Endothelial expression of bone morphogenetic protein receptor type 1a is required for atrioventricular valve formation

Beyond VICs: Shedding light on the overlooked VECs in calcific aortic valve disease

Calcific aortic valve disease (CAVD) is prevalent in developed nations and has emerged as a pressing global public health concern due to population aging. The precise etiology of this disease remains uncertain, and recent research has primarily focused on examining the role of valvular interstitial cells (VICs) in the development of CAVD. The predominant treatment options currently available involve open surgery and minimally invasive interventional surgery, with no efficacious pharmacological treatment. This article seeks to provide a comprehensive understanding of valvular endothelial cells (VECs) from the aspects of valvular endothelium-derived nitric oxide (NO), valvular endothelial mechanotransduction, valvular endothelial injury, valvular endothelial-mesenchymal transition (EndMT), and valvular neovascularization, which have received less attention, and aims to establish their role and interaction with VICs in CAVD. The ultimate goal is to provide new perspectives for the investigation of non-invasive treatment options for this disease.

Pathophysiology in Brain Arteriovenous Malformations: Focus on Endothelial Dysfunctions and Endothelial-to-Mesenchymal Transition

Brain arteriovenous malformations (bAVMs) substantially increase the risk for intracerebral hemorrhage (ICH), which is associated with significant morbidity and mortality. However, the treatment options for bAVMs are severely limited, primarily relying on invasive methods that carry their own risks for intraoperative hemorrhage or even death. Currently, there are no pharmaceutical agents shown to treat this condition, primarily due to a poor understanding of bAVM pathophysiology. For the last decade, bAVM research has made significant advances, including the identification of novel genetic mutations and relevant signaling in bAVM development. However, bAVM pathophysiology is still largely unclear. Further investigation is required to understand the detailed cellular and molecular mechanisms involved, which will enable the development of safer and more effective treatment options. Endothelial cells (ECs), the cells that line the vascular lumen, are integral to the pathogenesis of bAVMs. Understanding the fundamental role of ECs in pathological conditions is crucial to unraveling bAVM pathophysiology. This review focuses on the current knowledge of bAVM-relevant signaling pathways and dysfunctions in ECs, particularly the endothelial-to-mesenchymal transition (EndMT).

SOX7 deficiency causes ventricular septal defects through its effects on endocardial-to-mesenchymal transition and the expression of Wnt4 and Bmp2

SOX7 is a transcription factor-encoding gene located in a region on chromosome 8p23.1 that is recurrently deleted in individuals with ventricular septal defects (VSDs). We have previously shown that Sox7-/- embryos die of heart failure around E11.5. Here, we demonstrate that these embryos have hypocellular endocardial cushions with severely reduced numbers of mesenchymal cells. Ablation of Sox7 in the endocardium also resulted in hypocellular endocardial cushions, and we observed VSDs in rare E15.5 Sox7flox/-;Tie2-Cre and Sox7flox/flox;Tie2-Cre embryos that survived to E15.5. In atrioventricular explant studies, we showed that SOX7 deficiency leads to a severe reduction in endocardial-to-mesenchymal transition (EndMT). RNA-seq studies performed on E9.5 Sox7-/- heart tubes revealed severely reduced Wnt4 transcript levels. Wnt4 is expressed in the endocardium and promotes EndMT by acting in a paracrine manner to increase the expression of Bmp2 in the myocardium. Both WNT4 and BMP2 have been previously implicated in the development of VSDs in individuals with 46,XX sex reversal with dysgenesis of kidney, adrenals and lungs (SERKAL) syndrome and in individuals with short stature, facial dysmorphism and skeletal anomalies with or without cardiac anomalies 1 (SSFSC1) syndrome, respectively. We now show that Sox7 and Wnt4 interact genetically in the development of VSDs through their additive effects on endocardial cushion development with Sox7+/-;Wnt4+/- double heterozygous embryos having hypocellular endocardial cushions and perimembranous and muscular VSDs not seen in their Sox7+/- and Wnt4+/- littermates. These results provide additional evidence that SOX7, WNT4 and BMP2 function in the same pathway during mammalian septal development and that their deficiency can contribute to the development of VSDs in humans.

