Medicine (St Vincent's) - Theses
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Addressing Controversies in the Management of Barrett’s Oesophagus Related Dysplasia
Endoscopic mucosal resection (EMR) and radiofrequency ablation (RFA) are safe and effective for management of Barrett’s oesophagus with dysplasia; however, some patients have a poor response to RFA, and recurrence of dysplasia can occur. There are controversies surrounding the management of Barrett’s oesophagus with low grade dysplasia (LGD) due to the conflicting data in the literature on diagnosis and progression rate. This thesis describes the long-term outcomes of endoscopic eradication therapy in management of dysplastic Barrett’s oesophagus and factors associated with poor response to RFA. In addition, this thesis also addresses the wide range of progression rate of LGD in the literature, investigates the use of specific histologic criteria to predict progression from LGD and describes a different phenotype of LGD in Barrett’s oesophagus.
Difficult to treat populations with hepatitis C infection: Prisoners, people who inject drugs, and viral resistance
It is estimated that 71 million people are living with hepatitis C virus (HCV) infection globally. The availability of all-oral direct acting antiviral (DAA) medications for HCV infection has revolutionised treatment which is now well tolerated, short in duration and highly effective and cure rates exceed 95% in clinical trials. In this context, the World Health Organization (WHO) has proposed targets for the elimination of HCV as a public health threat by 2030. This includes an 80% reduction in HCV incidence and 65% reduction in HCV-related mortality. Achieving these targets will require sustained effort in diagnosing and treating HCV infection, as well as the development and implementation of models of care to reach populations both highly affected by HCV infection or those underserved by current models. Mathematical modelling data has demonstrated that in high and middle-income countries, HCV incidence will be most rapidly reduced if treatment is prioritised for people who inject drugs (PWID) who contribute most greatly to HCV transmission. Prison populations globally are characterised by high HCV prevalence which is estimated to exceed 15%, and, in Australia, is as high as 50% amongst incarcerated PWIDs. PWIDs also experience high rates of incarceration on account of the criminalisation of injecting drug use (IDU). Despite this, HCV treatment rates within prisons have remained low due to multiple barriers to prison-based HCV care. As individuals re-enter the community from prison, they are also confronted by multiple competing priorities and linkage to HCV care was poor in the interferon era. How we can safely and effectively increase HCV treatment rates in the prison setting and beyond is not well defined. While most people living with HCV are cured following first-line DAA therapy, there are a subset who relapse. Those with advanced liver disease, including cirrhosis, are overrepresented in this group. It is therefore important to evaluate second-line salvage therapies in individuals with advanced disease to minimise HCV-mortality and mortality, in keeping with the WHO elimination goals. This thesis includes a number of clinical studies to address the above issues. In the first study, I evaluated the safety and efficacy of HCV treatment delivered to prisoners by the Statewide Hepatitis Program which operates in all Victorian prisons. I identified that nurse-led HCV care can reach prisoners in large numbers, that it was safe, and that cure rates exceeded 95%. Importantly, over 80% of those treated had never engaged in specialist HCV care prior to incarceration, highlighting that prison-based treatment can reach a population that is poorly served by existing healthcare models. Given that approximately 70% of prisoners reported recent IDU prior to incarceration, prison-based HCV care can also potentially reduce HCV incidence and prevalence within the community more broadly via interrupting transmission. In the second study, I investigated the likelihood of community DAA initiation amongst individuals released from prison with untreated HCV infection. I performed a randomised control trial evaluating a transitional intervention aimed at enhancing continuity of care following release. I identified that amongst unsupported individuals, DAA initiation rates were low. Our transitional model, however, was able to support a greater proportion of individuals to commence HCV treatment, whilst also significantly reducing the interval between community re-entry and DAA initiation, compared to those receiving standard of care. In the third study, I investigated the performance of non-invasive fibrosis algorithms amongst prisoners with HCV, including the AST-to-Platelet Index (APRI) and FIB-4 scores, to minimise the need for transient elastography and improve prison treatment efficiencies. I identified that these algorithms achieved high negative predictive values (NPV) at previously validated thresholds and, if incorporated into HCV assessment pathways, could minimise the need for further fibrosis determination. This is relevant for the dissemination of prison-based HCV programs domestically and internationally where access