Stem-like signatures in human meningioma cells are under the control of CXCL11/CXCL12 chemokine activity

BACKGROUND

Meningiomas are mainly benign brain tumors, although about 20% of histologically benign cases are clinically aggressive and recur after resection. We hypothesize that meningioma brain invasiveness and recurrence may be related to the presence of cancer stem cells and their high responsiveness to the CXCL12-CXCR4/CXCR7 chemokine axis. The aim of this study was to isolate meningioma stem cells from human samples, characterize them for biological features related to malignant behavior, and to identify the role of CXCR4/CXCR7 in these processes.

METHODS

Meningioma stem cells were isolated from patient-derived primary cultures in stem cell-permissive conditions, and characterized for phenotype, self-renewal, proliferation and migration rates, vasculogenic mimicry (VM), and in vivo tumorigenesis, in comparison with differentiated meningioma cells and stem-like cells isolated from normal meninges. These cell populations were challenged with CXCL12 and CXCL11 and receptor antagonists to define the chemokine role in stem cell-related functions.

RESULTS

Stem-like cells isolated from meningioma cultures display higher proliferation and migration rates, and VM, as compared to meningioma non-stem cells or cells isolated from normal meninges and were the only tumorigenic population in vivo. In meningioma cells, these stem-like functions were under the control of the CXCR4/CXCR7 chemokine axis.

CONCLUSIONS

We report a role for CXCL11 and CXCL12 in the control of malignant features in stem-like cells isolated from human meningioma, providing a possible basis for the aggressive clinical behavior observed in subsets of these tumors. CXCR4/CXCR7 antagonists might represent a useful approach for meningioma at high risk of recurrence and malignant progression.

Early clonal extinction in glioblastoma progression revealed by genetic barcoding

Glioblastoma progression in its early stages remains poorly understood. Here, we transfer PDGFB and genetic barcodes in mouse brain to initiate gliomagenesis and enable direct tracing of glioblastoma evolution from its earliest possible stage. Unexpectedly, we observe a high incidence of clonal extinction events and progressive divergence in clonal sizes, even after the acquisition of malignant phenotype. Computational modeling suggests these dynamics result from clonal-based cell-cell competition. Through bulk and single-cell transcriptome analyses, coupled with lineage tracing, we reveal that Myc transcriptional targets have the strongest correlation with clonal size imbalances. Moreover, we show that the downregulation of Myc expression is sufficient to drive competitive dynamics in intracranially transplanted gliomas. Our findings provide insights into glioblastoma evolution that are inaccessible using conventional retrospective approaches, highlighting the potential of combining clonal tracing and transcriptomic analyses in this field.

Genome-wide profiling of patient-derived glioblastoma stem-like cells reveals recurrent genetic and transcriptomic signatures associated with brain tumors

PURPOSE

Patient-derived cancer cell lines can be very useful to investigate genetic as well as epigenetic mechanisms of transformation and to test new drugs. In this multi-centric study, we performed genomic and transcriptomic characterization of a large set of patient-derived glioblastoma (GBM) stem-like cells (GSCs).

METHODS

94 (80 I surgery/14 II surgery) and 53 (42 I surgery/11 II surgery) GSCs lines underwent whole exome and trascriptome analysis, respectively.

RESULTS

Exome sequencing revealed TP53 as the main mutated gene (41/94 samples, 44%), followed by PTEN (33/94, 35%), RB1 (16/94, 17%) and NF1 (15/94, 16%), among other genes associated to brain tumors. One GSC sample bearing a BRAF p.V600E mutation showed sensitivity in vitro to a BRAF inhibitor. Gene Ontology and Reactome analysis uncovered several biological processes mostly associated to gliogenesis and glial cell differentiation, S - adenosylmethionine metabolic process, mismatch repair and methylation. Comparison of I and II surgery samples disclosed a similar distribution of mutated genes, with an overrepresentation of mutations in mismatch repair, cell cycle, p53 and methylation pathways in I surgery samples, and of mutations in receptor tyrosine kinase and MAPK signaling pathways in II surgery samples. Unsupervised hierarchical clustering of RNA-seq data produced 3 clusters characterized by distinctive sets of up-regulated genes and signaling pathways.

CONCLUSION

The availability of a large set of fully molecularly characterized GCSs represents a valuable public resource to support the advancement of precision oncology for the treatment of GBM.

Cardiomyocytes derived small extracellular vesicles plays an important role in heart development

Introduction

Neonatal rats have the capacity to regenerate their hearts in response to injury, but this potential is lost after the first week of life. Cardiac maturation lays the foundation for postnatal heart development and disease, yet little is known about the contributions of the microenvironment to cardiomyocyte maturation.

Extracellular vesicles (EV) are bilayer-membrane nanoparticles released by all cell types, carrying proteins, lipids, and nucleic acids, which reflect the activation state of parental cells. Secreted small extracellular vesicles (sEV), prominently figure among extracellular signals that regulate cell function.

Purpose

We aim to determine whether cardiomyocyte (CM) derived sEV carried miRNA that has a role in heart development with specific regards to cardiomyocyte maturation.

Methods

sEV were isolated from rat cardiomyocyte at day 0 and 7 after birth by serial ultracentrifugation. sEV were characterized by NTA and analyzed by Western blot for the presence of classical EV markers (TSG101, Syntenin-1). The role of sEV in cardiomyocyte proliferation was assessed by analysis of EdU incorporation on neoantal rat CM treated with sEV_p0 or sEV_p7. miRNA content on sEV was assessed using a rat-miRNome MicroRNA Profiling Kit and the identified miRNA's targets confirmed by RealTime-PCR and Western Blot.

Results

NTA and Western Blot analysis confirmed the presence of sEV in both the extracellular vesicles preparation. sEV_p0 showed to be able to sligtly increase EdU incorporation in treated cardiomyocyte (1.15-Fold) while sEV_p7 significantly inihibit CM proliferation (0.78-Fold) toghether with a change in cardiomyocyte citoscheletal architecture. Data from miRNome analysis showed in sEV_p7 a significan increase in miRNA with cyclines as tagets. Downregulation of Cdk1; Cdk4; Cdk2; CcnB1 and CcnD1 was confirmed on CM trated with sEV_p7 compared to Ctrl. Downregulation of CCND1 was aslo confrmed at the protein level by Western Blot analysis.

Conclusions

These preliminary resultes showed an important role in heart develompent of cardiomyocyte derived-sEV. A deeper investigation of the pathaway activated by sEV may have a potential interest for the identification of possible regulators for stimulating heart regeneration.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Fondazione Leonardo, Lugano, Switzerland

D-aspartate oxidase gene duplication induces social recognition memory deficit in mice and intellectual disabilities in humans

The D-aspartate oxidase (DDO) gene encodes the enzyme responsible for the catabolism of D-aspartate, an atypical amino acid enriched in the mammalian brain and acting as an endogenous NMDA receptor agonist. Considering the key role of NMDA receptors in neurodevelopmental disorders, recent findings suggest a link between D-aspartate dysmetabolism and schizophrenia. To clarify the role of D-aspartate on brain development and functioning, we used a mouse model with constitutive Ddo overexpression and D-aspartate depletion. In these mice, we found reduced number of BrdU-positive dorsal pallium neurons during corticogenesis, and decreased cortical and striatal gray matter volume at adulthood. Brain abnormalities were associated with social recognition memory deficit at juvenile phase, suggesting that early D-aspartate occurrence influences neurodevelopmental related phenotypes. We corroborated this hypothesis by reporting the first clinical case of a young patient with severe intellectual disability, thought disorders and autism spectrum disorder symptomatology, harboring a duplication of a chromosome 6 region, including the entire DDO gene.

