Vascular MADs: two novel MAD-related genes selectively inducible by flow in human vascular endothelium

Endothelial cell SMAD6 balances Alk1 function to regulate adherens junctions and hepatic vascular development

BMP signaling is crucial to blood vessel formation and function, but how pathway components regulate vascular development is not well-understood. Here, we find that inhibitory SMAD6 functions in endothelial cells to negatively regulate ALK1-mediated responses, and it is required to prevent vessel dysmorphogenesis and hemorrhage in the embryonic liver vasculature. Reduced Alk1 gene dosage rescued embryonic hepatic hemorrhage and microvascular capillarization induced by Smad6 deletion in endothelial cells in vivo. At the cellular level, co-depletion of Smad6 and Alk1 rescued the destabilized junctions and impaired barrier function of endothelial cells depleted for SMAD6 alone. Mechanistically, blockade of actomyosin contractility or increased PI3K signaling rescued endothelial junction defects induced by SMAD6 loss. Thus, SMAD6 normally modulates ALK1 function in endothelial cells to regulate PI3K signaling and contractility, and SMAD6 loss increases signaling through ALK1 that disrupts endothelial cell junctions. ALK1 loss-of-function also disrupts vascular development and function, indicating that balanced ALK1 signaling is crucial for proper vascular development and identifying ALK1 as a 'Goldilocks' pathway in vascular biology that requires a certain signaling amplitude, regulated by SMAD6, to function properly.

Endothelial Cell SMAD6 Balances ACVRL1/Alk1 Function to Regulate Adherens Junctions and Hepatic Vascular Development

BMP signaling is critical to blood vessel formation and function, but how pathway components regulate vascular development is not well-understood. Here we find that inhibitory SMAD6 functions in endothelial cells to negatively regulate ALK1/ACVRL1-mediated responses, and it is required to prevent vessel dysmorphogenesis and hemorrhage in the embryonic liver vasculature. Reduced Alk1 gene dosage rescued embryonic hepatic hemorrhage and microvascular capillarization induced by Smad6 deletion in endothelial cells in vivo . At the cellular level, co-depletion of Smad6 and Alk1 rescued the destabilized junctions and impaired barrier function of endothelial cells depleted for SMAD6 alone. At the mechanistic level, blockade of actomyosin contractility or increased PI3K signaling rescued endothelial junction defects induced by SMAD6 loss. Thus, SMAD6 normally modulates ALK1 function in endothelial cells to regulate PI3K signaling and contractility, and SMAD6 loss increases signaling through ALK1 that disrupts endothelial junctions. ALK1 loss-of-function also disrupts vascular development and function, indicating that balanced ALK1 signaling is crucial for proper vascular development and identifying ALK1 as a "Goldilocks" pathway in vascular biology regulated by SMAD6.

Adjustable Thermo-Responsive, Cell-Adhesive Tissue Engineering Scaffolds for Cell Stimulation through Periodic Changes in Culture Temperature

A three-dimensional (3D) scaffold ideally provides hierarchical complexity and imitates the chemistry and mechanical properties of the natural cell environment. Here, we report on a stimuli-responsive photo-cross-linkable resin formulation for the fabrication of scaffolds by continuous digital light processing (cDLP), which allows for the mechano-stimulation of adherent cells. The resin comprises a network-forming trifunctional acrylate ester monomer (trimethylolpropane triacrylate, or TMPTA), N-isopropyl acrylamide (NiPAAm), cationic dimethylaminoethyl acrylate (DMAEA) for enhanced cell interaction, and 4-acryloyl morpholine (AMO) to adjust the phase transition temperature (T_trans) of the equilibrium swollen cross-polymerized scaffold. With glycofurol as a biocompatible solvent, controlled three-dimensional structures were fabricated and the transition temperatures were adjusted by resin composition. The effects of the thermally induced mechano-stimulation were investigated with mouse fibroblasts (L929) and myoblasts (C2C12) on printed constructs. Periodic changes in the culture temperature stimulated the myoblast proliferation.

Nuclear Mechanosensation and Mechanotransduction in Vascular Cells

Vascular cells are constantly subjected to physical forces associated with the rhythmic activities of the heart, which combined with the individual geometry of vessels further imposes oscillatory, turbulent, or laminar shear stresses on vascular cells. These hemodynamic forces play an important role in regulating the transcriptional program and phenotype of endothelial and smooth muscle cells in different regions of the vascular tree. Within the aorta, the lesser curvature of the arch is characterized by disturbed, oscillatory flow. There, endothelial cells become activated, adopting pro-inflammatory and athero-prone phenotypes. This contrasts the descending aorta where flow is laminar and endothelial cells maintain a quiescent and atheroprotective phenotype. While still unclear, the specific mechanisms involved in mechanosensing flow patterns and their molecular mechanotransduction directly impact the nucleus with consequences to transcriptional and epigenetic states. The linker of nucleoskeleton and cytoskeleton (LINC) protein complex transmits both internal and external forces, including shear stress, through the cytoskeleton to the nucleus. These forces can ultimately lead to changes in nuclear integrity, chromatin organization, and gene expression that significantly impact emergence of pathology such as the high incidence of atherosclerosis in progeria. Therefore, there is strong motivation to understand how endothelial nuclei can sense and respond to physical signals and how abnormal responses to mechanical cues can lead to disease. Here, we review the evidence for a critical role of the nucleus as a mechanosensor and the importance of maintaining nuclear integrity in response to continuous biophysical forces, specifically shear stress, for proper vascular function and stability.

Neuropilin-1 deficiency in vascular smooth muscle cells is associated with hereditary hemorrhagic telangiectasia arteriovenous malformations

Patients with hereditary hemorrhagic telangiectasia (HHT) have arteriovenous malformations (AVMs) with genetic mutations involving the activin-A receptor like type 1 (ACVRL1 or ALK1) and endoglin (ENG). Recent studies have shown that Neuropilin-1 (NRP-1) inhibits ALK1. We investigated the expression of NRP-1 in livers of patients with HHT and found that there was a significant reduction in NRP-1 in perivascular smooth muscle cells (SMCs). We used Nrp1^SM22KO mice (Nrp1 was ablated in SMCs) and found hemorrhage, increased immune cell infiltration with a decrease in SMCs, and pericyte lining in lungs and liver in adult mice. Histologic examination revealed lung arteriovenous fistulas (AVFs) with enlarged liver vessels. Evaluation of the retina vessels at P5 from Nrp1^SM22KO mice demonstrated dilated capillaries with a reduction of pericytes. In inflow artery of surgical AVFs from the Nrp1^SM22KO versus WT mice, there was a significant decrease in Tgfb1, Eng, and Alk1 expression and phosphorylated SMAD1/5/8 (pSMAD1/5/8), with an increase in apoptosis. TGF-β1–stimulated aortic SMCs from Nrp1^SM22KO versus WT mice have decreased pSMAD1/5/8 and increased apoptosis. Coimmunoprecipitation experiments revealed that NRP-1 interacts with ALK1 and ENG in SMCs. In summary, NRP-1 deletion in SMCs leads to reduced ALK1, ENG, and pSMAD1/5/8 signaling and reduced cell death associated with AVM formation.

SHED‐derived exosomes improve the repair capacity and osteogenesis potential of hPDLCs

OBJECTIVE

Exosomes secreted by stem cells are recognized as a critical component in tissue regeneration during stem cell-based therapy. Considering the limited sources and bone regeneration efficiency of human periodontal ligament cells (hPDLCs), we explored whether exosomes secreted by stem cells from human exfoliated deciduous teeth (SHED-exo) could improve the pluripotency and regenerative potential of hPDLCs.

METHODS AND MATERIALS

In hPDLCs, cell proliferation, migration, cell cycle, apoptosis, and osteogenic differentiation were detected after cells were exposed to SHED-exo (SHED-exo group), blank (control group), or control supernatant without exo (Csup group), via CCK-8, scratch analysis, flow cytometric, real-time PCR, and so on. Exosomes sequencing was performed to compare and analyze miRNAs contented in SHED-exo and hPDLC-exo.

RESULTS

As compared to control or Csup, SHED-exo significantly increased migration, apoptosis, and proliferation, promoted cell cycle transition from G1 to S phase in hPDLCs, and enhanced Runx2 expression and mineralization. In addition, it may be explained by the significant differences in miRNA contented in SHED-exo and hPDLC-exo.

