Differentiation and neural integration of hippocampal neuronal progenitors: Signaling pathways sequentially involved

• Published in: Hippocampus Vol. 20; no. 8; pp. 949 - 961
• Main Authors: Akchiche, Nassila, Bossenmeyer-Pourié, Carine, Pourié, Grégory, Koziel, Violette, Nédélec, Emmanuelle, Guéant, Jean-Louis, Daval, Jean-Luc
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-08-2010; Wiley
• Subjects: Adenosine Triphosphate - metabolism; Animals; apoptosis; Apoptosis - drug effects; bcl-X Protein - genetics; bcl-X Protein - metabolism; Bromodeoxyuridine - metabolism; Caspases - metabolism; cell communication; Cell Differentiation - drug effects; Cell Differentiation - physiology; Cell Proliferation - drug effects; Cells, Cultured; coculture; Coculture Techniques - methods; death-associated protein kinase; Disks Large Homolog 4 Protein; Embryo, Mammalian; Enzyme Inhibitors - pharmacology; Food and Nutrition; Gene Expression Regulation - drug effects; Hippocampus - cytology; Imidazoles - pharmacology; Intercellular Signaling Peptides and Proteins - pharmacology; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Life Sciences; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mitochondrial Membranes - physiology; Mitogen-Activated Protein Kinase Kinases - metabolism; Neurons - drug effects; Neurons - physiology; p38; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Rats; Rats, Wistar; Signal Transduction - drug effects; Signal Transduction - physiology; Stem Cells - drug effects; Stem Cells - physiology; survival; Time Factors; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - metabolism; Vesicular Glutamate Transport Protein 2 - genetics; Vesicular Glutamate Transport Protein 2 - metabolism
• ISSN: 1050-9631; 1098-1063
• DOI: 10.1002/hipo.20690

In the context of their potential implication in regenerative strategies, we characterized cell mechanisms underlying the fate of embryonic rat hippocampal H19–7 progenitors in culture upon induction of their differentiation, and tested their capacities to integrate into a neuronal network in vitro. Without addition of growth factors, nearly 100% of cells expressed various neuronal markers, with a progressive rise of the expression of Synapsin I and II, suggesting that cells developed as mature neurons with synaptogenic capacities. Fully differentiated neurons were identified as glutamatergic and expressed the receptor‐associated protein PSD‐95. Quantification of ATP showed that 60% of cells died within 24 h after differentiation. Cell death was shown to imply Erk1/2‐dependent intrinsic mitochondrial apoptosis signaling pathway, with activation of caspase‐9 and ‐3, finally leading to single‐strand DNA. Surviving neurons displayed high levels of Akt, phospho‐Akt, and antiapoptotic proteins such as Bcl‐2 and Bcl‐XL, with decreased caspase activation. In the absence of trophic support, the proapoptotic death‐associated protein (DAP) kinase was dramatically stimulated by 24 h postdifferentiation, along with increased levels of p38 and phospho‐p38, and caspase reactivation. These findings show that different signaling pathways are sequentially triggered by differentiation, and highlight that ultimate cell death would involve p38 and DAP kinase activation. This was supported by the improvement of cell survival at 24‐h postdifferentiation when cells were treated by PD169316, a specific inhibitor of p38. Finally, when seeded on rat hippocampal primary cultured neurons, a significant number of differentiated H19–7 cells were able to survive and to develop cell–cell communication. © 2009 Wiley‐Liss, Inc.