to transient elastography remains a barrier to care. In the fourth study, I investigated the prevalence of HCV NS5A resistance associated substitutions (RAS) at treatment baseline in DAA-naive participants with genotype (GT)1a, GT1b and GT3 infection. I demonstrated that the baseline NS5A RAS prevalence amongst Australians with GT1a infection was lower than other international regions, but comparable for GT1b and GT3 infection, and that next generation sequencing offered little improvement in diagnostic yield over population-based sequencing at baseline. These findings endorse Australia guidelines that HCV RAS testing is not required prior to first-line DAA therapy. In the fifth study, I evaluated the safety and efficacy of sofosbuvir, elbasvir, grazoprevir and ribavirin for relapsed HCV following treatment with an NS5A-inhibitor containing DAA regimen. I demonstrated that not only was this an effective salvage regimen for GT1 and 4, for which elbasvir and grazoprevir are licensed, but also for GT3 infection by using a multitargeted approach to suppress the emergence of resistant viral variants. In the sixth study, I evaluated the safety and efficacy of sofosbuvir, velpatasvir and voxilaprevir for relapsed HCV in Australians with advanced liver disease who were treated via a pharmaceutical early access program. Despite a high prevalence of difficult to cure characteristics including GT3 infection, cirrhosis, portal hypertension and liver transplantation (LT), I identified high SVR12 rates. While treatment was generally well tolerated, there were three episodes of hepatic decompensation and protease inhibitor usage should be carefully monitored in those with advanced disease. This study provides reassuring evidence that this regimen is highly effective for relapsed HCV, irrespective of baseline characteristics.
Virtual intracranial electroencephalography for epilepsy surgery: an ictal magnetoencephalographic study
Pharmaco-refractory focal epilepsy is a serious clinical problem. Epilepsy surgery is an effective approach to treat pharmaco-refractory focal epilepsy, particularly for complex cases with no clear lesion or an extensive lesion. However, surgical treatment is currently under-used and does not always render favourable outcomes. Invasive intracranial electroencephalography (iEEG) is the pre-surgical gold-standard to localise and circumscribe the epileptogenic zone (EZ). However, iEEG has several important limitations, such as constrained spatial sampling and invasiveness. More importantly, it is not always guaranteed that iEEG electrodes cover the entire EZ, which is believed to be one of the main reasons for unsuccessful surgeries. Non-invasive neuroimaging techniques mitigate the risks and limitations of iEEG by imaging brain structure and neural activity in a whole-brain fashion. Recent advances in electroencephalography (EEG), magnetoencephalography (MEG) and magnetic resonance imaging (MRI) combined with source imaging techniques allow to investigate neural dynamics at comparable temporal and spatial resolutions to iEEG but non-invasively. Solving forward and inverse problems are the two major missions of EEG and MEG source imaging. In this thesis, a study using realistic head model derived from individual MRI of a healthy subject and an epilepsy patient is conducted to understand the operating regime and limitations of constructing EEG and MEG forward models with compromise from brain lesion. Simulations using forward and inverse modelled ictal iEEG time-series and ictal MEG signals also offer crucial insights into reliably reconstructing ictal source signals that preserve important clinical characteristics, such as morphology and spatial patterns. Attempts have also been made to construct functional networks using ictal source signals reconstructed from MEG. There is a pressing need for non-invasive approaches that objectively characterise the EZ in presurgical evaluation. Dynamical network models using iEEG have demonstrated multiple successes in predicting the EZ and surgical outcomes. Combining non-invasive neuroimaging techniques with sophisticated dynamical network modelling approaches may offer valuable information to the current clinical localisation of the EZ such as iEEG. A novel approach, virtual iEEG (ViEEG), is proposed to non-invasively investigate ictal dynamics like iEEG without its limitations. The proof-of-concept study using 36 seizures captured MEG from 12 patients suggest dynamical network models applied to ictal ViEEG provide the valid characterisation of the EZ and non-ictogenic brain areas that are less likely to overlap the EZ. Moreover, solutions from ViEEG and dynamical network models using MEG alone predicts the iEEG seizure onset zone and the optimal source localisation solution that can only be offered using simultaneous EEG and MEG. The proposed approach and its findings demonstrate the feasibility of non-invasively and objectively characterising the EZ and motivate future work to optimise the current methods. The successful implementation of the proposed approach in the clinical setting would lead to significant benefit to people with refractory focal seizures: making surgery more available, minimising invasive recordings and therefore mitigation of risks, as well as improved surgical outcomes.
