Characterization of the activation of latent TGF-beta by co-cultures of endothelial cells and pericytes or smooth muscle cells: a self-regulating system

Advanced biosensors for nanomaterial-based detection of transforming growth factor alpha and beta, a class of major polypeptide regulators

Transforming growth factors (TGFs) regulate several cellular processes including, differentiation, growth, migration, extracellular matrix production, and apoptosis. TGF alpha (TGF-α) is a heterogeneous molecule containing 160 amino acid residues. It is a potent angiogenesis promoter that is activated by JAK-STAT signaling. Whereas TGF beta (TGF-β) consists of 390-412 amino acids. Smad and non-Smad signaling both occur in TGF beta. It is linked to immune cell activation, differentiation, and proliferation. It also triggers pre-apoptotic responses and inhibits cell proliferation. Both growth factors have a promising role in the development and homeostasis of tissues. Defects such as autoimmune diseases and cancer develop mechanisms to modulate checkpoints of the immune system resulting in altered growth factors profile. An accurate amount of these growth factors is essential for normal functioning, but an exceed or fall behind the normal level is alarming as it is linked to several disorders. This demands techniques for TGF-α and TGF-β profiling to effectively diagnose diseases, monitor their progression, and assess the efficacy of immunotherapeutic drugs. Quantitative detection techniques including the emergence of biosensing technology seem to accomplish the purpose. Until the present time, few biosensors have been designed in the context of TGF-α and TGF-β for disease detection, analyzing receptor binding, and interaction with carriers. In this paper, we have reviewed the physiology of transforming growth factor alpha and beta, including the types, structure, function, latent/active forms, signaling, and defects caused. It involves the description of biosensors on TGF-α and TGF-β, advances in technology, and future perspectives.

Enhancing differentiation of menstrual blood-derived stem cells into female germ cells using a bilayer amniotic membrane and nano-fibrous fibroin scaffold

Three-dimensional nanofiber scaffolds offer a promising method for simulating in vivo conditions within the laboratory. This study aims to investigate the influence of a bilayer amniochorionic membrane/nanofibrous fibroin scaffold on the differentiation of human menstrual blood mesenchymal stromal/stem cells (MenSCs) into female germ cells. MenSCs were isolated and assigned to four culture groups: (i) MenSCs co-cultured with granulosa cells (GCs) using the scaffold (3D-T group), (ii) MenSCs using the scaffold alone (3D-C group), (iii) MenSCs co-cultured only with GCs (2D-T group), and (iv) MenSCs without co-culture or scaffold (2D-C group). Both MenSCs and GCs were independently cultured for two weeks before co-culturing was initiated. Flow cytometry was employed to characterize MenSCs based on positive markers (CD73, CD90, and CD105) and negative markers (CD45 and CD133). Additionally, flow cytometry and immunocytochemistry were used to characterize the GCs. Differentiated MenSCs were analyzed using real-time PCR and immunostaining. The real-time PCR results demonstrated significantly higher levels of VASA expression in the 3D-T group compared to the 3D-C, 2D-T, and 2D-C groups. Similarly, the SCP3 mRNA level in the 3D-T group was notably elevated compared to the 3D-C, 2D-T, and 2D-C groups. Moreover, the expression of GDF9 was significantly higher in the 3D-T group when compared to the 3D-C, 2D-T, and 2D-C groups. Immunostaining results revealed a lack of signal for VASA, SCP3, or GDF9 markers in the 2D-T group, while some cells in the 3D-T group exhibited positive staining for all these proteins. These findings suggest that the combination of a bilayer amniochorionic membrane/nanofibrous fibroin scaffold with co-culturing GCs facilitates the differentiation of MenSCs into female germ cells.

Tale of two systems: the intertwining duality of fibrinolysis and lipoprotein metabolism

Fibrinolysis is an enzymatic process that breaks down fibrin clots, while dyslipidemia refers to abnormal levels of lipids and lipoproteins in the blood. Both fibrinolysis and lipoprotein metabolism are critical mechanisms that regulate a myriad of functions in the body, and the imbalance of these mechanisms is linked to the development of pathologic conditions, such as thrombotic complications in atherosclerotic cardiovascular diseases. Accumulated evidence indicates the close relationship between the 2 seemingly distinct and complicated systems-fibrinolysis and lipoprotein metabolism. Observational studies in humans found that dyslipidemia, characterized by increased blood apoB-lipoprotein and decreased high-density lipoprotein, is associated with lower fibrinolytic potential. Genetic variants of some fibrinolytic regulators are associated with blood lipid levels, supporting a causal relationship between these regulators and lipoprotein metabolism. Mechanistic studies have elucidated many pathways that link the fibrinolytic system and lipoprotein metabolism. Moreover, profibrinolytic therapies improve lipid panels toward an overall cardiometabolic healthier phenotype, while some lipid-lowering treatments increase fibrinolytic potential. The complex relationship between lipoprotein and fibrinolysis warrants further research to improve our understanding of the bidirectional regulation between the mediators of fibrinolysis and lipoprotein metabolism.

Highlighting In Vitro the Role of Brain-like Endothelial Cells on the Maturation and Metabolism of Brain Pericytes by SWATH Proteomics

Within the neurovascular unit, brain pericytes (BPs) are of major importance for the induction and maintenance of the properties of the blood-brain barrier (BBB) carried by the brain microvessel endothelial cells (ECs). Throughout barriergenesis, ECs take advantage of soluble elements or contact with BPs to maintain BBB integrity and the regulation of their cellular homeostasis. However, very few studies have focused on the role of ECs in the maturation of BPs. The aim of this study is to shed light on the proteome of BPs solocultured (hBP-solo) or cocultured with ECs (hBP-coc) to model the human BBB in a non-contact manner. We first generated protein libraries for each condition and identified 2233 proteins in hBP-solo versus 2492 in hBP-coc and 2035 common proteins. We performed a quantification of the enriched proteins in each condition by sequential window acquisition of all theoretical mass spectra (SWATH) analysis. We found 51 proteins enriched in hBP-solo related to cell proliferation, contractility, adhesion and extracellular matrix element production, a protein pattern related to an immature cell. In contrast, 90 proteins are enriched in hBP-coc associated with a reduction in contractile activities as observed in vivo in ‘mature’ BPs, and a significant gain in different metabolic functions, particularly related to mitochondrial activities and sterol metabolism. This study highlights that BPs take advantage of ECs during barriergenesis to make a metabolic switch in favor of BBB homeostasis in vitro.

Dual SMAD inhibition enhances the longevity of human epididymis epithelial cells

Primary human epididymis epithelial (HEE) cells are valuable reagents for functional studies on the human epididymis. We used them previously to determine the transcriptional networks that establish cell identity along the length of the epididymis from caput, corpus, and cauda. These studies on HEE cells and organoids derived from them revealed important cellular properties. However, similar to other primary cells, HEE cells undergo replicative senescence and de-differentiation in culture. A cocktail of small molecules was shown elsewhere to extend longevity of epithelial basal cells. The components included transforming growth factor β (TGF-β)/bone morphogenetic protein (BMP) antagonists, WNT agonist, and Rho-associated and coiled-coil containing protein kinase (ROCK) inhibitor (ROCKi), which together prevented the senescence-related upregulation of TGF-β signaling pathway members. Here, we treat HEE cells with the same cocktail and observed enhanced replicative potential and prolonged expression of markers of HEE differentiation. This treatment expands the differentiated HEE cell population available from individual epididymis tissue samples that can be used for molecular, cellular, and functional studies.

