Vascular endothelial growth factor (VEGF) isoform regulation of early forebrain development

Multi-functional near-infrared fluorescent polymer dot-siRNA for gene expression regulation

Regulation of gene expression in eukaryotic cells is critical for cell survival, proliferation, and cell fate determination. Misregulation of gene expression can have substantial, negative consequences that result in disease or tissue dysfunction that can be targeted for therapeutic intervention. Several strategies to inhibit gene expression at the level of mRNA transcription and translation have been developed, such as anti-sense inhibition and CRISPR-Cas9 gene editing. However, these strategies have some limitations in terms of specificity, toxicity, and ease of use. We have designed a nanomaterials-based tool to inhibit gene expression in eukaryotic cells with a potential application in basic and biomedical research. At the heart of our rational design approach is a polymer dots (Pdots)-based nanoplatform that can provide a means to deliver gene-specific small interfering (siRNA) into cells while at the same time providing a visualization mechanism to determine which cells have taken up the siRNA. The Pdots that we designed and synthesized had an average size 64.25 ± 0.60 nm and a zeta potential that was +37.40 ± 8.28 mV. The Pdot-1 nmole Gapdh siRNA showed an average size of 82.27 ± 9.83 nm, with the zeta potential values determined to be -52.00 ± 6.05 mV in the HEPES buffer. Both Pdots and Pdot-siRNA displayed two emission peaks in the visible (588 nm) and near-infrared (NIR) emission range (775 nm). We treated primary cultures of mouse brain-derived microvascular cells with Pdot-Gapdh siRNA and observed uniform cellular uptake of the nanomaterial in the cells and reduced intensity of Gapdh immunolabeling. Our results highlight the potential application of Pdot-siRNA for gene expression targeting with simultaneous visual monitoring of Pdot-siRNA delivery. The simple design offers a flexible and novel strategy to inhibit a wide range of mRNA targets with minimal toxicity, high efficiency, and focused cell visualization.

Sex-Dimorphic Differential Expression Profiles in the Brain of the Adult Chinese Soft-Shelled Turtle, Pelodiscus sinensis

The Chinese soft-shelled turtle (Pelodiscus sinensis) is an economically important species in aquaculture, and its growth pattern is characterized by significant sexual dimorphism. However, the underlying molecular mechanisms of this phenomenon have mostly been investigated in the gonadal tissues of P. sinensis, and there are no articles on sex differentiation from the brain of P. sinensis. Here, we analyzed transcriptomes of the brains of adult male and female P. sinensis using high-throughput Illumina sequencing technology, establishing a set of differential genes and differential transcription factors. The data showed that there were 908 genes with significant differences in expression, of which 357 genes were up-regulated and 551 genes were down-regulated. We annotated using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), and screened some genes and pathways related to growth. There were 282 growth-related differential genes and 181 sex-related differential genes. We screened the genes' growth hormone receptor (GHR) and vascular endothelial growth factor A (VEGFA), which may be related to the growth of P. sinensis. The pathways related to the growth and development of P. sinensis are the growth hormone synthesis, secretion, and action pathway; the MAPK (mitogen-activated protein kinase) pathway; and the calcium signaling pathway. In addition, through gene set enrichment analysis (GSEA), we screened out two genes, LIM homeobox protein 1 (LHX1) and fibroblast growth factor 7 (FGF7), which are related to both growth and sex differentiation, and through protein interaction analysis of these genes, we screened out eight genes, including LHX1, FGF7, GHR, fibroblast growth factor 4 (FGF4), EGFR, BMP3, GLI family zinc finger 2 (GLI2), and neuronal differentiation 1 (NEUROD1), and verified the expression levels of these eight genes in the brain of the P. sinensis by real-time quantitative PCR (qRT-PCR), which supported the reliability and accuracy of our transcriptome analysis. Our study provides a solid foundation for analyzing the mechanisms of sexual-dimorphic growth of P. sinensis and even other turtles.

Leptin signaling promotes blood vessel formation in the Xenopus tail during the embryo-larval transition

The signals that regulate peripheral blood vessel formation during development are still under investigation. The hormone leptin promotes blood vessel formation, adipose tissue establishment and expansion, tumor growth, and wound healing, but the underlying mechanisms for these actions are currently unknown. We investigated whether leptin promotes angiogenesis in the developing tail fin using embryonic transgenic xflk-1:GFP Xenopus laevis, which express a green fluorescent protein on vascular endothelial cells to mark blood vessels. We found that leptin protein is expressed in endothelial cells of developing blood vessels and that leptin treatment via injection increased phosphorylated STAT3 signaling, which is indicative of leptin activation of its receptor, in blood vessels of the larval tail fin. Leptin administration via media increased vessel length, branching, and reconnection with the cardinal vein, while decreased leptin signaling via immunoneutralization had an opposing effect on vessel development. We also observed disorganization of major vessels and microvessels of the tail fin and muscle when leptin signaling was decreased. Reduced leptin signaling lowered mRNA expression of cenpk, gpx1, and mmp9, markers for cell proliferation, antioxidation, and extracellular matrix remodeling/cell migration, respectively, in the developing tail, providing insight into three possible mechanisms underlying leptin's promotion of angiogenesis. Together these results illustrate that leptin levels are correlated with embryonic angiogenesis and that leptin coordinates multiple aspects of blood vessel growth and development, showing that leptin is an important morphogen during embryonic development.

