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Leung Kin Mei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 106-125). / Abstracts in English and Chinese. / Chapter CHAPTER 1 --- GENERAL INTRODUCTION --- p.1-11 / Chapter CHAPTER 2 --- ENZYMATIC REMOVAL OF CHONDROITIN SULFATES ABOLISHES THE AGE-RELATED ORDER IN THE OPTIC TRACT OF MOUSE EMBRYOS / INTRODUCTION --- p.12-13 / MATERIALS AND METHODS --- p.13-18 / RESULTS --- p.18-24 / DISCUSSION --- p.24-29 / FIGURES --- p.30-39 / Chapter CHAPTER 3 --- EXPRESSION OF PHOSPHACAN AND NEUROCAN IN THE DEVELOPING MOUSE RETINOFUGAL PATHWAY / INTRODUCTION --- p.40-42 / MATERIALS AND METHODS --- p.42-43 / RESULTS --- p.44-49 / DISCUSSION --- p.49-55 / FIGURES --- p.56-61 / Chapter CHAPTER 4 --- HEPARAN SULFATE PROTEOGLYCAN EXPRESSION IN THE OPTIC CHIASM OF MOUSE EMBRYOS / INTRODUCTION --- p.62-63 / MATERIALS AND METHODS --- p.63-65 / RESULTS --- p.66-70 / DISCUSSION --- p.70-76 / FIGURES --- p.77-82 / Chapter CHAPTER 5 --- EXPRESSION OF NEURAL CELL ADHESION MOLECULES IN THE CHIASM OF MOUSE EMBRYOS / INTRODUCTION --- p.83-85 / MATERIALS AND METHODS --- p.85-88 / RESULTS --- p.88-92 / DISCUSSION --- p.92.95 / FIGURES --- p.96-102 / Chapter CHAPTER 6 --- GERNEAL CONCLUSION --- p.103-105 / REFERENCES --- p.106-125

Polysialylated NCAM (polySia-NCAM) is re-expressed in a number of tumours, including small cell lung carcinoma and neuroblastoma and is strongly associated with aggressive, invasive and metastatic tumours in the clinic. SiRNA knockdown of the polysialyltransferases (polySTs), the enzymes responsible for polysialylation of neural cell adhesion molecule (NCAM), has been shown to abolish cell migration. PolySia-NCAM is thus a highly attractive novel therapeutic target. A library of potential polyST inhibitors has been synthesised, using substrate-based design and computational chemistry. Compounds synthesised include N-acylmannosamine analogues, thio-linked CMP-sialic acid analogues, N-acyl modified sialic acids and compounds incorporating elements of both approaches. Novel methodology development in the synthesis of many of the compounds is described, notably a novel route to N-acyl sialosides. In addition, compounds identified from in silico screening were considered. Routes to synthesis and isolation of analogues of biologically active compounds are described. Using an enzyme assay, compounds were evaluated for their ability to reduce polySia synthesis through polyST inhibition. Effects of agents on polySia expression in cells, and the ability of compounds to reduce cell migration in vitro was studied using a wound healing ‘scratch assay’. The data from these experiments revealed a number of potent modulators of polySia assembly and their efficacy in reducing cell migration, as well as the limits of the biosynthetic pathway to accept unnatural sialic acid precursors. This is the first example of polyST inhibition modulating tumour cell migration, and points to the potential of the polysialyltransferases as a therapeutic target in metastatic tumours.

Thesis (Ph. D.)--Case Western Reserve University, 2004. / [School of Medicine] Department of Neurosciences. Includes bibliographical references. Available online via OhioLINK's ETD Center.

