Neurogenic effect of vascular endothelial growth factor during germ layer formation of human embryonic stem cells

VEGFA-modified DPSCs combined with LC-YE-PLGA NGCs promote facial nerve injury repair in rats

Objective

The aim of this research was to investigate the effect of vascular endothelial growth factor A (VEGFA)-overexpressing rat dental pulp stem cells (rDPSCs) combined with laminin-coated and yarn-encapsulated poly(_l-lactide-co-glycolide) (PLGA) nerve guidance conduit (LC-YE-PLGA NGC) in repairing 10 mm facial nerve injury in rats.

Study Design

rDPSCs isolated from rat mandibular central incisor were cultured and identified in vitro and further transfected with the lentiviral vectors (Lv-VEGFA). To investigate the role and mechanisms of VEGFA in neurogenic differentiation in vitro, semaxanib (SU5416), Cell Counting Kit-8 (CCK-8), real-time quantitative polymerase chain reaction (qPCR) and Western blotting were performed. Ten-millimeter facial nerve defect models in rats were established and bridged by LC-YE-PLGA NGCs. The repair effects were detected by transmission electron microscopy (TEM), compound muscle action potential (CMAP), immunohistochemistry and immunofluorescence.

Results

Extracted cells exhibited spindle-shaped morphology, presented typical markers (CD44⁺CD90⁺CD34^-CD45^-), and presented multidirectional differentiation potential. The DPSCs with VEGFA overexpression were constructed successfully. VEGFA enhanced the proliferation and neural differentiation ability of rDPSCs, and the expression of neuron-specific enolase (NSE) and βIII-tubulin was increased. However, these trends were reversed with the addition of SU5416. This suggests that VEGFA mediates the above effects mainly through vascular endothelial growth factor receptor 2 (VEGFR2) binding. The LC-YE-NGC basically meet the requirements of facial nerve repair. For the in vivo experiment, the CMAP latency period was shorter in DPSCS-VEGFA-NGC group in comparison with other experimental groups, while the amplitude was increased. Such functional recovery correlated well with an increase in histological improvement. Further study suggested that VEGFA-modified DPSCs could increase the myelin number, thickness and axon diameter of facial nerve. NSE, βIII-tubulin and S100 fluorescence intensity and immunohistochemical staining intensity were significantly enhanced.

Conclusion

VEGFA-modified rDPSCs combined with LC-YE-PLGA NGCs have certain advantages in the growth and functional recovery of facial nerves in rats.

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.

Patient-specific pluripotent stem cell-based Parkinson's disease models showing endogenous alpha-synuclein aggregation

After the first research declaring the generation of human induced pluripotent stem cells (hiPSCs) in 2007, several attempts have been made to model neurodegenerative disease in vitro during the past decade. Parkinson’s disease (PD) is the second most common neurodegenerative disorder, which is mainly characterized by motor dysfunction. The formation of unique and filamentous inclusion bodies called Lewy bodies (LBs) is the hallmark of both PD and dementia with LBs. The key pathology in PD is generally considered to be the alpha-synuclein (α-syn) accumulation, although it is still controversial whether this protein aggregation is a cause or consequence of neurodegeneration. In the present work, the recently published researches which recapitulated the α-syn aggregation phenomena in sporadic and familial PD hiPSC models were reviewed. Furthermore, the advantages and potentials of using patient-derived PD hiPSC with focus on α-syn aggregation have been discussed.

Induction of typical and atypical neurogenesis in the adult substantia nigra after mouse embryonic stem cells transplantation

