In Vivo Monitoring of Adult Neurogenesis in Health and Disease

Adult neurogenesis, i.e., the generation of new neurons in the adult brain, presents an enormous potential for regenerative therapies of the central nervous system. While 5-bromo-2′-deoxyuridine labeling and subsequent histology or immunohistochemistry for cell-type-specific markers is still the gold standard in studies of neurogenesis, novel techniques, and tools for in vivo imaging of neurogenesis have been recently developed and successfully applied. Here, we review the latest progress on these developments, in particular in the area of magnetic resonance imaging (MRI) and optical imaging. In vivo in situ labeling of neural progenitor cells (NPCs) with micron-sized iron oxide particles enables longitudinal visualization of endogenous progenitor cell migration by MRI. The possibility of genetic labeling for cellular MRI was demonstrated by using the iron storage protein ferritin as the MR reporter-gene. However, reliable and consistent results using ferritin imaging for monitoring endogenous progenitor cell migration have not yet been reported. In contrast, genetic labeling of NPCs with a fluorescent or bioluminescent reporter has led to the development of some powerful tools for in vivo imaging of neurogenesis. Here, two strategies, i.e., viral labeling of stem/progenitor cells and transgenic approaches, have been used. In addition, the use of specific promoters for neuronal progenitor cells such as doublecortin increases the neurogenesis-specificity of the labeling. Naturally, the ultimate challenge will be to develop neurogenesis imaging methods applicable in humans. Therefore, we certainly need to consider other modalities such as positron emission tomography and proton magnetic resonance spectroscopy (1H-MRS), which have already been implemented for both animals and humans. Further improvements of sensitivity and neurogenesis-specificity are nevertheless required for all imaging techniques currently available

Are subventricular zone endogenous neural stem cells responsible for the remyelination of the corpus callosum in the Cuprizone mouse model? An in-vivo bioluminescence and magnetic resonance imaging study

Guglielmetti C., Praet J., Vreys R., Rangarajan J.R., Maes F., Verhoye M., Ponsaerts P., Van der Linden A., ''Are subventricular zone endogenous neural stem cells responsible for the remyelination of the corpus callosum in the Cuprizone mouse model? An in-vivo bioluminescence and magnetic resonance imaging study'', World molecular imaging congress - WMIC 2012, September 5-8, 2012, Dublin, Ireland.status: publishe

MRI visualization of endogenous neural progenitor cell migration along the RMS in the adult mouse brain: Validation of various MPIO labeling strategies

The adult rodent brain contains neural progenitor cells (NPCs), generated in the subventricular zone (SVZ), which migrate along the rostral migratory stream (RMS) towards the olfactory bulb (OB) where they differentiate into neurons. The aim of this study was to visualize endogenous NPC migration along the RMS with magnetic resonance imaging (MRI) in adult healthy mice. We evaluated various in situ (in vivo) labeling approaches using micron-sized iron oxide particles (MPIOs) on their efficiency to label endogenous NPCs. In situ labeling and visualization of migrating NPCs were analyzed by a longitudinal MRI study and validated with histology. Here, we visualized endogenous NPC migration in the mouse brain by in vivo MRI and demonstrated accumulation of MPIO-labeled NPCs in the OB over time with ex vivo MRI. Furthermore, we investigated the influence of in situ injection of MPIOs on adult neurogenesis. Quantitative analysis of bromodeoxyuridine labeled cells revealed altered proliferation in the SVZ and NPC migration after in situ MPIO injection. From the labeling strategies presented in this report, intraventricular injection of a small number of MPIOs combined with the transfection agent poly-L-lysine hydrobromide was the best method as labeling of the NPCs was successful and proliferation in the SVZ was only marginally affected. While MRI visualization of endogenous NPC migration can provide insight into aberrant NPC migration in disease models, this work emphasizes the importance to carefully explore the impact on adult neurogenesis when new in situ labeling strategies are developed.status: publishe

Multimodal imaging of subventricular zone neural stem/progenitor cells in the cuprizone mouse model reveals increased neurogenic potential for the olfactory bulb pathway, but no contribution to remyelination of the corpus callosum

