| There are one million immature oocytes at prophase of meiosis in ovary when women were bom. After adolescence, a number of them start to mature and ovulate under the effect of gonadotrophin. A health fertile woman will only ovalate approximately 400 of these unique cells. Oocyte resting in the ovary will die by atresia. Harvesting oocytes atresia and maturing them in vitro will help us to collect the massage of folliculogenesis and oocytes in vitro maturation (IVM), to provide oocytes for infertile women, to reduce in cost that need to purchace meducation for ovarian stimulation in IVF-ET and avoid the side effects associated with the use of gonadotrophin such as ovarian hyperstimualtion syndrome, weight gain, abdominal bloating and the long-term risk of it. At the same time, IVM can simptificate of treatment. Although, oocyte can mature, fertilization in vitro and pregenancy can succeed after embryo transfer, the rates of maturation, fertilize and pregenancy are very low. The compositon in culture medium can effect and even change the regulation of oocyte meiosis in mammal. Since 1990's, many scientists improve maturation of immature oocyte by adding different substances to culture medium. Today, the composition of culture system in vitro is different, there is no unified standard. To find the optimum culture medium system, improve the quality and maturation of oocyte is very籋 A 1*2004 MMimportant.Following the development of IVF-ET, cryopreservation has an inestimable effects. Cryopreservation of oocyte can avoid some of the law, ethical, moral and religion problems encountered by embryo crypreservation. It can provide the best hope of preserving the eugenesis for these young women at risk of losing their ovarian function because of disesses. Immature oocyte cryopreservation combining with oocyte maturation in vitro will built an egg banking, which can provide eggs to women who have little eggs, no eggs and decline of ovarian function, provide enough eggs to research and promote the development of biology, genetics and histology. Whittingham achieved the first success of mouse oocyte cryopreservation in 1997. The first human live fetal at 26 weeks from frozen was reported by Chen in 1986. Since then, many researchers studied the oocyte cryopreservation, but the improvement of it was very slow. Today, the success of oocyte cryopreservation is very low. There is no unified standard about cryopreservation methods. Every step of freezing-thawing can effect the nomal structure and function of oocyte, causing the low survival rate, fertilization rate and poor embryo development competence. There are many factors that effect oocyte cryopreservatin. One is the stage of oocyte, the other is the methods of cryopreservation . Mature oocyte is in metaphage II stage of the meiotic division, it shows the first body extruded and the chromosomes arrange on the meiotic spindle. It is well know that appropriate organization of spindle microtubules is essential for correct alignment and segregation of chromosomes. During the freezing and thawing, spindle is more easy to be injured by intracellular ice formation, leading to chromosomal abnormity and failure of fertilization and even development. Oocyte at germinal vesicle(GV) stage is in diplotene stage of the meiotic division. The spindle has not been formed and chromosomal abnormality is very low at this stage. It is likely that cryopreservation of GV stage oocyte is a better section than MII stage oocyte. Recently, a!few fetuses from mature and immature oocyte cryopreservation by different methods have born in overseas. It is very important to explore the factors which effect oocyte cryopreservation and find the optimal stage and method.We used mouse as the objects, studied the effects of epidermal growth factor(EGF),17beta-estradiol(17p-E2), pyruvic acid and cumulus cells on developmentcompetence of in vitro maturation mouse oocyte. The purpose was to optimize the culture system of IVM and provide the new theoretics of improving the maturation, fertilization and...
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