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Li, Cheuk Wun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 121-135). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

No description available.

Transforming growth factor beta (TGFβ) superfamily members are involved in controlling mammalian fertility. The largest subset of the TGFβ superfamily are the bone morphogenetic proteins (BMP). BMP ligands signal through the type I and II BMP receptors and utilise the Smads1/5/8 phosphorylation cascade to control gene expression in the cell nucleus. Although BMPs act through the same pathway, they have the ability to activate unique sets of genes dependant on the identity of the ligand. In this study, HEK293T cells were challenged with BMP ligands for four hours and gene expression profiles were compared using microarray technology. The genes upregulated in the presence of BMP2, BMP4, BMP6 and BMP7 play roles in cellular proliferation and differentiation. These functions are critical stages in the successful development of an ovarian follicle whilst undergoing folliculogenesis. All of the BMP ligands investigated in this study were also observed to upregulate the expression of a small group of common genes indicating that a shared regulatory pattern occurs within the BMP pathway. Of these genes, Smad6 and Smad7, inhibitor of DNA binding proteins 1-4 (ID 1-4), and msh homeobox homolog 2 (MSX2) were previously known BMP target genes. However, none of the remaining genes upregulated by all BMPs were previously shown to be BMP targets. The results from the microarray experiment were used as founding data for the in silico mining of novel genes not present on the array that may be differentially expressed in response to these ligands. The expression levels of several of the novel genes identified by in silico mining were then measured in vitro, however the results showed no differential expression in the HEK293T cells. To apply the knowledge of the microarray studies to the tissue of interest, eight genes were selected for assessment in ovine granulosa cells. Four of the genes upregulated in response to BMP6 in HEK293T cells were also differentially expressed in primary ovine granulosa cell cultures in response to BMP6 addition. The identification of several sheep breeds with mutations in TGFβ superfamily members has enabled investigations into the roles that specific TGFβ components play in controlling fertility. The highly fertile Booroola sheep has a substitution mutation in the type IB BMP receptor that results in an additive effect on ovulation rate. The Booroola mutation causes precocious maturation of ovarian follicles with fewer granulosa cells surrounding an enlarged oocyte, and carriers of the mutation have higher levels of circulating follicle stimulating hormone (FSH). BMPs have previously been shown to influence the regulation of FSH synthesis and secretion in the pituitary gland. In this study, primary pituitary cells were harvested and cultured from homozygous Booroola ewes and from wildtype ewes to determine if the mutation caused alterations in FSH secretion in vitro. The cells were collected 24 h following induction of luteolysis and cultured for 72 h prior to being challenged for 24 h with bone morphogenetic proteins (BMP2, BMP4, BMP6), growth and differentiation factor-9 (GDF9), transforming growth factor β1 (TGFβ1), activin-A and gonadotropin releasing hormone (GnRH). The levels of FSH and luteinising hormone (LH) were measured by radioimmunoassay and compared to the untreated controls. Primary pituitary cell cultures from Booroola ewes secreted less FSH than wildtype cells in the presence of BMP2, BMP4 and BMP6. These BMPs did not affect the FSH stores within the cells, or the levels of LH released. GDF9 appeared to act in a BMP-like manner by suppressing FSH secretion. The BMPRIB receptor however, was not found to co-localise with gonadotroph cells in either Booroola or wildtype pituitary tissues. These findings imply that the increased sensitivity of Booroola cells to BMP2, BMP4, BMP6, and GDF9 cannot be due to the direct action of the BMPRIB mutant Booroola receptor in the cells that synthesize FSH. The alternative type I BMP receptor to BMPRIB that can act in BMP signal transduction is BMPRIA. This receptor was also not found in gonadotroph cells of wildtype orBooroola ewes This is in contrast to findings in other flocks which have been shown to express BMPRIA in gonadotroph cells. This study has identified unique sets of differentially regulated genes in response to BMP-2, 4, 6, and 7 as well as TGFβ1 in a human HEK293T cell culture system. Among the differentially expressed genes, a common set of 12 genes were upregulated by all BMP ligands. None of these genes were present in the TGFβ1 set. Selected genes were validated in ovine primary granulosa cell cultures, showing that the human cell culture system functions similarly to cells of biologial relevance in fertility. Within the pituitary gland, BMPs are shown to influence FSH secretion. The presence of the Booroola mutation enhances the BMP effects on gonadotroph cells, however the lack of BMPRIB on gonadotroph cells indicates that the effects are indirect.

