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Ooplasmic influence on nuclear function during the metaphase II-interphase transition in mouse oocytes.
1Program for In Vitro Fertilization, Reproductive Surgery and Infertility, New York University School of Medicine, New York, New York 10016, USA.
Biology of Reproduction
|November 22, 2001
Summary
In vitro maturation of mouse oocytes hinders embryonic development, but their nuclei can support development within a proper ooplasmic environment. In vivo maturation is crucial for establishing this environment, leading to successful live births.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Cell Biology
Background:
- Oocyte maturation is critical for successful fertilization and embryonic development.
- The ooplasmic environment plays a vital role in supporting nuclear function post-activation.
- In vitro maturation (IVM) protocols may not fully replicate the in vivo conditions necessary for oocyte competence.
Purpose of the Study:
- To assess the functional competence of the nucleus and cytoplasm of mouse oocytes matured in vitro versus in vivo.
- To determine the impact of the ooplasmic milieu during artificial activation on subsequent embryonic development.
- To investigate the developmental potential of reconstructed zygotes using pronuclei from oocytes matured under different conditions.
Main Methods:
- Nuclear and pronuclear transfer techniques were employed in mouse oocytes.
- Oocytes were matured in vitro (IVM) or in vivo, denuded of granulosa cells, and artificially activated.
- Reconstructed zygotes were cultured and transferred to foster mothers to assess live birth rates.
Main Results:
- Live birth rates were significantly lower (0-1%) for oocytes matured and activated in vitro compared to in vivo matured oocytes (17-21%).
- Reconstructed zygotes using pronuclei from in vivo-matured oocytes or hybrid oocytes showed higher live birth rates (21-23%).
- Ooplasm from both in vitro and in vivo matured oocytes supported development equally well after activation and pronuclear formation were completed.
Conclusions:
- The nucleus of an in vitro-matured oocyte can support embryonic development, but requires the correct ooplasmic environment present during in vivo maturation.
- The cellular factors constituting the ooplasmic milieu develop adequately in vivo but are compromised in denuded oocytes matured in vitro.
- The ooplasmic milieu at the time of chemical activation is critical for successful embryonic development, irrespective of the maturation environment once activation is complete.