Stem cell transplantation in mouse models for Huntington's disease

Cell replacement therapies for neurodegenerative diseases using stem cells require above all a good survival of the graft and therefore an understanding of the possible influence of the surrounding degenerating tissue on the grafted cells. In this thesis, I report on the experiments of stem cell transplantation in mouse models for Huntington´s disease. The most common rodent model for HD is the QA-lesion model, where quinolinic acid is injected unilaterally into the striatum of adult rats. We adapted this method for use in mice and transplanted syngeneic embryonic and fetal neural stem cells of enhanced green fluorescent protein (EGFP)-transgenic mice into the QA-lesioned striatum. Since the glial cells react very strongly to the excitotoxic lesion, we examined both, astrocyte and microglia activation, at the site of transplantation, assuming an influence of activated glia on graft survival. In order to investigate the best timing of transplantation for the survival of donor cells, we transplanted fetal NSCs at 2, 7 and 14 days after injury. In addition, the influence of graft preparation prior to transplantation (i.e. intact neurospheres vs. dissociated cell suspension) on graft survival was investigated. At all transplantation dates we found that grafted neurospheres demonstrated better survival than single cell suspensions. By far the best survival was found when transplantation was performed early (2 days) after QA-lesion. At later transplantation dates, a decrease in graft survival was accompanied by an increasing astrocyte and microglia activation. We also investigated brain derived neurotrophic factor (BDNF)-expression in the striatum after QA-lesion, but there was no significant change in BDNF protein-level. Long term survival of NSCs transplanted 2 dpo showed that most of the cells expressed GFAP, suggesting astrocytic differentiation. Another mouse model for HD is the R6/2 mouse which carries the human exon 1 of the huntingtin gene, including the causative CAG repeats. These animals display a different neuropathology and therefore might be seen as a model for the early stage of HD. When we transplanted NSCs into the striatum of these mice, we found that graft morphology was somewhat different to that in the QA-lesioned striatum and transplanted cells expressed not only GFAP, but also the oligodendroglial precursor marker NG2. This also points to the influence of the host tissue environment on graft physiology. As a cooperation project with the research group of Prof. Melitta Schachner, we also investigated genetically manipulated embryonic NSCs after transplantation into the QA-model. Professor Schachners group transfected ES cells with the cell adhesion molecule L1 and already found an improved in vivo differentiation potential. In follow up experiments, we have investigated the possible functional outcome of such transplantations with the help of two different behavioural tests. Since a functional improvement could only be seen in one of the tests which subsequently diminished at 8 weeks after transplantation, it is not clear, whether these cells have the capacity to integrate into the tissue properly. Thus, despite the enhanced differential potential of the eNSCs, they fail to adopt the function of the missing striatal neurons. Furthermore, a number of the L1 expressing grafts went on to form tumours, highlighting the continued need for extreme vigilance when exploring the therapeutic potential of such cells.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2005

Author dc:creator

• Johann, Verena

Contributors dc:contributor

• Kosinski, Christoph Michael

• info:eu-repo/classification/ddc/570
• Biowissenschaften, Biologie

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-122746%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61062