Fibronectin Matrix Research Articles

Liarozole inhibits transforming growth factor-β3–mediated extracellular matrix formation in human three-dimensional leiomyoma cultures

To investigate the impact of liarozole on transforming growth factor-β3 (TGF-β3) expression, TGF-β3 controlled profibrotic cytokines, and extracellular matrix formation in a three-dimensional (3D) leiomyoma model system. Molecular and immunohistochemical analysis in a cell line evaluated in a three-dimensional culture. Laboratory study. None. Treatment of leiomyoma and myometrial cells with liarozole and TGF-β3 in a three-dimensional culture system. Quantitative real-time reverse-transcriptase polymerase chain reaction and Western blotting to assess fold gene and protein expression of TGF-β3 and TGF-β3 regulated fibrotic cytokines: collagen 1A1 (COL1A1), fibronectin, and versican before and after treatment with liarozole, and confirmatory immunohistochemical stains of treated three-dimensional cultures. Both TGF-β3 gene and protein expression were elevated in leiomyoma cells compared with myometrium in two-dimensional and 3D cultures. Treatment with liarozole decreased TGF-β3 gene and protein expression. Extracellular matrix components versican, COL1A1, and fibronectin were also decreased by liarozole treatment in 3D cultures. Treatment of 3D cultures with TGF-β3 increased gene expression and protein production of COL1A1, fibronectin, and versican. Liarozole decreased TGF-β3 and TGF-β3-mediated extracellular matrix expression in a 3D uterine leiomyoma culture system.

Abstract 554: Multimerin2 Influences Vascularization Through Modulation of Perlecan

Vascular development is crucial in normal physiology and pathophysiology, and is in part orchestrated by a dynamic balance between extracellular matrix (ECM) and endothelial cells. The molecular mechanisms that govern this balance and as such play a role in the formation of new blood vessels remain largely unknown. In order to identify new genes involved in blood vessel formation, we performed a genome-wide gene expression array analysis in Flk1+ angioblasts during mouse development using a commercial platform (Affymetrix). Multimerin2 (Mmrn2) expression was found to be upregulated in angioblasts and in the developing vasculature of zebrafish and mice. In vitro , using immunofluorescence, Mmrn2 was detected outside of human aortic endothelial cells (HAECs), were it co-localized with the extracellular matrix components perlecan, laminin and fibronectin. Direct interaction with these proteins was confirmed using a combination of co-immunoprecipitation followed by proteomics (LC-MS), and western blot to identify possible binding partners. Mmrn2 gain-of-function and loss-of-function in vitro studies, using Mmrn2 siRNA and adenoviral constructs likewise decreased and increased the expression of its binding partner perlecan. Perlecan is a well known modulator of the pro-angiogenic factor, FGF2, and is required for further signaling through the FGF receptor. Therefore, Mmrn2 may influence FGF2 signaling through perlecan expression and complex formation. Subsequent in vitro studies using an adenoviral construct to induce Mmrn2 overexpression resulted in a G1-arrest in HAECs (P<0.001, N=8). In FGF2 depleted medium a G1 arrest was also observed (P<0.05, N=3), Mmrn2 overexpression combined with FGF2 depleted medium did not enhance the G1 arrest, suggesting a role of Mmrn2 in FGF2 signaling. In addition, Mmrn2 silencing or overexpression in HAECs led to a loss of ECM organization or improved organization, respectively. In line, the binding partner of Mmrn2, perlecan, has been shown to be involved in stabilization of the ECM. These findings suggest that Mmrn2 plays a role during blood vessel formation by binding to perlecan and the ECM, thereby modulating FGF2 signaling and ECM organization and subsequently, regulating endothelial cell proliferation.

Fibronectin matrix polymerization regulates smooth muscle cell phenotype through a Rac1 dependent mechanism.

