Matrix metalloproteinase-19 deficiency promotes tenascin-C accumulation and allergen-induced airway inflammation

Mucosal-associated invariant T cells repress group 2 innate lymphoid cells in Alternaria alternata-induced model of allergic airway inflammation

Mucosal-associated invariant T (MAIT) cells, a blossoming member of the innate-like T cells, play a pivotal role in host defense through engaging the mucosal immunity. Although it has been suggested that MAIT cells are somehow implicated in the allergic airway inflammation mediated by group 2 innate lymphoid cells (ILC2s) such as asthma, the precise role(s) of MAIT cells in such inflammation has remained elusive. To explore the possible roles of MAIT cells in the inflammation, we examined whether MAIT cells suppressed the production of T helper (Th) 2 and inflammatory cytokines from ILC2s, and constrained the proliferation of ILC2s, both of which are prerequisite for airway inflammation. Given that laboratory mice are poor at MAIT cells, a novel mouse line rich in MAIT cells was used. We found that mice rich in MAIT cells showed alleviated airway inflammation as evidenced by reduced infiltration of the immune cells and hyperplasia in goblet cells in the lung concomitant with compromised production of Th2 and inflammatory cytokines, while wild type mice exhibited severe inflammation upon challenge with the fungal extracts. In vitro coculture experiments using purified ILC2s and MAIT cells unrevealed that cytokine-stimulated MAIT cells suppressed ILC2s to produce the cytokines as well as to proliferate most likely via production of IFN-γ. Furthermore, reconstitution of the allergic airway inflammation in the highly immunocompromised mice showed that ILC2-mediated inflammation was alleviated in mice that received MAIT cells along with ILC2s. We concluded that MAIT cells played a crucial role in suppressing the cytokine-producing capacity of ILC2s and ILC2 proliferation, that ultimately led to decrease in the allergic airway inflammation. The results open up a novel therapeutic horizon in ILC2-mediated inflammatory diseases by modulating MAIT cell activity.

Matrix Metalloproteinases: From Molecular Mechanisms to Physiology, Pathophysiology, and Pharmacology

The first matrix metalloproteinase (MMP) was discovered in 1962 from the tail of a tadpole by its ability to degrade collagen. As their name suggests, matrix metalloproteinases are proteases capable of remodeling the extracellular matrix. More recently, MMPs have been demonstrated to play numerous additional biologic roles in cell signaling, immune regulation, and transcriptional control, all of which are unrelated to the degradation of the extracellular matrix. In this review, we will present milestones and major discoveries of MMP research, including various clinical trials for the use of MMP inhibitors. We will discuss the reasons behind the failures of most MMP inhibitors for the treatment of cancer and inflammatory diseases. There are still misconceptions about the pathophysiological roles of MMPs and the best strategies to inhibit their detrimental functions. This review aims to discuss MMPs in preclinical models and human pathologies. We will discuss new biochemical tools to track their proteolytic activity in vivo and ex vivo, in addition to future pharmacological alternatives to inhibit their detrimental functions in diseases. SIGNIFICANCE STATEMENT: Matrix metalloproteinases (MMPs) have been implicated in most inflammatory, autoimmune, cancers, and pathogen-mediated diseases. Initially overlooked, MMP contributions can be both beneficial and detrimental in disease progression and resolution. Thousands of MMP substrates have been suggested, and a few hundred have been validated. After more than 60 years of MMP research, there remain intriguing enigmas to solve regarding their biological functions in diseases.