Responding to Urgency of Need - the Development of a Triage Tool for Palliative Care
Specialist palliative care services worldwide face the challenge of a workload that is growing in both volume and diversity. Simultaneously it is well recognised that timely access is crucial for the benefits of palliative care to be fully realized. When responding to a workload that at times may exceed resources, services must develop systems to prioritize patient care in a safe and fair manner. Significant efforts have been made to establish criteria defining which patients should receive specialist palliative care and at what point in the disease trajectory they should be referred, yet little is known about how patients should be prioritized once they have been referred. Unlike the field of emergency medicine and disaster response where systematic triage methods have been refined since World War I, limited attention has thus far been paid to how palliative care services should manage demand and consider urgency of response. A small number of studies have established that palliative care triage is a complex process embedded in organizational culture. Triage tools generated from these studies suffered from poor face validity and inter-rater reliability, and so have not been widely implemented into routine practice. This thesis therefore aimed to determine how the urgency of specialist palliative care needs should be assessed and compared between patients, with the practical outcome to ultimately develop an evidence-based, validated tool for palliative care triage – the Responding to Urgency of Need in Palliative Care (RUN-PC) Triage Tool. A series of studies were conducted, employing mixed methodologies to address various aspects of the research question and RUN-PC Triage Tool development. An initial qualitative study was undertaken to explore the attitudes and practices of palliative care providers towards triaging palliative care needs. This exploration led to a greater understanding of clinical decision-making that was used to develop a list of the key triage factors which formed the basis of the triage tool. These triage factors were then examined in the second study, a discrete choice experiment. This online international experiment determined the magnitude of effect that of each of the triage factors had on clinicians’ decision-making. These values became the scoring system for the RUN-PC Triage Tool. The third and final study was a validation study that demonstrated good intra- and inter-rater reliability and moderate to good correlation to expert opinion, which was used as the reference standard. This thesis paints a comprehensive picture of how palliative care clinicians approach the challenging task of triage and provides a practical tool to standardise the process that is evidence-based and validated. This research has significant implications for clinical practice internationally and represents an important step towards improving the transparency, consistency and efficiency of triage in palliative care, working towards equitable access for all.
Clinical, Immunological and Radiological Features of Endocrine Immune Related Adverse Events
Immune checkpoint blockade is a cancer treatment aimed at restoring and enhancing the ability of the immune system to combat a tumour. A recognised side effect is “collateral” immune damage to healthy tissue, or immune related adverse events (irAEs). Immune toxicity to endocrine glands can be rapid and irreversible and may result in the need for lifelong hormone replacement. A major challenge is identifying which patients will develop endocrine irAEs when treated with checkpoint inhibitors. The role of predictive biomarkers such as HLA type or autoantibodies has not been prospectively evaluated. The possibility of detecting pre-clinical endocrine dysfunction using MRI and PET imaging is described in small case series only. This project aims to 1. Define the clinical and immunological features of checkpoint inhibitor related diabetes, hypophysitis and thyroiditis in contrast to spontaneously occuring endocrine autoimminuty and 2. Explore ways to predict and detect endocrine toxicity early with biomarkers and imaging. First, I define the phenotype and immune mechanisms underlying checkpoint inhibitor related autoimmune diabetes. It was then relevant to discuss atypical or alternate phenotypes of diabetes and pancreatitis which have emerged over the past 2 years. This chapter concludes with a discussion of potential treatments aiming to reverse islet cell destruction, with a letter to the editor published in response to a case report. The next focus is the diagnostic evaluation of checkpoint inhibitor related hypophysitis. After hypothesising that the true incidence may be underappreciated, this chapter reviews the clinical, biochemical and radiological features in a cohort of patients monitored closely for this irAE. The third component of the thesis reviews the incidence and natural history of checkpoint inhibitor related thyroiditis. Defining the natural history provided important information guiding management of the hyperthyroid and hypothyroid phases respectively. This chapter includes a diagnostic accuracy study evaluating the role of FDG-PET/CT as a novel tool in the diagnosis of this irAE. In defining the natural history and diagnostic features of these three endocrine immune related adverse events, important recommendations about biochemical screening and the complementary role of routine cancer immaging are made. Importantly, treatment considerations relevant to oncologists and endocrinologists alike are outlined.
