Diss. (sammanfattning) Umeå : Umeå universitet, 2005. / Härtill 4 uppsatser.

Thrombospondin 1 (TSP1) is a 450 kDa homotrimeric multidomain glycoprotein with fundamental roles in many cell-cell and cell-matrix interactions. These varied, and sometimes conflicting, functions are mediated by specific domains in TSP1. One region with diverse biological roles is the Ca2+ binding loops (or type 3 repeats). The biological activity of this region is determined through a complex assembly of disulfide bonds linking structure and function. Disulfide interchange in a protein is usually very specific and quite slow, unless catalysed. I have found that protein disulfide isomerase (PDI) is expressed on the surface of platelets and endothelial cells in a reduced active conformation. The presence of enzymatically active PDI on the surface of TSP1-secreting cells suggests PDI is well positioned to catalyse disulfide interchange in, and regulate the structure/function relationships of, TSP1. PDI was observed to form disulfide-linked complexes with TSP1. Moreover, incubation of platelet or fibroblast TSP1 with PDI enhanced binding of an isomer-specific anti-TSP1 antibody whose epitope is in the Ca2+ binding loops. These findings suggest that PDI may mediate disulfide bond rearrangement in both the soluble and extracellular matrix-bound forms of TSP1. TSP1 is a tight-binding competitive inhibitor of neutrophil cathepsin G; however, incubation with PDI increased the Ki for the interaction ???10-14-fold. TSP1 bound platelet-derived growth factor (PDGF) tightly in the region of the Ca2+ binding loops and supported binding of PDGF to its receptor. PDI-mediated disulfide interchange in TSP1 ablated PDGF binding, indicating that PDI-catalysed disulfide interchange in TSP1 may modulate PDGF-TSP1 complex formation and the biological activity of PDGF. Finally, PDI-catalysed isomerization of TSP1 potently affected its cell adhesive properties. Treatment of TSP1 with PDI enhanced adhesion and spreading of endothelial cells through the ??v??3 integrin receptor to TSP1, by exposure of a cryptic RGD sequence. Thus, endothelial cell surface PDI may be a physiological regulator of RGD-dependent binding to TSP1. These data suggest that cell-surface PDI may regulate the disulfide-bonded structure and certain biological functions of TSP1. In conclusion, I propose a novel mechanism for the post-translational regulation of TSP1 structure/function, which in turn may regulate certain aspects of TSP1 in vascular biology.

Endometriosis is a gynecological disease defined as the growth of endometrium outside of the uterus. Although linked to 50% of female infertility cases, current medical treatments fail to maintain fecundity. Since the survival of endometriotic lesions is dependent on their early neovascularization, antiangiogenic therapies specifically targeting blood vessel growth could be a promising therapeutic option for the treatment of endometriosis. Angiogenesis, the branching of new blood vessels from existing vasculature, promotes robust vascularization of lesions. ABT-898 (Abbott Laboratories), a thrombospondin-1 analog, induces endothelial cell apoptosis while sequestering pro-angiogenic growth factors. We postulated that ABT-898 would reduce endometriotic lesion vascularization while physiological angiogenesis and pregnancy remained unaffected in a murine model of endometriosis. The antiangiogenic effect of ABT-898 was tested in a human umbilical vein endothelial cell line revealing disruption of endothelial tube branching. Two in vivo experiments were conducted in which endometriosis was induced in female alymphoid BALB/c-Rag2-/-Il2rg-/- mice by adhering sections of human endometrium to the abdominal wall. Lesions from ABT-898 treated mice contained a reduced number of CD31+ endothelial cells and a decrease in blood flow supplying the lesion compared to 5% dextrose controls. Reproductive status was evaluated through maintenance of pregnancies up to gestation day 12 revealing unaffected implantation site structure and physiological angiogenesis. In a trans-generational study, pregnant F0 generation mice received ABT-898 or 5% dextrose injections on gestation days 7, 9, 11, 13, 15, 17, and 19. F1 generation mice were raised to reproductive age and bred resulting in litters (F2 generation) comparable in size to the F0 generation litters. Chronic exposure to ABT-898 did not affect angiogenic plasma cytokine levels in F0 generation mice. In addition, physiological angiogenesis was unaffected within the uteri of ABT-898 treated mice. Histological examination of the kidney, liver, ovary, and uterus revealed no structural abnormalities in F0 and F1 generations exposed to ABT-898. These results suggest that ABT-898 inhibits pathological angiogenesis within endometriotic lesions without affecting physiological angiogenesis involved in pregnancy and organ function across three generations of mice. Further research will establish the effects of ABT-898 on embryonic development, organ toxicity, and physiological angiogenesis in all organs. / Thesis (Master, Anatomy & Cell Biology) -- Queen's University, 2013-05-07 15:19:10.967

