Obstetrics and Gynaecology - Theses
Permanent URI for this collection
Search Results
1 - 10 of 45
-
ItemIn mechanically ventilated extremely preterm infants, does extubation to a higher CPAP level, compared to a standard pressure, decrease the risk of extubation failure?( 2023-11)Background Extremely preterm infants, those born < 28 weeks gestation, are at increased risk of morbidity and mortality compared with infants born at term gestation. Respiratory distress is common at this gestational age, and many infants require intubation and mechanical ventilation. Due to the complications associated with invasive ventilation, clinicians aim to extubate these infants to non-invasive support as early as possible. However, 40-60% of these infants experience extubation failure. Extubation failure is associated with morbidities such as acute physiological instability, trauma to the tissues of the airway, bronchopulmonary dysplasia, pulmonary vascular disease, and death. Nasal continuous positive airway pressures (nCPAP) > 5 cm H2O reduces extubation failure, but there is no consensus on the optimal pressures. Optimisation of nCPAP by using higher pressures may reduce extubation failure. However, there is a paucity of data examining the efficacy of pressures greater than or equal to 9 cm H2O. Aim To evaluate whether the use of higher nCPAP levels of 9-11 cm H2O compared with standard pressures of 6-8 cm H2O reduces extubation failure in extremely preterm infants. Methods After reviewing the existing evidence, I conducted the following research: 1. An audit of extubation failure in extremely preterm infants across two tertiary neonatal intensive care units. I examined records of extremely preterm infants < 28 weeks’ gestation to determine the characteristics of infants who experienced extubation failure and predictors of extubation failure. 2. A systematic review and meta-analysis of current non-invasive respiratory supports used post-extubation in extremely preterm infants. 3. A clinical randomised controlled trial, in which preterm infants < 28 weeks’ gestation, admitted to a neonatal intensive care unit after birth, and undergoing their first extubation were allocated to receive either higher nCPAP (9-11 cm H2O) or standard nCPAP (6-8 cm H2O). The primary outcome was extubation failure within 7 days as per the trial extubation criteria. Results 1. On multivariable analysis, lower gestational age (OR 0.71 [95% CI 0.6-0.9], P<0.001) and higher pre-extubation mean airway pressure (OR 1.9 [95% CI 1.4-2.5], P<0.001) were predictive of extubation failure. 2. Overall quality evidence in this population (< 28 weeks’ gestation) is lacking. In extremely preterm infants, there is no difference between nCPAP and non-invasive positive pressure ventilation (NIPPV) in reducing extubation failure. When synchronised with the infant’s breathing and ventilator-derived using higher peak inspiratory pressures, NIPPV may be superior to nCPAP in preventing extubation failure. Nasal heated humidified high flow is inferior to nCPAP in preventing extubation failure. Finally, higher nCPAP levels (greater than or equal to 9 cm H2O) may reduce extubation failure. 3. The Extubation CPAP level assessment trial (ECLAT) recruited 138 infants with a mean gestation of 25.7 weeks and a mean birthweight of 777 grams. Extubation to a higher nCPAP reduced extubation failure compared with extubation to standard nCPAP: 35% vs. 57%, risk difference (95% confidence interval) -0.22 (-0.37, -0.04). There were no important differences in rates of secondary outcomes or adverse events between groups. Conclusions Currently, nCPAP, NIPPV (including biphasic positive airway pressure and neurally adjusted ventilatory assist), high flow and nasal high-frequency oscillation ventilation are non-invasive modes of respiratory support used post-extubation in extremely preterm infants. Despite this, extubation failure rates remain high. Gestational age at birth and pre-extubation mean airway pressure are helpful in predicting infants at risk of extubation failure. The use of higher pressures (greater than or equal to 9 cm H2O) reduced rates of extubation failure in extremely preterm infants managed with nCPAP.
