Smad7 is required for the development and function of the heart

The chromatin regulator Ankrd11 controls cardiac neural crest cell-mediated outflow tract remodeling and heart function

ANKRD11 (Ankyrin Repeat Domain 11) is a chromatin regulator and a causative gene for KBG syndrome, a rare developmental disorder characterized by multiple organ abnormalities, including cardiac defects. However, the role of ANKRD11 in heart development is unknown. The neural crest plays a leading role in embryonic heart development, and its dysfunction is implicated in congenital heart defects. We demonstrate that conditional knockout of Ankrd11 in the murine embryonic neural crest results in persistent truncus arteriosus, ventricular dilation, and impaired ventricular contractility. We further show these defects occur due to aberrant cardiac neural crest cell organization leading to outflow tract septation failure. Lastly, knockout of Ankrd11 in the neural crest leads to impaired expression of various transcription factors, chromatin remodelers and signaling pathways, including mTOR, BMP and TGF-β in the cardiac neural crest cells. In this work, we identify Ankrd11 as a regulator of neural crest-mediated heart development and function.

Chrysin-based supramolecular cyclodextrin-calixarene drug delivery system: a novel approach for attenuating cardiac fibrosis in chronic diabetes

Introduction: Cardiac fibrosis is strongly induced by diabetic conditions. Both chrysin (CHR) and calixarene OTX008, a specific inhibitor of galectin 1 (Gal-1), seem able to reduce transforming growth factor beta (TGF-β)/SMAD pro-fibrotic pathways, but their use is limited to their low solubility. Therefore, we formulated a dual-action supramolecular system, combining CHR with sulfobutylated β-cyclodextrin (SBECD) and OTX008 (SBECD + OTX + CHR). Here we aimed to test the anti-fibrotic effects of SBECD + OTX + CHR in hyperglycemic H9c2 cardiomyocytes and in a mouse model of chronic diabetes. Methods: H9c2 cardiomyocytes were exposed to normal (NG, 5.5 mM) or high glucose (HG, 33 mM) for 48 h, then treated with SBECD + OTX + CHR (containing OTX008 0.75-1.25-2.5 µM) or the single compounds for 6 days. TGF-β/SMAD pathways, Mitogen-Activated Protein Kinases (MAPKs) and Gal-1 levels were assayed by Enzyme-Linked Immunosorbent Assays (ELISAs) or Real-Time Quantitative Reverse Transcription Polymerase chain reaction (qRT-PCR). Adult CD1 male mice received a single intraperitoneal (i.p.) administration of streptozotocin (STZ) at a dosage of 102 mg/kg body weight. From the second week of diabetes, mice received 2 times/week the following i.p. treatments: OTX (5 mg/kg)-SBECD; OTX (5 mg/kg)-SBECD-CHR, SBECD-CHR, SBECD. After a 22-week period of diabetes, mice were euthanized and cardiac tissue used for tissue staining, ELISA, qRT-PCR aimed to analyse TGF-β/SMAD, extracellular matrix (ECM) components and Gal-1. Results: In H9c2 cells exposed to HG, SBECD + OTX + CHR significantly ameliorated the damaged morphology and reduced TGF-β1, its receptors (TGFβR1 and TGFβR2), SMAD2/4, MAPKs and Gal-1. Accordingly, these markers were reduced also in cardiac tissue from chronic diabetes, in which an amelioration of cardiac remodeling and ECM was evident. In both settings, SBECD + OTX + CHR was the most effective treatment compared to the other ones. Conclusion: The CHR-based supramolecular SBECD-calixarene drug delivery system, by enhancing the solubility and the bioavailability of both CHR and calixarene OTX008, and by combining their effects, showed a strong anti-fibrotic activity in rat cardiomyocytes and in cardiac tissue from mice with chronic diabetes. Also an improved cardiac tissue remodeling was evident. Therefore, new drug delivery system, which could be considered as a novel putative therapeutic strategy for the treatment of diabetes-induced cardiac fibrosis.

Polycomb Group Protein CBX7 Represses Cardiomyocyte Proliferation Through Modulation of the TARDBP/RBM38 Axis

BACKGROUND

Shortly after birth, cardiomyocytes exit the cell cycle and cease proliferation. At present, the regulatory mechanisms for this loss of proliferative capacity are poorly understood. CBX7 (chromobox 7), a polycomb group (PcG) protein, regulates the cell cycle, but its role in cardiomyocyte proliferation is unknown.

METHODS

We profiled CBX7 expression in the mouse hearts through quantitative real-time polymerase chain reaction, Western blotting, and immunohistochemistry. We overexpressed CBX7 in neonatal mouse cardiomyocytes through adenoviral transduction. We knocked down CBX7 by using constitutive and inducible conditional knockout mice (Tnnt2-Cre;Cbx7fl/+ and Myh6-MCM;Cbx7fl/fl, respectively). We measured cardiomyocyte proliferation by immunostaining of proliferation markers such as Ki67, phospho-histone 3, and cyclin B1. To examine the role of CBX7 in cardiac regeneration, we used neonatal cardiac apical resection and adult myocardial infarction models. We examined the mechanism of CBX7-mediated repression of cardiomyocyte proliferation through coimmunoprecipitation, mass spectrometry, and other molecular techniques.

RESULTS

We explored Cbx7 expression in the heart and found that mRNA expression abruptly increased after birth and was sustained throughout adulthood. Overexpression of CBX7 through adenoviral transduction reduced proliferation of neonatal cardiomyocytes and promoted their multinucleation. On the other hand, genetic inactivation of Cbx7 increased proliferation of cardiomyocytes and impeded cardiac maturation during postnatal heart growth. Genetic ablation of Cbx7 promoted regeneration of neonatal and adult injured hearts. Mechanistically, CBX7 interacted with TARDBP (TAR DNA-binding protein 43) and positively regulated its downstream target, RBM38 (RNA Binding Motif Protein 38), in a TARDBP-dependent manner. Overexpression of RBM38 inhibited the proliferation of CBX7-depleted neonatal cardiomyocytes.

CONCLUSIONS

Our results demonstrate that CBX7 directs the cell cycle exit of cardiomyocytes during the postnatal period by regulating its downstream targets TARDBP and RBM38. This is the first study to demonstrate the role of CBX7 in regulation of cardiomyocyte proliferation, and CBX7 could be an important target for cardiac regeneration.

MicroRNA-30e-3p reduces coronary microembolism-induced cardiomyocyte pyroptosis and inflammation by sequestering HDAC2 from the SMAD7 promoter

This study investigates the mechanism by which microRNA (miR)-30e-3p reduces coronary microembolism (CME)-induced cardiomyocyte pyroptosis and inflammation. Cardiac function tests, histological staining, and transmission electron microscopy were performed on CME-model rats injected with adeno-associated viral vectors. Cardiomyocytes were transfected 24 h before a cellular model of pyroptosis was established via treatment with 1 μg/mL lipopolysaccharide (LPS) for 4 h and 5 mM ATP for 30 min. Pyroptosis, inflammation, and Wnt/β-catenin signaling in cardiomyocytes were detected. Dual-luciferase reporter assays and/or RNA pull-down assays were performed to verify the binding of miR-30e-3p to HDAC2 mRNA or HDAC2 to the SMAD7 promoter. Chromatin immunoprecipitation was used to assess the level of H3K27 acetylation at the SMAD7 promoter. miR-30e-3p and SMAD7 expression levels were downregulated and HDAC2 expression was upregulated with CME. The overexpression of miR-30e-3p restored cardiac functions in CME-model rats and reduced serum cTnI, IL-18, and IL-1β levels, microinfarcts, inflammatory cell infiltration, apoptosis, collagen content, and GSDMD-N, cleaved caspase-1, and NLRP3 expression in the myocardium, but these effects were reversed by SMAD7 knockdown. The overexpression of miR-30e-3p or knockdown of HDAC2 reduced LDH, IL-18, and IL-1β secretion, propidium iodide intake, and GSDMD-N, NLRP3, cleaved caspase-1, Wnt3a, Wnt5a, and β-catenin expression in the cardiomyocyte model. miR-30e-3p inhibited the expression of HDAC2 by binding HDAC2 mRNA. HDAC2 repressed the expression of SMAD7 by catalyzing H3K27 deacetylation at the SMAD7 promoter. miR-30e-3p, by binding HDAC2 to promote SMAD7 expression, reduces CME-induced cardiomyocyte pyroptosis and inflammation.