TGFβ: Signaling Blockade for Cancer Immunotherapy

Discovered over four decades ago, transforming growth factor β (TGFβ) is a potent pleiotropic cytokine that has context-dependent effects on most cell types. It acts as a tumor suppressor in some cancers and/or supports tumor progression and metastasis through its effects on the tumor stroma and immune microenvironment. In TGFβ-responsive tumors it can promote invasion and metastasis through epithelial-mesenchymal transformation, the appearance of cancer stem cell features, and resistance to many drug classes, including checkpoint blockade immunotherapies. Here we consider the biological activities of TGFβ action on different cells of relevance toward improving immunotherapy outcomes for patients, with a focus on the adaptive immune system. We discuss recent advances in the development of drugs that target the TGFβ signaling pathway in a tumor-specific or cell type–specific manner to improve the therapeutic window between response rates and adverse effects.

p62-Nrf2 Regulatory Loop Mediates the Anti-Pulmonary Fibrosis Effect of Bergenin

Idiopathic pulmonary fibrosis (IPF) can severely disrupt lung function, leading to fatal consequences, and there is currently a lack of specific therapeutic drugs. Bergenin is an isocoumarin compound with lots of biological functions including antioxidant activity. This study evaluated the potential beneficial effects of bergenin on pulmonary fibrosis and investigated the possible mechanisms. We found that bergenin alleviated bleomycin-induced pulmonary fibrosis by relieving oxidative stress, reducing the deposition of the extracellular matrix (ECM) and inhibiting the formation of myofibroblasts. Furthermore, we showed that bergenin could induce phosphorylation and expression of p62 and activation of Nrf2, Nrf2 was required for bergenin-induced p62 upregulation, and p62 knockdown reduced bergenin-induced Nrf2 activity. More importantly, knockdown of Nrf2 or p62 could abrogate the antioxidant activity of bergenin and the inhibition effect of bergenin on TGF-β-induced ECM deposition and myofibroblast differentiation. Thereby, a regulatory loop is formed between p62 and Nrf2, which is an important target for bergenin aimed at treating pulmonary fibrosis.

Transcryptomic Analysis of Human Brain -Microvascular Endothelial Cell Driven Changes in -Vascular Pericytes

Many pathological conditions of the brain are associated with structural abnormalities within the neurovascular system and linked to pericyte (PC) loss and/or dysfunction. Since crosstalk between endothelial cells (ECs) and PCs greatly impacts the function of the blood–brain barrier (BBB), effects of PCs on endothelial integrity and function have been investigated extensively. However, the impact of ECs on the function and activity of PCs remains largely unknown. Hence, using co-cultures of human brain vascular PCs with human cerebral microvascular ECs on opposite sides of porous Transwell inserts which facilitates direct EC–PC contact and improves EC barrier function, we analyzed EC-driven transcriptomic changes in PCs using microarrays and changes in cytokines/chemokines using proteome arrays. Gene expression analysis (GEA) in PCs co-cultured with ECs versus PCs cultured alone showed significant upregulation of 1′334 genes and downregulation of 964 genes. GEA in co-cultured PCs revealed increased expression of five prominent PC markers as well as soluble factors, such as transforming growth factor beta, fibroblast growth factor, angiopoietin 1, brain-derived neurotrophic factor, all of which are involved in EC–PC crosstalk and BBB induction. Pathway enrichment analysis of modulated genes showed a strong impact on many inflammatory and extracellular matrix (ECM) pathways including interferon and interleukin signaling, TGF-β and interleukin-1 regulation of ECM, as well as on the mRNA processing pathway. Interestingly, while co-culture induced the mRNA expression of many chemokines and cytokines, including several CCL- and CXC-motif ligands and interleukins, we observed a decreased expression of the same inflammatory mediators on the protein level. Importantly, in PCs, ECs significantly induced interferon associated proteins (IFIT1, IFI44L, IF127, IFIT3, IFI6, IFI44) with anti-viral actions; downregulated prostaglandin E receptor 2 (prevent COX-2 mediated BBB damage); upregulated fibulin-3 and connective tissue growth factor essential for BBB integrity; and multiple ECMs (collagens and integrins) that inhibit cell migration. Our findings suggest that via direct contact, ECs prime PCs to induce molecules to promote BBB integrity and cell survival during infection and inflammatory insult. Taken together, we provide first evidence that interaction with ECs though porous membranes induces major changes in the transcriptomic and proteomic profile of PCs. ECs influence genes involved in diverse aspects of PC function including PC maturation, cell survival, anti-viral defense, blood flow regulation, immuno-modulation and ECM deposition.

PPARγ mediates the anti-pulmonary fibrosis effect of icaritin

BACKGROUND

Pulmonary fibrosis is a fatal lung disease with limited treatment options. Icaritin is the active ingredient derived from the traditional Chinese medical plant Epimedium and possesses many biomedical activities. This study aimed to investigate the effects and molecular mechanisms of icaritin on bleomycin-induced pulmonary fibrosis in mice.

METHODS

To assess its preventative effects, bleomycin treated mice received 0, 0.04, 0.2, and 1 mg/kg of icaritin from day 1 onwards. To assess its therapeutic effects, bleomycin treated mice received 0 and 1 mg/kg of icaritin from day 15 onwards. Mice were sacrificed on day 21 and lung tissues were collected, stained with HE, Masson and immunohistochemistry. Q-PCR was used to measure Collagen I and Collagen III expression, western blotting was used to quantify α-SMA, Collagen I expression. Hydroxyproline content was measured using a biochemical method. NIH3T3 and HLF-1 cells were treated with TGF-β1with or without icaritin, and α-SMA, Collagen I were tested. PPARγ antagonist GW9662 and PPARγ-targeted siRNA were used to investigate the mechanism of icaritin in inhibiting myofibroblast differentiation.

RESULTS

Both preventative and therapeutic administration of icaritin improved the histopathological changes, decreased Collagen and α-SMA, lowered hydroxyproline content in bleomycin-treated lung tissues. Icaritin decreased α-SMA and Collagen I expression in TGF-β1-stimulated NIH3T3 and HLF-1 cells. However, its effect in reducing α-SMA and Collagen I expression was suppressed when expression or activity of PPARγ was inhibited.

CONCLUSIONS

Icaritin has therapeutic potential against pulmonary fibrosis via the inhibition of myofibroblast differentiation, which may be mediated by PPARγ.

A Serpin With a Finger in Many PAIs: PAI-1's Central Function in Thromboinflammation and Cardiovascular Disease

Plasminogen activator inhibitor 1 (PAI-1) is a member of the serine protease inhibitor (serpin) superfamily. PAI-1 is the principal inhibitor of the plasminogen activators, tissue plasminogen activator (tPA), and urokinase-type plasminogen activator (uPA). Turbulence in the levels of PAI-1 tilts the balance of the hemostatic system resulting in bleeding or thrombotic complications. Not surprisingly, there is strong evidence that documents the role of PAI-1 in cardiovascular disease. The more recent uncovering of the coalition between the hemostatic and inflammatory pathways has exposed a distinct role for PAI-1. The storm of proinflammatory cytokines liberated during inflammation, including IL-6 and TNF-α, directly influence PAI-1 synthesis and increase circulating levels of this serpin. Consequently, elevated levels of PAI-1 are commonplace during infection and are frequently associated with a hypofibrinolytic state and thrombotic complications. Elevated PAI-1 levels are also a feature of metabolic syndrome, which is defined by a cluster of abnormalities including obesity, type 2 diabetes, hypertension, and elevated triglyceride. Metabolic syndrome is in itself defined as a proinflammatory state associated with elevated levels of cytokines. In addition, insulin has a direct impact on PAI-1 synthesis bridging these pathways. This review describes the key physiological functions of PAI-1 and how these become perturbed during disease processes. We focus on the direct relationship between PAI-1 and inflammation and the repercussion in terms of an ensuing hypofibrinolytic state and thromboembolic complications. Collectively, these observations strengthen the utility of PAI-1 as a viable drug target for the treatment of various diseases.