Investigating the Paracrine Role of Perinatal Derivatives: Human Amniotic Fluid Stem Cell-Extracellular Vesicles Show Promising Transient Potential for Cardiomyocyte Renewal

Cardiomyocyte renewal represents an unmet clinical need for cardiac regeneration. Stem cell paracrine therapy has attracted increasing attention to resurge rescue mechanisms within the heart. We previously characterized the paracrine effects that human amniotic fluid–derived stem cells (hAFSC) can exert to provide cardioprotection and enhance cardiac repair in preclinical models of myocardial ischemia and cardiotoxicity. Here, we analyze whether hAFSC secretome formulations, namely, hAFSC conditioned medium (hAFSC-CM) over extracellular vesicles (hAFSC-EVs) separated from it, can induce cardiomyocyte renewal. c-KIT+ hAFSC were obtained by leftover samples of II trimester prenatal amniocentesis (fetal hAFSC) and from clinical waste III trimester amniotic fluid during scheduled C-section procedures (perinatal hAFSC). hAFSC were primed under 1% O₂ to enrich hAFSC-CM and EVs with cardioactive factors. Neonatal mouse ventricular cardiomyocytes (mNVCM) were isolated from cardiac tissue of R26pFUCCI2 mice with cell cycle fluorescent tagging by mutually exclusive nuclear signal. mNVCM were stimulated by fetal versus perinatal hAFSC-CM and hAFSC-EVs to identify the most promising formulation for in vivo assessment in a R26pFUCCI2 neonatal mouse model of myocardial infarction (MI) via intraperitoneal delivery. While the perinatal hAFSC secretome did not provide any significant cardiogenic effect, fetal hAFSC-EVs significantly sustained mNVCM transition from S to M phase by 2-fold, while triggering cytokinesis by 4.5-fold over vehicle-treated cells. Treated mNVCM showed disorganized expression of cardiac alpha-actinin, suggesting cytoskeletal re-arrangements prior to cell renewal, with a 40% significant downregulation of Cofilin-2 and a positive trend of polymerized F-Actin. Fetal hAFSC-EVs increased cardiomyocyte cell cycle progression by 1.8-fold in the 4-day-old neonatal left ventricle myocardium short term after MI; however, such effect was lost at the later stage. Fetal hAFSC-EVs were enriched with a short isoform of Agrin, a mediator of neonatal heart regeneration acting by YAP-related signaling; yet in vitro application of YAP inhibitor verteporfin partially affected EV paracrine stimulation on mNVCM. EVs secreted by developmentally juvenile fetal hAFSC can support cardiomyocyte renewal to some extension, via intercellular conveyance of candidates possibly involving Agrin in combination with other factors. These perinatal derivative promising cardiogenic effects need further investigation to define their specific mechanism of action and enhance their potential translation into therapeutic opportunity.

Human amniotic fluid stem cell-extracellular vesicles as paracrine candidates to rejuvenate cardiomyocyte renewal

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): University of Genova

Background

Reactivation of cardiomyocyte renewal represents a milestone for cardiac regeneration. While broadly active in the early neonatal mammalian myocardium, such mechanism is lost soon after birth, with transition to defective repair. We previously showed that human amniotic fluid stem cells (hAFS) possess cardioprotective and cardioactive paracrine potential in a preclinical adult mouse model of myocardial infarction (MI)1, by sustaining cardiomyocyte cell cycle re-entry up to DNA duplication.

Purpose

Here we analyse whether hAFS secretome formulations, namely hAFS-conditioned medium (hAFS-CM) over extracellular vesicles (hAFS-EVs) separated from that, can enhance cardiomyocyte renewal in vitro and in vivo.

Methods

hAFS were obtained by leftover samples of prenatal screening amniocentesis and primed under 1% O2 preconditioning to enrich hAFS-CM and hAFS-EVs with cardioactive factors. hAFS-EVs were concentrated from hAFS-CM by serial ultracentrifugation. hAFS-EVs were profiled by electron microscopy, nanoparticle tracking analysis, proteomics and RNA sequencing (RNAseq). Neonatal mouse ventricular cardiomyocytes (mNVCM) were enzymatically isolated from R26pFUCCI2 mice with fluorescent tagging of cell-cycle by nuclear signal (G1-phase by Cdt1-mCherry; S-G2-M-phases by Geminin-mVenus1)2. mNVCM were stimulated by hAFS-CM or hAFS-EVs to identify the most promising formulation for further analysis in a R26pFUCCI2 4-day-old MI mouse model via intra-peritoneal delivery, according to principles of laboratory animal care and in compliance with authorization from the Italian Ministry of Health.

Results

hAFS-EVs sustained R26pFUCCI2 mNVCM transition from S- to M-phase by 2.1-fold (*p<0.05) in vitro, while triggering cytokinesis by 4.5-fold (*p<0.05) increase by Aurora B kinase expression at midbodies. Treated mNVCM showed disorganized expression of cardiac α-actinin, suggesting cytoskeletal re-arrangements prior to cell renewal, with significant down-regulation (0.6-fold, ****p<0.0001) of Cofilin-2 (CFL-2) an actin cytoskeleton regulator antagonizing cardiomyocyte proliferation3. RNAseq on hAFS-EVs revealed some of the mostly enriched microRNAs (miRNAs) targeting CFL-2 (miR-93-5p; miR-152-3p; miR-200b-3p; miR-429; miR-199a-3p; miR-20a-5p; miR-425-5p), while proteomics reported enrichment of a secreted form of Agrin, an important mediator for neonatal heart regeneration4. hAFS-EVs increased cardiomyocyte S- to M phase transition by 1.8-fold (*p<0.05) in the mouse neonatal left ventricle 3 days post-MI.

Conclusions

Our current findings suggest that EVs secreted by developmentally juvenile hAFS may be endowed with relevant potential to support cardiomyocyte renewal for future paracrine therapy in regenerative medicine with putative molecular candidate(s) of action in their cargo content including Agrin and non-coding miRNAs.

Cardiomyocytes (CM) derived small Extracellular Vesicles (sEV) plays an important role in heart development

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Schweizerische Herzstiftung - FF21017

Fondazione Leonardo

Introduction

Neonatal rats have the capacity to regenerate their hearts in response to injury, but this potential is lost after the first week of life. Cardiac maturation lays the foundation for postnatal heart development and disease, yet little is known about the contributions of the microenvironment to cardiomyocyte maturation.

Extracellular vesicles (EV) are bilayer-membrane nanoparticles released by all cell types, carrying proteins, lipids, and nucleic acids, which reflect the activation state of parental cells. Secreted small extracellular vesicles (sEV), prominently figure among extracellular signals that regulate cell function.

Purpose

We aim to determine whether cardiomyocyte (CM) derived sEV carried miRNA that has a role in heart development with specific regards to cardiomyocyte maturation.

Methods

sEV were isolated from rat cardiomyocyte at day 0 and 7 after birth by serial ultracentrifugation. sEV were characterized by NTA and analyzed by Western blot for the presence of classical EV markers (TSG101, Syntenin-1). The role of sEV in cardiomyocyte proliferation was assesed by analysis of EdU incorporation on neoantal rat CM treated with sEV_p0 or sEV_p7. miRNA content on sEV was assesed using a rat-miRNome MicroRNA Profiling Kit and the identified miRNA's targets confirmed by RealTime-PCR and Western Blot.