Pluripotent stem cells (PSCs: ESCs and iPSCs) provide an excellent model system for studying neural development and function. These cells also serve as a reliable source of cell replacement for the treatment of various neurodegenerative diseases and disorders. In view of these applications of PSCs, multiple protocols have been developed to direct their differentiation into neural lineage. However, many of these protocols are limiting in terms of (a) low efficiency of generation of neural cells after long-term culture, (b) requirement of exogenous factors to induce and enhance neural differentiation and (c) supplementation of PSC culture medium with serum. Therefore, in the present study, attempts were made to achieve enhanced efficiency of neural differentiation of PSCs in the absence of exogenous molecules by employing a defined culture medium containing knockout serum replacement (KSR). KSR-based culture system was tested with our in-house-derived EGFP-transgenic ‘GS-2’ ES-cell and ‘N9’ iPS-cell lines and the wild-type ‘D3’ ES-cell line. In KSR medium, PSC-derived EBs predominantly generated neural cells from their post-attachment outgrowths and the complexity of neural networks increased as the culture progressed. Molecular phenotyping of PSC-derived neural cells was performed based on the expression of neural markers both at the mRNA and protein levels. qPCR analysis revealed the expression of markers corresponding to multiple neural cell types, including glutamatergic, GABAergic, cholinergic, serotonergic and dopaminergic neurons, astrocytes and oligodendrocytes, at various time points during the culture. RNA expression studies were confirmed via immunocytochemical analysis of the expression of neural markers. On day 15 of culture, FACS quantitation revealed the efficient generation of NES+ neural progenitors (~16-18%), MAP2+ mature neurons (~12-26%) and GFAP+ astrocytes (~30-63%) from the three PSC lines. Functional assessment of the generated neurons was performed by electrophysiological analysis of passive (RMP) and active (threshold, amplitude, FWHM and outward and inward currents) membrane properties. In order to investigate the role of default pathway in neural differentiation of PSCs in KSR medium, various strategies were employed. GS-2 ES-cells were cultured in the presence of different serum-free supplements; predominant differentiation into neural lineage was achieved in the B27-supplemented medium. The supplementation of KSR medium with BMP4 failed to show any effect of neural differentiation of GS-2 ES-cells. Also, EBs were switched between KSR- and FBS-supplemented culture conditions on day 2 or day 5 of culture. These experiments indicated that KSR medium promoted the generation of neural cell fates at the expense of differentiation to non-neural lineages. Interestingly, differentiation of P19 EC-cells in KSR medium also resulted in the predominant neural differentiation. These experiments collectively suggested the importance of default pathway in neural differentiation of PSCs in KSR medium. Additionally, efforts were made to enrich PSC-derived neural cells and also to enhance the efficiency of neural differentiation of PSCs. The removal of central EB-core from its peripheral neural outgrowth via scooping resulted in the enrichment of neural cells by ~1.3-2.1 folds. Significant increases were observed in the percentages of GS-2 ES-cell-derived MAP2+ mature neurons and GFAP+ astrocytes. Also, FGF2 supplementation of KSR medium was tested as a strategy to achieve enhanced efficiency of neural differentiation. Preliminary studies suggested an increase in the percentage of NES+ neural progenitors in the presence of FGF2. Taken together, KSR-based culture system offers a simple, defined and efficient method to achieve neural differentiation of PSCs in short time duration in the absence of exogenous factors. KSR-based culture system can be employed to generate specific neural cell types, study molecular regulation of neural differentiation and in disease modeling. Also, it can be used to develop a platform for high-throughput screening of potential neurogenic molecules and for dissecting their mechanisms of action.

Polysialylated NCAM (polySia-NCAM) is re-expressed in a number of tumours, including small cell lung carcinoma and neuroblastoma and is strongly associated with aggressive, invasive and metastatic tumours in the clinic. SiRNA knockdown of the polysialyltransferases (polySTs), the enzymes responsible for polysialylation of neural cell adhesion molecule (NCAM), has been shown to abolish cell migration. PolySia-NCAM is thus a highly attractive novel therapeutic target. A library of potential polyST inhibitors has been synthesised, using substrate-based design and computational chemistry. Compounds synthesised include N-acylmannosamine analogues, thio-linked CMP-sialic acid analogues, N-acyl modified sialic acids and compounds incorporating elements of both approaches. Novel methodology development in the synthesis of many of the compounds is described, notably a novel route to N-acyl sialosides. In addition, compounds identified from in silico screening were considered. Routes to synthesis and isolation of analogues of biologically active compounds are described. Using an enzyme assay, compounds were evaluated for their ability to reduce polySia synthesis through polyST inhibition. Effects of agents on polySia expression in cells, and the ability of compounds to reduce cell migration in vitro was studied using a wound healing ‘scratch assay’. The data from these experiments revealed a number of potent modulators of polySia assembly and their efficacy in reducing cell migration, as well as the limits of the biosynthetic pathway to accept unnatural sialic acid precursors. This is the first example of polyST inhibition modulating tumour cell migration, and points to the potential of the polysialyltransferases as a therapeutic target in metastatic tumours. / EPSRC and BACR / The full text will be available at the end of the extended embargo: 5th March 2027