Repeated Intravenous Administration of Human Neural Stem Cells Producing Choline Acetyltransferase Exerts Anti-Aging Effects in Male F344 Rats

Major features of aging might be progressive decreases in cognitive function and physical activity, in addition to withered appearance. Previously, we reported that the intracerebroventricular injection of human neural stem cells (NSCs named F3) encoded the choline acetyltransferase gene (F3.ChAT). The cells secreted acetylcholine and growth factors (GFs) and neurotrophic factors (NFs), thereby improving learning and memory function as well as the physical activity of aged animals. In this study, F344 rats (10 months old) were intravenously transplanted with F3 or F3.ChAT NSCs (1 × 106 cells) once a month to the 21st month of age. Their physical activity and cognitive function were investigated, and brain acetylcholine (ACh) and cholinergic and dopaminergic system markers were analyzed. Neuroprotective and neuroregenerative activities of stem cells were also confirmed by analyzing oxidative damages, neuronal skeletal protein, angiogenesis, brain and muscle weights, and proliferating host stem cells. Stem cells markedly improved both cognitive and physical functions, in parallel with the elevation in ACh levels in cerebrospinal fluid and muscles, in which F3.ChAT cells were more effective than F3 parental cells. Stem cell transplantation downregulated CCL11 and recovered GFs and NFs in the brain, leading to restoration of microtubule-associated protein 2 as well as functional markers of cholinergic and dopaminergic systems, along with neovascularization. Stem cells also restored muscular GFs and NFs, resulting in increased angiogenesis and muscle mass. In addition, stem cells enhanced antioxidative capacity, attenuating oxidative damage to the brain and muscles. The results indicate that NSCs encoding ChAT improve cognitive function and physical activity of aging animals by protecting and recovering functions of multiple organs, including cholinergic and dopaminergic systems, as well as muscles from oxidative injuries through secretion of ACh and GFs/NFs, increased antioxidant elements, and enhanced blood flow.

Interneuron odyssey: molecular mechanisms of tangential migration

Cortical GABAergic interneurons are critical components of neural networks. They provide local and long-range inhibition and help coordinate network activities involved in various brain functions, including signal processing, learning, memory and adaptative responses. Disruption of cortical GABAergic interneuron migration thus induces profound deficits in neural network organization and function, and results in a variety of neurodevelopmental and neuropsychiatric disorders including epilepsy, intellectual disability, autism spectrum disorders and schizophrenia. It is thus of paramount importance to elucidate the specific mechanisms that govern the migration of interneurons to clarify some of the underlying disease mechanisms. GABAergic interneurons destined to populate the cortex arise from multipotent ventral progenitor cells located in the ganglionic eminences and pre-optic area. Post-mitotic interneurons exit their place of origin in the ventral forebrain and migrate dorsally using defined migratory streams to reach the cortical plate, which they enter through radial migration before dispersing to settle in their final laminar allocation. While migrating, cortical interneurons constantly change their morphology through the dynamic remodeling of actomyosin and microtubule cytoskeleton as they detect and integrate extracellular guidance cues generated by neuronal and non-neuronal sources distributed along their migratory routes. These processes ensure proper distribution of GABAergic interneurons across cortical areas and lamina, supporting the development of adequate network connectivity and brain function. This short review summarizes current knowledge on the cellular and molecular mechanisms controlling cortical GABAergic interneuron migration, with a focus on tangential migration, and addresses potential avenues for cell-based interneuron progenitor transplants in the treatment of neurodevelopmental disorders and epilepsy.

Streamlined synthesis of potential dual-emissive fluorescent silicon quantum dots (SiQDs) for cell imaging

One of the current challenges of working with nanomaterials in bioapplications is having a tool that is biocompatible (non-toxic) and produces stable, intense fluorescence for bioimaging. To address these challenges, we have developed a streamlined and one-pot synthetic route for silicon-based quantum dots (SiQDs) using a hydrothermal method. Part of our unique approach for designing the SiQDs was to incorporate (3-aminopropyl) triethoxysilane (APTES), which is an amphipathic molecule with hydroxyl and amine functional groups available for modification. In order to reduce the toxicity of APTES, we chose glucose as a reducing agent for the reaction. The resulting SiQDs produced potent, stable, potential dual-emissive fluorescence emission peaks in the visible and near-infrared (NIR) ranges. Both peaks could be used as distinguishing fluorescence signals for bioimaging, separately or in combination. The physical and optical properties of the SiQDs were determined under a range of environmental conditions. The morphology, surface composition, and electronic structure of the SiQDs were characterized using high resolution-transmission electronic microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The stability of the SiQDs was evaluated under a wide range of pHs. The biocompatibility and imaging potential of the SiQDs were tested in microvascular endothelial cells (MVEC), neural stem cells (NSC), and RAW 264.7 macrophage cells. The images obtained revealed different subcellular localizations, particularly during cell division, with distinct fluorescence intensities. The results demonstrated that SiQDs are a promising, non-toxic labeling tool for a variety of cell types, with the added advantage of having dual emission peaks both in visible and NIR ranges for bioimaging.

