Thèse soutenue

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Accès à la thèse
Auteur / Autrice : Gregory F. Lemkine
Direction : Barbara Demeneix
Type : Thèse de doctorat
Discipline(s) : Physiologie
Date : Soutenance en 2005
Etablissement(s) : Paris, Muséum national d'histoire naturelle
Ecole(s) doctorale(s) : École doctorale Sciences de la nature et de l'Homme - Évolution et écologie (Paris)
Jury : Président / Présidente : Pascale Debey
Examinateurs / Examinatrices : Bernard Zalc
Rapporteurs / Rapporteuses : Franck Bourrat, Jean-Paul Behr

Mots clés

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Résumé

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The subventricular zone (SVZ) of the adult mammalian brain harbors the neural stem cell population with potential neural regeneration and repair capacity. We describe a nonviral technique to preferentially transfect in vivo the adult neural stem cell population and its immediate progeny based on intraventricular injection of polyethyelenimines (PEl)/DNA complexes. Linear PEI is proving to be efficient, non-toxic and versatile agent for in vivo gene delivery by a number of routes. The transfected population was identified by cellular and ultra-structural evidence showing their proliferating status and expression of the specific markers GFAP and nestin. Stable activation of the lacZ reporter by cre-recombinase transfection in R26R mice demonstrated survival and migration of stem cell derivatives three months after injection. Apoptosis is thought to be the most common fate of the stem cell progeny. Introduction of a neuroprotective, antiapoptotic gene Bcl-XL can augment the number and change the histological profile of transgene-expressing cells in the SVZ. This opens up the possibility of enhancing in situ the regenerative potential of this population of cells. As well as confirming the importance of apoptosis in neural stem cell physiology, our results pave the way for further investigations of this phenomenon. This method thus provides selective targeting of the stem cell population and should allow an in-depth understanding of their biology. We thus investigated the effects of thyroid hormones on proliferation and apoptosis of stem cells in the subventricular zone as well as on migration of transgene-tagged neuroblasts out of the stem cell niche. Hypothyroidism significantly reduced all three of these processes, inhibiting generation of new cells. These data suggest that, besides the well established multiple roles of TH in early neurogenesis, TH is an essential component of the endocrine environment that activates neural stem cell growth, migration, and apoptosis. Further, the results demonstrate that the negative effects of TH on mitotic capacity have repercussion on the number of cells migrating through the RMS. Endocrine factors such as TH could be key factors to reveal regenerative potential of endogenous or grafted stem cells.