<p>Thrombospondin-1 (TSP-1) is a multifunctional extracellular matrix glycoprotein that is released from platelets α-granule to regulate angiogenesis process. TSP-1 is well-known as an inhibitory factor of angiogenesis that binds to angiogenesis stimulating factors, for example fibroblast growth factor 2 (FGF-2), vascular endothelial growth factor (VEGF) and hepatocyte growth factor/scatter factor (HGF/SF), to inhibit angiogenesis. We have cloned TSP-1 domains separately to allow studying of their function and effect on proliferation of human umbilical vein endothelial cells (HUVECs). We used an <em>Escherichia coli</em> expressionsvektor including poly histidin-tags and lac-promoter for induction of the seven successfully cloned domains by IPTG and arabinose. Our result shows that we have very low expression and induction of our protein in the <em>E.coli</em> by IPTG and arabinose, which is most likely due to complications associated with expressing a human protein in a prokaryotic system.</p>

Thrombospondin-1 (TSP-1) is a multifunctional extracellular matrix glycoprotein that is released from platelets α-granule to regulate angiogenesis process. TSP-1 is well-known as an inhibitory factor of angiogenesis that binds to angiogenesis stimulating factors, for example fibroblast growth factor 2 (FGF-2), vascular endothelial growth factor (VEGF) and hepatocyte growth factor/scatter factor (HGF/SF), to inhibit angiogenesis. We have cloned TSP-1 domains separately to allow studying of their function and effect on proliferation of human umbilical vein endothelial cells (HUVECs). We used an Escherichia coli expressionsvektor including poly histidin-tags and lac-promoter for induction of the seven successfully cloned domains by IPTG and arabinose. Our result shows that we have very low expression and induction of our protein in the E.coli by IPTG and arabinose, which is most likely due to complications associated with expressing a human protein in a prokaryotic system.

This thesis is an investigation of the use of thrombospondin-1 mimetic peptides for the treatment of epithelial ovarian cancer. The current standard of care for women diagnosed with ovarian cancer is surgical de-bulking followed by chemotherapeutics. Initially, this treatment regimen results in a reduction in the primary tumor, unfortunately chemoresistance and disease recurrence are problematic. Recent data has suggested a potential role for anti-angiogenic therapy for the treatment of various cancers. Therefore, the purpose of this study was to investigate the use of mimetics consisting of the anti-angiogenic domain of thrombospondin-1 (TSP-1) for the treatment of epithelial ovarian cancer (EOC) using a mouse model of the disease. The peptides were applied at various stages of tumor progression and a significant reduction in tumor size following treatment was observed. We found that not only were the peptides capable of slowing down tumor progression but they also played a role in reducing the size of established tumors. Treatment with TSP-1 mimetics also resulted in a significant reduction in secondary lesions and ascites fluid in the peritoneal cavity of animals. A significant increase in disease-free survival was also identified following long-term treatment with the peptide. Various histological studies revealed that the anti-angiogenic peptide was in fact inducing apoptosis of the endothelial cells and also re-organizing the vasculature. To determine whether this resulted in increased blood vessel profusion we applied standard chemotherapeutics in combination with TSP-1 mimetics. Experiments with radiolabelled and fluorescent chemotherapeutics demonstrated that pre-treating with TSP-1 mimetics allowed the vasculature to become normalized and resulted in an increased uptake of chemotherapeutics. Lastly, we investigated the mechanism of action of anti-angiogenic peptides. Most of the anti-tumor effects appeared to be due to the apoptotic effects of TSP-1 mimetics on the vasculature. A direct apoptotic effect on epithelial cells also was observed; however, it is uncertain how much of a role this plays. In conclusion, this study was important for identifying TSP-1 mimetic peptides as a potential therapeutic treatment for women suffering from EOC.

