Defects in aortic fusion and craniofacial vasculature in the holoprosencephalic mouse embryo under inhibition of sonic hedgehog signaling

The effect of gestational diabetes on identification of key genes and pathways in human umbilical vein endothelial cell by integrated bioinformatics analysis

Maternal diabetes may lead to long-term risks for the offspring. The study aims at identifying the potential crucial genes and pathways associated with foetal metabolism and malformation of gestational diabetes mellitus (GDM). Gene Expression Series 49524 and 87295 were downloaded from Gene Expression Omnibus database, including eight from GDM and eight from non-GDM. A total of 35 differentially expressed genes were identified. Gene ontology functional annotation and signalling pathway analyses were performed. Four hub genes were identified by protein-protein interaction network: SHH, E2F1, STAT1, and HOXA9. The four hub genes were assessed by western blot and real-time quantitative PCR in clinical samples. The results of this data mining and integration help to reveal the pathophysiologic and molecular mechanism imprinted in primary umbilical cord-derived cells from GDM offspring. These genes and pathways identified are potential stratification biomarkers and provide further insight for developing therapeutic intervention for the offspring of diabetic mothers.Impact statementWhat is already known on this subject? Maternal diabetes may lead to long-term risks for the offspring. A high glucose environment might change the umbilical cord expression of genes implicated in foetal metabolism and development. However, underlying molecular mechanisms have not been investigated thoroughly.What do the results of this study add? GO functional annotation showed that the biological functions of differentially expressed genes mainly involved in metanephros development, salivary gland morphogenesis, fat cell differentiation, vasculogenesis, muscle cell proliferation, heart morphogenesis and Wnt signalling pathway. Signalling pathway analyses found that these differentially expressed genes mainly implicated in the apoptosis, cell cycle, Hedgehog, P53, and NOTCH signalling pathway. Four hub genes were identified by protein-protein interaction network: SHH, E2F1, STAT1 and HOXA9.What are the implications of these findings for clinical practice and/or further research? The genes and pathways identified in the present study are potential stratification biomarkers and provide further insight for developing therapeutic intervention for the offspring of diabetic mothers.

Role of Hedgehog Signaling in Vasculature Development, Differentiation, and Maintenance

The role of Hedgehog (Hh) signaling in vascular biology has first been highlighted in embryos by Pepicelli et al. in 1998 and Rowitch et al. in 1999. Since then, the proangiogenic role of the Hh ligands has been confirmed in adults, especially under pathologic conditions. More recently, the Hh signaling has been proposed to improve vascular integrity especially at the blood–brain barrier (BBB). However, molecular and cellular mechanisms underlying the role of the Hh signaling in vascular biology remain poorly understood and conflicting results have been reported. As a matter of fact, in several settings, it is currently not clear whether Hh ligands promote vessel integrity and quiescence or destabilize vessels to promote angiogenesis. The present review relates the current knowledge regarding the role of the Hh signaling in vasculature development, maturation and maintenance, discusses the underlying proposed mechanisms and highlights controversial data which may serve as a guideline for future research. Most importantly, fully understanding such mechanisms is critical for the development of safe and efficient therapies to target the Hh signaling in both cancer and cardiovascular/cerebrovascular diseases.

Dl-3-N-butylphthalide promotes angiogenesis and upregulates sonic hedgehog expression after cerebral ischemia in rats

INTRODUCTION

Dl-3-N-butylphthalide (NBP), a small molecule drug used clinically in the acute phase of ischemic stroke, has been shown to improve functional recovery and promote angiogenesis and collateral vessel circulation after experimental cerebral ischemia. However, the underlying molecular mechanism is unknown.

AIMS

To explore the potential molecular mechanism of angiogenesis induced by NBP after cerebral ischemia.

RESULTS

NBP treatment attenuated body weight loss, reduced brain infarct volume, and improved neurobehavioral outcomes during focal ischemia compared to the control rats (P < 0.05). NBP increased the number of CD31⁺ microvessels, the number of CD31⁺ /BrdU⁺ proliferating endothelial cells, and the functional vascular density (P < 0.05). Further study demonstrated that NBP also promoted the expression of vascular endothelial growth factor and angiopoietin-1 (P < 0.05), which was accompanied by upregulated sonic hedgehog expression in astrocytes in vivo and in vitro.