CONCLUSION

Exosomes from SHED can improve cell proliferation, migration, cell cycle, apoptosis, and osteogenic differentiation of hPDLCs, which highlights the therapeutic value of this bioactive component in the regeneration of periodontal tissues using hPDLCs in clinical practice.

The versatility and paradox of BMP signaling in endothelial cell behaviors and blood vessel function

Blood vessels expand via sprouting angiogenesis, and this process involves numerous endothelial cell behaviors, such as collective migration, proliferation, cell–cell junction rearrangements, and anastomosis and lumen formation. Subsequently, blood vessels remodel to form a hierarchical network that circulates blood and delivers oxygen and nutrients to tissue. During this time, endothelial cells become quiescent and form a barrier between blood and tissues that regulates transport of liquids and solutes. Bone morphogenetic protein (BMP) signaling regulates both proangiogenic and homeostatic endothelial cell behaviors as blood vessels form and mature. Almost 30 years ago, human pedigrees linked BMP signaling to diseases associated with blood vessel hemorrhage and shunts, and recent work greatly expanded our knowledge of the players and the effects of vascular BMP signaling. Despite these gains, there remain paradoxes and questions, especially with respect to how and where the different and opposing BMP signaling outputs are regulated. This review examines endothelial cell BMP signaling in vitro and in vivo and discusses the paradox of BMP signals that both destabilize and stabilize endothelial cell behaviors.

BMP9 and BMP10: two close vascular quiescence partners that stand out

Bone morphogenetic proteins (BMPs) are dimeric transforming growth factor ß (TGFß) family cytokines that were first described in bone and cartilage formation but have since been shown to be involved in many pleiotropic functions. In human, there are 15 BMP ligands, which initiate their cellular signaling by forming a complex with two copies of type I receptors and two copies of type II receptors, both of which are transmembrane receptors with an intracellular serine/threonine kinase domain. Within this receptor family, ALK1 (Activin receptor-Like Kinase 1), which is a type I receptor mainly expressed on endothelial cells, and BMPRII (BMP Receptor type II), a type II receptor also highly expressed on endothelial cells, have been directly linked to two rare vascular diseases: hereditary haemorrhagic telangiectasia (HHT), and pulmonary arterial hypertension (PAH), respectively. BMP9 (gene name GDF2) and BMP10, two close members of the BMP family, are the only known ligands for the ALK1 receptor. This specificity gives them a unique role in physiological and pathological angiogenesis and tissue homeostasis. The aim of this current review is to present an overview of what is known about BMP9 and BMP10 on vascular regulation with a particular emphasis on recent results and the many questions that remain unanswered regarding the roles and specificities between BMP9 and BMP10. This article is protected by copyright. All rights reserved.

Transforming growth factor beta signaling functions during mammalian kidney development

Aberrant transforming growth factor beta (TGFβ) signaling during embryogenesis is implicated in severe congenital abnormalities, including kidney malformations. However, the molecular mechanisms that underlie congenital kidney malformations related to TGFβ signaling remain poorly understood. Here, we review current understanding of the lineage-specific roles of TGFβ signaling during kidney development and how dysregulation of TGFβ signaling contributes to the pathogenesis of kidney malformation.

SMAD6 transduces endothelial cell flow responses required for blood vessel homeostasis

Fluid shear stress provided by blood flow instigates a transition from active blood vessel network expansion during development, to vascular homeostasis and quiescence that is important for mature blood vessel function. Here we show that SMAD6 is required for endothelial cell flow-mediated responses leading to maintenance of vascular homeostasis. Concomitant manipulation of the mechanosensor Notch1 pathway and SMAD6 expression levels revealed that SMAD6 functions downstream of ligand-induced Notch signaling and transcription regulation. Mechanistically, full-length SMAD6 protein was needed to rescue Notch loss-induced flow misalignment. Endothelial cells depleted for SMAD6 had defective barrier function accompanied by upregulation of proliferation-associated genes and down regulation of junction-associated genes. The vascular protocadherin PCDH12 was upregulated by SMAD6 and required for proper flow-mediated endothelial cell alignment, placing it downstream of SMAD6. Thus, SMAD6 is a required transducer of flow-mediated signaling inputs downstream of Notch1 and upstream of PCDH12, as vessels transition from an angiogenic phenotype to maintenance of a homeostatic phenotype.

Current perspectives on inhibitory SMAD7 in health and disease

Transforming growth factor β (TGF-β) family members play an extensive role in cellular communication that orchestrates both early development and adult tissue homeostasis. Aberrant TGF-β family signaling is associated with a pathological outcome in numerous diseases, and in-depth understanding of molecular and cellular processes could result in therapeutic benefit for patients. Canonical TGF-β signaling is mediated by receptor-regulated SMADs (R-SMADs), a single co-mediator SMAD (Co-SMAD), and inhibitory SMADs (I-SMADs). SMAD7, one of the I-SMADs, is an essential negative regulator of the pleiotropic TGF-β and bone morphogenetic protein (BMP) signaling pathways. In a negative feedback loop, SMAD7 inhibits TGF-β signaling by providing competition for TGF-β type-1 receptor (TβRI), blocking phosphorylation and activation of SMAD2. Moreover, SMAD7 recruits E3 ubiquitin SMURF ligases to the type I receptor to promote ubiquitin-mediated proteasomal degradation. In addition to its role in TGF-β and BMP signaling, SMAD7 is regulated by and implicated in a variety of other signaling pathways and functions as a mediator of crosstalk. This review is focused on SMAD7, its function in TGF-β and BMP signaling, and its role as a downstream integrator and crosstalk mediator. This crucial signaling molecule is tightly regulated by various mechanisms. We provide an overview of the ways by which SMAD7 is regulated, including noncoding RNAs (ncRNAs) and post-translational modifications (PTMs). Finally, we discuss its role in diseases, such as cancer, fibrosis, and inflammatory bowel disease (IBD).

Syndecan-1 regulates extracellular matrix expression in keloid fibroblasts via TGF-β1/Smad and MAPK signaling pathways

AIMS

The present study aimed to explore the effect of syndecan-1 on keloid fibroblasts.

MAIN METHODS

Immunohistochemistry and Western blot were employed to assess the expression of syndecan-1. Primary cultured keloid fibroblasts were transfected with syndecan-1 siRNA. The function of syndecan-1 on the proliferation of keloid fibroblasts was investigated through Cell Counting Kit-8 (CCK-8) and flow cytometry. Extracellular matrix, TGF-β1/Smad, and MAPK related proteins were evaluated by Western blot.

KEY FINDINGS

Syndecan-1 was significantly overexpressed in both keloid tissues and fibroblasts. Moreover, the knockdown of syndecan-1 remarkably attenuated the proliferation of keloid fibroblasts and reduced the content of the extracellular matrix. Importantly, syndecan-1 regulates the expression of the extracellular matrix in keloid fibroblasts via TGF-β1/Smad and mitogen-activated protein kinase (MAPK) signaling pathways.

SIGNIFICANCE

The current results revealed a crucial function for syndecan-1 in regulating the expression of extracellular matrix and cell proliferation, thereby designating syndecan-1 as a novel target for keloid.

Evaluating medical device and material thrombosis under flow: current and emerging technologies

This review highlights the importance of flow in medical device thrombosis and explores current and emerging technologies to evaluate dynamic biomaterial Thrombosis in vitro.

Bicuspid aortic valve-associated aortopathy: Where do we stand?

Herein we summarize the current knowledge on the bicuspid aortic valve (BAV)-associated aortopathy regarding clinical presentation and disease sub-classification, genetic background, hemodynamics, histopathology, cells and signaling, animal models, and biomarkers. Despite enormous efforts in research in all of the above areas, important issues remain unknown: (i) what is the ontogenetic basis of BAV development? (ii) how can we explain the diversity of BAV and associated aortopathy phenotypes? (iii) what are the signaling processes in aortopathy pathogenesis and how can we interfere with these processes? Despite undoubtedly great progress that has been made in the understanding of BAV-associated aortopathy, so far researchers have put together a heap of Lego bricks, but at present it is unclear if the bricks are compatible, how they fit together, and which parts are missing to build the true model of the BAV aorta. A joint approach is needed to accelerate research progress.