Neurogenesis in the substantia nigra (SN) has been a controversial issue. Here we report that neurogenesis can be induced in the adult rodent SN by transplantation of embryoid body cells (EBCs) derived from mouse embryonic stem cells. The detection of Sox2⁺ dividing (BrdU⁺) putative host neural precursor cells (NPCs) between 1 and 6 days post-transplantation (dpt) supported the neurogenic capacity of the adult SN. In agreement with the awakening of NPCs by EBCs, only host cells from implant-bearing SN were able to generate neurosphere-like aggregates in the presence of Egf and Fgf2. Later, at 15 dpt, a significant number of SN Dcx⁺ neuroblasts were detected. However, a continuous BrdU administration after transplantation showed that only a fraction (about 20-30%) of those host Dcx⁺ progeny derived from dividing cells and few BrdU⁺ cells, some of them NeuN⁺, survived up to 30 dpt. Unexpectedly, 25-30% of Dcx⁺ or Psa-Ncam⁺ cells at 15 dpt displayed astrocytic markers such as Gfap and S100b. Using a genetic lineage tracing strategy, we demonstrated that a large proportion of host Dcx⁺ and/or Tubb3⁺ neuroblasts originated from Gfap⁺ cells. Remarkably, new blood vessels formed in association with the neurogenic process that, when precluded, caused a reduction in neuroblast production. Accordingly, two proteins secreted by EBCs, Fgf2 and Vegf, were able to promote the emergence of Dcx⁺/Psa-Ncam⁺, Tubb3⁺ and NeuN⁺/BrdU⁺ cells in vivo in the absence of EBCs. We propose that the adult SN is a mostly silent neurogenic niche with the ability to generate new neurons by typical and atypical mechanisms.

Intrinsic Immunity Shapes Viral Resistance of Stem Cells

Stem cells are highly resistant to viral infection compared to their differentiated progeny; however, the mechanism is mysterious. Here, we analyzed gene expression in mammalian stem cells and cells at various stages of differentiation. We find that, conserved across species, stem cells express a subset of genes previously classified as interferon (IFN) stimulated genes (ISGs) but that expression is intrinsic, as stem cells are refractory to interferon. This intrinsic ISG expression varies in a cell-type-specific manner, and many ISGs decrease upon differentiation, at which time cells become IFN responsive, allowing induction of a broad spectrum of ISGs by IFN signaling. Importantly, we show that intrinsically expressed ISGs protect stem cells against viral infection. We demonstrate the in vivo importance of intrinsic ISG expression for protecting stem cells and their differentiation potential during viral infection. These findings have intriguing implications for understanding stem cell biology and the evolution of pathogen resistance.

Amelioration of experimentally induced diabetic nephropathy and renal damage by nilotinib

Diabetes mellitus is an ever growing world-wide health problem. The patient has to stick to a firm life-long therapeutic regimen, otherwise diabetic complications will develop. Diabetic nephropathy (DN) is one of the most common diabetic complications and it requires careful medical attendance. Nilotinib hydrochloride is a protein tyrosine kinase inhibitor reported to have numerous therapeutic efficacies besides being an anticancer. In the current study, single I.P. streptozotocin (50 mg/kg) injection was used to induce type I diabetes mellitus in male Sprague-Dawley rats. After 8 weeks, significant deterioration of renal function with urinary excretion of nephrin, podocalyxin, and albumin was observed. Daily oral administration of nilotinib (20 mg/kg) for 8 weeks significantly improved signs of DN on all investigated scales. On a biochemical scale, kidney functions, albuminuria, urinary nephrin, podocalyxin excretion, and host oxidant/antioxidant balance significantly improved. Kidney content of nitric oxide, expression of toll-like receptors 4 and NF-κB/p65 activity significantly declined as well. On a histopathological scale, α-smooth muscle actin and nestin expression significantly declined. Meanwhile, area of fibrosis significantly declined as seen with significant reduction in accumulation of extracellular matrix components and kidney content of collagen. Ultimately, such improvements were accompanied by significant restoration of normal kidney physiology and function. In conclusion, nilotinib can hinder progression of DN through various mechanisms. Reduction of oxidative stress, enhancement of host antioxidant defense system, reduction of inflammation, angiogenesis, tissue hypoxia, and pro-fibrogenic biomarker expression can be implicated in the beneficial therapeutic outcome observed with nilotinib therapy.

Bioengineered fibrin-based niche to direct outgrowth of circulating progenitors into neuron-like cells for potential use in cellular therapy

OBJECTIVE

Autologous cells are considered to be the best choice for use in transplantation therapy. However, the challenges and risks associated with the harvest of transplantable autologous cells limit their successful therapeutic application. The current study explores the possibility of isolating neural progenitor cells from circulating multipotent adult progenitor cells for potential use in cell-based and patient-specific therapy for neurological diseases.