Vascular endothelial cell specification in health and disease

There are two vascular networks in mammals that coordinately function as the main supply and drainage systems of the body. The blood vasculature carries oxygen, nutrients, circulating cells, and soluble factors to and from every tissue. The lymphatic vasculature maintains interstitial fluid homeostasis, transports hematopoietic cells for immune surveillance, and absorbs fat from the gastrointestinal tract. These vascular systems consist of highly organized networks of specialized vessels including arteries, veins, capillaries, and lymphatic vessels that exhibit different structures and cellular composition enabling distinct functions. All vessels are composed of an inner layer of endothelial cells that are in direct contact with the circulating fluid; therefore, they are the first responders to circulating factors. However, endothelial cells are not homogenous; rather, they are a heterogenous population of specialized cells perfectly designed for the physiological demands of the vessel they constitute. This review provides an overview of the current knowledge of the specification of arterial, venous, capillary, and lymphatic endothelial cell identities during vascular development. We also discuss how the dysregulation of these processes can lead to vascular malformations, and therapeutic approaches that have been developed for their treatment.

TNF-α enhances TGF-β-induced endothelial-to-mesenchymal transition via TGF-β signal augmentation

The tumor microenvironment (TME) consists of various components including cancer cells, tumor vessels, cancer-associated fibroblasts (CAFs), and inflammatory cells. These components interact with each other via various cytokines, which often induce tumor progression. Thus, a greater understanding of TME networks is crucial for the development of novel cancer therapies. Many cancer types express high levels of TGF-β, which induces endothelial-to-mesenchymal transition (EndMT), leading to formation of CAFs. Although we previously reported that CAFs derived from EndMT promoted tumor formation, the molecular mechanisms underlying these interactions remain to be elucidated. Furthermore, tumor-infiltrating inflammatory cells secrete various cytokines, including TNF-α. However, the role of TNF-α in TGF-β-induced EndMT has not been fully elucidated. Therefore, this study examined the effect of TNF-α on TGF-β-induced EndMT in human endothelial cells (ECs). Various types of human ECs underwent EndMT in response to TGF-β and TNF-α, which was accompanied by increased and decreased expression of mesenchymal cell and EC markers, respectively. In addition, treatment of ECs with TGF-β and TNF-α exhibited sustained activation of Smad2/3 signals, which was presumably induced by elevated expression of TGF-β type I receptor, TGF-β2, activin A, and integrin αv, suggesting that TNF-α enhanced TGF-β-induced EndMT by augmenting TGF-β family signals. Furthermore, oral squamous cell carcinoma-derived cells underwent epithelial-to-mesenchymal transition (EMT) in response to humoral factors produced by TGF-β and TNF-α-cultured ECs. This EndMT-driven EMT was blocked by inhibiting the action of TGF-βs. Collectively, our findings suggest that TNF-α enhances TGF-β-dependent EndMT, which contributes to tumor progression.

Transcriptome analysis reveals microvascular endothelial cell-dependent pericyte differentiation

Microvascular homeostasis is strictly regulated, requiring close interaction between endothelial cells and pericytes. Here, we aimed to improve our understanding of how microvascular crosstalk affects pericytes. Human-derived pericytes, cultured in absence, or presence of human endothelial cells, were studied by RNA sequencing. Compared with mono-cultured pericytes, a total of 6704 genes were differentially expressed in co-cultured pericytes. Direct endothelial contact induced transcriptome profiles associated with pericyte maturation, suppression of extracellular matrix production, proliferation, and morphological adaptation. In vitro studies confirmed enhanced pericyte proliferation mediated by endothelial-derived PDGFB and pericyte-derived HB-EGF and FGF2. Endothelial-induced PLXNA2 and ACTR3 upregulation also triggered pericyte morphological adaptation. Pathway analysis predicted a key role for TGFβ signaling in endothelial-induced pericyte differentiation, whereas the effect of signaling via gap- and adherens junctions was limited. We demonstrate that endothelial cells have a major impact on the transcriptional profile of pericytes, regulating endothelial-induced maturation, proliferation, and suppression of ECM production.

Reactive oxygen species as signaling molecules in the development of lung fibrosis

Pulmonary fibrosis is a relatively rare but devastating disease characterized by the excessive deposition of extracellular matrix. The increased matrix results in reduced lung compliance and increased work of breathing, while the obliteration of alveolar-capillary structures can result in hypoxemia and pulmonary hypertension, which manifests clinically as worsening shortness of breath, respiratory failure, and death. Unbiased genome-wide association studies combined with animal models suggest that damage to the alveolar epithelium is the initiating factor in pulmonary fibrosis. This epithelial injury leads to the activation and proliferation of myofibroblasts that secrete extracellular matrix proteins characteristic of fibrosis. The best described molecular link between alveolar epithelial dysfunction and myofibroblast activation and proliferation is the profibrotic cytokine transforming growth factor-β (TGF-β). We and others have found that mitochondrial and NAD(P)H oxidase-generated reactive oxygen species (ROS) play a signaling role to enhance TGF-β signaling and promote fibrosis. The purpose of this article is to review how ROS signaling leads to the activation of TGF-β. We suggest that an improved understanding of these pathways might explain the failure of nonselective antioxidants to improve outcomes in patients with pulmonary fibrosis and might identify novel targets for therapy.

Transforming Growth Factor β1 Function in Airway Remodeling and Hyperresponsiveness. The Missing Link?

The pathogenesis of asthma includes a complex interplay among airway inflammation, hyperresponsiveness, and remodeling. Current evidence suggests that airway structural cells, including bronchial smooth muscle cells, myofibroblasts, fibroblasts, and epithelial cells, mediate all three aspects of asthma pathogenesis. Although studies show a connection between airway remodeling and changes in bronchomotor tone, the relationship between the two remains unclear. Transforming growth factor β1 (TGF-β1), a growth factor elevated in the airway of patients with asthma, plays a role in airway remodeling and in the shortening of various airway structural cells. However, the role of TGF-β1 in mediating airway hyperresponsiveness remains unclear. In this review, we summarize the literature addressing the role of TGF-β1 in airway remodeling and shortening. Through our review, we aim to further elucidate the role of TGF-β1 in asthma pathogenesis and the link between airway remodeling and airway hyperresponsiveness in asthma and to define TGF-β1 as a potential therapeutic target for reducing asthma morbidity and mortality.

Cleavage of the urokinase receptor (uPAR) on oral cancer cells: regulation by transforming growth factor - β1 (TGF-β1) and potential effects on migration and invasion

BACKGROUND

Urokinase plasminogen activator (uPA) receptor (uPAR) is up-regulated at the invasive tumour front of human oral squamous cell carcinoma (OSCC), indicating a role for uPAR in tumour progression. We previously observed elevated expression of uPAR at the tumour-stroma interface in a mouse model for OSCC, which was associated with increased proteolytic activity. The tumour microenvironment regulated uPAR expression, as well as its glycosylation and cleavage. Both full-length- and cleaved uPAR (uPAR (II-III)) are involved in highly regulated processes such as cell signalling, proliferation, migration, stem cell mobilization and invasion. The aim of the current study was to analyse tumour associated factors and their effect on uPAR cleavage, and the potential implications for cell proliferation, migration and invasion.

METHODS

Mouse uPAR was stably overexpressed in the mouse OSCC cell line AT84. The ratio of full-length versus cleaved uPAR as analysed by Western blotting and its regulation was assessed by addition of different protease inhibitors and transforming growth factor - β1 (TGF-β1). The role of uPAR cleavage in cell proliferation and migration was analysed using real-time cell analysis and invasion was assessed using the myoma invasion model.