3D patient-derived tumor models to recapitulate pediatric brain tumors In Vitro

Brain tumors are the leading cause of cancer-related deaths in children. Tailored therapies need preclinical brain tumor models representing a wide range of molecular subtypes. Here, we adapted a previously established brain tissue-model to fresh patient tumor cells with the goal of establishing3D in vitro culture conditions for each tumor type.Wereported our findings from 11 pediatric tumor cases, consisting of three medulloblastoma (MB) patients, three ependymoma (EPN) patients, one glioblastoma (GBM) patient, and four juvenile pilocytic astrocytoma (Ast) patients. Chemically defined media consisting of a mixture of pro-neural and pro-endothelial cell culture medium was found to support better growth than serum-containing medium for all the tumor cases we tested. 3D scaffold alone was found to support cell heterogeneity and tumor type-dependent spheroid-forming ability; both properties were lost in 2D or gel-only control cultures. Limited in vitro models showed that the number of differentially expressed genes between in vitro vs. primary tissues, are 104 (0.6%) of medulloblastoma, 3,392 (20.2%) of ependymoma, and 576 (3.4%) of astrocytoma, out of total 16,795 protein-coding genes and lincRNAs. Two models derived from a same medulloblastoma patient clustered together with the patient-matched primary tumor tissue; both models were 3D scaffold-only in Neurobasal and EGM 1:1 (v/v) mixture and differed by a 1-mo gap in culture (i.e., 6wk versus 10wk). The genes underlying the in vitrovs. in vivo tissue differences may provide mechanistic insights into the tumor microenvironment. This study is the first step towards establishing a pipeline from patient cells to models to personalized drug testing for brain cancer.

Netrin-1 promotes retinoblastoma-associated angiogenesis

BACKGROUND

Retinoblastoma (Rb) is the most common intraocular cancer of infancy and childhood, with an incidence of nearly 0.006% in all live births. Although a functional loss or inactivation of both alleles of the retinoblastoma 1 (RB1) gene during retinal development appears to be the predominant etiology for Rb, genes associated with tumor angiogenesis are also likely to be involved in the development of this condition. Netrin-1 is a factor that regulates pathological angiogenesis, while its role in Rb is largely unknown. The present study examined the role of netrin-1 in Rb.

METHODS

The expression of netrin-1 in Rb was assessed using public databases and using clinical specimens by RT-qPCR for mRNA and by ELISA for protein. The expression of netrin-1 was suppressed in Rb by siRNA and the effects on cell growth were determined by a CCK-8 assay, while the effects on angiogenesis were examined in vitro using human umbilical vein endothelial cell (HUVEC) assays and in vivo by quantification of tumor vessel density.

RESULTS

Analysis of published databases revealed that the netrin-1 gene is significantly upregulated in Rb, which was confirmed by immunohistochemistry on clinical specimens. Inhibition of netrin-1 in Rb cell lines significantly reduced their effects on angiogenesis in vitro using a HUVEC co-culture assay without affecting cell growth. Inhibition of netrin-1 expression in vivo suppressed the growth of grafted Rb, and this effect could be abolished by co-expression of vascular endothelial growth factor A (VEGF-A).

CONCLUSIONS

This data demonstrated a novel role for netrin-1 in the regulation of Rb-associated cancer vascularization and may represent a novel therapeutic target for patients with Rb.

The CCN2/CTGF interactome: an approach to understanding the versatility of CCN2/CTGF molecular activities

Cellular communication network 2 (CCN2), also known as connective tissue growth factor (CTGF) regulates diverse cellular processes, some at odds with others, including adhesion, proliferation, apoptosis, and extracellular matrix (ECM) protein synthesis. Although a cause-and-effect relationship between CCN2/CTGF expression and local fibrotic reactions has initially been established, CCN2/CTGF manifests cell-, tissue-, and context-specific functions and differentially affects developmental and pathological processes ranging from progenitor cell fate decisions and angiogenesis to inflammation and tumorigenesis. CCN2/CTGF multimodular structure, binding to and activation or inhibition of multiple cell surface receptors, growth factors and ECM proteins, and susceptibility for proteolytic cleavage highlight the complexity to CCN2/CTGF biochemical attributes. CCN2/CTGF expression and dosage in the local environment affects a defined community of its interacting partners, and this results in sequestration of growth factors, interference with or potentiation of ligand-receptor binding, cellular internalization of CCN2/CTGF, inhibition or activation of proteases, and generation of CCN2/CTGF degradome products that add molecular diversity and expand the repertoire of functional modules in the cells and their microenvironment. Through these interactions, different intracellular signals and cellular responses are elicited culminating into physiological or pathological reactions. Thus, the CCN2/CTGF interactome is a defining factor of its tissue- and context-specific effects. Mapping of new CCN2/CTGF binding partners might shed light on yet unknown roles of CCN2/CTGF and provide a solid basis for tissue-specific targeting this molecule or its interacting partners in a therapeutic context.

Thalidomide targets EGFL6 to inhibit EGFL6/PAX6 axis-driven angiogenesis in small bowel vascular malformation

BACKGROUND

Small bowel vascular malformation disease (SBVM) is the most common cause of obscure gastrointestinal bleeding (OGIB). Several studies suggested that EGFL6 was able to promote the growth of tumor endothelial cells by forming tumor vessels. To date, it remains unclear how EGFL6 promotes pathological angiogenesis in SBVM and whether EGFL6 is a target of thalidomide.