APPROACH

To enable the selection of neural progenitor cells from human peripheral blood mononuclear cells, and to support their lineage maintenance, the composition of a fibrin-based niche was optimized. Morphological examination and specific marker analysis were carried out, employing a qualitative/quantitative polymerase chain reaction followed by immunocytochemistry to: (i) characterize neural progenitor cells in culture; (ii) monitor proliferation/survival; and (iii) track their differentiation status.

MAIN RESULTS

The presence of neural progenitors in circulation was confirmed by the presence of nestin(+) cells at the commencement of the culture. The isolation, proliferation and differentiation of circulating neural progenitors to neuron-like cells were directed by the engineered niche. Neural cell isolation to near homogeneity was confirmed by the expression of β-III tubulin in ∼95% of cells, whereas microtubule associated protein-2 expression confirmed their ability to differentiate. The concentration of potassium chloride in the niche was found to favour neuron-like cell lengthening, cell-cell contact, and expressions of synaptophysin and tyrosine hydroxylase.

SIGNIFICANCE

The purpose of this research was to find out if peripheral blood could serve as a potential source of neural progenitors for cell based therapy. The study established that neural progenitors could be selectively isolated from peripheral blood mononuclear cells using a biomimetic niche. The selected cells could multiply and slowly differentiate into neuron-like cells. These neuron-like cells expressed functional proteins-tyrosine hydroxylase and synaptophysin. Early progenitors that proliferate while expressing β-III tubulin could be harvested from the culture, suggesting their potential use in cell transplantation therapy.

Intrauterine Growth Restriction: Effects on Neural Precursor Cell Proliferation and Angiogenesis in the Foetal Subventricular Zone

Exposure to adverse prenatal factors can result in abnormal brain development, contributing to the aetiology of several neurological disorders. Intrauterine insults could occur during neurogenesis and gliogenesis, disrupting these events. Here we investigate the effects of chronic placental insufficiency (CPI) on cell proliferation and the microenvironment in the subventricular zone (SVZ). At 30 days of gestation (DG; term ∼67 DG), CPI was induced in pregnant guinea pigs via unilateral uterine artery ligation to produce growth-restricted (GR) foetuses (n = 7); controls (n = 6) were from the unoperated horn. At 60 DG, foetal brains were stained immunohistochemically to identify proliferating cells (Ki67), immature neurons (polysialylated neuronal cell adhesion molecule), astrocytes (glial fibrillary acidic protein), microglia (ionised calcium-binding adaptor molecule-1, Iba-1) and the microvasculature (von Willebrand factor) in the SVZ. There was no overall difference (p > 0.05) in the total number of Ki67-immunoreactive (IR) cells, the percentage of SVZ occupied by blood vessels or the density of Iba-1-IR microglia in control versus GR foetuses. However, regression analysis across both groups revealed that both the number of Ki67-IR cells and the percentage of SVZ occupied by blood vessels in the ventral SVZ were negatively correlated (p < 0.05) with brain weight. Furthermore, in the SVZ (dorsal and ventral) the density of blood vessels positively correlated (p < 0.05) with the number of Ki67-IR cells. Double-labelling immunofluorescence suggested that the majority of proliferating cells were likely to be neural precursor cells. Thus, we have demonstrated an association between angiogenesis and neurogenesis in the foetal neurogenic niche and have identified a window of opportunity for the administration of trophic support to enhance a neuroregenerative response.

Prosurvival factors derived from the embryonic brain promote adult neural stem cell survival

Temporally distinct populations of neural stem cells (NSCs; embryonic and adult) display the cardinal stem cell properties of self-renewal and multipotentiality; however, their relative frequency and cell kinetics vary through development and into old age. We asked whether changes in NSC behavior could be accounted for by changes in environmental signals over time. We identified a prosurvival signaling cascade that enhances adult-derived NSC survival using cues released from embryonic neurons. Specifically, we demonstrate that stromal-cell-derived factor-1α (SDF-1α) released by embryonic neurons leads to upregulation of neuronal nitric oxide synthase in adult neural precursor cells. The resulting increase in nitric oxide leads to the upregulation of the stem cell factor (SCF) receptor ckit on adult NSCs (ANSCs). SCF released from embryonic neurons results in enhanced NSC survival. Using both in vitro and in vivo assays, we have demonstrated expansion of the size of the NSC pool through this pathway, indicating that ANSCs retain their ability to respond to embryonic-derived cues into adulthood.