Circulating microRNA: Myocardium-derived prenatal biomarker of ventricular septal defects

Background: Recently, circulating microRNAs (miRNAs) from maternal blood and amniotic fluid have been used as biomarkers for ventricular septal defect (VSD) diagnosis. However, whether circulating miRNAs are associated with fetal myocardium remains unknown.

Methods: Dimethadione (DMO) induced a VSD rat model. The miRNA expression profiles of the myocardium, amniotic fluid and maternal serum were analyzed. Differentially expressed microRNAs (DE-microRNAs) were verified by qRT–PCR. The target gene of miR-1-3p was confirmed by dual luciferase reporter assays. Expression of amniotic fluid-derived DE-microRNAs was verified in clinical samples.

Results: MiRNAs were differentially expressed in VSD fetal rats and might be involved in cardiomyocyte differentiation and apoptosis. MiR-1-3p, miR-1b and miR-293-5p were downregulated in the myocardium and upregulated in amniotic fluid/maternal serum. The expression of amniotic fluid-derived DE-microRNAs (miR-1-3p, miR-206 and miR-184) was verified in clinical samples. Dual luciferase reporter assays confirmed that miR-1-3p directly targeted SLC8A1/NCX1.

Conclusion: MiR-1-3p, miR-1b and miR-293-5p are downregulated in VSD myocardium and upregulated in circulation and may be released into circulation by cardiomyocytes. MiR-1-3p targets SLC8A1/NCX1 and participates in myocardial apoptosis. MiR-1-3p upregulation in circulation is a direct and powerful indicator of fetal VSD and is expected to serve as a prenatal VSD diagnostic marker.

Association of TGF-β Canonical Signaling-Related Core Genes With Aortic Aneurysms and Aortic Dissections

Transforming growth factor-beta (TGF-β) signaling is essential for the maintenance of the normal structure and function of the aorta. It includes SMAD-dependent canonical pathways and noncanonical signaling pathways. Accumulated genetic evidence has shown that TGF-β canonical signaling-related genes have key roles in aortic aneurysms (AAs) and aortic dissections and many gene mutations have been identified in patients, such as those for transforming growth factor-beta receptor one TGFBR1, TGFBR2, SMAD2, SMAD3, SMAD4, and SMAD6. Aortic specimens from patients with these mutations often show paradoxically enhanced TGF-β signaling. Some hypotheses have been proposed and new AA models in mice have been constructed to reveal new mechanisms, but the role of TGF-β signaling in AAs is controversial. In this review, we focus mainly on the role of canonical signaling-related core genes in diseases of the aorta, as well as recent advances in gene-mutation detection, animal models, and in vitro studies.

RBPMS is an RNA-binding protein that mediates cardiomyocyte binucleation and cardiovascular development

Noncompaction cardiomyopathy is a common congenital cardiac disorder associated with abnormal ventricular cardiomyocyte trabeculation and impaired pump function. The genetic basis and underlying mechanisms of this disorder remain elusive. We show that the genetic deletion of RNA-binding protein with multiple splicing (Rbpms), an uncharacterized RNA-binding factor, causes perinatal lethality in mice due to congenital cardiovascular defects. The loss of Rbpms causes premature onset of cardiomyocyte binucleation and cell cycle arrest during development. Human iPSC-derived cardiomyocytes with RBPMS gene deletion have a similar blockade to cytokinesis. Sequencing analysis revealed that RBPMS plays a role in RNA splicing and influences RNAs involved in cytoskeletal signaling pathways. We found that RBPMS mediates the isoform switching of the heart-enriched LIM domain protein Pdlim5. The loss of Rbpms leads to an abnormal accumulation of Pdlim5-short isoforms, disrupting cardiomyocyte cytokinesis. Our findings connect premature cardiomyocyte binucleation to noncompaction cardiomyopathy and highlight the role of RBPMS in this process.

Mechano-regulated cell-cell signaling in the context of cardiovascular tissue engineering

Cardiovascular tissue engineering (CVTE) aims to create living tissues, with the ability to grow and remodel, as replacements for diseased blood vessels and heart valves. Despite promising results, the (long-term) functionality of these engineered tissues still needs improvement to reach broad clinical application. The functionality of native tissues is ensured by their specific mechanical properties directly arising from tissue organization. We therefore hypothesize that establishing a native-like tissue organization is vital to overcome the limitations of current CVTE approaches. To achieve this aim, a better understanding of the growth and remodeling (G&R) mechanisms of cardiovascular tissues is necessary. Cells are the main mediators of tissue G&R, and their behavior is strongly influenced by both mechanical stimuli and cell-cell signaling. An increasing number of signaling pathways has also been identified as mechanosensitive. As such, they may have a key underlying role in regulating the G&R of tissues in response to mechanical stimuli. A more detailed understanding of mechano-regulated cell-cell signaling may thus be crucial to advance CVTE, as it could inspire new methods to control tissue G&R and improve the organization and functionality of engineered tissues, thereby accelerating clinical translation. In this review, we discuss the organization and biomechanics of native cardiovascular tissues; recent CVTE studies emphasizing the obtained engineered tissue organization; and the interplay between mechanical stimuli, cell behavior, and cell-cell signaling. In addition, we review past contributions of computational models in understanding and predicting mechano-regulated tissue G&R and cell-cell signaling to highlight their potential role in future CVTE strategies.

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.

Integrated transcriptomics and epigenomics reveal chamber-specific and species-specific characteristics of human and mouse hearts

DNA methylation, chromatin accessibility, and gene expression represent different levels information in biological process, but a comprehensive multiomics analysis of the mammalian heart is lacking. Here, we applied nucleosome occupancy and methylome sequencing, which detected DNA methylation and chromatin accessibility simultaneously, as well as RNA-seq, for multiomics analysis of the 4 chambers of adult and fetal human hearts, and adult mouse hearts. Our results showed conserved region-specific patterns in the mammalian heart at transcriptome and DNA methylation level. Adult and fetal human hearts showed distinct features in DNA methylome, chromatin accessibility, and transcriptome. Novel long noncoding RNAs were identified in the human heart, and the gene expression profiles of major cardiovascular diseases associated genes were displayed. Furthermore, cross-species comparisons revealed human-specific and mouse-specific differentially expressed genes between the atria and ventricles. We also reported the relationship among multiomics and found there was a bell-shaped relationship between gene-body methylation and expression in the human heart. In general, our study provided comprehensive spatiotemporal and evolutionary insights into the regulation of gene expression in the heart.

Multi-omic analyses of the four chambers of the human and mouse heart, including transcriptome, DNA methylation and chromatin accessibility, reveals characteristic patterns of gene regulation at the level of heart regions.

Simvastatin protects heart function and myocardial energy metabolism in pulmonary arterial hypertension induced right heart failure

The favorable effect of simvastatin on pulmonary arterial hypertension (PAH) has been well defined despite the unknown etiology of PAH. However, whether simvastatin exerts similar effects on PAH induced right heart failure (RHF) remains to be determined. We aimed to investigate the function of simvastatin in PAH induced RHF. Rats in the RHF and simvastatin groups were injected intraperitoneally with monocrotaline to establish PAH-induced RHF model. The expression of miR-21-5p in rat myocardium was detected and miR-21-5p expression was inhibited using antagomiRNA. The effect of simvastatin on hemodynamic indexes, ventricular remodeling of myocardial tissues, myocardial energy metabolism, and calmodulin was explored. Dual-luciferase reporter system was used to verify the binding relationship between miR-21-5p and Smad7. In addition, the regulatory role of simvastatin in Smad7, TGFBR1 and Smad2/3 was investigated. Simvastatin treatment improved hemodynamic condition, myocardial tissue remodeling, and myocardial energy metabolism, as well as increasing calmodulin expression in rats with PAH-induced RHF. After simvastatin treatment, the expression of miR-21-5p in myocardium of rats was decreased significantly. miR-21-5p targeted Smad7 and inhibited the expression of Smad7. Compared with RHF rats, the expressions of TGFBR1 and Smad2/3 in myocardium of simvastatin-treated rats were decreased significantly. Collectively, we provided evidence that simvastatin can protect ATPase activity and maintain myocardial ATP energy reserve through the miR-21-5p/Smad/TGF-β axis, thus ameliorating PAH induced RHF.

