Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2006. / Robert McKeon, Committee Member ; Robert Lee, Committee Member ; Robert Guldberg, Committee Member ; Ravi Bellamkonda, Committee Member ; Michelle LaPlaca, Committee Chair. Vita.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 267-326). Also available in print.

Introduction Neurogenesis, the development of new neurons, starts soon after the formation of the neural tube and is largely completed by birth. Development of the brain after birth is mainly reliant on the formation of new connections between surviving neurons. However, adult neurogenesis does continue in the subgranular zone of the hippocampus from quiescent adult neural stem cells. Traditionally neural stem cells were cultured as neurospheres, a heterogeneous agglomeration of neural cells at various stages of differentiation. This heterogeneity prevented accurate quantitative analysis. In 2008 Sun et al produced the first non-immortalised human foetal neural stem (NS) cell line from nine week old human foetal cortex. These cells are cultured as monolayers, have a radial glia like appearance, self renew and form all three neural cell types, neurons, astrocytes and oligodendrocytes upon differentiation. More recently human foetal neuroepithelial like (NES) stem cells have been produced from five week old human foetal hind-brain, they resemble neuroepithelial cells, with characteristic rosettes, upon differentiation they appear to form a pure population of neurons. These homogeneous monolayer cultures enable quantitative proteomic analysis, to increase our understanding of early brain development Methods Three NES and two NS cell lines were available for analysis. They proliferate by stimulation from FGF and EGF, removal of these growth factors results in spontaneous differentiation. Proliferating NES and NS cells were compared using SILAC labelling. In addition, each cell line was differentiated for 12 days, 6 timepoints were taken and compared using label free quantitation. Results 4677 proteins were quantitated with 473 differentially expressed, revealing fundamental differences between NES and NS cells. NES cells are less differentiated, expressing SOX2 and LIN28, have active cell cycle processes, DNA elongation, histone modification and miRNA mediated gene silencing. Whereas NS cells are more developmentally defined, express multiple membrane proteins, have activated focal adhesion, thereby increasing their binding and interaction with their environment. NS metabolism is more oxidative, utilises lipid metabolism, the pentose phosphate pathway and produces creatine phosphate. Upon differentiation the cell cycle processes are downregulated and neurogenic and gliogenic processes increased. Conclusion This work represent a detailed in vitro characterisation of non immortalised human foetal neural stem cells, it describes the regulatory, metabolic and structural changes occurring within neural stem cells in early brain development. The information herein points towards de-differentiation potentially through LIN28-let7, as a means to produce more neurogenic neural stem cells in vitro thus aiding regenerative therapies, as well as provides a wealth of information for better understanding neurological developmental disorders.

As the prevalence of Parkinson’s disease is expected to increase gradually over the years based on recent scientific predictions, developing a treatment plan to mitigate the development of this disease is essential. Previous research tried to tackle the motor and non-motor symptoms associated with the disease. That said, some symptoms seem to persist, and the quality of life of PD patients continues to decline. Zebrafish have emerged as a strong model to study the regeneration of DAergic neurons as they have the ability to show robust adult neurogenesis. Here, we used adult zebrafish to investigate DAergic neuron regeneration following ablation in various brain regions. In addition, we tested the efficacy of Nifurpirinol, an alternative substrate to MTZ, in ablating DAergic neurons in the adult zebrafish brain. Lastly, we tracked how the ablation of DAergic neurons influences the motor activity of adult zebrafish and how they tend to recover over time. Results showed a significant reduction in DAergic neurons at 7 days following the MTZ treatment in the olfactory bulb, telencephalon, and the periventricular pretectal nucleus. NFP also caused similar changes, albeit they were less statistically significant. In response to ablated DAergic neurons, MTZ-treated fish showed a significant increase in the number of neural stem cells undergoing proliferation at 1 dpt. However, the highest spike in proliferative cells, especially neural stem cells, was found at 7 dpt. This time point corresponded with the greatest decrease in DAergic neurons following ablation. These cellular changes were observed in the olfactory bulb and the telencephalon. That said, more drastic changes were noticed in the rostral and medial telencephalon. Results also showed that the adult zebrafish brain was not able to significantly replenish the number of DAergic neurons as early as 15 dpt. Based on previous observations, it seems that adult zebrafish need at least 45 days to regenerate their DAergic neurons to levels comparable to the DMSO control. Lastly, behaviour analysis showed that NFP has the most significant impact on motor activity across three different parameters at 0 hpt. MTZ also had similar effects on motor activity; however, it was less pronounced. The impact on the behaviour level seems more transient as some recovery was observed at 7 dpt. Overall, this transgenic zebrafish line allowed us to explore how and when the adult zebrafish brain was able to efficiently recover following the specific ablation of DAergic neurons. In addition, it expanded our understanding of adult neurogenesis which will hopefully allow us to better approach patients with Parkinson’s disease.