Results

NTA and Western Blot analysis confirmed the presence of sEV in both the extracellular vesicles preparation. sEV_p0 showed to be able to sligtly increase EdU incorporation in treated cardiomyocyte (1.15-Fold) while sEV_p7 significantly inihibit CM proliferation (0.78-Fold) toghether with a change in cardiomyocyte citoscheletal architecture. Data from miRNome analysis showed in sEV_p7 a significan increase in miRNA with cyclines as tagets. Downregulation of Cdk1 ; Cdk4 ; Cdk2 ; CcnB1 and CcnD1 was confirmed on CM trated with sEV_p7 compared to Ctrl. Downregulation of CCND1 was aslo confrmed at the protein level by Western Blot analysis.

Conclusions

These preliminary resultes showed an important role in heart develompent of cardiomyocyte derived-sEV. A deeper investigation of the pathaway activated by sEV may have a potential interest for the identification of possible regulators for stimulating heart regeneration.

Chloride intracellular channel 1 activity is not required for glioblastoma development but its inhibition dictates glioma stem cell responsivity to novel biguanide derivatives

Background

Chloride intracellular channel-1 (CLIC1) activity controls glioblastoma proliferation. Metformin exerts antitumor effects in glioblastoma stem cells (GSCs) inhibiting CLIC1 activity, but its low potency hampers its translation in clinical settings.

Methods

We synthesized a small library of novel biguanide-based compounds that were tested as antiproliferative agents for GSCs derived from human glioblastomas, in vitro using 2D and 3D cultures and in vivo in the zebrafish model. Compounds were compared to metformin for both potency and efficacy in the inhibition of GSC proliferation in vitro (MTT, Trypan blue exclusion assays, and EdU labeling) and in vivo (zebrafish model), migration (Boyden chamber assay), invasiveness (Matrigel invasion assay), self-renewal (spherogenesis assay), and CLIC1 activity (electrophysiology recordings), as well as for the absence of off-target toxicity (effects on normal stem cells and toxicity for zebrafish and chick embryos).

Results

We identified Q48 and Q54 as two novel CLIC1 blockers, characterized by higher antiproliferative potency than metformin in vitro, in both GSC 2D cultures and 3D spheroids. Q48 and Q54 also impaired GSC self-renewal, migration and invasion, and displayed low systemic in vivo toxicity. Q54 reduced in vivo proliferation of GSCs xenotransplanted in zebrafish hindbrain. Target specificity was confirmed by recombinant CLIC1 binding experiments using microscale thermophoresis approach. Finally, we characterized GSCs from GBMs spontaneously expressing low CLIC1 protein, demonstrating their ability to grow in vivo and to retain stem-like phenotype and functional features in vitro. In these GSCs, Q48 and Q54 displayed reduced potency and efficacy as antiproliferative agents as compared to high CLIC1-expressing tumors. However, in 3D cultures, metformin and Q48 (but not Q54) inhibited proliferation, which was dependent on the inhibition dihydrofolate reductase activity.

Conclusions

These data highlight that, while CLIC1 is dispensable for the development of a subset of glioblastomas, it acts as a booster of proliferation in the majority of these tumors and its functional expression is required for biguanide antitumor class-effects. In particular, the biguanide-based derivatives Q48 and Q54, represent the leads to develop novel compounds endowed with better pharmacological profiles than metformin, to act as CLIC1-blockers for the treatment of CLIC1-expressing glioblastomas, in a precision medicine approach.

A eutherian-specific microRNA controls the translation of Satb2 in a model of cortical differentiation

Cerebral cortical development is controlled by key transcription factors that specify the neuronal identities in the different layers. The mechanisms controlling their expression in distinct cells are only partially known. We investigated the expression and stability of Tbr1, Bcl11b, Fezf2, Satb2, and Cux1 mRNAs in single developing mouse cortical cells. We observe that Satb2 mRNA appears much earlier than its protein and in a set of cells broader than expected, suggesting an initial inhibition of its translation, subsequently released during development. Mechanistically, Satb2 3'UTR modulates protein translation of GFP reporters during mouse corticogenesis. We select miR-541, a eutherian-specific miRNA, and miR-92a/b as the best candidates responsible for SATB2 inhibition, being strongly expressed in early and reduced in late progenitor cells. Their inactivation triggers robust and premature SATB2 translation in both mouse and human cortical cells. Our findings indicate RNA interference as a major mechanism in timing cortical cell identities.

Comprehensive Profiling of Secretome Formulations from Fetal- and Perinatal Human Amniotic Fluid Stem Cells

We previously reported that c-KIT+ human amniotic-fluid derived stem cells obtained from leftover samples of routine II trimester prenatal diagnosis (fetal hAFS) are endowed with regenerative paracrine potential driving pro-survival, anti-fibrotic and proliferative effects. hAFS may also be isolated from III trimester clinical waste samples during scheduled C-sections (perinatal hAFS), thus offering a more easily accessible alternative when compared to fetal hAFS. Nonetheless, little is known about the paracrine profile of perinatal hAFS. Here we provide a detailed characterization of the hAFS total secretome (i.e., the entirety of soluble paracrine factors released by cells in the conditioned medium, hAFS-CM) and the extracellular vesicles (hAFS-EVs) within it, from II trimester fetal- versus III trimester perinatal cells. Fetal- and perinatal hAFS were characterized and subject to hypoxic preconditioning to enhance their paracrine potential. hAFS-CM and hAFS-EV formulations were analyzed for protein and chemokine/cytokine content, and the EV cargo was further investigated by RNA sequencing. The phenotype of fetal- and perinatal hAFS, along with their corresponding secretome formulations, overlapped; yet, fetal hAFS showed immature oxidative phosphorylation activity when compared to perinatal ones. The profiling of their paracrine cargo revealed some differences according to gestational stage and hypoxic preconditioning. Both cell sources provided formulations enriched with neurotrophic, immunomodulatory, anti-fibrotic and endothelial stimulating factors, and the immature fetal hAFS secretome was defined by a more pronounced pro-vasculogenic, regenerative, pro-resolving and anti-aging profile. Small RNA profiling showed microRNA enrichment in both fetal- and perinatal hAFS-EV cargo, with a stably- expressed pro-resolving core as a reference molecular signature. Here we confirm that hAFS represents an appealing source of regenerative paracrine factors; the selection of either fetal or perinatal hAFS secretome formulations for future paracrine therapy should be evaluated considering the specific clinical scenario.

Dissecting the effects of preconditioning with inflammatory cytokines and hypoxia on the angiogenic potential of mesenchymal stromal cell (MSC)-derived soluble proteins and extracellular vesicles (EVs)

Mesenchymal stromal cells (MSCs) are characterized by a regulatory phenotype and respond promptly to the environmental signals modulating their secretory activity. An appropriate preconditioning may induce MSCs to release secretomes with an enhanced regenerative potential. However, it fails to take into account that secretomes are composed by both soluble factors and extracellular vesicles (EVs), whose functions could be altered differently by the preconditioning approach. Here we demonstrate that the MSC secretome is strongly modulated by the simultaneous stimulation with hypoxia and pro-inflammatory cytokines, used to mimic the harsh environment present at the site of injury. We observed that the environmental variations strongly influenced the angiogenic potential of the different secretome fractions. Upon inflammation, the pro-angiogenic capacity of the soluble component of the MSC secretome was strongly inhibited, regardless of the oxygen level, while the EV-encapsulated component was not significantly affected by the inflammatory stimuli. These effects were accompanied by the modulation of the secreted proteins. On one hand, inflammation-activated MSCs release proteins mainly involved in the interaction with innate immune cells and in tissue remodeling/repair; on the other hand, when MSCs are not exposed to an inflamed environment, they respond to the different oxygen levels modulating the expression of proteins involved in the angiogenic process. The cargo content (in terms of miRNAs) of the corresponding EV fractions was less sensitive to the influence of the external stimuli. Our findings suggest that the therapeutic efficacy of MSC-based therapies could be enhanced by selecting the appropriate preconditioning approach and carefully discriminating its effects on the different secretome components.

