Comparison of preimplantation developmental competence after mouse oocyte growth and development in vitro and in vivo.

Culture systems for oocytes are essential for the experimental analysis of the basic mechanisms of oocyte development and, moreover, they will eventually find wide application in agriculture, the clinic, and wildlife preservation. Here, progress in mouse oocyte growth and development in vitro using oocyte-granulosa cell complexes from preantral follicles is reviewed. Oocyte-granulosa cell complexes were isolated from preantral (secondary) follicles of 12 day old mice, grown in vitro for 10 days, then matured and fertilized in vitro. The developmental competence of these oocytes was compared with oocytes grown in vivo and isolated from 22 day old mice, then matured and fertilized in vitro. In vitro-grown oocytes did not achieve the same size as their in vivo-grown counterparts. However, when oocytes were grown in medium containing fetal bovine serum, their preimplantation developmental competence was equivalent to that of in vivo-grown oocytes. Surprisingly, more blastocysts per animal were produced when oocytes were grown in vitro than in vivo. There was no correlation between oocyte size and either preimplantation developmental competence or number of cells per blastocyst. Oocytes grown in serum-free medium did not achieve the same developmental competence as oocytes grown in medium supplemented with serum. Lastly, the health status as an adult of the only animal born after complete oocyte development in vitro is described and discussed.