Medicine and Health Sciences Commons^™

Mechanisms Underlying Stem Cell Depletion In Ageing., Mackenzie Hsu

Electronic Thesis and Dissertation Repository

As we age, our bodies lose the ability to repair damaged tissues. This impairment may be due to age-related deficits in our regenerative stem cells. Stem cells reside in specialized areas called stem cell niches. Ageing may cause alterations in the stem cells directly or may alter the stem cell niche to generate deficits. However, systematic studies mapping stem cell deficits and alterations to stem cell niche are lacking. Here, I investigated the bone marrows of young and aged mice to determine age-related changes in the microenvironment that may alter resident stem cells.

To achieve my research objective, I examined …

Mechanisms Underlying Enhanced Bone Marrow Adipogenesis In Diabetes, Jina J.Y. Kum

Electronic Thesis and Dissertation Repository

Morbidity and mortality associated with diabetes are due to secondary vascular complications that include both micro- and macro-vascular organ dysfunctions. Our recent studies show that vascular dysfunction and inadequate vessel repair in diabetes may potentially be due to impaired vasculogenesis (de novo vessel formation). Specifically, we have shown that diabetes enhances adipogenesis in the bone marrow and reduces the number of marrow-resident vascular regenerative stem cells. In this study, I have determined the mechanisms of deleterious bone marrow adipogenesis, which may alter the cellular composition of the marrow and lead to the depletion of vascular regenerative stem cells.

My …

Trna Regulation In Humans: The Cellular Effect Of A Pathological Hars Y454s Mutation, Rosan Kenana

Electronic Thesis and Dissertation Repository

tRNAs are the adapter molecules involved in translating the genetic code into functional protein in a living cell. tRNAs are charged with their cognate amino acids - by aminoacyl-tRNA synthetases (aaRS or ARS) - which are then transferred to a growing peptide in a process called mRNA translation. The efficiency of translation is dependent on the ratio of ARS enzymes to their cognate tRNAs and the availability of correctly amino acylated tRNAs. Disruptions of this process, caused by mutations in ARS genes, in particular, have been linked to complex inherited diseases. USH3B syndrome, a recessively inherited disorder among consanguineous families …

Novel Imaging Tools Reveal The Dynamics Of The Myocardial Growth Hormone Secretagogue Receptor In Heart Disease And Heart Failure, Rebecca Sullivan

Electronic Thesis and Dissertation Repository

Heart disease (HD) is the leading cause of mortality worldwide. Currently, diagnosis is based on clinical features, imaging, and circulating cardiac biomarkers. Cardiac imaging technologies, such as echocardiography and cardiac magnetic resonance imaging (cMRI), enable the non-invasive detection of changes in heart function. Although these modalities can detect changes in structure and anatomy, it is usually at later stages, where prevention may not be possible. In conjunction with imaging, circulating biomarkers of heart failure (HF), notably B-type natriuretic peptide (BNP) and cardiac troponin I and T, can be detected with increased levels in the blood. These biomarkers are associated with …

Implications Of Long Non-Coding Rnas In The Pathogenesis Of Diabetic Retinopathy: A Novel Epigenetic Paradigm., Saumik Biswas

Electronic Thesis and Dissertation Repository

With the rising incidence of diabetic retinopathy (DR), there is an urgent need for novel therapies. Presently, several altered metabolic pathways have been implicated in the pathogenesis of DR. Recent advances in genomic technologies have identified considerable epigenetic alterations that also contribute to DR progression. Long non-coding RNAs (lncRNAs; >200 nucleotides), critical regulators of gene expression, are aberrantly expressed in DR and have not been comprehensively characterized. Our microarray analyses using human retinal endothelial cells (HRECs) revealed thousands of differentially expressed lncRNAs following high glucose (HG) exposure, with profound increases in the lncRNAs MALAT1 and HOTAIR. Using multiple techniques, …

Discovery Of Novel Mechanisms Regulating Cancer Extravasation In The Chorioallantoic Membrane Model, Yohan Kim