Obesity-Induced Changes in Bone Marrow Homeostasis

Obesity is characterized by low-grade inflammation, which is accompanied by increased accumulation of immune cells in peripheral tissues including adipose tissue (AT), skeletal muscle, liver and pancreas, thereby impairing their primary metabolic functions in the regulation of glucose homeostasis. Obesity has also shown to have a detrimental effect on bone homeostasis by altering bone marrow and hematopoietic stem cell differentiation and thus impairing bone integrity and immune cell properties. The origin of immune cells arises in the bone marrow, which has been shown to be affected with the obesogenic condition via increased cellularity and shifting differentiation and function of hematopoietic and bone marrow mesenchymal stem cells in favor of myeloid progenitors and increased bone marrow adiposity. These obesity-induced changes in the bone marrow microenvironment lead to dramatic bone marrow remodeling and compromising immune cell functions, which in turn affect systemic inflammatory conditions and regulation of whole-body metabolism. However, there is limited information on the inflammatory secretory factors creating the bone marrow microenvironment and how these factors changed during metabolic complications. This review summarizes recent findings on inflammatory and cellular changes in the bone marrow in relation to obesity and further discuss whether dietary intervention or physical activity may have beneficial effects on the bone marrow microenvironment and whole-body metabolism.

The solid-state fermentation of Artemisia capillaris leaves with Ganoderma lucidum enhances the anti-inflammatory effects in a model of atopic dermatitis

Artemisia capillaris, which belongs to the Asteraceae family and the genus Artemisia, has been reported to exert inhibitory effects on diabetes, cancer and inflammation. In this study, in order to enhance the bioactivity potential of the leaves of Artemisia by Ganoderma lucidum mycelium, we prepared aqueous samples of Artemisia capillaris (Ac) leaves, Ganoderma lucidum (Gl) and aqueous fractions produced by the solid fermentation of Ganoderma lucidum on Artemisia capillaris leaves (afAc/Gl). Thereafter, we evaluated whether these samples have potential to attenuate inflammation-related symptoms in an amimal model of 2,4-dinitrofluorobenzene (DNFB)-induced atopic dermatitis. We found that afAc/Gl exhibited enhanced anti-inflamamatory activity following the solid fermentation process when compared with Ac or Gl on ear thickness, ear epidermal thickness and eosinophil infiltration in the skin tissues. The expression of nitric oxide (NO) synthases (NOSs) was measured by immunohistochemical staining. The results revealed that afAc/Gl decreased endothelial NOS and inducible NOS expression compared with the DNFB group, while neuronal NOS expression was not altered. By comparing NO production, we found that as opposed to Ac, afAc/Gl has potential to inhibit atopic dermatitis-related symptoms during the inflammatory event. As regards matrix metalloproteinase (MMP) expression patterns, afAc/Gl exerted potent inhibitory activity on the mRNA expression of MMP-2, -7, -9, -12, -14 and -19. Taken together, these results suggest that the solid state fermentation of Ac by Gl is an effective strategy to obtaining useful ingredients which are converted into valuable compounds during an atopic inflammatory insult.

Tenascin-C deficiency protects mice from experimental autoimmune encephalomyelitis

The extracellular matrix glycoprotein tenascin-C (TnC) has been increasingly appreciated as a molecule susceptibly reacting to abnormalities in the mammalian immune system. TnC expression is elevated in inflamed tissues outside the immune system, but also in lymphoid organs. It participates in the promotion of inflammatory responses. Here, the role of TnC in a paradigm of CNS autoimmunity was investigated. Experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, was induced in mice deficient in TnC (TnC^-/- mice). Amelioration of EAE was observed in these mice in comparison to their wild-type (TnC^+/+) littermates. Since T helper (Th)1 and Th17 cells play a dominant role in the pathogenesis of EAE, these cells were investigated in addition to analyzing locomotor functions and pro-inflammatory cytokine levels. Smaller numbers of interferon-gamma-producing Th1 cells and reduced ability of Th17 cells to produce interleukin-17 were observed in spleens of TnC^-/- mice challenged by immunization with the myelin associated glycoprotein (MOG) when compared to TnC^+/+ mice. There was no difference in Th1 and Th17 responses in non-immunized TnC^-/- and TnC^+/+ mice, thus excluding generalized immunosuppression in TnC^-/- mice. These results show that TnC is important for the pathogenesis of CNS autoimmunity and that its deficiency interferes with Th1 and Th17 encephalitogenic potentials.