Sox2-dependent maintenance of mouse oligodendroglioma involves the Sox2-mediated downregulation of Cdkn2b, Ebf1, Zfp423, and Hey2

Cancer stem cells (CSC) are essential for tumorigenesis. The transcription factor Sox2 is overexpressed in brain gliomas, and is essential to maintain CSC. In mouse high-grade glioma pHGG cells in culture, Sox2 deletion causes cell proliferation arrest and inability to reform tumors after transplantation in vivo; in Sox2-deleted cells, 134 genes are derepressed. To identify genes mediating Sox2 deletion effects, we overexpressed into pHGG cells nine among the most derepressed genes, and identified four genes, Ebf1, Hey2, Zfp423, and Cdkn2b, that strongly reduced cell proliferation in vitro and brain tumorigenesis in vivo. CRISPR/Cas9 mutagenesis of each gene, individually or in combination (Ebf1 + Cdkn2b), significantly antagonized the proliferation arrest caused by Sox2 deletion. The same genes also repressed clonogenicity in primary human glioblastoma-derived CSC-like lines. These experiments identify a network of critical tumor suppressive Sox2-targets whose inhibition by Sox2 is involved in glioma CSC maintenance, defining new potential therapeutic targets.

Glioblastoma models driven by different mutations converge to the proneural subtype

The need of reliable syngeneic animal models for gliomas has been addressed in the last decades by reproducing genetic alterations typical of human glioblastoma in the mouse. Since different alterations underlie different molecular glioblastoma subtypes it is commonly expected that tumors induced by specific alterations represent models of the corresponding subtypes. We tested this assumption by a multilevel analysis ranging from a detailed histopathological analysis to a genome-wide expression profiling by microarray and RNA-seq on gliomas induced by two distinct molecular alterations: the overstimulation of the PDGF- and the EGF- pathways. These alterations are landmarks of proneural and classical glioblastoma subtypes respectively. However, our results consistently showed a strong similarity between the two glioma models. The expression profiles of both models converged toward a signature typical of oligodendrocyte progenitor cells, regardless the wide differentiative potential of the cell of origin. A classification based on similarity with human gliomas profiles revealed that both models belong to the proneural subtype. Our results highlight that reproducing a molecular alteration specific of a glioblastoma subtype not necessarily generates a tumor model recapitulating such subtype.

TRIM8-driven transcriptomic profile of neural stem cells identified glioma-related nodal genes and pathways

BACKGROUND

We recently reported TRIM8, encoding an E3 ubiquitin ligase, as a gene aberrantly expressed in glioblastoma whose expression suppresses cell growth and induces a significant reduction of clonogenic potential in glioblastoma cell lines.

METHODS

we provided novel insights on TRIM8 functions by profiling the transcriptome of TRIM8-expressing primary mouse embryonal neural stem cells by RNA-sequencing and bioinformatic analysis. Functional analysis including luciferase assay, western blot, PCR arrays, Real time quantitative PCR were performed to validate the transcriptomic data.

RESULTS

Our study identified enriched pathways related to the neurotransmission and to the central nervous system (CNS) functions, including axonal guidance, GABA receptor, Ephrin B, synaptic long-term potentiation/depression, and glutamate receptor signalling pathways. Finally, we provided additional evidence about the existence of a functional interactive crosstalk between TRIM8 and STAT3.

CONCLUSIONS

Our results substantiate the role of TRIM8 in the brain functions through the dysregulation of genes involved in different CNS-related pathways, including JAK-STAT.

GENERAL SIGNIFICANCE

This study provides novel insights on the physiological TRIM8 function by profiling for the first time the primary Neural Stem Cell over-expressing TRIM8 by using RNA-Sequencing methodology.

HSV as A Platform for the Generation of Retargeted, Armed, and Reporter-Expressing Oncolytic Viruses

Previously, we engineered oncolytic herpes simplex viruses (o-HSVs) retargeted to the HER2 (epidermal growth factor receptor 2) tumor cell specific receptor by the insertion of a single chain antibody (scFv) to HER2 in gD, gH, or gB. Here, the insertion of scFvs to three additional cancer targets—EGFR (epidermal growth factor receptor), EGFRvIII, and PSMA (prostate specific membrane antigen)—in gD Δ6–38 enabled the generation of specifically retargeted o-HSVs. Viable recombinants resulted from the insertion of an scFv in place of aa 6–38, but not in place of aa 61–218. Hence, only the gD N-terminus accepted all tested scFv inserts. Additionally, the insertion of mIL12 in the US1-US2 intergenic region of the HER2- or EGFRvIII-retargeted o-HSVs, and the further insertion of Gaussia Luciferase, gave rise to viable recombinants capable of secreting the cytokine and the reporter. Lastly, we engineered two known mutations in gB; they increased the ability of an HER2-retargeted recombinant to spread among murine cells. Altogether, current data show that the o-HSV carrying the aa 6–38 deletion in gD serves as a platform for the specific retargeting of o-HSV tropism to a number of human cancer targets, and the retargeted o-HSVs serve as simultaneous vectors for two molecules.

Platelet derived growth factor B gene expression in the Xenopus laevis developing central nervous system

Platelet-derived growth factor B (PDGF-B) belongs to the mitogen and growth factor family and like the other members it has many roles in cell differentiation, proliferation and migration during development, adult life and in pathological conditions. Among them it has been observed that aberrant PDGF signalling is frequently linked to glioma development and progression, and Pdgf-b over-expression in mouse neural progenitors leads to the formation of gliomas. Despite this evidence, the mechanisms underlying PDGF-B driven tumorigenesis and its role during brain development are not fully understood. In order to contribute to clarifying possible new roles of pdgf-b signalling, we present here the embryonic gene expression pattern of pdgf-b, so far unknown in early vertebrate development. By using Xenopus laevis as a model system we performed qRT-PCR and whole mount in situ hybridization. Pdgf-b mRNA is expressed in discrete regions of the developing central nervous system, in the cranial nerve placodes and in the notochord. We also compared the gene expression of pdgf-b with that of its receptor pdgfr-α suggesting so far unsuspected roles for this signalling pathway during the development of specific embryonic structures.

Noninvasive Monitoring of Glioma Growth in the Mouse

Malignant gliomas are the most common and deadly primary malignant brain tumors. In vivo orthotopic models could doubtless represent an appropriate tool to test novel treatment for gliomas. However, methods commonly used to monitor the growth of glioma inside the mouse brain are time consuming and invasive. We tested the reliability of a minimally invasive procedure, based on a secreted luciferase (Gaussia luciferase), to frequently monitor the changes of glioma size.