TGF-β and BMPR2 Signaling in PAH: Two Black Sheep in One Family

Knowledge pertaining to the involvement of transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP) signaling in pulmonary arterial hypertension (PAH) is continuously increasing. There is a growing understanding of the function of individual components involved in the pathway, but a clear synthesis of how these interact in PAH is currently lacking. Most of the focus has been on signaling downstream of BMPR2, but it is imperative to include the role of TGF-β signaling in PAH. This review gives a state of the art overview of disturbed signaling through the receptors of the TGF-β family with respect to vascular remodeling and cardiac effects as observed in PAH. Recent (pre)-clinical studies in which these two pathways were targeted will be discussed with an extended view on cardiovascular research fields outside of PAH, indicating novel future perspectives.

Developmental SMAD6 loss leads to blood vessel hemorrhage and disrupted endothelial cell junctions

The BMP pathway regulates developmental processes including angiogenesis, yet its signaling outputs are complex and context-dependent. Recently, we showed that SMAD6, an intracellular BMP inhibitor expressed in endothelial cells, decreases vessel sprouting and branching both in vitro and in zebrafish. Genetic deletion of SMAD6 in mice results in poorly characterized cardiovascular defects and lethality. Here, we analyzed the effects of SMAD6 loss on vascular function during murine development. SMAD6 was expressed in a subset of blood vessels throughout development, primarily in arteries, while expression outside of the vasculature was largely confined to developing cardiac valves with no obvious embryonic phenotype. Mice deficient in SMAD6 died during late gestation and early stages of postnatal development, and this lethality was associated with vessel hemorrhage. Mice that survived past birth had increased branching and sprouting of developing postnatal retinal vessels and disorganized tight and adherens junctions. In vitro, knockdown of SMAD6 led to abnormal endothelial cell adherens junctions and increased VE-cadherin endocytosis, indicative of activated endothelium. Thus, SMAD6 is essential for proper blood vessel function during murine development, where it appears to stabilize endothelial junctions to prevent hemorrhage and aberrant angiogenesis.

Melatonin-mediated miR-526b-3p and miR-590-5p upregulation promotes chondrogenic differentiation of human mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (BMSCs), with inherent chondrogenic differentiation potential appear to be ideally suited for therapeutic use in cartilage regeneration. Accumulating evidence has demonstrated that melatonin can promote chondrogenic differentiation in human BMSCs. However, little is known about the mechanism. MicroRNAs (miRNAs) have been shown to regulate the differentiation of BMSCs, but their roles in melatonin-promoted chondrogenic differentiation have not been characterized. Here, we demonstrate that melatonin promoted chondrogenic differentiation of human BMSCs via upregulation of miR-526b-3p and miR-590-5p. Mechanistically, the elevated miR-526b-3p and miR-590-5p enhanced SMAD1 phosphorylation by targeting SMAD7. Additionally, administration of miR-526b-3p mimics or miR-590-5p mimics successfully promoted the chondrogenic differentiation of human BMSCs. Collectively, our study suggests that modification of BMSCs using melatonin or miRNA transduction could be an effective therapy for cartilage damage and degeneration.

SMAD7 regulates proinflammatory and prolabor mediators in amnion and myometrium

Preterm birth continues to be a significant public health problem. Infection (bacterial and or viral) and inflammation, by stimulating proinflammatory cytokines, adhesion molecules, and matrix metalloproteinase 9 (MMP9), play a central role in the rupture of membranes and myometrial contractions. SMAD7 has been implicated in regulating the inflammatory response; however, no studies have been performed with regard to human labor. In this study, we determined the effect of spontaneous human labor and prolabor mediators on SMAD7 expression in myometrium and fetal membranes. Functional studies were employed to investigate the effect of siRNA knockdown of SMAD7 (siSMAD7) in regulating infection and inflammation-induced prolabor mediators. SMAD7 mRNA and protein expression were significantly higher with spontaneous term labor, compared to no labor, in myometrium and fetal membranes. SMAD7 expression was also significantly higher in amnion from women with preterm chorioamnionitis. The proinflammatory cytokines IL1B and TNF, the bacterial product fsl-1, and the viral dsRNA analog poly(I:C) significantly increased SMAD7 in myometrial cells and amnion cells. In myometrial cells, siSMAD7 cells significantly decreased cytokine (IL6) and chemokine (CXCL1, CXCL8, CCL2 are also known as GRO-alpha, interleukin (IL)-8 and monocyte chemotactic protein-1 (MCP-1)) production induced by IL1B, TNF, and fsl-1. There was also a decrease in the expression of adhesion molecules intercellular adhesion molecule 1 (ICAM1) and vascular cell adhesion molecule 1 (VCAM1) in siSMAD7 cells, and MMP9 expression. In amnion, siSMAD7 cells treated with IL1B also decreased cytokine and chemokine production, ICAM1 and MMP9 expression. In conclusion, we report a proinflammatory role for SMAD7 in human gestational tissues, with SMAD7 silencing attenuating the inflammatory response.

SMAD proteins directly suppress PAX2 transcription downstream of transforming growth factor-beta 1 (TGF-β1) signalling in renal cell carcinoma

Canonical TGF-β1 signalling promotes tumor progression by facilitating invasion and metastasis, whereby release of TGF-β1, by (for example) infiltrating immune cells, induces epithelial to mesenchymal transition (EMT). PAX2, a member of the Paired box family of transcriptional regulators, is normally expressed during embryonic development, including in the kidney, where it promotes mesenchymal to epithelial transition (MET). PAX2 expression is silenced in many normal adult tissues. However, in contrast, PAX2 is expressed in several cancer types, including kidney, prostate, breast, and ovarian cancer. While multiple studies have implicated TGF-β superfamily members in modulating expression of Pax genes during embryonic development, few have investigated direct regulation of Pax gene expression by TGF-β1. Here we have investigated direct regulation of PAX2 expression by TGF-β1 in clear cell renal cell carcinoma (CC-RCC) cell lines. Treatment of PAX2-expressing 786-O and A498 CC-RCC cell lines with TGF-β1 resulted in inhibition of endogenous PAX2 mRNA and protein expression, as well as expression from transiently transfected PAX2 promoter constructs; this inhibition was abolished in the presence of expression of the inhibitory SMAD, SMAD7. Using ChIP-PCR we showed TGF-β1 treatment induced SMAD3 protein phosphorylation in 786-O cells, and direct SMAD3 binding to the human PAX2 promoter, which was inhibited by SMAD7 over-expression. Overall, these data suggest that canonical TGF-β signalling suppresses PAX2 transcription in CC-RCC cells due to the direct binding of SMAD proteins to the PAX2 promoter. These studies improve our understanding of tumor progression and epithelial to mesenchyme transition (EMT) in CC-RCC and in other PAX2-expressing cancer types.

The transcriptomic and epigenetic map of vascular quiescence in the continuous lung endothelium

Maintenance of a quiescent and organotypically-differentiated layer of blood vessel-lining endothelial cells (EC) is vital for human health. Yet, the molecular mechanisms of vascular quiescence remain largely elusive. Here we identify the genome-wide transcriptomic program controlling the acquisition of quiescence by comparing lung EC of infant and adult mice, revealing a prominent regulation of TGFß family members. These transcriptomic changes are distinctly accompanied by epigenetic modifications, measured at single CpG resolution. Gain of DNA methylation affects developmental pathways, including NOTCH signaling. Conversely, loss of DNA methylation preferentially occurs in intragenic clusters affecting intronic enhancer regions of genes involved in TGFβ family signaling. Functional experiments prototypically validated the strongly epigenetically regulated inhibitors of TGFβ family signaling SMAD6 and SMAD7 as regulators of EC quiescence. These data establish the transcriptional and epigenetic landscape of vascular quiescence that will serve as a foundation for further mechanistic studies of vascular homeostasis and disease-associated activation.

The vascular system is made up of vessels including arteries, capillaries and veins that carry blood throughout the body. The inner surfaces of these blood vessels are lined with a thin layer of cells, called endothelial cells, which form a barrier and a communicating interface between the circulation and the surrounding tissue.

Early in an organism’s life, when the vascular system is still growing, endothelial cells increase in number by dividing into more cells. In adulthood, as the vascular system reaches its full size, the endothelial cells maintain a stable number. As a result, an adult’s vascular system has a resting layer of endothelial cells that does not divide. This is known as vascular quiescence, and scientists know little about how the body achieves and maintains it.