Extracellular molecules in hematopoietic stem cell mobilisation

Hematopoietic stem cells are a remarkable resource currently used for the life saving treatment, hematopoietic stem cell transplantation. Today, hematopoietic stem cells are primarily obtained from mobilized peripheral blood following treatment of the donor with the cytokine G-CSF, and in some settings, chemotherapy and/or the CXCR4 antagonist plerixafor. The collection of hematopoietic stem cells is contingent on adequate and timely mobilization of these cells into the peripheral blood. The use of healthy donors, particularly when unrelated to the patient, requires mobilization strategies be safe for the donor. While current mobilization strategies are largely successful, adequate mobilization fails to occur in a significant portion of donors. Understanding the mechanisms involved in the egress of stem cells from the bone marrow provides opportunities to further improve the process of collecting hematopoietic stem cells. Here, the role extracellular components of the blood and bone marrow in the mobilization process are discussed.

MMP-19 deficiency causes aggravation of colitis due to defects in innate immune cell function

Matrix metalloproteinases (MMPs) are potential biomarkers for disease activity in inflammatory bowel disease (IBD). However, clinical trials targeting MMPs have not succeeded, likely due to poor understanding of the biological functions of individual MMPs. Here, we explore the role of MMP-19 in IBD pathology. Using a DSS-induced model of colitis, we show evidence for increased susceptibility of Mmp-19-deficient (Mmp-19(-/-)) mice to colitis. Absence of MMP-19 leads to significant disease progression, with reduced survival rates, severe tissue destruction, and elevated levels of pro-inflammatory modulators in the colon and plasma, and failure to resolve inflammation. There was a striking delay in neutrophil infiltration into the colon of Mmp-19(-/-) mice during the acute colitis, leading to persistent inflammation and poor recovery; this was rescued by reconstitution of irradiated Mmp-19(-/-) mice with wild-type bone marrow. Additionally, Mmp-19-deficient macrophages exhibited decreased migration in vivo and in vitro and the mucosal barrier appeared compromised. Finally, chemokine fractalkine (CX3CL1) was identified as a novel substrate of MMP-19, suggesting a link between insufficient processing of CX3CL1 and cell recruitment in the Mmp-19(-/-) mice. MMP-19 proves to be a critical factor in balanced host response to colonic pathogens, and for orchestrating appropriate innate immune response in colitis.

Tenascin-C: Form versus function

Tenascin-C is a large, multimodular, extracellular matrix glycoprotein that exhibits a very restricted pattern of expression but an enormously diverse range of functions. Here, we discuss the importance of deciphering the expression pattern of, and effects mediated by, different forms of this molecule in order to fully understand tenascin-C biology. We focus on both post transcriptional and post translational events such as splicing, glycosylation, assembly into a 3D matrix and proteolytic cleavage, highlighting how these modifications are key to defining tenascin-C function.

Downregulation of matrix metalloproteinase‑19 induced by respiratory syncytial viral infection affects the interaction between epithelial cells and fibroblasts

The present study was designed to examine the expression and function of matrix metalloproteinase-19 (MMP-19), which is downregulated following respiratory syncytial virus (RSV) infection. The diverse expression levels of MMP were examined using a designed cDNA expression array. The expression and secretion of MMP-19 was examined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis and ELISA, respectively. The proliferation of epithelial cells and lung fibroblasts were examined using flow cytometry. The epithelial-mesenchymal transition (EMT) was also examined by performing western blot and RT-qPCR analyses. The results of the cDNA assay showed that infection with RSV resulted in the abnormal expression of certain metalloproteinases. Among these, the expression of MMP-19 decreased 3 and 7 days following infection. By using flow cytometric, western blot and RT-qPCR analyses, the present study demonstrated that the downregulation of MMP-19 inhibited the proliferation of epithelial cells, promoted the EMT and induced the proliferation of lung fibroblasts. Taken together, the findings of the present study suggested that the downregulation of MMP-19 following RSV infection may be associated with the development of airway hyper-responsiveness.