Overexpression of Smad7 in hypothalamic POMC neurons disrupts glucose balance by attenuating central insulin signaling

OBJECTIVE

Although the hypothalamus is crucial for peripheral metabolism control, the signals in specific neurons involved remain poorly understood. The aim of our current study was to explore the role of the hypothalamic gene mothers against decapentaplegic homolog 7 (Smad7) in peripheral glucose disorders.

METHODS

We studied glucose metabolism in high-fat diet (HFD)-fed mice and middle-aged mice with Cre-mediated recombination causing 1) overexpression of Smad7 in hypothalamic proopiomelanocortin (POMC) neurons, 2) deletion of Smad7 in POMC neurons, and 3) overexpression of protein kinase B (AKT) in arcuate nucleus (ARC) in Smad7 overexpressed mice. Intracerebroventricular (ICV) cannulation of insulin was used to test the hypothalamic insulin sensitivity in the mice. Hypothalamic primary neurons were used to investigate the mechanism of Smad7 regulating hypothalamic insulin signaling.

RESULTS

We found that Smad7 expression was increased in POMC neurons in the hypothalamic ARC of HFD-fed or middle-aged mice. Furthermore, overexpression of Smad7 in POMC neurons disrupted the glucose balance, and deletion of Smad7 in POMC neurons prevented diet- or age-induced glucose disorders, which was likely to be independent of changes in body weight or food intake. Moreover, the effect of Smad7 was reversed by overexpression of AKT in the ARC. Finally, Smad7 decreased AKT phosphorylation by activating protein phosphatase 1c in hypothalamic primary neurons.

CONCLUSIONS

Our results demonstrated that an excess of central Smad7 in POMC neurons disrupts glucose balance by attenuating hypothalamic insulin signaling. In addition, we found that this regulation was mediated by the activity of protein phosphatase 1c.

Spontaneous Right Ventricular Pseudoaneurysms and Increased Arrhythmogenicity in a Mouse Model of Marfan Syndrome

Patients with Marfan syndrome (MFS), a connective tissue disorder caused by pathogenic variants in the gene encoding the extracellular matrix protein fibrillin-1, have an increased prevalence of primary cardiomyopathy, arrhythmias, and sudden cardiac death. We have performed an in-depth in vivo and ex vivo study of the cardiac phenotype of Fbn1mgR/mgR mice, an established mouse model of MFS with a severely reduced expression of fibrillin-1. Using ultrasound measurements, we confirmed the presence of aortic dilatation and observed cardiac diastolic dysfunction in male Fbn1mgR/mgR mice. Upon post-mortem examination, we discovered that the mutant mice consistently presented myocardial lesions at the level of the right ventricular free wall, which we characterized as spontaneous pseudoaneurysms. Histological investigation demonstrated a decrease in myocardial compaction in the MFS mouse model. Furthermore, continuous 24 h electrocardiographic analysis showed a decreased heart rate variability and an increased prevalence of extrasystolic arrhythmic events in Fbn1mgR/mgR mice compared to wild-type littermates. Taken together, in this paper we document a previously unreported cardiac phenotype in the Fbn1mgR/mgR MFS mouse model and provide a detailed characterization of the cardiac dysfunction and rhythm disorders which are caused by fibrillin-1 deficiency. These findings highlight the wide spectrum of cardiac manifestations of MFS, which might have implications for patient care.

The Role of Bone Morphogenetic Protein 7 (BMP-7) in Inflammation in Heart Diseases

Bone morphogenetic protein-7 is (BMP-7) is a potent anti-inflammatory growth factor belonging to the Transforming Growth Factor Beta (TGF-β) superfamily. It plays an important role in various biological processes, including embryogenesis, hematopoiesis, neurogenesis and skeletal morphogenesis. BMP-7 stimulates the target cells by binding to specific membrane-bound receptor BMPR 2 and transduces signals through mothers against decapentaplegic (Smads) and mitogen activated protein kinase (MAPK) pathways. To date, rhBMP-7 has been used clinically to induce the differentiation of mesenchymal stem cells bordering the bone fracture site into chondrocytes, osteoclasts, the formation of new bone via calcium deposition and to stimulate the repair of bone fracture. However, its use in cardiovascular diseases, such as atherosclerosis, myocardial infarction, and diabetic cardiomyopathy is currently being explored. More importantly, these cardiovascular diseases are associated with inflammation and infiltrated monocytes where BMP-7 has been demonstrated to be a key player in the differentiation of pro-inflammatory monocytes, or M1 macrophages, into anti-inflammatory M2 macrophages, which reduces developed cardiac dysfunction. Therefore, this review focuses on the molecular mechanisms of BMP-7 treatment in cardiovascular disease and its role as an anti-fibrotic, anti-apoptotic and anti-inflammatory growth factor, which emphasizes its potential therapeutic significance in heart diseases.

Signaling regulation during gastrulation: Insights from mouse embryos and in vitro systems

Gastrulation is the process whereby cells exit pluripotency and concomitantly acquire and pattern distinct cell fates. This is driven by the convergence of WNT, BMP, Nodal and FGF signals, which are tightly spatially and temporally controlled, resulting in regional and stage-specific signaling environments. The combination, level and duration of signals that a cell is exposed to, according its position within the embryo and the developmental time window, dictates the fate it will adopt. The key pathways driving gastrulation exhibit complex interactions, which are difficult to disentangle in vivo due to the complexity of manipulating multiple signals in parallel with high spatiotemporal resolution. Thus, our current understanding of the signaling dynamics regulating gastrulation is limited. In vitro stem cell models have been established, which undergo organized cellular differentiation and patterning. These provide amenable, simplified, deconstructed and scalable models of gastrulation. While the foundation of our understanding of gastrulation stems from experiments in embryos, in vitro systems are now beginning to reveal the intricate details of signaling regulation. Here we discuss the current state of knowledge of the role, regulation and dynamic interaction of signaling pathways that drive mouse gastrulation.

Bone morphogenetic protein signaling in inflammation

IMPACT STATEMENT

By compiling findings from recent studies, this review will garner novel insight on the dynamic and complex role of BMP signaling in diseases of inflammation, highlighting the specific roles played by both individual ligands and endogenous antagonists. Ultimately, this summary will help inform the high therapeutic value of targeting this pathway for modulating diseases of inflammation.

CRISPR/Cas9-mediated genome editing in human stem cell-derived cardiomyocytes: Applications for cardiovascular disease modelling and cardiotoxicity screening

Cardiovascular diseases (CVDs) are leading causes of death worldwide, and drug-induced cardiotoxicity is among the most common cause of drug withdrawal from the market. Improved models of cardiac tissue are needed to study the mechanisms of CVDs and drug-induced cardiotoxicity. Human pluripotent stem cell-derived cardiomyocytes (hPSC-CM) have provided a major advance to our ability to study these conditions. Combined with efficient genome editing technologies, such as CRISPR/Cas9, we now have the ability to study with greater resolution the genetic causes and underlying mechanisms of inherited and drug-induced cardiotoxicity, and to investigate new treatments. Here, we review recent advances in the use of hPSC-CMs and CRISPR/Cas9-mediated genome editing to study cardiotoxicity and model CVD.