Changes in neural stem cells in the subventricular zone in a rat model of communicating hydrocephalus

Communicating hydrocephalus is a common type of hydrocephalus. At present, the prevalent treatment is to perform a ventriculo-peritoneal shunt, which, for reasons that are not clear, is sometimes ineffective. The subventricular zone (SVZ) of the lateral ventricles has been established as the primary site of adult neurogenesis. Following cerebral ischemia or brain injury, neural stem cells (NSCs) increase in the SVZ and can both differentiate into neurons and glial cells and respond to the injury. Neural stem cells, enabled by a complex repertoire of factors that precisely regulate the activation, proliferation, differentiation and integration of newborn cells, continuously generate new neurons. However, only a few systematic studies of the role of NSCs in hydrocephalus have been reported. In a rat model of communicating hydrocephalus, we recently showed that hydrocephalus caused the ventricular system to expand over time. We found that the number of NSCs in the SVZ peaked rapidly after hydrocephalus was established and decreased gradually over time until the cells disappeared. NSCs may be involved in the pathophysiology changes and repair process of hydrocephalus.

Solving the puzzle of Parkinson's disease using induced pluripotent stem cells

The prevalence and incidence of Parkinson's disease (PD) is increasing due to a prolonged life expectancy. This highlights the need for a better mechanistic understanding and new therapeutic approaches. However, traditional in vitro and in vivo experimental models to study PD are suboptimal, thus hampering the progress in the field. The epigenetic reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) offers a unique way to overcome this problem, as these cells share many properties of embryonic stem cells (ESCs) including the potential to be transformed into different lineages. PD modeling with iPSCs is nowadays facilitated by the growing availability of high-efficiency neural-specific differentiation protocols and the possibility to correct or induce mutations as well as creating marker cell lines using designer nucleases. These technologies, together with steady advances in human genetics, will likely introduce profound changes in the way we interpret PD and develop new treatments. Here, we summarize the different PD iPSCs reported so far and discuss the challenges for disease modeling using these cell lines.

Brain homeostasis: VEGF receptor 1 and 2-two unequal brothers in mind

Vascular endothelial growth factors (VEGFs), initially thought to act specifically on the vascular system, exert trophic effects on neural cells during development and adulthood. Therefore, the VEGF system serves as a promising therapeutic target for brain pathologies, but its simultaneous action on vascular cells paves the way for harmful side effects. To circumvent these deleterious effects, many studies have aimed to clarify whether VEGFs directly affect neural cells or if the effects are mediated secondarily via other cell types, like vascular cells. A great number of reports have shown the expression and function of VEGF receptors (VEGFRs), mainly VEGFR-1 and -2, in neural cells, where VEGFR-2 has been described as the major mediator of VEGF-A signals. This review aims to summarize and compare the divergent roles of VEGFR-1 and -2 during CNS development and homeostasis.

Nestin: A novel angiogenesis marker and possible target for tumor angiogenesis

Abnormal vasculature, termed tumor vessels, is a hallmark of solid tumors. The degree of angiogenesis is associated with tumor aggressiveness and clinical outcome. Therefore, exact quantification of tumor vessels is useful to evaluate prognosis. Furthermore, selective detection of newly formed tumor vessels within cancer tissues using specific markers raises the possibility of molecular targeted therapy via the inhibition of tumor angiogenesis. Nestin, an intermediate filament protein, is reportedly expressed in repair processes, various neoplasms, and proliferating vascular endothelial cells. Nestin expression is detected in endothelial cells of embryonic capillaries, capillaries of the corpus luteum, which replenishes itself by angiogenesis, and proliferating endothelial progenitor cells, but not in mature endothelial cells. Therefore, expression of nestin is relatively limited to proliferating vascular endothelial cells and endothelial progenitor cells. Nestin expression is also reported in blood vessels within glioblastoma, prostate cancer, colorectal cancer, and pancreatic cancer, and its expression is more specific for newly formed blood vessels than other endothelial cell markers. Nestin-positive blood vessels form smaller vessels with high proliferation activity in tumors. Knockdown of nestin in vascular endothelial cells suppresses endothelial cell growth and tumor formation ability of pancreatic cancers in vivo. Using nestin to more accurately evaluate microvessel density in cancer specimens may be a novel prognostic indicator. Furthermore, nestin-targeted therapy may suppress tumor proliferation via inhibition of angiogenesis in numerous malignancies, including pancreatic cancer. In this review article, we focus on nestin as a novel angiogenesis marker and possible therapeutic target via inhibition of tumor angiogenesis.