Metalloproteinases promote plaque rupture and myocardial infarction: A persuasive concept waiting for clinical translation

Atherosclerotic plaque rupture provokes most myocardial infarctions. Matrix metalloproteinases (MMPs) have counteracting roles in intimal thickening, which stabilizes plaques, on the one hand and extracellular matrix destruction that leads to plaque rupture on the other. This review briefly summarizes the key points supporting the involvement of individual MMPs in provoking plaque rupture and discusses the barriers that stand in the way of clinical translation, which can be itemised as follows: structural and functional complexity of the MMP family; lack of adequate preclinical models partly owing to different expression patterns of MMPs and TIMPs in mouse and human macrophages; the need to target individual MMPs selectively; the difficulties in establishing causality in human studies; and the requirement for surrogate markers of efficacy. Overcoming these barriers would open the way to new treatments that could have a major impact on cardiovascular mortality worldwide.

IL-17A mediates a selective gene expression profile in asthmatic human airway smooth muscle cells

Airway smooth muscle (ASM) cells are thought to contribute to the pathogenesis of allergic asthma by orchestrating and perpetuating airway inflammation and remodeling responses. In this study, we evaluated the IL-17RA signal transduction and gene expression profile in ASM cells from subjects with mild asthma and healthy individuals. Human primary ASM cells were treated with IL-17A and probed by the Affymetrix GeneChip array, and gene targets were validated by real-time quantitative RT-PCR. Genomic analysis underlined the proinflammatory nature of IL-17A, as multiple NF-κB regulatory factors and chemokines were induced in ASM cells. Transcriptional regulators consisting of primary response genes were overrepresented and displayed dynamic expression profiles. IL-17A poorly enhanced IL-1β or IL-22 gene responses in ASM cells from both subjects with mild asthma and healthy donors. Interestingly, protein modifications to the NF-κB regulatory network were not observed after IL-17A stimulation, although oscillations in IκBε expression were detected. ASM cells from subjects with mild asthma up-regulated more genes with greater overall variability in response to IL-17A than from healthy donors. Finally, in response to IL-17A, ASM cells displayed rapid activation of the extracellular signal-regulated kinase/ribosomal S6 kinase signaling pathway and increased nuclear levels of phosphorylated extracellular signal-regulated kinase. Taken together, our results suggest that IL-17A mediated modest gene expression response, which, in cooperation with the NF-κB signaling network, may regulate the gene expression profile in ASM cells.

Matrix metalloproteinases in inflammation

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of ubiquitously expressed zinc-dependent endopeptidases with broad substrate specificity and strictly regulated tissue specific expression. They are expressed in physiological situations and pathological conditions involving inflammation. MMPs regulate several functions related to inflammation including bioavailability and activity of inflammatory cytokines and chemokines. There is also evidence that MMPs regulate inflammation in tumor microenvironment, which plays an important role in cancer progression.

SCOPE OF REVIEW

Here, we discuss the current view on the role of MMPs in the regulation of inflammation.

MAJOR CONCLUSIONS

MMPs modulate inflammation by regulating bioavailability and activity of cytokines, chemokines, and growth factors, as well as integrity of physical tissue barriers. MMPs are also involved in immune evasion of tumor cells and in regulation of inflammation in tumor microenvironment.

GENERAL SIGNIFICANCE

There is increasing evidence for non-matrix substrates of MMPs that are related to regulation of inflammatory processes. New methods have been employed for identification of the substrates of MMPs in inflammatory processes in vivo. Detailed information on the substrates of MMPs may offer more specific and effective ways of inhibiting MMP function by blocking the cleavage site in substrate or by inhibition of the bioactivity of the substrate. It is expected, that more precise information on the MMP-substrate interaction may offer novel strategies for therapeutic intervention in inflammatory diseases and cancer without blocking beneficial actions of MMPs. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Hepatoprotective effect of MMP-19 deficiency in a mouse model of chronic liver fibrosis