Electronic Thesis and Dissertation Repository

Cancer metastasis is a multistep process that begins with the invasion of tumour cells into the stroma and migration towards the blood vessels. Tumour cells that have entered the bloodstream must then survive and leave by a process known as extravasation. Finally, extravasated cells proliferate and establish the secondary site in the metastatic cascade. Although extravasation encompasses key events during cancer cell invasion to aid in the development of effective treatments, an in vivo model that rapidly, reproducibly and economically recapitulates cancer cell extravasation is needed. Therefore, the objectives of my research were to 1) establish and validate an in …

The Role Of The Tau N-Terminal Phosphatase-Activating Domain And Phosphorylation At Thr175 In The Formation Of Tau Cytoplasmic Inclusions, Matthew A. Hintermayer

Electronic Thesis and Dissertation Repository

Cytoplasmic inclusions and fibrils of the microtubule-associated protein tau (tau protein) are a key neuropathological hallmark in tauopathies, including Alzheimer’s disease, chronic traumatic encephalopathy, and amyotrophic lateral sclerosis with cognitive impairment. Previous research has demonstrated that the phosphorylation of tau protein at Thr¹⁷⁵ is sufficient for the initiation of fibril formation both in vitro and in vivo. Here we use mutated tau protein constructs to demonstrate that phosphorylation at Thr¹⁷⁵ results in the aberrant exposure of an N-terminal phosphatase-activating domain (PAD). The tau PAD interacts with protein phosphatase 1 (PP1) leading to the activation of glycogen synthase …

Modulation Of Inflammation Driven Wound Healing After Glaucoma Surgery, James J. Armstrong

Electronic Thesis and Dissertation Repository

Dysregulated wound healing contributes to most currently unanswered ophthalmological morbidity. Opacification and structure altering contractures compromise the delicate ocular anatomy upon which ocular function and healthy vision are reliant. Glaucoma filtration surgery, corneal stromal injury, proliferative vitreoretinopathy and age-related macular degeneration are major contributors to ocular morbidity – all with myofibroblast transdifferentiation and pathognomonic scarring activity at their core.

This thesis aims to revaluate the means by which dysregulated ocular wound healing is combated with evidence describing a novel strategy to mitigate its effects. A translational approach was used. An initial retrospective analysis of over ten thousand glaucoma surgeries found …

Effects Of Maternal Protein Restriction On The Pulmonary Surfactant System During The Early Life And Adulthood, Reza Khazaee

Electronic Thesis and Dissertation Repository

Fetal growth restriction (FGR) is defined by low birth weight and contributes to a variety of adult-onset diseases with different severities between males and females. However, the effects of FGR on the pulmonary surfactant are not fully elucidated. In this thesis, first, we investigated the FGR effects on the lung function and the surfactant system at the early postnatal life. It was hypothesized that FGR contributes to alterations of lung mechanics and the surfactant system during the neonatal period. Second, we assessed the FGR effects on the surfactant system in response to sepsis in adulthood. It was hypothesized that FGR …

The Epidemiology Of Infective Endocarditis Among People Who Inject Drugs In London, Ontario., Brian Hallam

Electronic Thesis and Dissertation Repository

Infective endocarditis is an infectious disease that affects the valves of the heart. Injection drug use is currently a leading risk factor among patients with endocarditis. We conducted a prospective study using data from hospital chart records among patients with endocarditis in London, Ontario, which has a relatively high prevalence of people who inject drugs to assess the severity of the issue and the major risk factors of mortality pertaining to this population. This study had a sample size of 353 and included a review of the incidence of admissions of endocarditis, as well as a survival analysis, using both …

Kallikrein-Related Peptidases Are Dysregulated In Pleomorphic Adenoma, Matthew D. Morrison

Electronic Thesis and Dissertation Repository

Objectives: Pleomorphic adenoma (PA) is the most common benign salivary gland tumor. Kallikrein-related peptidases (KLKs) have been identified as biomarkers in many human tumors and may influence tumor behavior. We investigated KLK1-15 messenger ribonucleic acid (mRNA) and proteins in PA specimens to determine a KLK expression profile for this tumor.