Gluc activity was evaluated from blood samples collected from the tail tip of mice twice a week, allowing to make a growth curve for the tumors. We validated the correlation between Gluc activity and tumor size by analysing the tumor after brain dissection. We found that this method is reliable for monitoring human glioma transplanted in immunodeficient mice, but it has strong limitation in immunocompetent models, where an immune response against the luciferase is developed during the first weeks after transplant.

Polycomb dysregulation in gliomagenesis targets a Zfp423-dependent differentiation network

Malignant gliomas constitute one of the most significant areas of unmet medical need, owing to the invariable failure of surgical eradication and their marked molecular heterogeneity. Accumulating evidence has revealed a critical contribution by the Polycomb axis of epigenetic repression. However, a coherent understanding of the regulatory networks affected by Polycomb during gliomagenesis is still lacking. Here we integrate transcriptomic and epigenomic analyses to define Polycomb-dependent networks that promote gliomagenesis, validating them both in two independent mouse models and in a large cohort of human samples. We find that Polycomb dysregulation in gliomagenesis affects transcriptional networks associated with invasiveness and de-differentiation. The dissection of these networks uncovers Zfp423 as a critical Polycomb-dependent transcription factor whose silencing negatively impacts survival. The anti-gliomagenic activity of Zfp423 requires interaction with the SMAD proteins within the BMP signalling pathway, pointing to a novel synergic circuit through which Polycomb inhibits BMP signalling.

Sox2 is required to maintain cancer stem cells in a mouse model of high-grade oligodendroglioma

The stem cell-determining transcription factor Sox2 is required for the maintenance of normal neural stem cells. In this study, we investigated the requirement for Sox2 in neural cancer stem-like cells using a conditional genetic deletion mutant in a mouse model of platelet-derived growth factor-induced malignant oligodendroglioma. Transplanting wild-type oligodendroglioma cells into the brain generated lethal tumors, but mice transplanted with Sox2-deleted cells remained free of tumors. Loss of the tumor-initiating ability of Sox2-deleted cells was reversed by lentiviral-mediated expression of Sox2. In cell culture, Sox2-deleted tumor cells were highly sensitive to differentiation stimuli, displaying impaired proliferation, increased cell death, and aberrant differentiation. Gene expression analysis revealed an early transcriptional response to Sox2 loss. The observed requirement of oligodendroglioma stem cells for Sox2 suggested its relevance as a target for therapy. In support of this possibility, an immunotherapeutic approach based on immunization of mice with SOX2 peptides delayed tumor development and prolonged survival. Taken together, our results showed that Sox2 is essential for tumor initiation by mouse oligodendroglioma cells, and they illustrated a Sox2-directed strategy of immunotherapy to eradicate tumor-initiating cells.

Radial glia - from boring cables to stem cell stars

The discovery in the year 2000 that radial glial cells act as neural stem and progenitor cells in development has led to a change in the concept of neural stem cells in the adult brain. Not only are adult stem cells in the neurogenic niches glial in nature, but also glial cells outside these niches display greater potential when reacting to brain injury. Thus, a concept that emerged from developmental studies may hold the clue for neural repair.

Role of Btg2 in the progression of a PDGF-induced oligodendroglioma model

Tumor progression is a key aspect in oncology. Not even the overexpression of a powerful oncogenic stimulus such as platelet derived growth factor-B (PDGF-B) is sufficient per se to confer full malignancy to cells. In previous studies we showed that neural progenitors overexpressing PDGF-B need to undergo progression to acquire the capability to give rise to secondary tumor following transplant. By comparing the expression profile of PDGF-expressing cells before and after progression, we found that progressed tumors consistently downregulate the expression of the antiproliferative gene Btg2. We therefore tested whether the downregulation of Btg2 is sufficient and necessary for glioma progression with loss and gain of function experiments. Our results show that downregulation of Btg2 is not sufficient but is necessary for tumor progression since the re-introduction of Btg2 in fully progressed tumors dramatically impairs their gliomagenic potential. These results suggest an important role of Btg2 in glioma progression. Accordingly with this view, the analysis of public datasets of human gliomas showed that reduced level of Btg2 expression correlates with a significantly worse prognosis.

Sgk1 enhances RANBP1 transcript levels and decreases taxol sensitivity in RKO colon carcinoma cells

The serum- and glucocorticoid-regulated kinase (Sgk1) is essential for hormonal regulation of epithelial sodium channel-mediated sodium transport and is involved in the transduction of growth factor-dependent cell survival and proliferation signals. Growing evidence now points to Sgk1 as a key element in the development and/or progression of human cancer. To gain insight into the mechanisms through which Sgk1 regulates cell proliferation, we adopted a proteomic approach to identify up- or downregulated proteins after Sgk1-specific RNA silencing. Among several proteins, the abundance of which was found to be up- or downregulated upon Sgk1 silencing, we focused our attention of RAN-binding protein 1 (RANBP1), a major effector of the GTPase RAN. We report that Sgk1-dependent regulation of RANBP1 has functional consequences on both mitotic microtubule activity and taxol sensitivity of cancer cells.

A novel collection of snRNA-like promoters with tissue-specific transcription properties

We recently identified a novel dataset of snRNA-like trascriptional units in the human genome. The investigation of a subset of these elements showed that they play relevant roles in physiology and/or pathology. In this work we expand our collection of small RNAs taking advantage of a newly developed algorithm able to identify genome sequence stretches with RNA polymerase (pol) III type 3 promoter features thus constituting putative pol III binding sites. The bioinformatic analysis of a subset of these elements that map in introns of protein-coding genes in antisense configuration suggest their association with alternative splicing, similarly to other recently characterized small RNAs. Interestingly, the analysis of the transcriptional activity of these novel promoters shows that they are active in a cell-type specific manner, in accordance with the emerging body of evidence of a tissue/cell-specific activity of pol III.

Antagonistic modulation of gliomagenesis by Pax6 and Olig2 in PDGF-induced oligodendroglioma

Gliomas are aggressive tumors of the central nervous system originating from proliferating neural cells. Regulators of neural stem or progenitor cells biology may thus influence aspects of brain tumorigenesis, such as the maintenance of tumor-propagating potential. We investigated the role of Pax6, a neurogenic transcription factor already suggested as a positive prognostic marker for human gliomas, in a well-characterized in vivo model of PDGF-B-driven oligodendroglioma. In this system, the expression of Pax6 severely impairs tumor propagation by inducing a reduction of cell proliferation and the acquisition of differentiation traits in tumor-initiating cells. The overexpression of Pax6 correlates with a downregulation of Olig2, a bHLH transcription factor that normally antagonizes Pax6 in adult neurogenic niches and that plays a key role in the maintenance of neural stem and progenitor cells. Furthermore, we found that Olig2 is strictly required to maintain the malignancy of oligodendroglioma cells, since its silencing by interfering RNA abrogates tumor propagation. We finally show evidence that this function depends, at least in part, on the silencing of ID4, a dominant negative bHLH protein, whose upregulation follows Olig2 loss. In our model, the upregulation of ID4 mimics the loss of Olig2 in impairing the tumor-propagating potential of glioma cells. Our data, therefore, establish the relevance of physiological regulators of neural stem cell biology in regulating glial tumor malignancy and provide support for their functional interactions in this context.