Liver fibrosis is characterized by the deposition and increased turnover of extracellular matrix. This process is controlled by matrix metalloproteinases (MMPs), whose expression and activity dynamically change during injury progression. MMP-19, one of the most widely expressed MMPs, is highly expressed in liver; however, its contribution to liver pathology is unknown. The aim of this study was to elucidate the role of MMP-19 during the development and resolution of fibrosis by comparing the response of MMP-19-deficient (MMP19KO) and wild-type mice upon chronic liver CCl(4)-intoxication. We show that loss of MMP-19 was beneficial during liver injury, as plasma ALT and AST levels, deposition of fibrillar collagen, and phosphorylation of SMAD3, a TGF-ß1 signaling molecule, were all significantly lower in MMP19KO mice. The ameliorated course of the disease in MMP19KO mice likely results from a slower rate of basement membrane destruction and ECM remodeling as the knockout mice maintained significantly higher levels of type IV collagen and lower expression and activation of MMP-2 after 4 weeks of CCl(4)-intoxication. Hastened liver regeneration in MMP19KO mice was associated with slightly higher IGF-1 mRNA expression, slightly increased phosphorylation of Akt kinase, decreased TGF-ß1 mRNA levels and significantly reduced SMAD3 phosphorylation. In addition, primary hepatocytes isolated from MMP19KO mice showed impaired responsiveness towards TGF-ß1 stimulation, resulting in lower expression of Snail1 and vimentin mRNA. Thus, MMP-19-deficiency improves the development of hepatic fibrosis through the diminished replacement of physiological extracellular matrix with fibrotic deposits in the beginning of the injury, leading to subsequent changes in TGF-ß and IGF-1 signaling pathways.

Control of allergen-induced inflammation and hyperresponsiveness by the metalloproteinase ADAMTS-12

A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) constitute a family of endopeptidases related to matrix metalloproteinases. These proteinases have been largely implicated in tissue remodeling associated with pathological processes. Among them, ADAMTS12 was identified as an asthma-associated gene in a human genome screening program. However, its functional implication in asthma is not yet documented. The present study aims at investigating potential ADAMTS-12 functions in experimental models of allergic airways disease. Two different in vivo protocols of allergen-induced airways disease were applied to the recently generated Adamts12-deficient mice and corresponding wild-type mice. In this study, we provide evidence for a protective effect of ADAMTS-12 against bronchial inflammation and hyperresponsiveness. In the absence of Adamts12, challenge with different allergens (OVA and house dust mite) led to exacerbated eosinophilic inflammation in the bronchoalveolar lavage fluid and in lung tissue, along with airway dysfunction assessed by increased airway responsiveness following methacholine exposure. Furthermore, mast cell counts and ST2 receptor and IL-33 levels were higher in the lungs of allergen-challenged Adamts12-deficient mice. The present study provides, to our knowledge, the first experimental evidence for a contribution of ADAMTS-12 as a key mediator in airways disease, interfering with immunological processes leading to inflammation and airway hyperresponsiveness.

Nebulized anti-IL-13 monoclonal antibody Fab' fragment reduces allergen-induced asthma

IL-13 is a prototypic T helper type 2 cytokine and a central mediator of the complex cascade of events leading to asthmatic phenotype. Indeed, IL-13 plays key roles in IgE synthesis, bronchial hyperresponsiveness, mucus hypersecretion, subepithelial fibrosis, and eosinophil infiltration. We assessed the potential efficacy of inhaled anti-IL-13 monoclonal antibody Fab' fragment on allergen-induced airway inflammation, hyperresponsiveness, and remodeling in an experimental model of allergic asthma. Anti-IL-13 Fab' was administered to mice as a liquid aerosol generated by inExpose inhalation system in a tower allowing a nose-only exposure. BALB/c mice were treated by PBS, anti-IL-13 Fab', or A33 Fab' fragment and subjected to ovalbumin exposure for 1 and 5 weeks (short-term and long-term protocols). Our data demonstrate a significant antiasthma effect after nebulization of anti-IL-13 Fab' in a model of asthma driven by allergen exposure as compared with saline and nonimmune Fab fragments. In short- and long-term protocols, administration of the anti-IL-13 Fab' by inhalation significantly decreased bronchial responsiveness to methacholine, bronchoalveolar lavage fluid eosinophilia, inflammatory cell infiltration in lung tissue, and many features of airway remodeling. Levels of proinflammatory mediators and matrix metalloprotease were significantly lower in lung parenchyma of mice treated with anti-IL-13 Fab'. These data demonstrate that an inhaled anti-IL-13 Fab' significantly reduces airway inflammation, hyperresponsiveness, and remodeling. Specific neutralization of IL-13 in the lungs using an inhaled anti-IL-13 Fab' could represent a novel and effective therapy for the treatment of asthma.