RESULTS

We found that when uPAR was overexpressed a proportion of the receptor was cleaved, thus the cells presented both full-length uPAR and uPAR (II-III). Cleavage was mainly performed by serine proteases and urokinase plasminogen activator (uPA) in particular. When the OSCC cells were stimulated with TGF-β1, the production of the uPA inhibitor PAI-1 was increased, resulting in a reduction of uPAR cleavage. By inhibiting cleavage of uPAR, cell migration was reduced, and by inhibiting uPA activity, invasion was reduced. We could also show that medium containing soluble uPAR (suPAR), and cleaved soluble uPAR (suPAR (II-III)), induced migration in OSCC cells with low endogenous levels of uPAR.

CONCLUSIONS

These results show that soluble factors in the tumour microenvironment, such as TGF-β1, PAI-1 and uPA, can influence the ratio of full length and uPAR (II-III) and thereby potentially effect cell migration and invasion. Resolving how uPAR cleavage is controlled is therefore vital for understanding how OSCC progresses and potentially provides new targets for therapy.

The Discovery and Early Days of TGF-β: A Historical Perspective

Transforming growth factors (TGFs) were discovered as activities that were secreted by cancer cells, and later by normal cells, and had the ability to phenotypically and reversibly transform immortalized fibroblasts. TGF-β distinguished itself from TGF-α because it did not bind to the same epidermal growth factor (EGF) receptor as TGF-α and, therefore, acted through different cell-surface receptors and signaling mediators. This review summarizes the discovery of TGF-β, the early developments in its molecular and biological characterization with its many biological activities in different cell and tissue contexts and its roles in disease, the realization that there is a family of secreted TGF-β-related proteins with many differentiation functions in development and activities in normal cell and tissue physiology, and the subsequent identification and characterization of the receptors and effectors that mediate TGF-β family signaling responses.

TGF-β Small Molecule Inhibitor SB431542 Reduces Rotator Cuff Muscle Fibrosis and Fatty Infiltration By Promoting Fibro/Adipogenic Progenitor Apoptosis

Rotator cuff tears represent a large burden of muscle-tendon injuries in our aging population. While small tears can be repaired surgically with good outcomes, critical size tears are marked by muscle atrophy, fibrosis, and fatty infiltration, which can lead to failed repair, frequent re-injury, and chronic disability. Previous animal studies have indicated that Transforming Growth Factor-β (TGF-β) signaling may play an important role in the development of these muscle pathologies after injury. Here, we demonstrated that inhibition of TGF-β1 signaling with the small molecule inhibitor SB431542 in a mouse model of massive rotator cuff tear results in decreased fibrosis, fatty infiltration, and muscle weight loss. These observed phenotypic changes were accompanied by decreased fibrotic, adipogenic, and atrophy-related gene expression in the injured muscle of mice treated with SB431542. We further demonstrated that treatment with SB431542 reduces the number of fibro/adipogenic progenitor (FAP) cells-an important cellular origin of rotator cuff muscle fibrosis and fatty infiltration, in injured muscle by promoting apoptosis of FAPs. Together, these data indicate that the TGF-β pathway is a critical regulator of the degenerative muscle changes seen after massive rotator cuff tears. TGF-β promotes rotator cuff muscle fibrosis and fatty infiltration by preventing FAP apoptosis. TGF-β regulated FAP apoptosis may serve as an important target pathway in the future development of novel therapeutics to improve muscle outcomes following rotator cuff tear.

DMSO Enhances TGF-β Activity by Recruiting the Type II TGF-β Receptor From Intracellular Vesicles to the Plasma Membrane

Dimethyl sulfoxide (DMSO) is used to treat many diseases/symptoms. The molecular basis of the pharmacological actions of DMSO has been unclear. We hypothesized that DMSO exerts some of these actions by enhancing TGF-β activity. Here we show that DMSO enhances TGF-β activity by ∼3-4-fold in Mv1Lu and NMuMG cells expressing Smad-dependent luciferase reporters. In Mv1Lu cells, DMSO enhances TGF-β-stimulated expression of P-Smad2 and PAI-1. It increases cell-surface expression of TGF-β receptors (TβR-I and/or TβR-II) by ∼3-4-fold without altering their cellular levels as determined by (125) I-labeled TGF-β-cross-linking/Western blot analysis, suggesting the presence of large intracellular pools in these cells. Sucrose density gradient ultracentrifugation/Western blot analysis reveals that DMSO induces recruitment of TβR-II (but not TβR-I) from its intracellular pool to plasma-membrane microdomains. It induces more recruitment of TβR-II to non-lipid raft microdomains than to lipid rafts/caveolae. Mv1Lu cells transiently transfected with TβR-II-HA plasmid were treated with DMSO and analyzed by indirect immunofluoresence staining using anti-HA antibody. In these cells, TβR-II-HA is present as a vesicle-like network in the cytoplasm as well as in the plasma membrane. DMSO causes depletion of TβR-II-HA-containing vesicles from the cytoplasm and co-localization of TβR-II-HA and cveolin-1 at the plasma membrane. These results suggest that DMSO, a fusogenic substance, enhances TGF-β activity presumably by inducing fusion of cytoplasmic vesicles (containing TβR-II) and the plasma membrane, resulting in increased localization of TβR-II to non-lipid raft microdomains where canonical signaling occurs. Fusogenic activity of DMSO may play a pivotal role in its pharmacological actions involving membrane proteins with large cytoplasmic pools. J. Cell. Biochem. 117: 1568-1579, 2016. © 2015 Wiley Periodicals, Inc.

TGF-beta1 regulates human brain pericyte inflammatory processes involved in neurovasculature function

Background

Transforming growth factor beta 1 (TGFβ₁) is strongly induced following brain injury and polarises microglia to an anti-inflammatory phenotype. Augmentation of TGFβ₁ responses may therefore be beneficial in preventing inflammation in neurological disorders including stroke and neurodegenerative diseases. However, several other cell types display immunogenic potential and identifying the effect of TGFβ₁ on these cells is required to more fully understand its effects on brain inflammation. Pericytes are multifunctional cells which ensheath the brain vasculature and have garnered recent attention with respect to their immunomodulatory potential. Here, we sought to investigate the inflammatory phenotype adopted by TGFβ₁-stimulated human brain pericytes.

Methods

Microarray analysis was performed to examine transcriptome-wide changes in TGFβ₁-stimulated pericytes, and results were validated by qRT-PCR and cytometric bead arrays. Flow cytometry, immunocytochemistry and LDH/Alamar Blue® viability assays were utilised to examine phagocytic capacity of human brain pericytes, transcription factor modulation and pericyte health.

Results

TGFβ₁ treatment of primary human brain pericytes induced the expression of several inflammatory-related genes (NOX4, COX2, IL6 and MMP2) and attenuated others (IL8, CX3CL1, MCP1 and VCAM1). A synergistic induction of IL-6 was seen with IL-1β/TGFβ₁ treatment whilst TGFβ₁ attenuated the IL-1β-induced expression of CX3CL1, MCP-1 and sVCAM-1. TGFβ₁ was found to signal through SMAD2/3 transcription factors but did not modify nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) translocation. Furthermore, TGFβ₁ attenuated the phagocytic ability of pericytes, possibly through downregulation of the scavenger receptors CD36, CD47 and CD68. Whilst TGFβ did decrease pericyte number, this was due to a reduction in proliferation, not apoptotic death or compromised cell viability.