Preclinical studies identify novel targeted pharmacological strategies for treatment of human malignant pleural mesothelioma

The incidence of human malignant pleural mesothelioma (hMPM) is still increasing worldwide. hMPM prognosis is poor even if the median survival time has been slightly improved after the introduction of the up-to-date chemotherapy. Nevertheless, large phase II/III trials support the combination of platinum derivatives and pemetrexed or raltitrexed, as preferred first-line schedule. Better understanding of the molecular machinery of hMPM will lead to the design and synthesis of novel compounds targeted against pathways identified as crucial for hMPM cell proliferation and spreading. Among them, several receptors tyrosine kinase show altered activity in subsets of hMPM. This observation suggests that these kinases might represent novel therapeutic targets in this chemotherapy-resistant disease. Over these foundations, several promising studies are ongoing at preclinical level and novel molecules are currently under evaluation as well. Yet, established tumour cell lines, used for decades to investigate the efficacy of anticancer agents, although still the main source of drug efficacy studies, after long-term cultures tend to biologically diverge from the original tumour, limiting the predictive potential of in vivo efficacy. Cancer stem cells (CSCs), a subpopulation of malignant cells capable of self-renewal and multilineage differentiation, are believed to play an essential role in cancer initiation, growth, metastasization and relapse, being responsible of chemo- and radiotherapy refractoriness. According to the current carcinogenesis theory, CSCs represent the tumour-initiating cell (TIC) fraction, the only clonogenic subpopulation able to originate a tumour mass. Consequently, the recently described isolation of TICs from hMPM, the proposed main pharmacological target for novel antitumoural drugs, may contribute to better dissect the biology and multidrug resistance pathways controlling hMPM growth.

PDGF-B-driven gliomagenesis can occur in the absence of the proteoglycan NG2

BACKGROUND

In the last years, the transmembrane proteoglycan NG2 has gained interest as a therapeutic target for the treatment of diverse tumor types, including gliomas, because increases of its expression correlate with dismal prognosis. NG2 has been shown to function as a co-receptor for PDGF ligands whose aberrant expression is common in gliomas. We have recently generated a glioma model based on the overexpression of PDGF-B in neural progenitors and here we investigated the possible relevance of NG2 during PDGF-driven gliomagenesis.

METHODS

The survival curves of NG2-KO mice overexpressing PDGF-B were compared to controls by using a Log-rank test. The characteristics of tumors induced in NG2-KO were compared to those of tumors induced in wild type mice by immunostaining for different cell lineage markers and by transplantation assays in adult mice.

RESULTS

We showed that the lack of NG2 does not appreciably affect any of the characterized steps of PDGF-driven brain tumorigenesis, such as oligodendrocyte progenitor cells (OPC) induction, the recruitment of bystander OPCs and the progression to full malignancy, which take place as in wild type animals.

CONCLUSIONS

Our analysis, using both NG2-KO mice and a miRNA based silencing approach, clearly demonstrates that NG2 is not required for PDGF-B to efficiently induce and maintain gliomas from neural progenitors. On the basis of the data obtained, we therefore suggest that the role of NG2 as a target molecule for glioma treatment should be carefully reconsidered.

Recent insights into PDGF-induced gliomagenesis

Gliomas are aggressive and almost incurable glial brain tumors which frequently display abnormal platelet-derived growth factor (PDGF) signaling. Evidence gained from studies on several in vivo animal models has firmly established a causal connection between aberrant PDGF signaling and the formation of some gliomas. However, only recently has significant knowledge been gained regarding crucial issues such as the glioma cell of origin and the relationship between the transforming stimulus and the cellular characteristics of the resulting tumor. Based on recent evidence, we propose that PDGF can bias cell-fate decisions, driving the acquisition of cell type-specific features by the progeny of multipotent neural progenitors, thus determining the shape and direction of the transformation path. Furthermore, recent data about the cellular mechanisms of PDGF-driven glioma progression and maintenance indicate that PDGF may be required, unexpectedly, to override cell contact inhibition and promote glioma cell infiltration rather than to stimulate cell proliferation.

SOX2 silencing in glioblastoma tumor-initiating cells causes stop of proliferation and loss of tumorigenicity

Glioblastoma, the most aggressive cerebral tumor, is invariably lethal. Glioblastoma cells express several genes typical of normal neural stem cells. One of them, SOX2, is a master gene involved in sustaining self-renewal of several stem cells, in particular neural stem cells. To investigate its role in the aberrant growth of glioblastoma, we silenced SOX2 in freshly derived glioblastoma tumor-initiating cells (TICs). Our results indicate that SOX2 silenced glioblastoma TICs, despite the many mutations they have accumulated, stop proliferating and lose tumorigenicity in immunodeficient mice. SOX2 is then also fundamental for maintenance of the self-renewal capacity of neural stem cells when they have acquired cancer properties. SOX2, or its immediate downstream effectors, would then be an ideal target for glioblastoma therapy.

PDGF-B induces a homogeneous class of oligodendrogliomas from embryonic neural progenitors

We describe the generation of mouse gliomas following the overexpression of PDGF-B in embryonic neural progenitors. Our histopathological, immunohistochemical and genome-wide expression analyses revealed a surprising uniformity among PDGF-B induced tumors, despite they were generated by transducing a highly heterogeneous population of progenitor cells known for their ability to produce all the cell types of the central nervous system. Comparison of our microarray data with published gene expression data sets for many different murine neural cell types revealed a closest correlation between our tumor cells and oligodendrocyte progenitor cells, confirming definitively that PDGF-B-induced gliomas are pure oligodendrogliomas. Importantly, we show that this uniformity is likely due to the ability of PDGF-B overexpression to respecify competent embryonic neural precursors toward the oligodendroglial lineage, providing evidence that the transforming activity of PDGF-B is influenced by the developmental potential of the targeted cells. Interestingly, we found that PDGF-B-induced tumors harbor different proliferating cell populations. However only PDGF-B-overexpressing cells are tumorigenic, indicating that paracrine signaling from the tumor is unable to transform bystander cells.

Six3 controls the neural progenitor status in the murine CNS

Six3, a homeodomain-containing transcriptional regulator belonging to the Six/so family, shows a defined spatiotemporal expression pattern in the developing murine telencephalon, suggesting that it may control the development of specific subsets of neural progenitors. We find that retrovirus-mediated misexpression of Six3 causes clonal expansion of isolated cortical progenitor cells by shortening their cell cycle and by prolonging their amplification period, while maintaining them in an immature precursor state. Our results show that the observed effects exerted by Six3 overexpression in mammalian brain depend strictly on the integrity of its DNA-binding domain, suggesting that Six3 action likely relies exclusively on its transcriptional activity. In vivo upregulation of Six3 expression in single progenitor cells of the embryonic telencephalon keeps them in an undifferentiated state. Our observations point to a role of Six3 in the control of the subtle equilibrium between proliferation and differentiation of defined precursor populations during mammalian neurogenesis.

Prospective isolation of functionally distinct radial glial subtypes--lineage and transcriptome analysis

Since the discovery of radial glia as the source of neurons, their heterogeneity in regard to neurogenesis has been described by clonal and time-lapse analysis in vitro. However, the molecular determinants specifying neurogenic radial glia differently from radial glia that mostly self-renew remain ill-defined. Here, we isolated two radial glial subsets that co-exist at mid-neurogenesis in the developing cerebral cortex and their immediate progeny. While one subset generates neurons directly, the other is largely non-neurogenic but also gives rise to Tbr2-positive basal precursors, thereby contributing indirectly to neurogenesis. Isolation of these distinct radial glia subtypes allowed determining interesting differences in their transcriptome. These transcriptomes were also strikingly different from the transcriptome of radial glia isolated at the end of neurogenesis. This analysis therefore identifies, for the first time, the lineage origin of basal progenitors and the molecular differences of this lineage in comparison to directly neurogenic and gliogenic radial glia.