CONCLUSION

NBP treatment promoted the expression of vascular endothelial growth factor and angiopoietin-1, induced angiogenesis, and improved neurobehavioral recovery. These effects were associated with increased sonic hedgehog expression after NBP treatment. Our results broadened the clinical application of NBP to include the later phase of ischemia.

"Twig-like" cerebral vessels are not pathognomonic for ACTA A2 mutations: A case report

ACTA2 mutations are recently described genetically defined abnormalities of blood vessels in various organs of the body with specific abnormalities in cerebral vessels in the form of straightening of all cerebral arteries ("twig-like" pattern), stenosis/occlusions, proximal dilatation, and absent "moyamoya" type of collaterals. We describe a one-and-a half year-old girl child who presented with mild motor developmental delay and on neuroimaging showed septo-preoptic holoprosencephaly, diffuse radial polymicrogyria, and pontine hypoplasia along with magnetic resonance angiographic features suggestive of ACTA2 mutation type of cerebral vessels. However, genetic studies revealed no evidence of ACTA2 mutation, indicating that the "twig-like" pattern may not only be a pathognomonic feature of ACTA2 mutations.

Flow-induced protein kinase A-CREB pathway acts via BMP signaling to promote HSC emergence

Kim et al. identify a novel shear stress–induced pathway involving protein kinase A, CREB, and bone morphogenetic protein that regulates hematopoietic stem cell generation in the embryonic aorta.

Fluid shear stress promotes the emergence of hematopoietic stem cells (HSCs) in the aorta–gonad–mesonephros (AGM) of the developing mouse embryo. We determined that the AGM is enriched for expression of targets of protein kinase A (PKA)–cAMP response element-binding protein (CREB), a pathway activated by fluid shear stress. By analyzing CREB genomic occupancy from chromatin-immunoprecipitation sequencing (ChIP-seq) data, we identified the bone morphogenetic protein (BMP) pathway as a potential regulator of CREB. By chemical modulation of the PKA–CREB and BMP pathways in isolated AGM VE-cadherin⁺ cells from mid-gestation embryos, we demonstrate that PKA–CREB regulates hematopoietic engraftment and clonogenicity of hematopoietic progenitors, and is dependent on secreted BMP ligands through the type I BMP receptor. Finally, we observed blunting of this signaling axis using Ncx1-null embryos, which lack a heartbeat and intravascular flow. Collectively, we have identified a novel PKA–CREB–BMP signaling pathway downstream of shear stress that regulates HSC emergence in the AGM via the endothelial-to-hematopoietic transition.

Dorsal aorta formation: separate origins, lateral-to-medial migration, and remodeling

Blood vessel formation is a highly dynamic tissue-remodeling event that can be observed from early development in vertebrate embryos. Dorsal aortae, the first functional intra-embryonic blood vessels, arise as two separate bilateral vessels in the trunk and undergo lateral-to-medial translocation, eventually fusing into a single large vessel at the midline. After this dramatic remodeling, the dorsal aorta generates hematopoietic stem cells. The dorsal aorta is a good model to use to increase our understanding of the mechanisms controlling the establishment and remodeling of larger blood vessels in vivo. Because of the easy accessibility to the developing circulatory system, quail and chick embryos have been widely used for studies on blood vessel formation. In particular, the mapping of endothelial cell origins has been performed using quail-chick chimera analysis, revealing endothelial, vascular smooth muscle, and hematopoietic cell progenitors of the dorsal aorta. The avian embryo model also allows conditional gene activation/inactivation and direct observation of cell behaviors during dorsal aorta formation. This allows a better understanding of the molecular mechanisms underlying specific morphogenetic events during dynamic dorsal aorta formation from a cell behavior perspective.

Sonic Hedgehog-mediated synergistic effects guiding angiogenesis and osteogenesis

Sonic hedgehog (Shh) is a morphogen controlling the skeletal and vascular development in the embryo but is also reactivated during adult repair processes. Thus, this molecule holds great therapeutic potential for biotechnological and biomedical approaches aiming to enhance tissue regeneration or to replace damaged tissues. According to present knowledge, Shh signaling controls the expression of several families of growth factors involved in neovascularization and vessel maturation and acts upstream of the most prominent angiogenic growth factor, vascular endothelial growth factor. In this context, a very interesting feature of Shh is that it controls both angiogenic activity and vessel stabilization by mural cells. In parallel, Shh seems to have a direct effect on endothelial cell tube formation and seems to trigger the differentiation process of mesenchymal stem cells toward the osteogenic lineage. In this chapter, we will therefore shortly summarize the multifaceted potential of Shh for bone repair and vascularization according to the current literature. In addition, we will show how coculture models based on outgrowth endothelial cells and primary osteoblasts can be used to reveal some of the relevant mechanisms by which Shh drives and connects bone regeneration and vascularization.