Modeling neurogenesis impairment in Down syndrome with induced pluripotent stem cells from Trisomy 21 amniotic fluid cells

Down syndrome (DS), or Trisomy 21 (T21) syndrome, one of the most common chromosomal abnormalities, is caused by an extra duplication of chromosome 21. In studies of neuron development, experimental models based on human cells are considered to be the most desired and accurate for basic research. The generation of diseased induced pluripotetn stem (iPS) cell is a critical step in understanding the developmental stages of complex neuronal diseases. Here, we generated human DS iPS cell lines from second trimester amniotic fluid (AF) cells with T21 by co-expressing Yamanaka factors through lentiviral delivery and subsequently differentiated them into neuronal progenitor cells (NPCs) for further analyses. T21 AF-iPS cells were characterized for the expression of pluripotent markers and for their ability to differentiate into all three germ layers by forming embryoid bodies in vitro and teratomas in vivo. The T21 AF-iPS cells maintained their unique pattern of chromosomal karyotypes: three pairs of chromosome 21. The level of amyloid precursor protein was significantly increased in NPCs derived from T21 AF-iPS cells compared with NPCs from normal AF-iPS cells. The expression levels of miR-155 and miR-802 in T21 AF-iPS-NPCs were highly elevated in the presence of low expression of MeCP2. We observed that T21 iPS-NPCs generated fewer neurons compared with controls. T21 iPS-NPCs exhibit developmental defects during neurogenesis. Our findings suggest that T21 AF-iPS cells serve as a good source to further elucidate the impairment neurogenesis of DS and the onset of Alzheimer's disease.

Subventricular zone microglia transcriptional networks

Microglia play an important role in inflammatory diseases of the central nervous system. There is evidence of microglial diversity with distinct phenotypes exhibiting either neuroprotection and repair or neurotoxicity. However the precise molecular mechanisms underlying this diversity are still unknown. Using a model of experimental autoimmune encephalomyelitis (EAE) we performed transcriptional profiling of isolated subventricular zone microglia from the acute and chronic disease phases of EAE. We found that microglia exhibit disease phase specific gene expression signatures, that correspond to unique gene ontology functions and genomic networks. Our data demonstrate for the first time, distinct transcriptional networks of microglia activation in vivo, that suggests a role as mediators of injury or repair.

Evolution of the VEGF-regulated vascular network from a neural guidance system

The vascular network is closely linked to the neural system, and an interdependence is displayed in healthy and in pathophysiological responses. How has close apposition of two such functionally different systems occurred? Here, we present a hypothesis for the evolution of the vascular network from an ancestral neural guidance system. Biological cornerstones of this hypothesis are the vascular endothelial growth factor (VEGF) protein family and cognate receptors. The primary sequences of such proteins are conserved from invertebrates, such as worms and flies that lack discernible vascular systems compared to mammals, but all these systems have sophisticated neuronal wiring involving such molecules. Ancestral VEGFs and receptors (VEGFRs) could have been used to develop and maintain the nervous system in primitive eukaryotes. During evolution, the demands of increased morphological complexity required systems for transporting molecules and cells, i.e., biological conductive tubes. We propose that the VEGF-VEGFR axis was subverted by evolution to mediate the formation of biological tubes necessary for transport of fluids, e.g., blood. Increasingly, there is evidence that aberrant VEGF-mediated responses are also linked to neuronal dysfunctions ranging from motor neuron disease, stroke, Parkinson's disease, Alzheimer's disease, ischemic brain disease, epilepsy, multiple sclerosis, and neuronal repair after injury, as well as common vascular diseases (e.g., retinal disease). Manipulation and correction of the VEGF response in different neural tissues could be an effective strategy to treat different neurological diseases.