-
ItemIdentification of novel biomarkers in human cervicovaginal fluid to predict labour(University of Melbourne, 2009)
-
ItemDefining abnormal fetal size in pregnancy to help identify infants at risk of size related complications( 2023-03)A key component of antenatal care centres on ensuring that fetal size is appropriate for gestational age. Most attention is focused on detecting small infants because they are known to be at increased risk of perinatal mortality and many short and long-term complications. This is because small fetal size often reflects a pregnancy affected by placental insufficiency- resulting in pathological growth- or true fetal growth restriction. Despite the fact that all international guidelines agree on the need to detect and monitor small fetuses, the decision about which obstetric growth standard best identifies the fetus at increased risk of adverse outcome remains a subject of fierce debate. There are many different published obstetric growth standards. Even within Australia, many institutions and states use different growth charts. The centile thresholds applied can thus be quite discrepant. This means that the chart used can have a significant impact on detection of the small (‘at-risk’) fetus and subsequent management decisions regarding surveillance and timing of birth. Therefore, the first aim of this thesis was to clarify which growth standards perform best in identifying the fetus at risk in an Australian obstetric population. To answer this question, we used a variety of epidemiological methods to examine the association of fetal size with adverse perinatal outcomes. We sourced large datasets in order to use rare primary endpoints of high clinical significance, such as stillbirth. The first dataset available included all women that delivered at a single tertiary centre (Mercy Hospital for Women) from 1994 to 2016 (101,309 births). The second dataset included all births within Victoria from 2005 – 2015 (735,591 births), obtained from the Consultative Council on Obstetric and Paediatric Mortality and Morbidity (CCOPMM). The third dataset, available in the latter part of the candidature, also from CCOPMM, included all births within Victoria from 2009 – 2019 (853,191 births). At each point throughout this thesis, the largest and most contemporary dataset available was used to answer our research questions. The size of our datasets enabled us to assess rare perinatal outcomes known to be associated with placental insufficiency, including stillbirth and major neonatal morbidity, as well as assess rare outcomes associated with large infants, such as shoulder dystocia. Our first project compared the classification of infants as <10th centile by the recently published INTERGROWTH-21st birthweight charts or by customised growth centiles. INTERGROWTH-21st growth charts were derived from a prospective international cohort of healthy mothers and infants. Such charts are considered ‘prescriptive’, capturing fetal growth and birthweight under optimal conditions. Customised fetal growth centiles were adjusted for fetal and maternal characteristics known to impact birthweight. INTERGROWTH-21st charts classified only 4.6% of infants below their 10th centile cutoff, compared with 10.6% by customised charts. This means that many fetuses currently considered high risk would be reclassified as healthy, using INTERGROWTH-21st charts. Therefore, we considered that INTERGROWTH-21st charts were not suitable for immediate adoption into Australian clinical practice. Our second project examined which growth standards were best to detect small fetuses at risk of perinatal morbidity and mortality in a preterm population. The impact that fetal size assessment has on informing surveillance and management decisions is particularly significant in the preterm period. We found that a growth standard derived from the estimated fetal weight of an in-utero population (a ‘fetal’ chart), had the best ability to identify fetuses at-risk in a preterm setting. This is because it identifies fetuses who are small compared with healthy fetuses in ongoing pregnancies, rather than fetuses that have been born prematurely for pathological conditions that may have adversely impacted fetal growth. Next, we compared sex-specific growth standards with those unadjusted for fetal sex, given male infants are known to be larger on average. We found that classifying infants as small by sex-specific standards better correlated with perinatal outcomes, indicating true fetal growth restriction. We then examined the impact of a growth standard that provided a single set of centiles for each gestational week, with one for each gestational day. We found that using a gestational day-specific growth chart was beneficial, as a week-based chart artificially distorted the centile classifications (and hence risk categorisation) for infants born at the beginning or end of a week. We then examined the impact of maternal size on the classification of infant size. Maternal obesity can affect fetal size, and we investigated whether infants experienced growth restriction, or failed to meet their growth potential, at a correspondingly higher birthweight centile in the setting of maternal obesity. We identified that the same stillbirth risk seen in <10th centile infants born from healthy weight mothers exists at a higher birthweight centile among infants born to mothers with higher body mass index. Finally, we examined the optimal assessment of fetal size among large for gestational age infants (>90th birthweight centile). Pathological overgrowth is more likely to be associated with intrapartum complications such as emergency caesarean section, so we investigated whether adjusting fetal centile according to maternal height alone, or height and weight, improved the prediction of emergency caesarean section. We found that adjusting for maternal height, but not both maternal height and weight, improved the prediction of emergency caesarean section risk. The findings of this thesis have helped clarify which aspects of growth charts may best identify the small, or large, infants at greatest risk of experiencing growth-related complications. These findings provide important guidance for future adoption, or creation, of improved obstetric growth standards to better identify fetuses at increased risk of adverse outcome, and will provide greater clarity for clinicians around the use of currently available charts.