Multidisciplinary Care of Functional Gastrointestinal Disorders
Functional gastrointestinal disorders are highly prevalent. They constitute the most common presentation for gastroenterology specialist consultation and are among the most common conditions seen by general practitioners. These disorders include irritable bowel syndrome, functional dyspepsia and constipation. Their treatment is associated with substantial costs to the healthcare system, while other costs include impaired workforce productivity. Functional gastrointestinal disorders are typically characterised by an absence of “organic” pathology. Psychological and dietary factors are thought to play some part. Despite the efficacy of psychologically-based, behavioural and dietary therapies they are rarely incorporated into specialist care, and rarely form first line therapy. The typical model of specialist care involves a gastroenterologist working in isolation; the outcome of such a model of care has not been adequately evaluated. This thesis involves a collection of studies which evaluate the outcome of gastroenterologist-only care for functional gastrointestinal disorders, other models of care, and a multi-disciplinary model of care. I have demonstrated that symptom outcomes twelve months after care in a gastroenterologist-only clinic is poor. The majority of patients were dissatisfied with care, continued to have symptoms, and were often absent from work due to symptoms. This is the first study to have evaluated the outcomes of a gastroenterologist-only clinic. In a systematic review of the literature I have evaluated the models of care which have been evaluated for functional gastrointestinal disorders. This is the first published evaluation of models of care for functional gut disorders and suggested the benefit of allied clinicians incorporated into the care of functional gastrointestinal disorders. To evaluate if a multi-disciplinary model of care is superior to a gastroenterologist-only clinic model I critically reviewed the literature regarding trial design. I then designed a comprehensive, pragmatic, randomised trial that evaluated symptoms, quality of life, psychological wellbeing and cost. The MANTRA (multi-disciplinary treatment of functional gastrointestinal disorders) study is the first randomised study to evaluate the benefit of a multi-disciplinary model of care for functional gastrointestinal disorders. It demonstrated clinically-relevant, statistically significant, superiority of a multi-disciplinary clinic compared with a gastroenterologist-only standard care clinic, with regards to symptoms, quality of life, psychological wellbeing and cost. The studies in this thesis demonstrate that the current specialist-only model of care for these highly prevalent and costly conditions is inadequate. The thesis also provides a clear rationale and evidence base for a multi-disciplinary clinic model for the treatment of functional gastrointestinal disorders with respect to all important outcomes.