MicroRNA‑20b‑5p promotes ventricular remodeling by targeting the TGF‑β/Smad signaling pathway in a rat model of ischemia‑reperfusion injury

Myocardial ischemic injury results from severe impairment of the coronary blood supply and may lead to metabolic and ultrastructural changes, thereby causing irreversible damage. MicroRNA (miR)-20b-5p has been demonstrated to be involved in malignancies of the breast, colorectum, stomach, blood and oropharynx. The present study aimed to investigate the effects of miR-20b-5p on ventricular remodeling following myocardial ischemia-reperfusion (IR) injury in rats by targeting small mothers against decapentaplegic homolog 7 (Smad7) via the transforming growth factor-β (TGF-β)/Smad signaling pathway. A total of 70 adult male Sprague-Dawley rats were divided into seven groups: Sham group, IR group, negative control group, miR-20b-5p mimics group, miR-20b-5p inhibitors group, small interfering RNA (siRNA)-Smad7 group, and miR-20b-5p inhibitors + siRNA-Smad7 group. Dual luciferase reporter gene assays were used to verify the association between miR-20b-5p and Smad7. Myocardial infarction size, myocardial collagen volume fraction and perivascular collagen area were detected separately using triphenyltetrazolium chloride and Masson's staining. The rate of positive expression of Smad7 was detected using immunohistochemistry, and the expression levels of miR-20b-5p, TGF-β1, Smad3 and Smad7 were detected using reverse transcription-quantitative polymerase chain reaction and western blot analyses. The findings revealed that miR-20b-5p inhibited Smad7. Compared with the sham group, the other six groups had increased myocardial infarction size, myocardial collagen, and expression of miR-20b-5p, TGF-β1 and Smad3, and decreased expression of Smad7. Compared with the IR group, the miR-20b-5p mimics group and the siRNA-Smad7 group had increased myocardial infarction size and myocardial collagen, increased expression of TGF-β1 and Smad3, and decreased expression of Smad7. The expression of miR-20b-5p was markedly increased in the miR-20b-5p mimics group, but did not differ significantly from that in the siRNA-Smad7 group. The results demonstrated that miR-20b-5p promoted ventricular remodeling following myocardial IR injury in rats by inhibiting the expression of Smad7 through activating the TGF-β/Smad signaling pathway.

Neddylation mediates ventricular chamber maturation through repression of Hippo signaling

During development, ventricular chamber maturation is a crucial step in the formation of a functionally competent postnatal heart. Defects in this process can lead to left ventricular noncompaction cardiomyopathy and heart failure. However, molecular mechanisms underlying ventricular chamber development remain incompletely understood. Neddylation is a posttranslational modification that attaches ubiquitin-like protein NEDD8 to protein targets via NEDD8-specific E1-E2-E3 enzymes. Here, we report that neddylation is temporally regulated in the heart and plays a key role in cardiac development. Cardiomyocyte-specific knockout of NAE1, a subunit of the E1 neddylation activating enzyme, significantly decreased neddylated proteins in the heart. Mice lacking NAE1 developed myocardial hypoplasia, ventricular noncompaction, and heart failure at late gestation, which led to perinatal lethality. NAE1 deletion resulted in dysregulation of cell cycle-regulatory genes and blockade of cardiomyocyte proliferation in vivo and in vitro, which was accompanied by the accumulation of the Hippo kinases Mst1 and LATS1/2 and the inactivation of the YAP pathway. Furthermore, reactivation of YAP signaling in NAE1-inactivated cardiomyocytes restored cell proliferation, and YAP-deficient hearts displayed a noncompaction phenotype, supporting an important role of Hippo-YAP signaling in NAE1-depleted hearts. Mechanistically, we found that neddylation regulates Mst1 and LATS2 degradation and that Cullin 7, a NEDD8 substrate, acts as the ubiquitin ligase of Mst1 to enable YAP signaling and cardiomyocyte proliferation. Together, these findings demonstrate a role for neddylation in heart development and, more specifically, in the maturation of ventricular chambers and also identify the NEDD8 substrate Cullin 7 as a regulator of Hippo-YAP signaling.

The TGFβ superfamily in cardiac dysfunction

TGFβ superfamily includes the transforming growth factor βs (TGFβs), bone morphogenetic proteins (BMPs), growth and differentiation factors (GDFs) and Activin/Inhibin families of ligands. Among the 33 members of TGFβ superfamily ligands, many act on multiple types of cells within the heart, including cardiomyocytes, cardiac fibroblasts/myofibroblasts, coronary endothelial cells, smooth muscle cells, and immune cells (e.g. monocytes/macrophages and neutrophils). In this review, we highlight recent discoveries on TGFβs, BMPs, and GDFs in different cardiac residential cellular components, in association with functional impacts in heart development, injury repair, and dysfunction. Specifically, we will review the roles of TGFβs, BMPs, and GDFs in cardiac hypertrophy, fibrosis, contractility, metabolism, angiogenesis, and regeneration.

miR-181b-induced SMAD7 downregulation controls granulosa cell apoptosis through TGF-β signaling by interacting with the TGFBR1 promoter

SMAD7 disrupts the TGF-β signaling pathway by influencing TGFBR1 stability and by blocking the binding of TGFBR1 to SMAD2/3. In this study, we showed that SMAD7 attenuated the TGF-β signaling pathway in ovarian granulosa cells (GCs) by regulating TGFBR1 transcriptional activity. To function as a transcription factor, SMAD7 downregulated the mRNA levels of TGFBR1 via direct binding to the SMAD-binding elements (SBEs) within the promoter region of pig TGFBR1. We also showed that SMAD7 enhanced porcine GC apoptosis by interrupting TGFBR1 and the TGF-β signaling pathway. Interestingly, miR-181b, a microRNA that is downregulated during porcine follicular atresia, was identified to be directly targeting SMAD7 at its 3'-UTR. By inhibiting SMAD7, miR-181b could inhibit GC apoptosis by activating the TGF-β signaling pathway. Our findings provide new insights into the mechanisms underlying the regulation of the TGF-β signaling pathway by SMAD7 and miR-181b.

Smad7 deficiency decreases iron and haemoglobin through hepcidin up-regulation by multilayer compensatory mechanisms

To maintain iron homoeostasis, the iron regulatory hormone hepcidin is tightly controlled by BMP-Smad signalling pathway, but the physiological role of Smad7 in hepcidin regulation remains elusive. We generated and characterized hepatocyte-specific Smad7 knockout mice (Smad7^Alb/Alb ), which showed decreased serum iron, tissue iron, haemoglobin concentration, up-regulated hepcidin and increased phosphor-Smad1/5/8 levels in both isolated primary hepatocytes and liver tissues. Increased levels of hepcidin lead to reduced expression of intestinal ferroportin and mild iron deficiency anaemia. Interestingly, we found no difference in hepcidin expression or phosphor-Smad1/5/8 levels between iron-challenged Smad7^Alb/Alb and Smad7^flox/flox , suggesting other factors assume the role of iron-induced hepcidin regulation in Smad7 deletion. We performed RNA-seq to identify differentially expressed genes in the liver. Significantly up-regulated genes were then mapped to pathways, revealing TGF-β signalling as one of the most relevant pathways, including the up-regulated genes Smad6, Bambi and Fst (Follistatin). We found that Smad6 and Bambi-but not Follistatin-are controlled by the iron-BMP-Smad pathway. Overexpressing Smad6, Bambi or Follistatin in cells significantly reduced hepcidin expression. Smad7 functions as a key regulator of iron homoeostasis by negatively controlling hepcidin expression, and Smad6 and Smad7 have non-redundant roles. Smad6, Bambi and Follistatin serve as additional inhibitors of hepcidin in the liver.