-
ItemLife after the lab - the short-medium- and long-term outcomes after in vitro fertilisation (IVF) in Victoria( 2022-12)BACKGROUND In-vitro fertilisation (IVF) is an artificial mode of conception. Currently, IVF accounts for approximately 5% of births in Australia and has resulted in more than 8 million births world-wide. From an epidemiology perspective, IVF, like many other perinatal events, is a significant perinatal exposure which may have important long-term sequalae. AIMS This thesis aims to examine specific short-, medium- and long-term outcomes for children conceived by IVF. In doing so, this project was intended to contribute to the growing body of literature looking at outcomes among these children and help fill an existing knowledge gap. RESEARCH QUESTIONS To achieve the project aim, two research questions with were explored. First (project 1), what is the association between IVF using donor gametes and specific adverse outcomes of pregnancy, including hypertensive disorders and fetal growth restriction? Second (project 2), what is the estimated causal effect of IVF conception on school-age developmental and educational outcomes for children, compared with unassisted conception? This second question represents the major project of this thesis. METHODS These research questions were explored separately using contrasting methodologies. In project 1, a retrospective observational study was undertaken to examine the association between IVF using different categories of donated gametes (donated sperm, oocyte, or embryo) and 1) hypertensive disorders of pregnancy and 2) fetal growth restriction (FGR)), compared with IVF-conceived pregnancies using autologous gametes (own egg and partner sperm). The second and major project of this thesis was a state-wide, population-based record linkage study aimed at examining the school-age educational and developmental outcomes for children after IVF conception. IVF cycle data was obtained from the three major IVF providers in Victoria from 2005-2014 to identify a cohort of children conceived via IVF. This dataset was then combined by administrative data linkage with four other separate databases. These datasets, included the 1) Victorian Perinatal Data Collection – to enable identification of spontaneously conceived controls from the same time period and to add birth outcome data for the population, 2) The Australian Early Development Census (AEDC) – a global assessment of childhood development at school entry, 3) the National Assessment Program for Literacy and Numeracy (NAPLAN) – the universal Australian psychometric testing metric, and 4) the birth deaths and marriages registry – which was required to link maternal and child data. Project 2 was approached under the framework of causal inference. This approach stipulates that throughout the study design process, data collection, analysis and interpretation, researchers attempt to curtail bias arising from observational data such that under a set of assumptions, causal effects can be estimated. These methods have been developed since the 1970s but are not commonly used in health research. The application of these methods to the research question of interest in project 2 is a significant focus of this thesis. RESULTS Our findings from project 1 suggest a 2.3-fold increased risk of hypertensive disorders of pregnancy, after adjustments with multivariate regression, in pregnancies conceived via donated oocytes. Sperm donation did not appear to be associated with an increased risk (adjusted odds ratio: 0.94, 95% confidence interval: 0.73 to 1.21). The results from project 2 suggest that there is no causal effect of IVF conception on the risk of being developmentally vulnerable at school entry, as assessed by the AEDC outcome metric (average treatment effect (ATE) risk ratio: 0.97, 95% CI 0.77 to 1.25). Similarly, the findings suggest no causal effect of IVF conception on educational outcomes at age 7-9, with similar overall NAPLAN z-score seen in both IVF conceived children and controls (ATE mean difference: 0.003, 95% CI -0.018 to 0.077). The causal model included adjustment of important covariates including maternal age, education, socioeconomics and parity. DISCUSSION The findings of project 1 confirm that pregnancies with a history of egg donation should be managed as high risk. Previous evidence has suggested that “primi-paternity” (the first pregnancy conceived with a specific partner) increases the risk of hypertensive disorders of pregnancy. Our findings suggest that the concept of primi-paternity is only valid during natural conception. IVF is known to be associated with an increased risk of hypertensive disorders of pregnancy – and our findings did not suggest additional risk using donated sperm. As such, we propose that the products within seminal fluid may contribute to development of maternal immunotolerance and that IVF may subvert this natural process of immunotolerance. The findings in this project provide important reassurance for current and future families of IVF-conceived children. Additionally, this thesis demonstrates that via creation of a population-wide, covariate rich dataset and with considered application of these methods, causal effect can be estimated from observational data to determine the school-age educational and developmental outcomes for children after IVF-assisted conception compared to their peers.