Limb and digit loss poses a significant problem across the animal kingdom. Ambystoma mexicanum, commonly known as the axolotl, however, is one species that has achieved a remarkable ability to bypass the misfortune associated with a lost limb. Viewed as a model organism in regenerative studies, the axolotl retains extraordinary regenerative properties well into adulthood that humans severely lack. While the basics of regeneration have been described, much about the molecular processes of regeneration is still largely unknown. Thrombospondin-1 (TSP-1), an angiogenesis inhibitor, has been identified as a potential factor to play a significant role in the regrowth of limbs. Vascularization of tissues is vital to the survival of biological structures, and TSP-1 has been shown to play a regulatory role in the development and remodeling of tissue vasculature. Here, we study the effect of a loss-of-function mutation in the tsp-1 gene on the process of limb regeneration in the axolotl. Our studies reveal that tsp-1 -/- animals lag in regeneration time, developing smaller blastemas in the first three weeks of regeneration. We show that the loss of TSP-1, however, is not deleterious to the overall process of regeneration as late stage blastemas of the -/- animals catch up in size and development to the wild type animals after three weeks. Our data suggests that while TSP-1 may be important during the initial stages, it may not be required for proper regeneration.

No / Platelet microparticle (PMP)-induced angiogenesis plays a key role in tumour metastasis and has been proposed to contribute towards cardiovascular disease by enhancing atherosclerotic plaque vulnerability. However, the mechanisms underlying PMP induced angiogenesis are ill defined. Recent reports demonstrate that PMPs deliver micro-RNAs (miRNAs) to recipient cells, controlling gene expression. We therefore evaluated whether miRNA transfer was a key regulator of PMP-induced angiogenesis. Co-culturing PMPs with human umbilical vein endothelial cells (HUVEC) on extracellular matrix gel induced robust capillary like structure formation. PMP treatment altered the release of angiogenesis modulators from HUVEC, including significantly reducing production of anti-angiogenic thrombospondin-1 (THBS-1). Both functional responses were abrogated by treating PMPs with RNase, suggesting the transfer of PMP-derived RNA was a critical event. PMPs were an abundant source of miRNA Let-7a, which was transferred to HUVEC following co-incubation. Using luciferase reporter assays we have shown that Let-7a directly targets the 3’UTR of the THBS-1 mRNA. HUVEC transfection with a Let-7a anti-sense oligonucleotide reduced the ability of PMPs to inhibit THBS-1 release, and significantly decreased PMP induced in vitro angiogenesis. Antibody neutralisation of THBS-1 reversed the anti-angiogenic effect of let-7a inhibition in PMP treated HUVEC, highlighting Let-7a dependent translational repression of THBS-1 drives angiogenesis. Importantly, plasmid overexpression of Let-7a in HUVEC alone induced robust tubule formation on extracellular matrix gel. These data reveal a new role for Let-7a in promoting angiogenesis and show for the first time PMPs induced angiogenic responses occur through miRNA regulation of HUVEC.