METHODS

We took advantage of SBVM plasma and tissue samples and compared the expression of EGFL6 between SBVM patients and healthy people via ELISA and Immunohistochemistry. We elucidated the underlying function of EGFL6 in SBVM in vitro and by generating a zebrafish model that overexpresses EGFL6, The cycloheximide (CHX)-chase experiment and CoIP assays were conducted to demonstrate that thalidomide can promote the degradation of EGFL6 by targeting CRBN.

RESULTS

The analysis of SBVM plasma and tissue samples revealed that EGFL6 was overexpressed in the patients compared to healthy people. Using in vitro and in vivo assays, we demonstrated that an EMT pathway triggered by the EGFL6/PAX6 axis is involved in the pathogenesis of SBVM. Furthermore, through in vitro and in vivo assays, we elucidated that thalidomide can function as anti-angiogenesis medicine through the regulation of EGFL6 in a proteasome-dependent manner. Finally, we found that CRBN can mediate the effect of thalidomide on EGFL6 expression and that the CRBN protein interacts with EGFL6 via a Lon N-terminal peptide.

CONCLUSION

Our findings revealed a key role for EGFL6 in SBVM pathogenesis and provided a mechanism explaining why thalidomide can cure small bowel bleeding resulting from SBVM.

Placental growth factor in beta cells plays an essential role in gestational beta-cell growth

OBJECTIVE

Pancreatic beta cells proliferate in response to metabolic requirements during pregnancy, while failure of this response may cause gestational diabetes. A member of the vascular endothelial growth factor family, placental growth factor (PlGF), typically plays a role in metabolic disorder and pathological circumstance. The expression and function of PlGF in the endocrine pancreas have not been reported and are addressed in the current study.

RESEARCH DESIGN AND METHODS

PlGF levels in beta cells were determined by immunostaining or ELISA in purified beta cells in non-pregnant and pregnant adult mice. An adeno-associated virus (AAV) serotype 8 carrying a shRNA for PlGF under the control of a rat insulin promoter (AAV-rat insulin promoter (RIP)-short hairpin small interfering RNA for PlGF (shPlGF)) was prepared and infused into mouse pancreas through the pancreatic duct to specifically knock down PlGF in beta cells, and its effects on beta-cell growth were determined by beta-cell proliferation, beta-cell mass and insulin release. A macrophage-depleting reagent, clodronate, was coapplied into AAV-treated mice to study crosstalk between beta cells and macrophages.

RESULTS

PlGF is exclusively produced by beta cells in the adult mouse pancreas. Moreover, PlGF expression in beta cells was significantly increased during pregnancy. Intraductal infusion of AAV-RIP-shPlGF specifically knocked down PlGF in beta cells, resulting in compromised beta-cell proliferation, reduced growth in beta-cell mass and impaired glucose tolerance during pregnancy. Mechanistically, PlGF depletion in beta cells reduced islet infiltration of trophic macrophages, which appeared to be essential for gestational beta-cell growth.

CONCLUSIONS

Our study suggests that increased expression of PlGF in beta cells may trigger gestational beta-cell growth through recruited macrophages.

Improved therapeutic effects on diabetic foot by human mesenchymal stem cells expressing MALAT1 as a sponge for microRNA-205-5p

Diabetic foot (DF) is a common complication of high severity for diabetes, a prevalent metabolic disorder that affects billions of people worldwide. Mesenchymal stem cells (MSCs) have a demonstrative therapeutic effect on DF, through their generation of pro-angiogenesis factors, like vascular endothelial growth factor (VEGF). Recently, genetically modified MSCs have been used in therapy and we have shown that depletion of micoRNA-205-5p (miR-205-5p) in human MSCs promotes VEGF-mediated therapeutic effects on DF. Here, we showed that a long non-coding RNA (lncRNA), MALAT1, is a competing endogenous RNA (ceRNA) for miR-205-5p, and is low expressed in human MSCs. Ectopic expression of MALAT1 in human MSCs significantly decreased miR-205-5p levels, resulting in upregulation of VEGF production and improved in vitro endothelial cell tube formation. In a DF model in immunodeficient NOD/SCID mice, transplantation of human miR-205-5p-depleted MSCs exhibited better therapeutic effects on DF recovery than control MSCs. Moreover, MALAT1-expressing MSCs showed even better therapeutic effects on DF recovery than miR-205-5p-depleted MSCs. This difference in DF recovery was shown to be associated with the levels of on-site vascularization. Together, our data suggest that MALAT1 functions as a sponge RNA for miR-205-5p to increase therapeutic effects of MSCs on DF.

Vascular-Derived Vegfa Promotes Cortical Interneuron Migration and Proximity to the Vasculature in the Developing Forebrain

Vascular endothelial growth factor (Vegfa) is essential for promoting the vascularization of the embryonic murine forebrain. In addition, it directly influences neural development, although its role in the forming forebrain is less well elucidated. It was recently suggested that Vegfa may influence the development of GABAergic interneurons, inhibitory cells with crucial signaling roles in cortical neuronal circuits. However, the mechanism by which it affects interneuron development remains unknown. Here we investigated the developmental processes by which Vegfa may influence cortical interneuron development by analyzing transgenic mice that ubiquitously express the Vegfa120 isoform to perturb its signaling gradient. We found that interneurons reach the dorsal cortex at mid phases of corticogenesis despite an aberrant vascular network. Instead, endothelial ablation of Vegfa alters cortical interneuron numbers, their intracortical distribution and spatial proximity to blood vessels. We show for the first time that vascular-secreted guidance factors promote early-migrating interneurons in the intact forebrain in vivo and identify a novel role for vascular-Vegfa in this process.