Smooth muscle cells are maintained in a differentiated state in the vessel wall, but can be modulated to a synthetic phenotype following injury. Smooth muscle phenotypic modulation is thought to play an important role in the pathology of vascular occlusive diseases. Phenotypically modulated smooth muscle cells exhibit increased proliferative and migratory properties that accompany the downregulation of smooth muscle cell marker proteins. Extracellular matrix proteins, including fibronectin, can regulate the smooth muscle phenotype when used as adhesive substrates. However, cells produce and organize a 3-dimensional fibrillar extracellular matrix, which can affect cell behavior in distinct ways from the protomeric 2-dimensional matrix proteins that are used as adhesive substrates. We previously showed that the deposition/polymerization of fibronectin into the extracellular matrix can regulate the deposition and organization of other extracellular matrix molecules in vitro. Further, our published data show that the presence of a fibronectin polymerization inhibitor results in increased expression of smooth muscle cell differentiation proteins and inhibits vascular remodeling in vivo. In this manuscript, we used an in vitro cell culture system to determine the mechanism by which fibronectin polymerization affects smooth muscle phenotypic modulation. Our data show that fibronectin polymerization decreases the mRNA levels of multiple smooth muscle differentiation genes, and downregulates the levels of smooth muscle α-actin and calponin proteins by a Rac1-dependent mechanism. The expression of smooth muscle genes is transcriptionally regulated by fibronectin polymerization, as evidenced by the increased activity of luciferase reporter constructs in the presence of a fibronectin polymerization inhibitor. Fibronectin polymerization also promotes smooth muscle cell growth, and decreases the levels of actin stress fibers. These data define a Rac1-dependent pathway wherein fibronectin polymerization promotes the SMC synthetic phenotype by modulating the expression of smooth muscle cell differentiation proteins.

Proteominer facilitates high‐throughput proteomic analysis of low abundance proteins in the cartilage secretome (LB39)

Proteomics is increasingly used for biomarker identification. We have developed high‐throughput mass spectrometric (MS) methods to identify proteins in the secretome of articular cartilage explants, which we are utilizing as an in vitro model of joint inflammation. However, the identification of lower abundance proteins of potentially higher biological significance in this model is hampered by the presence of highly abundant glycoproteins in the secretome. Development of protein depletion techniques that allow the identification of low abundance proteins is important for novel biomarker discovery, especially in the context of identifying pathophysiologically relevant biomarkers of joint inflammation and cartilage degradation. Proteominer protein enrichment kits decrease the dynamic range of complex biological samples, allowing improved analytical coverage of the proteome. The objective of this study was to apply high‐throughput MS techniques following proteominer enrichment to expand the range of proteins that can be identified in the secretome of cartilage exposed to proinflammatory cytokines such as IL‐1β. Explant cultures were established in DMEM + 2% Pen/Strep, using metacarpophalangeal joints of horses. Explants were either untreated controls or treated with 10 ng/ml IL‐1β. After incubating for 6 days at 37⁰C in a humidified environment (95% air, 5% CO2) proteins in culture supernatants were concentrated ~24 fold using Centriplus YM‐3 and Centricon‐3 (3000 MWCO) centrifugal filter units. Concentrated samples were processed with a Small Capacity Proteominer™ Protein Enrichment Kit (Bio‐Rad). After elution, samples were reduced, alkylated, acetone precipitated and trypsin digested overnight, before digested peptides were applied to C18 spin columns, followed by nanoLC‐MS/MS analysis on an amaZon speed ETD. Extracellular matrix proteins identified in untreated control secretome included cartilage oligomeric matrix protein (COMP), fibromodulin and fibronectin. Macrophage migration inhibitory factor (MIF), serum amyloid A protein (SAA) and Heat shock 70 kDa protein 1‐like (HSP70) were identified in explants exposed to IL‐1β. Identification of new low abundance proteins in this model will facilitate a greater understanding of inflammatory processes occurring within cartilage.Grant Funding Source: Supported by Biotechnology and Biological Sciences Research Council (BBSRC) (Contract grant number: BB/G018030/1) and the European Commission Framework 7 program (EU FP7; HEALTH.2012.2.4.5–2, project number 305815).

MYPT1 regulates contractility and microtubule acetylation to modulate integrin adhesions and matrix assembly

Although much is known about how individual cytoskeletal systems contribute to physiological processes such as cell migration and branching morphogenesis, little is known about how these different systems actively coordinate their functions after polymerization. Here we show that both fibroblasts and developing glands reciprocally coordinate levels of cellular contractility and microtubule acetylation. We find that this balance is achieved by interaction of the myosin phosphatase target subunit of myosin phosphatase with either myosin light chain or HDAC6, a microtubule deacetylase. This balance of contractility and microtubule acetylation controls progression of adhesion maturation by regulating surface density of α5β1 integrin and fibronectin. Thus, we propose that a homeostatic balance between contractility and microtubule acetylation is mediated by myosin phosphatase via controlled activation and deactivation of myosin II and HDAC6. This regulates the surface density of α5β1 integrin to modulate fibronectin matrix assembly and governs rates of cell migration and branching morphogenesis.