No description available.

An essential component of developing successful neural stem cell (NSC)-based therapies involves the establishment of methodologies to noninvasively monitor grafted NSCs within brain tissues in real time. In this context, ex vivo labeling with ultrasmall superparamagnetic iron oxide (USPIO) particles has been shown to enable efficient tracking of transplanted NSCs via magnetic resonance imaging (MRI). However, whether and how USPIO labeling affects the intrinsic biology of NSCs is not thoroughly understood, and remains an active area of investigation. Here, we perform a comprehensive examination of rat NSC survival and regenerative function upon labeling with the USPIO, Molday ION Rhodamine B (MIRB), which allows for dual magnetic resonance and optical imaging. After optimization of labeling efficiency, two specific doses of MIRB (20 and 50 mu g/mL) were chosen and were followed for the rest of the study. We observed that both MIRB doses supported the robust detection of NSCs, over an extended period of time in vitro and in vivo after transplantation into the striata of host rats, using MRI and post hoc fluorescence imaging. Both in culture and after neural transplantation, the higher 50 mu g/mL MIRB dose significantly reduced the survival, proliferation, and differentiation rate of the NSCs. Interestingly, although the lower 20 mu g/mL MIRB labeling did not produce overtly negative effects, it increased the proliferation and glial differentiation of the NSCs. Additionally, application of this dose also changed the morphological characteristics of neurons and glia produced after NSC differentiation. Importantly, the transplantation of NSCs labeled with either of the two MIRB doses upregulated the immune response in recipient animals. In particular, in animals receiving the 50 mu g/mL MIRB-labeled NSCs, this immune response consisted of an increased number of CD68(+)-activated microglia, which appeared to have phagocytosed MIRB particles and cells contributing to an exaggerated MRI signal dropout in the animals. Overall, these results indicate that although USPIO particles, such as MIRB, may have advantageous labeling and magnetic resonance-sensitive features for NSC tracking, a further examination of their effects might be necessary before they can be used in clinical scenarios of cell-based transplantation.

The murine subventricular zone (SVZ) in a brain contains a population of stem cells and daily produces tens of thousands of neurons throughout lifetime. However, the mechanisms of SVZ neural stem/progenitor cell (NSPC) maintenance, differentiation and cell-fate specification are still not clear. To understand these parameters via histone methylations with bivalent mechanism, the SVZ NSPCs were first isolated by using a culture technique called neurosphere assay (NSA). It has been a challenge to culture pure cell populations of SVZ subtypes, so the NSA was initially validated. The H3K27me3 mark, which has a dominant role in the bivalent mechanism, has not been studied in postnatal and adult SVZ in vivo, yet their role has been implicated to control the shift of embryonic cortical neurogenesis to gliogenesis. Therefore, we have first investigated whether H3K27me3 marks are present in the postnatal and adult SVZ NSPC population and whether their marks have been changed after stroke or demyelination in central nervous system (CNS) by immunohistrochemistry. With the confirmation of H3K27me3 mark present in SVZ NSPCs, the presence of H3K27me3 catalyzer, called polycomb repressive complex 2 (PRC2) core components (Eed, Ezh2, Suz12) including Jarid2, was investigated and confirmed in postnatal SVZ in vitro by qRT-PCR and Western blot. To understand the role of PRC2 enzymatic activity in postnatal SVZ neurosphere self-renewal and multipotency, Eed was down-regulated by using lentiviral mediated delivery of shRNA. Also, PRC2 dependent or independent function of Jarid2 was examined via knockdown approach. The lack of Eed in the neurospheres resulted the attenuation of self-renewal and oligodendrogenesis, whereas the Jarid2 knockdown neurospheres showed the decreased proliferation with no SVZ NSPC differentiation. Based on these knockdown studies, it suggests Eed and Jarid2 might not share their function in the postnatal SVZ NSPCs to govern postnatal SVZ NSPC self-renewal and multipotency.