-
ItemMaternal morbidity, maternal mortality, and stillbirth in the Asia-Pacific region( 2023-01)The Asia-Pacific region hosts many low-middle-income countries with significant barriers to achieving health equity. The Solomon Islands is a Pacific nation with high levels of preventable maternal mortality, morbidity and stillbirth. This thesis investigated rates and causes of maternal morbidity in the region; maternal mortality, maternal morbidity and stillbirth in the Solomon Islands; and the role of betel nut on adverse pregnancy outcomes and hypertensive disorders in pregnancy. These findings can guide future research and health policy in the region.
-
ItemAgeing of the placenta: potential prognostics, diagnostics and therapeutics( 2022)Abstract Ageing effects on human organs are most notable in the elderly. However, the placenta is exceptional because it shows signs of ageing in a short time span. Healthy ageing of the placenta is the process of developing and maintaining the functional ability of the placenta until term and is a feature of uncomplicated pregnancies. However, recent studies show unhealthy ageing of the placenta is a common feature of important human pregnancy disorders. Unhealthy premature ageing of the placenta is associated with pregnancy complications of preeclampsia (PE) and fetal growth restriction (FGR), whereas unhealthy placental ageing at term is associated with stillbirth. Given the emerging importance of placental ageing, the general aim of the work was to investigate potential prognostics, diagnostics and therapeutics for ageing of the placenta. Regarding prognostics and diagnostics, the sFlt-1/PlGF ratio test used to predict the risk of PE was investigated in a retrospective clinical study. The sFlt-1/PlGF ratio increased with the healthy ageing of the placenta at term. In addition, the total extracellular vesicle population isolated from the maternal peripheral blood during second trimester increased in pregnancies with a late onset PE outcome compared to a gestation matched normotensive control outcome and showed an association with the sFlt-1 concentration. These results suggest that the sFlt-1/PlGF ratio and EV population size are potential prognostic or diagnostic markers for unhealthy placental ageing-associated pathologies such as PE and stillbirth. A hallmark of ageing is damage to stem cells, which prevents them from replenishing cells in ageing organs and tissues. Pharmaceutical drugs and extracellular vesicles (EV) with anti-ageing properties secreted by healthy ageing early term decidual mesenchymal stem cells (ET-DMSC) were used to treat unhealthy premature-ageing PE-DMSC and ageing late term DMSC (LT-DMSC). As well, a microRNA present in high levels in ET-DMSC (miR-516b-5p) was also analysed. Drugs with anti-ageing properties and EV from ET-DMSC delayed the ageing phenotype of both PE-DMSC and LT-DMSC. In addition, miR-516b-5p affected stem cell survival. ET-DMSC with elevated levels of miR-516b-5p had better survivability. Finally, as described above, the total EV population size in maternal blood is a potential prognostic or diagnostic marker for unhealthy placental ageing-associated pathologies. However, many cell types, including stem cells, secrete EV into maternal blood. The final aim was to determine whether EV secreted from DMSC into maternal blood could be enriched from maternal blood. In order to achieve this, unique DMSC-EV cell surface markers need to be identified. When compared with chorionic mesenchymal stem cell derived EV (CMSC-EV), mass spectrometry analyses showed DMSC-EV and CMSC-EV have unique combinations of lipids and proteins on their surface, which could potentially facilitate the isolation of DMSC-EV and CMSC-EV from maternal blood. In addition, studies in the literature showed that changes in the levels of candidate lipids and proteins are associated with healthy ageing and in some cases with unhealthy placental ageing-associates pathologies such as PE and FGR, where the placenta shows signs of premature ageing.
