Olivier Preynat-Seauve

A key role for NOX4 in epithelial cell death during development of lung fibrosis.

UNLABELLED The pathogenesis of pulmonary fibrosis is linked to oxidative stress, possibly generated by the reactive oxygen species (ROS) generating NADPH oxidase NOX4. Epithelial cell death is a crucial early step in the development of the disease, followed only later by the fibrotic stage. We demonstrate that in lungs of patients with idiopathic lung fibrosis, there is strong expression of NOX4 in hyperplastic alveolar type II cells. AIM To study a possible causative role of NOX4 in the death of alveolar cells, we have generated NOX4-deficient mice. RESULTS Three weeks after administration of bleomycin, wild-type (WT) mice developed massive fibrosis, whereas NOX4-deficient mice displayed almost normal lung histology, and only little Smad2 phosphorylation and accumulation of myofibroblasts. However, the protective effects of NOX4 deficiency preceded the fibrotic stage. Indeed, at day 7 after bleomycin, lungs of WT mice showed massive increase in epithelial cell apoptosis and inflammation. In NOX4-deficient mice, no increase in apoptosis was observed, whereas inflammation was comparable to WT. In vitro, NOX4-deficient primary alveolar epithelial cells exposed to transforming growth factor-β(1) did not generate ROS and were protected from apoptosis. Acute treatment with the NOX inhibitors also blunted transforming growth factor-β(1)-induced apoptosis. CONCLUSION ROS generation by NOX4 is a key player in epithelial cell death leading to pulmonary fibrosis.

The miR 302-367 cluster drastically affects self-renewal and infiltration properties of glioma-initiating cells through CXCR4 repression and consequent disruption of the SHH-GLI-NANOG network

Glioblastoma multiforme (GBM) is the most common form of primary brain tumor in adults, often characterized by poor survival. Glioma-initiating cells (GiCs) are defined by their extensive self-renewal, differentiation, and tumor initiation properties. GiCs are known to be involved in tumor growth and recurrence, and in resistance to conventional treatments. One strategy to efficiently target GiCs in GBM consists in suppressing their stemness and consequently their tumorigenic properties. In this study, we show that the miR-302-367 cluster is strongly induced during serum-mediated stemness suppression. Stable miR-302-367 cluster expression is sufficient to suppress the stemness signature, self-renewal, and cell infiltration within a host brain tissue, through inhibition of the CXCR4 pathway. Furthermore, inhibition of CXCR4 leads to the disruption of the sonic hedgehog (SHH)-GLI-NANOG network, which is involved in self-renewal and expression of the embryonic stem cell-like signature. In conclusion, we demonstrated that the miR-302-367 cluster is able to efficiently trigger a cascade of inhibitory events leading to the disruption of GiCs stem-like and tumorigenic properties.

Tumor-Infiltrating Dendritic Cells Are Potent Antigen-Presenting Cells Able to Activate T Cells and Mediate Tumor Rejection

Dendritic cells (DC) are potent inducers of immune responses. DC have been shown to infiltrate tumors, but very little is known about the functional status of these naturally occurring tumor-infiltrating DC (TIDC). In this study, the status and function of TIDC from several types of mouse melanoma were investigated in detail. CD11c+/MHC II+ cells, consistent with a DC phenotype, were found in all of transplantable or spontaneous melanomas studied. These TIDC were predominantly myeloid (CD11c+/CD8α−/B220−) in nature with small numbers of plasmacytoid (CD11c+/B220+). TIDC had an intermediate maturation phenotype with some expression of costimulatory molecules and the capacity to take up particles. Upon culture overnight ex vivo, the TIDC markedly up-regulated the expression of costimulatory molecules and also increased IL-12 production. Importantly, such ex vivo-matured TIDC pulsed with OVA were able to migrate to lymph nodes, to activate naive OVA-specific CD4+ and CD8+ T cells, and to confer protection against a challenge with OVA-expressing tumor cells. In conclusion, melanomas are infiltrated by functional DC that can act as fully competent APC. These APC have the potential to be manipulated and may therefore represent a promising target for cancer immunotherapy.

Neural progenitors derived from human embryonic stem cells are targeted by allogeneic T and natural killer cells.