Exosomes derived from human umbilical cord mesenchymal stem cells improve myocardial repair via upregulation of Smad7

It has been previously reported that exosomes derived from human umbilical cord mesenchymal stem cells (hucMSC)‑exosomes exhibit cardioprotective effects on the rat acute myocardial infarction (AMI) models and cardiomyocyte hypoxia injury models in vitro, however the exact mechanisms involved require further investigation. The present study aimed to investigate the repair effects of hucMSC‑exosomes on myocardial injury via the regulation of mothers against decapentaplegic homolog 7 (Smad7) expression. Compared with sham or normoxia groups (in vivo and in vitro, respectively), western blotting demonstrated that Smad7 expression was significantly decreased in the borderline area of infraction myocardium and in H9C2(2‑1) cells following hypoxia‑induced injury. Additionally, microRNA (miR)‑125b‑5p expression was markedly increased using reverse transcription‑quantitative polymerase chain reaction, but was reversed by hucMSC‑exosomes. Trypan blue staining and lactate dehydrogenase release detection demonstrated that cell injury was significantly increased in the AMI + PBS and hypoxia group compared with in the sham and normoxia groups and was inhibited by hucMSC‑exosomes. A dual luciferase reporter gene assay confirmed that Smad7 is a target gene of miR‑125b‑5p. In addition, miR‑125b‑5p mimics promoted H9C2(2‑1) cell injury following 48 h exposure to hypoxia. Downregulation of Smad7 expression under hypoxia was increased by miR‑125b‑5p mimics compared with the mimic negative control, and hucMSC‑exosomes partially alleviated this phenomenon. In conclusion, hucMSC‑exosomes may promote Smad7 expression by inhibiting miR‑125b‑5p to increase myocardial repair. The present study may provide a potential therapeutic approach to improve myocardial repair following AMI.

The Role of Hedgehog Signalling in the Formation of the Ventricular Septum

An incomplete septation of the ventricles in the vertebrate heart that disturbes the strict separation between the contents of the two ventricles is termed a ventricular septal defect (VSD). Together with bicuspid aortic valves, it is the most frequent congenital heart disease in humans. Until now, life-threatening VSDs are usually treated surgically. To avoid surgery and to develop an alternative therapy (e.g., a small molecule therapy), it is necessary to understand the molecular mechanisms underlying ventricular septum (VS) development. Consequently, various studies focus on the investigation of signalling pathways, which play essential roles in the formation of the VS. In the past decade, several reports found evidence for an involvement of Hedgehog (HH) signalling in VS development. In this review article, we will summarise the current knowledge about the association between HH signalling and VS formation and discuss the use of such knowledge to design treatment strategies against the development of VSDs.

SMAD7 deficiency stimulates Müller progenitor cell proliferation during the development of the mammalian retina

The transforming growth factor-β (TGF-β) pathway contributes to maintain the quiescence of adult neural stem and progenitor cells in the brain. In the retina, Müller cells are discussed to represent a glial cell population with progenitor-like characteristics. Here, we aimed to investigate if elevated TGF-β signaling modulates the proliferation of Müller cells during retinal development. We generated mutant mice with a systemic, heterozygous up-regulation of TGF-β signaling by deleting its inhibitor SMAD7. We investigated apoptosis, proliferation, and differentiation of Müller cells in the developing retina. We show that a heterozygous deletion of SMAD7 results in an increased proliferation of Müller cell progenitors in the central retina at postnatal day 4, the time window when Müller cells differentiate in the mouse retina. This in turn results in a thickened retina and inner nuclear layer and a higher number of differentiated Müller cells in the more developed retina. Müller cells in mutant mice contain higher amounts of nestin than those of control animals which indicates that the increase in TGF-β signaling activity during retinal development contribute to maintain some progenitor-like characteristics in Müller cells even after their differentiation period. We conclude that TGF-β signaling influences Müller cell proliferation and differentiation during retinal development.

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.

Genome-wide methylation analysis identifies novel CpG loci for perimembranous ventricular septal defects in human

Aim: Congenital heart diseases are the most common birth defects worldwide and leading cause of infant mortality. The perimembranous ventricular septal defect is most prevalent. Epigenetics may provide an underlying mechanism of the gene–environment interactions involved. Materials & methods: We examined epigenome-wide DNA methylation using the Illumina HumanMethylation450 BeadChip in 84 case children and 196 control children. Results: We identified differential methylation of a CpG locus (cg17001566) within the PRDM16 gene after Bonferroni correction (p = 9.17 × 10-8). This was validated by bisulfite pyrosequencing. PRDM16 functions as a repressor of TGF-β signaling controlling tissue morphogenesis crucial during cardiogenesis. At 15% false-discovery rate, we identified seven additional CpG loci. Conclusion: These findings provide novel insights in the pathogenesis of perimembranous ventricular septal defect, which is of interest for future prediction and prevention.

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.

Screening of SMAD7 in Malay patients with ventricular septal defect

Ventricular septal defect (VSD) is the most common form of cardiac malformations accounting approximately 20% of all congenital heart defects. SMAD7 is an inhibitory protein that antagonizes the signalling of TGF-β family member and has been found in the development and function of mouse heart models. This study aims to screen and identify the polymorphisms of SMAD7 exonic regions in Malay population with VSD. Peripheral blood samples were collected and extracted from 30 clinically diagnosed VSD patients. PCR amplification was performed using 12 sets of designed primers encompassing seven exons of SMAD7. Re-sequencing was conducted to characterize the polymorphisms of SMAD7. Observed polymorphisms were then genotyped in 30 healthy individuals using both re-sequencing and allele-specific PCR techniques. A total of 10 variants were identified in the patient population located in the upstream (rs7236774), exonic (rs368427729, rs145686330, rs3764482, rs3809922, rs780863704 and rs3809923), intronic (rs3736242) and 3'UTR regions (rs375444823 and rs16950113). No significant difference of genotype and allele frequency was observed among these SNPs. Two synonymous variants (rs3809922 and rs3809923) were found in complete linkage disequilibrium (r²=1.0) with each other indicate a strong correlation of these SNPs. The identification of these SNPs provides a new perspective of the VSD causation.

iPSC-derived cardiomyocytes reveal abnormal TGF-β signalling in left ventricular non-compaction cardiomyopathy

Left ventricular non-compaction (LVNC) is the third most prevalent cardiomyopathy in children and its pathogenesis has been associated with the developmental defect of the embryonic myocardium. We show that patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from LVNC patients carrying a mutation in the cardiac transcription factor TBX20 recapitulate a key aspect of the pathological phenotype at the single-cell level and this was associated with perturbed transforming growth factor beta (TGF-β) signalling. LVNC iPSC-CMs have decreased proliferative capacity due to abnormal activation of TGF-β signalling. TBX20 regulates the expression of TGF-β signalling modifiers including one known to be a genetic cause of LVNC, PRDM16, and genome editing of PRDM16 caused proliferation defects in iPSC-CMs. Inhibition of TGF-β signalling and genome correction of the TBX20 mutation were sufficient to reverse the disease phenotype. Our study demonstrates that iPSC-CMs are a useful tool for the exploration of pathological mechanisms underlying poorly understood cardiomyopathies including LVNC.

Generation and Characterization of Smad7 Conditional Knockout Mice

Smad7 is an important negative modulator that regulates the duration and strength of TGF-β signaling. Dysregulation of Smad7 is associated with the pathogenesis of many human diseases. Various mouse models are developed to facilitate addressing the physiological functions of Smad7. We have recently demonstrated that loss of Smad7 function by deletion in its MH2 domain leads to multiple cardiac defects and aggravates ethanol-induced liver injury. Here, we describe the procedure to construct and characterize the Smad7 conditional knockout mice.