Inflammatory bowel disease and pregnancy: patient education, assessment of disease activity and monitoring of drug therapies
Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory condition of the gastrointestinal tract. The disease commonly impacts women during their reproductive years. IBD, particularly when active during pregnancy, is associated with worse maternofoetal outcomes. Pregnancy-related knowledge remains poor in many patients, with concerns regarding drug safety and a lack of understanding of the negative ramifications of active disease in pregnancy. Safe and effective monitoring of disease activity and drug therapies to control IBD throughout pregnancy are imperative. However, the utility and means of objective disease activity monitoring in pregnancy are unknown. The effect of pregnancy on the pharmacokinetics of immunosuppressant and biologic drugs in pregnancy remains undefined. This thesis presents a range of clinical research work as part of the prospective Pregnancy in Crohn’s and Colitis: Observations, Levels and Outcomes (PICCOLO) study. This study aimed to improve the pregnancy-related education and care of women with IBD; characterise the utility of objective disease activity monitoring including gastrointestinal ultrasonography in pregnancy; and examine the pharmacokinetics of thiopurine and biologic medications during pregnancy as well as infant outcomes following in utero medication exposure. I have explored the lived experience of IBD and pregnancy from the patient’s perspective using qualitative in-depth interviews. This research unearthed rich data relating to unique maternal fears and uncertainties around IBD medications and enduring a chronic illness throughout the pregnancy journey. I have demonstrated that a single individualised patient education intervention improves pregnancy-related knowledge among women with IBD. This novel intervention included a simple, accessible educational consultation for women with IBD who were pregnant or wishing to conceive. Pregnancy knowledge and quality of life scores were enhanced following the intervention and patient satisfaction levels were very high. This work has defined the role of gastrointestinal ultrasonography as a feasible and accurate modality for monitoring IBD in pregnancy. Adequate intestinal views were obtained in most patients to the end of the second trimester. Gastrointestinal ultrasound delivered a high specificity and sensitivity when compared with matched faecal calprotectin concentrations as an objective marker of disease activity. The research has contributed substantially to the understanding of the pharmacokinetics of thiopurines and biologic medications including infliximab, adalimumab and vedolizumab during pregnancy. Thiopurine metabolite concentrations were studied longitudinally in patients with IBD across pregnancy and in exposed neonates. Significant shunting of maternal thiopurine metabolites can occur during pregnancy. This work has established that complete clearance of thiopurine metabolites occurs in exposed infants by six weeks of age. Unlike a previous study, this work has shown that there is no association with neonatal anaemia following antenatal exposure to thiopurines. However, I identified the novel findings of thrombocytosis and abnormal liver function tests in exposed infants from six weeks of age, which gradually improved; possible mechanisms behind these infant haematological and biochemical findings are uncertain. Maternal drug levels of infliximab, adalimumab and vedolizumab in pregnancy were also prospectively assessed. This work has demonstrated that adalimumab levels remain stable and infliximab levels display a small increase in pregnancy. This study has described the first data regarding vedolizumab levels in pregnancy and clearance time in infants exposed to vedolizumab in utero. I have identified that maternal vedolizumab levels may show a small decrease in pregnancy, while infant vedolizumab cord blood levels are lower than maternal levels. All infants had undetectable vedolizumab levels by sixteen weeks of age. I have also presented preliminary data regarding another newer biologic agent, ustekinumab, including maternal levels in pregnancy and placental transfer. Infant cord blood levels of ustekinumab were found to be higher than maternal levels in the small cohort to date. This series of studies has the potential to change the paradigm of pregnancy-related education, objective disease activity monitoring and optimal use of IBD therapies for pregnant women with IBD globally.
Clinical, molecular and psychosocial profiling of long-term survivors of glioblastoma
Glioblastoma is the most common and most aggressive primary brain tumor in adults. It affects approximately 5.5 per 100,000 people in Australia, with incidence increasing by 3% per year. It is the sixth leading cause of cancer burden in Australia and is associated with significant morbidity from diagnosis. Prior to 2005, the mainstay of treatment was maximal surgical resection followed by radiotherapy with three- and five-year survival rates of 4.4% and 1.9% respectively. In 2005, the addition of concurrent oral temozolomide chemotherapy to standard radiotherapy demonstrated a modest improvement in overall survival with three- and five-year survival rates of 16% and 9.8% respectively. This established combined therapy as standard treatment for this condition (Stupp protocol) and highlighted the prospect of longer term survival as a small but distinct possibility. Long-term survivors of glioblastoma have been defined as patients alive 18 months to 5 years following diagnosis, without clear consensus on an appropriate definition. Approximately 13.7% of all patients diagnosed with glioblastoma survive longer than 2 years. With improved surgical and radiotherapy techniques, and the introduction of new therapies such as targeted therapy, the numbers in this group may continue to grow. Predicting who these patients are and understanding the nature and experience of their survivorship becomes paramount. The purpose of this thesis is to gain a comprehensive understanding of long-term survivors of glioblastoma, defined as patients diagnosed with glioblastoma who survive at least two years. Using a mixed methods approach, it combines elements of quantitative research, such as chart reviews, quality of life questionnaires and neurocognitive assessment, with qualitative research, such as semi-structured interviews. Together, this thesis addresses three major facets. Firstly, to be able to recognise at diagnosis patients that are likely to survive longer. Secondly, to develop a detailed understanding of the lived experience and patient reported concerns faced by long-term survivors of glioblastoma. Thirdly, to increase the proportion of long-term survivors through targeted clinical trials. Ultimately, this thesis provides insight into the care needs of patients, facilitates the planning of treatment and supportive care by clinicians, identifies options for improving access to clinical trials and recognises the support networks required for both patients and their caregivers to uphold their quality of life.
