Abstract
Abstract Meiotic maturation occurs spontaneously when bovine oocytes are removed from their follicles and cultured in vitro. This natural phenomenon in mammals has greatly facilitated the use of in vitro matured oocytes for fertilization and embryo production. Bovine oocytes from small antral (immature) follicles can be matured in vitro up to the stage where they can be fertilized but their average subsequent developmental capacity is limited. Regardless of progress made to improve culture conditions during oocyte maturation and embryo development during the last few years, only one third of the oocytes selected on morphological criteria result in viable embryos, while the other two thirds, cultured in the same conditions, do not. This indicates some deficiency in these oocytes. It is clear that normal cytoplasmic maturation must occur in vitro to produce a good embryo but is the cytoplasm of all oocytes ready to respond to our maturation conditions? If we suppose that a maturing follicle influences the oocyte's ability to support further development, it is essential to understand this process and simulate this effect in vitro. The first step towards this objective requires a culture system that reproduces the ovarian follicular environment for the oocyte, in which nuclear maturation is prevented. In this study, we summarize the effect of each part of the follicle on meiotic resumption in bovine oocytes. Associations between mural granulosa cells and cumulus cells seem to be essential for prevention of nuclear maturation but the health of the follicle and the follicular fluid content are also important.
Published Version
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