Neuroblastoma is a highly metastatic and invasive tumour with poor prognosis. Despite recent advances in the treatment of neuroblastoma, mortality is still high due to uncontrolled metastatic disease, and novel therapeutic approaches for the treatment of neuroblastoma are therefore desperately needed. A potential novel approach for therapy of neuroblastoma relates to the polysialic acid decoration of the neural cell adhesion molecule (PSANCAM). PSA-NCAM is selectively re-expressed in a number of tumours including neuroblastoma, where it is thought to modulate tumour dissemination. Expression is strongly associated with poor clinical prognosis and an aggressive tumour phenotype. Inhibition of the enzymes responsible for synthesis of PSA, the polysialyltransferases (polySTs) presents a novel and selective therapeutic opportunity. The aims of the studies described in this thesis are to evaluate PSANCAM expression and function in neuroblastoma, and to develop and utilise cell-based models to pharmacologically investigate novel polyST inhibitors. PSA-NCAM was seen to be highly expressed in neuroblastoma clinical specimens and associated with phenotypes of tumour aggressiveness. A screening panel consisting of cell lines with a range of PSA-NCAM expression types was established and utilised to develop assays for pharmacologically assessing novel polyST inhibitors. Using cytidine monophosphate (CMP), a naturally-occurring inhibitor of polySTs, the robustness of the assays was confirmed before progression to evaluate novel molecules. From 16 compounds identified in an in vitro screen of polyST inhibition, three promising polyST inhibitors were identified. These promising polyST inhibitors modulated PSA-NCAM expression on the tumour cell surface and led to a significant reduction in cell migration. Therefore the work presented in this thesis suggests that targeting polySTs is a promising novel therapeutic strategy for neuroblastoma and further research in this area is warranted. / Mu'tah University and Jordan Armed Forces, Hashemite Kingdom of Jordan. / The full text will be available at the end of the extended embargo period: 5th March 2027

Traumatic brain injury (TBI) results from a physical insult to the head and often results in temporary or permanent brain dysfunction. However, the cellular pathology remains poorly understood and there are currently no clinically effective treatments. The overall goal of this work was to develop and characterize a novel three-dimensional (3-D) in vitro paradigm of neural trauma integrating a robust 3-D neural co-culture system and a well-defined biomechanical input representative of clinical TBI. Specifically, a novel 3-D neuronal-astrocytic co-culture system was characterized, establishing parameters resulting in the growth and vitality of mature 3-D networks, potentially providing enhanced physiological relevance and providing an experimental platform for the mechanistic study of neurobiological phenomena. Furthermore, an electromechanical device was developed that is capable of subjecting 3-D cell-containing matrices to a defined mechanical insult, with a predicted strain manifestation at the cellular level. Following independent development and validation, these novel 3-D neural cell and mechanical trauma paradigms were used in combination to develop a mechanically-induced model of neural degeneration and reactive astrogliosis. This in vitro surrogate model of neural degeneration and reactive astrogliosis was then exploited to assess factors influencing neural stem cell (NSC) survival and integration upon delivery to this environment, revealing that specific factors in an injured environment were detrimental to NSC survival. This work has developed enabling technologies for the in vitro study of neurobiological phenomena and responses to injury, and may aid in elucidating the complex biochemical cascades that occur after a traumatic insult. Furthermore, the novel paradigm developed here may provide a powerful experimental framework for improving treatment strategies following neural trauma, and therefore serve as a valid pre-animal test-bed.

Polysialic acid is a unique carbohydrate that decorates the surface of the neural cell adhesion molecule. Polysialic acid is an onco-developmental antigen, expressed in tumours principally of neuroendocrine origin, notably neuroblastoma, strongly correlating with invasion and metastasis. Polysialylation is regulated by two polysialyltransferase enzymes, PST (ST8SiaIV) and STX (ST8SiaII), with STX dominant in cancer. Post-development polysialic acid expression is only found at low levels in the brain, thus this could be a novel target for cancer therapy. It is hypothesized that inhibition of polysialyltransferase could lead to control of tumour dissemination and metastasis. The aims of this thesis were to develop tools and in vitro assays to screen novel polysialyltransferase inhibitors. A panel of tumour cell lines were characterised in terms of growth parameters (using the MTT assay) and polysialic acid expression. This includes a pair of isogenic C6 rat glioma cells (C6-STX and C6-WT) and naturally polysialic acid expressing neuroblastoma cells (SH-SY5Y). Following this, an in vitro assay was validated to screen modulation of polysialic acid expression by removing pre-existing polysialic acid expression using endoneuraminidase N and evaluated the amount of re-expression of polysialic acid using immunocytochemistry. Then, a functional assay was developed and validated for invasion, the matrigel invasion assay. Cytidine monophosphate (tool compound) significantly reduced polysialic acid surface expression and invasion. A panel of six novel polysialyltransferase inhibitors was screened for cytotoxicity, polysialic acid surface expression and invasion. Of the potential polysialyltransferase inhibitors evaluated, ICT3176 and ICT3172 were identified from virtual screening of Maybridge library and were emerged as the most promising inhibitors, demonstrating significant (p < 0.05) reduction in cell-surface polysialic acid re-expression and invasion in polysialic acid expressing cells. Furthermore, the specificity of compounds for polysialyltransferase (α-2,8-sialyltransferase) over other members of the wider sialyltransferase family (α-2,3- and α-2,6-sialyltransferases) was confirmed using differential lectin staining. These results demonstrated that small molecule inhibitors as STX is possible and provides suitable in vitro cell based assays to discovery more potent derivatives.