Conclusions

TGFβ₁ attenuated pericyte expression of key chemokines and adhesion molecules involved in CNS leukocyte trafficking and the modulation of microglial function, as well as reduced the phagocytic ability of pericytes. However, TGFβ₁ also enhanced the expression of classical pro-inflammatory cytokines and enzymes which can disrupt BBB functioning, suggesting that pericytes adopt a phenotype which is neither solely pro- nor anti-inflammatory. Whilst the effects of pericyte modulation by TGFβ₁ in vivo are difficult to infer, the reduction in pericyte proliferation together with the elevated IL-6, MMP-2 and NOX4 and reduced phagocytosis suggests a detrimental action of TGFβ₁ on neurovasculature.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0503-0) contains supplementary material, which is available to authorized users.

Matters of context guide future research in TGFβ superfamily signaling

The highly conserved wiring of the SMAD-dependent transforming growth factor β (TGFβ) superfamily signaling pathway has been mapped over the last 20 years after molecular discovery of its component parts. Numerous alternative TGFβ-activated signaling pathways that elicit SMAD-independent biological responses also exist. However, the molecular mechanisms responsible for the renowned context dependency of TGFβ signaling output remains an active and often confounding area of research, providing a prototype relevant to regulation of other signaling pathways. Highlighting discoveries presented at the 9th FASEB meeting, The TGFβ Superfamily: Signaling in Development and Disease (July 12-17th 2015 in Snowmass, Colorado), this Review outlines research into the rich contextual nature of TGFβ signaling output and offers clues for therapeutic advances.

Deletion of ocular transforming growth factor β signaling mimics essential characteristics of diabetic retinopathy

Diabetic retinopathy, a major cause of blindness, is characterized by a distinct phenotype. The molecular causes of the phenotype are not sufficiently clear. Here, we report that deletion of transforming growth factor β signaling in the retinal microenvironment of newborn mice induces changes that largely mimic the phenotype of nonproliferative and proliferative diabetic retinopathy in humans. Lack of transforming growth factor β signaling leads to the formation of abundant microaneurysms, leaky capillaries, and retinal hemorrhages. Retinal capillaries are not covered by differentiated pericytes, but by a coat of vascular smooth muscle-like cells and a thickened basal lamina. Reactive microglia is found in close association with retinal capillaries. In older animals, loss of endothelial cells and the formation of ghost vessels are observed, findings that correlate with the induction of angiogenic molecules and the accumulation of retinal hypoxia-inducible factor 1α, indicating hypoxia. Consequently, retinal and vitreal neovascularization occurs, a scenario that leads to retinal detachment, vitreal hemorrhages, neuronal apoptosis, and impairment of sensory function. We conclude that transforming growth factor β signaling is required for the differentiation of retinal pericytes during vascular development of the retina. Lack of differentiated pericytes initiates a scenario of structural and functional changes in the retina that mimics those of diabetic retinopathy strongly indicating a common mechanism.

The role of TGFβ1 and LRG1 in cardiac remodelling and heart failure

Heart failure is a life-threatening condition that carries a considerable emotional and socio-economic burden. As a result of the global increase in the ageing population, sedentary life-style, increased prevalence of risk factors, and improved survival from cardiovascular events, the incidence of heart failure will continue to rise. Despite the advances in current cardiovascular therapies, many patients are not suitable for or may not benefit from conventional treatments. Thus, more effective therapies are required. Transforming growth factor (TGF) β family of cytokines is involved in heart development and dys-regulated TGFβ signalling is commonly associated with fibrosis, aberrant angiogenesis and accelerated progression into heart failure. Therefore, a potential therapeutic pathway is to modulate TGFβ signalling; however, broad blockage of TGFβ signalling may cause unwanted side effects due to its pivotal role in tissue homeostasis. We found that leucine-rich α-2 glycoprotein 1 (LRG1) promotes blood vessel formation via regulating the context-dependent endothelial TGFβ signalling. This review will focus on the interaction between LRG1 and TGFβ signalling, their involvement in the pathogenesis of heart failure, and the potential for LRG1 to function as a novel therapeutic target.

Design of growth factor sequestering biomaterials

Growth factors (GFs) are major regulatory proteins that can govern cell fate, migration, and organization. Numerous aspects of the cell milieu can modulate cell responses to GFs, and GF regulation is often achieved by the native extracellular matrix (ECM). For example, the ECM can sequester GFs and thereby control GF bioavailability. In addition, GFs can exert distinct effects depending on whether they are sequestered in solution, at two-dimensional interfaces, or within three-dimensional matrices. Understanding how the context of GF sequestering impacts cell function in the native ECM can instruct the design of soluble or insoluble GF sequestering moieties, which can then be used in a variety of bioengineering applications. This Feature Article provides an overview of the natural mechanisms of GF sequestering in the cell milieu, and reviews the recent bioengineering approaches that have sequestered GFs to modulate cell function. Results to date demonstrate that the cell response to GF sequestering depends on the affinity of the sequestering interaction, the spatial proximity of sequestering in relation to cells, the source of the GF (supplemented or endogenous), and the phase of the sequestering moiety (soluble or insoluble). We highlight the importance of context for the future design of biomaterials that can leverage endogenous molecules in the cell milieu and mitigate the need for supplemented factors.

Pericytes in kidney fibrosis

PURPOSE OF REVIEW

Pericytes and perivascular fibroblasts have emerged as poorly appreciated yet extensive populations of mesenchymal cells in the kidney that play important roles in homeostasis and responses to injury. This review will update readers on the evolving understanding of the biology of these cells.

RECENT FINDINGS

Fate mapping has identified pericytes and perivascular fibroblasts as the major source of pathological fibrillar matrix-forming cells in interstitial kidney disease. In other organs similar cells have been described and independent fate mapping indicates that pericytes or perivascular cells are myofibroblast progenitors in multiple organs. Over the last year, new insights into the function of pericytes in kidney homeostasis has been uncovered and new molecular pathways that regulate detachment and their transdifferentiation into pathological myofibroblasts, including Wingless/Int, ephrin, transforming growth factor β, platelet derived growth factor, and Hedgehog signaling pathways, have been reported. In addition provocative studies indicate that microRNAs, which regulate posttranscriptional gene expression, may also play important roles in their transdifferentiation.

SUMMARY

Pericytes and perivascular fibroblasts are the major source of pathological collagen fiber-forming cells in interstitial kidney diseases. New avenues of research into their activation and differentiation has identified new drug candidates for the treatment of interstitial kidney disease.

The brain tumor microenvironment

High-grade brain tumors are heterogeneous with respect to the composition of bona fide tumor cells and with respect to a range of intermingling parenchymal cells. Glioblastomas harbor multiple cell types, some with increased tumorigenicity and stem cell-like capacity. The stem-like cells maybe the cells of origin for tumor relapse. However, the tumor-associated parenchymal cells such as vascular cells,microglia, peripheral immune cells, and neural precursor cells also play a vital role in controlling the course of pathology.In this review, we describe the multiple interactions of bulk glioma cells and glioma stem cells with parenchymal cell populations and highlight the pathological impact as well as signaling pathways known for these types of cell-cell communication. The tumor-vasculature not only nourishes glioblastomas, but also provides a specialized niche for these stem-like cells. In addition, microglial cells,which can contribute up to 30% of a brain tumor mass,play a role in glioblastoma cell invasion. Moreover, non-neoplastic astrocytes can be converted into a reactive phenotype by the glioma microenvironment and can then secrete a number of factors which influences tumor biology. The young brain may have the capacity to inhibit gliomagenesis by the endogenous neural precursor cells, which secrete tumor suppressive factors. The factors, pathways, and interactions described in this review provide a new prospective on the cell biology of primary brain tumors, which may ultimately generate new treatment modalities. However, our picture of the multiple interactions between parenchymal and tumor cells is still incomplete.