To unravel the mechanisms controlling vascular quiescence, Schlereth et al. studied endothelial cells taken from blood vessels in the lungs of newborn and adult mice. By comparing all the genes present at both developmental stages, the changes of gene activity in these cells could be measured. The results showed that the activity of genes strongly correlated with so called epigenetic changes in the genes involved in vascular quiescence. These are DNA modifications that can alter the function of a gene without affecting its underlying sequence.

Two genes in particular (Smad6 and Smad7) appeared to play an important role in vascular quiescence. Their corresponding proteins, SMAD6 and SMAD7, inhibit another group of proteins (TGFβ family) important for cell growth. The results showed that the endothelial cells in adult mice produced more SMAD6 and SMAD7 than in young mice. Therefore, endothelial cells of adult mice stop to increase in number and to migrate.

For the first time ever, Schlereth et al. have provided an extensive comparative analysis of gene activity and epigenetic changes to study vascular quiescence. The findings open a new chapter of vascular biology and will serve as a foundation for future research into the mechanisms of vascular quiescence. Problems in maintaining a resting layer of cells may lead to vascular dysfunction, which is associated with a wide range of diseases, such as stroke, heart disease and cancer making it a leading cause of death. In future, scientists may be able to develop new treatments that target specific molecules to help the body achieve a resting blood vessel system.

Developing a Reliable Mouse Model for Cancer Therapy-Induced Cardiovascular Toxicity in Cancer Patients and Survivors

Background

The high incidence of cardiovascular events in cancer survivors has long been noted, but the mechanistic insights of cardiovascular toxicity of cancer treatments, especially for vessel diseases, remain unclear. It is well known that atherosclerotic plaque formation begins in the area exposed to disturbed blood flow, but the relationship between cancer therapy and disturbed flow in regulating plaque formation has not been well studied. Therefore, we had two goals for this study; (1) Generate an affordable, reliable, and reproducible mouse model to recapitulate the cancer therapy-induced cardiovascular events in cancer survivors, and (2) Establish a mouse model to investigate the interplay between disturbed flow and various cancer therapies in the process of atherosclerotic plaque formation.

Methods and Results

We examined the effects of two cancer drugs and ionizing radiation (IR) on disturbed blood flow-induced plaque formation using a mouse carotid artery partial ligation (PCL) model of atherosclerosis. We found that doxorubicin and cisplatin, which are commonly used anti-cancer drugs, had no effect on plaque formation in partially ligated carotid arteries. Similarly, PCL-induced plaque formation was not affected in mice that received IR (2 Gy) and PCL surgery performed one week later. In contrast, when PCL surgery was performed 26 days after IR treatment, not only the atherosclerotic plaque formation but also the necrotic core formation was significantly enhanced. Lastly, we found a significant increase in p90RSK phosphorylation in the plaques from the IR-treated group compared to those from the non-IR treated group.

Conclusions

Our results demonstrate that IR not only increases atherosclerotic events but also vulnerable plaque formation. These increases were a somewhat delayed effect of IR as they were observed in mice with PCL surgery performed 26 days, but not 10 days, after IR exposure. A proper animal model must be developed to study how to minimize the cardiovascular toxicity due to cancer treatment.

Ionizing Radiation Induces Endothelial Inflammation and Apoptosis via p90RSK-Mediated ERK5 S496 Phosphorylation

Adverse cardiovascular events are a leading nonmalignant cause of morbidity and mortality among cancer survivors who have been exposed to ionizing radiation (IR), but the exact mechanism of the cardiovascular complications induced by IR remains unclear. In this study we investigated the potential role of the p90RSK-ERK5 module in regulating IR-induced endothelial cell inflammation and apoptosis.

Whole body radiation of mice with 2 Gy γ-ray significantly increased endothelial VCAM-1 expression; especially in the disturbed flow area in vivo. In vitro studies showed that IR increased p90RSK activation as well as subsequent ERK5 S496 phosphorylation in cultured human endothelial cells (ECs). A specific p90RSK inhibitor, FMK-MEA, significantly inhibited both p90RSK activation and ERK5 S496 phosphorylation, but it had no effect on IR-induced ERK5 TEY motif phosphorylation, suggesting that p90RSK regulates ERK5 transcriptional activity, but not its kinase activity. In fact, we found that IR-induced NF-kB activation and VCAM-1 expression in ECs were significantly inhibited by the over-expression of S496 phosphorylation site mutant of ERK5 (ERK5 S496A) compared to overexpression of wild type ERK5. Furthermore, when ECs were exposed to IR, the number of annexin V positive cells increased, and overexpression of ERK5 S496A, but not wild type ERK5, significantly inhibited this increase.

Our results demonstrate that IR augmented disturbed flow-induced VCAM-1 expression in vivo. Endothelial p90RSK was robustly activated by IR and subsequently up-regulated ERK5 S496 phosphorylation, inflammation, and apoptosis in ECs. The EC p90RSK-ERK5 signaling axis can be a good target to prevent cardiovascular events after radiation therapy in cancer patients.

3,5,6,7,8,3',4'-Heptamethoxyflavone, a Citrus Flavonoid, Inhibits Collagenase Activity and Induces Type I Procollagen Synthesis in HDFn Cells

Citrus fruits contain various types of flavonoids with powerful anti-aging and photoprotective effects on the skin, and have thus been attracting attention as potential, efficacious skincare agents. Here, we aimed to investigate the chemical composition of Citrus unshiu and its protective effects on photoaging. We isolated and identified a bioactive compound, 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF), from C. unshiu peels using ethanol extraction and hexane fractionation. HMF inhibited collagenase activity and increased type I procollagen content in UV-induced human dermal fibroblast neonatal (HDFn) cells. HMF also suppressed the expression of matrix metalloproteinases 1 (MMP-1) and induced the expression of type I procollagen protein in UV-induced HDFn cells. Additionally, HMF inhibited ultraviolet B (UVB)-induced phosphorylation of the mitogen-activated protein kinases (MAPK) cascade signaling components-ERK, JNK, and c-Jun-which are involved in the induction of MMP-1 expression. Furthermore, HMF affected the TGF-β/Smad signaling pathway, which is involved in the regulation of type I procollagen expression. In particular, HMF induced Smad3 protein expression and suppressed Smad7 protein expression in UV-induced HDFn cells in a dose-dependent manner. These findings suggest a role for Citrusunshiu in the preparation of skincare products in future.

Bone Morphogenetic Proteins in Vascular Homeostasis and Disease

It is well established that control of vascular morphogenesis and homeostasis is regulated by vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), Delta-like 4 (Dll4), angiopoietin, and ephrin signaling. It has become clear that signaling by bone morphogenetic proteins (BMPs), which have a long history of studies in bone and early heart development, are also essential for regulating vascular function. Indeed, mutations that cause deregulated BMP signaling are linked to two human vascular diseases, hereditary hemorrhagic telangiectasia and pulmonary arterial hypertension. These observations are corroborated by data obtained with vascular cells in cell culture and in mouse models. BMPs are required for normal endothelial cell differentiation and for venous/arterial and lymphatic specification. In adult life, BMP signaling orchestrates neo-angiogenesis as well as vascular inflammation, remodeling, and calcification responses to shear and oxidative stress. This review emphasizes the pivotal role of BMPs in the vascular system, based on studies of mouse models and human vascular disorders.

ALK1 signaling in development and disease: new paradigms

Activin A receptor like type 1 (ALK1) is a transmembrane serine/threonine receptor kinase in the transforming growth factor-beta receptor family that is expressed on endothelial cells. Defects in ALK1 signaling cause the autosomal dominant vascular disorder, hereditary hemorrhagic telangiectasia (HHT), which is characterized by development of direct connections between arteries and veins, or arteriovenous malformations (AVMs). Although previous studies have implicated ALK1 in various aspects of sprouting angiogenesis, including tip/stalk cell selection, migration, and proliferation, recent work suggests an intriguing role for ALK1 in transducing a flow-based signal that governs directed endothelial cell migration within patent, perfused vessels. In this review, we present an updated view of the mechanism of ALK1 signaling, put forth a unified hypothesis to explain the cellular missteps that lead to AVMs associated with ALK1 deficiency, and discuss emerging roles for ALK1 signaling in diseases beyond HHT.

Thoracic Aortic Aneurysm Development in Patients with Bicuspid Aortic Valve: What Is the Role of Endothelial Cells?