Radial glia and neural stem cells

During the last decade, the role of radial glia has been radically revisited. Rather than being considered a mere structural component serving to guide newborn neurons towards their final destinations, radial glia is now known to be the main source of neurons in several regions of the central nervous system, notably in the cerebral cortex. Radial glial cells differentiate from neuroepithelial progenitors at the beginning of neurogenesis and share with their ancestors the bipolar shape and the expression of some molecular markers. Radial glia, however, can be distinguished from neuroepithelial progenitors by the expression of astroglial markers. Clonal analyses showed that radial glia is a heterogeneous population, comprising both pluripotent and different lineage-restricted neural progenitors. At late-embryonic and postnatal stages, radial glial cells give rise to the neural stem cells responsible for adult neurogenesis. Embryonic pluripotent radial glia and adult neural stem cells may be clonally linked, thus representing a lineage displaying stem cell features in both the developing and mature central nervous system.

Functional analysis of R75Q mutation in the gene coding for Connexin 26 identified in a family with nonsyndromic hearing loss

Mutations in the gene (GJB2) coding for Connexin 26 (Cx26) are responsible for genetic forms of sensorineural hearing loss. This article describes a family characterized by congenital profound hearing loss, inherited in an autosomal dominant fashion and associated to a R75Q substitution in Cx26. Cell transfection and fluorescence imaging, dye transfer experiments and dual patch clamp recording showed that the mutant completely prevents the formation of functional channels despite assembling into junctional plaques, in communication incompetent HeLa cells. The disease is not associated with palmar and plantar keratosis in any of the family members, suggesting that R75Q substitution is not sufficient for the development of the complete syndromic phenotype. The association of palmar and plantar keratosis with profound hearing loss may be dependent on genetic background, requiring a functional interaction between the mutated Cx26 and other epidermally expressed connexins.

Neurogenic potential of human mesenchymal stem cells revisited: analysis by immunostaining, time-lapse video and microarray

The possibility of generating neural cells from human bone-marrow-derived mesenchymal stem cells (hMSCs) by simple in vitro treatments is appealing both conceptually and practically. However, whether phenotypic modulations observed after chemical manipulation of such stem cells truly represent a genuine trans-lineage differentiation remains to be established. We have re-evaluated the effects of a frequently reported biochemical approach, based on treatment with butylated hydroxyanisole and dimethylsulphoxide, to bring about such phenotypic conversion by monitoring the morphological changes induced by the treatment in real time, by analysing the expression of phenotype-specific protein markers and by assessing the modulation of transcriptome. Video time-lapse microscopy showed that conversion of mesenchymal stem cells to a neuron-like morphology could be reproduced in normal primary fibroblasts as well as mimicked by addition of drugs eliciting cytoskeletal collapse and disruption of focal adhesion contacts. Analysis of markers revealed that mesenchymal stem cells constitutively expressed multi-lineage traits, including several pertaining to the neural one. However, the applied ;neural induction' protocol neither significantly modulated the expression of such markers, nor induced de novo translation of other neural-specific proteins. Similarly, global expression profiling of over 21,000 genes demonstrated that gene transcription was poorly affected. Most strikingly, we found that the set of genes whose expression was altered by the inductive treatment did not match those sets of genes differentially expressed when comparing untreated mesenchymal stem cells and immature neural tissues. Conversely, by comparing these gene expression profiles with that obtained from comparisons between the same cells and an unrelated non-neural organ, such as liver, we found that the adopted neural induction protocol was no more effective in redirecting human mesenchymal stem cells toward a neural phenotype than toward an endodermal hepatic pathway.

Neuronal or glial progeny: regional differences in radial glia fate

The precursor function of the ubiquitous glial cell type in the developing central nervous system (CNS), the radial glia, is largely unknown. Using Cre/loxP in vivo fate mapping studies, we found that radial glia generate virtually all cortical projection neurons but not the interneurons originating in the ventral telencephalon. In contrast to the cerebral cortex, few neurons in the basal ganglia originate from radial glia, and in vitro lineage analysis revealed intrinsic differences in the potential of radial glia from the dorsal and ventral telencephalon. This shows that the progeny of radial glia not only differs profoundly between brain regions but also includes the majority of neurons in some parts of the CNS.

Glial cells generate neurons: the role of the transcription factor Pax6

Radial glial cells, ubiquitous throughout the developing CNS, guide radially migrating neurons and are the precursors of astrocytes. Recent evidence indicates that radial glial cells also generate neurons in the developing cerebral cortex. Here we investigated the role of the transcription factor Pax6 expressed in cortical radial glia. We showed that radial glial cells isolated from the cortex of Pax6 mutant mice have a reduced neurogenic potential, whereas the neurogenic potential of non-radial glial precursors is not affected. Consistent with defects in only one neurogenic lineage, the number of neurons in the Pax6 mutant cortex in vivo is reduced by half. Conversely, retrovirally mediated Pax6 expression instructs neurogenesis even in astrocytes from postnatal cortex in vitro. These results demonstrated an important role of Pax6 as intrinsic fate determinant of the neurogenic potential of glial cells.

Radial glial cells as neuronal precursors: a new perspective on the correlation of morphology and lineage restriction in the developing cerebral cortex of mice

Radial glia is a ubiquitous cell type in the developing central nervous system (CNS) of vertebrates, characterized by radial processes extending through the wall of the neural tube which serve as guiding cables for migrating neurons. Radial glial cells were considered as glial precursor cells due to their astroglial traits and later transformation into astrocytes in the mammalian CNS. Accordingly, a hypothetical morphologically distinct type of precursor was attributed the role of neurogenesis. Recent evidence obtained in vitro and in vivo, however, revealed that a large subset of radial glia generates neurons. We further demonstrate here that the progeny of radial glial cells does not differ from the progeny of precursors labeled from the ventricular surface, implying that there is no obvious relation between precursor morphology and neuron-glia lineage decisions in the developing cerebral cortex of mice. Moreover, we show that many radial glial cells seem to maintain their process during cell division and discuss the implications of this observation for the orientation of cell division. These new data are then related to radial glial cells in other non-mammalian vertebrates persisting into adulthood and suggest that radial glia are not only neurogenic during development, but also in adulthood.

Emx2 promotes symmetric cell divisions and a multipotential fate in precursors from the cerebral cortex

Distinct sets of precursor cells generate the mammalian cerebral cortex. During neurogenesis most precursors are specified to generate a single cell type and only few are multipotent. The cell-intrinsic molecular determinants of these distinct lineages are not known. Here we describe that retroviral transduction of the transcription factor Emx2 in precursors from the cerebral cortex results in a significant increase of large clones that are generated mostly by symmetric cell divisions and contain multiple cell types, comprising neurons and glial cells. Thus, Emx2 is the first cell-intrinsic determinant able to instruct CNS precursors towards a multipotential fate. To evaluate the role of endogenous Emx2 in cortical precursors, we examined cell division in Emx2-/- mice. These analyses further supported the role of endogenous Emx2 in the regulation of symmetric cell divisions in the developing cortex.

In vivo PC3 overexpression by retroviral vector affects cell differentiation of rat cortical precursors

The PC3 gene is a marker of dividing neuroepithelial (NE) cells. We transduced single cortical precursors of the ventricular zone (VZ) with a PC3-carrying retroviral vector at E16 stage, and analysed the effects of transgene expression on their progeny in 3-week-old animals. Unlike control-transduced cells, all viable PC3-transduced cells remained close to the ventricle and displayed a round-shaped, undifferentiated morphology.