Ng, Ka Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 118-131). / Abstracts in English and Chinese. / Thesis Abstract --- p.i / 論文摘要 --- p.vi / Acknowledgements --- p.x / Abbreviations --- p.xii / Thesis Content --- p.xv / List of Figures --- p.xix / List of Tables --- p.xxi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Haematopoiesis --- p.1 / Chapter 1.2 --- Leukemia --- p.2 / Chapter 1.3 --- Childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) --- p.3 / Chapter 1.3.1 --- Epidemiology --- p.4 / Chapter 1.3.2 --- Causes and risk factors --- p.4 / Chapter 1.3.3 --- Clinical features --- p.6 / Chapter 1.3.4 --- Morphology --- p.6 / Chapter 1.4 --- Classification of BCP-ALL --- p.7 / Chapter 1.4.1 --- Immunophenotyping --- p.7 / Chapter 1.4.2 --- Cytogenetics and molecular genetics --- p.9 / Chapter 1.5 --- Prognostic factors --- p.13 / Chapter 1.6 --- Current treatments of BCP-ALL --- p.15 / Chapter Chapter 2 --- Literature Review --- p.18 / Chapter 2.1 --- Cytogenetics abnormalities in BCP-ALL --- p.18 / Chapter 2.1.1 --- Chromosomal translocation --- p.18 / Chapter 2.1.2 --- Aneuploidy --- p.21 / Chapter 2.2 --- Epigenetic aberrations --- p.21 / Chapter 2.2.1 --- DNA methylation --- p.22 / Chapter 2.2.2 --- Mechanism of DNA Methylation in Transcription Repression --- p.23 / Chapter 2.3 --- DNA Methylation in Normal Haematopoiesis --- p.25 / Chapter 2.4 --- DNA Methylation in Haematological Malignancies --- p.26 / Chapter 2.4.1 --- DNA methylation in ALL --- p.26 / Chapter 2.4.2 --- DNA methylation in BCP-ALL --- p.29 / Chapter 2.5 --- Angiogenesis in pathogenesis of acute leukemias --- p.30 / Chapter 2.6 --- Thrombospondin-1 (TSP-1) --- p.32 / Chapter 2.6.1 --- Structure of TSP-1 --- p.33 / Chapter 2.6.2 --- The role of TSP-1 in tumorigenesis --- p.34 / Chapter 2.6.3 --- TSP-1 mediates the activation of TGFβ --- p.36 / Chapter 2.6.4 --- TSP-1 mediates TGFβ-induced Apoptosis --- p.37 / Chapter 2.6.5 --- Association of TGFβ with normal haematopoiesis and haematological malignancies progression --- p.40 / Chapter 2.6.6 --- TSP-1 Induced Apoptosis via its Receptor CD36 --- p.42 / Chapter 2.6.7 --- THBS1 promoter hypermethylation and its association with tumorigenesis --- p.43 / Chapter 2.6.8 --- Effect of THBS1 aberrant methylation on TGFp --- p.45 / Chapter Chapter 3 --- Rationale of Study --- p.47 / Chapter Chapter 4 --- Materials and Methods --- p.52 / Chapter 4.1 --- Patient sample --- p.52 / Chapter 4.2 --- Cell lines --- p.52 / Chapter 4.3 --- Mononuclear cells isolation --- p.53 / Chapter 4.4 --- THBS1 promoter hypermethylation analysis --- p.54 / Chapter 4.4.1 --- DNA extraction from mononuclear cells and cell lines --- p.54 / Chapter 4.4.2 --- Bisulfite conversion --- p.55 / Chapter 4.4.3 --- Methylation specific PCR (MSP) --- p.55 / Chapter 4.5 --- Quantification of THBS1 mRNA expression --- p.57 / Chapter 4.5.1 --- RNA extraction --- p.57 / Chapter 4.5.2 --- Reverse transcription PCR --- p.58 / Chapter 4.5.3 --- Real-time RT-PCR --- p.58 / Chapter 4.6 --- Determination of plasma TSP-1 level --- p.59 / Chapter 4.7 --- TSP-1 treatment --- p.60 / Chapter 4.8 --- Flow cytometry analysis --- p.60 / Chapter 4.8.1 --- Annexin-V analysis --- p.60 / Chapter 4.8.2 --- Cell fixation --- p.61 / Chapter 4.8.3 --- Analysis of Caspase-3 activation --- p.62 / Chapter 4.8.4 --- "Analysis of TGFβ downstream pathway activation: Phosphorylation of Smad2/3, JNK and p38" --- p.62 / Chapter 4.9 --- Determination ofTGF-β expression --- p.63 / Chapter 4.10 --- Statistical analysis methods --- p.64 / Chapter Chapter 5 --- Results / Chapter 5.1 --- THBS1 methylation statuses in BCP-ALL patients and cell lines --- p.66 / Chapter 5.2 --- Correlation of THBS1 methylation statuses and clinico- pathological features in BCP-ALL patients --- p.68 / Chapter 5.3 --- Association of THBS1 methylation and THBS1 mRNA expression --- p.69 / Chapter 5.4 --- Effect of TSP-1 treatment on apoptosis level of BCP-ALL cells --- p.72 / Chapter 5.4.1 --- Annexin-V assay --- p.72 / Chapter 5.4.2 --- Caspase-3 activation assay --- p.75 / Chapter 5.5 --- THBS1 methylation and activation of secreted TGFβ --- p.78 / Chapter 5.6 --- Effect of TSP-1 treatment on activation of TGFβ --- p.80 / Chapter 5.7 --- The involvement ofTGFβ activation in TSP-1 induced apoptosis in BCP-ALL --- p.82 / Chapter 5.8 --- The association of TGFβ signaling pathway activities with THBS1 methylation --- p.86 / Chapter Chapter 6 --- Discussion --- p.91 / Chapter 6.1 --- THBS-1 promoter hypermethylation in BCP-ALL cell lines and patients: Correlation with expression and clinico-pathological profile --- p.93 / Chapter 6.1.1 --- THBS1 promoter hypermethylation status in childhood BCP-ALL --- p.93 / Chapter 6.1.2 --- THBS1 methylation as prognostic markers --- p.94 / Chapter 6.1.3 --- "Association of THBS1 methylation status, mRNA expression and TSP-1 protein expression in childhood BCP-ALL" --- p.96 / Chapter 6.2 --- Study of the correlation of TSP-1 induced apoptosis with the THBS1 promoter methylation status --- p.99 / Chapter 6.3 --- Elucidation of the molecular mechanisms of TSP-1 induced apoptosis: study of the involvement of TGFβ activation --- p.103 / Chapter 6.3.1 --- Latent TGFβ activation by TSP-1 in BCP-ALL and association with THBS1 methylation status --- p.103 / Chapter 6.3.2 --- TSP-1 induced cell death through activation ofTGFβ --- p.105 / Chapter 6.3.3 --- TSP-1 induced apoptotic signals via TGFβ signaling pathway --- p.107 / Chapter 6.4 --- Limitation of study --- p.113 / Chapter 6.5 --- Future studies --- p.114 / Chapter 6.5.1 --- Continuation study in TSP-1 induced TGFβ-mediated pathways --- p.114 / Chapter 6.5.2 --- Microarray analysis --- p.115 / Chapter 6.6 --- TSP-1 in treatment of childhood BCP-ALL --- p.115 / Chapter Chapter 7 --- Conclusion --- p.117 / Reference --- p.118