Vascular Morphogenesis of Human Umbilical Vein Endothelial Cells on Cell-Derived Macromolecular Matrix Microenvironment

Extracellular matrix (ECM) is a highly organized network of proteins and other macromolecules that plays a critical role in cell adhesion, migration, and differentiation. In this study, we hypothesize that ECM derived from in-vitro-cultured cells possesses unique surface texture, topography, and mechanical property, and consequently carries some distinct cues for vascular morphogenesis of human umbilical vein endothelial cells (ECs). Cell-derived matrix (CDM) was obtained by culturing fibroblasts, preosteoblasts, and chondrocytes, respectively, on coverslips and then by decellularizing them using detergents and enzymes. These matrices were named fibroblast-derived matrix (FDM), preosteoblast-derived matrix (PDM), and chondrocyte-derived matrix (CHDM). Immunofluorescence of each CDM shows that some of the matrix components are fibronectin (FN), type I collagen, and laminin. Atomic force microscopy analysis presented that average fiber diameter ranged from 2 to 7 μm and FDM holds much larger fibers. The matrix elasticity measurements revealed that average Young's modulus of CHDM (17.7 ± 4.2 kPa) was much greater than that of PDM (10.5 ± 1.1 kPa) or FDM (5.7 ± 0.5 kPa). During 5-day culture, EC morphologies were dramatically changed on PDM and FDM, but those on CHDM and gelatin were rather stable, regardless of time lapse. Cell migration assay discovered quicker repopulation of the scratched areas on PDM and FDM than on gelatin and CHDM. A capillary-like structure (CLS) assembly was also notable only in the PDM and FDM, as compared with CHDM, gelatin, or FN that were very poor in CLS formation. Quantitative analysis of mean CLS branch points and branch lengths demonstrated much better angiogenic activity of ECs on PDM and FDM. Interestingly, CLS formation was closely associated with matrix remodeling by ECs and the matrix clearance on PDM with time was sharply contrasted with that on CHDM that majority of the matrix FN was reserved. It was notable that membrane type 1-matrix metalloprotease was deeply involved in the process of matrix remodeling. This study indicates that specific matrix microenvironments are very critical for vascular morphogenesis of ECs, and thus, provide a nice platform for angiogenesis study as well as vascular tissue engineering.

A plasminogen activator inhibitor type 1 mutant retards diabetic nephropathy in db/db mice by protecting podocytes

New Findings What is the central question of this study? The mechanism by which PAI‐1R reduces proteinuria has not been previously explored. What is the main finding and its importance? Using cultured podocytes and diabetic db/db mice, we show that, similar to the effects of transforming growth factor‐β1, PAI‐1 directly injures podocytes. Reducing the increased PAI‐1 activity by PAI‐1R in diabetic db/db mice, in fact, reduces podocyte injury, thereby reducing albuminuria. Therefore, PAI‐1R may provide an additional therapeutic effect in slowing progression of diabetic nephropathy by maintaining podocyte integrity. A mutant non‐inhibiting plasminogen activator inhibitor type 1 (PAI‐1), termed PAI‐1R, which reduces endogenous PAI‐1 activity, has been shown to inhibit albuminuria and reduce glomerulosclerosis in experimental diabetes. The mechanism of the reduction of albuminuria is unclear. This study sought to determine whether the administration of PAI‐1R protected podocytes from injury directly, thereby reducing albuminuria in the db/db mouse, a model of type 2 diabetes. Untreated uninephrectomized db/db mice developed significant mesangial matrix expansion and albuminuria at week 22 of age, associated with segmental podocyte foot‐process effacement, reduction of renal nephrin, podocin and zonula occludin‐1 production and induction of renal desmin and B7‐1 generation. In contrast, treatment with PAI‐1R at 0.5 mg (kg body weight)−1 i.p., twice daily from week 20 to 22, reduced glomerular matrix accumulation, fibronectin and collagen production and albuminuria by 36, 62, 65 and 31%, respectively (P < 0.05), without affecting blood glucose level or body weight. Podocyte morphology and protein markers were also significantly attenuated by PAI‐1R administration. Importantly, recombinant PAI‐1 downregulated nephrin and zonula occludin‐1 but increased desmin and B7‐1 mRNA expression and protein production by podocytes in vitro, similar to the effects of transforming growth factor‐β1. These observations provide evidence that PAI‐1, in a manner similar to transforming growth factor‐β1, directly induces podocyte injury, particularly in the setting of diabetes, where elevated PAI‐1 may contribute to the progression of albuminuria. Reducing the increased PAI‐1 activity by administration of PAI‐1R, in fact, reduces podocyte injury, thereby reducing albuminuria. Therefore, PAI‐1R provides an additional therapeutic effect in slowing the progression of diabetic nephropathy via the protection of podocytes.