Emerging roles of inflammation-mediated endothelial–mesenchymal transition in health and disease

Endothelial–mesenchymal transition (EndoMT), a cellular differentiation process in which endothelial cells (ECs) lose their properties and differentiate into mesenchymal cells, has been observed not only during development but also in various pathological states in adults, including cancer progression and organ/tissue fibrosis. Transforming growth factor-β (TGF-β), an inflammation-related cytokine, has been shown to play central roles in the induction of EndoMT. TGF-β induces EndoMT by regulating the expression of various transcription factors, signaling molecules, and cellular components that confer ECs with mesenchymal characteristics. However, TGF-β by itself is not necessarily sufficient to induce EndoMT to promote the progression of EndoMT-related diseases to a refractory extent. In addition to TGF-β, additional activation by other inflammatory factors is often required to stabilize the progression of EndoMT. Since recent lines of evidence indicate that inflammatory signaling molecules act as enhancers of EndoMT, we summarize the roles of inflammatory factors in the induction of EndoMT and related diseases. We hope that this review will help to develop therapeutic strategies for EndoMT-related diseases by targeting inflammation-mediated EndoMT.

Endothelial to Mesenchymal Transition in the Cardiogenesis and Cardiovascular Diseases

Today, cardiovascular diseases remain a leading cause of morbidity and mortality worldwide. Endothelial to mesenchymal transition (EndMT) does not only play a major role in the course of development but also contributes to several cardiovascular diseases in adulthood. EndMT is characterized by down-regulation of the endothelial proteins and highly up-regulated fibrotic specific genes and extracellular matrix-forming proteins. EndMT is also a transforming growth factor-β-driven (TGF-β) process in which endothelial cells lose their endothelial characteristics and acquire a mesenchymal phenotype with expression of α-smooth muscle actin (α-SMA), fibroblast-specific protein 1, etc. EndMT is a vital process during cardiac development, thus disrupted EndMT gives rise to the congenital heart diseases, namely septal defects and valve abnormalities. In this review, we have discussed the main signaling pathways and mechanisms participating in the process of EndMT such as TGF-β and Bone morphogenetic protein (BMP), Wnt^#, and Notch signaling pathway and also studied the role of EndMT in physiological cardiovascular development and pathological conditions including myocardial infarction, pulmonary arterial hypertension, congenital heart defects, cardiac fibrosis, and atherosclerosis. As a perspective view, having a clear understanding of involving cellular and molecular mechanisms in EndMT and conducting Randomized controlled trials (RCTs) with a large number of samples for involving pharmacological agents may guide us into novel therapeutic approaches of congenital disorders and heart diseases.

TGF-β-Induced Endothelial to Mesenchymal Transition in Disease and Tissue Engineering

Endothelial to mesenchymal transition (EndMT) is a complex biological process that gives rise to cells with multipotent potential. EndMT is essential for the formation of the cardiovascular system during embryonic development. Emerging results link EndMT to the postnatal onset and progression of fibrotic diseases and cancer. Moreover, recent reports have emphasized the potential for EndMT in tissue engineering and regenerative applications by regulating the differentiation status of cells. Transforming growth factor β (TGF-β) engages in many important physiological processes and is a potent inducer of EndMT. In this review, we first summarize the mechanisms of the TGF-β signaling pathway as it relates to EndMT. Thereafter, we discuss the pivotal role of TGF-β-induced EndMT in the development of cardiovascular diseases, fibrosis, and cancer, as well as the potential application of TGF-β-induced EndMT in tissue engineering.

A Computational Model of the Endothelial to Mesenchymal Transition

Endothelial cells (ECs) form the lining of lymph and blood vessels. Changes in tissue requirements or wounds may cause ECs to behave as tip or stalk cells. Alternatively, they may differentiate into mesenchymal cells (MCs). These processes are known as EC activation and endothelial-to-mesenchymal transition (EndMT), respectively. EndMT, Tip, and Stalk EC behaviors all require SNAI1, SNAI2, and Matrix metallopeptidase (MMP) function. However, only EndMT inhibits the expression of VE-cadherin, PECAM1, and VEGFR2, and also leads to EC detachment. Physiologically, EndMT is involved in heart valve development, while a defective EndMT regulation is involved in the physiopathology of cardiovascular malformations, congenital heart disease, systemic and organ fibrosis, pulmonary arterial hypertension, and atherosclerosis. Therefore, the control of EndMT has many promising potential applications in regenerative medicine. Despite the fact that many molecular components involved in EC activation and EndMT have been characterized, the system-level molecular mechanisms involved in this process have not been elucidated. Toward this end, hereby we present Boolean network model of the molecular involved in the regulation of EC activation and EndMT. The simulated dynamic behavior of our model reaches fixed and cyclic patterns of activation that correspond to the expected EC and MC cell types and behaviors, recovering most of the specific effects of simple gain and loss-of-function mutations as well as the conditions associated with the progression of several diseases. Therefore, our model constitutes a theoretical framework that can be used to generate hypotheses and guide experimental inquiry to comprehend the regulatory mechanisms behind EndMT. Our main findings include that both the extracellular microevironment and the pattern of molecular activity within the cell regulate EndMT. EndMT requires a lack of VEGFA and sufficient oxygen in the extracellular microenvironment as well as no FLI1 and GATA2 activity within the cell. Additionally Tip cells cannot undergo EndMT directly. Furthermore, the specific conditions that are sufficient to trigger EndMT depend on the specific pattern of molecular activation within the cell.