Neural progenitor cells (NPC) of foetal origin or derived from human embryonic stem cells (HESC) have the potential to differentiate into mature neurons after transplantation into the central nervous system, opening the possibility of cell therapy for neurodegenerative disorders. In most cases, the transplanted NPC are genetically unrelated to the recipient, leading to potential rejection of the transplanted cells. Very few data provide reliable information as to the potential immune response of allogeneic neural progenitors derived from HESC. In this study, we analyzed in vitro the allogeneic immune response of T lymphocytes and natural killer (NK) cells to NPC derived from HESC or of foetal origin. We demonstrate that NPC induce T‐cell stimulation and a strong NK cytotoxic response. NK‐cell activity is unrelated to MHC‐I expression but driven by the activating NKG2D receptor. Cyclosporine and dexamethasone previously used in clinical studies with foetal NPC did not only fail to prevent NK alloreactivity but strongly inhibited the terminal maturation from NPC into mature neurons. We conclude that allogenic transplantation of NPC in the central nervous system will most likely require an immunosuppressive regimen targeting allogenic T and NK cells, whereas possible interference with the differentiation of NPC needs to be carefully evaluated.

Development of Human Nervous Tissue upon Differentiation of Embryonic Stem Cells in Three‐Dimensional Culture

Researches on neural differentiation using embryonic stem cells (ESC) require analysis of neurogenesis in conditions mimicking physiological cellular interactions as closely as possible. In this study, we report an air‐liquid interface‐based culture of human ESC. This culture system allows three‐dimensional cell expansion and neural differentiation in the absence of added growth factors. Over a 3‐month period, a macroscopically visible, compact tissue developed. Histological coloration revealed a dense neural‐like neural tissue including immature tubular structures. Electron microscopy, immunochemistry, and electrophysiological recordings demonstrated a dense network of neurons, astrocytes, and oligodendrocytes able to propagate signals. Within this tissue, tubular structures were niches of cells resembling germinal layers of human fetal brain. Indeed, the tissue contained abundant proliferating cells expressing markers of neural progenitors. Finally, the capacity to generate neural tissues on air‐liquid interface differed for different ESC lines, confirming variations of their neurogenic potential. In conclusion, this study demonstrates in vitro engineering of a human neural‐like tissue with an organization that bears resemblance to early developing brain. As opposed to previously described methods, this differentiation (a) allows three‐dimensional organization, (b) yields dense interconnected neural tissue with structurally and functionally distinct areas, and (c) is spontaneously guided by endogenous developmental cues. STEM CELLS 2009;27:509–520

Extralymphatic Tumors Prepare Draining Lymph Nodes to Invasion via a T-Cell Cross-Tolerance Process

Metastases often develop in lymphoid organs. However, the immunologic mechanism allowing such invasion is not known because these organs are considered to be hostile to tumor cells. Here, we analyzed the interactions between tumor cells and CD8(+) T cells in such lymphoid organs. Tumor cells implanted into lymph nodes were able to induce tumor-specific cytotoxic CD8(+) T-cell responses, conducting to tumor rejection, in contrast to primary extralymphatic tumors rapidly anergizing T cells in draining lymph nodes (DLN) via a cross-presentation process. This abortive CD8(+) T-cell response to extralymphatic tumor is independent of the subcellular localization of antigen in tumor cells and is consistent with a lack of CD4(+) T-cell help. Notably, this anergy was potent enough to allow successful DLN implantation of tumor cells. Such distant cross-tolerization of tumor-specific CD8(+) T cells may be a determinant permissive event leading to invasion of DLN. In this situation, metastatic tumor cells do not need to down-regulate their immunogenicity to spread.

Comprehensive Human Virus Screening Using High-Throughput Sequencing with a User-Friendly Representation of Bioinformatics Analysis: a Pilot Study