Avidity-Controlled Delivery of Angiogenic Peptides from Injectable Molecular-Recognition Hydrogels

Peptide mimics of growth factors represent an emerging class of therapeutic drugs due to high biological specificity and relative ease of synthesis. However, maintaining efficacious therapeutic dosage at the therapy site has proven challenging owing to poor intestinal permeability and short circulating half-lives in the blood stream. In this work, we present the affinity immobilization and controlled release of QK, a vascular endothelial growth factor (VEGF) mimetic peptide, from an injectable mixing-induced two-component hydrogel (MITCH). The MITCH system is crosslinked by reversible interactions between WW domains and complementary proline-rich peptide modules. Fusion of the QK peptide to either one or two units of the proline-rich sequence creates bifunctional peptide conjugates capable of specific binding to MITCH while preserving their angiogenic bioactivity. Presenting two repeats of the proline-rich sequence increases the binding enthalpy 2.5 times due to avidity effects. Mixing of the drug conjugates with MITCH components results in drug encapsulation and extended release at rates consistent with the affinity immobilization strength. Human umbilical vein endothelial cells (HUVECs) treated with the soluble drug conjugates exhibit morphogenetic events of VEGF receptor 2 signal transduction followed by cell migration and organization into networks characteristic of early angiogenesis. In a three-dimensional model where HUVECs were cultured as spheroids in a matrix of collagen and fibronectin, injection of drug-releasing MITCH resulted in significantly more cell outgrowth than drugs injected in saline. This ability to sustain local drug availability is ideal for therapeutic angiogenesis applications, where spatiotemporal control over drug distribution is a key requirement for clinical success.

Opposing effects of collagen I and vitronectin on fibronectin fibril structure and function

Extracellular matrix fibronectin fibrils serve as passive structural supports for the organization of cells into tissues, yet can also actively stimulate a variety of cell and tissue functions, including cell proliferation. Factors that control and coordinate the functional activities of fibronectin fibrils are not known. Here, we compared effects of cell adhesion to vitronectin versus type I collagen on the assembly of and response to, extracellular matrix fibronectin fibrils. The amount of insoluble fibronectin matrix fibrils assembled by fibronectin-null mouse embryonic fibroblasts adherent to collagen- or vitronectin-coated substrates was not significantly different 20h after fibronectin addition. However, the fibronectin matrix produced by vitronectin-adherent cells was ~10-fold less effective at enhancing cell proliferation than that of collagen-adherent cells. Increasing insoluble fibronectin levels with the fibronectin fragment, anastellin did not increase cell proliferation. Rather, native fibronectin fibrils polymerized by collagen- and vitronectin-adherent cells exhibited conformational differences in the growth-promoting, III-1 region of fibronectin, with collagen-adherent cells producing fibronectin fibrils in a more extended conformation. Fibronectin matrix assembly on either substrate was mediated by α5β1 integrins. However, on vitronectin-adherent cells, α5β1 integrins functioned in a lower activation state, characterized by reduced 9EG7 binding and decreased talin association. The inhibitory effect of vitronectin on fibronectin-mediated cell proliferation was localized to the cell-binding domain, but was not a general property of αvβ3 integrin-binding substrates. These data suggest that adhesion to vitronectin allows for the uncoupling of fibronectin fibril formation from downstream signaling events by reducing α5β1 integrin activation and fibronectin fibril extension.