Phosphorylation of the chromatin remodeling factor DPF3a induces cardiac hypertrophy through releasing HEY repressors from DNA

DPF3 (BAF45c) is a member of the BAF chromatin remodeling complex. Two isoforms have been described, namely DPF3a and DPF3b. The latter binds to acetylated and methylated lysine residues of histones. Here, we elaborate on the role of DPF3a and describe a novel pathway of cardiac gene transcription leading to pathological cardiac hypertrophy. Upon hypertrophic stimuli, casein kinase 2 phosphorylates DPF3a at serine 348. This initiates the interaction of DPF3a with the transcriptional repressors HEY, followed by the release of HEY from the DNA. Moreover, BRG1 is bound by DPF3a, and is thus recruited to HEY genomic targets upon interaction of the two components. Consequently, the transcription of downstream targets such as NPPA and GATA4 is initiated and pathological cardiac hypertrophy is established. In human, DPF3a is significantly up-regulated in hypertrophic hearts of patients with hypertrophic cardiomyopathy or aortic stenosis. Taken together, we show that activation of DPF3a upon hypertrophic stimuli switches cardiac fetal gene expression from being silenced by HEY to being activated by BRG1. Thus, we present a novel pathway for pathological cardiac hypertrophy, whose inhibition is a long-term therapeutic goal for the treatment of the course of heart failure.

Embryonic Lethality Due to Arrested Cardiac Development in Psip1/Hdgfrp2 Double-Deficient Mice

Hepatoma-derived growth factor (HDGF) related protein 2 (HRP2) and lens epithelium-derived growth factor (LEDGF)/p75 are closely related members of the HRP2 protein family. LEDGF/p75 has been implicated in numerous human pathologies including cancer, autoimmunity, and infectious disease. Knockout of the Psip1 gene, which encodes for LEDGF/p75 and the shorter LEDGF/p52 isoform, was previously shown to cause perinatal lethality in mice. The function of HRP2 was by contrast largely unknown. To learn about the role of HRP2 in development, we knocked out the Hdgfrp2 gene, which encodes for HRP2, in both normal and Psip1 knockout mice. Hdgfrp2 knockout mice developed normally and were fertile. By contrast, the double deficient mice died at approximate embryonic day (E) 13.5. Histological examination revealed ventricular septal defect (VSD) associated with E14.5 double knockout embryos. To investigate the underlying molecular mechanism(s), RNA recovered from ventricular tissue was subjected to RNA-sequencing on the Illumina platform. Bioinformatic analysis revealed several genes and biological pathways that were significantly deregulated by the Psip1 knockout and/or Psip1/Hdgfrp2 double knockout. Among the dozen genes known to encode for LEDGF/p75 binding factors, only the expression of Nova1, which encodes an RNA splicing factor, was significantly deregulated by the knockouts. However the expression of other RNA splicing factors, including the LEDGF/p52-interacting protein ASF/SF2, was not significantly altered, indicating that deregulation of global RNA splicing was not a driving factor in the pathology of the VSD. Tumor growth factor (Tgf) β-signaling, which plays a key role in cardiac morphogenesis during development, was the only pathway significantly deregulated by the double knockout as compared to control and Psip1 knockout samples. We accordingly speculate that deregulated Tgf-β signaling was a contributing factor to the VSD and prenatal lethality of Psip1/Hdgfrp2 double-deficient mice.

Left ventricular non-compaction cardiomyopathy

Left ventricular non-compaction, the most recently classified form of cardiomyopathy, is characterised by abnormal trabeculations in the left ventricle, most frequently at the apex. It can be associated with left ventricular dilation or hypertrophy, systolic or diastolic dysfunction, or both, or various forms of congenital heart disease. Affected individuals are at risk of left or right ventricular failure, or both. Heart failure symptoms can be induced by exercise or be persistent at rest, but many patients are asymptomatic. Patients on chronic treatment for compensated heart failure sometimes present acutely with decompensated heart failure. Other life-threatening risks of left ventricular non-compaction are ventricular arrhythmias or complete atrioventricular block, presenting clinically as syncope, and sudden death. Genetic inheritance arises in at least 30-50% of patients, and several genes that cause left ventricular non-compaction have been identified. These genes seem generally to encode sarcomeric (contractile apparatus) or cytoskeletal proteins, although, in the case of left ventricular non-compaction with congenital heart disease, disturbance of the NOTCH signalling pathway seems part of a final common pathway for this form of the disease. Disrupted mitochondrial function and metabolic abnormalities have a causal role too. Treatments focus on improvement of cardiac efficiency and reduction of mechanical stress in patients with systolic dysfunction. Further, treatment of arrhythmia and implantation of an automatic implantable cardioverter-defibrillator for prevention of sudden death are mainstays of therapy when deemed necessary and appropriate. Patients with left ventricular non-compaction and congenital heart disease often need surgical or catheter-based interventions. Despite progress in diagnosis and treatment in the past 10 years, understanding of the disorder and outcomes need to be improved.

Heterozygous modulation of TGF-β signaling does not influence Müller glia cell reactivity or proliferation following NMDA-induced damage

The stimulation of progenitor or stem cells proliferation in the retina could be a therapeutic avenue for the treatment of various ocular neurodegenerative disorders. Müller glia cells have been discussed to represent a progenitor cell population in the adult retina. In the brain, TGF-β signaling regulates the fate of stem cells; however, its role in the vertebrate retina is unclear. We therefore investigated whether manipulation of the TGF-β signaling pathway is sufficient to promote Müller glia cell proliferation and subsequently their trans-differentiation into retinal neurons. To this end, we used mice with heterozygous deficiency of the essential TGF-β receptor type II or of the inhibitory protein SMAD7, in order to down- or up-regulate the activity of TGF-β signaling, respectively. Excitotoxic damage was applied by intravitreal N-methyl-D-aspartate injection, and BrdU pulse experiments were used to label proliferative cells. Although we successfully stimulated Müller glia cell reactivity, our findings indicate that a moderate modulation of TGF-β signaling is not sufficient to provoke Müller glia cell proliferation. Hence, TGF-β signaling in the retina might not be the essential causative factor to maintain mammalian Müller cells in a quiescent, non-proliferative state that prevents a stem cell-like function.

A novel association of biventricular cardiac noncompaction and diabetic embryopathy: case report and review of the literature

Diabetic embryopathy refers to a constellation of congenital malformations arising in the setting of poorly controlled maternal diabetes mellitus. Cardiac abnormalities are the most frequently observed findings, with a 5-fold risk over normal pregnancies. Although a diverse spectrum of cardiac defects has been documented, cardiac noncompaction morphology has not been associated with this syndrome. In this report, we describe a novel case of biventricular cardiac noncompaction in a neonate of a diabetic mother. The patient was a late preterm female with right anotia, caudal dysgenesis, multiple cardiac septal and aortic arch defects, and biventricular cardiac noncompaction. Examination of both ventricles demonstrated spongy myocardium with increased myocardial trabeculation greater than 50% left ventricular thickness and greater than 75% right ventricular thickness, with hypoplasia of the bilateral papillary muscles, consistent with noncompaction morphology. Review of the literature highlights the importance of gene expression and epigenomic regulation in cardiac embryogenesis.

Inhibitory SMADs: potential regulators of ovarian function

Transforming growth factor beta (TGFB) superfamily signaling regulates essential reproductive functions. Dysregulation of TGFB signaling results in cellular and molecular deficiencies in the ovary, leading to reproductive diseases and cancer development. SMAD proteins are canonical TGFB signaling components consisting of receptor-regulated SMADs (SMAD1/2/3/5/9), a common SMAD (SMAD4), and inhibitory SMADs (SMAD6/7). Inhibitory SMADs are negative regulators of TGFB and bone morphogenetic protein signaling, and their reproductive functions are poorly defined. Emerging evidence supports that inhibitory SMADs are potential regulators of ovarian function. Further efforts and new genetic models are needed to unveil the role of inhibitory SMADs in the ovary.