Bicuspid aortic valve (BAV) is the most common type of congenital cardiac malformation. Patients with a BAV have a predisposition for the development of thoracic aortic aneurysm (TAA). This pathological aortic dilation may result in aortic rupture, which is fatal in most cases. The abnormal aortic morphology of TAAs results from a complex series of events that alter the cellular structure and extracellular matrix (ECM) composition of the aortic wall. Because the major degeneration is located in the media of the aorta, most studies aim to unravel impaired smooth muscle cell (SMC) function in BAV TAA. However, recent studies suggest that endothelial cells play a key role in both the initiation and progression of TAAs by influencing the medial layer. Aortic endothelial cells are activated in BAV mediated TAAs and have a substantial influence on ECM composition and SMC phenotype, by secreting several key growth factors and matrix modulating enzymes. In recent years there have been significant advances in the genetic and molecular understanding of endothelial cells in BAV associated TAAs. In this review, the involvement of the endothelial cells in BAV TAA pathogenesis is discussed. Endothelial cell functioning in vessel homeostasis, flow response and signaling will be highlighted to give an overview of the importance and the under investigated potential of endothelial cells in BAV-associated TAA.

Beyond organoids: In vitro vasculogenesis and angiogenesis using cells from mammals and zebrafish

The ability to culture complex organs is currently an important goal in biomedical research. It is possible to grow organoids (3D organ-like structures) in vitro; however, a major limitation of organoids, and other 3D culture systems, is the lack of a vascular network. Protocols developed for establishing in vitro vascular networks typically use human or rodent cells. A major technical challenge is the culture of functional (perfused) networks. In this rapidly advancing field, some microfluidic devices are now getting close to the goal of an artificially perfused vascular network. Another development is the emergence of the zebrafish as a complementary model to mammals. In this review, we discuss the culture of endothelial cells and vascular networks from mammalian cells, and examine the prospects for using zebrafish cells for this objective. We also look into the future and consider how vascular networks in vitro might be successfully perfused using microfluidic technology.

Candidate Gene Resequencing in a Large Bicuspid Aortic Valve-Associated Thoracic Aortic Aneurysm Cohort: SMAD6 as an Important Contributor

Bicuspid aortic valve (BAV) is the most common congenital heart defect. Although many BAV patients remain asymptomatic, at least 20% develop thoracic aortic aneurysm (TAA). Historically, BAV-related TAA was considered as a hemodynamic consequence of the valve defect. Multiple lines of evidence currently suggest that genetic determinants contribute to the pathogenesis of both BAV and TAA in affected individuals. Despite high heritability, only very few genes have been linked to BAV or BAV/TAA, such as NOTCH1, SMAD6, and MAT2A. Moreover, they only explain a minority of patients. Other candidate genes have been suggested based on the presence of BAV in knockout mouse models (e.g., GATA5, NOS3) or in syndromic (e.g., TGFBR1/2, TGFB2/3) or non-syndromic (e.g., ACTA2) TAA forms. We hypothesized that rare genetic variants in these genes may be enriched in patients presenting with both BAV and TAA. We performed targeted resequencing of 22 candidate genes using Haloplex target enrichment in a strictly defined BAV/TAA cohort (n = 441; BAV in addition to an aortic root or ascendens diameter ≥ 4.0 cm in adults, or a Z-score ≥ 3 in children) and in a collection of healthy controls with normal echocardiographic evaluation (n = 183). After additional burden analysis against the Exome Aggregation Consortium database, the strongest candidate susceptibility gene was SMAD6 (p = 0.002), with 2.5% (n = 11) of BAV/TAA patients harboring causal variants, including two nonsense, one in-frame deletion and two frameshift mutations. All six missense mutations were located in the functionally important MH1 and MH2 domains. In conclusion, we report a significant contribution of SMAD6 mutations to the etiology of the BAV/TAA phenotype.

Long Noncoding RNA MANTIS Facilitates Endothelial Angiogenic Function

Supplemental Digital Content is available in the text.

Background:

The angiogenic function of endothelial cells is regulated by numerous mechanisms, but the impact of long noncoding RNAs (lncRNAs) has hardly been studied. We set out to identify novel and functionally important endothelial lncRNAs.

Methods:

Epigenetically controlled lncRNAs in human umbilical vein endothelial cells were searched by exon-array analysis after knockdown of the histone demethylase JARID1B. Molecular mechanisms were investigated by RNA pulldown and immunoprecipitation, mass spectrometry, microarray, several knockdown approaches, CRISPR-Cas9, assay for transposase-accessible chromatin sequencing, and chromatin immunoprecipitation in human umbilical vein endothelial cells. Patient samples from lung and tumors were studied for MANTIS expression.

Results:

A search for epigenetically controlled endothelial lncRNAs yielded lncRNA n342419, here termed MANTIS, as the most strongly regulated lncRNA. Controlled by the histone demethylase JARID1B, MANTIS was downregulated in patients with idiopathic pulmonary arterial hypertension and in rats treated with monocrotaline, whereas it was upregulated in carotid arteries of Macaca fascicularis subjected to atherosclerosis regression diet, and in endothelial cells isolated from human glioblastoma patients. CRISPR/Cas9-mediated deletion or silencing of MANTIS with small interfering RNAs or GapmeRs inhibited angiogenic sprouting and alignment of endothelial cells in response to shear stress. Mechanistically, the nuclear-localized MANTIS lncRNA interacted with BRG1, the catalytic subunit of the switch/sucrose nonfermentable chromatin-remodeling complex. This interaction was required for nucleosome remodeling by keeping the ATPase function of BRG1 active. Thereby, the transcription of key endothelial genes such as SOX18, SMAD6, and COUP-TFII was regulated by ensuring efficient RNA polymerase II machinery binding.

Conclusion:

MANTIS is a differentially regulated novel lncRNA facilitating endothelial angiogenic function.

Regulation of TGF-β Family Signaling by Inhibitory Smads

Inhibitory Smads (I-Smads) have conserved carboxy-terminal MH2 domains but highly divergent amino-terminal regions when compared with receptor-regulated Smads (R-Smads) and common-partner Smads (co-Smads). Smad6 preferentially inhibits Smad signaling initiated by the bone morphogenetic protein (BMP) type I receptors ALK-3 and ALK-6, whereas Smad7 inhibits both transforming growth factor β (TGF-β)- and BMP-induced Smad signaling. I-Smads also regulate some non-Smad signaling pathways. Here, we discuss the vertebrate I-Smads, their roles as inhibitors of Smad activation and regulators of receptor stability, as scaffolds for non-Smad signaling, and their possible roles in the nucleus. We also discuss the posttranslational modification of I-Smads, including phosphorylation, ubiquitylation, acetylation, and methylation.

Regulation of TGF-β Family Signaling by Inhibitory Smads

Inhibitory Smads (I-Smads) have conserved carboxy-terminal MH2 domains but highly divergent amino-terminal regions when compared with receptor-regulated Smads (R-Smads) and common-partner Smads (co-Smads). Smad6 preferentially inhibits Smad signaling initiated by the bone morphogenetic protein (BMP) type I receptors ALK-3 and ALK-6, whereas Smad7 inhibits both transforming growth factor β (TGF-β)- and BMP-induced Smad signaling. I-Smads also regulate some non-Smad signaling pathways. Here, we discuss the vertebrate I-Smads, their roles as inhibitors of Smad activation and regulators of receptor stability, as scaffolds for non-Smad signaling, and their possible roles in the nucleus. We also discuss the posttranslational modification of I-Smads, including phosphorylation, ubiquitylation, acetylation, and methylation.

Dynamically Tunable Cell Culture Platforms for Tissue Engineering and Mechanobiology

Human tissues are sophisticated ensembles of many distinct cell types embedded in the complex, but well-defined, structures of the extracellular matrix (ECM). Dynamic biochemical, physicochemical, and mechano-structural changes in the ECM define and regulate tissue-specific cell behaviors. To recapitulate this complex environment in vitro, dynamic polymer-based biomaterials have emerged as powerful tools to probe and direct active changes in cell function. The rapid evolution of polymerization chemistries, structural modulation, and processing technologies, as well as the incorporation of stimuli-responsiveness, now permit synthetic microenvironments to capture much of the dynamic complexity of native tissue. These platforms are comprised not only of natural polymers chemically and molecularly similar to ECM, but those fully synthetic in origin. Here, we review recent in vitro efforts to mimic the dynamic microenvironment comprising native tissue ECM from the viewpoint of material design. We also discuss how these dynamic polymer-based biomaterials are being used in fundamental cell mechanobiology studies, as well as towards efforts in tissue engineering and regenerative medicine.