-
ItemThe role of metzincins and TIMPs in ovarian cancer( 2022)Epithelial ovarian cancer has the highest fatality-to-case ratio of all the gynaecological malignancies. In Australia, only 46% of patients survive 5 years after diagnosis of epithelial ovarian cancer. The metzincin family of metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in matrix remodelling, regulation of signal-transduction pathways, angiogenesis and a range of diseases including cancers. This thesis investigated the role of metzincins and TIMPs in ovarian cancer providing insights in progression, chemoresistance and recurrence in patients. It revealed that TIMP-2, specifically, plays a role in serous epithelial ovarian cancer progression and regulates chemosensitivity of ovarian cancer cells through pathways that regulate cancer stem cell (CSC) phenotypes. In chapters 3 and 4, the expression patterns of metzincins and TIMPs were assessed in (a) FIGO stages, Silverberg grades and WHO types of primary serous ovarian carcinomas; and (b) ascites-derived tumour cells collected from chemo-naive and chemotherapy-treated recurrent patients and fluids. The expression of TIMP-2 and TIMP-3 was significantly upregulated in high-grade serous ovarian tumours compared to benign tumours. Moreover, TIMP-2 mRNA was regulated in the chemotherapy-treated, ascites-derived epithelial tumours compared to chemo-naive samples. TIMPs and MMPs were differentially expressed in fourteen ovarian cancer cell lines. Chemotherapy treatments (cisplatin or paclitaxel) modulated TIMPs and MMPs expression in association with increased expression of genes related to chemoresistance. Overall, the findings indicated that TIMP-2 was a likely candidate to be involved with ovarian tumour progression and chemoresistance. In chapter 5, TIMP-2 gene expression was transiently knocked-down by siRNA (T2-KD) in three high grade serous ovarian cancer cell lines (JHOS-2, OVCAR4 and OVCAR5) and a control cell line derived from normal oviductal epithelium (FT282). Overall, TIMP-2 downregulation significantly downregulated the expression and activation of MMP-2, but enhanced: proliferation, invasion, MMP-14 expression, induced EMT and increased sensitivity to cisplatin and paclitaxel. Chemotherapy treatments significantly enhanced the expression of TIMP-2, MMP-2, MMP-14, chemoresistant and CSC genes and induced activation of STAT3 in control cells, but remained unchanged in T2-KD cells. These results demonstrate that TIMP-2 plays a role in ovarian cancer progression and regulates chemosensitivity of ovarian cancer cells through pathways that regulate CSC phenotype. In chapter 6, TIMP-2 was edited in OVCAR5 cell line using CRISPR/Cas9 using two different guide RNAs. This resulted in two clonal cell lines, with gRNA2 (63% TIMP-2 knock-down) cells having similar characteristics as siRNA T2-KD cells. However, the functional outcome from gRNA1 (80% knock-down) was partially different. This cell line had similar MMP-2 and MMP-14 profile as gRNA2 but was resistant to paclitaxel. In addition, gRNA1 cells produced greater tumour burden than control cells in mice and a significantly shorter survival response compared to gRNA2 cells which produced small tumour burden and significantly longer survival. Collectively, these results demonstrate a complex role of TIMP-2 in ovarian cancer progression and chemoresistance. It is not only the reduction of TIMP-2 expression but the degree of reduction that influences the physiological/biological end points. Findings in this thesis have furthered understanding of TIMP-2 in ovarian tumorigenesis and laid the foundation for TIMP-2 mediated targeted therapy.
-
ItemHuman amnion epithelial cells and bronchopulmonary dysplasia in preterm infants( 2021)Bronchopulmonary dysplasia (BPD) is a frequent and important morbidity for extremely preterm infants. The lung injury that gives rise to BPD occurs during the late canalicular and early saccular phases of lung maturation and is induced by various agents including hyperoxia, ventilation associated injury and infection. The result is arrest of alveolar development. Consequently, infants with BPD are more likely to have poorer respiratory health, not just in infancy, but through their lifetime. Sufferers of BPD are at greater risk of neurodevelopment challenges such as cerebral palsy and cognitive impairment. Treating, or better still, preventing this multifactorial disease is challenging. Cell therapy, with its capacity to modulate the inflammatory response, support angiogenesis and protect endogenous progenitor cells, is a unique and promising therapy for BPD. Human amnion epithelial cells (hAECs) are a type of cell therapy derived from the amniotic membrane of term placentae. The mechanisms of hAEC action and evidence of their therapeutic potential in BPD-like injury are evaluated here. Following this examination of the pre-clinical evidence, this thesis outlines the development and implementation of a phase 1 dose escalation study of hAECs in infants at significant risk of developing BPD. This work builds on an earlier, first in human study, of a modest dose of hAECs in infants with established severe BPD. The tolerability of larger doses of hAECs given to less mature infants in our study called ‘RENEWAL; Reducing Neonatal Lung Disease With Amnion Cells’ is reported. In an important and novel contribution to the field of neonatal cell therapy we have highlighted and resolved deficiencies in bedside cell therapy infusion protocols. Established infusion protocols were discovered to delivered less than 20% of the intended dose of hAECs during the early phases of the RENEWAL study. We solved this challenge with simple measures using equipment that was readily available in the neonatal unit. Finally, the strengths and limitations of the RENEWAL study are examined, and future directions for neonatal cell therapy are discussed. The RENEWAL study represents an important milestone in neonatal cell therapy. The RENEWAL study has detected and resolved important knowledge gaps. With its completion anticipated in the next 18 months, the RENEWAL study will add significantly to the body of evidence for the safety of cell therapy in extremely preterm infants. Importantly, the tolerable dose of hAECs in extremely preterm infants reported here provides a foundation on which to build the next series of cell therapy trials.