Angiogenesis is the growth of new blood vessels from existing vasculature; it requires the breakdown of existing blood vessel walls followed by the migration and proliferation of endothelial cells to form the new vessels. It is a complex process that is regulated by many pro- and anti-angiogenic factors and the roles of some of these factors are still unclear. Angiogenesis is a key feature of many pathological conditions including cancer, polycystic ovary syndrome and endometriosis so is an area of great research interest. There are several methods currently available for the study of angiogenesis, both in vitro and in vivo, and whilst all of these methods have enhanced understanding of angiogenesis, they also have limitations. The ovary is an excellent model for the study of angiogenesis as it undergoes intense vascular morphogenesis in a cyclical manner. The female reproductive system is unique as no other healthy adult tissue undergoes spontaneous angiogenesis. The tissues in the ovary undergo constant remodelling during both folliculogenesis and the formation and regression of the corpus luteum. Blood vessels are recruited from the ovarian stroma at the preantral stage to form vascular sheaths, in the thecal layer, which surround the developing follicle and supply nutrients, hormones and allow gaseous exchange. As follicular development progresses to the antral stage, when gonadotrophin-dependence is established, increased angiogenesis is essential to sustain development of the rapidly expanding follicle. Previous research into ovarian angiogenesis has focussed on the corpus luteum but the mechanisms of the regulation of angiogenesis during folliculogenesis need further elucidation. The work in this thesis aims to develop and utilise an in vitro angiogenesis assay using the culture of intact preantral and early antral follicles to provide a new approach to the study of follicular angiogenesis. During the course of this thesis this assay was utilised to investigate the effect of various factors on follicular angiogenesis and ovarian function. The role of the putative anti-angiogenic factor thrombospondin-1 (TSP-1) in the regulation of physiological angiogenesis was investigated using the in vitro angiogenesis assay developed during the course of this thesis and the role of TSP-1 in normal ovarian function was investigated using the culture of isolated granulosa cells. The results suggest that TSP-1 is able to inhibit angiogenesis and that it has an extravascular role in the ovary, in vitro. These findings were extended to an in vivo angiogenesis model where follicular angiogenesis was assessed by quantitative immunohistochemistry for bromodeoxyuridine and the endothelial cell marker CD31. The extravascular role for TSP-1 was also further investigated in vivo and was assessed by quantitative immunohistochemistry for activated caspase-3. The results confirmed the findings of the in vitro study, indicating that TSP-1 has antiangiogenic action and acts to clear non-dominant follicles from the ovary through the induction of atresia. Vascular endothelial growth factor (VEGF) is the main factor involved in stimulating angiogenesis and many advances have been made into elucidating the role, and the mechanisms of action, of VEGF on angiogenesis. Angiopoietin-1 (Ang-1) is considered to be one of the main factors acting in concert with VEGF to stabilise new blood vessels and its role in angiogenesis has been the subject of much discussion and controversy. This thesis investigates the effects of Ang-1 on follicular angiogenesis and development, using the in vitro angiogenesis assay, granulosa cell culture and RNA knockdown experiments. The results have shown that Ang-1 can induce follicular angiogenesis at high doses and that at low doses stimulates prosurvival pathways and inhibits apoptotic mediators. This thesis describes a novel in vitro culture system for the study of angiogenesis in ovarian follicles. Using this system the effects of various factors on follicular angiogenesis and on follicle development and survival have been investigated. Investigations into the mechanisms of action of these factors have also been performed. These studies have improved understanding of the regulation of follicular angiogenesis and have indicated extravascular roles for angiogenic factors in the ovary. Since angiogenesis is a key feature of many pathological conditions, the ability to manipulate angiogenesis and to investigate and quantify the effects of proor anti-angiogenic compounds may have important clinical implications.