Patterns of tooth agenesis in patients with Down syndrome in relation to hypothyroidism and congenital heart disease: an aid for treatment planning

INTRODUCTION

The purposes of this study were to investigate the patterns of tooth agenesis (oligodontia and nonoligodontia), maxillary canine impaction, and tooth transposition in subjects with Down syndrome and to determine whether congenital heart disease and hypothyroidism are parameters in tooth agenesis.

METHODS

The study included 114 patients with Down syndrome. The data were quantified by using standardized records, clinical examinations, panoramic radiographs, and solo roentgenograms. The subjects were differentiated into oligodontia (6 or more teeth missing) and nonoligodontia (5 or fewer teeth missing).

RESULTS

In these patients with Down syndrome, 59.6% had missing teeth. Those in the nonoligodontia group showed a tendency toward a negative correlation between congenital heart disease and agenesis (P = 0.093; odds ratio = 0.49) but a slight positive correlation between hypothyroidism and agenesis (P = 0.060; odds ratio = 3.71). In the oligodontia group, there was a quantitatively and qualitatively different pattern, indicating another phenotype. When both mandibular central incisors were missing, there was a remarkable chance for oligodontia (P = 0.001; odds ratio = 38.8). In the mandible, symmetrical agenesis of the canines and lateral incisors was more frequent in the nonoligodontia group.

CONCLUSIONS

The oligodontia (with a different phenotype) and nonoligodontia groups had different patterns of agenesis. Maxillary canine impaction was not related to absence of the lateral incisors. Absence of both mandibular central incisors was a high predictor for oligodontia. Congenital heart disease and hypothyroidism are parameters involved in tooth agenesis.

Effect of VEGF on neural differentiation of human embryonic stem cells in vitro

The effects of vascular endothelial growth factor (VEGF) on neural differentiation of human embryonic stem cells (hESCs) in vitro and the possible mechanism were observed. The hESCs lines, TJMU1 and TJMU2, were established and stored by our laboratory. hESCs differentiated into neuronal cells through embryonic body formation. In this induction process, hESCs were divided into three groups: group A, routine induction; group B, routine induction+10 ng/mL VEGF; group C, routine induction+10 ng/mL VEGF+10 ng/mL VEGFR2/Fc. OCT4, Nestin and GFAP in each group were detected by RT-PCR, and the cells expressing Nestin and GFAP were counted by immunofluorescence. The percentage of Nestin positive cells in group B was significantly higher than in groups A and C, while the percentage of GFAP positive cells in group B was significantly lower than in groups A and C (P<0.01). There was no significant difference between groups A and C (P>0.05). It was concluded that VEGF, via VEGFR2, stimulated the neural differentiation of hESCs in vitro.

Human neural stem cell transplantation attenuates apoptosis and improves neurological functions after cerebral ischemia in rats

BACKGROUND

Neuroprotection is a major therapeutic approach for ischemic brain injury. We investigated the neuroprotective effects induced by transplantation of human embryonic neural stem cells (NSCs) into the cortical penumbra 24 h after focal cerebral ischemia.

METHODS

NSCs were prepared from human embryonic brains obtained at 8 weeks of gestation. Focal cerebral ischemia was induced in adult rats by permanent occlusion of the middle cerebral artery. Animals were randomly divided into two groups: NSCs-grafted group and medium-grafted group (control). Infarct size was assessed 28 days after transplantation by hematoxylin and eosin staining. Neurological severity scores were evaluated before ischemia and at 1, 7, 14, and 28 days after transplantation. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and immunohistochemical analysis of Bcl-2 and Bax were performed at 7, 14, and 28 days after transplantation.

RESULTS

Physiological parameters of the two groups were comparable, but not significantly different. NSC transplantation significantly improved neurological function (P<0.05) but did not reduce the infarct size significantly (P>0.05). Compared with the control, NSC transplantation significantly reduced the number of TUNEL- and Bax-positive cells in the penumbra at 7 days. Interestingly, the number of Bcl-2-positive cells in the penumbra after NSC transplantation was significantly higher than that after medium transplantation (P<0.05).

CONCLUSIONS

The results indicate that NSC transplantation has anti-apoptotic activity and can improve the neurological function; these effects are mediated by the up-regulation of Bcl-2 expression in the penumbra.