Homozygous missense variant in BMPR1A resulting in BMPR signaling disruption and syndromic features

Background

The bone morphogenetic protein (BMP) pathway is known to play an imperative role in bone, cartilage, and cardiac tissue formation. Truncating, heterozygous variants, and deletions of one of the essential receptors in this pathway, Bone Morphogenetic Protein Receptor Type1A (BMPR1A), have been associated with autosomal dominant juvenile polyposis. Heterozygous deletions have also been associated with cardiac and minor skeletal anomalies. Populations with atrioventricular septal defects are enriched for rare missense BMPR1A variants.

Methods

We report on a patient with a homozygous missense variant in BMPR1A causing skeletal abnormalities, growth failure a large atrial septal defect, severe subglottic stenosis, laryngomalacia, facial dysmorphisms, and developmental delays.

Results

Functional analysis of this variant shows increased chondrocyte death for cells with the mutated receptor, increased phosphorylated R‐Smads1/5/8, and loss of Sox9 expression mediated by decreased phosphorylation of p38.

Conclusion

This homozygous missense variant in BMPR1A appears to cause a distinct clinical phenotype.

Inhibitor of DNA binding in heart development and cardiovascular diseases

Id proteins, inhibitors of DNA binding, are transcription regulators containing a highly conserved helix-loop-helix domain. During multiple stages of normal cardiogenesis, Id proteins play major roles in early development and participate in the differentiation and proliferation of cardiac progenitor cells and mature cardiomyocytes. The fact that a depletion of Ids can cause a variety of defects in cardiac structure and conduction function is further evidence of their involvement in heart development. Multiple signalling pathways and growth factors are involved in the regulation of Ids in a cell- and tissue- specific manner to affect heart development. Recent studies have demonstrated that Ids are related to multiple aspects of cardiovascular diseases, including congenital structural, coronary heart disease, and arrhythmia. Although a growing body of research has elucidated the important role of Ids, no comprehensive review has previously compiled these scattered findings. Here, we introduce and summarize the roles of Id proteins in heart development, with the hope that this overview of key findings might shed light on the molecular basis of consequential cardiovascular diseases. Furthermore, we described the future prospective researches needed to enable advancement in the maintainance of the proliferative capacity of cardiomyocytes. Additionally, research focusing on increasing embryonic stem cell culture adaptability will help to improve the future therapeutic application of cardiac regeneration.

Endothelial to Mesenchymal Transition: Role in Physiology and in the Pathogenesis of Human Diseases

Numerous studies have demonstrated that endothelial cells are capable of undergoing endothelial to mesenchymal transition (EndMT), a newly recognized type of cellular transdifferentiation. EndMT is a complex biological process in which endothelial cells adopt a mesenchymal phenotype displaying typical mesenchymal cell morphology and functions, including the acquisition of cellular motility and contractile properties. Endothelial cells undergoing EndMT lose the expression of endothelial cell-specific proteins such as CD31/platelet-endothelial cell adhesion molecule, von Willebrand factor, and vascular-endothelial cadherin and initiate the expression of mesenchymal cell-specific genes and the production of their encoded proteins including α-smooth muscle actin, extra domain A fibronectin, N-cadherin, vimentin, fibroblast specific protein-1, also known as S100A4 protein, and fibrillar type I and type III collagens. Transforming growth factor-β1 is considered the main EndMT inducer. However, EndMT involves numerous molecular and signaling pathways that are triggered and modulated by multiple and often redundant mechanisms depending on the specific cellular context and on the physiological or pathological status of the cells. EndMT participates in highly important embryonic development processes, as well as in the pathogenesis of numerous genetically determined and acquired human diseases including malignant, vascular, inflammatory, and fibrotic disorders. Despite intensive investigation, many aspects of EndMT remain to be elucidated. The identification of molecules and regulatory pathways involved in EndMT and the discovery of specific EndMT inhibitors should provide novel therapeutic approaches for various human disorders mediated by EndMT.