Oocyte-derived Smad4 is not required for development of the oocyte or the preimplantation embryo

The generation of a competent egg requires complex molecular interactions between the oocyte and the ovary, and transforming growth factor β (TGF-β) is a major signaling pathway. Smad4 is a central regulator of the TGF-β signaling pathway as it mediates gene expression triggered by activation of TGF-β receptors. Deletion of Smad4 in granulosa cells disrupts follicle development; however, the role of Smad4 in the oocyte has not been confirmed. Furthermore, the role of Smad4 in embryo development has not been confirmed because previous studies of Smad4(del/del) embryos were generated from heterozygous parents, and thus it is possible that maternal transcripts rescue development before embryonic day 6.5 (E6.5) when Smad4(del/del) embryos die. To determine the role of TGF-β signaling in oocyte and embryo development, mice with oocyte-specific deletion of Smad4 were studied. Fertility was evaluated in Mutant (Smad4(F/F):ZP3Cre) and CONTROL (Smad4(F/F)) females mated continuously with control males during a 6-month period. Surprisingly, Mutant females were fertile with the same litter size (Mutants, 9.23 ± 0.4; CONTROLs, 9.42 ± 0.4) and interlitter period as CONTROLs. Ovulation rate induced using a superovulation regime did not differ between CONTROLs and Mutants at both 6 weeks and 6 months. Embryo development was assessed at E6.5 using CONTROL and Mutant females mated with heterozygous males. Development of Smad4(del/del) embryos at E6.5 was retarded consistent with previous studies of embryos generated from heterozygous parents indicating that there is no rescue of preimplantation development by maternal transcripts. The numbers of implanted embryos at 6.5 dpc also did not differ (

CONTROL

9.1 ± 0.4; Mutant: 7.0 ± 0.9). However, only 26.3% of E6.5 embryos carried by Mutant females were Smad4(del/del) compared with the expected ratio of 50%. Since litter size was not decreased, this indicates that either the number of Smad4(del) sperm fertilizing the oocytes is reduced or implantation of Smad4(del/del) embryos is suboptimal. In summary, we have shown that Smad4 in the oocyte, and thus TGF-β signaling, is not required for oocyte or follicle development, ovulation, fertilization, preimplantation development, or implantation.

Bone Morphogenetic Protein (BMP) signaling in development and human diseases

Bone Morphogenetic Proteins (BMPs) are a group of signaling molecules that belongs to the Transforming Growth Factor-β (TGF-β) superfamily of proteins. Initially discovered for their ability to induce bone formation, BMPs are now known to play crucial roles in all organ systems. BMPs are important in embryogenesis and development, and also in maintenance of adult tissue homeostasis. Mouse knockout models of various components of the BMP signaling pathway result in embryonic lethality or marked defects, highlighting the essential functions of BMPs. In this review, we first outline the basic aspects of BMP signaling and then focus on genetically manipulated mouse knockout models that have helped elucidate the role of BMPs in development. A significant portion of this review is devoted to the prominent human pathologies associated with dysregulated BMP signaling.

Critical roles of miRNA-mediated regulation of TGFβ signalling during mouse cardiogenesis

AIMS

MicroRNAs (miRNAs) play critical roles during the development of the cardiovascular system. Blocking miRNA biosynthesis in embryonic hearts through a conditional gene inactivation approach led to differential cardiac defects depending on the Cre drivers used in different studies. The goal of this study is to reveal the cardiogenic pathway that is regulated by the miRNA mechanism at midgestation, a stage that has not been evaluated in previous publications.

METHODS AND RESULTS

We specifically inactivated Dicer1, which is essential for generation of functional mature miRNAs, in the myocardium by crossing cTnt-Cre mice with Dicer1(loxP) mice. cTnt-Cre efficiently inactivates target genes in cardiomyocytes at midgestation. All mutants died between E14.5 and E16.5 with severe myocardial wall defects, including reduced cell proliferation, increased cell death, and spongy myocardial wall. Expression of TGFβ type I receptor (Tgfbr1), which encodes the Type I receptor of TGFβ ligands, was up-regulated in mutant hearts. As expected, TGFβ activity was increased in Dicer1-inactivated hearts. Our further molecular analysis suggested that Tgfbr1 is a direct target of three miRNAs. Reducing TGFβ activities using a pharmacological inhibitor on in vitro cultured hearts, or through an in vivo genetic approach, partially rescued the cardiac defects caused by Dicer1 inactivation.

CONCLUSIONS

We show for the first time that TGFβ signalling is directly regulated by the miRNA mechanism during myocardial wall morphogenesis. Increased TGFβ activity plays a major role in the cardiac defects caused by myocardial deletion of Dicer1. Thus, miRNA-mediated regulation of TGFβ signalling is indispensable for normal cardiogenesis.

Transforming growth factor-β signaling in T cells promotes stabilization of atherosclerotic plaques through an interleukin-17-dependent pathway

Adaptive immunity has a major impact on atherosclerosis, with pro- and anti-atherosclerotic effects exerted by different subpopulations of T cells. Transforming growth factor-β (TGF-β) may promote development either of anti-atherosclerotic regulatory T cells or of T helper 17 (TH17) cells, depending on factors in the local milieu. We have addressed the effect on atherosclerosis of enhanced TGF-β signaling in T cells. Bone marrow from mice with a T cell-specific deletion of Smad7, a potent inhibitor of TGF-β signaling, was transplanted into hypercholesterolemic Ldlr(-/-) mice. Smad7-deficient mice had significantly larger atherosclerotic lesions that contained large collagen-rich caps, consistent with a more stable phenotype. The inflammatory cytokine interleukin-6 (IL-6) was expressed in the atherosclerotic aorta, and increased mRNA for IL-17A and the TH17-specific transcription factor RORγt were detected in draining lymph nodes. Treating Smad7-deficient chimeras with neutralizing IL-17A antibodies reversed stable cap formation. IL-17A stimulated collagen production by human vascular smooth muscle cells, and RORγt mRNA correlated positively with collagen type I and α-smooth muscle actin mRNA in a biobank of human atherosclerotic plaques. These data link IL-17A to induction of a stable plaque phenotype, could lead to new plaque-stabilizing therapies, and should prompt an evaluation of cardiovascular events in patients treated with IL-17 receptor blockade.

Multimodal ultrasound-photoacoustic imaging of tissue engineering scaffolds and blood oxygen saturation in and around the scaffolds

Preclinical, noninvasive imaging of tissue engineering polymeric scaffold structure and/or the physiological processes such as blood oxygenation remains a challenge. In vitro or ex vivo, the widely used scaffold characterization modalities such as porosimetry, electron or optical microscopy, and X-ray microcomputed tomography have limitations or disadvantages-some are invasive or destructive, others have limited tissue penetration (few hundred micrometers) and/or show poor contrast under physiological conditions. Postmortem histological analysis, the most robust technique for the evaluation of neovascularization is obviously not appropriate for acquiring physiological or longitudinal data. In this study, we have explored the potential of ultrasound (US)-coregistered photoacoustic (PA) imaging as a noninvasive multimodal imaging modality to overcome some of the above challenges and/or provide complementary information. US-PA imaging was employed to characterize poly(lactic-co-glycolic acid) (PLGA) polymer scaffolds or single-walled carbon nanotube (SWCNT)-incorporated PLGA (SWCNT-PLGA) polymer scaffolds as well as blood oxygen saturation within and around the scaffolds. Ex vivo, PLGA and SWCNT-PLGA scaffolds were placed at 0.5, 2, and 6 mm depths in chicken breast tissues. PLGA scaffolds could be localized with US imaging, but generate no PA signal (excitation wavelengths 680 and 780 nm). SWCNT-PLGA scaffolds generated strong PA signals at both wavelengths due to the presence of the SWCNTs and could be localized with both US and PA imaging depths between 0.5-6 mm (lateral resolution = 90 μm, axial resolution = 40 μm). In vivo, PLGA and SWCNT-PLGA scaffolds were implanted in subcutaneous pockets at 2 mm depth in rats, and imaged at 7 and 14 days postsurgery. The anatomical position of both the scaffolds could be determined from the US images. Only SWCNT-PLGA scaffolds could be easily detected in the US-PA images. SWCNT-PLGA scaffolds had significant four times higher PA signal intensity compared with the surrounding tissue and PLGA scaffolds. In vivo blood oxygen saturation maps around and within the PLGA scaffolds could be obtained by PA imaging. There was no significant difference in oxygen saturation for the PLGA scaffolds at the two time points. The blood oxygen saturation maps complemented the histological analysis of neovascularization of the PLGA scaffolds.