Methods: Fresh frozen PA tissue specimens (n = 26) and matched controls were subjected to RT-qPCR to detect KLK1-15 mRNA. Expression of KLK1, KLK12, KLK13 and KLK8 proteins were then evaluated via immunostaining techniques. Statistical analyses were performed with the level of significance set at P < .05.

Results: We observed downregulation …

Crispr Screen For Identification Of Kinases That Mediate Prostate Cancer Cell Invasion, Hamad Aldhafeeri

Electronic Thesis and Dissertation Repository

Metastasis is the primary cause of mortality in cancer patients. Inhibition of proteins that are involved in the regulation of metastasis are expected to suppress metastasis and represent treatment targets. Our focus is on prostate cancer metastasis and we have developed a novel high-throughput means of performing in vitro screens for regulators of prostate cancer metastasis. We propose to use a focused CRISPR library screen that will “knock out” all human kinases to determine which ones are responsible for prostate cancer metastasis. CRISPR is a potent genetic editing tool and was used to silence all kinases in prostate cells (BPH …

A Clinico-Pathological Study Of The Structural And Functional Changes In The Retina And Optic Nerve Following Diabetic Retinopathy Treatments, Richard Filek

Electronic Thesis and Dissertation Repository

Diabetic retinopathy (DR) is the result of microvascular changes in the retina due to hyperglycemia which alter the blood-retinal barrier (BRB). The increased permeability of BRB results in the accumulation of extracellular fluid, the development of diabetic macular edema (DME) and capillary occlusion. Capillary occlusion results in retinal ischemia which increases vascular endothelial growth factor (VEGF) levels, increases vascular permeability and results in neovascularization in proliferative diabetic retinopathy (PDR) patients. The treatments clinically used for DR are panretinal photocoagulation (PRP) for PDR and injectable vascular endothelial growth factor inhibitors (anti-VEGFs) for DME.

The safety of PRP and anti-VEGF therapy on …

Immunological Impact Of Cli-095 On Dendritic Cell Maturation And Hypoxia-Re-Oxygenation Induced Inflammatory Injury, Hajed Obaid Alharbi

Electronic Thesis and Dissertation Repository

Immunological Impact of CLI-095 on Dendritic Cell Maturation and Hypoxia-re-oxygenation induced inflammatory injury

Introduction: Ischemia reperfusion injury (IRI) activates innate immunity through the engagement of Toll-Like Receptors (TLRs) by endogenous ligands. TLR4 expressed within the kidney is a potential mediator of innate activation and inflammation. Stimulation of TLR4 induces distinct patterns of gene expression, which not only leads to the activation of innate immunity but also to the development of acquired immunity. CLI-095, a novel synthetic small-molecule, suppresses production of multiple cytokines by inhibiting TLR4 signaling. In this study, we have determined the role of TLR4 in hypoxia and re-oxygenation …

Protective Benefits Of Hydrogen Sulfide Treatment During Renal Transplantation, Ian Lobb

Electronic Thesis and Dissertation Repository

Ischemia/reperfusion injury (IRI) is inherent to renal transplantation (RTx) and is initiated when blood supply is necessarily removed during organ procurement (ischemia) and subsequently restored upon engraftment (reperfusion). During renal ischemia, ATP depletion causes tubular epithelial cell (TEC) injury and subsequent release of pro-inflammatory mediators. Upon reperfusion, influx of O₂ causes reactive oxygen species (ROS) production and infiltration of innate immune cells which release damaging ROS and proteases. Prolonged periods of IRI are associated with increased risk of delayed graft function (DGF) and decreased long-term graft survival. The endogenously produced gasotransmitter, hydrogen sulfide (H₂S), has recently been …