TGF-β-Induced Endothelial-Mesenchymal Transition in Fibrotic Diseases

Fibrotic diseases are characterized by net accumulation of extracellular matrix proteins in affected organs leading to their dysfunction and ultimate failure. Myofibroblasts have been identified as the cells responsible for the progression of the fibrotic process, and they originate from several sources, including quiescent tissue fibroblasts, circulating CD34⁺ fibrocytes and the phenotypic conversion of various cell types into activated myofibroblasts. Several studies have demonstrated that endothelial cells can transdifferentiate into mesenchymal cells through a process termed endothelial- mesenchymal transition (EndMT) and that this can give rise to activated myofibroblasts involved in the development of fibrotic diseases. Transforming growth factor β (TGF-β) has a central role in fibrogenesis by modulating the fibroblast phenotype and function, inducing myofibroblast transdifferentiation and promoting matrix accumulation. In addition, TGF-β by inducing EndMT may further contribute to the development of fibrosis. Despite extensive investigation of the pathogenesis of fibrotic diseases, no effective treatment strategies are available. Delineation of the mechanisms responsible for initiation and progression of fibrotic diseases is crucial for the development of therapeutic strategies for the treatment of the disease. In this review, we summarize the role of the TGF-β signaling pathway and EndMT in the development of fibrotic diseases and discuss their therapeutic potential.

Endothelial to mesenchymal transition in the cardiovascular system

Endothelial to mesenchymal transition (EndMT) is a special type of epithelial to mesenchymal transition. It is a process that is characterized by the loss of features of endothelial cells and acquisition of specific markers of mesenchymal cells. A variety of stimuli, such as inflammation, growth factors, and hypoxia, regulate EndMT through various signaling pathways and intracellular transcription factors. It has been demonstrated that epigenetic modifications are also involved in this process. Recent studies have identified the essential role of EndMT in the cardiovascular system. EndMT contributes to steps in cardiovascular development, such as cardiac valve formation and septation, as well as the pathogenesis of various cardiovascular disorders, such as congenital heart disease, myocardial fibrosis, myocardial infarction and pulmonary arterial hypertension. Thus, comprehensive understanding of the underlying mechanisms of EndMT will provide novel therapeutic strategies to overcome congenital heart disease due to abnormal development and other cardiovascular diseases. This review will focus on summarizing the currently understood signaling pathways and epigenetic modifications involved in the regulation of EndMT and the role of EndMT in pathophysiological conditions of the cardiovascular system.

Endothelial-to-mesenchymal transition: A novel therapeutic target for cardiovascular diseases

Endothelial-to-mesenchymal transition (EndMT) is a complex biological process in which endothelial cells lose their specific markers and acquire a mesenchymal or myofibroblastic phenotype. Similar to epithelial-to-mesenchymal transition (EMT), EndMT can be induced by multiple stimulants such as cytokines and metabolic factors that play crucial roles in the development of the cardiovascular system. Recent studies have demonstrated that EndMT may play a significant role in the pathogenesis of cardiovascular diseases (CVDs), and may represent a novel therapeutic target for cardiovascular remodeling and fibrotic disorders. The exact molecular mechanisms involved in cardiovascular pathogenesis that occur as a result of EndMT, however, are not fully explained. In this review, we reveal the multiple intercellular mechanisms of EndMT including stimulants, signaling pathways, and seek to explore the relationship between this biological process, cardiovascular system development, and CVDs that may lead to new therapeutic strategies for the treatment of CVDs.

Exome sequencing identifies rare variants in multiple genes in atrioventricular septal defect

Purpose

The genetic etiology of atrioventricular septal defect (AVSD) is unknown in 40% cases. Conventional sequencing and arrays have identified the etiology in only a minority of non-syndromic individuals with AVSD.

Methods

Whole exome sequencing was performed in 81 unrelated probands with AVSD to identify potentially causal variants in a comprehensive set of 112 genes with strong biological relevance to AVSD.