An anteroposterior wave of vascular inhibitor downregulation signals aortae fusion along the embryonic midline axis

Paracrine signals, both positive and negative, regulate the positioning and remodeling of embryonic blood vessels. In the embryos of mammals and birds, the first major remodeling event is the fusion of bilateral dorsal aortae at the midline to form the dorsal aorta. Although the original bilaterality of the dorsal aortae occurs as the result of inhibitory factors (antagonists of BMP signaling) secreted from the midline by the notochord, it is unknown how fusion is later signaled. Here, we report that dorsal aortae fusion is tightly regulated by a change in signaling by the notochord along the anteroposterior axis. During aortae fusion, the notochord ceases to exert its negative influence on vessel formation. This is achieved by a transcriptional downregulation of negative regulators while positive regulators are maintained at pre-fusion levels. In particular, Chordin, the most abundant BMP antagonist expressed in the notochord prior to fusion, undergoes a dramatic downregulation in an anterior to posterior wave. With inhibitory signals diminished and sustained expression of the positive factors SHH and VEGF at the midline, fusion of the dorsal aortae is signaled. These results demonstrate a novel mechanism by which major modifications of the vascular pattern can occur through modulation of vascular inhibitors without changes in the levels of positive vascular regulators.

Sonic hedgehog promotes angiogenesis and osteogenesis in a coculture system consisting of primary osteoblasts and outgrowth endothelial cells

A number of previous studies documented the angiogenic potential of outgrowth endothelial cells in vitro and in vivo and provided evidence that therapeutic success could depend on coculture or coimplantation strategies. Thus, deeper insight into the molecular mechanisms underlying this pro-angiogenic effect of cocultures might provide new translational options for tissue engineering and regenerative medicine. One promising signaling pathway in bone repair involved in neoangiogenesis and bone formation is the sonic hedgehog (Shh) pathway. In this article, we focus on the effect of Shh on the formation of microvessel-like structures and osteoblastic differentiation in cocultures of primary osteoblasts and outgrowth endothelial cells. Already after 24 h of treatment, Shh leads to a massive increase in microvessel-like structures compared with untreated cocultures. Increased formation of angiogenic structures seems to correlate with the upregulation of vascular endothelial growth factor or angiopoietins (Ang-1 and Ang-2) studied at both the mRNA and protein levels. In addition, treatment with cyclopamine, an inhibitor of hedgehog signaling, blocked the formation of microvessel-like structures in the cocultures. However, exogenous Shh also resulted in the upregulation of several osteogenic differentiation markers in real-time polymerase chain reaction, as well as in an increased mineralization and alkaline phosphatase activity. The present data highlight the central role of the Shh pathway in bone regeneration and vascularization. Further, Shh might have the potential to improve both angiogenesis and osteogenesis in clinical applications in the future.

Paracrine Hedgehog signaling in stomach and intestine: new roles for hedgehog in gastrointestinal patterning

BACKGROUND & AIMS

Hedgehog signaling is critical in gastrointestinal patterning. Mice deficient in Hedgehog signaling exhibit abnormalities that mirror deformities seen in the human VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, limb) association. However, the direction of Hedgehog signal flow is controversial and the cellular targets of Hedgehog signaling change with time during development. We profiled cellular Hedgehog response patterns from embryonic day 10.5 (E10.5) to adult in murine antrum, pyloric region, small intestine, and colon.

METHODS

Hedgehog signaling was profiled using Hedgehog pathway reporter mice and in situ hybridization. Cellular targets were identified by immunostaining. Ihh-overexpressing transgenic animals were generated and analyzed.