Prevention of pericardial adhesions with N-O carboxymethylchitosan in the rabbit model

The presence of mediastinal adhesions significantly increases the morbidity and mortality of reoperative cardiac surgical procedures. Previous investigations have reported on the therapeutic utility of topical hydrogels in reducing the formation of postsurgical adhesions. The goal of the present study is to evaluate the ability of N-O carboxymethylchitosan (a glycosaminoglycan hydrogel derivative) to reduce the formation ofpostsurgical pericardial adhesions in a large-animal model. Sixteen adult New Zealand white rabbits were randomly assigned to one of two treatment groups. Group 1 subjects (n = 8) had N-O carboxymethylchitosan directly applied to the heart and retrosternal surfaces after sternotomy was performed, while subjects in group 2 (n = 8) had saline applied to these areas. After a period of 14 days the animals were sacrificed under anesthesia, and independent observers, blinded to treatment, graded the formation of pericardial adhesions. The severity of adhesion formation was significantly less in the group treated with N-O carboxymethylchitosan (p < .01). This study demonstrates that N-O carboxymethylchitosan markedly decreases the formation of poststernotomy adhesions in a large-animal model without untoward cardiac side effects. This hydrogel derivative may prove to be of great therapeutic value when used prophylactically in the setting of cardiac surgery.

Isolation of radial glial cells by fluorescent-activated cell sorting reveals a neuronal lineage

The developing central nervous system of vertebrates contains an abundant cell type designated radial glial cells. These cells are known as guiding cables for migrating neurons, while their role as precursor cells is less clear. Since radial glial cells express a variety of astroglial characteristics and differentiate as astrocytes after completing their guidance function, they have been considered as part of the glial lineage. Using fluorescence-activated cell sorting, we show here that radial glial cells also are neuronal precursors and only later, after neurogenesis, do they shift towards an exclusive generation of astrocytes. These results thus demonstrate a novel function for radial glial cells, namely their ability to generate two major cell types found in the nervous system, neurons and astrocytes.

PC3 overexpression affects the pattern of cell division of rat cortical precursors

The PC3 gene is transiently expressed during neurogenesis in precursor cells of the telencephalic ventricular/subventricular zone, and is rapidly downregulated before cell migration and differentiation. It is thought to have a role in controlling cell proliferation, but its precise function is not known. Here we present evidence that PC3, when overexpressed in vitro by retroviral-mediated gene transfer, acts by interfering with the normal pattern of cell division. Firstly, we report evidence that PC3 overexpression reduces the rate of cell proliferation in both NIH 3T3 cells and embryonic precursor cells from the rat cerebral cortex. Secondly, when studying the pattern of BrdU dilution in clones of cortical precursors, we observe that clones transduced with PC3 show an asymmetric pattern of BrdU dilution more frequently than clones transduced with a control vector. We discuss the hypothesis that the higher number of PC3 transduced clones showing an asymmetric pattern of BrdU dilution may be due to an increase in asymmetric cell divisions.

Characterization of a cloned xenopus laevis serotonin 5-HT1A receptor expressed in the NIH-3T3 cell line

In a previous work we isolated a Xenopus 5-HT1A receptor gene and now report the characterization of this receptor. The HindIII-XbaI fragment of this gene was cloned into the pcDNA I NEO vector and stably transfected into eukaryotic cells (NIH-3T3). To determine the specific 5-HT1A receptor binding, [3H]8-OH-DPAT was used as radioligand. The selective 5-HT1A receptor agonist bound only a single class of saturable high-affinity binding sites with pharmacological characteristics similar to those of the mammalian 5-HT1A receptor. The effects of X5-HT1A receptor activation on cell growth were also investigated in stably transfected NIH-3T3 cells. The 5-HT1A agonist 8-OH-DPAT was found to increase DNA synthesis and accelerated cell growth.

Deletion polymorphism of angiotensin-converting enzyme gene and left ventricular hypertrophy in southern Italian patients

OBJECTIVES

This study sought to evaluate the possible association of polymorphism of the angiotensin-converting enzyme (ACE) gene with blood pressure and left ventricular mass index (LVMI).

BACKGROUND

The renin-angiotensin system seems to be involved in the pathogenesis of essential hypertension. Moreover, recent epidemiologic observations demonstrate that many subjects with left ventricular hypertrophy have normal blood pressure levels, suggesting that factors other than hemodynamic overload may contribute to the hypertrophy.

METHODS

The study included 140 untreated hypertensive outpatients who underwent ambulatory blood pressure monitoring, echocardiographic evaluation and analysis for insertion (I)/ deletion (D) polymorphism in intron 16 of the ACE gene by polymerase chain reaction. Blood pressure was measured at 24 h, and LVMI was calculated by the Devereux formula, in each patient.

RESULTS

Left ventricular mass index values (mean +/- SD) were 137 +/- 28 g/m2 in patients with the DD genotype, 125 +/- 27 g/m2 in those with the ID genotype and 115 +/- 27 g/m2 in those with II genotype. The frequencies of the DD, ID and II genotypes were 45.71% (n = 64), 46.42% (n = 65) and 7.85% (n = 11), respectively, and were in Hardy-Weinberg equilibrium. The strongest association between left ventricular mass and DD genotype in our cohort appeared to be an independent cardiovascular risk factor (DD vs. ID: odds ratio [OR] 2.497, 95% confidence interval [CI] interval 1.158 to 5.412, p < 0.05; DD vs. II: OR 6.577, 95% CI 1.169 to 28.580, p < 0.02).

CONCLUSIONS

Our data show that the LVMI was significantly enhanced in patients with the DD genotype.

The effects of hemodilution with polyethylene glycol bovine hemoglobin (PEG-Hb) in a conscious porcine model

BACKGROUND

Severe hemodilution in large mammals has been used rigorously for the safety and efficacy testing of hemoglobin-based red blood cell substitutes. The effects of hemodilution with polyethylene glycol-modified bovine hemoglobin (PEG-Hb) were investigated in an unanesthetized porcine model.

METHODS

Immature Yorkshire cross barrow pigs were subjected to exchange transfusion with PEG-Hb (n = 6) or dextran 70 (n = 4) until an 80% reduction in hematocrit was achieved.

RESULTS

All six (100%) PEG-Hb-infused pigs and only one (25%) dextran 70 control pig survived the resultant reduction in erythrocytes. Heart rates and mean arterial pressure were not significantly affected by PEG-Hb infusion. Pigs infused with PEG-Hb maintained normal levels of blood pH, PO2, and PCO2 while dextran 70 controls showed low PvO2, PaCO2, and the development of acidosis. Histological evaluation revealed that the surviving dextran 70 control animal exhibited possible anoxia-induced hepatic centrilobular necrosis. PEG-Hb-treated pigs demonstrated the presence of renal tubular cell cytoplasmic vacuoles and vacuolated macrophages in spleens.

CONCLUSIONS

The results indicate that PEG-Hb effectively supports life close to lethal levels of anemia.

[Effort hernia of the diaphragm: apropos of a case]

The so-called stress diaphragmatic hernias are very unusual in the group of post-traumatic hernias. The Authors report a case and consider clinical, anatomical as well as pathophysiological aspects of the disease. Diagnostic procedures and therapeutic approach are also stressed.