Cardiac Safety of TGF-β Receptor I Kinase Inhibitor LY2157299 Monohydrate in Cancer Patients in a First-in-Human Dose Study

Transforming growth factor-beta (TGF-β) signaling plays an important role in the fetal development of cardiovascular organs and in the repair mechanisms of the heart. Hence, inhibitors of the TGF-β signaling pathway require a careful identification of a safe therapeutic window and a comprehensive monitoring of the cardiovascular system. Seventy-nine cancer patients (67 glioma and 12 solid tumor) enrolled in a first-in-human dose study and received the TGF-β inhibitor LY2157299 monohydrate (LY2157299) as monotherapy (n = 53) or in combination with lomustine (n = 26). All patients were monitored using 2D echocardiography/color and Spectral Doppler (2D Echo with Doppler) every 2 months, monthly electrocardiograms, thorax computer tomography scans every 6 months, and monthly serum brain natriuretic peptide (BNP), troponin I, cystatin C, high-sensitivity C-reactive protein (hs-CRP). Administration of LY2157299 was not associated with medically relevant cardiovascular toxicities, including patients treated ≥6 months (n = 13). There were no increases of troponin I, BNP, or hs-CRP or reduction in cystatin C levels, which may have been considered as signs of cardiovascular injury. Blood pressure was generally stable during treatment. Imaging with echocardiography/Doppler showed an increase in mitral and tricuspid valve regurgitation by two grades of severity in only one patient with no concurrent clinical symptoms of cardiovascular injury. Overall, this comprehensive cardiovascular monitoring for the TGF-β inhibitor LY2157299 did not detect medically relevant cardiac toxicity and hence supports the evaluation of LY2157299 in future clinical trials.

Global analysis of DNA methylation in hepatocellular carcinoma by a liquid hybridization capture-based bisulfite sequencing approach

BACKGROUND

Epigenetic alterations, such as aberrant DNA methylation of promoter and enhancer regions, which lead to atypical gene expression, have been associated with carcinogenesis. In hepatocellular carcinoma (HCC), genome-wide analysis of methylation has only recently been used. For a better understanding of hepatocarcinogenesis, we applied an even higher resolution analysis of the promoter methylome to identify previously unknown regions and genes differentially methylated in HCC.

RESULTS

Optimized liquid hybridization capture-based bisulfite sequencing (LHC-BS) was developed to quantitatively analyze 1.86 million CpG sites in individual samples from eight pairs of HCC and adjacent tissues. By linking the differentially methylated regions (DMRs) in promoters to the differentially expressed genes (DEGs), we identified 12 DMR-associated genes. We further utilized Illumina MiSeq combining the bisulfite sequencing PCR approach to validate the 12 candidate genes. Analysis of an additional 78 HCC pairs on the Illumina MiSeq platform confirmed that 7 genes showed either promoter hyper-methylation (SMAD6, IFITM1, LRRC4, CHST4, and TBX15) or hypo-methylation (CCL20 and NQO1) in HCC.

CONCLUSIONS

Novel methylome profiling provides a cost-efficient approach to identifying candidate genes in human HCC that may contribute to hepatocarcinogenesis. Our work provides further information critical for understanding the epigenetic processes underlying tumorigenesis and development of HCC.

Regulators and effectors of bone morphogenetic protein signalling in the cardiovascular system

Bone morphogenetic proteins (BMPs) play key roles in the regulation of cell proliferation, differentiation and apoptosis in various tissues and organs, including the cardiovascular system. BMPs signal through both Smad-dependent and -independent cascades to exert a wide spectrum of biological activities. Cardiovascular disorders such as abnormal angiogenesis, atherosclerosis, pulmonary hypertension and cardiac hypertrophy have been linked to aberrant BMP signalling. To correct the dysregulated BMP signalling in cardiovascular pathogenesis, it is essential to get a better understanding of how the regulators and effectors of BMP signalling control cardiovascular function and how the dysregulated BMP signalling contributes to cardiovascular dysfunction. We hence highlight several key regulators of BMP signalling such as extracellular regulators of ligands, mechanical forces, microRNAs and small molecule drugs as well as typical BMP effectors like direct downstream target genes, mitogen-activated protein kinases, reactive oxygen species and microRNAs. The insights into these molecular processes will help target both the regulators and important effectors to reverse BMP-associated cardiovascular pathogenesis.

SMAD7: a timer of tumor progression targeting TGF-β signaling

In the context of cancer, transforming growth factor β (TGF-β) is a cell growth suppressor; however, it is also a critical inducer of invasion and metastasis. SMAD is the important mediator of TGF-β signaling pathway, which includes receptor-regulated SMADs (R-SMADs), common-mediator SMADs (co-SMADs), and inhibitory SMADs (I-SMADs). I-SMADs block the activation of R-SMADs and co-SMADs and thus play important roles especially in the SMAD-dependent signaling. SMAD7 belongs to the I-SMADs. As an inhibitor of TGF-β signaling, SMAD7 is overexpressed in numerous cancer types and its abundance is positively correlated to the malignancy. Emerging evidence has revealed the switch-in-role of SMAD7 in cancer, from a TGF-β inhibiting protein at the early stages that facilitates proliferation to an enhancer of invasion at the late stages. This role change may be accompanied or elicited by the tumor microenvironment and/or somatic mutation. Hence, current knowledge suggests a tumor-favorable timer nature of SMAD7 in cancer progression. In this review, we summarized the advances and recent findings of SMAD7 and TGF-β signaling in cancer, followed by specific discussion on the possible factors that account for the functional changes of SMAD7.

Circulating Bmp10 acts through endothelial Alk1 to mediate flow-dependent arterial quiescence

Blood flow plays crucial roles in vascular development, remodeling and homeostasis, but the molecular pathways required for transducing flow signals are not well understood. In zebrafish embryos, arterial expression of activin receptor-like kinase 1 (alk1), which encodes a TGFβ family type I receptor, is dependent on blood flow, and loss of alk1 mimics lack of blood flow in terms of dysregulation of a subset of flow-responsive arterial genes and increased arterial endothelial cell number. These data suggest that blood flow activates Alk1 signaling to promote a flow-responsive gene expression program that limits nascent arterial caliber. Here, we demonstrate that restoration of endothelial alk1 expression to flow-deprived arteries fails to rescue Alk1 activity or normalize arterial endothelial cell gene expression or number, implying that blood flow may play an additional role in Alk1 signaling independent of alk1 induction. To this end, we define cardiac-derived Bmp10 as the crucial ligand for endothelial Alk1 in embryonic vascular development, and provide evidence that circulating Bmp10 acts through endothelial Alk1 to limit endothelial cell number in and thereby stabilize the caliber of nascent arteries. Thus, blood flow promotes Alk1 activity by concomitantly inducing alk1 expression and distributing Bmp10, thereby reinforcing this signaling pathway, which functions to limit arterial caliber at the onset of flow. Because mutations in ALK1 cause arteriovenous malformations (AVMs), our findings suggest that an impaired flow response initiates AVM development.

Induction of olfaction and cancer-related genes in mice fed a high-fat diet as assessed through the mode-of-action by network identification analysis

The pathophysiological mechanisms underlying the development of obesity and metabolic diseases are not well understood. To gain more insight into the genetic mediators associated with the onset and progression of diet-induced obesity and metabolic diseases, we studied the molecular changes in response to a high-fat diet (HFD) by using a mode-of-action by network identification (MNI) analysis. Oligo DNA microarray analysis was performed on visceral and subcutaneous adipose tissues and muscles of male C57BL/6N mice fed a normal diet or HFD for 2, 4, 8, and 12 weeks. Each of these data was queried against the MNI algorithm, and the lists of top 5 highly ranked genes and gene ontology (GO)-annotated pathways that were significantly overrepresented among the 100 highest ranked genes at each time point in the 3 different tissues of mice fed the HFD were considered in the present study. The 40 highest ranked genes identified by MNI analysis at each time point in the different tissues of mice with diet-induced obesity were subjected to clustering based on their temporal patterns. On the basis of the above-mentioned results, we investigated the sequential induction of distinct olfactory receptors and the stimulation of cancer-related genes during the development of obesity in both adipose tissues and muscles. The top 5 genes recognized using the MNI analysis at each time point and gene cluster identified based on their temporal patterns in the peripheral tissues of mice provided novel and often surprising insights into the potential genetic mediators for obesity progression.