RESULTS

Hedgehog signaling is strictly paracrine from antrum to colon throughout embryonic and adult life. Novel findings include the following: mesothelial cells of the serosa transduce Hedgehog signals in fetal life; the hindgut epithelium expresses Ptch but not Gli1 at E10.5; the 2 layers of the muscularis externa respond differently to Hedgehog signals; organogenesis of the pyloric sphincter is associated with robust Hedgehog signaling; dramatically different Hedgehog responses characterize stomach and intestine at E16; and after birth, the muscularis mucosa and villus smooth muscle consist primarily of Hedgehog-responsive cells and Hh levels actively modulate villus core smooth muscle.

CONCLUSIONS

These studies reveal a previously unrecognized association of paracrine Hedgehog signaling with several gastrointestinal patterning events involving the serosa, pylorus, and villus smooth muscle. The results may have implications for several human anomalies and could potentially expand the spectrum of the human VACTERL association.

Cross talk between hedgehog and bone morphogenetic proteins occurs during cardiomyogenesis in P19 cells

Hedgehog (Hh) signaling plays a role in heart morphogenesis and can initiate cardiomyogenesis in P19 cells. To determine if Hh signaling is essential for P19 cell cardiomyogenesis, we determined which Hh factors are expressed and the effect of Hh signal transduction inhibitors. Here, we find that the Hh gene family and their downstream mediators are expressed during cardiomyogenesis but an active Hh signaling pathway is not essential. However, loss of Hh signaling resulted in a delay of BMP-4, GATA-4, Gli2, and Meox1 expression during cardiomyogenesis. By using Noggin-overexpressing P19 cells, we determined that Hh signaling was not active during Noggin-mediated inhibition of cardiomyogenesis. Thus, there is cross talk between the Hh and BMP signaling pathways and the Hh pathway appears important for timely cardiomyogenesis.

Sonic hedgehog is required for the assembly and remodeling of branchial arch blood vessels

Sonic hedgehog (Shh) is a morphogen involved in many developmental processes. Injection of cells (5E1) that produce a Shh-blocking antibody causes an attenuation of the Shh response, and this causes vascular malformations and impaired remodeling characterized by hemorrhages and protrusions of the anterior cardinal vein and outflow tract, delayed fusion of the dorsal aortae, impaired branching of the internal carotid artery, and delayed remodeling of the aortic arches. Distribution of smooth muscle cells in the vessel wall is unchanged. In 5E1-injected embryos, we also observed impaired assembly of endothelial cells into vascular tubes, particularly in the sixth branchial arch, around the anterior cardinal vein and around the dorsal aorta. In 5E1-treated embryos, increased numbers of macrophage-like cells, apoptotic cells, and a decreased level of proliferation were observed in head mesenchyme. Together, these observations show that Shh signaling is required at multiple stages for proper vessel formation and remodeling.

Decreased cardiac glutathione peroxidase levels and enhanced mandibular apoptosis in malformed embryos of diabetic rats

OBJECTIVE

To characterize normal and malformed embryos within the same litters from control and diabetic rats for expression of genes related to metabolism of reactive oxygen species (ROS) or glucose as well as developmental genes.

RESEARCH DESIGN AND METHODS

Embryos from nondiabetic and streptozotocin-induced diabetic rats were collected on gestational day 11 and evaluated for gene expression (PCR) and distribution of activated caspase-3 and glutathione peroxidase (Gpx)-1 by immunohistochemistry.

RESULTS

Maternal diabetes (MD group) caused growth retardation and an increased malformation rate in the embryos of MD group rats compared with those of controls (N group). We found decreased gene expression of Gpx-1 and increased expression of vascular endothelial growth factor-A (Vegf-A) in malformed embryos of diabetic rats (MDm group) compared with nonmalformed littermates (MDn group). Alterations of messenger RNA levels of other genes were similar in MDm and MDn embryos. Thus, expression of copper zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD), and sonic hedgehog homolog (Shh) were decreased, and bone morphogenetic protein-4 (Bmp-4) was increased, in the MD embryos compared with the N embryos. In MDm embryos, we detected increased activated caspase-3 immunostaining in the first visceral arch and cardiac area and decreased Gpx-1 immunostaining in the cardiac tissue; both findings differed from the caspase/Gpx-1 immunostaining of the MDn and N embryos.

CONCLUSIONS

Maternal diabetes causes growth retardation, congenital malformations, and decreased general antioxidative gene expression in the embryo. In particular, enhanced apoptosis of the first visceral arch and heart, together with decreased cardiac Gpx-1 levels, may compromise the mandible and heart and thus cause an increased risk of developing congenital malformation.