Hsp90 Binds Directly to Fibronectin (FN) and Inhibition Reduces the Extracellular Fibronectin Matrix in Breast Cancer Cells

Heat shock protein 90 (Hsp90) has been identified in the extracellular space and has been shown to chaperone a finite number of extracellular proteins involved in cell migration and invasion. We used chemical cross-linking and immunoprecipitation followed by tandem mass spectrometry (MS/MS) to isolate a complex containing Hsp90 and the matrix protein fibronectin (FN) from breast cancer cells. Further analysis showed direct binding of Hsp90 to FN using an in vitro co-immunoprecipitation assay, a solid phase binding assay and surface plasmon resonance (SPR) spectroscopy. Confocal microscopy showed regions of co-localisation of Hsp90 and FN in breast cancer cell lines. Exogenous Hsp90β was shown to increase the formation of extracellular FN matrix in the Hs578T cell line, whilst knockdown or inhibition of Hsp90 led to a reduction in the levels of both soluble and insoluble FN and could be partially rescued by addition of exogenous Hsp90β. Treatment of cells with novobiocin led to internalization of FN into vesicles that were positive for the presence of the lysosomal marker, LAMP-1. Taken together, the direct interaction between FN and Hsp90, as well as the decreased levels of both soluble and insoluble FN upon Hsp90 inhibition or knockdown, suggested that FN may be a new client protein for Hsp90 and that Hsp90 was involved in FN matrix assembly and/or stability. The identification of FN as a putative client protein of Hsp90 suggests a role for Hsp90 in FN matrix stability, which is important for a number of fundamental cellular processes including embryogenesis, wound healing, cell migration and metastasis.

Fibronectin matrix assembly is essential for cell condensation during chondrogenesis.

Mesenchymal cell condensation is the initiating event in endochondral bone formation. Cell condensation is followed by differentiation into chondrocytes, which is accompanied by induction of chondrogenic gene expression. Gene mutations involved in chondrogenesis cause chondrodysplasias and other skeletal defects. Using mesenchymal stem cells (MSCs) in an in vitro chondrogenesis assay, we found that knockdown of the diastrophic dysplasia (DTD) sulfate transporter (DTDST, also known as SLC26A2), which is required for normal cartilage development, blocked cell condensation and caused a significant reduction in fibronectin matrix. Knockdown of fibronectin with small interfering RNAs (siRNAs) also blocked condensation. Fibrillar fibronectin matrix was detected prior to cell condensation, and its levels increased during and after condensation. Inhibition of fibronectin matrix assembly by use of the functional upstream domain (FUD) of adhesin F1 from Streptococcus pyogenes prevented cell condensation by MSCs and also by the chondrogenic cell line ATDC5. Our data show that cell condensation and induction of chondrogenesis depend on fibronectin matrix assembly and DTDST, and indicate that this transporter is required earlier in chondrogenesis than previously appreciated. They also raise the possibility that certain of the skeletal defects in DTD patients might derive from the link between DTDST, fibronectin matrix and condensation.

Conformational remodeling of the fibronectin matrix selectively regulates VEGF signaling.

The fibronectin matrix plays a crucial role in the regulation of angiogenesis during development, tissue repair and pathogenesis. Previous work has identified a fibronectin-derived homophilic binding peptide, anastellin, as an effective inhibitor of angiogenesis; however, its mechanism of action is not well understood. In the present study, we demonstrate that anastellin selectively inhibits microvessel cell signaling in response to the VEGF165 isoform, but not VEGF121, by preventing the assembly of the complex containing the VEGF receptor and neuropilin-1. Anastellin treatment resulted in the inactivation of α5β1 integrins but was not accompanied by a change in either adhesion complexes or adhesion-based signaling. Integrin inactivation was associated with a masking of the fibronectin synergy site within the extracellular matrix (ECM), indicating that α5β1 inactivation resulted from a decrease in available ligand. These data demonstrate that anastellin influences the microvessel cell response to growth factors by controlling the repertoire of ligated integrins and point to anastellin as an effective regulator of fibronectin matrix organization. These studies further suggest that homophilic fibronectin binding peptides might have novel applications in the field of tissue regeneration as tools to regulate neovascularization.