Suppression of microRNA-205-5p in human mesenchymal stem cells improves their therapeutic potential in treating diabetic foot disease

Diabetes is a prevalent disease endangering human health, while diabetic foot disease (DF) is one of the most severe complications of diabetes. Mesenchymal stem cells (MSCs) have been used in DF treatment, taking advantage of the differentiation potential of MSCs into endothelial cells and their production and secretion of trophic factors like vascular endothelial growth factor (VEGF). Molecular modification of MSCs to improve their therapeutic effects has been recently applied in treating other diseases, but not yet in DF. Here, we found that micoRNA-205-5p (miR-205-5p) is expressed in human MSCs, and miR-205-5p inhibits protein translation of VEGF through its interaction with 3'-UTR of the VEGF mRNA. Expression of antisense of miR-205-5p (as-miR-205-5p) significantly increased both cellular and secreted VEGF by MSCs, which significantly improved the therapeutic effects of MSCs on DF-associated wound healing in diabetic NOD/SCID mice. Together, our data suggest that miR-205-5p suppression in MSCs may improve their therapeutic effects on DF, seemingly through augmentation of VEGF-mediated vascularization.

Nucleolin-targeted Extracellular Vesicles as a Versatile Platform for Biologics Delivery to Breast Cancer

Small interfering RNAs (siRNA)/microRNAs (miRNA) have promising therapeutic potential, yet their clinical application has been hampered by the lack of appropriate delivery systems. Herein, we employed extracellular vesicles (EVs) as a targeted delivery system for small RNAs. EVs are cell-derived small vesicles that participate in cell-to-cell communication for protein and RNA delivery. We used the aptamer AS1411-modified EVs for targeted delivery of siRNA/microRNA to breast cancer tissues. Tumor targeting was facilitated via AS1411 binding to nucleolin, which is highly expressed on the surface membrane of breast cancer cells. This delivery vesicle targeted let-7 miRNA delivery to MDA-MB-231 cells in vitro as confirmed with fluorescent microscopic imaging and flow cytometry. Also, intravenously delivered AS1411-EVs loaded with miRNA let-7 labeled with the fluorescent marker, Cy5, selectively targeted tumor tissues in tumor-bearing mice and inhibited tumor growth. Importantly, the modified EVs were well tolerated and showed no evidence of nonspecific side effects or immune response. Thus, the RNAi nanoplatform is versatile and can deliver siRNA or miRNA to breast cancer cells both in vitro and in vivo. Our results suggest that the AS1411-EVs have a great potential as drug delivery vehicles to treat cancers.

Cerebrovascular defects in Foxc1 mutants correlate with aberrant WNT and VEGF-A pathways downstream of retinoic acid from the meninges

Growth and maturation of the cerebrovasculature is a vital event in neocortical development however mechanisms that control cerebrovascular development remain poorly understood. Mutations in or deletions that include the FOXC1 gene are associated with congenital cerebrovascular anomalies and increased stroke risk in patients. Foxc1 mutant mice display severe cerebrovascular hemorrhage at late gestational ages. While these data demonstrate Foxc1 is required for cerebrovascular development, its broad expression in the brain vasculature combined with Foxc1 mutant's complex developmental defects have made it difficult to pinpoint its function(s). Using global and conditional Foxc1 mutants, we find 1) significant cerebrovascular growth defects precede cerebral hemorrhage and 2) expression of Foxc1 in neural crest-derived meninges and brain pericytes, though not endothelial cells, is required for normal cerebrovascular development. We provide evidence that reduced levels of meninges-derived retinoic acid (RA), caused by defects in meninges formation in Foxc1 mutants, is a major contributing factor to the cerebrovascular growth defects in Foxc1 mutants. We provide data that suggests that meninges-derived RA ensures adequate growth of the neocortical vasculature via regulating expression of WNT pathway proteins and neural progenitor derived-VEGF-A. Our findings offer the first evidence for a role of the meninges in brain vascular development and provide new insight into potential causes of cerebrovascular defects in patients with FOXC1 mutations.