Differential cytotoxic effects of mono-(2-ethylhexyl) phthalate on blastomere-derived embryonic stem cells and differentiating neurons

Potential applications of embryonic stem (ES) cells are not limited to regenerative medicine but can also include in vitro screening of various toxicants. In this study, we established mouse ES cell lines from isolated blastomeres of two-cell stage embryos and examined their potential use as an in vitro system for the study of developmental toxicity. Two ES cell lines were established from 69 blastomere-derived blastocysts (2.9%). The blastomere-derived ES (bm-ES) cells were treated with mono-(2-ethylhexyl) phthalate (MEHP) in an undifferentiated state or after directed differentiation into early neural cell types. We observed significantly decreased cell viability when undifferentiated bm-ES cells were exposed to a high dose of MEHP (1000 microM). The cytotoxic effects of MEHP were accompanied by increased DNA fragmentation, nuclear condensation, and activation of Caspase-3, which are biochemical and morphological features of apoptosis. Compared to undifferentiated bm-ES cells, considerably lower doses of MEHP (50 and 100 microM) were sufficient to induce cell death in early neurons differentiated from bm-ES cells. At the lower doses, the number of neural cells positive for the active form of Caspase-3 was greater than that for undifferentiated bm-ES cells. Thus, our data indicate that differentiating neurons are more sensitive to MEHP than undifferentiated ES cells, and that undifferentiated ES cells may have more efficient defense systems against cytotoxic stresses. These findings might contribute to the development of a new predictive screening method for assessment of hazards for developmental toxicity.

VEGFR-1 regulates adult olfactory bulb neurogenesis and migration of neural progenitors in the rostral migratory stream in vivo

The generation of new neurons in the olfactory bulb (OB) persists into adulthood and is a multistep process that includes proliferation, fate choice, migration, survival, and differentiation. Neural precursor cells destined to form olfactory interneurons arise in the subventricular zone (SVZ) and migrate along the rostral migratory stream (RMS) to the OB. Recently, some factors classically known from their effects on the vascular system have been found to influence different steps of adult neurogenesis. In the present study, we report a modulatory function for the vascular endothelial growth factor receptor-1 (VEGFR-1) in adult olfactory neurogenesis. We identified expression of VEGFR-1 in GFAP-positive cells within regions involved in neurogenesis of the adult mouse brain. To determine functions for VEGFR-1 in adult neurogenesis, we compared neural progenitor cell proliferation, migration, and differentiation from wild-type and VEGFR-1 signaling-deficient mice (Flt-1TK(-/-) mice). Our data show that VEGFR-1 signaling is involved in the regulation of proliferation of neuronal progenitor cells within the SVZ, migration along the RMS, and in neuronal differentiation and anatomical composition of interneuron subtypes within the OB. RMS migration in Flt-1TK(-/-) mice was altered mainly as a result of increased levels of its ligand VEGF-A, which results in an increased phosphorylation of VEGFR-2 in neuronal progenitor cells within the SVZ and the RMS. This study reveals that proper RMS migration is dependent on endogenous VEGF-A protein.

Role and therapeutic potential of VEGF in the nervous system

The development of the nervous and vascular systems constitutes primary events in the evolution of the animal kingdom; the former provides electrical stimuli and coordination, while the latter supplies oxygen and nutrients. Both systems have more in common than originally anticipated. Perhaps the most striking observation is that angiogenic factors, when deregulated, contribute to various neurological disorders, such as neurodegeneration, and might be useful for the treatment of some of these pathologies. The prototypic example of this cross-talk between nerves and vessels is the vascular endothelial growth factor or VEGF. Although originally described as a key angiogenic factor, it is now well established that VEGF also plays a crucial role in the nervous system. We describe the molecular properties of VEGF and its receptors and review the current knowledge of its different functions and therapeutic potential in the nervous system during development, health, disease and in medicine.