Multiple sclerosis is a devastating demyelinating disease of the central nervous system (CNS) in which endogenous remyelination, and thus recovery, often fails. Although the cuprizone mouse model allowed elucidation of many molecular factors governing remyelination, currently very little is known about the spatial origin of the oligodendrocyte progenitor cells that initiate remyelination in this model. Therefore, we here investigated in this model whether subventricular zone (SVZ) neural stem/progenitor cells (NSPCs) contribute to remyelination of the splenium following cuprizone-induced demyelination. Experimentally, from the day of in situ NSPC labeling, C57BL/6J mice were fed a 0.2% cuprizone diet during a 4-week period and then left to recover on a normal diet for 8weeks. Two in situ labeling strategies were employed: (i) NSPCs were labeled by intraventricular injection of micron-sized iron oxide particles and then followed up longitudinally by means of magnetic resonance imaging (MRI), and (ii) SVZ NSPCs were transduced with a lentiviral vector encoding the eGFP and Luciferase reporter proteins for longitudinal monitoring by means of in vivo bioluminescence imaging (BLI). In contrast to preceding suggestions, no migration of SVZ NSPC towards the demyelinated splenium was observed using both MRI and BLI, and further validated by histological analysis, thereby demonstrating that SVZ NSPCs are unable to contribute directly to remyelination of the splenium in the cuprizone model. Interestingly, using longitudinal BLI analysis and confirmed by histological analysis, an increased migration of SVZ NSPC-derived neuroblasts towards the olfactory bulb was observed following cuprizone treatment, indicative for a potential link between CNS inflammation and increased neurogenesis.Guglielmetti C., Praet J., Rangarajan J.R., Vreys R., De Vocht N., Maes F., Verhoye M., Ponsaerts P., Van der Linden A., ''Multimodal imaging of subventricular zone neural stem/progenitor cells in the cuprizone mouse model reveals increased neurogenic potential for the olfactory bulb pathway, but no contribution to remyelination of the corpus callosum'', NeuroImage, vol. 86, no. 1, pp. 99-110, February 2014.status: publishe

Multimodal imaging of subventricular zone neural stem/progenitor cells in the cuprizone mouse model reveals increased neurogenic potential for the olfactory bulb pathway, but no contribution to remyelination of the corpus callosum

AbstractMultiple sclerosis is a devastating demyelinating disease of the central nervous system (CNS) in which endogenous remyelination, and thus recovery, often fails. Although the cuprizone mouse model allowed elucidation of many molecular factors governing remyelination, currently very little is known about the spatial origin of the oligodendrocyte progenitor cells that initiate remyelination in this model. Therefore, we here investigated in this model whether subventricular zone (SVZ) neural stem/progenitor cells (NSPCs) contribute to remyelination of the splenium following cuprizone-induced demyelination. Experimentally, from the day of in situ NSPC labeling, C57BL/6J mice were fed a 0.2% cuprizone diet during a 4-week period and then left to recover on a normal diet for 8weeks. Two in situ labeling strategies were employed: (i) NSPCs were labeled by intraventricular injection of micron-sized iron oxide particles and then followed up longitudinally by means of magnetic resonance imaging (MRI), and (ii) SVZ NSPCs were transduced with a lentiviral vector encoding the eGFP and Luciferase reporter proteins for longitudinal monitoring by means of in vivo bioluminescence imaging (BLI). In contrast to preceding suggestions, no migration of SVZ NSPC towards the demyelinated splenium was observed using both MRI and BLI, and further validated by histological analysis, thereby demonstrating that SVZ NSPCs are unable to contribute directly to remyelination of the splenium in the cuprizone model. Interestingly, using longitudinal BLI analysis and confirmed by histological analysis, an increased migration of SVZ NSPC-derived neuroblasts towards the olfactory bulb was observed following cuprizone treatment, indicative for a potential link between CNS inflammation and increased neurogenesis

Tracking of ferritin-labeled endogenous neuroblast migration in mouse brain with MRI

Vande Velde G., Rangarajan J.R., Vreys R., Dresselaers T., Van der Linden A., Debyser Z., Baekelandt V., Maes F., Himmelreich U., ''Tracking of ferritin-labeled endogenous neuroblast migration in mouse brain with MRI'', World molecular imaging congress - WMIC 2011, September 7-10, 2011, San Diego, California, USA.status: publishe