Autocrine VEGF Isoforms Differentially Regulate Endothelial Cell Behavior

Vascular endothelial growth factor A (VEGF) is involved in all the essential biology of endothelial cells, from proliferation to vessel function, by mediating intercellular interactions and monolayer integrity. It is expressed as three major alternative spliced variants. In mice, these are VEGF120, VEGF164, and VEGF188, each with different affinities for extracellular matrices and cell surfaces, depending on the inclusion of heparin-binding sites, encoded by exons 6 and 7. To determine the role of each VEGF isoform in endothelial homeostasis, we compared phenotypes of primary endothelial cells isolated from lungs of mice expressing single VEGF isoforms in normoxic and hypoxic conditions. The differential expression and distribution of VEGF isoforms affect endothelial cell functions, such as proliferation, adhesion, migration, and integrity, which are dependent on the stability of and affinity to VEGF receptor 2 (VEGFR2). We found a correlation between autocrine VEGF164 and VEGFR2 stability, which is also associated with increased expression of proteins involved in cell adhesion. Endothelial cells expressing only VEGF188, which localizes to extracellular matrices or cell surfaces, presented a mesenchymal morphology and weakened monolayer integrity. Cells expressing only VEGF120 lacked stable VEGFR2 and dysfunctional downstream processes, rendering the cells unviable. Endothelial cells expressing these different isoforms in isolation also had differing rates of apoptosis, proliferation, and signaling via nitric oxide (NO) synthesis. These data indicate that autocrine signaling of each VEGF isoform has unique functions on endothelial homeostasis and response to hypoxia, due to both distinct VEGF distribution and VEGFR2 stability, which appears to be, at least partly, affected by differential NO production. This study demonstrates that each autocrine VEGF isoform has a distinct effect on downstream functions, namely VEGFR2-regulated endothelial cell homeostasis in normoxia and hypoxia.

Regulating the regulators of angiogenesis by CCN1 and taking it up a Notch

CCN1 is encoded by an extracellular matrix protein-gene that is essential for the proper development of the cardiovascular system and the control of angiogenesis, inflammation, progenitor cell lineage commitment and extracellular matrix protein remodeling during the adult life. High-precision genetic models of tissue-specific gene deletion demonstrated a pivotal role of CCN1 in providing positional information to angiogenic endothelial cells (ECs) during the outgrowth and maturation of nascent blood vessel sprouts, fine-controlling Notch-dependent inter-endothelial cell communications and mediating interaction with inflammatory cells. Some of these pleiotropic activities of CCN1 are unique among proteins of the extracellular matrix. Thus, CCN1 represents a model molecule for investigating and unraveling novel aspects of extracellular protein signaling in vascular development and diseases.

The alternative complement pathway aids in vascular regression during the early stages of a murine model of proliferative retinopathy

Proliferative retinopathic diseases often progress in 2 phases: initial regression of retinal vasculature (phase 1) followed by subsequent neovascularization (NV) (phase 2). The immune system has been shown to aid in vascular pruning in such retinopathies; however, little is known about the role of the alternative complement pathway in the initial vascular regression phase. Using a mouse model of oxygen-induced retinopathy (OIR), we observed that alternative complement pathway-deficient mice (Fb(-/-)) exhibited a mild decrease in vascular loss at postnatal day (P)8 compared with age- and strain-matched controls (P = 0.035). Laser capture microdissection was used to isolate the retinal blood vessels. Expression of the complement inhibitors Cd55 and Cd59 was significantly decreased in blood vessels isolated from hyperoxic retinas compared with those from normoxic control mice. Vegf expression was measured at P8 and found to be significantly lower in OIR mice than in normoxic control mice (P = 0.0048). Further examination of specific Vegf isoform expression revealed a significant decrease in Vegf120 (P = 0.00032) and Vegf188 (P = 0.0092). In conjunction with the major modulating effects of Vegf during early retinal vascular development, our data suggest a modest involvement of the alternative complement pathway in targeting vessels for regression in the initial vaso-obliteration stage of OIR.

Anti-vascular endothelial growth factor therapies in ophthalmology: current use, controversies and the future

Use of anti-vascular endothelial growth factor (VEGF) therapies was introduced for the treatment of ocular disorders in 2005. In the UK, the current licensed and NICE approved indications are for the treatment of neovascular age-related macular degeneration (nAMD), diabetic macular oedema (DMO), macular oedema secondary to a retinal vein occlusion (RVO) and choroidal neovascularization in pathological myopia. These diagnoses alone account for two-thirds of the main causes of legally registrable visual impairment and blindness. Ranibizumab (Lucentis®; Genentech/Novartis), a drug specifically designed for intraocular use, is the primary licensed medication. Controversially however, clinicians have been using an unlicensed cheaper drug, bevacizumab (Avastin®; Genentech/Roche), originally designed for systemic administration, with a similar mode of action and shown to have a similar efficacy. However, there are fears of greater side effects with bevacizumab though studies have not been sufficiently powered to show statistical difference. In the current global economic climate, anti-VEGF treatment places huge financial and logistical pressure on already strained health care systems. Bevacizumab is considerably more cost effective than ranibizumab, and thus using bevacizumab would widen access to treatment particularly in developing countries. This licensing issue also places clinicians in a difficult medico-legal position especially in Europe, where doctors are duty bound to use a licensed drug for a particular indication if this is available. As the indications of anti-VEGF therapies expand and the cost of health care provision becomes more expensive, the controversies surrounding their use will inevitably become more important.

Linking pathways in the developing and aging brain with neurodegeneration

The molecular and cellular mechanisms, which coordinate the critical stages of brain development to reach a normal structural organization with appropriate networks, are progressively being elucidated. Experimental and clinical studies provide evidence of the occurrence of developmental alterations induced by genetic or environmental factors leading to the formation of aberrant networks associated with learning disabilities. Moreover, evidence is accumulating that suggests that also late-onset neurological disorders, even Alzheimer's disease, might be considered disorders of aberrant neural development with pathological changes that are set up at early stages of development before the appearance of the symptoms. Thus, evaluating proteins and pathways that are important in age-related neurodegeneration in the developing brain together with the characterization of mechanisms important during brain development with relevance to brain aging are of crucial importance. In the present review we focus on (1) aspects of neurogenesis with relevance to aging; (2) neurodegenerative disease (NDD)-associated proteins/pathways in the developing brain; and (3) further pathways of the developing or neurodegenerating brains that show commonalities. Elucidation of complex pathogenetic routes characterizing the earliest stage of the detrimental processes that result in pathological aging represents an essential first step toward a therapeutic intervention which is able to reverse these pathological processes and prevent the onset of the disease. Based on the shared features between pathways, we conclude that prevention of NDDs of the elderly might begin during the fetal and childhood life by providing the mothers and their children a healthy environment for the fetal and childhood development.

