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Title: Molecular and metabolic measures of oocyte developmental competence in vivo and in vitro
Author: Fernandez, Esther Collado
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2013
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Assisted reproduction technologies remain inefficient, owing largely to poor oocyte quality. It is hypothesised that a more detailed understanding of the factors that influence the oocyte's metabolome and transcriptome in vivo and in vitro will lead to improvements in the diagnosis and treatment of female infertility. The objectives of this thesis were to (i) evaluate the impact of the follicular environment in natural cycles and following controlled ovarian stimulation (COS) on oocyte competence (i.e. quality) in vitro; (ii) identify cumulus cell markers of oocyte quality; and (iii) map the changes in oocyte carbohydrate metabolism and mitochondria] membrane potential (4Wm) during oogenesis. In vitro maturation (IVM) was conducted in 426 bovine oocytes from natural cycles and 102 oocytes were obtained from follicles after COS. Oocyte quality was quantified by meiotic progression to metaphase 11 (MII), by amino acid profiling (AAP) and by tracking the gamete's capacity to fertilise and develop into blastocyst. Oocytes from subordinate follicles, follicles ipsilateral to the corpus luteum, and follicles 5-9.5mm in diameter showed greater developmental potential. The consumption/production of serine, threonine, histidine and glutamine by bovine MII oocytes was predictive (68.9% accuracy) of the gametes capacity to support blastocyst development in vitro. A high ratio of inhibin 13a (INHBA) to follistatin (FST) mRNA expression in cumulus cells (CCs) also reflected the blastocyst potential of bovine oocytes. Analysis of the consumption/production of glucose, lactate and pyruvate by 292 ovine and 729 human follicles and 211 ovine and 275 human oocytes showed that energy metabolism by these cells relied on glucose and pyruvate oxidation, respectively, and this increased as development progressed. Oocyte mitochondria] i.'Pm remained stable through oogenesis. The results indicate that the follicle microenvironment profoundly influences oocyte metabolism and developmental potential in monovular species. Furthermore, follicular maturity, oocyte AAP and CC gene expression have been shown to be valuable markers of oocyte quality in vitro.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available