Surface-Bound Vascular Endothelial Growth Factor Promotes Prolonged Activation of Endothelial Cells: A New Technology for Capturing Endothelial Progenitor Cells by Intravascular Stents

In -situ selective capture of the Endothelial Progenitor Cell (EPC) in the arterial blood stream can provide antithrombogenic and -cell proliferation potential to implanted intravascular stents. Therefore, we defined molecular mechanisms of EPC activation associated with stent surface-bound proteins. We sought suitable bound protein to capture and proliferate EPCs. Then, to determine whether and how long the surface-bound protein activates intracellular signal-transduction pathways of endothelial cells through its receptor, we studied the phosphorylation of key intracellular macromolecules including Vascular Endothelial Growth Factor (VEGF) Receptor (R)-2 (VEGFR-2), focal adhesion protein-tyrosine kinase, Akt, and extracellular signal-regulated kinase in human umbilical vein endothelial cells. We found the most suitable surface-bound protein was VEGF. Phosphorylation of these macromolecules continued for a long time up to 72 hours. Under these conditions, quantitative RT-PCR revealed time-dependent up-regulation of the mRNAs encoding three major extracellular matrix macromolecules, collagen IV, laminin-5, and fibronectin. Immuno histo- chemical analysis revealed that these macromolecules were secreted on the basal sides of adherent cells over time and that within a few days after initial adhesion occurred, deposition of these macromolecules shut down the EC adhesion. These results demonstrate that activation of the VEGF-VEGFR intracellular signaling pathway is significant for in situ EPC capture technology for intravascular stents, although further in vivo studies should be done to confirm these processes.

An Extracellular Matrix Molecule, Secreted by the Epithelial-Mesenchymal Transition is Associated With Lymph Node Metastasis of Thyroid Papillary Carcinoma

Background:Papillary thyroid carcinoma often has lymph node metastasis, compared with follicular thyroid carcinoma. The study showed that epithelial-mesenchymal transition occurs in carcinoma cells during the first stage of metastasis, where some extracellular matrix molecules are secreted in large quantities. Sialic acid carried by fibronectin as the antigen of the monoclonal antibody (MoAb) JT-95, was detected in 90% of papillary thyroid carcinoma cases, and in a few follicular thyroid carcinomas, in the extracellular matrix of thyroid carcinoma cells.Objectives:The current study was conducted to investigate the association between increasing the number of extracellular matrix molecules, fibronectin, and lymph node metastasis. We also co-cultured a thyroid carcinoma cell line and lymphocyte cell line, with and without MoAb JT-95, in order to investigate the mechanism of cell to cell interaction.Patients and Methods:Immunostaining with JT-95 was performed in 45 papillary thyroid carcinoma cases, and 20 follicular type tumors, to investigate the association between the quantity of fibronectin expression and the frequency of lymph node metastasis. The thyroid carcinoma cell line (SW1736), which secreted fibronectin, and the B cell-lymphoma cell line (Daudi), which held integrin on the cell surface, were co-cultured to observe the adhesion of cells to each other. The SW1736 cell line, pretreated with JT-95, was also co-cultured with the Daudi cell line.Results:There were 39 cases with lymph node metastasis in 59 malignant tumors, and 0 cases in 6 benign follicular type tumors. The staining scores by JT-95 of the 39 tumors with lymph node metastasis were 5+ in eight cases and 6+ in 31 cases. On the other hand, the scores of 20 malignant tumors without lymph node metastasis were < 4+ in all of the cases. In the co-cultured assay, numerous adhesions were observed between the SW1736 and Daudi cells. In contrast, the inhibition of adherences was observed in proportion to the concentrations of JT-95.Conclusions:Increased fibronectin expression in thyroid malignancies is correlated with lymph node metastasis.

Epithelial bridges maintain tissue integrity during collective cell migration

The ability of skin to act as a barrier is primarily determined by the efficiency of skin cells to maintain and restore its continuity and integrity. In fact, during wound healing keratinocytes migrate collectively to maintain their cohesion despite heterogeneities in the extracellular matrix. Here, we show that monolayers of human keratinocytes migrating along functionalized micropatterned surfaces comprising alternating strips of extracellular matrix (fibronectin) and non-adherent polymer form suspended multicellular bridges over the non-adherent areas. The bridges are held together by intercellular adhesion and are subjected to considerable tension, as indicated by the presence of prominent actin bundles. We also show that a model based on force propagation through an elastic material reproduces the main features of bridge maintenance and tension distribution. Our findings suggest that multicellular bridges maintain tissue integrity during wound healing when cell-substrate interactions are weak and may prove helpful in the design of artificial scaffolds for skin regeneration.