Transforming growth factor-Beta and urokinase-type plasminogen activator: dangerous partners in tumorigenesis-implications in skin cancer

Transforming growth factor-beta (TGF-β) is a pleiotropic factor, with several different roles in health and disease. TGF-β has been postulated as a dual factor in tumor progression, since it represses epithelial tumor development in early stages, whereas it stimulates tumor progression in advanced stages. During tumorigenesis, cancer cells acquire the capacity to migrate and invade surrounding tissues and to metastasize different organs. The urokinase-type plasminogen activator (uPA) system, comprising uPA, the uPA cell surface receptor, and plasminogen-plasmin, is involved in the proteolytic degradation of the extracellular matrix and regulates key cellular events by activating intracellular signal pathways, which together allow cancer cells to survive, thus, enhancing cell malignance during tumor progression. Due to their importance, uPA and its receptor are tightly transcriptionally regulated in normal development, but are deregulated in cancer, when their activity and expression are related to further development of cancer. TGF-β regulates uPA expression in cancer cells, while uPA, by plasminogen activation, may activate the secreted latent TGF-β, thus, producing a pernicious cycle which contributes to the enhancement of tumor progression. Here we review the specific roles and the interplay between TGF-β and uPA system in cancer cells and their implication in skin cancer.

TGFβ restores hematopoietic homeostasis after myelosuppressive chemotherapy

Blocking TGFβ signaling after chemotherapy accelerates hematopoietic reconstitution and delays the return of cycling HSCs to quiescence.

Myelosuppression is a life-threatening complication of antineoplastic therapy, but treatment is restricted to a few cytokines with unilineage hematopoietic activity. Although hematopoietic stem cells (HSCs) are predominantly quiescent during homeostasis, they are rapidly recruited into cell cycle by stresses, including myelosuppressive chemotherapy. Factors that induce HSCs to proliferate during stress have been characterized, but it is not known how HSC quiescence is then reestablished. In this study, we show that TGFβ signaling is transiently activated in hematopoietic stem and progenitor cells (HSPCs) during hematopoietic regeneration. Blockade of TGFβ signaling after chemotherapy accelerates hematopoietic reconstitution and delays the return of cycling HSCs to quiescence. In contrast, TGFβ blockade during homeostasis fails to induce cycling of HSPCs. We identified the cyclin-dependent kinase inhibitor Cdkn1c (p57) as a key downstream mediator of TGFβ during regeneration because the recovery of chimeric mice, incapable of expressing p57 in HSPCs, phenocopies blockade of TGFβ signaling after chemotherapy. This study demonstrates that context-dependent activation of TGFβ signaling is central to an unrecognized counterregulatory mechanism that promotes homeostasis once hematopoiesis has sufficiently recovered from myelosuppressive chemotherapy. These results open the door to new, potentially superior, approaches to promote multilineage hematopoietic recovery by blocking the TGFβ signaling that dampens regeneration.

Acute alcohol-induced liver injury

Alcohol consumption is customary in most cultures and alcohol abuse is common worldwide. For example, more than 50% of Americans consume alcohol, with an estimated 23.1% of Americans participating in heavy and/or binge drinking at least once a month. A safe and effective therapy for alcoholic liver disease (ALD) in humans is still elusive, despite significant advances in our understanding of how the disease is initiated and progresses. It is now clear that acute alcohol binges not only can be acutely toxic to the liver, but also can contribute to the chronicity of ALD. Potential mechanisms by which acute alcohol causes damage include steatosis, dysregulated immunity and inflammation, and altered gut permeability. Recent interest in modeling acute alcohol exposure has yielded new insights into potential mechanisms of acute injury, which also may well be relevant for chronic ALD. Recent work by this group on the role of PAI-1 and fibrin metabolism in mediating acute alcohol-induced liver damage serve as an example of possible new targets that may be useful for alcohol abuse, be it acute or chronic.

Impact of endothelial cells on 3D cultured smooth muscle cells in a biomimetic hydrogel

For the development of vascular tissue engineering, the impact of endothelial cells (ECs) on smooth muscle cell (SMC) spreading, proliferation, and differentiation is explored in the current study using a coculture model. In this coculture model, SMCs were encapsulated in a biomimetic hydrogel based on methacrylated dextran-graft-lysine (Dex-MA-LA) and methacrylamide-modified gelatin (Gel-MA), and exposed to a monolayer of ECs. With EC coculture, SMC proliferation in 3D hydrogel was promoted at initial period, and the formation of denser cellular networks was enhanced. ECs dynamically modulated SMC phenotype by promoting a more contractile SMC phenotype initially (on day 2), indicated by the upregulated expression of contractile genes α-actin, calponin, smooth muscle-myosin heavy chain (SM-MHC), and smoothelin; however, the onset of maximum expressions was delayed by ECs. Full differentiation of SMCs was not obtained even with EC coculture. Higher level of platelet-derived growth factor (PDGF)-BB and latent transforming growth factor (TGF)-β1 were detected in medium of coculture. These biochemical cues together with the physical cue of tensional force within cellular networks may be responsible for the dynamic modulation of SMC phenotype in coculture. Synthesis of elastin was promoted by ECs at transcriptional level. The formation of denser cellular networks and synthesis of elastin suggest that coculture with ECs is a potential method to construct functional vessel media layer in vitro.

Alcoholic liver disease and the potential role of plasminogen activator inhibitor-1 and fibrin metabolism

Plasminogen activator inhibitor-1 (PAI-1) is a major player in fibrinolysis due to its classical role of inhibiting plasminogen activators. Although increased fibrinolysis is common in alcoholic cirrhosis, decreased fibrinolysis (driven mostly by elevated levels of PAI-1) is common during the development of alcoholic liver disease (ALD). However, whether or not PAI-1 plays a causal role in the development of early ALD was unclear. Recent studies in experimental models have suggested that PAI-1 may contribute to the development of early (steatosis), intermediate (steatohepatitis) and late (fibrosis) stages of ALD. For example, fatty liver owing to both acute and chronic ethanol was blunted by the genetic inhibition of PAI-1. This effect of targeting PAI-1 appears to be mediated, at least in part, by an increase in very low-density lipoprotein (VLDL) synthesis in the genetic absence of this acute phase protein. Results from a two-hit model employing ethanol and lipopolysaccharide administration suggest that PAI-1 plays a critical role in hepatic inflammation, most likely due to its ability to cause fibrin accumulation, which subsequently sensitizes the liver to ensuing damaging insults. Lastly, the role of PAI-1 in hepatic fibrosis is less clear and appears that PAI-1 may serve a dual role in this pathological change, both protective (enhancing regeneration) and damaging (blocking matrix degradation). In summary, results from these studies suggest that PAI-1 may play multiple roles in the various stages of ALD, both protective and damaging. The latter effect is mediated by its influence on steatosis (i.e. decreasing VLDL synthesis), inflammation (i.e. impairing fibrinolysis) and fibrosis (i.e. blunting matrix degradation), whereas the former is mediated by maintaining hepatocyte division after an injury.

Biological Significance of Local TGF-β Activation in Liver Diseases

The cytokine transforming growth factor-β (TGF-β) plays a pivotal role in a diverse range of cellular responses, including cell proliferation, apoptosis, differentiation, migration, adhesion, angiogenesis, stimulation of extracellular matrix (ECM) synthesis, and downregulation of ECM degradation. TGF-β and its receptors are ubiquitously expressed by most cell types and tissues in vivo. In intact adult tissues and organs, TGF-β is secreted in a biologically inactive (latent) form associated in a non-covalent complex with the ECM. In response to injury, local latent TGF-β complexes are converted into active TGF-β according to a tissue- and injury type-specific activation mechanism. Such a well and tightly orchestrated regulation in TGF-β activity enables an immediate, highly localized response to type-specific tissue injury. In the pathological process of liver fibrosis, TGF-β plays as a master profibrogenic cytokine in promoting activation and myofibroblastic differentiation of hepatic stellate cells, a central event in liver fibrogenesis. Continuous and/or persistent TGF-β signaling induces sustained production of ECM components and of tissue inhibitor of metalloproteinase synthesis. Therefore, the regulation of locally activated TGF-β levels is increasingly recognized as a therapeutic target for liver fibrogenesis. This review summarizes our present knowledge of the activation mechanisms and bioavailability of latent TGF-β in biological and pathological processes in the liver.

