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Developmental Biology

An Enzyme- and Serum-free Neural Stem Cell Culture Model for EMT Investigation Suited for Drug Discovery

Published: August 23rd, 2016

DOI:

10.3791/54018

1Dept. of Biomedicine, Pharmacenter, University of Basel, 2Molecular Signalling and Gene Therapy, Narayana Nethralaya Foundation, Narayana Health City, 3Brain Ischemia and Regeneration, Department of Biomedicine, University Hospital Basel, 4Department of Neurosurgery, Klinikum Idar-Oberstein, 5Department of Neurosurgery and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, 6Department of Neurology, Laboratory of Molecular Neuro Oncology, University Hospital of Zurich
* These authors contributed equally

Epithelial to mesenchymal transition (EMT) allows cancers to become invasive. To investigate EMT, a neural stem cell (NSC)-based in vitro model devoid of serum and enzymes is described. This standardized system allows quantitative and qualitative assessment of cell migration, gene and protein expression. The model is suited for drug discovery.

Epithelial to mesenchymal transition (EMT) describes the process of epithelium transdifferentiating into mesenchyme. EMT is a fundamental process during embryonic development that also commonly occurs in glioblastoma, the most frequent malignant brain tumor. EMT has also been observed in multiple carcinomas outside the brain including breast cancer, lung cancer, colon cancer, gastric cancer. EMT is centrally linked to malignancy by promoting migration, invasion and metastasis formation. The mechanisms of EMT induction are not fully understood. Here we describe an in vitro system for standardized isolation of cortical neural stem cells (NSCs) and subsequent EMT-induction. This system provides the flexibility to use either single cells or explant culture. In this system, rat or mouse embryonic forebrain NSCs are cultured in a defined medium, devoid of serum and enzymes. The NSCs expressed Olig2 and Sox10, two transcription factors observed in oligodendrocyte precursor cells (OPCs). Using this system, interactions between FGF-, BMP- and TGFβ-signaling involving Zeb1, Zeb2, and Twist2 were observed where TGFβ-activation significantly enhanced cell migration, suggesting a synergistic BMP-/TGFβ-interaction. The results point to a network of FGF-, BMP- and TGFβ-signaling to be involved in EMT induction and maintenance. This model system is relevant to investigate EMT in vitro. It is cost-efficient and shows high reproducibility. It also allows for the comparison of different compounds with respect to their migration responses (quantitative distance measurement), and high-throughput screening of compounds to inhibit or enhance EMT (qualitative measurement). The model is therefore well suited to test drug libraries for substances affecting EMT.

During several stages of embryonic development, epithelial cells lose their strong adherence to each other (e.g., tight junctions) and acquire a migratory phenotype in a process called epithelial to mesenchymal transition (EMT)1. EMT is required for the formation of additional cell types, such as the mesenchymal neural crest cells, a population that segregates from the neuroepithelium2. EMT is not only essential during embryonic stages but also required at later stages of adult life to maintain physiological processes in the adult organism, such as wound healing3and central nervous system (CNS) regeneration in demyelinating le....

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All animal procedures followed the 'Guide for the Care and Use of Laboratory Animals' (NIH publication, 8th edition, 2011) and were approved by the Animal Welfare Committee of Basel (Swiss Guidelines for the Care and Use of Animals). By these guidelines the animal protocol is considered of "lowest animal severity grade".

1. Preparation of Expansion Medium

Note: Work in aseptic conditions as standard for tissue culture.

  1. Take two 15 ml tubes, and add 5 ml of L-glutamine-.......

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This EMT model system is based on the standardized isolation of NSCs both as single cells or as explants from a specific region of the developing neural tube, the central cortex (Figures 1 and 2). For quantitative assessment, explants were seeded right at the center of a 500 µm grid culture dish (Figure 3). Explants from the central cortex were first exposed to FGF2 for two days, followed by additional two days in different combinati.......

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In this study a standardized system for EMT analysis utilizing NSCs is described (summarized in Supplementary Figure 3). The standardization ensures reproducibility (Table 1 and 2). The NSCs are derived from the developing cortex, a tissue that normally does not undergo EMT. This is of advantage for the analysis of early steps in EMT. Initial steps in EMT cannot be adequately studied in tumor cells that have accumulated genetic changes and may have already adopted EMT features. Moreover,.......

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The study was supported by the University of Basel Science Foundation and the Swiss National Science Foundation by a grant to MHS and AG (SNF IZLIZ3_157230). We thank: Dr. Tania Rinaldi Burkat for generously providing infrastructure; all members of the Bettler group for discussions and comments. We thank Gerhard Dorne (Leica Microsystems, Switzerland) for professional and competent installation of the Full HD MC170 video camera (Leica Microsystems, Switzerland).

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Name Company Catalog Number Comments
BMP4, rhBMP4 RnD Systems  314-BP-01M
Bovine pancreas insulin Sigma  I1882
Boyden chamber, CytoSelect cell invasion assay Cell Biolabs CBA-110 24 well plate system
Cell culture dish with grid Ibidi 500 mm dish, 35 mm 80156
CellMask Orange Life Technologies C10045 Plasma membrane dye, use at 1:1000 .
DAPI LifeTechnologies D1306 Stock at 5mg/ml. Use at 1:10000. Cancerogenic. Appropriate protection (gloves, coat, goggles) required.
DMEM/F12 1:1 medium bottle Gibco Invitrogen 21331-020
FGF2, rhFGF2 RnD Systems 233-FB-01M
Fibronectine, bovine Sigma  F4759
Glutamax supplement  Gibco Invitrogen  35050-061
Graphics software with pixel measurement feature Fiji fiji.sc/Fiji version 2.0.0-rc-30/1.49s
HBSS media Sigma  H9394
Human apo-Transferrin Sigma T1147 Possible lung irritant. Avoid inhalation. Use appropriate protection.
L-glutamine Gibco Invitrogen  25030-024
Nestin, Mouse anti Nestin antibody Genetex GTX26142 Use at 1:100, 4% PFA fixation, Triton X100 at 0.1%
Olig2, Rabbit anti Olig2 antibody Provided by Hirohide Takebayash Personal stock Use at 1:2000, 4% PFA fixation, Triton X100 at 0.1%
Penicillin/Streptomycin/Fungizone Gibco Invitrogen  15240-062
Podoplanin, Mouse anti Podoplanin antibody Acris DM3614P Use at 1:250, 4% PFA fixation, avoid Triton X100
Poly-L-ornithine Sigma  P3655
Putrescine Sigma  P5780 Skin and eye irritant. Appropriate protection required.
Sodium selenite Sigma  S5261
Sox10, Rabbit anti Sox10 antibody Millipore Chemicon AB5774 Use at 1:200, 4% PFA fixation, Triton X100 at 0.1%
TGFb1, rhTGFb1 RnD Systems 240-B-010
Uncoated Petri dishes Falcon Corning 351029

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