Loss of neurogenesis in Hydra leads to compensatory regulation of neurogenic and neurotransmission genes in epithelial cells.

Hydra continuously differentiates a sophisticated nervous system made of mechanosensory cells (nematocytes) and sensory-motor and ganglionic neurons from interstitial stem cells. However, this dynamic adult neurogenesis is dispensable for morphogenesis. Indeed animals depleted of their interstitial stem cells and interstitial progenitors lose their active behaviours but maintain their developmental fitness, and regenerate and bud when force-fed. To characterize the impact of the loss of neurogenesis in Hydra, we first performed transcriptomic profiling at five positions along the body axis. We found neurogenic genes predominantly expressed along the central body column, which contains stem cells and progenitors, and neurotransmission genes predominantly expressed at the extremities, where the nervous system is dense. Next, we performed transcriptomics on animals depleted of their interstitial cells by hydroxyurea, colchicine or heat-shock treatment. By crossing these results with cell-type-specific transcriptomics, we identified epithelial genes up-regulated upon loss of neurogenesis: transcription factors (Dlx, Dlx1, DMBX1/Manacle, Ets1, Gli3, KLF11, LMX1A, ZNF436, Shox1), epitheliopeptides (Arminins, PW peptide), neurosignalling components (CAMK1D, DDCl2, Inx1), ligand-ion channel receptors (CHRNA1, NaC7), G-Protein Coupled Receptors and FMRFRL. Hence epitheliomuscular cells seemingly enhance their sensing ability when neurogenesis is compromised. This unsuspected plasticity might reflect the extended multifunctionality of epithelial-like cells in early eumetazoan evolution.

Multi-functionality and plasticity characterize epithelial cells in Hydra.

Epithelial sheets, a synapomorphy of all metazoans but porifers, are present as 2 layers in cnidarians, ectoderm and endoderm, joined at their basal side by an extra-cellular matrix named mesoglea. In the Hydra polyp, epithelial cells of the body column are unipotent stem cells that continuously self-renew and concomitantly express their epitheliomuscular features. These multifunctional contractile cells maintain homeostasis by providing a protective physical barrier, by digesting nutrients, by selecting a stable microbiota, and by rapidly closing wounds. In addition, epithelial cells are highly plastic, supporting the adaptation of Hydra to physiological and environmental changes, such as long starvation periods where survival relies on a highly dynamic autophagy flux. Epithelial cells also play key roles in developmental processes as evidenced by the organizer activity they develop to promote budding and regeneration. We propose here an integrative view of the homeostatic and developmental aspects of epithelial plasticity in Hydra.

Isolation and partial characterization of a new human glioblastoma cell line.

Although significant progresses were made in the field of molecular biology of malignant cerebral gliomas, the prognostic of these tumors continues to be reserved. One of the therapeutic failure reasons is the incomplete knowledge regarding the origin of these tumors and cells features, which in fact represent an obstacle in developing a cell and molecular therapy guided against malignant cells responsible for the tumor development and for the therapeutic resistance. Initiation and characterization of glioblastoma cell lines represents an essential step in order to obtain a better in vitro and in vivo experimental model for glioblastoma. We describe here a new glioblastoma line, named T11, which was successfully isolated in our laboratories starting with a tumor sample obtained intraoperative from a 58 years-old female patient. The histopathological evaluation showed a grad IV WHO glioma (glioblastoma). The sample was prepared by manual fragmentation, followed by enzymatic digestions using different concentration of trypsin. The cell line has been cultivated for more than 150 passages. The characterization of the glioblastoma line consisted in the evaluation of cells proliferation capacity (growth curve), morphological features, karyotyping and identification of specific markers. We found that T11 expressed specific markers for glial progenitors and astrocytes (glial fibrillary acidic protein-GFAP); oligodendrocites (A2B5; O4), and microglia (CD45, CD 11b). Cells were negative for neuronal lineage markers like beta3-tubulin and NCAM. In order to evaluate the differentiation grade of T11 cell line, the presence of stem cell markers (nestin, CD133) was explored. T11l cells expressed higher level of nestin and lower level of CD133 comparing with standard glioblastoma cell line U87. T11 cell line expressed VEGF and Bcl-2, but not EGFR and Mdrl and Bax. This new line has distinct and unique characteristics when compared with standard glioblastoma cell line (e.g., U87) and may become a new and useful in vitro model for glioblastoma.

Alterations induced by lithium in gfap expression and in the proteinic composition of glial cells in vitro.

In the adult brain, astrocytes account for about 40% of the cell population in the central nervous system. Normal, reactive and neoplastic astrocytes can be identified in immunohistochemical preparations by means of glial fibrillary acid proteins (GFAP) expression. This protein is considered to be a sensitive indicator of xenobiotics toxicity. Previous studies have demonstrated that 2 mM LiCl induce alterations of astrocyte morphology after 18-20 days of treatment in vitro. We have decided to study GFAP expression under such conditions. Immunodetection and Western blotting assays have shown 2 mM of LiCl to induce alterations of GFAP expression both after 12 days of treatment and after 18-20 days. Moreover, 2 mM of LiCl induce an alteration of the proteinic composition of cells.

Lithium action upon Hep2 tumoral cells in vitro.

Previously performed light microscopy studies have demonstrated Hep2 tumoral cells to be sensitive to concentrations of LiCl 1 mM and 2 mM. At those concentrations, LiCl induces morphological alterations consisting in cell hypertrophy, formations of cells with several nuclei similar to syncytium, cytoplasmic projections. This study focuses on the action of LiCl on growth kinetics, cloning capacity and protein composition of Hep2 tumoral cells. We have found LiCl (1 mM and 2 mM) to influence all those parameters.