Results

A significant enrichment of rare and rare/damaging variants was identified in the gene set, compared with controls (odds ratio 1.52, 95% confidence interval 1.35–1.71, p = 4.8 x 10^-11). The enrichment was specific to AVSD probands compared with a non-AVSD cohort with tetralogy of Fallot (odds ratio 2.25, 95% confidence interval 1.84-2.76, p = 2.2 x 10^-16). Six genes (NIPBL, CHD7, CEP152, BMPR1a, ZFPM2 and MDM4) were enriched for rare variants in AVSD compared to controls, including three syndrome-associated genes (NIPBL, CHD7, CEP152). The findings were confirmed in a replication cohort of 81 AVSD probands.

Conclusion

Mutations in genes with strong biological relevance to AVSD, including syndrome-associated genes, can contribute to AVSD even in those with isolated heart disease. The identification of a gene set associated with AVSD will facilitate targeted genetic screening in this cohort.

Id proteins regulate capillary repair and perivascular cell proliferation following ischemia-reperfusion injury

Acute kidney injury (AKI) results in microvascular damage that if not normally repaired, may lead to fibrosis. The Id1 and 3 proteins have a critical role in promoting angiogenesis during development, tumor growth and wound repair by functioning as dominant negative regulators of bHLH transcription factors. The goal of this study was to determine if Id proteins regulate microvascular repair and remodeling and if increased Id1 expression results in decreased capillary loss following AKI. The effect of changes in Id expression in vivo was examined using Id1−/−, Id3RFP/+ (Id1/Id3 KO) and Tek (Tie2)-rtTA, TRE-lacz/TRE Id1 (TRE Id1) mice with doxycycline inducible endothelial Id1 and β-galactosidase expression. Id1 and 3 were co-localized in endothelial cells in normal adult kidneys and protein levels were increased at day 3 following ischemia-reperfusion injury (IRI) and contralateral nephrectomy. Id1/Id3 KO mice had decreased baseline capillary density and pericyte coverage and increased tubular damage following IRI but decreased interstitial cell proliferation and fibrosis compared with WT littermates. No compensatory increase in kidney size occurred in KO mice resulting in increased creatinine compared with WT and TRE Id1 mice. TRE Id1 mice had no capillary rarefaction within 1 week following IRI in comparison with WT littermates. TRE Id1 mice had increased proliferation of PDGFRβ positive interstitial cells and medullary collagen deposition and developed capillary rarefaction and albuminuria at later time points. These differences were associated with increased Angiopoietin 1 (Ang1) and decreased Ang2 expression in TRE Id1 mice. Examination of gene expression in microvascular cells isolated from WT, Id1/Id3 KO and TRE Id1 mice showed increased Ang1 and αSMA in Id1 overexpressing cells and decreased pericyte markers in cells from KO mice. These results suggest that increased Id levels following AKI result in microvascular remodeling associated with increased fibrosis.

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.

Roles of TGF-β signals in endothelial-mesenchymal transition during cardiac fibrosis

Most cardiac diseases caused by inflammation are associated with fibrosis in the heart. Fibrosis is characterized by the accumulation of fibroblasts and excess deposition of extracellular matrix (ECM), which results in the distorted organ architecture and function. Recent studies revealed that cardiac fibroblasts are heterogeneous with multiple origins. Endothelial-mesenchymal transition (EndMT) plays important roles in the formation of cardiac fibroblasts during pathological settings. EndMT is regulated by signaling pathways mediated by cytokines including transforming growth factor (TGF)-β. Better understanding of the mechanisms of the formation of cardiac fibroblasts via EndMT may provide an opportunity to develop therapeutic strategies to cure heart diseases.

Mechanisms of bone morphogenetic protein 2 (BMP2) stimulated inhibitor of DNA binding 3 (Id3) transcription