Parkinson's disease patient-derived induced pluripotent stem cells free of viral reprogramming factors

Induced pluripotent stem cells (iPSCs) derived from somatic cells of patients represent a powerful tool for biomedical research and may provide a source for replacement therapies. However, the use of viruses encoding the reprogramming factors represents a major limitation of the current technology since even low vector expression may alter the differentiation potential of the iPSCs or induce malignant transformation. Here, we show that fibroblasts from five patients with idiopathic Parkinson's disease can be efficiently reprogrammed and subsequently differentiated into dopaminergic neurons. Moreover, we derived hiPSCs free of reprogramming factors using Cre-recombinase excisable viruses. Factor-free hiPSCs maintain a pluripotent state and show a global gene expression profile, more closely related to hESCs than to hiPSCs carrying the transgenes. Our results indicate that residual transgene expression in virus-carrying hiPSCs can affect their molecular characteristics and that factor-free hiPSCs therefore represent a more suitable source of cells for modeling of human disease.

Vitronectin promotes oligodendrocyte differentiation during neurogenesis of human embryonic stem cells

We demonstrate enhanced differentiation of oligodendrocytes during neurogenesis of human embryonic stem cells (hESCs) using an extracellular matrix protein, vitronectin (VN). We show that VN is expressed in the ventral part of the developing human spinal cord. Combined treatment of retinoic acid, sonic hedgehog, and noggin in the presence of VN allows hESCs to differentiate into O4-positive oligodendrocytes. Particularly, VN profoundly promotes the derivation of oligodendrocyte progenitors that proliferate and differentiate into oligodendrocytes in response to mitogenic and survival factors. These results support the beneficial effect of VN on oligodendrocytic differentiation of hESCs.

Enhanced co-expression of beta-tubulin III and choline acetyltransferase in neurons from mouse embryonic stem cells promoted by icaritin in an estrogen receptor-independent manner

A previous small molecule screen demonstrated that some prenylflavonoids can promote neuronal differentiation from mouse embryonic stem (ES) cells based on morphologic criteria. Here we build on this observation and examine the neuronal subtypes induced by icaritin, a compound screened, and the molecular events underlying the differentiation. In the presence of icaritin, the number of neural rosettes in embryoid bodies (EBs) expressing nestin efficiently increased and the neuroectodermal gene Fgf5 expression upregulated during germ layer formation. The neural progenitors generated from icaritin-treated EBs were further differentiated into the neurons (marked by beta-tubulin III) and also enhanced the choline acetyltransferase (ChAT) expression upon terminal differentiation. A suppression of p38 mitogen-activated protein kinase (p38MAPK) phosphorylation and sustained extracellular signal-regulated protein kinase (ERK) phosphorylation existed simultaneously without estrogen-like activities involved. Taken together, enhanced co-expression of beta-tubulin III and choline acetyltransferase in neuronal differentiation from mouse ES cells is promoted by icaritin via estrogen receptor-independent action.

Cellular distribution of vascular endothelial growth factor A (VEGFA) and B (VEGFB) and VEGF receptors 1 and 2 in focal cortical dysplasia type IIB

Members of the vascular endothelial growth factor (VEGF) family are key signaling proteins in the induction and regulation of angiogenesis, both during development and in pathological conditions. However, signaling mediated through VEGF family proteins and their receptors has recently been shown to have direct effects on neurons and glial cells. In the present study, we immunocytochemically investigated the expression and cellular distribution of VEGFA, VEGFB, and their associated receptors (VEGFR-1 and VEGFR-2) in focal cortical dysplasia (FCD) type IIB from patients with medically intractable epilepsy. Histologically normal temporal cortex and perilesional regions displayed neuronal immunoreactivity (IR) for VEGFA, VEGFB, and VEGF receptors (VEGFR-1 and VEGFR-2), mainly in pyramidal neurons. Weak IR was observed in blood vessels and there was no notable glial IR within the grey and white matter. In all FCD specimens, VEGFA, VEGFB, and both VEGF receptors were highly expressed in dysplastic neurons. IR in astroglial and balloon cells was observed for VEGFA and its receptors. VEGFR-1 displayed strong endothelial staining in FCD. Double-labeling also showed expression of VEGFA, VEGFB and VEGFR-1 in cells of the microglia/macrophage lineage. The neuronal expression of both VEGFA and VEGFB, together with their specific receptors in FCD, suggests autocrine/paracrine effects on dysplastic neurons. These autocrine/paracrine effects could play a role in the development of FCD, preventing the death of abnormal neuronal cells. In addition, the expression of VEGFA and its receptors in glial cells within the dysplastic cortex indicates that VEGF-mediated signaling could contribute to astroglial activation and associated inflammatory reactions.