Expression of caveolin-1 in the early phase of beta-TCP implanted in dog mandible

Caveolin is an essential and signature protein of caveolae. Caveolin-1 participates in signal transduction processes by acting as a scaffolding protein that concentrates, organizes and functional regulates signalling molecules within caveolar membranes. Beta-tricalcium phosphate (β-TCP) has been widely used for scaffold in tissue engineering due to its high biodegradability, osteoconductivity, easy manipulation, and lack of histotoxicity. To better understand the role of caveolin-1 in bone homeostasis and response to β-TCP scaffold, β-TCP was implanted into the dog mandible defects in beagle dogs, and gene expression profiles were examined focused on the molecular components involved in caveolin-1 regulation. Here we showed the quantitative imageology analysis characterized using in vivo micro-computed tomography (CT) images at 4 and 7 days after β-TCP implanted in dog mandibles. The bone reformation by using the β-TCP scaffolds began within 4 days of surgery, and was healing well at 7 days after surgery. Higher mRNA level of caveolin-1 was observed in β-TCP-implanted Beagle dog mandibles compared with controls at day 4 and day 7 post-surgery. The enhancement of caveolin-1 by β-TCP was further confirmed by immunohistochemistry and immunofluorescence analysis. We further revealed increased Smad7 and Phospho Stat3 expression in β-TCP-implanted specimens. Taken together, these results suggest that the enhancement of caveolin-1 play an important role in accelerating bone formation by β-TCP.

Nonsynonymous variants in the SMAD6 gene predispose to congenital cardiovascular malformation

Congenital cardiovascular malformation (CVM) exhibits familial predisposition, but most of the specific genetic factors involved are unknown. Postulating that rare variants in genes in critical cardiac developmental pathways predispose to CVM, we systematically surveyed three genes of the bone morphogenetic protein (BMP) signaling pathway for novel variants. Exonic, splice site, and untranslated regions of BMPR1A, BMPR2, and SMAD6 genes were sequenced in 90 unrelated sporadic cases of CVM. One nonsynonymous variant (p.C484F) with predicted functional impact was found in the MAD homology 2 domain of SMAD6, an intracellular inhibitor of BMP signaling. Sequencing this domain in an additional 346 cases of CVM yielded two further nonsynonymous variants (p.P415L and p.A325T). Functional effects of all three SMAD6 mutations were investigated using BMP signaling assays in vitro. Two SMAD6 variants (p.C484F and p.P415L) had significantly (P < 0.05) lower activity than wild-type SMAD6 in inhibiting BMP signaling in a transcriptional reporter assay. In addition, the p.C484F variant had a significantly (P < 0.05) lower capacity to inhibit an osteogenic response to BMP signaling. We conclude that low-frequency deleterious variants in SMAD6 predispose to CVM. This is the first report of a human disease phenotype related to genetic variation in SMAD6. Hum Mutat 33:720–727, 2012. © 2012 Wiley Periodicals, Inc.

Nuclear Smad7 Overexpressed in Mesenchymal Cells Acts as a Transcriptional Corepressor by Interacting with HDAC-1 and E2F to Regulate Cell Cycle

Smad family proteins are essential intracellular mediators that regulate transforming growth factor-β (TGF-β) ligand signaling. In response to diverse stimuli, Smad7 is rapidly expressed and acts as a cytoplasmic inhibitor that selectively interferes with signals elicited from TGF-β family receptors. In addition, earlier works have indicated that retrovirally transduced Smad7 induces long-lasting cell proliferation arrest in a variety of mesenchymal cells through down-regulation of G1 cyclins. However, the molecular mechanisms underlying the cytostatic effects of Smad7 remain unknown. We show here that Smad7 can form a complex with endogenous histone deacetylase proteins HDAC-1 and HDAC-3 in NIH 3T3 mouse fibroblast cells. By contrast, forced expression of a dominant-negative variant of HDAC-1 efficiently protected cells against Smad7 proliferation inhibition, suggesting that Smad7 depends on the deacetylase activity of its associated HDAC-1 to arrest the cell cycle. Furthermore, Smad7 caused HDAC-1 bind to E2F-1 to form a ternary complex on chromosomal DNA containing an E2F-binding motif and leading to repression in the activity of the E2F target genes. Smad7 mutations that prevented its binding to either HDAC-1 or E2F-1 resulted in a significant decrease in Smad7-mediated inhibition of cell proliferation. The present results strongly suggest that nuclear Smad7 is a transcriptional corepressor for E2F, providing a molecular basis for the Smad7-induced arrest of the cell cycle.

Bone Morphogenetic Protein functions as a context-dependent angiogenic cue in vertebrates

Bone Morphogenetic Protein (BMP) signaling has been implicated in diverse biological processes. Although how BMP signaling regulates behaviors of endothelial cells during angiogenesis are not fully understood, increasing evidence indicate functions of BMP signaling components are essential in developmental and pathological angiogenesis. Here we review recent advances in delineating the functions of BMP signaling during angiogenesis. In addition, we discuss downstream pathways that transduce BMP signaling in endothelial cells, and factors that modulate BMP signaling response in endothelial cells. Finally, we provide recent insight on how BMP signaling functions as a context dependent angiogenic cue.

Uniaxial mechanical strain modulates the differentiation of neural crest stem cells into smooth muscle lineage on micropatterned surfaces

Neural crest stem cells (NCSCs) play an important role in the development and represent a valuable cell source for tissue engineering. However, how mechanical factors in vivo regulate NCSC differentiation is not understood. Here NCSCs were derived from induced pluripotent stem cells and used as a model to determine whether vascular mechanical strain modulates the differentiation of NCSCs into smooth muscle (SM) lineage. NCSCs were cultured on micropatterned membranes to mimic the organization of smooth muscle cells (SMCs), and subjected to cyclic uniaxial strain. Mechanical strain enhanced NCSC proliferation and ERK2 phosphorylation. In addition, mechanical strain induced contractile marker calponin-1 within 2 days and slightly induced SM myosin within 5 days. On the other hand, mechanical strain suppressed the differentiation of NCSCs into Schwann cells. The induction of calponin-1 by mechanical strain was inhibited by neural induction medium but further enhanced by TGF-β. For NCSCs pre-treated with TGF-β, mechanical strain induced the gene expression of both calponin-1 and SM myosin. Our results demonstrated that mechanical strain regulates the differentiation of NCSCs in a manner dependent on biochemical factors and the differentiation stage of NCSCs. Understanding the mechanical regulation of NCSC differentiation will shed light on the development and remodeling of vascular tissues, and how transplanted NCSCs respond to mechanical factors.

Preferential activation of SMAD1/5/8 on the fibrosa endothelium in calcified human aortic valves--association with low BMP antagonists and SMAD6

Background

Aortic valve (AV) calcification preferentially occurs on the fibrosa side while the ventricularis side remains relatively unaffected. Here, we tested the hypothesis that side-dependent activation of bone morphogenic protein (BMP) pathway in the endothelium of the ventricularis and fibrosa is associated with human AV calcification.

Methods and Results

Human calcified AVs obtained from AV replacement surgeries and non-calcified AVs from heart transplantations were used for immunohistochemical studies. We found SMAD-1/5/8 phosphorylation (a canonical BMP pathway) was higher in the calcified fibrosa than the non-calcified fibrosa while SMAD-2/3 phosphorylation (a canonical TGFβ pathway) did not show any difference. Interestingly, we found that BMP-2/4/6 expression was significantly higher on the ventricularis endothelium compared to the fibrosa in both calcified and non-calcified AV cusps; however, BMP antagonists (crossvienless-2/BMPER and noggin) expression was significantly higher on the ventricularis endothelium compared to the fibrosa in both disease states. Moreover, significant expression of inhibitory SMAD-6 expression was found only in the non-calcified ventricularis endothelium.

Conclusions

SMAD-1/5/8 is preferentially activated in the calcified fibrosa endothelium of human AVs and it correlates with low expression of BMP antagonists and inhibitory SMAD6. These results suggest a dominant role of BMP antagonists in the side-dependent calcification of human AVs.