Determining how SRSF2 mutation leads to MDS and CMML and its genetic cooperativities in vivo and in vitro
Myelodysplastic syndromes (MDS) are a group of heterogeneous clonal stem cell malignancies characterised by multilineage cytopenia and dysplasia. MDS mostly occurs in aged populations where there are limited therapeutic options. Compared to MDS, chronic myelomonocytic leukaemia (CMML) presents with a monocytosis feature and has a poor survival of 16 months for high-risk patients. In the past decade, several sequencing studies have defined the complex molecular landscapes of MDS and CMML. SRSF2, a component of RNA splicing machinery, is one of the most frequent mutations in MDS and CMML. To understand the consequences and effects of SRSF2P95H mutation on normal haematopoiesis, several groups, including our lab, have generated in vivo mouse models using various gene targeting strategies and Cre recombinases. These models demonstrated some effects of SRSF2P95H mutation on haematopoiesis, and described certain mis-splicing changes in the Srsf2P95H/+ cells. However, the mechanism and role of SRSF2P95H mutation in promoting and initiating MDS/CMML are still poorly defined. My thesis aimed to address key knowledge gaps by examining the cell of origin, transcriptomic/splicing changes, synthetic lethal genetic interactions, and co-operative interactions of SRSF2P95H/+ mutation in the initiation of MDS/CMML. In the first part of my thesis, I assessed the cell of origin in SRSF2P95H MDS by characterizing a conditional knock-in Srsf2P95H/+ mouse model, using LysM-Cre. After activating Srsf2P95H/+ mutation in myeloid progenitors, I observed no development of MDS even after prolonged ageing (up to 52 weeks) and only mild changes in haematopoiesis. Compared to the stem cell activation model (hScl-CreERT2) that we reported, the results of LysM-Cre demonstrated that a myeloid progenitor is not the cell of origin in SRSF2mut MDS. In the second part of my thesis, I analyzed the transcriptomic and splicing changes of Srsf2P95H/+ cells, using both purified stem and progenitor cell populations as well as Hoxb8 immortalized cell lines. The transcriptome analysis revealed up- and down-regulation of lineage associated genes and up-regulation of MDS associated pathways and the p38 MAPK kinase pathway. The splicing analysis demonstrated skipped exons as the most frequent alternative splicing event. In terms of specific mis-splicing targets, I examined exon inclusion in several reported transcripts and compared the most frequently mis-spliced genes across 12 human SRSF2mut and murine Srsf2mut datasets. Through this analysis, I found that mRNA processing and DNA repair represent the top mis-spliced pathways in Srsf2P95H/+ cells. I also present a pilot study of single cell RNA sequencing of Srsf2P95H/+ stem and primitive progenitor populations, which unveiled a myeloid-biased signature and enhanced myeloid differentiation of the Srsf2P95H/+ stem cells. In the third part of my thesis, I explored the synthetic lethality of Srsf2P95H/+ cells with a pooled CRISPR knock-out screen. I discovered that loss of DNA repair or cell cycle pathways was synthetic lethal with Srsf2P95H/+ mutation. Consistent with this genetic lethality, I demonstrated that Palbociclib, a CDK6 inhibitor, could preferentially target the Srsf2P95H/+ cells. This finding opens up new therapeutic windows beyond known spliceosome inhibitors for SRSF2mut MDS. In the fourth and last part of my thesis, I generated and characterized two multi-genic mutation models: Srsf2P95H/+ Tet2-/- and Srsf2P95H/+ Cbl-/-. In the Srsf2P95H/+ Tet2-/- model, I observed profound myeloid bias, B lymphoid suppression and increased ST-HSC percentages in the stem cell compartment after 52 weeks of activating/deleting mutations in the haematopoietic stem cells. Within the Srsf2P95H/+ Tet2-/- cohort, I also observed development of CMML in both native haematopoiesis and transplantation settings. So far, this is the first model to demonstrate synergistic interactions between Srsf2P95H/+ and Tet2-/- mutation, as well as initiation of CMML in vivo. For the Srsf2P95H/+ Cbl-/- model, I characterized a small cohort of mice due to prolonged breeding difficulties. Nevertheless, I discovered increased myeloid proliferation in the double Srsf2P95H/+ Cbl-/- and Srsf2P95H/+ Cbl+/- mutants. Collectively, the work included in this thesis creates an original contribution to understanding the role of SRSF2P95H mutation in MDS, its synthetic lethal genetic interactions, potential therapeutic targeting of SRSF2P95H cells, and how it co-operates with other recurrent mutations in initiation of CMML.