ABSTRACT High-throughput sequencing (HTS) provides the means to analyze clinical specimens in unprecedented molecular detail. While this technology has been successfully applied to virus discovery and other related areas of research, HTS methodology has yet to be exploited for use in a clinical setting for routine diagnostics. Here, a bioinformatics pipeline (ezVIR) was designed to process HTS data from any of the standard platforms and to evaluate the entire spectrum of known human viruses at once, providing results that are easy to interpret and customizable. The pipeline works by identifying the most likely viruses present in the specimen given the sequencing data. Additionally, ezVIR can generate optional reports for strain typing, can create genome coverage histograms, and can perform cross-contamination analysis for specimens prepared in series. In this pilot study, the pipeline was challenged using HTS data from 20 clinical specimens representative of those most often collected and analyzed in daily practice. The specimens (5 cerebrospinal fluid, 7 bronchoalveolar lavage fluid, 5 plasma, 2 serum, and 1 nasopharyngeal aspirate) were originally found to be positive for a diverse range of DNA or RNA viruses by routine molecular diagnostics. The ezVIR pipeline correctly identified 14 of 14 specimens containing viruses with genomes of <40,000 bp, and 4 of 6 specimens positive for large-genome viruses. Although further validation is needed to evaluate sensitivity and to define detection cutoffs, results obtained in this pilot study indicate that the overall detection success rate, coupled with the ease of interpreting the analysis reports, makes it worth considering using HTS for clinical diagnostics.

Phenazopyridine induces and synchronizes neuronal differentiation of embryonic stem cells.

Embryonic stem (ES) cells are powerful tools to understand mechanisms of neuronal differentiation and to engineer neurons for in vitro studies and cell therapy. We developed a screening approach to identify small organic molecules driving neuronal differentiation of ES cells. For this purpose, we used a lentivector carrying a dual luciferase reporter system to engineer an ES cell line which allowed us to screen for small organic molecules enhancing neuronal differentiation. One of them, phenazopyridine, was further analysed in human ES cells. Phenazopyridine: (i) enhanced neuronal differentiation, (ii) increased cell survival, (iii) decreased the amount of non‐neuronal and undifferentiated cells and (iv) synchronized the cellular differentiation state. Phenazopyridine allowed the development of a differentiation protocol compatible with the generation of clinical grade neural precursors, which were able differentiate into different neuronal subtypes, astrocytes and oligodendrocytes. In summary, we describe a powerful approach to identify small molecules directing stem cell differentiation. This led to the establishment of a new application for an old drug and the development of a novel clinical grade protocol for neuronal differentiation of ES cells.

Comprehensive metagenomic analysis of glioblastoma reveals absence of known virus despite antiviral‐like type I interferon gene response

Glioblastoma is a deadly malignant brain tumor and one of the most incurable forms of cancer in need of new therapeutic targets. As some cancers are known to be caused by a virus, the discovery of viruses could open the possibility to treat, and perhaps prevent, such a disease. Although an association with viruses such as cytomegalovirus or Simian virus 40 has been strongly suggested, involvement of these and other viruses in the initiation and/or propagation of glioblastoma remains vague, controversial and warrants elucidation. To exhaustively address the association of virus and glioblastoma, we developed and validated a robust metagenomic approach to analyze patient biopsies via high‐throughput sequencing, a sensitive tool for virus screening. In addition to traditional clinical diagnostics, glioblastoma biopsies were deep‐sequenced and analyzed with a multistage computational pipeline to identify known or potentially discover unknown viruses. In contrast to the studies reporting the presence of viral signatures in glioblastoma, no common or recurring active viruses were detected, despite finding an antiviral‐like type I interferon response in some specimens. Our findings highlight a discrete and non‐specific viral signature and uncharacterized short RNA sequences in glioblastoma. This study provides new insights into glioblastoma pathogenesis and defines a general methodology that can be used for high‐resolution virus screening and discovery in human cancers.

Stem cell sources for regenerative medicine: the immunological point of view

Stem cell transplantation consists in the introduction of stem cells or derived products in a diseased organism. Because of the differentiation properties of stem cells, the goal is to replace damaged cells or tissues. Numbers of stem cell were identified and isolated from embryos, fetuses, or adult organs, harboring different properties, and thus providing multiple strategies of regenerative medicine for different diseases. More recently, the artificial induction of stemness properties in adult somatic cells has proposed a new way to generate stem cells. One important concern of stem cell therapy is the possible risk that transplanted stem cells could be rejected by the recipients immune system. Depending on their source, stem cell transplantation is associated with diverse immunological situations. If some sources allow autologous transplantation, others cannot bypass an allogeneic context between the donor and the recipient. This review summarizes all of the stem cell sources for regenerative medicine and the immunological questions associated to their use. Regarding the emerging strategies compatible with autologous transplantation, this article points notably the complexity of the choice between the immunological safety and the specific advantages of allogeneic stem cells.