Strategies to improve in vitro maturation of human and mouse oocytes

Our knowledge of reproductive medicine has expanded rapidly since the birth of Louise Brown, the first baby to be conceived by in vitro fertilization (IVF) in 1978. In vitro maturation (IVM) of oocytes - a culture technique to support maturation of immature oocytes in vitro - could offer an interesting adjunct to the classical assisted reproductive treatments. From a clinical point of view, it could diminish or avoid the use of superovulation drugs, thus reducing treatment length, costs and the risk of severe ovarian hyperstimulation syndrome (OHSS) and other adverse side-effects associated with hormonal stimulation. Other potential benefits include the provision of a source of oocytes for research in the fields of stem cells and cloning, obtaining oocytes for donation and preservation of fertility. However, several aspects of the technique are still in the process of optimization. A crucial point in this context is the development of new culture strategies for IVM, which is the objective of the present thesis. Immature human and mouse oocytes were used as models to reach this goal. One of the major problems in IVM is the fact that isolated meiotic-competent oocytes undergo nuclear maturation spontaneously before the cytoplasm achieves full maturity. A possible way to circumvent this deficiency is to apply a 2-step culture composed of (1) a prematuration culture (PMC) to block temporarily spontaneous nuclear maturation, followed by (2) conventional IVM. By inducing meiotic arrest during PMC, oocytes may have the time to undergo cytoplasmic changes (mRNA storage, protein accumulation, ultrastructural remodelling), needed to enhance the oocytes’ capacity to sustain further embryonic development. Oocyte-specific phosphodiesterase type 3-inhibitors (PDE3-Is) are potent meiotic inhibitors of the PMC-step. Mouse cumulus-oocytes complexes (COCs) were utilized to optimize the 2-step culture. In addition, a similar 2-step culture was applied on human oocytes. Furthermore, we performed the PMC step in a three-dimensional (3D) co-culture system of human oocytes with dissociated cumulus cells, making use of an extra-cellular matrix (ECM; collagen). The results from the above studies might offer significant applications for improving the clinical outcome of IVM technologies.

ISBN:9789038214207

Jaar van publicatie:2009

Toegankelijkheid:Open