Yin Yang 1 (YY1) synergizes with Smad7 to inhibit TGF-β signaling in the nucleus

As a prototype of the TGF-β superfamily cytokines, TGF-β is well known for its diverse roles in embryogenesis and adult tissue homeostasis. TGF-β evokes cellular responses by signaling mainly through cell membrane receptors and transcription factor R-Smads and Co-Smad (Smad4), while an inhibitory Smad, Smad7, acts as a critical negative regulator of TGF-β signaling. Smad7 antagonizes TGF-β signaling by regulating the stability or activity of the receptors or blocking the DNA binding of the functional R-Smad-Smad4 complex in the nucleus. However, the function of Smad7 in the nucleus is not fully understood. Yin Yang 1 (YY1) is a ubiquitously expressed transcription factor with multiple functions. It has been reported that YY1 can inhibit Smad-dependent transcriptional responses and TGF-β/BMP-induced cell differentiation independently of its DNA binding ability. In this study, we found that Smad7 interacts with YY1 and the interaction is attenuated by TGF-β signaling. Reporter assays and target gene expression analyses revealed that Smad7 and YY1 act in concert to inhibit TGF-β-induced transcription in the nucleus. Furthermore, Smad7 could enhance the interaction of YY1 with the histone deacetylase HDAC1. Consistently, YY1 and HDAC1 augmented the transcription repression activity of Smad7 in Gal4-luciferase reporter analysis. Therefore, our findings define a novel mechanism of Smad7 and YY1 to antagonize TGF-β signaling.

The dual role of Smad7 in the control of cancer growth and metastasis

Smad7 was initially identified as an inhibitor of Transforming growth factor (TGF)-β due mainly to its ability to bind TGF-β receptor type I and prevent TGF-β-associated Smad signaling. More recently, it has been demonstrated that Smad7 can interact with other intracellular proteins and regulate also TGF-β-independent signaling pathways thus making a valid contribution to the neoplastic processes in various organs. In particular, data emerging from experimental studies indicate that Smad7 may differently modulate the course of various tumors depending on the context analyzed. These observations, together with the demonstration that Smad7 expression is deregulated in many cancers, suggest that therapeutic interventions around Smad7 can help interfere with the development/progression of human cancers. In this article we review and discuss the available data supporting the role of Smad7 in the modulation of cancer growth and progression.

CHD7 interacts with BMP R-SMADs to epigenetically regulate cardiogenesis in mice

Haploinsufficiency for CHD7, an ATP-dependent nucleosome remodeling factor, is the leading cause of CHARGE syndrome. While congenital heart defects (CHDs) are major clinical features of CHARGE syndrome, affecting >75% of patients, it remains unclear whether CHD7 can directly regulate cardiogenic genes in embryos. Our complementary yeast two-hybrid and biochemical assays reveal that CHD7 is a novel interaction partner of canonical BMP signaling pathway nuclear mediators, SMAD1/5/8, in the embryonic heart. Moreover, CHD7 associates in a BMP-dependent manner with the enhancers of a critical cardiac transcription factor, Nkx2.5, that contain functional SMAD1-binding elements. Both the active epigenetic signature of Nkx2.5 regulatory elements and its proper expression in cardiomyocytes require CHD7. Finally, inactivation of Chd7 in mice impairs multiple BMP signaling-regulated cardiogenic processes. Our results thus support the model that CHD7 is recruited by SMAD1/5/8 to the enhancers of BMP-targeted cardiogenic genes to epigenetically regulate their expression. Impaired BMP activities in embryonic hearts may thus have a major contribution to CHDs in CHARGE syndrome.

Association of two variants in SMAD7 with the risk of congenital heart disease in the Han Chinese population

SMAD7 is a general antagonist of TGF-β signaling and has been found to be involved in cardiogenesis in mouse models, but its role in human congenital heart disease (CHD) has yet to be investigated. To examine if SMAD7 is associated with CHD, we conducted a case-control study in the Han Chinese population. Exon1 and exon4 of SMAD7, which encode the functional MH1 and MH2 domains, were directly sequenced in 1,201 sporadic CHD patients and 1,116 control individuals. A total of 18 sequence variations were identified. Two common variants rs3809922 and rs3809923 are located at exon4 of SMAD7, and were found in strong linkage disequilibrium with each other (r² = 0.93). We analyzed the association of these two loci with CHD in 3 independent subgroup case-control studies, and found that in some subgroups, rs3809922 and rs3809923 were significantly associated with CHD through genetic model analysis. In the combined data set, TT genotype in rs3809922 significantly increased the risk of CHD compared with CC and CT, while GG genotype in rs3809923 significantly increased the risk of CHD compared with CC and CG, particularly in the recessive model. In addition, haplotype analyses showed that haplotype TG significantly increased the risk of CHD (P = 6.9×10⁻⁶); this finding supports the results from the analyses based on single locus. According to data from the 1000 Genomes Project, the frequencies of the two risk alleles varied greatly between populations worldwide, which indicate the identified associations might have a population difference. To our knowledge, this is the first report that genetic variants in SMAD7 influence susceptibility to CHD risk.

Co-ordinating Notch, BMP, and TGF-β signaling during heart valve development

Congenital heart defects affect approximately 1-5 % of human newborns each year, and of these cardiac defects 20-30 % are due to heart valve abnormalities. Recent literature indicates that the key factors and pathways that regulate valve development are also implicated in congenital heart defects and valve disease. Currently, there are limited options for treatment of valve disease, and therefore having a better understanding of valve development can contribute critical insight into congenital valve defects and disease. There are three major signaling pathways required for early specification and initiation of endothelial-to-mesenchymal transformation (EMT) in the cardiac cushions: BMP, TGF-β, and Notch signaling. BMPs secreted from the myocardium set up the environment for the overlying endocardium to become activated; Notch signaling initiates EMT; and both BMP and TGF-β signaling synergize with Notch to promote the transition of endothelia to mesenchyme and the mesenchymal cell invasiveness. Together, these three essential signaling pathways help form the cardiac cushions and populate them with mesenchyme and, consequently, set off the cascade of events required to develop mature heart valves. Furthermore, integration and cross-talk between these pathways generate highly stratified and delicate valve leaflets and septa of the heart. Here, we discuss BMP, TGF-β, and Notch signaling pathways during mouse cardiac cushion formation and how they together produce a coordinated EMT response in the developing mouse valves.

SMAD7 antagonizes key TGFβ superfamily signaling in mouse granulosa cells in vitro

Transforming growth factor β (TGFβ) superfamily signaling is essential for female reproduction. Dysregulation of the TGFβ signaling pathway can cause reproductive diseases. SMA and MAD (mothers against decapentaplegic) (SMAD) proteins are downstream signaling transducers of the TGFβ superfamily. SMAD7 is an inhibitory SMAD that regulates TGFβ signalingin vitro. However, the function of SMAD7 in the ovary remains poorly defined. To determine the signaling preference and potential role of SMAD7 in the ovary, we herein examined the expression, regulation, and function of SMAD7 in mouse granulosa cells. We showed that SMAD7 was expressed in granulosa cells and subject to regulation by intraovarian growth factors from the TGFβ superfamily. TGFB1 (TGFβ1), bone morphogenetic protein 4, and oocyte-derived growth differentiation factor 9 (GDF9) were capable of inducingSmad7expression, suggesting a modulatory role of SMAD7 in a negative feedback loop. Using a small interfering RNA approach, we further demonstrated that SMAD7 was a negative regulator of TGFB1. Moreover, we revealed a link between SMAD7 and GDF9-mediated oocyte paracrine signaling, an essential component of oocyte–granulosa cell communication and folliculogenesis. Collectively, our results suggest that SMAD7 may function during follicular development via preferentially antagonizing and/or fine-tuning essential TGFβ superfamily signaling, which is involved in the regulation of oocyte–somatic cell interaction and granulosa cell function.