| Acquisition of full developmental competence of oocytes not only occurs during growth stage, and the final preparation during oocyte maturation is also critical. Previous studies have shown that nuclear maturation can occur spontaneously following culture in vitro; however, there may be some insufficiency in cytoplasmic maturation of the in vitro matured oocytes. But till now, the differences of the events of cytoplasmic maturation between in vitro and in vivo matured oocytes are still not clear. Ovarian stimulation by gonadotrophins is used to permits the growth and development of follicles, to time the initiation of pre-ovulatory oocyte maturation, and to increase the numbers of oocytes ovulated. It is one of the foundations of current treatments of human infertility. The success of clinical IVF has been depending on generation of matured oocytes at high frequency. However, ovarian stimulation with gonadotropins is associated with side effects and complications.;In order to illuminate mechanisms which affect the developmental competence of oocytes produced in vitro, in the present study, we have compared the difference of the quality of oocytes produced in vitro with that of the oocytes produced in vivo using mouse model. In order to understand the relationship between oocyte competence and ovarian responses to stimulation in the mouse, we also have compared difference of the quality of oocytes produced in vitro or in vivo from gonadotrophns stimulated ovaries with that of from natural cycling ovaries.;In-vitro matured oocytes were collected from (1) naturally ovulated mice and (2) superovulated (PMSG + hCG) mice. Immature oocytes were retrieved from (3) naturally cycling mice, and (4) from mice primed with PMSG. The results indicate that the percentages of cleavage and blastocyst formation are significantly different (P<0.05) between in-vivo and in-vitro matured oocytes. Blastocyst formation rate is significantly higher (P<0.05) in immature oocytes derived from PMSG primed mice compared to immature oocytes derived from naturally cycling mice. The percentages of oocytes with comet tails and the length of comet tails are significantly higher and longer respectively in in-vitro matured oocytes compared to in-vivo matured oocytes. Total cell numbers of blastocyst are also significantly different (P<0.05) between in-vivo and in-vitro matured oocytes. However, there are no differences in ratio of trophectoderm (TE)/inner cell mass (ICM) between in-vivo and in-vitro matured oocytes. In conclusion, in-vivo matured mouse oocytes are more competent than those of matured in-vitro, suggesting that it may be due to its less damage of DNA. Embryonic development capacity of in-vivo matured oocytes is not promoted by ovarian stimulation. Gonadotropin priming prior to immature mouse oocyte retrieval is beneficial to subsequent embryonic development.;Keywords. mouse oocyte, IVM, IVF, gonadotropin, development... |
