The competence of oocytes to mature and undergo fertilization and embryonic development is known to be influenced by the conditions under which their maturation occurs. Suboptimal maturation in vitro currently limits the use of immature oocytes for embryo creation. This project examines the relationship between the conditions of in vitro maturation of human oocytes and aspects of their subsequent developmental competence through the in vitro creation and analysis of research embryos. This work is essential in defining effective and safe conditions for the use of human immature oocytes in programmes of clinical treatment to alleviate infertility. Human immature oocytes were exposed in vitro to various concentrations of meiosis activating sterol (FF-MAS), an endogenous mediator of follicle and oocyte function, or epidermal growth factor (EOP), in the absence of other hormonal support. Their survival and further development relative to controls were measured by assessing the proportions maturing, fertilizing by sperm injection (ICSI), and cleaving in vitro. Image analysis was used to measure various dimensions of oocytes and embryos daily. A pilot study of chromosome and spindle configurations at meiotic metaphase was also conducted. The major findings of this project are that FF-MAS supplementation of maturation medium has different positive effects upon immature oocytes arising from patient groups having different endocrine profiles and yielding differing oocyte populations. FF-MAS at 30J.lg/ml promotes survival of oocytes from unstimulated patients with polycystic ovaries (p<O.02S) and promotes maturation of oocytes from gonadotrophin-stimulated patients undergoing ICSI treatment (p<O.OS). A response to FF-MAS in terms of oocyte growth was evident in immature oocytes from both types of patients (p<O.05). Mature, immature and atretic oocytes from patients with pca became significantly different in terms of oocyte diameter when cultured in FF-MAS (10 or 30J.lg/ml), contrasting with those cultured in control conditions, or obtained from patients undergoing ICSI treatment. However, significant (p<O.OS) enlargement of oocyte diameter between oocyte recovery and the day of insemination occurred when oocytes from patients undergoing ICSI were cultured with FF-MAS. The proportion of mature oocytes fertilized by ICSI was not affected by FF-MAS in the maturation culture but there was a non-significant tendency towards an improved chance of cleavage when FF-MAS was present. Embryonic development beyond early cleavage was not observed, despite conditions supportive of blastocyst production from in vivo matured oocytes, suggesting that developmental competence remained compromised even in the presence of FF-MAS. A pilot study to ascertain whether the incidence of spindle defects or chromosome irregularities in in vitro matured metaphase oocytes was influenced by the presence of FF-MAS gave equivocal results. This project has confirmed that the ongoing development of in vitro matured oocytes may be affected by the conditions of their maturation. Specifically it has demonstrated for the first time the positive effects of FF-MAS upon human immature oocyte development in vitro, and provided the first quantitative non-invasive analysis of oocyte growth during maturation under various conditions in vitro.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:269542 |
| Date | January 2002 |
| Creators | Cavilla, Jennifer Louise |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/73509/ |
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