Mechanisms Regulating Stem Cell Phenotype In Infantile Hemangioma, Niamh Richmond

Electronic Thesis and Dissertation Repository

Infantile hemangiomas (IHs) are benign vascular neoplasms characterized by the differentiation of multipotential stem cells (hemSCs) into endothelial cells during the early proliferative phase, and later into adipocytes during spontaneous involution. Transforming growth factor-β (TGFβ) has been shown to be significantly elevated upon IH involution and this coincides with repression of a developmentally-regulated transcription factor T-box 2 (TBX2). These findings implicate both TGFβ and TBX2 in mediating hemSC differentiation during IH evolution. The aim of my study is to understand the role of TGFβ and TBX2 in hemSC differentiation. I performed immunofluorescence staining to localize TBX2 protein in sectioned IH …

Polycomb Repressive Complex 2 Regulates Mir-200b In Retinal Endothelial Cells: Possible Implications In Diabetic Retinopathy, Michael A. Ruiz

Electronic Thesis and Dissertation Repository

Glucose-induced augmented vascular endothelial growth factor (VEGF) production is a key event in diabetic retinopathy. We have previously demonstrated that downregulation of miR-200b increases VEGF, mediating structural and functional changes in the retina in diabetes. However, mechanisms regulating miR-200b in diabetes are not known. Histone methyltransferase complex, Polycomb Repressive Complex 2 (PRC2), has been shown to repress miRNAs in neoplastic process. We hypothesized that, in diabetes, PRC2 represses miR-200b through its histone H3 lysine-27 trimethylation mark. We show that human retinal microvascular endothelial cells exposed to high levels of glucose regulate miR-200b repression through histone methylation, and that inhibition of …

Vascular Stem Cells In Diabetic Complications, Emily C. Keats

Electronic Thesis and Dissertation Repository

Diabetes leads to a variety of secondary complications. At the heart of these complications lies endothelial cells (ECs) – cells that take up unregulated plasma glucose, experience various biochemical alterations, and provide the basis for whole organ vascular dysfunctions. With the purpose of generating new vascular networks for the treatment of these chronic complications, my initial work focused on vascular stem cells (VSCs). VSCs have the ability to differentiate into both endothelial (EPC) and mesenchymal (MPC) progenitor cells, both of which are necessary for the creation of stable and functional blood vessels. To establish whether these progenitor populations retain their …

Immunohistochemical Studies Of Expression And Correlation Of Osteopontin, Cd44, And Integrin Αvβ3 In Selected Benign And Malignant Salivary Gland Tumours, Tommy Fok

Electronic Thesis and Dissertation Repository

Osteopontin (OPN) is a phosphorylated acidic glycoprotein that has been shown to play a vital role in tumourigenesis and metastases. The objective of this study was to determine the expression of OPN and its receptors (CD44 and integrin α_vβ₃) in several salivary gland cancers, and assess its clinical correlations.

Immunohistochemical techniques were used to semi-quantify the level of OPN expression and its receptors in normal salivary glands and different types of salivary gland tumour.

Our results show that in tumours of salivary gland origin, higher levels of OPN were detected in tumours which were malignant compared …

The Role Of Non-Canonical Wnt/Planar Cell Polarity Signalling In Breast Cancer Progression, Connor D. Macmillan

Electronic Thesis and Dissertation Repository

The role of planar cell polarity (PCP) signalling in breast cancer is unclear, as evidence shows that activation of this pathway with WNT5A can either promote or inhibit progression. Using the 21T cells, which represent distinct stages of breast cancer progression when grown in a mouse xenograft model (21PT, atypical ductal hyperplasia; 21NT ductal carcinoma in situ; 21MT-1, invasive mammary carcinoma), I hypothesized that WNT5A will promote progression only when VANGL1, another component of PCP signalling, is elevated.

Each 21T cell line showed distinct stage-specific morphologies when grown in a Matrigel “on-top” assay. WNT5A overexpression promoted progression to an invasive …