Shifts in the vascular endothelial growth factor isoforms result in transcriptome changes correlated with early neural stem cell proliferation and differentiation in mouse forebrain

Regulation of neural stem cell (NSC) fate decisions is critical during the transition from a multicellular mammalian forebrain neuroepithelium to the multilayered neocortex. Forebrain development requires coordinated vascular investment alongside NSC differentiation. Vascular endothelial growth factor A (Vegf) has proven to be a pleiotrophic gene whose multiple protein isoforms regulate a broad range of effects in neurovascular systems. To test the hypothesis that the Vegf isoforms (120, 164, and 188) are required for normal forebrain development, we analyzed the forebrain transcriptome of mice expressing specific Vegf isoforms, Vegf120, VegfF188, or a combination of Vegf120/188. Transcriptome analysis identified differentially expressed genes in embryonic day (E) 9.5 forebrain, a time point preceding dramatic neuroepithelial expansion and vascular investment in the telencephalon. Meta-analysis identified gene pathways linked to chromosome-level modifications, cell fate regulation, and neurogenesis that were altered in Vegf isoform mice. Based on these gene network shifts, we predicted that NSC populations would be affected in later stages of forebrain development. In the E11.5 telencephalon, we quantified mitotic cells [Phospho-Histone H3 (pHH3)-positive] and intermediate progenitor cells (Tbr2/Eomes-positive), observing quantitative and qualitative shifts in these populations. We observed qualitative shifts in cortical layering at P0, particularly with Ctip2-positive cells in layer V. The results identify a suite of genes and functional gene networks that can be used to further dissect the role of Vegf in regulating NSC differentiation and downstream consequences for NSC fate decisions.

Neural stem cell survival factors

Neural stem and progenitor cells (NSCs and NPs) give rise to the central nervous system (CNS) during embryonic development. NSCs and NPs differentiate into three main cell-types of the CNS; astrocytes, oligodendrocytes, and neurons. NSCs are present in the adult CNS and are important in maintenance and repair. Adult NSCs hold great promise for endogenous or self-repair of the CNS. Intriguingly, NSCs have been implicated as the cells that give rise to brain tumors. Thus, the balance between survival, growth and differentiation is a critical aspect of NSC biology, during development, in the adult, and in disease processes. In this review, we survey what is known about survival factors that control both embryonic and adult NSCs. We discuss the neurosphere culture system as this is widely used to measure NSC activity and behavior in vitro and emphasize the importance of clonality. We define here NSC survival factors in their broadest sense to include any factor that influences survival and proliferation of NSCs and NPs. NSC survival factors identified to date include growth factors, morphogens, proteoglycans, cytokines, hormones, and neurotransmitters. Understanding NSC and NP interaction in response to these survival factors will provide insight to CNS development, disease and repair.

Hypoglycemia reduces vascular endothelial growth factor A production by pancreatic beta cells as a regulator of beta cell mass

VEGF-A expression in beta cells is critical for pancreatic development, formation of islet-specific vasculature, and Insulin secretion. However, two key questions remain. First, is VEGF-A release from beta cells coupled to VEGF-A production in beta cells? Second, how is the VEGF-A response by beta cells affected by metabolic signals? Here, we show that VEGF-A secretion, but not gene transcription, in either cultured islets or purified pancreatic beta cells, was significantly reduced early on during low glucose conditions. In vivo, a sustained hypoglycemia in mice was induced with Insulin pellets, resulting in a significant reduction in beta cell mass. This loss of beta cell mass could be significantly rescued with continuous delivery of exogenous VEGF-A, which had no effect on beta cell mass in normoglycemic mice. In addition, an increase in apoptotic endothelial cells during hypoglycemia preceded an increase in apoptotic beta cells. Both endothelial and beta cell apoptosis were prevented by exogenous VEGF-A, suggesting a possible causative relationship between reduced VEGF-A and the loss of islet vasculature and beta cells. Furthermore, in none of these experimental groups did beta cell proliferation and islet vessel density change, suggesting a tightly regulated balance between these two cellular compartments. The average islet size decreased in hypoglycemia, which was also prevented by exogenous VEGF-A. Taken together, our data suggest that VEGF-A release in beta cells is independent of VEGF-A synthesis. Beta cell mass can be regulated through modulated release of VEGF-A from beta cells based on physiological need.