-
ItemNasal high flow therapy in neonates: new evidence and a novel application( 2021)Background Newborn infants may require respiratory support in the first days of life. Preterm infants receiving respiratory support are susceptible to a chronic lung disease called bronchopulmonary dysplasia (BPD). Non-invasive respiratory support reduces rates of BPD, compared with ventilatory support via an endotracheal tube. Continuous positive airway pressure (CPAP) is the most common form of non-invasive respiratory support in neonates. Nasal high flow therapy (nHF) is a novel alternative to CPAP. It comprises two small, tapered nasal prongs through which heated, humidified, blended air and oxygen are delivered at high flow rates. There are currently two common indications for nHF in neonates: primary respiratory support soon after birth for the prophylaxis or treatment of respiratory distress syndrome, and post-extubation support following a period of mechanical ventilation. The evidence for the use of nHF is evolving, and systematic evaluation of this evidence is important. There may be novel applications of nHF. In older children and adults, nHF is used during endotracheal intubation (the placement of a breathing tube in the trachea to support breathing with a mechanical ventilator). Neonatal endotracheal intubation is a procedure that is technically difficult and is occurring less frequently over time; hence success rates on the first attempt are low. In addition, oxygen desaturation during endotracheal intubation is common. Interventions to improve the likelihood of first attempt intubation success, as well as infant stability during the procedure are therefore needed. Based on adult and paediatric data, nHF use during endotracheal intubation may prolong the time to desaturation. There have previously been no studies of the use of nHF during neonatal intubation. Aims This thesis aims (i) to synthesise existing evidence for nHF use in neonates and (ii) to evaluate the innovative application of nHF during neonatal endotracheal intubation. Methods For this thesis, I summarised the literature on invasive and non-invasive neonatal respiratory support, focusing on preterm infants. I also summarised the difficulties associated with neonatal endotracheal intubation. I then undertook the following original research: 1. A Cochrane systematic review and meta-analysis of the use of nHF for primary respiratory support in preterm infants, compared with other non-invasive respiratory support modalities; and 2. A multicentre, randomised controlled trial of nHF during oral neonatal endotracheal intubation, in which neonates undergoing intubation were randomly allocated to either nHF during the first intubation attempt, or to standard care. Results of original research 1. When compared with CPAP, the use of nHF for primary respiratory support in preterm infants (<37 weeks’ gestation) was associated with no difference in the outcomes of death, BPD or the combined outcome of death or BPD. The rate of treatment failure at 72 hours after trial entry was higher in infants managed with nHF, compared with CPAP. However, there was no difference in the rate of mechanical ventilation between groups. When compared with non-invasive positive pressure ventilation (CPAP with superimposed pressure rises to a set peak pressure), the use of nHF was associated with no difference in the outcomes of death, BPD, the combined outcome of death or BPD, treatment failure, or mechanical ventilation. 2. The use of nHF during neonatal endotracheal intubation increased the likelihood of successful intubation on the first attempt without physiological instability. Infants managed with nHF were more likely to be intubated successfully on the first attempt, and fewer infants desaturated during the procedure. Whilst there was no evidence of a difference in effect in the prespecified subgroups of postmenstrual age and use of premedication, the beneficial effect of nHF during intubation was greater when intubation was performed by inexperienced operators. Nasal HF was quick to apply and there was no difference in serious adverse events between groups. Conclusions These findings suggest that the use of nHF for primary respiratory support in preterm infants may result in little to no difference in the clinically important outcomes of death or BPD, compared with CPAP or NIPPV. Nasal HF is associated with a higher rate of treatment failure than CPAP. However, provided surfactant and/or CPAP are available in the event of nHF treatment failure, there is no difference in the rate of mechanical ventilation. The use of nHF during neonatal endotracheal intubation increases the likelihood of successful intubation on the first attempt and improves physiological stability of the infant. Using nHF during neonatal endotracheal intubation is a simple, easily applicable technique which may improve neonatal care and aid acquisition of a critical procedural skill.