Role of reactive oxygen and nitrogen species in the vascular responses to inflammation

Inflammation is a complex and potentially life-threatening condition that involves the participation of a variety of chemical mediators, signaling pathways, and cell types. The microcirculation, which is critical for the initiation and perpetuation of an inflammatory response, exhibits several characteristic functional and structural changes in response to inflammation. These include vasomotor dysfunction (impaired vessel dilation and constriction), the adhesion and transendothelial migration of leukocytes, endothelial barrier dysfunction (increased vascular permeability), blood vessel proliferation (angiogenesis), and enhanced thrombus formation. These diverse responses of the microvasculature largely reflect the endothelial cell dysfunction that accompanies inflammation and the central role of these cells in modulating processes as varied as blood flow regulation, angiogenesis, and thrombogenesis. The importance of endothelial cells in inflammation-induced vascular dysfunction is also predicated on the ability of these cells to produce and respond to reactive oxygen and nitrogen species. Inflammation seems to upset the balance between nitric oxide and superoxide within (and surrounding) endothelial cells, which is necessary for normal vessel function. This review is focused on defining the molecular targets in the vessel wall that interact with reactive oxygen species and nitric oxide to produce the characteristic functional and structural changes that occur in response to inflammation. This analysis of the literature is consistent with the view that reactive oxygen and nitrogen species contribute significantly to the diverse vascular responses in inflammation and supports efforts that are directed at targeting these highly reactive species to maintain normal vascular health in pathological conditions that are associated with acute or chronic inflammation.

Vascular damage in the central nervous system: a multifaceted role for vascular-derived TGF-β

The brain function depends on a continuous supply of blood. The blood-brain barrier (BBB), which is formed by vascular cells and glia, separates components of the circulating blood from neurons and maintains the precisely regulated brain milieu required for proper neuronal function. A compromised BBB alters the transport of molecules between the blood and brain and has been associated with or shown to precede neurodegenerative disease. Blood components immediately leak into the brain after mechanical damage or as a consequence of a compromised BBB in brain disease changing the extracellular environment at sites of vascular damage. It is intriguing how blood-derived components alter the cellular and molecular constituents of the neurovascular interface after BBB opening. We recently identified an unexpected role for the blood protein fibrinogen, which is deposited in the nervous system promptly after vascular damage, as an initial scar inducer by promoting the availability of active TGF-β. Fibrinogen-bound latent TGF-β interacts with astrocytes, leading to active TGF-β formation and activation of the TGF-β/Smad signaling pathway. Here, we discuss the pleiotropic effects of potentially vascular-derived TGF-β on cells at the neurovascular interface and we speculate how these biological effects might contribute to degeneration and regeneration processes. Summarizing the effects of the components derived from the brain vascular system on nervous system regeneration might support the development of new therapeutic approaches.

The regulatory function of SPARC in vascular biology

SPARC is a matricellular protein, able to modulate cell/ECM interactions and influence cell responses to growth factors, and therefore is particularly attuned to contribute to physiological processes involving changes in ECM and cell mobilization. Indeed, the list of biological processes affected by SPARC includes wound healing, tumor progression, bone formation, fibrosis, and angiogenesis. The process of angiogenesis is complex and involves a number of cellular processes such as endothelial cell proliferation, migration, ECM degradation, and synthesis, as well as pericyte recruitment to stabilize nascent vessels. In this review, we will summarize current results that explore the function of SPARC in the regulation of angiogenic events with a particular emphasis on the modulation of growth factor activity by SPARC in the context of blood vessel formation. The primary function of SPARC in angiogenesis remains unclear, as SPARC activity in some circumstances promotes angiogenesis and in others is more consistent with an anti-angiogenic activity. Undoubtedly, the mercurial nature of SPARC belies a redundancy of functional proteins in angiogenesis as well as cell-type-specific activities that alter signal transduction events in response to unique cellular milieus. Nonetheless, the investigation of cellular mechanisms that define functional activities of SPARC continue to contribute novel and exciting paradigms to vascular biology.

The brain tumor microenvironment

High-grade brain tumors are heterogeneous with respect to the composition of bona fide tumors cells and with respect to a range of intermingling parenchymal cells. Glioblastomas harbor multiple cell types, some with increased tumorigenicity and stem cell-like capacity. The stem-like cells may be the cells of origin for tumor relapse. However, the tumor-associated parenchymal cells-such as vascular cells, microglia, peripheral immune cells, and neural precursor cells-also play a vital role in controlling the course of pathology. In this review, we describe the multiple interactions of bulk glioma cells and glioma stem cells with parenchymal cell populations and highlight the pathological impact and signaling pathways known for these types of cell-cell communication. The tumor-vasculature not only nourishes glioblastomas, but also provides a specialized niche for these stem-like cells. In addition, microglial cells, which can contribute up to 30% of a brain tumor mass, play a role in glioblastoma cell invasion. Moreover, non-neoplastic astrocytes can be converted into a reactive phenotype by the glioma microenvironment and can then secrete a number of factors which influences tumor biology. The young brain may have the capacity to inhibit gliomagenesis by the endogenous neural stem and progenitor cells, which secrete tumor suppressive factors. The factors, pathways, and interactions described in this review provide a new prospective on the cell biology of primary brain tumors, which may ultimately generate new treatment modalities. However, our picture of the multiple interactions between parenchymal and tumor cells is still incomplete. © 2011 Wiley-Liss, Inc.

Quantification and regulation of cell migration

Cell migration is essential for many physiological and pathological processes that include embryonic development, the immune response, wound healing, angiogenesis, and cancer metastasis. It is also important for emerging tissue engineering applications such as tissue reconstitution and the colonization of biomedical implants. By summarizing results from recent experimental and theoretical studies, this review outlines the role played by growth factors or substrate-adhesion molecules in modulating cell motility and shows that cell motility can be an important factor in determining the rates of tissue formation. The application of cell motility assays and the use of theoretical models for analyzing cell migration and proliferation are also discussed.

Brain pericytes: emerging concepts and functional roles in brain homeostasis

Brain pericytes are an important constituent of neurovascular unit. They encircle endothelial cells and contribute to the maturation and stabilization of the capillaries in the brain. Recent studies have revealed that brain pericytes play pivotal roles in a variety of brain functions, such as regulation of capillary flow, angiogenesis, blood brain barrier, immune responses, and hemostasis. In addition, brain pericytes are pluripotent and can differentiate into different lineages similar to mesenchymal stem cells. The brain pericytes are revisited as a key player to maintain brain function and repair brain damage.