Haplotype association mapping of acute lung injury in mice implicates activin a receptor, type 1

RATIONALE

Because acute lung injury is a sporadic disease produced by heterogeneous precipitating factors, previous genetic analyses are mainly limited to candidate gene case-control studies.

OBJECTIVES

To develop a genome-wide strategy in which single nucleotide polymorphism associations are assessed for functional consequences to survival during acute lung injury in mice.

METHODS

To identify genes associated with acute lung injury, 40 inbred strains were exposed to acrolein and haplotype association mapping, microarray, and DNA-protein binding were assessed.

MEASUREMENTS AND MAIN RESULTS

The mean survival time varied among mouse strains with polar strains differing approximately 2.5-fold. Associations were identified on chromosomes 1, 2, 4, 11, and 12. Seven genes (Acvr1, Cacnb4, Ccdc148, Galnt13, Rfwd2, Rpap2, and Tgfbr3) had single nucleotide polymorphism (SNP) associations within the gene. Because SNP associations may encompass "blocks" of associated variants, functional assessment was performed in 91 genes within ± 1 Mbp of each SNP association. Using 10% or greater allelic frequency and 10% or greater phenotype explained as threshold criteria, 16 genes were assessed by microarray and reverse real-time polymerase chain reaction. Microarray revealed several enriched pathways including transforming growth factor-β signaling. Transcripts for Acvr1, Arhgap15, Cacybp, Rfwd2, and Tgfbr3 differed between the strains with exposure and contained SNPs that could eliminate putative transcriptional factor recognition sites. Ccdc148, Fancl, and Tnn had sequence differences that could produce an amino acid substitution. Mycn and Mgat4a had a promoter SNP or 3'untranslated region SNPs, respectively. Several genes were related and encoded receptors (ACVR1, TGFBR3), transcription factors (MYCN, possibly CCDC148), and ubiquitin-proteasome (RFWD2, FANCL, CACYBP) proteins that can modulate cell signaling. An Acvr1 SNP eliminated a putative ELK1 binding site and diminished DNA-protein binding.

CONCLUSIONS

Assessment of genetic associations can be strengthened using a genetic/genomic approach. This approach identified several candidate genes, including Acvr1, associated with increased susceptibility to acute lung injury in mice.

Tgfβ/Alk5 signaling is required for shear stress induced klf2 expression in embryonic endothelial cells

Endothelial cells (EC) translate biomechanical forces into functional and phenotypic responses that play important roles in cardiac development. Specifically, EC in areas of high shear stress, i.e., in the cardiac outflow tract and atrioventricular canal, are characterized by high expression of Krüppel-like factor 2 (Klf2) and by transforming growth factor-beta (Tgfβ)-driven endothelial-to-mesenchymal transition. Extraembryonic venous obstruction (venous clip model) results in congenital heart malformations, and venous clip-induced alterations in shear stress-related gene expression are suggestive for an increase in cardiac shear stress. Here, we study the effects of shear stress on Klf2 expression and Tgfβ-associated signaling in embryonic EC in vivo using the venous clip model and in vitro by subjecting cultured EC to fluid flow. Cellular responses were assessed by analysis of Klf2, Tgfβ ligands, and their downstream signaling targets. Results show that, in embryonic EC, shear stress activates Tgfβ/Alk5 signaling and that induction of Klf2 is an Alk5 dependent process.

Flow-dependent Smad2 phosphorylation and TGIF nuclear localization in human aortic endothelial cells

Endothelial cells respond to fluid flow stimulation through transient and sustained signal pathway activation. Smad2 is a signaling molecule and transcription factor in the Smad signaling pathway, traditionally associated with TGF-β. Although phosphorylation of Smad2 in the receptor-dependent COOH-terminal region is the most appreciated way Smad2 is activated to affect gene expression, phosphorylation may also occur in the MH1-MH2 linker region (L-psmad2). Here, we show that in human aortic endothelial cells (HAEC), Smad2 was both preferentially phosphorylated in the linker region and localized to the nucleus in a flow-dependent manner. The Smad corepressor transforming growth interacting factor (TGIF) was also found to have flow-dependent nuclear localization. Tissue studies confirmed this L-psmad2 generation trend in rat aorta, indicating likely importance in arterial tissue. HAEC-based inhibitor studies demonstrated that L-psmad2 levels were not related to MAPK phosphorylation, but instead followed the pattern of pAkt(473), both with and without the phosphatidylinositol 3-kinase inhibitor PI-103. Akt and Smad species were also shown to directly interact under flow relative to static controls. To further evaluate impacts of PI-103 treatment, expression profiles for two TGF-β and shear stress-dependent genes were determined and showed that mRNAs were lower from untreated 10 dyn/cm(2) than 2 dyn/cm(2) average shear stress cultures. However, upon exposure to PI-103, this trend was reversed, with a stronger response observed at 10 dyn/cm(2). Taken together, the results of this work suggest that fluid flow exposure may influence endothelial gene expression by a novel mechanism involving Akt, L-psmad2, and TGIF.

A meta-analysis of microarray-based gene expression studies of olfactory bulb-derived olfactory ensheathing cells

Genome wide transcriptional profiling and large scale proteomics have emerged as two powerful methods to dissect the molecular properties of specific neural tissues or cell types on a global scale. Several genome-wide transcriptional profiling and proteomics studies have been published on cultured olfactory ensheathing cells (OEC). In this article we present a meta-analysis of all five published and publicly available micro-array gene expression datasets of cultured early-passage-OB-OEC with other cell types (Schwann cells, late-passage-OB-OEC, mucosa-OEC, an OEC cell line, and acutely dissected OEC). The aim of this meta-analysis is to identify genes and molecular pathways that are found in multiple instead of one isolated study. 454 Genes were detected in at least three out of five microarray datasets. In this "Top-list", genes involved in the biological processes "growth of neurites", "blood vessel development", "migration of cells" and "immune response" were strongly overrepresented. By applying network analysis tools, molecular networks were constructed and Hub-genes were identified that may function as key genes in the above mentioned interrelated processes. We also identified 7 genes (ENTPD2, MATN2, CTSC, PTHLH, GLRX1, COL27A1 and ID2) with uniformly higher or lower expression in early-passage-OB-OEC in all five microarray comparisons. These genes have diverse but intriguing roles in neuroprotection, neurite extension and/or tissue repair. Our meta-analysis provides novel insights into the molecular basis of OB-OEC-mediated neural repair and can serve as a repository for investigators interested in the molecular biology of OEC. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

IL1B induced Smad 7 negatively regulates gastrin expression

Background

Helicobacter pylori elicited IL1B is one of the various modulators responsible for perturbation of acid secretion in gut. We have earlier reported that IL1B activated NFkB downregulates gastrin, a major modulator of acid secretion. However, we hypothesized that regulation of gastrin by IL1B would depend on the cell's ability to integrate inputs from multiple signaling pathways to generate appropriate biological response.

Principal Finding

In this study, we report that IL1B induces Smad 7 expression by about 4.5 fold in gastric carcinoma cell line, AGS. Smad 7 resulted in transcriptional repression of gastrin promoter by about 6.5 fold when co -transfected with Smad 7 expression vector and gastrin-promoter luciferase in AGS cells. IL1B inhibited phosphorylation of Smad 3 and subsequently interfered with nuclear translocation of the positive Smad complex, thus occluding it off the gastrin promoter. IL1B promoter polymorphisms (-511T/-31C IL1B) are known to be associated with H. pylori associated gastro-duodenal ulcer. We observed that IL1B expressed from -31T promoter driven IL1B cDNA elicited 3.5 fold more Smad 7 than that expressed from the IL1B-31C variant in AGS cells. This differential activation of Smad 7 by IL1B promoter variants translated into differential downregulation of gastrin expression. We further analyzed Smad 7, NFkB, IL1B and gastrin expression in antral gut biopsy samples of patients with H. pylori associated duodenal ulcer and normal individuals. We observed that individuals with duodenal ulcer had significantly lower levels of IL1B, Smad 7, NFkB and corresponding higher level of gastrin expression.

Conclusion

Pro-inflammatory cytokine IL1B repress gastrin expression by activating Smad 7 and subsequent inhibition of nuclear localization of Smad 3/4 complex. Polymorphic promoter variants of IL1B gene can modulate the IL1B expression which resulted in differential activation Smad 7 and consequent repression of gastrin expression, respectively. Analysis of H. pylori infected duodenal ulcer patient's gut biopsy samples also supported this observation.