-
ItemCharacterising the impact of chemotherapy on the ovary( 2021)Cancer survivorship has risen, but in females, DNA-damaging treatments deplete the ovarian reserve of primordial follicles (PMFs), causing infertility and ovarian endocrine failure. It has previously been shown in mice that elimination of the pro-apoptotic BH3-only protein, PUMA, protects oocytes from gamma-irradiation-induced apoptosis. However, the role of such pathways following chemotherapy has not previously been studied and the underlying mechanisms of chemotherapy-induced PMF loss have been unclear, hampering efforts to develop effective pharmacologic ovarian protection agents. This thesis had three main aims: 1. To determine whether PUMA elimination prevents loss of primordial follicles following gonadotoxic chemotherapy; 2. To identify the underlying mechanisms of PMF loss following cisplatin and cyclophosphamide, including their intraovarian cellular targets and the time course over which depletion occurs; 3. To investigate the DNA repair capacity of PMFs following cisplatin- and cyclophosphamide-induced damage and identify repair pathways used. To address these aims, three original studies were devised, using mouse models. In Chapter 2, unbiased stereology was used to quantify the effect of cyclophosphamide and cisplatin on PMF numbers in wild type (WT), TAp63-/-, and Puma-/- female mice. In WTs, cyclophosphamide depleted the ovarian reserve by 96% and cisplatin by 78%. In striking contrast, Puma-/- females in all treatment groups retained all their PMFs, as did TAp63-/- mice treated with cisplatin. Interestingly, cyclophosphamide-treated TAp63-/- females were only partially protected, indicating mechanistic differences in Puma induction pathways. Fertility trials showed that both drugs reduced fertility in WTs. In contrast, all fertility parameters were completely preserved in both TAp63-/- and Puma-/- groups, regardless of treatment; offspring appeared healthy. Together, these data demonstrate that PUMA is the critical trigger of apoptosis in PMFs following these chemotherapies and that its elimination protects the ovarian reserve and preserves fertility. Chapter 3 investigated the underlying mechanisms of PMF depletion following cisplatin or cyclophosphamide treatment. Immunofluorescence for phospho-histone family, member X (gamma-H2AX) showed that oocytes within primordial, transitional, and primary follicles sustain DNA double strand breaks (DSBs), but in secondary and antral follicles, granulosa cells are damaged; apoptosis was detected in the corresponding cell types using TUNEL. Given that most oocytes in reproductively young mice are stored within PMFs, this demonstrates that direct PMF oocyte damage is the primary mechanism of ovarian reserve depletion in this setting. Therefore, pharmacological strategies for ovarian protection during cancer treatment must specifically prevent PMF oocyte apoptosis. Chapter 4 investigated DNA repair pathways employed by PMFs after cisplatin or cyclophosphamide treatment. Immunofluorescence for RAD51, an essential protein in the high-fidelity, homologous recombination (HR) pathway, indicated that PMF oocytes initiate HR within 8 hours of treatment with cisplatin or cyclophosphamide, coinciding with high levels of DSBs as shown by gamma-H2AX. Immunofluorescence for DNA-PKcs, part of the lower fidelity, non-homologous end joining (NHEJ) pathway, showed that NHEJ is seldom utilised in PMF oocytes following these chemotherapies. Collectively, these studies represent a body of work which enhances our mechanistic understanding of chemotherapy-induced ovarian damage, explains how common cancer treatments cause female infertility, and identifies targets for future pharmacological strategies to preserve ovarian function in female cancer patients.
- 1 (current)
- 2
- 3
- 4
- 5