Osteoporotic fractures are still the major health concerns in many developed societies especially when the incidence of that tremendously increased with the aging population. However, the outcomes of osteoporotic fracture treatment have not been entirely satisfactory due to the poor quality of bone substance. Inspiringly, bone morphogenetic protein 2 (BMP2) with the ability to accelerate bone formation showed advantages over the conventional treatment. The only problem needed to overcome is its short half-life which resulted in the requirement of readministration and extremely high cost. As a solution to that, gene therapy provides a promising way to sustainably release this protein at the regeneration site. Since viral vectors have been hampered by genetic toxicity and immunogenicity, nanoscaled non-viral vectors offer an attractive means for gene delivery. Chitosan as non-viral vector has been widely investigated for its excellent biocompatibility. Most efforts have been given to improve its low transfection efficiency. In this study, chitosan was first modified with octaarginine, one of cell membrane penetrating peptides, and showed enhanced transfection activity, but which was not significant as expected. Following that, low molecular weight polyethyleminine (PEI) was introduced to modify chitosan through bioreducible disulfide linkage, denoted as Chitosan-ss-PEI. PEI is an efficient non-viral vector but hampered by molecular-weight dependent toxicity. The developed Chitosan-ss-PEI showed good biocompatibility in MTT assay in three different cell lines, during which cells were maintained 80% of viability when the concentration of this vector was up to 100 μg/mL. The optimal transfection efficiency of Chitosan-ss-PEI was higher than that of PEI 25k and comparable to Lipofectamine in delivering luciferase reporter gene. GFP expression mediated by Chitosan-ss-PEI also showed similar results. Chitosan-ss-PEI was then applied to deliver BMP2 gene to skeletal system cells and exhibited the osteogenic ability. For C2C12 myoblast cells, this system inhibited their myoblast differentiation and induced the osteogenic differentiation. It also showed stronger effect in promoting the differentiation of immature osteblast-like MG63 cells and in inducing C3H10T1/2 mesenchymal stem cells osteogenic differentiation in term of ALP activity and mineralization ability compared with other commercial available non-viral vectors. Primary MSCs such as bone marrow stromal cells (BMSC) and human umbilical cord blood mesenchymal stem cells (hUCB-MSC), are usually more difficult to transfect, but they showed stronger osteogenic differentiation ability induced by this system comparing with the cell lines. BMP2 usually requires extremely high concentration to realize its function. Through the investigation of BMP2 signaling regulation in this study, it was found that parathyroid hormone (PTH) could increase the access of BMP2 ligands to their receptors by negatively influencing BMPs antagonist network, resulted in enhanced BMP2 activity in bone remodeling and in promoting the commitment of MSC to osteoblast lineage both in vitro and in vivo. This course involved the endocytosis of PTHR with a complex of LRP6, which organized antagonist network on the cell surface to shield the BMPs receptors. Novel approaches are expected to be developed based on this mechanism with the purpose of intensifying the therapeutic effect of BMPs. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Low back pain (LBP) is associated with intervertebral disc (IVD) degeneration and exerts enormous socioeconomic burdens on the society. The nucleus pulposus (NP) is the structural and functional core of the IVD, and plays vital roles in its homeostasis. Although the etiology of IVD degeneration is not fully understood, the cellular changes of the NP have been proposed to be associated with degeneration. Conventional management for IVD degeneration primarily targets to relieve LBP and other symptoms without restoring or preserving disc function. Novel therapeutic strategies have emerged with an aim to retard or even reverse disc degeneration. In particular, the use of growth factors, such as the bone morphogenetic proteins (BMP), has received considerable attention due to their anabolic effects on extracellular matrix (ECM) synthesis by NP cells. BMP-2 and BMP-7 are of great interest for their involvement in osteogenesis, chondrogenesis, and development and maintenance of the IVD. To date, the benefits of BMP-2 on disc degeneration are controversial, given the inconsistent findings from animal model studies. The effectiveness of BMP-7 in disc repair, however, has been well demonstrated both in vitro and in vivo. A better understanding of the differences between BMP-2 and BMP-7 regulatory action on NP cells may facilitate future applications of BMP in disc repair/regeneration. This study hypothesized that BMP-2 and BMP-7 act differentially on human NP cells via different signal transduction processes. The differential effect of BMP-2 and BMP-7 was first tested in bovine NP cells using a three-dimensional culture system (alginate beads). Both BMP-2 and BMP-7 enhanced ECM production and phenotypic characteristics of bovine NP cells. Notably, BMP-7 was significantly more potent than BMP-2 in this regard. The effects of BMPs were further tested on non-degenerated (ND-NP) and degenerated (D-NP) human NP cells. The DMMB assay revealed that BMP-7 exerted a superior up-regulatory action on GAG production of D-NP cells compared to BMP-2. Furthermore, the overall response of D-NP cells to BMP-2 and BMP-7 was significantly lower than ND-NP cells. Immunohistochemical staining and quantitative RT-PCR assays demonstrated that D-NP cells possess a more fibroblastic and less chondrocyte-like phenotype than ND-NP cells. At the mRNA level, the BMP receptor BMPR1A was not expressed in D-NP cells. BMP-7, but not BMP-2, induced expression of BMPR1A in D-NP cells. On the other hand, gene expression of selected TGF-β pathway components and hypoxia pathway components were significantly up-regulated by BMP-2 but down-regulated by BMP-7. These findings suggest that D-NP cells can activate differential molecular cascades in response to BMP-2 and BMP-7. In conclusion, this study showed a superior effect of BMP7 in up-regulation of classical BMP signaling components including BMP receptor BMPR1A. The reduced responsiveness of D-NP cells to BMP-2 and BMP-7 stimulation may be related to a different expression pattern of BMP receptors. This study provides insights into the differential regulatory actions of BMP-2 and BMP-7 on human NP cells and facilitates the future application of BMPs in managing disc degeneration. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Thesis (Ph.D.)--York University, 2007. Graduate Programme in Biology. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR29321

Thesis (M.S.)--University of Michigan, 2005. / Includes bibliographical references.

Thesis (Ph. D.)--Cornell University, August, 2007. / Vita. Includes bibliographical references (leaves 99-107).

Thesis (M.S.)--Miami University, Dept. of Zoology, 2008. / Title from first page of PDF document. Includes bibliographical references (p. 24-29).