Classical macrophage activation up-regulates several matrix metalloproteinases through mitogen activated protein kinases and nuclear factor-κB

Remodelling of the extracellular matrix (ECM) and cell surface by matrix metalloproteinases (MMPs) is an important function of monocytes and macrophages. Recent work has emphasised the diverse roles of classically and alternatively activated macrophages but the consequent regulation of MMPs and their inhibitors has not been studied comprehensively. Classical activation of macrophages derived in vitro from un-fractionated CD16^+/− or negatively-selected CD16⁻ macrophages up-regulated MMP-1, -3, -7, -10, -12, -14 and -25 and decreased TIMP-3 steady-state mRNA levels. Bacterial lipopolysaccharide, IL-1 and TNFα were more effective than interferonγ except for the effects on MMP-25, and TIMP-3. By contrast, alternative activation decreased MMP-2, -8 and -19 but increased MMP -11, -12, -25 and TIMP-3 steady-state mRNA levels. Up-regulation of MMPs during classical activation depended on mitogen activated protein kinases, phosphoinositide-3-kinase and inhibitor of κB kinase-2. Effects of interferonγ depended on janus kinase-2. Where investigated, similar effects were seen on protein concentrations and collagenase activity. Moreover, activity of MMP-1 and -10 co-localised with markers of classical activation in human atherosclerotic plaques in vivo. In conclusion, classical macrophage activation selectively up-regulates several MMPs in vitro and in vivo and down-regulates TIMP-3, whereas alternative activation up-regulates a distinct group of MMPs and TIMP-3. The signalling pathways defined here suggest targets for selective modulation of MMP activity.

Matrix metalloproteinase-19 is a key regulator of lung fibrosis in mice and humans

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by epithelial phenotypic changes and fibroblast activation. Based on the temporal heterogeneity of IPF, we hypothesized that hyperplastic alveolar epithelial cells regulate the fibrotic response.

OBJECTIVES

To identify novel mediators of fibrosis comparing the transcriptional signature of hyperplastic epithelial cells and conserved epithelial cells in the same lung.

METHODS

Laser capture microscope and microarrays analysis were used to identify differentially expressed genes in IPF lungs. Bleomycin-induced lung fibrosis was evaluated in Mmp19-deficient and wild-type (WT) mice. The role of matrix metalloproteinase (MMP)-19 was additionally studied by transfecting the human MMP19 in alveolar epithelial cells.

MEASUREMENTS AND MAIN RESULTS

Laser capture microscope followed by microarray analysis revealed a novel mediator, MMP-19, in hyperplastic epithelial cells adjacent to fibrotic regions. Mmp19(-/-) mice showed a significantly increased lung fibrotic response to bleomycin compared with WT mice. A549 epithelial cells transfected with human MMP19 stimulated wound healing and cell migration, whereas silencing MMP19 had the opposite effect. Gene expression microarray of transfected A549 cells showed that PTGS2 (prostaglandin-endoperoxide synthase 2) was one of the highly induced genes. PTGS2 was overexpressed in IPF lungs and colocalized with MMP-19 in hyperplastic epithelial cells. In WT mice, PTGS2 was significantly increased in bronchoalveolar lavage and lung tissues after bleomycin-induced fibrosis, but not in Mmp19(-/-) mice. Inhibition of Mmp-19 by siRNA resulted in inhibition of Ptgs2 at mRNA and protein levels.

CONCLUSIONS

Up-regulation of MMP19 induced by lung injury may play a protective role in the development of fibrosis through the induction of PTGS2.