Although it is known that the regenerative function of neural stem/progenitor cells (NSPCs) declines with age, causal mechanisms underlying this phenomenon are not understood. Here, we systematically analyze subventricular zone (SVZ) NSPCs, in various groups of rats across the aging spectrum, using in vitro and in vivo histological and behavioral techniques. These studies indicate that although NSPC function continuously declines with advancing age, there is a critical time period during middle age (13-15 months) when a striking reduction in NSPC survival and regeneration (proliferation and neuronal differentiation) occurs. The studies also indicate that this specific temporal pattern of NSPC deterioration is functionally relevant at a behavioral level and correlates with the decreasing expression of the redox-sensitive transcription factor, Nrf2, in the NSPCs. When Nrf2 expression was suppressed in 'young' NSPCs, using short interfering RNAs, the survival and regeneration of the NSPCs was significantly compromised and mirrored 'old' NSPCs. Conversely, Nrf2 overexpression in 'old' NSPCs rendered them similar to 'young' NSPCs, and they showed increased survival and regeneration. Furthermore, examination of newborn Nrf2 knockout (Nrf2-/-) mice revealed a lower number of SVZ NSPCs in these animals, when compared to wild-type controls. In addition, the proliferative and neurogenic potential of the NSPCs was also compromised in the Nrf2-/- mice. These results identify a novel regulatory role for Nrf2 in NSPC function during aging and have important implications for developing NSPC-based strategies to support healthy aging and to treat age-related neurodegenerative disorders.

The Gangliosidoses, to include GM1 gangliosidosis and Sandhoff disease are a class of incurable lysosomal storage disorders characterized by an abnormal accumulation of gangliosides leading to progressive neurodegeneration and eventually death. GM1 gangliosidosis is caused by a genetic defect in the lysosomal-specific acid β-galactosidase, which results in the massive accumulation of ganglioside GM1 primarily in the central nervous system (CNS). Sandhoff disease (SD) results from a defect in the β-subunit of β- Hexosaminidase A and leads to the accumulation of ganglioside GM2 and its asialo derivative (GA2). As there are no effective therapies for these glycosphingolipid (GSL) storage disorders, I studied substrate reduction therapy (SRT), stem cell therapy, and adeno-associated viral (AAV) gene therapy in neonatal mice as early intervention therapies and were effective in reducing CNS GSL storage. In addition, AAV gene therapy was also evaluated in the adult GM1 gangliosidosis mice. Furthermore, analysis of the brain lipids in mice, cats, and humans with Sandhoff disease revealed that the SD cat model is intermediate between the SD mouse and the SD patient with respect to GM2 and GA2 accumulation. These findings are the first to compare the different therapies and provide valuable information for the translation of mouse studies to clinical trials in patients. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

Specific regions within the adult mammalian brain maintain the ability to generate neurons. The largest of these, the ventricular-subventricular zone (V-SVZ), comprises the entire lateral wall of the lateral ventricles. Here, a subset of glial fibrillary acid protein (GFAP)-positive astrocytes (B cells) gives rise to neurons and oligodendrocytes throughout life. This process of neurogenesis involves quiescent B cells becoming proliferative (epidermal growth factor receptor (EGFR)-positive) and giving rise to neuroblasts via transit amplifying precursors. The neuroblasts then migrate through the rostral migratory stream (RMS) to the olfactory bulbs (OBs), where they mature into neurons. Studying the stem cells in the V-SVZ has been hindered by the shortage of molecular markers to selectively target them. Using microarray and qPCR analysis of putative quiescent neural stem cells we determined that they were enriched for PDGFRβ mRNA. We used immunostaining to determine the in vivo identity of PDGFRβ+ cells, and discovered that only GFAP+ cells within the V-SVZ stem cell lineage express PDGFRβ. Moreover, these PDGFRβ+ B cells contact the ventricle at the center of ependymal pinwheel structures and the vast majority of them are EGFR-. Importantly, the V-SVZ/RMS/OBcore axis was highly enriched for PDGFRβ expression compared with other brain regions. Detailed morphological analyses of PDGFRβ+ B cells revealed primary cilia at their apical process in contact with the ventricle and long radial processes contacting blood vessels deep within the V-SVZ, both of which are characteristics of adult neural stem cells. When PDGFRβ+ cells were lineage traced in vivo they formed olfactory bulb neurons. Using fluorescence-activated cell sorting (FACS) to purify PDGFRβ+ astrocytes we discovered this receptor is expressed by all adult V-SVZ neural stem cells, including a novel population of EGFR+ PDGFRβ+ cells which correspond to the activated neural stem cells. RNA-sequencing analysis of the purified populations revealed that PDGFRβ+ EGFR+ cells possess a transcriptional profile intermediate between quiescent neural stem cells and actively proliferating GFAP- progenitor cells. Finally, when PDGFRβ is deleted in adult GFAP+ NSCs we observe a decrease in EGFR+ and Dcx+ progenitor cells, together with an increase in quiescent GFAP+ astrocytes. A larger proportion of these mutant cells come in contact with the ventricular lumen, suggesting that PDGFRβ is required for V-SVZ astrocytes to act as stem cells, possibly by mediating interactions with their niche. Taken together, these data identify PDGFRβ as a novel marker for adult V-SVZ neural stem cells that is an important regulator of their stem cell capabilities.