Estrogen-mediated activation of fibroblasts and its effects on the fibroid cell proliferation

In this study, we explored the role of estrogen-mediated activation of stromal fibroblasts in the pathogenesis of uterine fibroid in patients. We isolated uterine fibroids and surrounding smooth muscle from patients and separated fibroblasts using immunomagnetic beads. We also measured the expression levels of estrogen receptors in fibroblasts and examined cell proliferation, expressions of fibroblast activation protein (FAP), extracellular matrix (ECM) (fibronectin, laminin, collagen I), growth factors (transforming growth factor-β, insulin-like growth factor-1), and cell proliferation pathway stimulated by estrogen. We also silenced the expression of FAP by RNA interference and analyzed the expression levels of these markers before and after E2 stimulation. Finally, we also investigated the effect of activated fibroblast supernatant on cell proliferation of fibroblasts, smooth muscle cells, and fibroid cells. We found that fibroblasts in uterine fibroid were activated, and the expression levels of estrogen receptors from fibroid cells were higher than those from smooth muscle cells. After estrogen stimulation, the proliferation activity of fibroblast was enhanced, and the expression of FAP, ECM, and growth factors was increased; the signaling pathway involved in cell proliferation was also activated. Interestingly, the activated fibroblast supernatant stimulation can promote cell proliferation. Silencing of FAP expression could inhibit the E2-mediated biological effects. In conclusion, estrogen promotes proliferation of uterine fibroids through the activation of fibroblasts, thus, activated fibroblasts may play an important role in the pathogenesis of uterine fibroids, which could be targeted in future for the treatment of uterine fibroid.

Platelet P2Y12 Is Involved in Murine Pulmonary Metastasis

The involvement of platelets in tumor progression is well recognized. The depletion of circulating platelets or pharmacologic inhibitors of platelet activation decreases the metastatic potential of circulating tumor cells in metastasis mouse models. The platelet ADP receptor P2Y12 amplifies the initial hemostatic responses activated by a variety of platelet agonists and stabilizes platelet aggregation, playing a crucial role in granule secretion, integrin activation and thrombus formation. However, the relationship between P2Y12 and tumor progression is not clear. In our study, the Lewis Lung Carcinoma (LLC) spontaneous metastatic mouse model was used to evaluate the role of P2Y12 in metastasis. The results demonstrated that P2Y12 deficiency significantly reduced pulmonary metastasis. Further studies indicated that P2Y12 deficiency diminished the ability of LLC cells to induce platelet shape change and release of active TGFβ1 by a non-contact dependent mechanism resulting in a diminished, platelet-induced EMT-like transformation of the LLC cells, and that transformation probably is a prerequisite of LLC cell metastasis. Immunohistochemical analyses indicated an obvious P2Y12 deficiency related attenuation of recruitment of VEGFR1+ bone marrow derived cell clusters, and extracellular matrix fibronectin deposition in lungs, which presumably are required for pre-metastatic niche formation. In contrast to the LLC cells, non-epithelial melanoma B16 cells induced platelet aggregation in a cell number and P2Y12-dependent manner. Also, a platelet induced EMT-like transformation of B16 cells is dependent on P2Y12. In agreement with the LLC cell model, platelet P2Y12 deficiency also results in significantly less lung metastasis in the B16 melanoma experimental metastasis model. These results demonstrate that P2Y12 is a safe drug target for anti-thrombotic therapy, and that P2Y12 may serve as a new target for inhibition of tumor metastasis.

PAX3 in neuroblastoma: oncogenic potential, chemosensitivity and signalling pathways

