoclonal antibody (GC-4 mAb), and specific N-cadherin knock-down by short interference RNA (siRNA). TGF-beta1 stimulates Jun N-terminal kinase (also known as stress-activated protein kinase) (JNK) activity in myofibroblasts. Pharmacological inhibition of JNK alleviates TGF-beta stimulated invasion, N-cadherin expression and wound healing migration. Neutralization of N-cadherin activity by the GC-4 or by a 10-mer N-cadherin peptide or by siRNA reduces directional migration, filopodia formation, polarization and Golgi-complex reorientation during wound healing. Taken together, our study identifies a new mechanism in which cancer cells contribute to the coordination of invasion of stromal myofibroblasts.