Context for improving access to care for children and youth with diabetes in less-resourced countries
There are major deficits in knowledge related to the epidemiology and care of the various types of diabetes in young people in less-resourced countries. Multiple barriers exist at individual, community, health system, national, and international levels that must be overcome to lessen the gap in outcomes between advantaged and disadvantaged regions. This thesis presents 11 published papers by the candidate addressing this gap in knowledge. Type 1 diabetes (T1D) incidence data is presented for three countries with no previous data (Fiji, Bolivia and Azerbaijan), showing differing rates in each country, and in Fiji differing rates in the two main ethnic populations. Novel information on the types of diabetes is presented for Azerbaijan (along with the incidence data aforementioned), Pakistan and Bangladesh. Results in Azerbaijan were similar to those seen in European populations. In Pakistan and Bangladesh, it is common to see atypical forms that clinically present like T1D cases but do not have low C-peptide values or diabetes autoantibodies. Five papers examine costs and access to care. In a survey of 71 countries, availability of nearly all key components of care was greatly reduced in lower-income countries. A study of costs to families in 15 countries demonstrated that the cost of core supplies is prohibitively expensive for many families. A comprehensive review of issues surrounding access to supplies for self-monitoring of blood glucose presents new information on the global market and makes numerous practical recommendations. Progress towards Universal Health Coverage for provision of insulin and blood glucose test strips was evaluated in 44 countries, showing that there was greater progress for insulin than for test strips. A novel framework for describing T1D care levels (Basic, Intermediate and Comprehensive) provides a way of identifying the steps required to improve care in a particular situation, and the data presented from Bolivia shows that Intermediate Care can achieve outcomes similar to those in some highly-resourced countries. The final paper, using robust, novel and replicable methodology, demonstrates the efficacy of traditional evaporative cooling devices used for insulin storage where refrigerators are not available. In conclusion, efforts to improve care for young people with diabetes in less-resourced countries must take into account wide differences in incidence and the types of diabetes that occur between countries. Furthermore, for care to improve, many components of care need to be addressed. The concept of ‘Intermediate Care’ provides an achievable level of care that can result in reasonable outcomes even in poorly resourced health systems.
Detection and monitoring of diabetic polyneuropathy with specialised markers of small and large nerve fibres
Routine nerve conduction studies (NCS) are the current standard test for the evaluation of suspected peripheral neuropathy, but are often normal in patients with diabetic polyneuropathy (DPN). This is because: i. NCS are unable to detect dysfunction of small fibres, which may be affected earlier and are the cause of painful neuropathic symptoms; and ii. Significant large fibre axonal loss +/- demyelination may need to occur before NCS detect this is an abnormality. This research project critically evaluates various newer/novel methods to detect and potentially monitor diabetic neuropathy, and to provide a feasible way that this can be routinely assessed in the neurophysiology laboratory. I chose to specifically analyse the diabetic population as this is by far the most common cause of peripheral neuropathy in the global community, causing significant burden of disease. The various known novel techniques to assess and monitor DPN are evaluated, firstly through that which is available in current literature. These are compared in terms of diagnostic accuracy, as well as availability and cost-effectiveness. Based on the findings from this literature review, various prospective clinical studies are developed to further evaluate the more promising techniques identified. A focus was made towards techniques that can be performed in the neurophysiology laboratory, as routine NCS have, and will remain likely to have a significant role in the assessment of diabetes-related neuropathy. Thus, this clinical visit provides an opportune time to perform these additional tests as a way of providing supplementary information on patient’s peripheral nerve status. Small and large nerve fibres are both affected by diabetes. However, these fibres display very different physiological properties, not just in terms of structure and function, but they are also evaluated by completely different techniques. Small fibres can then be further subdivided into different populations of thinly myelinated A-delta fibres and unmyelinated C-fibres, which again have very different properties and assessment modalities. This thesis is divided into two main sections with research focussed on providing more accurate measurement of the various small fibre populations in the first section, and then improving large fibre testing beyond that of routine NCS in the second section.