Human cytomegalovirus induces TGF-β1 activation in renal tubular epithelial cells after epithelial-to-mesenchymal transition

Human cytomegalovirus (HCMV) infection is associated epidemiologically with poor outcome of renal allografts due to mechanisms which remain largely undefined. Transforming growth factor-β1 (TGF-β1), a potent fibrogenic cytokine, is more abundant in rejecting renal allografts that are infected with either HCMV or rat CMV as compared to uninfected, rejecting grafts. TGF-β1 induces renal fibrosis via epithelial-to-mesenchymal transition (EMT) of renal epithelial cells, a process by which epithelial cells acquire mesenchymal characteristics and a migratory phenotype, and secrete molecules associated with extracellular matrix deposition and remodeling. We report that human renal tubular epithelial cells infected in vitro with HCMV and exposed to TGF-β1 underwent morphologic and transcriptional changes of EMT, similar to uninfected cells. HCMV infected cells after EMT also activated extracellular latent TGF-β1 via induction of MMP-2. Renal epithelial cells transiently transfected with only the HCMV IE1 or IE2 open reading frames and stimulated to undergo EMT also induced TGF-β1 activation associated with MMP-2 production, suggesting a role for these viral gene products in MMP-2 production. Consistent with the function of these immediate early gene products, the antiviral agents ganciclovir and foscarnet did not inhibit TGF-β1 production after EMT by HCMV infected cells. These results indicate that HCMV infected renal tubular epithelial cells can undergo EMT after exposure to TGF-β1, similar to uninfected renal epithelial cells, but that HCMV infection by inducing active TGF-β1 may potentiate renal fibrosis. Our findings provide in vitro evidence for a pathogenic mechanism that could explain the clinical association between HCMV infection, TGF-β1, and adverse renal allograft outcome.

Human cytomegalovirus (HCMV) is a common virus that establishes lifelong persistence in the host. Although asymptomatic in healthy people, HCMV can reactivate and cause disease in immunosuppressed patients, such as those undergoing kidney transplantation. HCMV infection is associated with inferior renal allograft survival compared to transplants without HCMV infection. HCMV infected allografts also contain higher levels of the fibrogenic cytokine, transforming growth factor-β1 (TGF-β1), compared to uninfected allografts. TGF-β1 is a potent inducer of renal fibrosis and causes epithelial-to-mesenchymal transition (EMT), whereby epithelial cells acquire characteristics of cells of mesenchymal origin and express molecules associated with fibrosis. Our work shows that renal epithelial cells infected in vitro with HCMV can undergo EMT, but that HCMV infected cells produce greater amounts of the fibrogenic molecule TGF-β1, compared to uninfected cells after EMT. We have shown that this effect is likely due to specific HCMV genes (IE1, IE2), and cannot be prevented by administration of antivirals such as ganciclovir or foscarnet. These data suggest that HCMV may contribute to adverse renal allograft outcome by exacerbating TGF-β1 induced renal fibrosis. Understanding such mechanisms will permit the development of treatments that could improve long-term renal allograft survival in HCMV infected patients.

Proteasomal regulation of pulmonary fibrosis

It is estimated that, combined, 400,000 people are diagnosed with idiopathic pulmonary fibrosis (IPF) or acute lung injury/acute respiratory distress syndrome annually in the United States, and both diseases are associated with an unacceptably high mortality rate. Although these disorders are distinct clinical entities, they share pathogenic mechanisms that may provide overlapping therapeutic targets. One example is fibroblast activation, which occurs concomitant with acute lung injury as well as in the progressive fibrosis of IPF. Both clinical entities are characterized by elevations of the profibrotic cytokine, transforming growth factor (TGF)-beta1. Protein degradation by the ubiquitin-proteasomal system modulates TGF-beta1 expression and signaling. In this review, we highlight the effects of proteasomal inhibition in various animal models of tissue fibrosis and mechanisms by which it may regulate TGF-beta1 expression and signaling. At present, there are no effective therapies for fibroproliferative acute respiratory distress syndrome or IPF, and proteasomal inhibition may provide a novel, attractive target in these devastating diseases.

Diverse roles of the vasculature within the neural stem cell niche

An interdependent relationship between the vascular and nervous systems begins during the earliest stages of development and persists through the mammalian lifespan. Accordingly, the process of adult neurogenesis involves the coordinated response of both systems to maintain a specialized microenvironment (niche) that tips the scale towards maintenance or regeneration, as needed. Understanding the nature and regulation of this balance will provide a foundation on which the potential for molecular- and stem cell-based therapies can be developed to treat prevalent CNS diseases and disorders. The vasculature is cited as a prominent feature within the adult subventricular zone and subgranular zone, known adult neural stem cell niches, helping to retain neural stem and progenitor cell potential. The vascular compartment within the neural stem cell niche has the unique opportunity to not only regulate neural stem and progenitor cells through direct contact with, and paracrine signaling from, endothelial and mural cells that make up blood vessels, but also integrates systemic signals into the local microenvironment via distribution of soluble factors from blood circulation to regulate stem cell niche behavior. Understanding the intricate role that the vasculature plays to influence neural stem cells in the context of niche regulation will help to bridge the gap from bench to bedside for the development of regeneration-based therapies for the CNS.

Transcriptional activation of endothelial cells by TGFβ coincides with acute microvascular plasticity following focal spinal cord ischaemia/reperfusion injury

Microvascular dysfunction, loss of vascular support, ischaemia and sub-acute vascular instability in surviving blood vessels contribute to secondary injury following SCI (spinal cord injury). Neither the precise temporal profile of the cellular dynamics of spinal microvasculature nor the potential molecular effectors regulating this plasticity are well understood. TGFβ (transforming growth factor β) isoforms have been shown to be rapidly increased in response to SCI and CNS (central nervous system) ischaemia, but no data exist regarding their contribution to microvascular dysfunction following SCI. To examine these issues, in the present study we used a model of focal spinal cord ischaemia/reperfusion SCI to examine the cellular response(s) of affected microvessels from 30 min to 14 days post-ischaemia. Spinal endothelial cells were isolated from affected tissue and subjected to focused microarray analysis of TGFβ-responsive/related mRNAs 6 and 24 h post-SCI. Immunohistochemical analyses of histopathology show neuronal disruption/loss and astroglial regression from spinal microvessels by 3 h post-ischaemia, with complete dissolution of functional endfeet (loss of aquaporin-4) by 12 h post-ischaemia. Coincident with this microvascular plasticity, results from microarray analyses show 9 out of 22 TGFβ-responsive mRNAs significantly up-regulated by 6 h post-ischaemia. Of these, serpine 1/PAI-1 (plasminogen-activator inhibitor 1) demonstrated the greatest increase (>40-fold). Furthermore, uPA (urokinase-type plasminogen activator), another member of the PAS (plasminogen activator system), was also significantly increased (>7.5-fold). These results, along with other select up-regulated mRNAs, were confirmed biochemically or immunohistochemically. Taken together, these results implicate TGFβ as a potential molecular effector of the anatomical and functional plasticity of microvessels following SCI.

Insulin acts through FOXO3a to activate transcription of plasminogen activator inhibitor type 1

Plasminogen activator inhibitor-1 (PAI-1) is an important regulator of fibrinolysis. PAI-1 levels are elevated in type 2 diabetes, and this elevation correlates with macro- and microvascular complications of diabetes. However, the mechanistic link between insulin and up-regulation of PAI-1 is unclear. Here we demonstrate that overexpression of Forkhead-related transcription factor (Fox)O1, FoxO3a, and FoxC1 augment insulin's ability to activate the PAI-1 promoter. In addition, insulin treatment promotes the phosphorylation of nuclear and cytoplasmic Fox03a and an increase of cytoplasmic Fox03a. In contrast, insulin treatment led to the accumulation of phospho-Fox01 only in the cytoplasm. Furthermore, insulin also increased the ability of chimeric LexA-FoxO1, LexA-FoxO3a, and LexA-FoxC1 proteins to increase the activity of a LexA reporter, suggesting that the effect of insulin on FoxO3a was direct. Using small interfering RNA to specifically deplete each of the Fox transcription factors tested, we demonstrate that only reduction of FoxO3a inhibits insulin-increased PAI-1-Luc expression and PAI-1 mRNA accumulation. Finally, chromatin immunoprecipitation assays confirm the presence of FoxO3a on the PAI-1 promoter. These results suggest that FoxO3a mediates insulin-increased PAI-1 gene expression.