The role of vitamin D in asthma

Vitamin D metabolites are important immune-modulatory hormones and are able to suppress Th2-mediated allergic airway disease. Some genetic factors that may contribute to asthma are regulated by vitamin D, such as vitamin D receptor (VDR), human leukocyte antigen genes (HLA), human Toll-like receptors (TLR), matrix metalloproteinases (MMPs), a disintegrin and metalloprotein-33 (ADAM-33), and poly(ADP-ribosyl) polymerase- 1 (PARP-1). Vitamin D has also been implicated in asthma through its effects on the obesity, bacillus Calmettee Guérin (BCG) vaccination and high vitamin D level, vitamin D supplement, checkpoint protein kinase 1 (Chk1), plasminogen activator inhibitor-1 (PAI-1) and gamma delta T cells (gdT). Vitamin D plays a role in asthma and exerts its action through either genomic and/or non-genomic ways.

Extracellular matrix protein tenascin-C is required in the bone marrow microenvironment primed for hematopoietic regeneration

The BM microenvironment is required for the maintenance, proliferation, and mobilization of hematopoietic stem and progenitor cells (HSPCs), both during steady-state conditions and hematopoietic recovery after myeloablation. The ECM meshwork has long been recognized as a major anatomical component of the BM microenvironment; however, the molecular signatures and functions of the ECM to support HSPCs are poorly understood. Of the many ECM proteins, the expression of tenascin-C (TN-C) was found to be dramatically up-regulated during hematopoietic recovery after myeloablation. The TN-C gene was predominantly expressed in stromal cells and endothelial cells, known as BM niche cells, supporting the function of HSPCs. Mice lacking TN-C (TN-C(-/-)) mice showed normal steady-state hematopoiesis; however, they failed to reconstitute hematopoiesis after BM ablation and showed high lethality. The capacity to support transplanted wild-type hematopoietic cells to regenerate hematopoiesis was reduced in TN-C(-/-) recipient mice. In vitro culture on a TN-C substratum promoted the proliferation of HSPCs in an integrin α9-dependent manner and up-regulated the expression of the cyclins (cyclinD1 and cyclinE1) and down-regulated the expression of the cyclin-dependent kinase inhibitors (p57(Kip2), p21(Cip1), p16(Ink4a)). These results identify TN-C as a critical component of the BM microenvironment that is required for hematopoietic regeneration.

Does airway smooth muscle express an inflammatory phenotype in asthma?

In addition to hyperresponsiveness in asthma, airway smooth muscle (ASM) also manifests an inflammatory phenotype characterized by augmented expression of mediators that enhance inflammation, contribute to tissue remodelling and augment leucocyte trafficking and activity. Our present review summarizes contemporary understanding of ASM-derived mediators and their paracrine and autocrine actions in airway diseases.

Tenascins and the importance of adhesion modulation

Tenascins are a family of extracellular matrix proteins that evolved in early chordates. There are four family members: tenascin-X, tenascin-R, tenascin-W, and tenascin-C. Tenascin-X associates with type I collagen, and its absence can cause Ehlers-Danlos Syndrome. In contrast, tenascin-R is concentrated in perineuronal nets. The expression of tenascin-C and tenascin-W is developmentally regulated, and both are expressed during disease (e.g., both are associated with cancer stroma and tumor blood vessels). In addition, tenascin-C is highly induced by infections and inflammation. Accordingly, the tenascin-C knockout mouse has a reduced inflammatory response. All tenascins have the potential to modify cell adhesion either directly or through interaction with fibronectin, and cell-tenascin interactions typically lead to increased cell motility. In the case of tenascin-C, there is a correlation between elevated expression and increased metastasis in several types of tumors.

The actin associated protein palladin in smooth muscle and in the development of diseases of the cardiovasculature and in cancer

Palladin is an actin associated protein serving as a cytoskeleton scaffold, and actin cross linker, localizing at stress fibers, focal adhesions, and other actin based structures. Recent studies showed that palladin plays a critical role in smooth muscle differentiation, migration, contraction, and more importantly contributes to embryonic development. This review will focus on the functions and possible mechanisms of palladin in smooth muscle and in pathological conditions such as cardiovascular diseases and cancers.