Determining the impact of Recql4 mutations on normal homeostasis, tumour development, and functional genetic interactions
Since mutations in the RECQL4 gene were identified as causative of Rothmund-Thomson syndrome (RTS) more than twenty years ago, some inroads have been made in the understanding of this disease and its mutations. It has been discovered that the majority of these mutations are nonsense and frameshift mutations resulting in truncating protein products that delete both the helicase and the C-terminal domain. The deletion of these domains results in a dysfunctional RECQL4 protein and the development of the variable clinical spectrum and the increased predisposition to malignancies, typical of RTS. Several Recql4-mutated mice have been generated as a model for RTS. Although these models have contributed to identify some of the functions of RECQL4, they do not accurately reflect the genetic status of RTS, in which patients generally present with hypomorphic, rather than null alleles. On the other hand, these models have not provided sufficient insight into the specific functions and domains of RECQL4; and the effects of RECQL4 mutations on normal homeostasis, tumour development, and functional genetic interactions. This thesis, through its three related components, aims to address all these gaps by using murine models bearing mutations that inactivate specific functions and domains of RECQL4, and that resemble common mutations seen in humans. In the first component of this thesis, I generated mice carrying an ATP-binding knock-in mutation to assess the physiological requirements and biological functions of the helicase activity, thought to be critical for the overall functions of RECQL4. Through a variety of experiments, I observed that homozygous mice were normal in terms of embryonic development, body weight, haematopoiesis, B and T cell development, and physiological DNA damage repair. Furthermore, to compare the in vivo effects of a helicase-inactive versus truncating mutations, I used conditional deletion models and found that only mice carrying truncating mutations developed bone marrow failure. These findings demonstrated that the ATP-dependent helicase activity of RECQL4 is not essential for its physiological functions, and that truncating mutations are deleterious. For the second component of this thesis, I assessed mice carrying germline truncating RECQL4 mutations to understand the impact of the deletion of the helicase and C-terminal domains on normal homeostasis and tumour development. I found that truncating mutations affected stability and subcellular localisation of RECQL4, which translated to a homozygous embryonic lethality and a haploinsufficient low bone mass phenotype through defects in early osteoblast progenitors. Additionally, I observed that the severity of the defect was related to the degree of the truncation, suggesting that gene dosage is an important determinant of the bone phenotype. However, these mutations were not sufficient to initiate tumorigenesis in mice, even after exposure to irradiation, which pointed to the possibility that mutations in other genes, besides Recql4, might be contributing to this disease. In the third and final component of this thesis, I performed a genome-wide genetic rescue screen to identify genetic interactions with mutant Recql4, an area largely unexplored. Amongst the genes identified, the standout candidate was Klhdc3. In subsequent validation assays, I demonstrated that mutation of Klhdc3 rescued the phenotypes associated with a pathogenic RECQL4 mutation, which is to my knowledge, the first confirmed genetic interaction associated with an improvement of the cellular phenotypes caused by RECQL4 mutations. Collectively, the work presented in this thesis makes an original contribution to knowledge through the finding that the ATP-dependent helicase activity of RECQL4 is dispensable for its physiological functions, the discovery that truncating mutations cause a haploinsufficient low bone mass phenotype and that gene dosage is an unsuspected regulator of bone mass, and the identification of Klhdc3 mutation as being capable of rescuing the proliferation defect caused by a truncating RECQL4 mutation.