In vitro fertilization
In vitro fertilization (IVF) can be achieved in various laboratory animals by co-culturing oocytes and sperm. First, superovulation of female animals are induced by hormonal injections. Then, collected oocytes are fertilized by culturing them with sperm in vitro under appropriate conditions. IVF-derived offspring are usually obtained by transferring embryos into genital tracts (oviducts or uteri) of pregnant or pseudopregnant females after culturing embryos to make them develop into later developmental stages.
IVF is a quite useful technique not only to obtain offsprings of endangered animals, sterile animals or animals with low reproductive performance, but also to study fertilization mechanisms. Embryo and sperm freezing technologies are also important for maintenance of various animals, e.g., laboratory animals. In case of laboratory animals, mice is a species that IVF is most frequently applied to. IVF is especially useful when many embryos are needed at a given time. As we reported in vitro fertilization rates of 55 strains of mice (Ref. 1), there are still some strains which show low fertilization rates and/or low developmental rates in vitro.
Although literature of successful offspring production from in vitro fertilized embryos has been reported in rabbits(1959) and rats(1974), it is still difficult to obtain IVF-derived offspring with high reproducibility in animals other than mice, rats and rabbits. We reported successful IVF in the mastomys (Ref. 2) and the Mongolian gerbil (Ref. 3), but we have not yet obtained offspring from IVF embryos. No papers are published so far on successful IVF-derived offspring production in the guinea pig. It is still difficult to reproduce the results of successful offspring production in Syrian hamsters reported by other laboratory (1991).
Thus, we have to seek improvment for IVF and related techiques to make them more efficient and stable. Along the search for the improvement, we would obtain broader insights for secrets of the animal development.
References
- Development in vitro of preimplantation embryos from 55 mouse strains., Suzuki O., Asano T., Yamamoto Y., Takano K. and Koura M., Reproduction, Fertility and Development, 8, 975-980 (1996).
- Partial characterization of the gametes and development of a successful in vitro fertilization procedure in the Mastomys ( Praomys coucha ): A new species for reproductive biology research., Nohara M., Hirayama T., Ogura A., Hiroi M and Araki Y., Biology of Reproduction, 58, 226-233 (1998).
- In vitro fertilization and intracytoplasmic sperm injection in the Mongolian gerbil., Mochida K., Matsuda J., Ponce R. H., Nakahira M., Takano K., Yamamoto Y., Noguchi Y. and Ogura A., 14th International Congress on Animal Reproduction, Abstracts vol.2, 204 (2000)