Tumor angiogenesis and anti-angiogenic therapy in malignant gliomas revisited

The cellular and molecular mechanisms of tumor angiogenesis and its prospects for anti-angiogenic cancer therapy are major issues in almost all current concepts of both cancer biology and targeted cancer therapy. Currently, (1) sprouting angiogenesis, (2) vascular co-option, (3) vascular intussusception, (4) vasculogenic mimicry, (5) bone marrow-derived vasculogenesis, (6) cancer stem-like cell-derived vasculogenesis and (7) myeloid cell-driven angiogenesis are all considered to contribute to tumor angiogenesis. Many of these processes have been described in developmental angiogenesis; however, the relative contribution and relevance of these in human brain cancer remain unclear. Preclinical tumor models support a role for sprouting angiogenesis, vascular co-option and myeloid cell-derived angiogenesis in glioma vascularization, whereas a role for the other four mechanisms remains controversial and rather enigmatic. The anti-angiogenesis drug Avastin (Bevacizumab), which targets VEGF, has become one of the most popular cancer drugs in the world. Anti-angiogenic therapy may lead to vascular normalization and as such facilitate conventional cytotoxic chemotherapy. However, preclinical and clinical studies suggest that anti-VEGF therapy using bevacizumab may also lead to a pro-migratory phenotype in therapy resistant glioblastomas and thus actively promote tumor invasion and recurrent tumor growth. This review focusses on (1) mechanisms of tumor angiogenesis in human malignant glioma that are of particular relevance for targeted therapy and (2) controversial issues in tumor angiogenesis such as cancer stem-like cell-derived vasculogenesis and bone-marrow-derived vasculogenesis.

Linkage study of embryopathy-polygenic inheritance of diabetes-induced skeletal malformations in the rat

We developed an inbred rat model of diabetic embryopathy, in which the offspring displays skeletal malformations (agnathia or micrognathia) when the mother is diabetic, and no malformations when she is not diabetic. Our aim was to find genes controlling the embryonic maldevelopment in a diabetic environment. We contrasted the fetal outcome in inbred Sprague-Dawley L rats (20% skeletal malformations in diabetic pregnancy) with that of inbred Wistar Furth rats (denotedW, no skeletal malformations in diabetic pregnancy). We used offspring from the backcross F(1)×L to probe for the genetic basis for malformation of the mandible in diabetic pregnancy. A set of 186 fetuses (93 affected, 93 unaffected) was subjected to a whole genome scan with 160 micro satellites. Analysis of genotype distribution indicated 7 loci on chromosome 4, 10 (3 loci), 14, 18, and 19 in the teratogenic process (and 14 other loci on 12 chromosomes with less strong association to the malformations), several of which contained genes implicated in other experimental studies of diabetic embryopathy. These candidate genes will be scrutinized in further experimentation. We conclude that the genetic involvement in rodent diabetic embryopathy is polygenic and predisposing for congenital malformations.

The Long and the Short of it: Gene and Environment Interactions During Early Cortical Development and Consequences for Long-Term Neurological Disease

Cortical development is a complex amalgamation of proliferation, migration, differentiation, and circuit formation. These processes follow defined timescales and are controlled by a combination of intrinsic and extrinsic factors. It is currently unclear how robust and flexible these processes are and whether the developing brain has the capacity to recover from disruptions. What is clear is that there are a number of cognitive disorders or conditions that are elicited as a result of disrupted cortical development, although it may take a long time for the full pathophysiology of the conditions to be realized clinically. The critical window for the manifestation of a neurodevelopmental disorder is prolonged, and there is the potential for a complex interplay between genes and environment. While there have been extended investigations into the genetic basis of a number of neurological and mental disorders, limited definitive associations have been discovered. Many environmental factors, including inflammation and stress, have been linked to neurodevelopmental disorders, and it may be that a better understanding of the interplay between genes and environment will speed progress in this field. In particular, the development of the brain needs to be considered in the context of the whole materno-fetal unit as the degree of the metabolic, endocrine, or inflammatory responses, for example, will greatly influence the environment in which the brain develops. This review will emphasize the importance of extending neurodevelopmental studies to the contribution of the placenta, vasculature, cerebrospinal fluid, and to maternal and fetal immune response. These combined investigations are more likely to reveal genetic and environmental factors that influence the different stages of neuronal development and potentially lead to the better understanding of the etiology of neurological and mental disorders such as autism, epilepsy, cerebral palsy, and schizophrenia.

Neural differentiation of rat aorta pericyte cells

Pericyte perivascular cells, believed to originate mesenchymal stem cells (MSC), are characterized by their capability to differentiate into various phenotypes and participate in tissue reconstruction of different organs, including the brain. We show that these cells can be induced to differentiation into neural-like phenotypes. For these studies, pericytes were obtained from aorta ex-plants of Sprague-Dawley rats and differentiated into neural cells following induction with trans retinoic acid (RA) in serum-free defined media or differentiation media containing nerve growth and brain-derived neuronal factor, B27, N2, and IBMX. When induced to differentiation with RA, cells express the pluripotency marker protein stage-specific embryonic antigen-1, neural-specific proteins β3-tubulin, neurofilament-200, and glial fibrillary acidic protein, suggesting that pericytes undergo differentiation, similar to that of neuroectodermal cells. Differentiated cells respond with intracellular calcium transients to membrane depolarization by KCl indicating the presence of voltage-gated ion channels and express functional N-methyl-D-aspartate receptors, characteristic for functional neurons. The study of neural differentiation of pericytes contributes to the understanding of induction of neuroectodermal differentiation as well as providing a new possible stem-cell source for cell regeneration therapy in the brain.