Rapid 3-dimensional imaging of embryonic craniofacial morphology using microscopic computed tomography

OBJECTIVE

Microscopic computed tomography (microCT) has been recently applied to morphological evaluation of mouse embryos with or without congenital malformations, and 3-dimensional (3D) digital images of the whole embryo can be obtained. In the present study, the authors report a modified, rapid technique of 3D embryonic microCT without processing with osmium tetroxide.

METHODS

Normal embryonic days 10.5 to 11 mouse embryos, as well as those with craniofacial anomalies treated with teratogens, were examined. After fixation, we processed the embryo samples with hexamethyldisilazane, instead of highly toxic osmium tetroxide in the original method.

RESULTS

Our protocol enabled clear 3D craniofacial imaging of the normal and anomalous mouse embryos within a short period of 20 minutes or 1 hour. In addition, some anatomical landmarks were clearly detected in the reconstituted craniofacial section images.

CONCLUSION

Our present data suggest a possible role of microCT for high-throughput morphological screening of the mouse embryos with craniofacial anomalies.

Hedgehog signalling in vascular development

The Hedgehog family of proteins are powerful morphogens mediating embryonic development as well as adult morphogenesis and carcinogenesis. For example, excess hedgehog activity has been implicated in basal cell carcinoma, medulloblastoma and rhabdomyosarcoma. More recently, hedgehog signalling has been implicated in angiogenesis. While hedgehog signalling in adult angiogenesis may constitute a simple recapitulation of that in embryonic development, it should be appreciated that Hedgehog signalling occurs in embryonic angiogenesis in different developmental contexts. This article reviews the role of Hedgehog signalling in both embryonic and postnatal vascular development. The temporal importance of a window of hedgehog dependent angiogenesis during development is emphasised and illustrated using a whole mouse embryo culture system.

Murine models of holoprosencephaly

Holoprosencephaly (HPE), the most common developmental defect of the forebrain and midface, is caused by a failure to delineate the midline in these structures. Both genetic and environmental etiologies exist for HPE, and clinical presentation is highly variable. HPE occurs in sporadic and inherited forms, and even HPE in pedigrees is characterized by incomplete penetrance and variable expressivity. Heterozygous mutations in eight different genes have been identified in human HPE, and disruption of Sonic hedgehog expression and/or signaling in the rostroventral region of the embryo is a major common effect of these mutations. An understanding of the mechanisms whereby genetic defects and teratogenic exposures become manifest as developmental anomalies of varying severity requires experimental models that accurately reproduce the spectrum of defects seen in human HPE. The mouse has emerged as such a model, because of its ease of genetic manipulation and similarity to humans in development of the forebrain and face. HPE is generally observed in mice homozygous for mutations in orthologs of human HPE genes though, unlike humans, rarely in mice with heterozygous mutations. Moreover, reverse genetics in the mouse has provided a wealth of new candidate human HPE genes. Construction of hypomorphic alleles, interbreeding to produce double mutants, and analysis of these mutations on different genetic backgrounds has generated multiple models of HPE and begun to provide insight into the conundrum of the HPE spectrum. Here, we review forebrain development with an emphasis on the pathways known to be defective in HPE and describe the strengths and weaknesses of various murine models of HPE.

Hedgehog signaling: a biophysical or biomechanical modulator in embryonic development?

Although embryonic development is inevitably affected by biophysical or biomechanical processes, it has yet to be elucidated to what extent molecular mechanisms of development are modulated by such physical factors. The hedgehog family, including Sonic hedgehog (Shh), is the most well-known morphogens involved in the developmental pattern formation of various organs, such as the nervous system, face, limbs, and skin appendages. There are several unique features in hedgehog signaling including long-range diffusion or positive and negative feedback loops, suggesting the possible modification of hedgehog signaling by biophysical or biomechanical factors. Especially, the period of embryonic day 8-10 is characterized by various biomechanically regulated processes in mouse development, such as axial rotation and vasculoangiogenesis. We executed a series of experiments using a mouse whole embryo culture system to investigate the biomechanical roles of hedgehog signaling during this period. In this review, we examine various examples in which biophysical and biomechanical aspects of hedgehog signaling in development are revealed, including our own data using the mouse whole embryo culture system.