Transcription factor PAX3/Pax3 contributes to diverse cell lineages during embryonic development and is important in tumourigenesis. We found that PAX3 is re-expressed in neuroblastoma and malignant neuroblastic (N-type) neuroblastoma cells had significantly higher PAX3 protein expression than their benign substrate-adherent (S-type) counterparts. Knock-down of PAX3 expression by siRNA transfection resulted in persistent cell growth inhibition in both types of neuroblastoma cell, owing to G1 cell cycle arrest and progressive apoptosis. Inhibition of PAX3 expression significantly decreased the attachment of S-type SH-EP1 cells to extra-cellular matrix proteins, fibronectin, laminin and collagen IV. Migration and invasion of both neuroblastoma cell types were markedly reduced after PAX3 down-regulation. PAX3 knock-down significantly augmented the cytotoxic effect of chemotherapeutic agents, etoposide, vincristine and cisplatin, commonly used to treat neuroblastoma. Microarray analyses revealed that particularly signalling pathways involving cell cycle, apoptosis, cell adhesion, cytoskeletal remodelling and development were altered by PAX3 down-regulation. Changes in PAX3 downstream genes identified by microarray analyses were validated in 47 genes by quantitative PCR. These novel findings lead us to propose that PAX3 might contribute to oncogenic characteristics of neuroblastoma cells by regulating a variety of crucial signalling pathways.

HER-2/neu Mediates Oncogenic Transformation via Altered CREB Expression and Function

The cyclic (c)AMP responsive element binding protein (CREB) plays a key role in many cellular processes, including differentiation, proliferation, and signal transduction. Furthermore, CREB overexpression was found in tumors of distinct origin and evidence suggests an association with tumorigenicity. To establish a mechanistic link between HER-2/neu-mediated transformation and CREB protein expression and function, in vitro models of HER-2/neu-overexpressing and HER-2/neu-negative/silenced counterparts as well as human mammary carcinoma lesions with defined HER-2/neu status were used. HER-2/neu overexpression resulted in the induction and activation of CREB protein in vitro and in vivo, whereas short hairpin RNA (shRNA)-mediated inhibition of HER-2/neu correlated with downregulated CREB activity. CREB activation in HER-2/neu-transformed cells enhanced distinct signal transduction pathways, whereas their inhibition negatively interfered with CREB expression and/or activation. CREB downregulation in HER-2/neu-transformed cells by shRNA and by the inhibitors KG-501 and lapatinib caused morphologic changes, reduced cell proliferation with G0-G1 cell-cycle arrest, which was rescued by CREB expression. This was accompanied by reduced cell migration, wound healing, an increased fibronectin adherence, invasion, and matrix metalloproteinase expression. In vivo shCREB-HER-2/neu(+) cells, but not control cells, exerted a significantly decreased tumorgenicity that was associated with decreased proliferative capacity, enhanced apoptosis, and increased frequency of T lymphocytes in peripheral blood mononuclear cells. Thus, CREB plays an important role in the HER-2/neu-mediated transformation by altering in vitro and in vivo growth characteristics. These data suggest that CREB affects tumor immunogenicity and is a potential target for cancer therapy.

The Hippo signaling pathway is required for salivary gland development and its dysregulation is associated with Sjogren's syndrome

Sjogren's syndrome (SS) is a complex autoimmune disease that primarily affects salivary and lacrimal glands and is associated with high morbidity. Although the prevailing dogma is that immune system pathology drives SS, increasing evidence points to structural defects, including defective E-cadherin adhesion, to be involved in its etiology. We have shown that E-cadherin has pivotal roles in the development of the mouse salivary submandibular gland (SMG) by organizing apical-basal polarity in acinar and ductal progenitors and by signaling survival for differentiating duct cells. Recently, E-cadherin junctions have been shown to interact with effectors of the Hippo signaling pathway, a core pathway regulating the organ size, cell proliferation, and differentiation. We now show that Hippo signaling is required for SMG-branching morphogenesis and is involved in the pathophysiology of SS. During SMG development, a Hippo pathway effector, TAZ, becomes increasingly phosphorylated and associated with E-cadherin and α-catenin, consistent with the activation of Hippo signaling. Inhibition of Lats2, an upstream kinase that promotes TAZ phosphorylation, results in dysmorphogenesis of the SMG and impaired duct formation. SMGs from non-obese diabetic mice, a mouse model for SS, phenocopy the Lats2-inhibited SMGs and exhibit a reduction in E-cadherin junctional components, including TAZ. Importantly, labial specimens from human SS patients display mislocalization of TAZ from junctional regions to the nucleus, coincident with accumulation of extracellular matrix components, fibronectin and connective tissue growth factor, known downstream targets of TAZ. Our studies show that Hippo signaling has a crucial role in SMG-branching morphogenesis and provide evidence that defects in this pathway are associated with SS in humans.