Bone morphogenetic protein 2 (BMP2) stimulates expression of the inhibitors of DNA binding (Id) 1, 2, and 3 in a variety of cell types. Here, we examined mechanisms mediating BMP2-stimulated Id3 transcription in murine gonadotropes. Using a combination of quantitative RT-PCR, promoter-reporter analyses, over-expression, and RNA interference approaches, we demonstrate that BMP2 signals via the BMPR2 and BMPR1A (ALK3) receptors and intracellular signaling proteins SMADs 1 and 5 to stimulate Id3 transcription. We further define a novel 6-bp cis-element mediating BMP2- and SMAD-dependent transcription, though this site does not appear to bind SMADs directly. A specific DNA binding protein complex binds to this element, but its constituent protein(s) remain undetermined. Recently, a more distal enhancer was shown to mediate BMP4-induction of the human ID3 gene in ovarian cancer cells. This enhancer is conserved in the murine gene and we demonstrate its role in BMP2-induced Id3 promoter activity in gonadotropes. Conversely, the proximal cis-element defined here is also conserved in human ID3 and we demonstrate its functional role in BMP2-induction of ID3 transcription. Finally, we show that the two regulatory elements also mediate BMP2-induction of Id3 promoter activity in murine fibroblasts. Collectively, we have defined a general mechanism whereby BMP2 regulates Id3/ID3 transcription in different cell types and in different species.

Bone Morphogenic Protein-4 Impairs Endothelial Function Through Oxidative Stress–Dependent Cyclooxygenase-2 Upregulation

Rationale:

Bone morphogenic protein (BMP)4 can stimulate superoxide production and exert proinflammatory effects on the endothelium. The underlying mechanisms of how BMP4 mediates endothelial dysfunction and hypertension remain elusive.

Objective:

To elucidate the cellular pathways by which BMP4-induced endothelial dysfunction is mediated through oxidative stress–dependent upregulation of cyclooxygenase (COX)-2.

Methods and Results:

Impaired endothelium-dependent relaxations, exaggerated endothelium-dependent contractions, and reactive oxygen species (ROS) production were observed in BMP4-treated mouse aortae, which were prevented by the BMP4 antagonist noggin. Pharmacological inhibition with thromboxane prostanoid receptor antagonist or COX-2 but not COX-1 inhibitor prevented BMP4-induced endothelial dysfunction, which was further confirmed with the use of COX-1 −/− or COX-2 −/− mice. Noggin and knockdown of BMP receptor 1A abolished endothelium-dependent contractions and COX-2 upregulation in BMP4-treated aortae. Apocynin and tempol treatment were effective in restoring endothelium-dependent relaxations, preventing endothelium-dependent contractions and eliminating ROS overproduction and COX-2 overexpression in BMP4-treated aortae. BMP4 increased p38 mitogen-activated protein kinase (MAPK) activity through a ROS-sensitive mechanism and p38 MAPK inhibitor prevented BMP4-induced endothelial dysfunction. COX-2 inhibition blocked the effect of BMP4 without affecting BMP4-induced ROS overproduction and COX-2 upregulation. Importantly, renal arteries from hypertensive rats and humans showed higher levels of COX-2 and BMP4 accompanied by endothelial dysfunction.

Conclusions:

We show for the first time that ROS serve as a pathological link between BMP4 stimulation and the downstream COX-2 upregulation in endothelial cells, leading to endothelial dysfunction through ROS-dependent p38 MAPK activation. This BMP4/ROS/COX-2 cascade is important in the maintenance of endothelial dysfunction in hypertension.

BMP and BMP receptor expression during murine organogenesis

Cell-cell communication is critical for regulating embryonic organ growth and differentiation. The Bone Morphogenetic Protein (BMP) family of transforming growth factor beta (TGFbeta) molecules represents one class of such cell-cell signaling molecules that regulate the morphogenesis of several organs. Due to high redundancy between the myriad BMP ligands and receptors in certain tissues, it has been challenging to address the role of BMP signaling using targeting of single Bmp genes in mouse models. Here, we present a detailed study of the developmental expression profiles of three BMP ligands (Bmp2, Bmp4, Bmp7) and three BMP receptors (Bmpr1a, Bmpr1b, and BmprII), as well as their molecular antagonist (noggin), in the early embryo during the initial steps of murine organogenesis. In particular, we focus on the expression of Bmp family members in the first organs and tissues that take shape during embryogenesis, such as the heart, vascular system, lungs, liver, stomach, nervous system, somites and limbs. Using in situ hybridization, we identify domains where ligand(s) and receptor(s) are either singly or co-expressed in specific tissues. In addition, we identify a previously unnoticed asymmetric expression of Bmp4 in the gut mesogastrium, which initiates just prior to gut turning and the establishment of organ asymmetry in the gastrointestinal tract. Our studies will aid in the future design and/or interpretation of targeted deletion of individual Bmp or Bmpr genes, since this study identifies organs and tissues where redundant BMP signaling pathways are likely to occur.